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Americans with Disabilities Act of 1990

The Americans with Disabilities Act of 1990 or ADA is a civil rights law that prohibits discrimination based on disability. It affords similar protections against discrimination to Americans with disabilities as the Civil Rights Act of 1964, which made discrimination based on race, religion, sex, national origin, and other characteristics illegal, and later sexual orientation and gender identity. In addition, unlike the Civil Rights Act, the ADA also requires covered employers to provide reasonable accommodations to employees with disabilities, and imposes accessibility requirements on public accommodations.

In 1986, the National Council on Disability had recommended the enactment of an Americans with Disabilities Act and drafted the first version of the bill which was introduced in the House and Senate in 1988. A broad bipartisan coalition of legislators supported the ADA, while the bill was opposed by business interests (who argued the bill imposed costs on business) and conservative evangelicals (who opposed protection for individuals with HIV). The final version of the bill was signed into law on July 26, 1990, by President George H. W. Bush. It was later amended in 2008 and signed by President George W. Bush with changes effective as of January 1, 2009.

Disabilities included

ADA disabilities include both mental and physical medical conditions. A condition does not need to be severe or permanent to be a disability. Equal Employment Opportunity Commission regulations provide a list of conditions that should easily be concluded to be disabilities: amputation, attention deficit hyperactivity disorder (ADHD), autism, bipolar disorder, blindness, cancer, cerebral palsy, deafness, diabetes, epilepsy, HIV/AIDS, intellectual disability, major depressive disorder, mobility impairments requiring a wheelchair, multiple sclerosis, muscular dystrophy, obsessive–compulsive disorder (OCD), post-traumatic stress disorder (PTSD), and schizophrenia. Other mental or physical health conditions also may be disabilities, depending on what the individual's symptoms would be in the absence of "mitigating measures" (medication, therapy, assistive devices, or other means of restoring function), during an "active episode" of the condition (if the condition is episodic).

Certain specific conditions that are widely considered anti-social, or tend to result in illegal activity, such as kleptomania, pedophilia, exhibitionism, voyeurism, etc. are excluded under the definition of "disability" in order to prevent abuse of the statute's purpose. Additionally, sexual orientation is no longer considered a disorder and is also excluded under the definition of "disability". However, in 2022, the United States Court of Appeals for the Fourth Circuit stated that the ADA covers individuals with gender dysphoria, which may aid transgender people in accessing legal protections they otherwise may be unable to.

Title I—employment

 * See also US labor law and .

The ADA states that a "covered entity" shall not discriminate against "a qualified individual with a disability". This applies to job application procedures, hiring, advancement and discharge of employees, job training, and other terms, conditions, and privileges of employment. "Covered entities" include employers with 15 or more employees, as well as employment agencies, labor organizations, and joint labor-management committees. There are strict limitations on when a covered entity can ask job applicants or employees disability-related questions or require them to undergo medical examination, and all medical information must be kept confidential.

Prohibited discrimination may include, among other things, firing or refusing to hire someone based on a real or perceived disability, segregation, and harassment based on a disability. Covered entities are also required to provide reasonable accommodations to job applicants and employees with disabilities. A reasonable accommodation is a change in the way things are typically done that the person needs because of a disability, and can include, among other things, special equipment that allows the person to perform the job, scheduling changes, and changes to the way work assignments are chosen or communicated. An employer is not required to provide an accommodation that would involve undue hardship (excessive difficulty or expense), and the individual who receives the accommodation must still perform the essential functions of the job and meet the normal performance requirements. An employee or applicant who currently engages in the illegal use of drugs is not considered qualified when a covered entity takes adverse action based on such use.

Part of Title I was found unconstitutional by the United States Supreme Court as it pertains to states in the case of Board of Trustees of the University of Alabama v. Garrett as violating the sovereign immunity rights of the several states as specified by the Eleventh Amendment to the United States Constitution. The Court determined that state employees cannot sue their employer for violating ADA rules. State employees can, however, file complaints at the Department of Justice or the Equal Employment Opportunity Commission, who can sue on their behalf.

Title II—public entities (and public transportation)
Title II prohibits disability discrimination by all public entities at the local level, e.g., school district, municipal, city, or county, and at state level. Public entities must comply with Title II regulations by the U.S. Department of Justice. These regulations cover access to all programs and services offered by the entity. Access includes physical access described in the ADA Standards for Accessible Design and programmatic access that might be obstructed by discriminatory policies or procedures of the entity.

Title II applies to public transportation provided by public entities through regulations by the U.S. Department of Transportation. It includes the National Railroad Passenger Corporation (Amtrak), along with all other commuter authorities. This section requires the provision of paratransit services by public entities that provide fixed-route services. ADA also sets minimum requirements for space layout in order to facilitate wheelchair securement on public transport.

Title II also applies to all state and local public housing, housing assistance, and housing referrals. The Office of Fair Housing and Equal Opportunity is charged with enforcing this provision.

Title III—public accommodations (and commercial facilities)

Under Title III, no individual may be discriminated against on the basis of disability with regards to the full and equal enjoyment of the goods, services, facilities, or accommodations of any place of public accommodation by any person who owns, leases, or operates a place of public accommodation. Public accommodations include most places of lodging (such as inns and hotels), recreation, transportation, education, and dining, along with stores, care providers, and places of public displays.

Under Title III of the ADA, all new construction (construction, modification or alterations) after the effective date of the ADA (approximately July 1992) must be fully compliant with the Americans With Disabilities Act Accessibility Guidelines (ADAAG) found in the Code of Federal Regulations at 28 C.F.R., Part 36, Appendix A.

Title III also has applications to existing facilities. One of the definitions of "discrimination" under Title III of the ADA is a "failure to remove" architectural barriers in existing facilities. See. This means that even facilities that have not been modified or altered in any way after the ADA was passed still have obligations. The standard is whether "removing barriers" (typically defined as bringing a condition into compliance with the ADAAG) is "readily achievable", defined as "...easily accomplished without much difficulty or expense".

The statutory definition of "readily achievable" calls for a balancing test between the cost of the proposed alteration and the wherewithal of the business and/or owners of the business. Thus, what might be "readily achievable" for a sophisticated and financially capable corporation might not be readily achievable for a small or local business.

There are exceptions to this title; many private clubs and religious organizations may not be bound by Title III. With regard to historic properties (those properties that are listed or that are eligible for listing in the National Register of Historic Places, or properties designated as historic under state or local law), those facilities must still comply with the provisions of Title III of the ADA to the "maximum extent feasible" but if following the usual standards would "threaten to destroy the historic significance of a feature of the building" then alternative standards may be used.

Under 2010 revisions of Department of Justice regulations, newly constructed or altered swimming pools, wading pools, and spas must have an accessible means of entrance and exit to pools for disabled people. However, the requirement is conditioned on whether providing access through a fixed lift is "readily achievable". Other requirements exist, based on pool size, include providing a certain number of accessible means of entry and exit, which are outlined in Section 242 of the standards. However, businesses are free to consider the differences in the application of the rules depending on whether the pool is new or altered, or whether the swimming pool was in existence before the effective date of the new rule. Full compliance may not be required for existing facilities; Section 242 and 1009 of the 2010 Standards outline such exceptions.

Service animals
The ADA provides explicit coverage for service animals. Guidelines have been developed not only to protect persons with disabilities but also to indemnify businesses from damages related to granting access to service animals on their premises. Businesses are allowed to ask if the animal is a service animal and ask what tasks it is trained to perform, but they are not allowed to ask the service animal to perform the task nor ask for a special ID of the animal. They cannot ask what the person's disabilities are. A person with a disability cannot be removed from the premises unless either of two things happen: the animal is out of control and its owner cannot get it under control (e.g. a dog barking uncontrollably in a restaurant), or the animal is a direct threat to people's health and safety. Allergies and fear of animals would not be considered a threat to people's health and safety, so it would not be a valid reason to deny access to people with service animals. Businesses that prepare or serve food must allow service animals and their owners on the premises even if state or local health laws otherwise prohibit animals on the premises. In this case, businesses that prepare or serve food are not required to provide care or food for service animals, nor do they have to provide a designated area for the service animal to relieve itself. Lastly, people that require service dogs cannot be charged an extra fee for their service dog or be treated unfairly, for example, being isolated from people at a restaurant. People with disabilities cannot be treated as "less than" other customers. However, if a business normally charges for damages caused by the person to property, the customer with a disability will be charged for their service animal's damages to the property.

Auxiliary aids
The ADA provides explicit coverage for auxiliary aids.

Auxiliary aids and services are items, equipment or services that assist in effective communication between a person who has a hearing, vision or speech disability and a person who does not.

ADA says that a public accommodation shall take those steps that may be necessary to ensure that no individual with a disability is excluded, denied services, segregated or otherwise treated differently than other individuals because of the absence of auxiliary aids and services, unless the public accommodation can demonstrate that taking those steps would fundamentally alter the nature of the goods, services, facilities, privileges, advantages, or accommodations being offered or would result in an undue burden, i.e., significant difficulty or expense. The term "auxiliary aids and services" includes:

 * 1) Qualified interpreters on-site or through video remote interpreting (VRI) services; notetakers; real-time computer-aided transcription services; written materials; exchange of written notes; telephone handset amplifiers; assistive listening devices; assistive listening systems; telephones compatible with hearing aids; closed caption decoders; open and closed captioning, including real-time captioning; voice, text, and video-based telecommunications products and systems, including text telephones (TTYs), videophones, and captioned telephones, or equally effective telecommunications devices; videotext displays; accessible electronic and information technology; or other effective methods of making aurally delivered information available to individuals who are deaf or hard of hearing;
 * 2) Qualified readers; taped texts; audio recordings; Brailled materials and displays; screen reader software; magnification software; optical readers; secondary auditory programs (SAP); large print materials; accessible electronic and information technology; or other effective methods of making visually delivered materials available to individuals who are blind or have low vision;
 * 3) Acquisition or modification of equipment or devices; and
 * 4) Other similar services and actions.

Captions are considered one type of auxiliary aid. Since the passage of the ADA, the use of captioning has expanded. Entertainment, educational, informational, and training materials are captioned for deaf and hard-of-hearing audiences at the time they are produced and distributed. The Television Decoder Circuitry Act of 1990 requires that all televisions larger than 13 inches sold in the United States after July 1993 have a special built-in decoder that enables viewers to watch closed-captioned programming. The Telecommunications Act of 1996 directs the Federal Communications Commission (FCC) to adopt rules requiring closed captioning of most television programming. The FCC's rules on closed captioning became effective January 1, 1998.

Title IV—telecommunications
Title IV of the ADA amended the landmark Communications Act of 1934 primarily by adding section. This section requires that all telecommunications companies in the U.S. take steps to ensure functionally equivalent services for consumers with disabilities, notably those who are deaf or hard of hearing and those with speech impairments. When Title IV took effect in the early 1990s, it led to the installation of public teletypewriter (TTY) machines and other TDD (telecommunications devices for the deaf). Title IV also led to the creation, in all 50 states and the District of Columbia, of what was then called dual-party relay services and now are known as Telecommunications Relay Services (TRS), such as STS relay. Today, many TRS-mediated calls are made over the Internet by consumers who use broadband connections. Some are Video Relay Service (VRS) calls, while others are text calls. In either variation, communication assistants translate between the signed or typed words of a consumer and the spoken words of others. In 2006, according to the Federal Communications Commission (FCC), VRS calls averaged two million minutes a month.

Title V—miscellaneous provisions
Title V includes technical provisions. It discusses, for example, the fact that nothing in the ADA amends, overrides or cancels anything in Section 504. Additionally, Title V includes an anti-retaliation or coercion provision. The Technical Assistance Manual for the ADA explains this provision:

"III-3.6000 Retaliation or coercion. Individuals who exercise their rights under the ADA, or assist others in exercising their rights, are protected from retaliation. The prohibition against retaliation or coercion applies broadly to any individual or entity that seeks to prevent an individual from exercising his or her rights or to retaliate against him or her for having exercised those rights ... Any form of retaliation or coercion, including threats, intimidation, or interference, is prohibited if it is intended to interfere."

History
The ADA has roots in Section 504 of the Rehabilitation Act of 1973.

Drafting
The law began in the Virginia House of Delegates in 1985 as the Virginians with Disabilities Act—supported by Warren G. Stambaugh—which was passed by the state Virginia. It is the first iteration of the Americans with Disabilities Act.

In 1986, the National Council on Disability (NCD), an independent federal agency, issued a report, Towards Independence, in which the Council examined incentives and disincentives in federal laws towards increasing the independence and full integration of people with disabilities into U.S. society. Among the disincentives to independence the Council identified was the existence of large remaining gaps in civil rights coverage for people with disabilities in the United States. A principal conclusion of the report was to recommend the adoption of comprehensive civil rights legislation, which became the ADA.

The idea of federal legislation enhancing and extending civil rights legislation to millions of Americans with disabilities gained bipartisan support in late 1988 and early 1989. In early 1989 both Congress and the newly inaugurated Bush White House worked separately, then jointly, to write legislation capable of expanding civil rights without imposing undue harm or costs on those already in compliance with existing rules and laws.

Lobbying
Over the years, key activists and advocates played an important role in lobbying members of the U.S. Congress to develop and pass the ADA, including Justin Whitlock Dart Jr., Patrisha Wright and others.

Wright is known as "the General" for her work in coordinating the campaign to enact the ADA. She is widely considered the main force behind the campaign lobbying for the ADA.

Support
Senator Bob Dole was a supporter and advocate for the bill.

Opposition from religious groups
Conservative evangelicals opposed the ADA because the legislation protected individuals with HIV, which they associated with homosexuality.

The debate over the Americans with Disabilities Act led some religious groups to take opposite positions. The Association of Christian Schools International opposed the ADA in its original form, primarily because the ADA labeled religious institutions "public accommodations" and thus would have required churches to make costly structural changes to ensure access for all. The cost argument advanced by ACSI and others prevailed in keeping religious institutions from being labeled as "public accommodations". Church groups such as the National Association of Evangelicals testified against the ADA's Title I employment provisions on grounds of religious liberty. The NAE believed the regulation of the internal employment of churches was "... an improper intrusion [of] the federal government."

Opposition from business interests
Many companies, corporations, and business groups opposed the Americans with Disabilities Act, arguing that the legislation would impose costs on businesses. Testifying before Congress, Greyhound Bus Lines stated that the act had the potential to "deprive millions of people of affordable intercity public transportation and thousands of rural communities of their only link to the outside world." The US Chamber of Commerce argued that the costs of the ADA would be "enormous" and have "a disastrous impact on many small businesses struggling to survive." The National Federation of Independent Business, an organization that lobbies for small businesses, called the ADA "a disaster for small business". Pro-business conservative commentators joined in opposition, writing that the Americans with Disabilities Act was "an expensive headache to millions" that would not necessarily improve the lives of people with disabilities.

"Capitol Crawl"
Shortly before the act was passed, disability rights activists with physical disabilities coalesced in front of the Capitol Building, shed their crutches, wheelchairs, powerchairs and other assistive devices, and immediately proceeded to crawl and pull their bodies up all 100 of the Capitol's front steps, without warning. As the activists did so, many of them chanted "ADA now", and "Vote, Now". Some activists who remained at the bottom of the steps held signs and yelled words of encouragement at the "Capitol Crawlers". Jennifer Keelan, a second grader with cerebral palsy, was videotaped as she pulled herself up the steps, using mostly her hands and arms, saying "I'll take all night if I have to." This direct action is reported to have "inconvenienced" several senators and to have pushed them to approve the act. While there are those who do not attribute much overall importance to this action, the "Capitol Crawl" of 1990 is seen by some present-day disability activists in the United States as a central act for encouraging the ADA into law.

Final passage

Senator Tom Harkin (D-IA) authored what became the final bill and was its chief sponsor in the Senate. Harkin delivered part of his introduction speech in sign language, saying it was so his deaf brother could understand.

President George H. W. Bush, on signing the measure on July 26, 1990, said:

"I know there may have been concerns that the ADA may be too vague or too costly, or may lead endlessly to litigation. But I want to reassure you right now that my administration and the United States Congress have carefully crafted this Act. We've all been determined to ensure that it gives flexibility, particularly in terms of the timetable of implementation; and we've been committed to containing the costs that may be incurred.... Let the shameful wall of exclusion finally come tumbling down."

ADA Amendments Act, 2008
The ADA defines a covered disability as a physical or mental impairment that substantially limits one or more major life activities, a history of having such an impairment, or being regarded as having such an impairment. The Equal Employment Opportunity Commission (EEOC) was charged with interpreting the 1990 law with regard to discrimination in employment. The EEOC developed regulations limiting an individual's impairment to one that "severely or significantly restricts" a major life activity. The ADAAA directed the EEOC to amend its regulations and replace "severely or significantly" with "substantially limits", a more lenient standard.

On September 25, 2008, President George W. Bush signed the ADA Amendments Act of 2008 (ADAAA) into law. The amendment broadened the definition of "disability", thereby extending the ADA's protections to a greater number of people. The ADAAA also added to the ADA examples of "major life activities" including, but not limited to, "caring for oneself, performing manual tasks, seeing, hearing, eating, sleeping, walking, standing, lifting, bending, speaking, breathing, learning, reading, concentrating, thinking, communicating, and working" as well as the operation of several specified "major bodily functions". The act overturned a 1999 US Supreme Court case that held that an employee was not disabled if the impairment could be corrected by mitigating measures; it specifically provides that such impairment must be determined without considering such ameliorative measures. It also overturned the court's finding that an impairment that substantially limits one major life activity must also limit others to be considered a disability. In 2008, the United States House Committee on Education and Labor stated that the amendment "makes it absolutely clear that the ADA is intended to provide broad coverage to protect anyone who faces discrimination on the basis of disability." Thus the ADAAA led to broader coverage of impaired employees.

Web Content Accessibility Guidelines, 2019
In October 2019, the Supreme Court declined to resolve a circuit split as to whether websites are covered by the ADA. The Court turned down an appeal from Domino's Pizza and let stand a U.S. 9th Circuit Court of Appeals ruling which held that the Americans With Disabilities Act protects access not just to brick-and-mortar public accommodations, but also to the websites and apps of those businesses.

Impact
The ADA led to significant improvements in terms of access to public services, accessibility in the built environment, and societal understanding of disability.

Employment
Between 1991 (after the enactment of the ADA) and 1995, the employment rate of men with disabilities dropped by 7.8% regardless of age, educational level, or type of disability, with the most affected being young, less-educated and intellectually disabled men. While no causal link between the ADA and that trend has been definitively identified, some researchers have characterized the ADA as ineffectual and argued that it caused this decline by raising the cost of doing business for employers, who quietly avoid hiring people with disabilities for fear of lawsuit. To these employers, hiring people with disabilities became too expensive as they had to spend extra on assistive technology.

In 2001, for men of all working ages and women under 40, Current Population Survey data showed a sharp drop in the employment of disabled workers, leading at least two economists to attribute the cause to the Act. By contrast, a study in 2003 found that while the Act may have led to short term reactions by employers, in the long term, there were either positive or neutral consequences for wages and employment. In 2005, the rate of employment among disabled people increased to 45% of the population of disabled people.

"Professional plaintiffs"
Since enforcement of the act began in July 1992, it has quickly become a major component of employment law. The ADA allows private plaintiffs to receive only injunctive relief (a court order requiring the public accommodation to remedy violations of the accessibility regulations) and attorneys' fees, and does not provide monetary rewards to private plaintiffs who sue non-compliant businesses. Unless a state law, such as the California Unruh Civil Rights Act, provides for monetary damages to private plaintiffs, persons with disabilities do not obtain direct financial benefits from suing businesses that violate the ADA.

The attorneys' fees provision of Title III does provide incentive for lawyers to specialize and engage in serial ADA litigation, but a disabled plaintiff does not obtain a financial reward from attorneys' fees unless they act as their own attorney, or as mentioned above, a disabled plaintiff resides in a state that provides for minimum compensation and court fees in lawsuits. Moreover, there may be a benefit to these private attorneys general who identify and compel the correction of illegal conditions: they may increase the number of public accommodations accessible to persons with disabilities. "Civil rights law depends heavily on private enforcement. Moreover, the inclusion of penalties and damages is the driving force that facilitates voluntary compliance with the ADA." Courts have noted:

"As a result, most ADA suits are brought by a small number of private plaintiffs who view themselves as champions of the disabled. For the ADA to yield its promise of equal access for the disabled, it may indeed be necessary and desirable for committed individuals to bring serial litigation advancing the time when public accommodations will be compliant with the ADA."

However, in states that have enacted laws that allow private individuals to win monetary awards from non-compliant businesses (as of 2008, these include California, Florida, Hawaii, and Illinois), "professional plaintiffs" are typically found. At least one of these plaintiffs in California has been barred by courts from filing lawsuits unless he receives prior court permission. Through the end of fiscal year 1998, 86% of the 106,988 ADA charges filed with and resolved by the Equal Employment Opportunity Commission, were either dropped or investigated and dismissed by EEOC but not without imposing opportunity costs and legal fees on employers.

Case law
There have been some notable cases regarding the ADA. For example, a major hotel room marketer (Hotels.com) with their business presence on the Internet was sued because their customers with disabilities could not reserve hotel rooms through their website without substantial extra efforts that persons without disabilities were not required to perform. Such lawsuits represent a major potential expansion of the ADA in that they (known as "bricks vs. clicks"), seek to expand the ADA's authority to cyberspace, where entities may not have actual physical facilities that are required to comply.

Green v. State of California
Green v. State of California, No. S137770 (Cal. August 23, 2007) was a case in which the California Supreme Court was faced with deciding whether an employee suing the state is required to prove they are able to perform "essential" job duties, regardless of whether or not there was "reasonable accommodation", or if the employer must prove the person suing was unable to do so. The court ruled the burden was on the employee, not the employer, and reversed a disputed decision by the lower courts. Plaintiff attorney David Greenberg brought forth considerations of the concept that, even in the state of California, employers do not have to employ a worker who is unable to perform "essential job functions" with "reasonable accommodation". Forcing employers to do so "would defy logic and establish a poor public policy in employment matters."

National Federation of the Blind v. Target Corporation
National Federation of the Blind v. Target Corp. was a case where a major retailer, Target Corp., was sued because their web designers failed to design its website to enable persons with low or no vision to use it.

Board of Trustees of the University of Alabama v. Garrett
Board of Trustees of the University of Alabama v. Garrett was a United States Supreme Court case about Congress's enforcement powers under the Fourteenth Amendment to the Constitution. It decided that Title I of the Americans with Disabilities Act was unconstitutional insofar as it allowed private citizens to sue states for money damages.

Barden v. The City of Sacramento
Barden v. The City of Sacramento, filed in March 1999, claimed that the City of Sacramento failed to comply with the ADA when, while making public street improvements, it did not bring its sidewalks into compliance with the ADA. Certain issues were resolved in federal court. One issue, whether sidewalks were covered by the ADA, was appealed to the 9th Circuit Court of Appeals, which ruled that sidewalks were a "program" under the ADA and must be made accessible to persons with disabilities. The ruling was later appealed to the U.S. Supreme Court, which refused to hear the case, letting stand the ruling of the 9th Circuit.

Bates v. United Parcel Service, Inc
Bates v. United Parcel Service, Inc (UPS; begun in 1999) was the first equal opportunity employment class action brought on behalf of Deaf and Hard of Hearing workers throughout the country concerning workplace discrimination. It established legal precedent for these employees to be fully covered under the ADA. Key findings included: The outcome was that UPS agreed to pay a $5.8 million award and agreed to a comprehensive accommodations program that was implemented in their facilities throughout the country.
 * 1) UPS failed to address communication barriers and to ensure equal conditions and opportunities for deaf employees;
 * 2) Deaf employees were routinely excluded from workplace information, denied opportunities for promotion, and exposed to unsafe conditions due to lack of accommodations by UPS;
 * 3) UPS also lacked a system to alert these employees as to emergencies, such as fires or chemical spills, to ensure that they would safely evacuate their facility; and
 * 4) UPS had no policy to ensure that deaf applicants and employees actually received effective communication in the workplace.

Spector v. Norwegian Cruise Line Ltd.
Spector v. Norwegian Cruise Line Ltd. was a case that was decided by the United States Supreme Court in 2005. The defendant argued that as a vessel flying the flag of a foreign nation it was exempt from the requirements of the ADA. This argument was accepted by a federal court in Florida and, subsequently, the Fifth Circuit Court of Appeals. However, the U.S. Supreme Court reversed the ruling of the lower courts on the basis that Norwegian Cruise Lines was a business headquartered in the United States whose clients were predominantly Americans and, more importantly, operated out of port facilities throughout the United States.

Olmstead v. L.C.
Olmstead v. L.C. was a case before the United States Supreme Court in 1999. The two plaintiffs, Lois Curtis and E.W., were institutionalized in Georgia for diagnosed "mental retardation" and schizophrenia. Clinical assessments by the state determined that the plaintiffs could be appropriately treated in a community setting rather than the state institution. The plaintiffs sued the state of Georgia and the institution for being inappropriately treated and housed in the institutional setting rather than being treated in one of the state's community-based treatment facilities.

The Supreme Court decided under Title II of the ADA that mental illness is a form of disability and therefore covered under the ADA, and that unjustified institutional isolation of a person with a disability is a form of discrimination because it "...perpetuates unwarranted assumptions that persons so isolated are incapable or unworthy of participating in community life." The court added, "Confinement in an institution severely diminishes the everyday life activities of individuals, including family relations, social contacts, work options, economic independence, educational advancement, and cultural enrichment."

Therefore, under Title II no person with a disability can be unjustly excluded from participation in or be denied the benefits of services, programs or activities of any public entity.

Michigan Paralyzed Veterans of America v. The University of Michigan
Michigan Paralyzed Veterans of America v. The University of Michigan was a case filed before the United States District Court for the Eastern District of Michigan. It was filed on behalf of the Michigan Paralyzed Veterans of America against the University of Michigan claiming that Michigan Stadium violated the Americans with Disabilities Act in its $226-million renovation by failing to add enough seats for disabled fans or accommodate the needs for disabled restrooms, concessions and parking. Additionally, the distribution of the accessible seating was at issue, with nearly all the seats being provided in the end-zone areas. The U.S. Department of Justice assisted in the suit, which was settled in March 2008. The settlement required the stadium to add 329 wheelchair seats throughout the stadium by 2010, and an additional 135 accessible seats in clubhouses to go along with the existing 88 wheelchair seats. This case was significant because it set a precedent for the uniform distribution of accessible seating and gave the DOJ the opportunity to clarify previously unclear rules. The agreement now is a blueprint for all stadiums and other public facilities regarding accessibility.

Paralyzed Veterans of America v. Ellerbe Becket Architects and Engineers
One of the first major ADA lawsuits, Paralyzed Veterans of America v. Ellerbe Becket Architects and Engineers (PVA 1996) was focused on the wheelchair accessibility of a stadium project that was still in the design phase, MCI Center (now known as Capital One Arena) in Washington, D.C. Previous to this case, which was filed only five years after the ADA was passed, the DOJ was unable or unwilling to provide clarification on the distribution requirements for accessible wheelchair locations in large assembly spaces. While Section 4.33.3 of ADAAG makes reference to lines of sight, no specific reference is made to seeing over standing patrons. The MCI Center, designed by Ellerbe Becket Architects & Engineers, was designed with too few wheelchair and companion seats, and the ones that were included did not provide sight lines that would enable the wheelchair user to view the playing area while the spectators in front of them were standing. This case and another related case established precedent on seat distribution and sight lines issues for ADA enforcement that continues to present day.

Toyota Motor Manufacturing, Kentucky, Inc. v. Williams
Toyota Motor Manufacturing, Kentucky, Inc. v. Williams, was a case in which the US Supreme Court interpreted the meaning of the phrase "substantially impairs" as used in the Americans with Disabilities Act. It reversed a Sixth Circuit Court of Appeals decision to grant partial summary judgment in favor of the respondent, Ella Williams, that classified her inability to perform manual job-related tasks as a disability. The Court held that the "major life activity" definition for evaluating the performance of manual tasks focuses the inquiry on whether Williams was unable to perform a range of tasks central to most people in carrying out the activities of daily living, not whether Williams was unable to perform her specific job tasks. Therefore, the determination of whether an impairment rises to the level of a disability is not limited to activities in the workplace solely, but rather to manual tasks in life in general. When the Supreme Court applied this standard, it found that the Court of Appeals had incorrectly determined the presence of a disability because it relied solely on her inability to perform specific manual work tasks, which was insufficient in proving the presence of a disability. The Court of Appeals should have taken into account the evidence presented that Williams retained the ability to do personal tasks and household chores, such activities being the nature of tasks most people do in their daily lives, and placed too much emphasis on her job disability. Since the evidence showed that Williams was performing normal daily tasks, it ruled that the Court of Appeals erred when it found that Williams was disabled. This ruling has since been invalidated by the ADAAA. In fact, Congress explicitly cited Toyota v. Williams in the text of the ADAAA itself as one of its driving influences for passing the ADAAA.

US Airways, Inc. v. Barnett
US Airways, Inc. v. Barnett was decided by the US Supreme Court in 2002. This case held that even requests for accommodation that might seem reasonable on their face, e.g., a transfer to a different position, can be rendered unreasonable because it would require a violation of the company's seniority system. While the court held that, in general, a violation of a seniority system renders an otherwise reasonable accommodation unreasonable, a plaintiff can present evidence that, despite the seniority system, the accommodation is reasonable in the specific case at hand, e.g., the plaintiff could offer evidence that the seniority system is so often disregarded that another exception would not make a difference.

Importantly, the court held that the defendant need not provide proof that this particular application of the seniority system should prevail, and that, once the defendant showed that the accommodation violated the seniority system, it fell to Barnett to show it was nevertheless reasonable.

In this case, Barnett was a US Airways employee who injured his back, rendering him physically unable to perform his cargo-handling job. Invoking seniority, he transferred to a less-demanding mailroom job, but this position later became open to seniority-based bidding and was bid on by more senior employees. Barnett requested the accommodation of being allowed to stay on in the less-demanding mailroom job. US Airways denied his request, and he lost his job.

The Supreme Court decision invalidated both the approach of the district court, which found that the mere presence and importance of the seniority system was enough to warrant a summary judgment in favor of US Airways, as well as the circuit court's approach that interpreted 'reasonable accommodation' as 'effective accommodation.'

Access Now v. Southwest Airlines
Access Now, Inc. v. Southwest Airlines Co. was a 2002 case where the District Court decided that the website of Southwest Airlines was not in violation of the Americans with Disabilities Act, because the ADA is concerned with things with a physical existence and thus cannot be applied to cyberspace. Judge Patricia A. Seitz found that the "virtual ticket counter" of the website was a virtual construct, and hence not a "public place of accommodation". As such, "To expand the ADA to cover 'virtual' spaces would be to create new rights without well-defined standards."

Ouellette v. Viacom International Inc.
Ouellette v. Viacom International Inc. (2011) held that a mere online presence does not subject a website to the ADA guidelines. Thus Myspace and YouTube were not liable for a dyslexic man's inability to navigate the site regardless of how impressive the "online theater" is.

Authors Guild v. HathiTrust
Authors Guild v. HathiTrust was a case in which the District Court decided that the HathiTrust digital library was a transformative, fair use of copyrighted works, making a large number of written text available to those with print disability.

Zamora-Quezada v. HealthTexas Medical Group
Zamora-Quezada v. HealthTexas Medical Group (begun in 1998) was the first time this act was used against HMOs when a novel lawsuit was filed by Texas attorney Robert Provan against five HMOs for their practice of revoking the contracts of doctors treating disabled patients. In 1999, these HMOs sought to dismiss Provan's lawsuit, but a federal court ruled against them, and the case was settled out of court. Many decisions relating to Provan's unique lawsuit against these HMOs have been cited in other court cases since.

Campbell v. General Dynamics Government Systems Corp.
Campbell v. General Dynamics Government Systems Corp. (2005) concerned the enforceability of a mandatory arbitration agreement contained in a dispute resolution policy linked to an e-mailed company-wide announcement, insofar as it applies to employment discrimination claims brought under the Americans with Disabilities Act.

Tennessee v. Lane
Tennessee v. Lane, 541 U.S. 509 (2004), was a case in the Supreme Court of the United States involving Congress's enforcement powers under section 5 of the Fourteenth Amendment. George Lane was unable to walk after a 1997 car accident in which he was accused of driving on the wrong side of the road. A woman was killed in the crash, and Lane faced misdemeanor charges of reckless driving. The suit was brought about because he was denied access to appear in criminal court because the courthouse had no elevator, even though the court was willing to carry him up the stairs and then willing to move the hearing to the first floor. He refused, citing he wanted to be treated as any other citizen, and was subsequently charged with failure to appear, after appearing at a previous hearing where he dragged himself up the stairs. The court ruled that Congress did have enough evidence that disabled people were being denied those fundamental rights that are protected by the Due Process clause of the Fourteenth Amendment and had the enforcement powers under section 5 of the Fourteenth Amendment. It further ruled that "reasonable accommodations" mandated by the ADA were not unduly burdensome and disproportionate to the harm.

Gender dysphoria
In 2022, the United States Court of Appeals for the Fourth Circuit stated that the ADA covers individuals with gender dysphoria, which may aid transgender people in accessing legal protections they otherwise may be unable to.

title: Americans with Disabilities Act of 1990


text:
Apple I

The Apple Computer 1 (Apple-1), later known predominantly as the Apple I, is an 8-bit motherboard-only personal computer designed by Steve Wozniak and released by the Apple Computer Company (now Apple Inc.) in 1976. The company was initially formed to sell the Apple I – its first product – and would later become the world's largest technology company. The idea of starting a company and selling the computer came from Wozniak's friend and Apple co-founder Steve Jobs. One of the main innovations of the Apple I was that it included video display terminal circuitry and a keyboard interface on a single board, allowing it to connect to a low-cost composite video monitor instead of an expensive computer terminal, compared to most existing computers at the time. It was one of the first computers to have such video output, released at about the same time as the Sol-20, which has similar capability.

To finance the Apple I's development, Wozniak and Jobs sold some of their possessions for a few hundred dollars. Wozniak demonstrated the first prototype in July 1976 at the Homebrew Computer Club in Palo Alto, California, impressing an early computer retailer. After securing an order for 50 computers, Jobs was able to order the parts on credit and deliver the first Apple products after ten days.

The Apple I was one of the first computers available that used the inexpensive MOS Technology 6502 microprocessor. An expansion included a BASIC interpreter, allowing users to utilize BASIC at home instead of at institutions with mainframe computers, greatly lowering the entry cost for computing with BASIC.

Production was discontinued on September 30, 1977, after the June 10, 1977 introduction of its successor, the Apple II, which Byte magazine referred to as part of the "1977 Trinity" of personal computing (along with the PET 2001 from Commodore Business Machines and the TRS-80 Model I from Tandy Corporation). As relatively few computers were made before they were discontinued, coupled with their status as Apple's first product, surviving Apple I units are now displayed in computer museums.

Development
In 1975, Steve Wozniak started attending meetings of the Homebrew Computer Club, which was a major source of inspiration for him. New microcomputers such as the Altair 8800 inspired Wozniak to build a microprocessor into his video terminal circuit to make a complete computer. At the time the only appropriate CPUs available were the Intel 8080, and the Motorola 6800. Of these options, Wozniak preferred the 6800, though he was financially unable to obtain either. Instead, he began designing computers on paper until he could afford a CPU.

When the $25 MOS Technology 6502 was released in late 1975, Wozniak wrote a version of BASIC for it, then began to design a computer for it to run on. The 6502 was developed by many of the same engineers that designed the 6800, as many in Silicon Valley left employers to form their own companies. Wozniak's earlier 6800 computer design needed only minor changes to run on the new processor.

By March 1, 1976, Wozniak completed the basic design of his computer. Wozniak originally offered the design to HP while working there, but it was rejected by the company on five occasions. When he demonstrated his computer at the Homebrew Computer Club, his friend and fellow club regular Steve Jobs was immediately interested in its commercial potential. Wozniak intended to share schematics of the machine for free, but Jobs advised him to start a business together and sell bare printed circuit boards for the computer. Wozniak, at first skeptical, was later convinced by Jobs that even if they were not successful they could at least say to their grandchildren that they had had their own company. To raise the money they needed to build the first batch of the circuit boards, Wozniak sold his HP-65 scientific calculator while Jobs sold his Volkswagen van.

After the company was formed, Jobs and Wozniak gave a presentation of the fully assembled "Apple Computer A" at the Homebrew Computer Club. Paul Terrell, who was starting a new computer shop in Mountain View, California, called the Byte Shop, saw the presentation and was impressed by the machine. Terrell told Jobs that he would order 50 units of the Apple I and pay $500 each on delivery, but only if they came fully assembled – he was not interested in buying bare printed circuit boards with no components.

Jobs took the purchase order from the Byte Shop to national electronic parts distributor Cramer Electronics, and ordered the components needed. When asked by the credit manager how he would pay for the parts, Jobs replied, "I have this purchase order from the Byte Shop chain of computer stores for 50 of my computers and the payment terms are COD. If you give me the parts on net 30-day terms I can build and deliver the computers in that time frame, collect my money from Terrell at the Byte Shop and pay you."

To verify the purchase order, the credit manager called Paul Terrell, who assured him if the computers showed up, Jobs would have more than enough money for the parts order. The two Steves and their small crew spent day and night building and testing the computers, and delivered to Terrell on time. Terrell was surprised to receive a batch of assembled circuit boards, as he had expected complete computers with a case, monitor and keyboard. Nonetheless, he kept his word and paid the two Steves the money promised.

Announcement and sales
The Apple I went on sale in July 1976 at a price of US$666.66. Wozniak later said he had no idea about the relation between the number and the number of the beast, and that he came up with the price because he liked "repeating digits" and because it was a one-third markup on the US$500 wholesale price. Jobs had managed to get the inventory into the nation's first four storefront microcomputer retailers: Byte Shop (Palo Alto, California), itty bitty machine company (Evanston, Illinois), Data Domain (Bloomington, Indiana), and Computer Mart (New York City).

The first unit produced was used in a high school math class, and donated to Liza Loop's public-access computer center. About 200 units were produced, and all but 25 were sold within nine or ten months.

In April 1977, the price was dropped to $475. It continued to be sold through August 1977, despite the introduction of the Apple II in April 1977, which began shipping in June of that year. In October 1977, the Apple I was officially discontinued and removed from Apple's price list. As Wozniak was the only person who could answer most customer support questions about the computer, the company offered Apple I owners discounts and trade-ins for Apple IIs to persuade them to return their computers. These recovered boards were then destroyed by Apple, contributing to their later rarity.

Both Steve Jobs and Steve Wozniak have stated that Apple did not assign serial numbers to the Apple l. Several boards have been found with numbered stickers affixed to them, which appear to be inspection stickers from the PCB manufacturer/assembler. A batch of boards is known to have numbers hand-written in black permanent marker on the back; these usually appear as "01-00##". As of January 2022, 29 Apple-1s with a serial number are known. The highest known number is 01–0079. Two original Apple-1s have been analyzed by PSA, Los Angeles, concluding the serial numbers had been hand-written by Steve Jobs.

Hardware
The Apple I used a MOS Technologies 6502 microprocessor running at $1.023 MHz$, and its design was based largely on Wozniak's previous work centered around a Motorola 6800. The unconventional clock speed was chosen to be a fraction ($2/7$) of the NTSC color carrier, which simplified video circuitry. $4 KB$ of memory was included on the base machine, which was expandable to $8 KB$ on-board and up to $64 KB$ by using an add-on card. On-board memory utilized newly-available 4Kbit DRAM chips, and was designed to be upgradeable to the next generation of 16Kbit chips for a maximum of $32 KB$ on-board memory. An optional $75 plug-in cassette interface card allowed users to store programs on ordinary audio cassette tapes. A BASIC interpreter, originally written by Wozniak, was provided with the cassette interface that let users easily write programs and play simple games. An onboard AC power supply was included.

The Apple I did not come with a case. It could be used bare, though some users chose to build custom (typically wooden) enclosures.

Video and Input
The Apple I included built-in computer terminal circuitry with composite video output. To use the computer, a user-supplied composite monitor and ASCII-encoded keyboard needed to be connected. If a monitor was not available, a standard television set could be used along with an RF modulator. In comparison, competing machines generally required an expensive dedicated video display terminal or teletypewriter. This, combined with its single-board construction, made the Apple I an elegant and inexpensive machine for its day, though competitors such as the Sol-20 and Sphere 1 offered similar feature sets.

The computer generated its video output using a shift register memory and a Signetics 2513 64×8×5 Character Generator. It was capable of displaying uppercase characters, numbers and basic punctuation and math symbols with a 5x8 pixel font:

{{legend|#EFF|Symbols and punctuation}}

Apple Cassette Interface expansion
A cassette interface was available in the form of an optional add-on for the Apple I's expansion slot. A cassette deck plugged in to the expansion's phone connector ports could be written to and read from as a form of removable storage. The only alternative to the interface for loading programs was typing machine code by hand, making the add-on "ubiquitous".

The expansion came with a free cassette tape containing Steve Wozniak's Integer BASIC interpreter. Other software tapes were supplied "at minimal cost" including ported video games such as Hamurabi, Lunar Lander and Star Trek.

Conservation
Only about 200 Apple I boards were produced, and the whereabouts of 62 to 82 are known. After the success of the Apple II, and of Apple broadly, the Apple I was recognized as an important historical computer. According to the 1986 Apple IIe Owner's Guide, an Apple I was then worth "between $10,000 and $15,000" and a board was reportedly sold for $50,000 in 1999.

In November 2010, an Apple I with a cache of original documents and packaging sold for £133,250 ($) at Christie's auction house in London. The documents included the return label showing Steve Jobs's parents' address, a personally typed and signed letter from Jobs (answering technical questions about the computer), and the invoice (listing "Steven" as the salesman). The computer was brought to Polytechnic University of Turin for restoration.

In October 2014 the Henry Ford Museum purchased an Apple I at a Bonhams auction for US$905000. The sale included the keyboard, monitor, cassette decks and a manual. In 2017, an Apple I removed from Steve Jobs's office in 1985 by Apple quality control engineer Don Hutmacher was placed on display at Living Computers: Museum + Labs.

On May 30, 2015, an elderly woman reportedly dropped off boxes of electronics for disposal at an electronics recycling center in the Silicon Valley of Northern California. Included in the electronics (removed from her garage after the death of her husband) was an original Apple I computer, which the recycling firm sold for US$200000. When a discarded item is sold, it is the company's practice to give 50% of the proceeds to the original owner, but the woman has not been identified.

Apple I computers with original documents and memorabilia have frequently been auctioned for over $300,000 throughout the 2010s  and 2020s. The production prototype for the Apple I survives in a badly damaged state and was itself auctioned in 2022 for $677,196.

Replicas
Several Apple I clones and replicas have been released in recent years. These are created by hobbyists and marketed to the hobbyist/collector community. Availability is usually limited to small runs in response to demand.

Emulation
Emulation software for the Apple I has been written for modern home computers  and for web browsers. It has also been emulated on 1980s era computers including the SAM Coupé and Commodore 64.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Apple I


text:
Apatosaurus

Apatosaurus ( meaning "deceptive lizard") is a genus of herbivorous sauropod dinosaur that lived in North America during the Late Jurassic period. Othniel Charles Marsh described and named the first-known species, A. ajax, in 1877, and a second species, A. louisae, was discovered and named by William H. Holland in 1916. Apatosaurus lived about 152 to 151 million years ago (mya), during the late Kimmeridgian to early Tithonian age, and are now known from fossils in the Morrison Formation of modern-day Colorado, Oklahoma, New Mexico, Wyoming, and Utah in the United States. Apatosaurus had an average length of 21 - 23 m, and an average mass of 16.4 - 22.4 t. A few specimens indicate a maximum length of 11–30% greater than average and a mass of approximately 33 t.

The cervical vertebrae of Apatosaurus are less elongated and more heavily constructed than those of Diplodocus, a diplodocid like Apatosaurus, and the bones of the leg are much stockier despite being longer, implying that Apatosaurus was a more robust animal. The tail was held above the ground during normal locomotion. Apatosaurus had a single claw on each forelimb and three on each hindlimb. The Apatosaurus skull, long thought to be similar to Camarasaurus, is much more similar to that of Diplodocus. Apatosaurus was a generalized browser that likely held its head elevated. To lighten its vertebrae, Apatosaurus had air sacs that made the bones internally full of holes. Like that of other diplodocids, its tail may have been used as a whip to create loud noises, or, as more recently suggested, as a sensory organ.

The skull of Apatosaurus was confused with that of Camarasaurus and Brachiosaurus until 1909, when the holotype of A. louisae was found, and a complete skull just a few meters away from the front of the neck. Henry Fairfield Osborn disagreed with this association, and went on to mount a skeleton of Apatosaurus with a Camarasaurus skull cast. Apatosaurus skeletons were mounted with speculative skull casts until 1970, when McIntosh showed that more robust skulls assigned to Diplodocus were more likely from Apatosaurus.

Apatosaurus is a genus in the family Diplodocidae. It is one of the more basal genera, with only Amphicoelias and possibly a new, unnamed genus more primitive. Although the subfamily Apatosaurinae was named in 1929, the group was not used validly until an extensive 2015 study. Only Brontosaurus is also in the subfamily, with the other genera being considered synonyms or reclassified as diplodocines. Brontosaurus has long been considered a junior synonym of Apatosaurus; its type species was reclassified as A.excelsus in 1903. A 2015 study concluded that Brontosaurus is a valid genus of sauropod distinct from Apatosaurus, but not all paleontologists agree with this division. As it existed in North America during the late Jurassic, Apatosaurus would have lived alongside dinosaurs such as Allosaurus, Camarasaurus, Diplodocus, and Stegosaurus.

Description
Apatosaurus was a large, long-necked, quadrupedal animal with a long, whip-like tail. Its forelimbs were slightly shorter than its hindlimbs. Most size estimates are based on specimen CM3018, the type specimen of A.louisae, reaching 21 - 23 m in length and 16.4 - 22.4 t in body mass. A 2015 study that estimated the mass of volumetric models of Dreadnoughtus, Apatosaurus, and Giraffatitan estimates CM3018 at 21.8 - 38.2 t, similar in mass to Dreadnoughtus. Some specimens of A.ajax (such as OMNH1670) represent individuals 11–30% longer, suggesting masses twice that of CM3018 or 32.7 - 72.6 t, potentially rivaling the largest titanosaurs. However, the upper size estimate of OMNH1670 is likely an exaggeration, with the size estimates revised in 2020 at 30 m in length and 33 MT in body mass based on volumetric analysis. The skull is small in relation to the size of the animal. The jaws are lined with spatulate (chisel-like) teeth suited to an herbivorous diet. The snout of Apatosaurus and similar diplodocoids is squared, with only Nigersaurus having a squarer skull. The braincase of Apatosaurus is well preserved in specimen BYU17096, which also preserved much of the skeleton. A phylogenetic analysis found that the braincase had a morphology similar to those of other diplodocoids. Some skulls of Apatosaurus have been found still in articulation with their teeth. Those teeth that have the enamel surface exposed do not show any scratches on the surface; instead, they display a sugary texture and little wear. Like those of other sauropods, the neck vertebrae are deeply bifurcated; they carried neural spines with a large trough in the middle, resulting in a wide, deep neck. The vertebral formula for the holotype of A.louisae is 15cervicals, 10dorsals, 5sacrals, and 82caudals. The caudal vertebra number may vary, even within species. The cervical vertebrae of Apatosaurus and Brontosaurus are stouter and more robust than those of other diplodocids and were found to be most similar to Camarasaurus by Charles Whitney Gilmore. In addition, they support cervical ribs that extend farther towards the ground than in diplodocines, and have vertebrae and ribs that are narrower towards the top of the neck, making the neck nearly triangular in cross-section. In Apatosaurus louisae, the atlas-axis complex of the first cervicals is nearly fused. The dorsal ribs are not fused or tightly attached to their vertebrae and are instead loosely articulated. Apatosaurus has ten dorsal ribs on either side of the body. The large neck was filled with an extensive system of weight-saving air sacs. Apatosaurus, like its close relative Supersaurus, has tall neural spines, which make up more than half the height of the individual bones of its vertebrae. The shape of the tail is unusual for a diplodocid; it is comparatively slender because of the rapidly decreasing height of the vertebral spines with increasing distance from the hips. Apatosaurus also had very long ribs compared to most other diplodocids, giving it an unusually deep chest. As in other diplodocids, the tail transformed into a whip-like structure towards the end. The limb bones are also very robust. Within Apatosaurinae, the scapula of Apatosaurus louisae is intermediate in morphology between those of A.ajax and Brontosaurus excelsus. The arm bones are stout, so the humerus of Apatosaurus resembles that of Camarasaurus, as well as Brontosaurus. However, the humeri of Brontosaurus and A.ajax are more similar to each other than they are to A.louisae. In 1936, Charles Gilmore noted that previous reconstructions of Apatosaurus forelimbs erroneously proposed that the radius and ulna could cross; in life they would have remained parallel. Apatosaurus had a single large claw on each forelimb, a feature shared by all sauropods more derived than Shunosaurus. The first three toes had claws on each hindlimb. The phalangeal formula is 2-1-1-1-1, meaning the innermost finger (phalanx) on the forelimb has two bones and the next has one. The single manual claw bone (ungual) is slightly curved and squarely truncated on the anterior end. The pelvic girdle includes the robust ilia, and the fused (co-ossified) pubes and ischia. The femora of Apatosaurus are very stout and represent some of the most robust femora of any member of Sauropoda. The tibia and fibula bones are different from the slender bones of Diplodocus but are nearly indistinguishable from those of Camarasaurus. The fibula is longer and slenderer than the tibia. The foot of Apatosaurus has three claws on the innermost digits; the digit formula is 3-4-5-3-2. The first metatarsal is the stoutest, a feature shared among diplodocids.

Initial discovery
The first Apatosaurus fossils were discovered by Arthur Lakes, a local miner, and his friend Henry C. Beckwith in the spring of 1877 in Morrison, a town in the eastern foothills of the Rocky Mountains in Jefferson County, Colorado. Arthur Lakes wrote to Othniel Charles Marsh, Professor of Paleontology at Yale University, and Edward Drinker Cope, paleontologist based in Philadelphia, about the discovery until eventually collecting several fossils and sending them to both paleontologists. Marsh named Atlantosaurus montanus based on some of the fossils sent and hired Lakes to collect the rest of the material at Morrison and send it to Yale, while Cope attempted to hire Lakes as well but was rejected. One of the best specimens collected by Lakes in 1877 was a well preserved partial postcranial skeleton, including many vertebrae, and a partial braincase (YPM VP 1860), which was sent to Marsh and named Apatosaurus ajax in November 1877. The composite term Apatosaurus comes from the Greek words apatē (ἀπάτη)/apatēlos (ἀπατηλός) meaning "deception"/"deceptive", and sauros (σαῦρος) meaning "lizard"; thus, "deceptive lizard". Marsh gave it this name based on the chevron bones, which are dissimilar to those of other dinosaurs; instead, the chevron bones of Apatosaurus showed similarities with those of mosasaurs, most likely that of the representative species Mosasaurus. By the end of excavations at Lakes' quarry in Morrison, several partial specimens of Apatosaurus had been collected, but only the type specimen of A. ajax can be confidently referred to the species.

During excavation and transportation, the bones of the holotype skeleton were mixed with those of another Apatosaurine individual originally described as Atlantosaurus immanis; as a consequence, some elements cannot be ascribed to either specimen with confidence. Marsh distinguished the new genus Apatosaurus from Atlantosaurus on the basis of the number of sacral vertebrae, with Apatosaurus possessing three and Atlantosaurus four. Recent research shows that traits usually used to distinguish taxa at this time were actually widespread across several taxa, causing many of the taxa named to be invalid, like Atlantosaurus. Two years later, Marsh announced the discovery of a larger and more complete specimen (YPM VP 1980) from Como Bluff, Wyoming, he gave this specimen the name Brontosaurus excelsus. Also at Como Bluff, the Hubbell brothers working for Edward Drinker Cope collected a tibia, fibula, scapula, and several caudal vertebrae along with other fragments belonging to Apatosaurus in 1877–78 at Cope's Quarry 5 at the site. Later in 1884, Othniel Marsh named Diplodocus lacustris based on a chimeric partial dentary, snout, and several teeth collected by Lakes in 1877 at Morrison. In 2013, it was suggested that the dentary of D. lacustris and its teeth were actually from Apatosaurus ajax based on its proximity to the type braincase of A. ajax. All specimens currently considered Apatosaurus were from the Morrison Formation, the location of the excavations of Marsh and Cope.

Second Dinosaur Rush and skull issue
After the end of the Bone Wars, many major institutions in the eastern United States were inspired by the depictions and finds by Marsh and Cope to assemble their own dinosaur fossil collections. The competition to mount the first sauropod skeleton specifically was the most intense, with the American Museum of Natural History, Carnegie Museum of Natural History, and Field Museum of Natural History all sending expeditions to the west to find the most complete sauropod specimen, bring it back to the home institution, and mount it in their fossil halls. The American Museum of Natural History was the first to launch an expedition, finding a well preserved skeleton (AMNH 460), which is occasionally assigned to Apatosaurus, is considered nearly complete; only the head, feet, and sections of the tail are missing, and it was the first sauropod skeleton mounted. The specimen was found north of Medicine Bow, Wyoming, in 1898 by Walter Granger, and took the entire summer to extract. To complete the mount, sauropod feet that were discovered at the same quarry and a tail fashioned to appear as Marsh believed it should – but which had too few vertebrae – were added. In addition, a sculpted model of what the museum thought the skull of this massive creature might look like was made. This was not a delicate skull like that of Diplodocus – which was later found to be more accurate – but was based on "the biggest, thickest, strongest skull bones, lower jaws and tooth crowns from three different quarries". These skulls were likely those of Camarasaurus, the only other sauropod for which good skull material was known at the time. The mount construction was overseen by Adam Hermann, who failed to find Apatosaurus skulls. Hermann was forced to sculpt a stand-in skull by hand. Osborn said in a publication that the skull was "largely conjectural and based on that of Morosaurus" (now Camarasaurus). In 1903, Elmer Riggs published a study that described a well-preserved skeleton of a diplodocid from the Grand River Valley near Fruita, Colorado, Field Museum of Natural History specimen P25112. Riggs thought that the deposits were similar in age to those of the Como Bluff in Wyoming from which Marsh had described Brontosaurus. Most of the skeleton was found, and after comparison with both Brontosaurus and Apatosaurus ajax, Riggs realized that the holotype of A.ajax was immature, and thus the features distinguishing the genera were not valid. Since Apatosaurus was the earlier name, Brontosaurus should be considered a junior synonym of Apatosaurus. Because of this, Riggs recombined Brontosaurus excelsus as Apatosaurus excelsus. Based on comparisons with other species proposed to belong to Apatosaurus, Riggs also determined that the Field Columbian Museum specimen was likely most similar to A.excelsus.

Despite Riggs' publication, Henry Fairfield Osborn, who was a strong opponent of Marsh and his taxa, labeled the Apatosaurus mount of the American Museum of Natural History Brontosaurus. Because of this decision the name Brontosaurus was commonly used outside of scientific literature for what Riggs considered Apatosaurus, and the museum's popularity meant that Brontosaurus became one of the best known dinosaurs, even though it was invalid throughout nearly all of the 20th and early 21st centuries. It was not until 1909 that an Apatosaurus skull was found during the first expedition, led by Earl Douglass, to what would become known as the Carnegie Quarry at Dinosaur National Monument. The skull was found a short distance from a skeleton (specimen CM3018) identified as the new species Apatosaurus louisae, named after Louise Carnegie, wife of Andrew Carnegie, who funded field research to find complete dinosaur skeletons in the American West. The skull was designated CM11162; it was very similar to the skull of Diplodocus. Another smaller skeleton of A.louisae was found nearby CM11162 and CM3018. The skull was accepted as belonging to the Apatosaurus specimen by Douglass and Carnegie Museum director William H. Holland, although other scientists – most notably Osborn – rejected this identification. Holland defended his view in 1914 in an address to the Paleontological Society of America, yet he left the Carnegie Museum mount headless. While some thought Holland was attempting to avoid conflict with Osborn, others suspected Holland was waiting until an articulated skull and neck were found to confirm the association of the skull and skeleton. After Holland's death in 1934, museum staff placed a cast of a Camarasaurus skull on the mount.

While most other museums were using cast or sculpted Camarasaurus skulls on Apatosaurus mounts, the Yale Peabody Museum decided to sculpt a skull based on the lower jaw of a Camarasaurus, with the cranium based on Marsh's 1891 illustration of the skull. The skull also included forward-pointing nasals – something unusual for any dinosaur – and fenestrae differing from both the drawing and other skulls. No Apatosaurus skull was mentioned in literature until the 1970s when John Stanton McIntosh and David Berman redescribed the skulls of Diplodocus and Apatosaurus. They found that though he never published his opinion, Holland was almost certainly correct, that Apatosaurus had a Diplodocus-like skull. According to them, many skulls long thought to pertain to Diplodocus might instead be those of Apatosaurus. They reassigned multiple skulls to Apatosaurus based on associated and closely associated vertebrae. Even though they supported Holland, it was noted that Apatosaurus might have possessed a Camarasaurus-like skull, based on a disarticulated Camarasaurus-like tooth found at the precise site where an Apatosaurus specimen was found years before. On October20, 1979, after the publications by McIntosh and Berman, the first true skull of Apatosaurus was mounted on a skeleton in a museum, that of the Carnegie. In 1998, it was suggested that the Felch Quarry skull that Marsh had included in his 1896 skeletal restoration instead belonged to Brachiosaurus. This was supported in 2020 with a redescription of the brachiosaurid material found at the Felch Quarry.

Recent discoveries and reassessment
In 2011, the first specimen of Apatosaurus where a skull was found articulated with its cervical vertebrae was described. This specimen, CMCVP7180, was found to differ in both skull and neck features from A.louisae, but shared many features of the cervical vertebrae with A.ajax. Another well-preserved skull is Brigham Young University specimen 17096, a well-preserved skull and skeleton, with a preserved braincase. The specimen was found in Cactus Park Quarry in western Colorado. In 2013, Matthew Mossbrucker and several other authors published an abstract that described a premaxilla and maxilla from Lakes' original quarry in Morrison and referred the material to Apatosaurus ajax. Almost all modern paleontologists agreed with Riggs that the two dinosaurs should be classified together in a single genus. According to the rules of the ICZN (which governs the scientific names of animals), the name Apatosaurus, having been published first, has priority as the official name; Brontosaurus was considered a junior synonym and was therefore long discarded from formal use. Despite this, at least one paleontologist – Robert T. Bakker – argued in the 1990s that A.ajax and A.excelsus were in fact sufficiently distinct for the latter to merit a separate genus.

In 2015, Emanuel Tschopp, Octávio Mateus, and Roger Benson released a paper on diplodocoid systematics, and proposed that genera could be diagnosed by thirteen differing characters, and species separated based on six. The minimum number for generic separation was chosen based on the fact that A.ajax and A.louisae differ in twelve characters, and Diplodocus carnegiei and D.hallorum differ in eleven characters. Thus, thirteen characters were chosen to validate the separation of genera. The six differing features for specific separation were chosen by counting the number of differing features in separate specimens generally agreed to represent one species, with only one differing character in D.carnegiei and A.louisae, but five differing features in B.excelsus. Therefore, Tschopp etal. argued that Apatosaurus excelsus, originally classified as Brontosaurus excelsus, had enough morphological differences from other species of Apatosaurus that it warranted being reclassified as a separate genus again. The conclusion was based on a comparison of 477 morphological characteristics across 81 different dinosaur individuals. Among the many notable differences are the wider – and presumably stronger – neck of Apatosaurus species compared to B.excelsus. Other species previously assigned to Apatosaurus, such as Elosaurus parvus and Eobrontosaurus yahnahpin were also reclassified as Brontosaurus. Some features proposed to separate Brontosaurus from Apatosaurus include: posterior dorsal vertebrae with the centrum longer than wide; the scapula rear to the acromial edge and the distal blade being excavated; the acromial edge of the distal scapular blade bearing a rounded expansion; and the ratio of the proximodistal length to transverse breadth of the astragalus 0.55 or greater. Sauropod expert Michael D'Emic pointed out that the criteria chosen were to an extent arbitrary and that they would require abandoning the name Brontosaurus again if newer analyzes obtained different results. Mammal paleontologist Donald Prothero criticized the mass media reaction to this study as superficial and premature, concluding that he would keep "Brontosaurus" in quotes and not treat the name as a valid genus.

Valid species
Many species of Apatosaurus have been designated from scant material. Marsh named as many species as he could, which resulted in many being based upon fragmentary and indistinguishable remains. In 2005, Paul Upchurch and colleagues published a study that analyzed the species and specimen relationships of Apatosaurus. They found that A.louisae was the most basal species, followed by FMNHP25112, and then a polytomy of A.ajax, A.parvus, and A.excelsus. Their analysis was revised and expanded with many additional diplodocid specimens in 2015, which resolved the relationships of Apatosaurus slightly differently, and also supported separating Brontosaurus from Apatosaurus.

 * Apatosaurus ajax was named by Marsh in 1877 after Ajax, a hero from Greek mythology. Marsh designated the incomplete, juvenile skeleton YPM1860 as its holotype. The species is less studied than Brontosaurus and A.louisae, especially because of the incomplete nature of the holotype. In 2005, many specimens in addition to the holotype were found assignable to A.ajax, YPM1840, NSMT-PV 20375, YPM1861, and AMNH460. The specimens date from the late Kimmeridgian to the early Tithonian ages. In 2015, only the A.ajax holotype YPM1860 assigned to the species, with AMNH460 found either to be within Brontosaurus, or potentially its own taxon. However, YPM1861 and NSMT-PV 20375 only differed in a few characteristics, and cannot be distinguished specifically or generically from A.ajax. YPM1861 is the holotype of "Atlantosaurus" immanis, which means it might be a junior synonym of A.ajax.
 * Apatosaurus louisae was named by Holland in 1916, being first known from a partial skeleton that was found in Utah. The holotype is CM3018, with referred specimens including CM3378, CM11162, and LACM52844. The former two consist of a vertebral column; the latter two consist of a skull and a nearly complete skeleton, respectively. Apatosaurus louisae specimens all come from the late Kimmeridgian of Dinosaur National Monument. In 2015, Tschopp etal. found the type specimen of Apatosaurus laticollis to nest closely with CM3018, meaning the former is likely a junior synonym of A.louisae.

The cladogram below is the result of an analysis by Tschopp, Mateus, and Benson (2015). The authors analyzed most diplodocid type specimens separately to deduce which specimen belonged to which species and genus.

Reassigned species

 * Apatosaurus grandis was named in 1877 by Marsh in the article that described A.ajax. It was briefly described, figured, and diagnosed. Marsh later mentioned it was only provisionally assigned to Apatosaurus when he reassigned it to his new genus Morosaurus in 1878. Since Morosaurus has been considered a synonym of Camarasaurus, C.grandis is the oldest-named species of the latter genus.
 * Apatosaurus excelsus was the original type species of Brontosaurus, first named by Marsh in 1879. Elmer Riggs reclassified Brontosaurus as a synonym of Apatosaurus in 1903, transferring the species B.excelsus to A.excelsus. In 2015, Tschopp, Mateus, and Benson argued that the species was distinct enough to be placed in its own genus, so they reclassified it back into Brontosaurus.
 * Apatosaurus parvus, first described from a juvenile specimen as Elosaurus in 1902 by Peterson and Gilmore, was reassigned to Apatosaurus in 1994, and then to Brontosaurus in 2015. Many other, more mature specimens were assigned to it following the 2015 study.
 * Apatosaurus minimus was originally described as a specimen of Brontosaurus sp. in 1904 by Osborn. In 1917, Henry Mook named it as its own species, A.minimus, for a pair of ilia and their sacrum. In 2012, Mike P. Taylor and Matt J. Wedel published a short abstract describing the material of A. minimus, finding it hard to place among either Diplodocoidea or Macronaria. While it was placed with Saltasaurus in a phylogenetic analysis, it was thought to represent instead some form with convergent features from many groups. The study of Tschopp etal. did find that a camarasaurid position for the taxon was supported, but noted that the position of the taxon was found to be highly variable and there was no clearly more likely position.
 * Apatosaurus alenquerensis was named in 1957 by Albert-Félix de Lapparent and Georges Zbyweski. It was based on post cranial material from Portugal. In 1990, this material was reassigned to Camarasaurus, but in 1998 it was given its own genus, Lourinhasaurus. This was further supported by the findings of Tschopp etal. in 2015, where Lourinhasaurus was found to be sister to Camarasaurus and other camarasaurids.
 * Apatosaurus yahnahpin was named by James Filla and Patrick Redman in 1994. Bakker made A.yahnahpin the type species of a new genus, Eobrontosaurus in 1998, and Tschopp reclassified it as Brontosaurus yahnahpin in 2015.

Classification
Apatosaurus is a member of the family Diplodocidae, a clade of gigantic sauropod dinosaurs. The family includes some of the longest creatures ever to walk the earth, including Diplodocus, Supersaurus, and Barosaurus. Apatosaurus is sometimes classified in the subfamily Apatosaurinae, which may also include Suuwassea, Supersaurus, and Brontosaurus. Othniel Charles Marsh described Apatosaurus as allied to Atlantosaurus within the now-defunct group Atlantosauridae. In 1878, Marsh raised his family to the rank of suborder, including Apatosaurus, Atlantosaurus, Morosaurus (=Camarasaurus) and Diplodocus. He classified this group within Sauropoda, a group he erected in the same study. In 1903, Elmer S. Riggs said the name Sauropoda would be a junior synonym of earlier names; he grouped Apatosaurus within Opisthocoelia. Sauropoda is still used as the group name. In 2011, John Whitlock published a study that placed Apatosaurus a more basal diplodocid, sometimes less basal than Supersaurus.

Cladogram of the Diplodocidae after Tschopp, Mateus, and Benson (2015).

Paleobiology
It was believed throughout the 19th and early 20th centuries that sauropods like Apatosaurus were too massive to support their own weight on dry land. It was theorized that they lived partly submerged in water, perhaps in swamps. More recent findings do not support this; sauropods are now thought to have been fully terrestrial animals. A study of diplodocid snouts showed that the square snout, large proportion of pits, and fine, subparallel scratches of the teeth of Apatosaurus suggests it was a ground-height, nonselective browser. It may have eaten ferns, cycadeoids, seed ferns, horsetails, and algae. Stevens and Parish (2005) speculate that these sauropods fed from riverbanks on submerged water plants.

A 2015 study of the necks of Apatosaurus and Brontosaurus found many differences between them and other diplodocids, and that these variations may have shown that the necks of Apatosaurus and Brontosaurus were used for intraspecific combat. Various uses for the single claw on the forelimb of sauropods have been proposed. One suggestion is that they were used for defense, but their shape and size make this unlikely. It was also possible they were for feeding, but the most probable use for the claw was grasping objects such as tree trunks when rearing.

Trackways of sauropods like Apatosaurus show that they may have had a range of around 25 - 40 km per day, and that they could potentially have reached a top speed of 20 - 30 km per hour. The slow locomotion of sauropods may be due to their minimal muscling, or to recoil after strides. A trackway of a juvenile has led some to believe that they were capable of bipedalism, though this is disputed.

Neck posture
Diplodocids like Apatosaurus are often portrayed with their necks held high up in the air, allowing them to browse on tall trees. Some studies state diplodocid necks were less flexible than previously believed, because the structure of the neck vertebrae would not have allowed the neck to bend far upward, and that sauropods like Apatosaurus were adapted to low browsing or ground feeding.

Other studies by Taylor find that all tetrapods appear to hold their necks at the maximum possible vertical extension when in a normal, alert posture; they argue the same would hold true for sauropods barring any unknown, unique characteristics that set the soft tissue anatomy of their necks apart from that of other animals. Apatosaurus, like Diplodocus, would have held its neck angled upward with the head pointing downward in a resting posture. Kent Stevens and Michael Parrish (1999 and 2005) state Apatosaurus had a great feeding range; its neck could bend into a U-shape laterally. The neck's range of movement would have also allowed the head to feed at the level of the feet.

Matthew Cobley et al. (2013) dispute this, finding that large muscles and cartilage would have limited movement of the neck. They state the feeding ranges for sauropods like Diplodocus were smaller than previously believed, and the animals may have had to move their whole bodies around to better access areas where they could browse vegetation. As such, they might have spent more time foraging to meet their minimum energy needs. The conclusions of Cobley etal. are disputed by Taylor, who analyzed the amount and positioning of intervertebral cartilage to determine the flexibility of the neck of Apatosaurus and Diplodocus. He found that the neck of Apatosaurus was very flexible.

Physiology

Given the large body mass and long neck of sauropods like Apatosaurus, physiologists have encountered problems determining how these animals breathed. Beginning with the assumption that, like crocodilians, Apatosaurus did not have a diaphragm, the dead-space volume (the amount of unused air remaining in the mouth, trachea, and air tubes after each breath) has been estimated at about 184 L for a 30 t specimen. Paladino calculates its tidal volume (the amount of air moved in or out during a single breath) at 904 L with an avian respiratory system, 225 L if mammalian, and 19 L if reptilian.

On this basis, its respiratory system would likely have been parabronchi, with multiple pulmonary air sacs as in avian lungs, and a flow-through lung. An avian respiratory system would need a lung volume of about 600 L compared with a mammalian requirement of 2,950 L, which would exceed the space available. The overall thoracic volume of Apatosaurus has been estimated at 1,700 L, allowing for a 500 L, four-chambered heart and a 900 L lung capacity. That would allow about 300 L for the necessary tissue. Evidence for the avian system in Apatosaurus and other sauropods is also present in the pneumaticity of the vertebrae. Though this plays a role in reducing the weight of the animal, Wedel (2003) states they are also likely connected to air sacs, as in birds.

James Spotila et al. (1991) concludes that the large body size of sauropods would have made them unable to maintain high metabolic rates because they would not have been able to release enough heat. They assumed sauropods had a reptilian respiratory system. Wedel says that an avian system would have allowed it to dump more heat. Some scientists state that the heart would have had trouble sustaining sufficient blood pressure to oxygenate the brain. Others suggest that the near-horizontal posture of the head and neck would have eliminated the problem of supplying blood to the brain because it would not have been elevated.

James Farlow (1987) calculates that an Apatosaurus-sized dinosaur about 35 t would have possessed 5.7 t of fermentation contents, though he cautions that the regression equation being used is based on living mammals which are much smaller and physiologically different. Assuming Apatosaurus had an avian respiratory system and a reptilian resting-metabolism, Frank Paladino etal. (1997) estimate the animal would have needed to consume only about 262 L of water per day.

Growth
A 1999 microscopic study of Apatosaurus and Brontosaurus bones concluded the animals grew rapidly when young and reached near-adult sizes in about 10years. In 2008, a study on the growth rates of sauropods was published by Thomas Lehman and Holly Woodward. They said that by using growth lines and length-to-mass ratios, Apatosaurus would have grown to 25t (25 long tons; 28 short tons) in 15years, with growth peaking at 5000 kg in a single year. An alternative method, using limb length and body mass, found Apatosaurus grew 520 kg per year, and reached its full mass before it was about 70years old. These estimates have been called unreliable because the calculation methods are not sound; old growth lines would have been obliterated by bone remodeling. One of the first identified growth factors of Apatosaurus was the number of sacral vertebrae, which increased to five by the time of the creature's maturity. This was first noted in 1903 and again in 1936.

Long-bone histology enables researchers to estimate the age that a specific individual reached. A study by Eva Griebeler etal. (2013) examined long-bone histological data and concluded the Apatosaurus sp.SMA0014 weighed 20206 kg, reached sexual maturity at 21years, and died aged 28. The same growth model indicated Apatosaurus sp.BYU 601–17328 weighed 18178 kg, reached sexual maturity at 19years, and died aged 31.

Juveniles
Compared with most sauropods, a relatively large amount of juvenile material is known from Apatosaurus. Multiple specimens in the OMNH are from juveniles of an undetermined species of Apatosaurus; this material includes partial shoulder and pelvic girdles, some vertebrae, and limb bones. OMNH juvenile material is from at least two different age groups and based on overlapping bones likely comes from more than three individuals. The specimens exhibit features that distinguish Apatosaurus from its relatives, and thus likely belong to the genus. Juvenile sauropods tend to have proportionally shorter necks and tails, and a more pronounced forelimb-hindlimb disparity than found in adult sauropods.

Tail
An article published in 1997 reported research of the mechanics of Apatosaurus tails by Nathan Myhrvold and paleontologist Philip J. Currie. Myhrvold carried out a computer simulation of the tail, which in diplodocids like Apatosaurus was a very long, tapering structure resembling a bullwhip. This computer modeling suggested diplodocids were capable of producing a whiplike cracking sound of over 200 decibels, comparable to the volume of a cannon being fired.

A pathology has been identified on the tail of Apatosaurus, caused by a growth defect. Two caudal vertebrae are seamlessly fused along the entire articulating surface of the bone, including the arches of the neural spines. This defect might have been caused by the lack or inhibition of the substance that forms intervertebral disks or joints. It has been proposed that the whips could have been used in combat and defense, but the tails of diplodocids were quite light and narrow compared to Shunosaurus and mamenchisaurids, and thus to injure another animal with the tail would severely injure the tail itself. More recently, Baron (2020) considers the use of the tail as a bullwhip unlikely because of the potentially catastrophic muscle and skeletal damage such speeds could cause on the large and heavy tail. Instead, he proposes that the tails might have been used as a tactile organ to keep in touch with the individuals behind and on the sides in a group while migrating, which could have augmented cohesion and allowed communication among individuals while limiting more energetically demanding activities like stopping to search for dispersed individuals, turning to visually check on individuals behind, or communicating vocally.

Paleoecology
The Morrison Formation is a sequence of shallow marine and alluvial sediments which, according to radiometric dating, dates from between 156.3mya at its base, and 146.8mya at the top, placing it in the late Oxfordian, Kimmeridgian, and early Tithonian stages of the Late Jurassic period. This formation is interpreted as originating in a locally semiarid environment with distinct wet and dry seasons. The Morrison Basin, where dinosaurs lived, stretched from New Mexico to Alberta and Saskatchewan; it was formed when the precursors to the Front Range of the Rocky Mountains started pushing up to the west. The deposits from their east-facing drainage basins were carried by streams and rivers and deposited in swampy lowlands, lakes, river channels, and floodplains. This formation is similar in age to the Lourinhã Formation in Portugal and the Tendaguru Formation in Tanzania.

Apatosaurus was the second most common sauropod in the Morrison Formation ecosystem, after Camarasaurus. Apatosaurus may have been more solitary than other Morrison Formation dinosaurs. Fossils of the genus have only been found in the upper levels of the formation. Those of Apatosaurus ajax are known exclusively from the upper Brushy Basin Member, about 152–151 mya. A.louisae fossils are rare, known only from one site in the upper Brushy Basin Member; they date to the late Kimmeridgian stage, about 151mya. Additional Apatosaurus remains are known from similarly aged or slightly younger rocks, but they have not been identified as any particular species, and thus may instead belong to Brontosaurus.

The Morrison Formation records a time when the local environment was dominated by gigantic sauropod dinosaurs. Dinosaurs known from the Morrison Formation include the theropods Allosaurus, Ceratosaurus, Ornitholestes, Saurophaganax, and Torvosaurus; the sauropods Brontosaurus, Brachiosaurus, Camarasaurus, and Diplodocus; and the ornithischians Camptosaurus, Dryosaurus, and Stegosaurus. Apatosaurus is commonly found at the same sites as Allosaurus, Camarasaurus, Diplodocus, and Stegosaurus. Allosaurus accounted for 70–75% of theropod specimens and was at the top trophic level of the Morrison food web. Many of the dinosaurs of the Morrison Formation are of the same genera as those seen in Portuguese rocks of the Lourinhã Formation – mainly Allosaurus, Ceratosaurus, and Torvosaurus – or have a close counterpart – Brachiosaurus and Lusotitan, Camptosaurus and Draconyx, and Apatosaurus and Dinheirosaurus. Other vertebrates that are known to have shared this paleo-environment include ray-finned fishes, frogs, salamanders, turtles, sphenodonts, lizards, terrestrial and aquatic crocodylomorphs, and several species of pterosaur. Shells of bivalves and aquatic snails are also common. The flora of the period has been evidenced in fossils of green algae, fungi, mosses, horsetails, cycads, ginkgoes, and several families of conifers. Vegetation varied from river-lining forests of tree ferns with fern understory (gallery forests), to fern savannas with occasional trees such as the Araucaria-like conifer Brachyphyllum.

title: Apatosaurus