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Cloudinidae

The cloudinids, an early metazoan family containing the genera Acuticocloudina, Cloudina and Conotubus, lived in the late Ediacaran period about 550 million years ago. and became extinct at the base of the Cambrian. They formed millimetre-scale conical fossils consisting of calcareous cones nested within one another; the appearance of the organism itself remains unknown. The name Cloudina honors the 20th-century geologist and paleontologist Preston Cloud.

Cloudinids comprise two genera: Cloudina itself is mineralized, whereas Conotubus is at best weakly mineralized, whilst sharing the same "funnel-in-funnel" construction.

Cloudinids had a wide geographic range, reflected in the present distribution of localities in which their fossils are found, and are an abundant component of some deposits. They never appear in the same layers as soft-bodied Ediacaran biota, but the fact that some sequences contain cloudinids and Ediacaran biota in alternating layers suggests that these groups had different environmental preferences. It has been suggested that cloudinids lived embedded in microbial mats, growing new cones to avoid being buried by silt. However no specimens have been found embedded in mats, and their mode of life is still an unresolved question.

The classification of the cloudinids has proved difficult: they were initially regarded as polychaete worms, and then as coral-like cnidarians on the basis of what look like buds on some specimens. Current scientific opinion is divided between classifying them as polychaetes and regarding it as unsafe to classify them as members of any broader grouping. In 2020, a new study of pyritized specimens from the Wood Canyon Formation in Nevada showed the presence of Nephrozoan type guts, the oldest on record, supporting the bilaterian interpretation.

Cloudinids are important in the history of animal evolution for two reasons. They are among the earliest and most abundant of the small shelly fossils with mineralized skeletons, and therefore feature in the debate about why such skeletons first appeared in the Late Ediacaran. The most widely supported answer is that their shells are a defense against predators, as some Cloudina specimens from China bear the marks of multiple attacks, which suggests they survived at least a few of them. The holes made by predators are approximately proportional to the size of the Cloudina specimens, and Sinotubulites fossils, which are often found in the same beds, have so far shown no such holes. These two points suggest that predators attacked in a selective manner, and the evolutionary arms race which this indicates is commonly cited as a cause of the Cambrian explosion of animal diversity and complexity.

Morphology
Cloudina varies in size from a diameter of 0.3 to 6.5 mm, and 8 to 150 mm in length. Fossils consist of a series of stacked vase-like calcite tubes, whose original mineral composition is unknown, but inferred to be high-magnesium calcite. Each cone traps a significant pore space beneath it, and stacks eccentrically in the one below. This results in a ridged external appearance. The overall tube is curved or sinuous, and occasionally branches. The tube walls are 8 to 50 micrometers thick, usually lying in the range 10 to 25 μm. Although it used to be thought that the tubes had test-tube like bases, detailed three-dimensional reconstruction has shown that the tubes had an open base. There is evidence that the tube was flexible.

Classification
Cloudina was originally classified in 1972 as a member of the Cribricyathea, a class known from the Early Cambrian. Glaessner (1976) accepted this classification and also proposed that Cloudina was similar to the annelid worms, particularly serpulid polychaetes. However, Hahn & Pflug (1985) and Conway Morris et al.. (1990) doubted both Germs' and Glaessner's suggested relationships, and were unwilling to classify it to anything more than its own family, Cloudinidae. Some specimens of Cloudina hartmannae display budding, which implies asexual reproduction. On this basis Grant (1990) classified Cloudina as a coral-like cnidarian. Since the tubes had an open base, creating a single living space rather than a series of separate chambers, Cloudina is more likely to be a stem group polychaete worm, in other words an evolutionary "aunt" or "cousin" of more recent polychaetes. This interpretation is reinforced by the even distribution of bore-holes made by predators. However, as with so many Ediacaran life forms, there is great debate surrounding its position in the tree of life, and classification between the kingdom and family level may be unwise.

Ecology
Cloudina is frequently found in association with stromatolites, which are limited to shallow water; their isotopic composition suggests that water temperatures were relatively cool. They have also been found in normal sea-floor sediments, suggesting that they were not only restricted to dwelling on microbial mounds. On the other hand, Cloudina has never been found in the same layers as the soft-bodied Ediacara biota, but Cloudina and Ediacara biota have been found in alternating layers. This suggests that the two groups of organisms had different environmental preferences.

In many Cloudina specimens the ridges formed by the cones are of varying width, which suggests the organisms grew at a variable rate. Adolf Seilacher suggests that they adhered to microbial mats, and that the growth phases represented the organism keeping pace with sedimentation—growing through new material deposited on it that would otherwise bury it. Kinks in the developing tube are easily explained by the mat falling slightly from the horizontal. Because of its small size, Cloudina would be expected to be found in situ in the microbial mat, especially if, as Seilacher suggests, sedimentation built up around it during its lifetime. But all the many specimens discovered to date have only been found having been washed out of their places of growth. A further argument against Seilacher's hypothesis is that the predatory borings found in many specimens are not concentrated at what would be the top end, as one would expect if the animal was mainly buried. An alternative is that the organism dwelt on seaweeds, but until a specimen unquestionably in situ is discovered, its mode of life remains open to debate.

The tubes often appear to form colonies, although they are sometimes found in more isolated situations. The frequent appearance of large and sometimes single-species colonies has been attributed to the lack of significant predation. On the other hand, in some locations up to 20% of Cloudina fossils contain predatory borings ranging from 15 to 400 μm in diameter. The boreholes are rather evenly distributed along the tube length, and some tubes had been bored multiple times—hence the organism could survive attacks, since predators do not attack empty shells. This may indicate that the animal could vary its position in the tube in response to predation, or that it occupied the full length—but not the full width—of the tube. The even distribution is perhaps difficult to reconcile with an infaunal lifestyle, mainly buried in a microbial mat, and adds weight to Miller's suggestion that the animal lived on seaweeds or in a reef environment. If modern-day molluscs are a suitable analogy, the size distribution of the borings suggests that the predator was similar in size to Cloudina.

Fossil findings in the Nama Group, Namibia, suggest that Cloudina was one of the first reef-building animals, but machine-learning facilitated 3D tomography indicates that the 'reef-forming' fossils are in fact simply aggregations of solitary individuals.

Fossil locations
Cloudina occurred in calcium carbonate rich areas of stromatolite reefs. It is found in association with Namacalathus, which like Cloudina was "weakly skeletal" and solitary, and Namapoikia, which was "robustly skeletal" and formed sheets on open surfaces.

First found in the Nama Group in Namibia, Cloudina has also been reported in Oman, China's Dengying Formation, Canada, Uruguay, Argentina, Antarctica, Brazil, Nevada, central Spain, northwest Mexico and California, in west and south Siberia. The Cloudina fossils found in association with late Precambrian-Early Cambrian anabaritids SSF and tubular agglutinated skeletal fossils Platysolenites and Spirosolenites in Siberia.

Paleontological importance
Although not the first small shelly fossil to be found, Cloudina is one of the earliest and most abundant. The evolution of external shells in the Late Ediacaran is thought to be a defence against predators, marking the start of an evolutionary arms race. While predatory borings are common in Cloudina specimens, no such borings have been found in Sinotubulites, a similar shelly fossil sometimes found in the same beds. In addition, the diameters of borings in Cloudina are proportional to the sizes of specimens, which suggests that predators were selective about the size of their prey. These two indications that predators attacked selectively suggest the possibility of speciation in response to predation, which is often postulated as a potential cause of the rapid diversification of animals in the Early Cambrian.

title: Cloudinidae


text:
Conodont

Conodonts (Greek kōnos, "cone", + odont, "tooth") are an extinct group of eel-looking agnathan (jawless) vertebrates, classified in the class Conodonta. For many years, they were known only from fossils of their spiky oral elements, which are usually found in isolation and are now called conodont elements, while knowledge about soft tissues remains limited. A resilient group of prehistoric fish, conodonts existed in the world's oceans for over 300 million years, from the Cambrian to the beginning of the Jurassic. Due to their cosmopolitan distribution, conodont elements are widely used as index fossils, fossils used to define and identify geological periods.

Discovery and understanding of conodonts
The teeth-like fossils of the conodont were first discovered by Heinz Christian Pander and the results published in Saint Petersburg, Russia, in 1856.

It was only in the early 1980s that the first fossil evidence of the rest of the animal was found (see below). In the 1990s exquisite fossils were found in South Africa in which the soft tissue had been converted to clay, preserving even muscle fibres. The presence of muscles for rotating the eyes showed definitively that the animals were primitive vertebrates.

Nomenclature and taxonomic rank
Through their history of study, "conodont" is a term which has been applied to both the individual fossils and to the animals to which they belonged. The original German term used by Pander was "conodonten", which was subsequently anglicized as "conodonts", though no formal latinized name was provided for several decades. MacFarlane (1923) described them as an order, Conodontes (a Greek translation), which Huddle (1934) altered to the Latin spelling Conodonta. A few years earlier, Eichenberg (1930) established another name for the animals responsible for conodont fossils: Conodontophorida ("conodont bearers"). A few other scientific names were rarely and inconsistently applied to conodonts and their proposed close relatives during 20th century, such as Conodontophoridia, Conodontophora, Conodontochordata, Conodontiformes, and Conodontomorpha.

Conodonta and Conodontophorida are by far the most common scientific names used to refer to conodonts, though inconsistencies regarding their taxonomic rank still persist. Bengtson (1976)'s research on conodont evolution identified three morphological tiers of early conodont-like fossils: protoconodonts, paraconodonts, and "true conodonts" (euconodonts). Further investigations revealed that protoconodonts were probably more closely related to chaetognaths (arrow worms) rather than true conodonts. On the other hand, paraconodonts are still considered a likely ancestral stock or sister group to euconodonts.

The 1981 Treatise on Invertebrate Paleontology volume on the conodonts (Part W revised, supplement 2) lists Conodonta as the name of both a phylum and a class, with Conodontophorida as a subordinate order for "true conodonts". All three ranks were attributed to Eichenberg, and Paraconodontida was also included as an order under Conodonta. This approach was criticized by Fåhraeus (1983), who argued that it overlooked Pander's historical relevance as a founder and primary figure in conodontology. Fåhraeus proposed to retain Conodonta as a phylum (attributed to Pander), with the single class Conodontata (Pander) and the single order Conodontophorida (Eichenberg). Subsequent authors continued to regard Conodonta as a phylum with an ever-increasing number of subgroups.

With increasingly strong evidence that conodonts lie within the phylum Chordata, more recent studies generally refer to "true conodonts" as the class Conodonta, containing multiple smaller orders. Paraconodonts are typically excluded from the group, though still regarded as close relatives. In practice, Conodonta, Conodontophorida, and Euconodonta are equivalent terms and are used interchangeably.

Lone elements
Conodont elements consist of mineralised teeth-like structures of varying morphology and complexity. The evolution of mineralized tissues has been puzzling for more than a century. It has been hypothesized that the first mechanism of chordate tissue mineralization began either in the oral skeleton of conodonts or the dermal skeleton of early agnathans.

The element array constituted a feeding apparatus that is radically different from the jaws of modern animals. They are now termed "conodont elements" to avoid confusion. The three forms of teeth, i.e., coniform cones, ramiform bars, and pectiniform platforms, probably performed different functions.

For many years, conodonts were known only from enigmatic tooth-like microfossils (200 micrometers to 5 millimeters in length ), which occur commonly, but not always, in isolation and were not associated with any other fossil. Until the early 1980s, conodont teeth had not been found in association with fossils of the host organism, in a konservat lagerstätte. This is because the conodont animal was soft-bodied, thus everything but the teeth was unsuited for preservation under normal circumstances.

These microfossils are made of hydroxylapatite (a phosphatic mineral). The conodont elements can be extracted from rock using adequate solvents.

They are widely used in biostratigraphy. Conodont elements are also used as paleothermometers, a proxy for thermal alteration in the host rock, because under higher temperatures, the phosphate undergoes predictable and permanent color changes, measured with the conodont alteration index. This has made them useful for petroleum exploration where they are known, in rocks dating from the Cambrian to the Late Triassic.

Full apparatus
The conodont apparatus may comprise a number of discrete elements, including the spathognathiform, ozarkodiniform, trichonodelliform, neoprioniodiform, and other forms.

In the 1930s, the concept of conodont assemblages was described by Hermann Schmidt and by Harold W. Scott in 1934.

Elements of ozarkodinids
The feeding apparatus of ozarkodinids is composed of an axial Sa element at the front, flanked by two groups of four close-set elongate Sb and Sc elements which were inclined obliquely inwards and forwards. Above these elements lay a pair of arched and inward pointing (makellate) M elements. Behind the S-M array lay transversely oriented and bilaterally opposed (pectiniform, i.e. comb-shaped) Pb and Pa elements.

The conodont animal
Although conodont elements are abundant in the fossil record, fossils preserving soft tissues of conodont animals are known from only a few deposits in the world. One of the first possible body fossils of a conodont were those of Typhloesus, an enigmatic animal known from the Bear Gulch limestone in Montana. This possible identification was based on the presence of conodont elements with the fossils of Typhloesus. This claim was disproved, however, as the conodont elements were actually in the creature's digestive area. That animal is now regarded as a possible mollusk related to gastropods. As of 2023, there are only three described species of conodonts that have preserved trunk fossils: Clydagnathus windsorensis from the Carboniferous aged Granton Shrimp Bed in Scotland, Promissum pulchrum from the Ordovician aged Soom Shale in South Africa, and Panderodus unicostatus from the Silurian aged Waukesha Biota in Wisconsin. There are other examples of conodont animals that only preserve the head region, including eyes, of the animals known from the Silurian aged Eramosa site in Ontario and Triassic aged Akkamori section in Japan.

According to these fossils, conodonts had large eyes, fins with fin rays, chevron-shaped muscles and axial line, which were interpreted as notochord or the dorsal nerve cord. While Clydagnathus and Panderodus had lengths only reaching 4-5 cm, Promissum is estimated to reach 40 cm in length, if it had the same proportions as Clydagnathus.

Ecology
The "teeth" of some conodonts have been interpreted as filter-feeding apparatuses, filtering plankton from the water and passing it down the throat. Others have been interpreted as a "grasping and crushing array". Wear on some conodont elements suggests that they functioned like teeth, with both wear marks likely created by food as well as by occlusion with other elements. Studies have concluded that conodonts taxa occupied both pelagic (open ocean) and nektobenthic (swimming above the sediment surface) niches. The preserved musculature suggests that some conodonts (Promissum at least) were efficient cruisers, but incapable of bursts of speed. Based on isotopic evidence, some Devonian conodonts have been proposed to have been low-level consumers that fed on zooplankton.

A study on the population dynamics of Alternognathus has been published. Among other things, it demonstrates that at least this taxon had short lifespans lasting around a month. A study Sr/Ca and Ba/Ca ratios of a population of conodonts from a carbonate platform from the Silurian of Sweden found that the different conodont species and genera likely occupied different trophic niches.

Some species of the genus Panderodus have been speculated to be venomous, based on grooves found on some elements.

Affinities
, scientists classify the conodonts in the phylum Chordata on the basis of their fins with fin rays, chevron-shaped muscles and notochord.

Milsom and Rigby envision them as vertebrates similar in appearance to modern hagfish and lampreys, and phylogenetic analysis suggests they are more derived than either of these groups. However, this analysis comes with one caveat: the earliest conodont-like fossils, the protoconodonts, appear to form a distinct clade from the later paraconodonts and euconodonts. Protoconodonts are probably not relatives of true conodonts, but likely represent a stem group to Chaetognatha, an unrelated phylum that includes arrow worms.

Moreover, some analyses do not regard conodonts as either vertebrates or craniates, because they lack the main characteristics of these groups. More recently it has been proposed that conodonts may be stem-cyclostomes, more closely related to hagfish and lampreys than to jawed vertebrates.

Ingroup relations
Individual conodont elements are difficult to classify in a consistent manner, but an increasing number of conodont species are now known from multi-element assemblages, which offer more data to infer how different conodont lineages are related to each other. The following is a simplified cladogram based on Sweet and Donoghue (2001), which summarized previous work by Sweet (1988) and Donoghue et al. (2000):

Only a few studies approach the question of conodont ingroup relationships from a cladistic perspective, as informed by phylogenetic analyses. One of the broadest studies of this nature was the analysis of Donoghue et al. (2008), which focused on "complex" conodonts (Prioniodontida and other descendant groups):

Evolutionary history
The earliest fossils of conodonts are known from the Cambrian period. Conodonts extensively diversified during the early Ordovician, reaching their apex of diversity during the middle part of the period, and experienced a sharp decline during the late Ordovician and Silurian, before reaching another peak of diversity during the mid-late Devonian. Conodont diversity declined during the Carboniferous, with an extinction event at the end of the middle Tournaisian and a prolonged period of significant loss of diversity during the Pennsylvanian. Only a handful of conodont genera were present during the Permian, though diversity increased after the P-T extinction during the Early Triassic.

Diversity continued to decline during the Middle and Late Triassic, culminating in their extinction soon after the Triassic-Jurassic boundary. Much of their diversity during the Paleozoic was likely controlled by sea levels and temperature, with the major declines during the Late Ordovician and Late Carboniferous due to cooler temperatures, especially glacial events and associated marine regressions which reduced continental shelf area. However, their final demise is more likely related to biotic interactions, perhaps competition with new Mesozoic taxa.

Taxonomy
Conodonta taxonomy based on Sweet (1988), Sweet & Donoghue (2001), and Mikko's Phylogeny Archive.
 * Class Conodonta Pander, 1856 [Conodontophorida Eichenberg, 1930; "euconodonts" Bengtson, 1976 ]
 * Cavidonti Sweet, 1988
 * Order Belodellida? Sweet, 1988
 * Ansellidae? Fåhraeus & Hunter, 1985
 * Belodellidae Khodalevich & Tschernich, 1973
 * Dapsilodontidae? Sweet, 1988
 * Order Proconodontida Sweet, 1988
 * Cordylodontidae Lindström, 1970
 * Fryxellodontidae Miller, 1981
 * Pseudooneotodidae? Wang & Aldridge, 2010
 * Proconodontidae Lindström, 1970
 * Pygodontidae? Bergstrom, 1981
 * Conodonti Pander, 1856 non Branson, 1938
 * Order Protopanderodontida Sweet, 1988 [Panderodontida Sweet, 1988 ]
 * Acanthodontidae Lindström, 1970
 * Clavohamulidae Lindström, 1970
 * Drepanoistodontidae? Fåhraeus, 1978 [Distacodontidae Bassler, 1925 ]
 * Panderodontidae Lindström, 1970
 * Protopanderodontidae Lindström, 1970 [Scolopodontidae Bergström, 1981 ; Oneotodontidae Miller, 1981 ; Teridontidae Miller, 1981 ]
 * Serratognathidae? Zhen et al., 2009
 * Strachanognathidae? Bergström, 1981 [Cornuodontidae Fåhraeus, 1966 ]
 * Order Prioniodontida Dzik, 1976 (paraphyletic)
 * Acodontidae? Dzik, 1993 [Tripodontinae Sweet, 1988 ]
 * Cahabagnathidae? Stouge & Bagnoli 1999
 * Distacodontidae? Bassler, 1925 emend. Ulrich & Bassler, 1926 [Drepanodontinae Fåhraeus & Nowlan, 1978 ; Lonchodininae Hass, 1959 ]
 * Gamachignathidae? Wang & Aldridge, 2010
 * Jablonnodontidae? Dzik, 2006
 * Nurrellidae? Pomešano-Cherchi, 1967
 * Paracordylodontidae? Bergström, 1981
 * Playfordiidae? Dzik, 2002
 * Ulrichodinidae? Bergström, 1981
 * Rossodus Repetski & Ethington, 1983
 * Multioistodontidae Harris, 1964 [Dischidognathidae]
 * Oistodontidae Lindström, 1970 [Juanognathidae Bergström, 1981 ]
 * Periodontidae Lindström, 1970
 * Rhipidognathidae Lindström, 1970 sensu Sweet, 1988
 * Prioniodontidae Bassler, 1925
 * Phragmodontidae Bergström, 1981 [Cyrtoniodontinae Hass, 1959 ]
 * Plectodinidae Sweet, 1988
 * Pygodontidae? Bergstrom, 1981
 * Icriodontacea
 * Balognathidae (Hass, 1959)
 * Polyplacognathidae Bergström, 1981
 * Distomodontidae Klapper, 1981
 * Icriodellidae Sweet, 1988
 * Icriodontidae Müller & Müller, 1957
 * Order Prioniodinida Sweet, 1988
 * Oepikodontidae? Bergström, 1981
 * Xaniognathidae? Sweet, 1981
 * Chirognathidae Branson & Mehl, 1944
 * Prioniodinidae Bassler, 1925 [Hibbardellidae Mueller, 1956 ]
 * Bactrognathidae Lindström, 1970
 * Ellisoniidae Clark, 1972
 * Gondolellidae Lindström, 1970
 * Order Ozarkodinida Dzik, 1976 [Polygnathida]
 * Anchignathodontidae? Clark, 1972
 * Archeognathidae? Miller, 1969
 * Belodontidae? Huddle, 1934
 * Coleodontidae? Branson & Mehl, 1944 [Hibbardellidae Müller, 1956 ; Loxodontidae]
 * Eognathodontidae? Bardashev, Weddige & Ziegler, 2002
 * Francodinidae? Dzik, 2006
 * Gladigondolellidae? (Hirsch, 1994) [Sephardiellinae Plasencia, Hirsch & Márquez-Aliaga, 2007 ; Neogondolellinae Hirsch, 1994 ; Cornudininae Orchard, 2005 ; Epigondolellinae Orchard, 2005 ; Marquezellinae Plasencia et al., 2018 ; Paragondolellinae Orchard, 2005 ; Pseudofurnishiidae Ramovs, 1977 ]
 * Iowagnathidae? Liu et al., 2017
 * Novispathodontidae? (Orchard, 2005)
 * Trucherognathidae? Branson & Mehl, 1944
 * Vjalovognathidae? Shen, Yuan & Henderson, 2015
 * Wapitiodontidae? Orchard, 2005
 * Cryptotaxidae Klapper & Philip, 1971
 * Spathognathodontidae Hass, 1959 [ Ozarkodinidae Dzik, 1976 ]
 * Pterospathodontidae Cooper, 1977 [Carniodontidae]
 * Kockelellidae Klapper, 1981 [Caenodontontidae]
 * Polygnathidae Bassler, 1925 [?Eopolygnathidae Bardashev, Weddige & Ziegler, 2002 ]
 * Palmatolepidae Sweet, 1988
 * Hindeodontidae (Hass, 1959)
 * Elictognathidae Austin & Rhodes, 1981
 * Gnathodontidae Sweet, 1988
 * Idiognathodontidae Harris & Hollingsworth, 1933
 * Mestognathidae Austin & Rhodes, 1981
 * Cavusgnathidae Austin & Rhodes, 1981
 * Sweetognathidae Ritter, 1986

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

title: Conodont


text:
Gnathostomulid

Gnathostomulids, or jaw worms, are a small phylum of nearly microscopic marine animals. They inhabit sand and mud beneath shallow coastal waters and can survive in relatively anoxic environments. They were first recognised and described in 1956.

Anatomy
Most gnathostomulids measure 0.5 to 1 mm in length. They are often slender to thread-like worms, with a generally transparent body. In many Bursovaginoidea, one of the major group of gnathostomulids, the neck region is slightly narrower than the rest of the body, giving them a distinct head.

Like flatworms they have a ciliated epidermis, but in contrast to flatworms, they have one cilium per cell. The cilia allow the worms to glide along in the water between sand grains, although they also use muscles, allowing the body to twist or contract, for movement.

They have no body cavity, and no circulatory or respiratory system. The nervous system is simple, and restricted to the outer layers of the body wall. The only sense organs are modified cilia, which are especially common in the head region.

The mouth is located just behind the head, after a rostrum, on the underside of the body. It has a pair of cuticular jaws, supplied by strong muscles, and often bearing minute teeth. A "basal plate" on the lower surface that bears a comb-like structure is also present. The basal plate is used to scrape smaller organisms off of the grains of sand that make up their anoxic seabed mud habitat. This bilaterally symmetrical pharynx with its complex cuticular mouth parts make them appear closely related to rotifers and their allies, together making up the Gnathifera. The ultrastructure of the jaws made of rods with electron dense core in transmission electron microscopy sections also support their close relation with Rotifera and Micrognathozoa. The mouth opens into a blind-ending tube in which digestion takes place; there is no true anus. However, there is tissue connecting the intestine to the epidermis which may serve as an anal pore.

Reproduction
Gnathostomulids are simultaneous hermaphrodites. Each individual possesses a single ovary and one or two testes. After fertilization, the single egg ruptures through the body wall and adheres to nearby sand particles; the parent is able to rapidly heal the resulting wound. The egg hatches into a miniature version of the adult, without a larval stage.

Taxonomy
There are approximately 100 described species and certainly many more as yet undescribed. The known species are grouped in two orders. The filospermoids are very long and are characterized by an elongate rostrum. The bursovaginoids have paired sensory organs and are characterized by the presence of a penis and a sperm-storage organ called a bursa.

Gnathostomulids have no known fossil record, though there are (debatable) similarities between the jaws of modern gnathostomulids and certain conodont elements. (Ochietti & Cailleux, 1969; Durden et al, 1969)

They appear to be a sister clade to the Syndermata.

title: Gnathostomulid


text:
Stanley Jordan

Stanley Jordan (born July 31, 1959) is an American jazz guitarist noted for his playing technique, which involves tapping his fingers on the fretboard of the guitar with both hands.

Music career
Jordan was born in Chicago, Illinois, United States. When he was six, he started on piano, then at eleven switched to guitar. He later began playing in rock and soul bands. In 1976, he won an award at the Reno Jazz Festival. At Princeton University, he studied music theory and composition with Milton Babbitt and computer music with Paul Lansky. He also took freshman calculus with Edward Nelson. While at Princeton he played with Benny Carter and Dizzy Gillespie.

In 1985, Bruce Lundvall became president of Blue Note Records and Stanley Jordan was the first person he signed. Blue Note released his album Magic Touch, which sat at No.1 on Billboard's jazz chart for 51 weeks, setting a record.

Touch technique
Normally, a guitarist uses two hands to play each note. One hand presses down a guitar string behind a chosen fret to prepare the note, and the other hand either plucks or strums the string to play that note. Jordan's touch technique is an advanced form of two-handed tapping. The guitarist produces a note using only one finger by quickly tapping (or hammering) his finger down behind the appropriate fret. The impact causes the string to vibrate enough to sound the note, and the volume can be controlled by varying the force of impact. Jordan taps with both hands, and more legato than is normally associated with guitar tapping. His technique allows the guitarist to play melody and chords simultaneously. It is also possible, as he has demonstrated, to play simultaneously on two different guitars, as well as guitar and piano.

He plays guitar in all-fourths tuning, from bass to treble EADGCF (all in perfect fourths as on the bass guitar) rather than the standard EADGBE. He has stated that all-fourths tuning "simplifies the fingerboard, making it logical".

Jordan's main guitar was built by Vigier Guitars in 1984: it is an Arpege model on which Vigier made a flat fingerboard, allowing it to have a very low action (0.5/0.7mm). The low action facilitates the tapping technique.

Recording
Among the artists Jordan has worked with are Quincy Jones, Stanley Clarke, Onaje Allan Gumbs, Michal Urbaniak, Richie Cole, The Dave Matthews Band, The String Cheese Incident, Phil Lesh, Moe, and Umphrey's McGee.

He has performed at many jazz festivals, including Kool Jazz Festival (1984), Concord Jazz Festival (1985), and the Montreux International Jazz Festival (1985).

In 2004, he released the album Dreams of Peace with the Italian band Novecento. The album was produced by Lino Nicolosi and Pino Nicolosi at Nicolosi Productions and was released in the U.S. on Favored Nations. He signed with Mack Avenue Records and released State of Nature in 2008 and Friends in 2011. The latter was nominated for an NAACP Image Award. He has four Grammy nominations. Jordan made the startup sound for the Macintosh computer models the Power Macintosh 6100, Power Macintosh 7100, and Power Macintosh 8100.

Film and television
Jordan made a cameo appearance in the movie Blind Date (1987). In 1995 he wrote the score for the short film One Red Rose. In 1996 he wrote the score for the ABC TV afternoon special, Daddy's Girl.

Since the mid-1980s he has performed on numerous television shows, including The Tonight Show with Johnny Carson, The David Letterman Show and the Grammy Awards.

Personal life
Stanley Jordan was briefly married and has one daughter, Julia Jordan, who is a singer and songwriter.

In the 2024 United States presidential election, Jordan supported author Marianne Williamson for president "because she's bringing politics into the 21st-century".

As leader

 * Touch Sensitive (Tangent, 1982)
 * Magic Touch (Blue Note, 1985)
 * Standards Vol. 1 (Blue Note, 1986)
 * Flying Home (EMI-Manhattan, 1988)
 * Cornucopia (Blue Note, 1990)
 * Stolen Moments (Blue Note, 1991)
 * Bolero (Arista, 1994)
 * Live in New York (Blue Note, 1998)
 * Dreams of Peace (Nicolosi, 2003)
 * Relaxing Music for Difficult Situations I (Manifold Music, 2003)
 * State of Nature (Mack Avenue, 2008)
 * New Morning: The Paris Concert (Inakustik, 2008)
 * Friends (Mack Avenue, 2011)
 * Duets with Kevin Eubanks (Mack Avenue, 2015)

As sideman

 * Muriel Anderson & Phil Keaggy, Uncut Gems (CGD Music, 2003)
 * Muriel Anderson, Wildcat (Heartstrings Attached Music, 2005)
 * Burt Bacharach, Blue Note Plays Burt Bacharach (Blue Note, 2004)
 * Anthony Branker, For the Children (RPC, 1980)
 * Dennis Chambers, Groove and More (Soul Trade, 2013)
 * Stanley Clarke, Hideaway (Epic, 1986)
 * Billy Cobham, Drum 'n' Voice Vol. 4 (Nicolosi, 2016)
 * Stu Gardner, Presents Total Happiness: Music from the Bill Cosby Show Vol. II (Columbia, 1987)
 * Rebbie Jackson, R U Tuff Enuff (Columbia, 1988)
 * Charnett Moffett, Net Man (Blue Note, 1987)
 * Charnett Moffett, Treasure (Motema, 2010)
 * Charnett Moffett, Music from Our Soul (Motema, 2017)
 * Novecento, Secret (Nicolosi, 2008)
 * Kenny Rogers, The Heart of the Matter (RCA, 1985)
 * Dionne Warwick, Sings Cole Porter (Arista, 1990)

title: Stanley Jordan


text:
Hyolitha

Hyoliths are animals with small conical shells, known from fossils from the Palaeozoic era. They are at least considered as being lophotrochozoan, and possibly being lophophorates, a group which includes the brachiopods, while others consider them as being basal lophotrochozoans, or even molluscs.

Morphology
The shell of a hyolith is typically one to four centimeters in length, triangular or elliptical in cross section. Some species have rings or stripes. It comprises two parts: the main conical shell (previously referred to as a ‘conch’) and a cap-like operculum. Some also had two curved supports known as helens They are calcareous – probably aragonitic All of these structures grew by marginal accretion.

Shell microstructure
The orthothecid shell has an internal layer with a microstructure of transverse bundles, and an external layer comprising longitudinal bundles.

Helens
Some hyoliths had helens, long structures that taper as they coil gently in a logarithmic spiral in a ventral direction. The helens had an organic-rich central core surrounded by concentric laminae of calcite. They grew by the addition of new material at their base, on the cavity side, leaving growth lines.

They were originally described by Walcott as separate fossils under the genus name Helenia, (Walcott's wife was named Helena and his daughter Helen); Bruce Runnegar adopted the name helen when they were recognized as part of the hyolith organism. Encrusting organisms have been found on helens, and also on both sides of the main shell, all of which are therefore supposed to have been raised above the sea bed. The helens have been interpreted as props that supported the feeding organ, the lophophore, above the sea bed.

Operculum
The operculum closes over the aperture of the shell, leaving (in hyolithids) two gaps through which the helens can protrude. It comprises two parts: the cardinal shield, a flat region at the top of the shell; and the conical shield, the bottom part, which is more conical. The inside of the shell bears a number of protrusions, notably the dorsal cardinal processes and the radially-arranged clavicles.

Soft tissues
The soft tissues of the mid-Cambrian hyolith Haplophrentis, from the Burgess Shale and Spence Shale Lagerstätten include a gullwing-shaped band below the operculum. This band is interpreted as a lophophore, a feeding organ with a central mouth; it bears 12 to 16 tentacles. From the mouth a muscular pharynx leads to a gut, which loops back and exits beyond the crown of tentacles. Next to the gut are a pair of large kidney-shaped organs of uncertain nature. Under the operculum are muscles. The thin body wall circumscribes the interior of the shell, except the apex. Preserved intestines have been described from the Ordovician hyolith Girvanolithes thraivensis.

Taxonomy
The hyoliths are divided into two orders, the Hyolithida and the Orthothecida.

Hyolitha have dorso-ventrally differentiated opercula, with the ventral surface of the shell extending forwards to form a shelf termed the ligula.

The Orthothecida are somewhat more problematic, and probably contain a number of non-hyoliths simply because they are so difficult to identify with confidence, especially if their operculum is absent. They have a straight (planar) opening, sometimes with a notch on the bottom side, and sealed with an operculum that has no ligula, clavicles, furrow or rooflets.

Hyptiotheca is an unusual hyolithid, in that it lacks clavicles.

Orthothecids fall into two groups: one, the orthothecida sensu stricto, is kidney or heart shaped in cross-section due to a longitudinal groove on its ventral surface, and its opercula bear cardinal processes; the other has a rounded cross-section and often lacks cardinal processes, making them difficult to distinguish from other cornet-shaped calcareous organisms. All were sessile and benthic; some may have been filter feeders.

Phylogenetic position
Because hyoliths are extinct and do not obviously resemble any extant group, it has long been unclear which living group they are most closely related to. They have been supposed to be molluscs; or to belong to their own phylum in an unspecified part of the tree of life. Their grade of organization was historically considered to be of the 'mollusc-annelid-sipunculid' level, consistent with a Lophotrochozoan affinity, and comparison was primarily drawn with the molluscs or sipunculids. Older studies (predating the Lophotrochozoan concept) consider hyoliths to represent a stem lineage of the clade containing (Mollusca + Annelida + Arthropoda).

A secure classification at last became possible in 2017, on the basis of Burgess Shale specimens that preserve lophophores. This diagnostic characteristic demonstrates an affinity with the Lophophorata, a group that contains Brachiopoda, Bryozoa (perhaps), and Phoronida.

A study in 2019 estimated that hyoliths are more likely to be basal members of the lophotrochozoans rather than lophophorates. Meanwhile, a study in 2020 instead concluded that hyoliths belong to Mollusca, as did a different study in 2022.

Ecology
Hyolithids were benthic (bottom-dwellers), using their helens as stilts to hold the opening of their shells above the sea floor. Orthothecids did not have helens, but are presumed to have been sessile and benthic.

In the Cambrian, their global distribution shows no sign of provinciality, suggesting a long-lived planktonic larval life stage (reflected by their protoconchs); but by the Ordovician distinct assemblages were becoming evident.

Some orthothecids are preserved in vertical [life] orientation, suggesting a sessile suspension-feeding habit; hyolithids tend to be flat on the bottom, and their shape and the occurrence of epibionts are consistent with a sessile suspension feeding habit via orientation relative to passive currents.

Occurrence
The first hyolith fossils appeared about in the Purella antiqua Zone of the Nemakit-Daldynian Stage of Siberia and in its analogue the Paragloborilus subglobosus–Purella squamulosa Zone of the Meishucunian Stage of China. Hyolith abundance and diversity attain a maximum in the Cambrian, followed by a progressive decline up to their Permian extinction.

Similar organisms
Due to the simple shape of their shell, hyoliths have been something of a wastebasket taxon, and organisms originally interpreted as hyoliths have sometimes later been recognized as something else – as for example in the case of the cnidarian-like Glossolites and Palaeoconotuba.

title: Hyolitha


text:
Lobopodia

Lobopodians are members of the informal group Lobopodia (from the Greek, meaning "blunt feet"), or the formally erected phylum Lobopoda Cavalier-Smith (1998). They are panarthropods with stubby legs called lobopods, a term which may also be used as a common name of this group as well. While the definition of lobopodians may differ between literatures, it usually refers to a group of soft-bodied, marine worm-like fossil panarthropods such as Aysheaia and Hallucigenia.

The oldest near-complete fossil lobopodians date to the Lower Cambrian; some are also known from Ordovician, Silurian and Carboniferous Lagerstätten. Some bear toughened claws, plates or spines, which are commonly preserved as carbonaceous or mineralized microfossils in Cambrian strata. The grouping is considered to be paraphyletic, as the three living panarthropod groups (Arthropoda, Tardigrada and Onychophora) are thought to have evolved from lobopodian ancestors.

Definitions

The Lobopodian concept varies from author to author. Its most general sense refers to a suite of mainly Cambrian worm-like panarthropod taxa possessing lobopods – for example, Aysheaia, Hallucigenia, and Xenusion – which were traditionally united as "Xenusians" or "Xenusiids" (class Xenusia). Certain Dinocaridid genera, such as Opabinia, Pambdelurion, and Kerygmachela, may also be regarded as lobopodians, sometimes referred to more specifically as "gilled lobopodians" or "gilled lobopods". This traditional, informal usage of "Lobopodia" treats it as an evolutionary grade, including only extinct Panarthropods near the base of crown Panarthropoda. Crown Panarthropoda comprises the three extant Panarthropod phyla – Onychophora (velvet worms), Tardigrada (waterbears), and Arthropoda (arthropods) – as well as their most recent common ancestor and all of its descendants. Thus, in this usage, Lobopodia consists of various basal Panarthropods. This corresponds to "A" in the image to the left.

An alternative, broader definition of Lobopodia would also incorporate Onychophora and Tardigrada, the two living panarthropod phyla which still bear lobopodous limbs. This definition, corresponding to "C", is a morphological one, depending on the superficial similarity of appendages (the "lobopods"). Thus, it is paraphyletic, excluding the Euarthropods, which are descendants of certain Lobopodians, on the basis of their highly divergent limb morphology. "Lobopodia" has also been used to refer to a proposed sister clade to Arthropoda, consisting of the extant Onychophora and Tardigrada, as well as their most recent common ancestor and all of its descendants. This definition renders Lobopodia a monophyletic taxon, if indeed it is valid (that is, if Tardigrades and Onychophora are closer to one another than either is to Arthropoda), but would exclude all the Euarthropod-line taxa traditionally considered Lobopodians. Its validity is uncertain, however, as there are a number of hypotheses regarding the internal phylogeny of Panarthropoda. The broadest definition treats Lobopodia as a monophyletic superphylum equivalent in circumscription to Panarthropoda. By this definition, represented by "D" in the image, Lobopodia is no longer treated as an evolutionary grade but as a clade, containing not only the early, superficially "Lobopodian" forms but also all of their descendants, including the extant Panarthropods.

Lobopodia has, historically, sometimes included Pentastomida, a group of parasitic panarthropod which were traditionally thought to be a unique phylum, but revealed by subsequent phylogenomic and anatomical studies to be a highly specialized taxon of crustaceans.

Representative taxa
The better-known genera include Aysheaia, which was discovered in the Canadian Burgess Shale, and Hallucigenia, known from both the Chenjiang Maotianshan Shale and the Burgess Shale. Aysheaia pedunculata has a morphology apparently basic for lobopodians — for example, a significantly annulated cuticle, a terminal mouth opening, specialized frontalmost appendages, and stubby lobopods with terminal claws. Hallucigenia sparsa is famous for having a complex history of interpretation — it was originally reconstructed with long, stilt-like legs and mysterious fleshy dorsal protuberances, and was long considered a prime example of the way in which nature experimented with the most diverse and bizarre body designs during the Cambrian. However, further discoveries showed that this reconstruction had placed the animal upside-down: interpreting the "stilts" as dorsal spines made it clear that the fleshy "dorsal" protuberances were actually elongated lobopods. More recent reconstruction even exchanged the front and rear ends of the animal: it was revealed that the bulbous imprint previously thought to be a head was actually gut contents being expelled from the anus.

Microdictyon is another charismatic as well as the speciose genus of lobopodians resembling Hallucigenia, but instead of spines, it bore pairs of net-like plates, which are often found disarticulated and are known as an example of small shelly fossils (SSF). Xenusion has the oldest fossil record amongst the described lobopodians, which may trace back to Cambrian Stage 2. Luolishania is an iconic example of lobopodians with multiple pairs of specialized appendages. The gill lobopodians Kerygmachela and Pambdelurion shed light on the relationship between lobopodians and arthropods, as they have both lobopodian affinities and characteristics linked to the arthropod stem-group.

Morphology

Most lobopodians were only a few centimeters in length, while some genera grew up to over 20 centimeters. Their bodies are annulated, although the presence of annulation may differ between position or taxa, and sometimes difficult to discern due to their close spacing and low relief on the fossil materials. Body and appendages are circular in cross-section.

Head
Due to the usually poor preservation, detailed reconstructions of the head region are only available for a handful of lobopodian species. The head of a lobopodian is more or less bulbous, and sometime possesses a pair of pre-ocular, presumely protocerebral appendages – for example, primary antennae or well-developed frontal appendages,  which are individualized from the trunk lobopods (with the exception of Antennacanthopodia, which have two pairs of head appendages instead of one ). Mouthparts may consist of rows of teeth or a conical proboscis. The eyes may be represented by a single ocellus or by numerous pairs of simple ocelli, as has been shown in Luolishania (=Miraluolishania ), Ovatiovermis, Onychodictyon, Hallucigenia, Facivermis, and less certainly Aysheaia as well. However, in gilled lobopodians like Kerygmachela, the eyes are relatively complex reflective patches that may had been compound in nature.

Trunk and lobopods
The trunk is elongated and composed of numerous body segments (somites), each bearing a pair of legs called lobopods or lobopodous limbs. The segmental boundaries are not as externally significant as those of arthropods, although they are indicated by heteronomous annulations (i.e., the alternation of annulation density corresponding to the position of segmental boundaries) in some species. The trunk segments may bear other external, segment-corresponding structures such as nodes (e.g. Hadranax, Kerygmachela ), papillae (e.g. Onychodictyon ), spine/plate-like sclerites (e.g. armoured lobopodians ) or lateral flaps (e.g. gilled lobopodians ). The trunk may terminate with a pair of lobopods (e.g. Aysheaia, Hallucigenia sparsa) or a tail-like extension (e.g. Paucipodia, Siberion, Jianshanopodia).

The lobopods are flexible and loosely conical in shape, tapering from the body to tips that may or may not  bear claws. The claws, if present, are hardened structures with a shape resembling a hook or gently-curved spine. Claw-bearing lobopods usually have two claws, but single claws are known (e.g. posterior lobopods of luolishaniids  ), as are more than two (e.g. three in Tritonychus, seven in Aysheaia ) depending on its segmental or taxonomical association. In some genera, the lobopods bear additional structures such as spines (e.g. Diania ), fleshy outgrowths (e.g. Onychodictyon ), or tubercules (e.g. Jianshanopodia ). There is no sign of arthropodization (development of a hardened exoskeleton and segmental division on panarthropod appendages) in known members of lobopodians, even for those belonging to the arthropod stem-group (e.g. gilled lobopodians and siberiids), and the suspected case of arthropodization on the limbs of Diania is considered to be a misinterpretation.

Differentiation (tagmosis) between trunk somites barely occurs, except in hallucigenids and luolishaniids, where numerous pairs of their anterior lobopods are significantly slender (hallucigenids) or setose (luolishaniids) in contrast to their posterior counterparts.

Internal structures

The gut of lobopodians is often straight, undifferentiated, and sometimes preserved in the fossil record in three dimensions. In some specimens the gut is found to be filled with sediment. The gut consists of a central tube occupying the full length of the lobopodian's trunk, which does not change much in width - at least not systematically. However, in some groups, specifically the gilled lobopodians and siberiids, the gut is surrounded by pairs of serially repeated, kidney-shaped gut diverticulae (digestive glands). In some specimens, parts of the lobopodian gut can be preserved in three dimensions. This cannot result from phosphatisation, which is usually responsible for 3-D gut preservation, because the phosphate content of the guts is under 1%; the contents comprise quartz and muscovite. The gut of the representative Paucipodia is variable in width, being widest at the centre of the body. Its position in the body cavity is only loosely fixed, so flexibility is possible.

Not much is known about the neural anatomy of lobopodians due to the spare and mostly ambiguous fossil evidence. Possible traces of a nervous system were found in Paucipodia, Megadictyon and Antennacanthopodia. The first and so far the only confirmed evidence of lobopodian neural structures comes from the gilled lobopodian Kerygmachela in Park et al. 2018 — it presents a brain composed of only a protocerebrum (the frontal-most cerebral ganglion of panarthropods) that is directly connected to the nerves of eyes and frontal appendages, suggesting the protocerebral ancestry of the head of lobopodians as well as the whole Panarthropoda.

In some extant ecdysozoan such as priapulids and onychophorans, there is a layer of outermost circular muscles and a layer of innermost longitudinal muscles. The onychophorans also have a third, intermediate, layer of interwoven oblique muscles. Musculature of the gilled lobopodian Pambdelurion shows a similar anatomy, but that of the lobopodian Tritonychus shows the opposite pattern: it is the outermost muscles that are longitudinal and the innermost layer that consists of circular muscles.

Categories
Based on external morphology, lobopdians may fall under different categories — for example the general worm-like taxa as "xenusiid" or "xenusian"; xenusiid with sclerite as "armoured lobopodians"; and taxa with both robust frontal appendages and lateral flaps as "gilled lobopodians". Some of them were originally defined under a taxonomic sense (e.g. class Xenusia), but neither any of them are generally accepted as monophyletic in further studies.

Armoured lobopodians
Armoured lobopodians referred to xenusiid lobopodians which bore repeated sclerites such as spine or plates on their trunk (e.g. Hallucigenia, Microdictyon, Luolishania) or lobopods (e.g. Diania). In contrast, lobopodians without sclerites may be referred to as "unarmoured lobopodians". Function of the sclerites were interpreted as protective armor and/or muscle attachment points. In some cases, only the disarticulated sclerites of the animal were preserved, which represented as component of small shelly fossils (SSF). Armoured lobopodians were suggest to be onychophoran-related and may even represent a clade in some previous studies, but their phylogenetic positions in later studies are controversial. (see text)

Gilled lobopodians

Dinocaridids with lobopodian affinities (due to shared features like annulation and lobopods) are referred to as "gilled lobopodians"  or "gilled lobopods". These forms sport a pair of flaps on each trunk segment, but otherwise no signs of arthropodization, in contrast to more derived dinocaridids like the Radiodonta that have robust and sclerotized frontal appendages. Gilled lobopodians cover at least four genera: Pambdelurion, Kerygmachela, Utahnax and Mobulavermis. Opabinia may also fall under this category in a broader sense, although the presence of lobopods in this genus is not definitively proven. Omnidens, a genus known only from a Pambdelurion-like mouth apparatus, may also be a gilled lobopodian. The body flaps may have functioned as both swimming appendages and gills, and are possibly homologous to the dorsal flaps of radiodonts and exites of Euarthropoda. Whether these genera were true lobopodians is still contested by some. However, they are widely accepted as stem-group arthropods just basal to radiodonts.

Siberion and similar taxa

Siberion, Megadictyon and Jianshanopodia may be grouped as siberiids (order Siberiida), jianshanopodians or "giant lobopodians" by some literatures. They are generally large — body length ranging between 7 and 22 centimeters (2¼ to 8⅔ inches) — xenusiid lobopodians with widen trunk, stout trunk lobopods without evidence of claws, and most notably a pair of robust frontal appendages. With the possible exception of Siberion, they also have digestive glands like those of a gilled lobopodian and basal euarthropod. Their anatomy represent transitional forms between typical xenusiids and gilled lobopodians, eventually placing them under the basalmost position of arthropod stem-group.

Paleoecology
Lobopodians possibly occupied a wide range of ecological niches. Although most of them had undifferentiated appendages and straight gut, which would suggest a simple sediment-feeding lifestyle, sophisticated digestive glands and large size of gilled lobopodians and siberiids would allow them to consume larger food items, and their robust frontal appendages may even suggest a predatory lifestyle. On the other hand, luolishaniids such as Luolishania and Ovatiovermis have elaborate feather-like lobopods that presumably formed 'baskets' for suspension or filter-feeding. Lobopods with curved terminal claws may have given some lobopodians the ability to climb on substrances.

Not much is known about the physiology of lobopodians. There is evidence to suggest that lobopodians moult just like other ecdysozoan taxa, but the outline and ornamentation of the harden sclerite did not vary during ontogeny. The gill-like structures on the body flaps of gilled lobopodians and ramified extensions on the lobopods of Jianshanopodia may provide respiratory function (gills). Pambdelurion may control the movement of their lobopods in a way similar to onychophorans.

Distribution
During the Cambrian, lobopodians displayed a substantial degree of biodiversity. One species is known from each of the Ordovician and Silurian periods, with a few more known from the Carboniferous (Mazon Creek) — this represents the paucity of exceptional lagerstatten in post-Cambrian deposits.

Phylogeny
The overall phylogenetic interpretation on lobopodians has changed dramatically since their discovery and first description. The reassignments are not only based on new fossil evidence, but also new embryological, neuroanatomical, and genomic (e.g. gene expression, phylogenomics) information observed from extant panarthropod taxa.

Based on their apparently onychophoran-like morphology (e.g. annulated cuticle, lobopodous appendage with claws), lobopodians were originally thought to be present a group of paleozoic onychophorans. This interpretation was challenged after the discovery of lobopodians with arthropod and tardigrade-like characteristics, suggesting that the similarity between lobopodians and onychophorans represents deeper panarthropod ancestral traits (plesiomorphies) instead of onychophoran-exclusive characteristics (synapomorphies). For example, The British palaeontologist Graham Budd sees the Lobopodia as representing a basal grade from which the phyla Onychophora and Arthropoda arose, with Aysheaia comparable to the ancestral plan, and with forms like Kerygmachela and Pambdelurion representing a transition that, via the dinocaridids, would lead to an arthropod body plan. Aysheaia's surface ornamentation, if homologous with palaeoscolecid sclerites, may represent a deeper link connecting it with cycloneuralian outgroups. Many further studies followed and extended the idea, generally in agreement that all three panarthropod phyla have lobopodians in their stem lineages. Lobopodians are thus paraphyletic, and include the last common ancestor of arthropods, onychophorans and tardigrades.

Stem-group arthropods
Compared to other panarthropod stem-groups, suggestion on the lobopodian members of arthropod stem-group is relatively consistent — siberiid like Megadictyon and Jianshanopodia occupied the basalmost position, gilled lobopodians Pambdelurion and Kerygmachela branch next, and finally lead to a clade compose of Opabinia, Radiodonta and Euarthropoda (crown-group arthropods). Their positions within arthropod stem-group are indicated by numerous arthropod groundplans and intermediate forms (e.g. arthropod-like digestive glands, radiodont-like frontal appendages and dorso-ventral appendicular structures link to arthropod biramous appendages). Lobopodian ancestry of arthropods also reinforced by genomic studies on extant taxa — gene expression support the homology between arthropod appendages and onychophoran lobopods, suggests that modern less-segmented arthropodized appendages evolved from annulated lobopodous limbs. On the other hand, primary antennae and frontal appendages of lobopodians and dinocaridids may be homologous to the labrum/hypostome complex of euarthropods, an idea support by their protocerebral origin  and developmental pattern of the labrum of extant arthropods.

Diania, a genus of armoured lobopodian with stout and spiny legs, were originally thought to be associated within the arthropod stem-group based on its apparently arthropod-like (arthropodized) trunk appendages. However, this interpretation is questionable as the data provided by the original description are not consistent with the suspected phylogenic relationships. Further re-examination even revealed that the suspected arthropodization on the legs of Diania was a misinterpretation — although the spine may have hardened, the remaining cuticle of Diania 's legs were soft (not harden nor scleritzed), lacking any evidence of pivot joint and arthrodial membrane, suggest the legs are lobopods with only widely spaced annulations. Thus, the re-examination eventually reject the evidence of arthropodization (sclerotization, segmentation and articulation) on the appendages as well as the fundamental relationship between Diania and arthropods.

Stem-group onychophorans

While Antennacanthopodia is widely accepted as a stem-group onychophoran,    the position of other xenusiid genera that were previously thought to be onychophoran-related is controversial — in further studies, most of them were either suggested to be stem-group onychophorans   or basal panarthropods, with a few species (Aysheaia   or Onychodictyon ferox ) occasionally suggested to be stem-group tardigrades. A study in 2014 suggested that Hallucigenia are stem-group onychophorans based on their claws, which have overlapped internal structures resembling those of an extant onychophoran. This interpretation was questioned by later studies, as the structures may be a panarthropod plesiomorphy.

Stem-group tardigrades

Lobopodian taxa of the tardigrade stem-group is unclear. Aysheaia  or Onychodictyon ferox had been suggest to be a possible member, based on the high claw number (in Aysheaia) and/or terminal lobopods with anterior-facing claws  (in both taxa). Although not widely accepted, there are even suggestions that Tardigrada itself representing the basalmost panarthropod or branch between the arthropod stem-group. However, a paper in 2023 found luolishaniids to be the closest relatives of tardigrades using various morphological characteristics.

Stem-group panarthropods
It is unclear that which lobopodians represent members of the panarthropod stem-group, which were branched just before the last common ancestor of extant panarthropod phyla. Aysheaia may have occupied this position based on its apparently basic morphology;  while other studies rather suggest luolishaniid and hallucigenid,   two lobopodian taxa which had been resolved as members of stem-group onychophorans as well.

Described genera

As of 2018, over 20 lobopodian genera have been described. The fossil materials being described as lobopodians Mureropodia apae and Aysheaia prolata are considered to be disarticulated frontal appendages of the radiodonts Caryosyntrips and Stanleycaris, respectively. Miraluolishania was suggested to be synonym of Luolishania by some studies. The enigmatic Facivermis was later revealed to be a highly specialized genus of luolishaniid lobopodians.

 * Antennacanthopodia
 * Aysheaia
 * Carbotubulus
 * Cardiodictyon
 * Collinsium
 * Collinsovermis
 * Diania
 * Entothyreos
 * Facivermis
 * Fusuconcharium
 * Hadranax
 * Hallucigenia
 * Jianshanopodia
 * Kerygmachela
 * Lenisambulatrix
 * Luolishania (=Miraluolishania)
 * Megadictyon
 * Microdictyon
 * Mobulavermis
 * Omnidens?
 * Onychodictyon
 * Orstenotubulus
 * Ovatiovermis
 * Pambdelurion
 * Parvibellus?
 * Paucipodia
 * Quadratapora
 * Siberion
 * Thanahita
 * Tritonychus
 * Utahnax
 * Xenusion

title: Lobopodia


text:
Archaeocyatha

Archaeocyatha (, 'ancient cups') is a taxon of extinct, sessile, reef-building marine sponges that lived in warm tropical and subtropical waters during the Cambrian Period. It is believed that the centre of the Archaeocyatha origin is now located in East Siberia, where they are first known from the beginning of the Tommotian Age of the Cambrian, 525 million years ago (mya). In other regions of the world, they appeared much later, during the Atdabanian, and quickly diversified into over a hundred families.

They became the planet's first reef-building animals and are an index fossil for the Lower Cambrian worldwide.

Preservation
The remains of Archaeocyatha are mostly preserved as carbonate structures in a limestone matrix. This means that the fossils cannot be chemically or mechanically isolated, save for some specimens that have already eroded out of their matrices, and their morphology has to be determined from thin cuts of the stone in which they were preserved.

Geological history
Today, the archaeocyathan families are recognizable by small but consistent differences in their fossilized structures: Some archaeocyathans were built like nested bowls, while others were as long as 300mm. Some archaeocyaths were solitary organisms, while others formed colonies. In the beginning of the Toyonian Age around 516 mya, the archaeocyaths went into a sharp decline. Almost all species became extinct by the Middle Cambrian, with the final-known species, Antarcticocyathus webberi, disappearing just prior to the end of the Cambrian period. Their rapid decline and disappearance coincided with a rapid diversification of the Demosponges.

The archaeocyathids were important reef-builders in the early to middle Cambrian, with reefs (and indeed any accumulation of carbonates) becoming very rare after the group's extinction until the diversification of new taxa of coral reef-builders in the Ordovician.

Antarcticocyathus  was considered the only late Cambrian archaeocyath, but its reinterpretation as a lithisid sponge means that there are now no archaeocyaths post the mid-Cambrian.

Morphology
The typical archaeocyathid resembled a hollow horn coral. Each had a conical or vase-shaped porous skeleton of calcite similar to that of a sponge. The structure appeared like a pair of perforated, nested ice cream cones. Their skeletons consisted of either a single porous wall (Monocyathida), or more commonly as two concentric porous walls, an inner and outer wall separated by a space. Inside the inner wall was a cavity (like the inside of an ice cream cup). At the base, these pleosponges were held to the substrate by a holdfast. The body presumably occupied the space between the inner and outer shells (the intervallum).

Ecology

Flow tank experiments suggest that archaeocyathan morphology allowed them to exploit flow gradients, either by passively pumping water through the skeleton, or, as in present-day, extant sponges, by drawing water through the pores, removing nutrients, and expelling spent water and wastes through the pores into the central space.

The size of the pores places a limit on the size of plankton that archaeocyaths could have consumed; different species had different sized pores, the largest large enough to conceivably consume mesozooplankton, possibly giving rise to different ecological niches within a single reef.

Distribution
The archaeocyathans inhabited coastal areas of shallow seas. Their widespread distribution over almost the entire Cambrian world, as well as the taxonomic diversity of the species, might be explained by surmising that, like true sponges, they had a planktonic larval stage that enabled their wide spread.

Taxonomy
Their phylogenetic affiliation has been subject to changing interpretations, yet the consensus is growing that the archaeocyath was indeed a kind of sponge, thus sometimes called a pleosponge. But some invertebrate paleontologists have placed them in an extinct, separate phylum, known appropriately as the Archaeocyatha. However, one cladistic analysis suggests that Archaeocyatha is a clade nested within the phylum Porifera (better known as the true sponges).

True archaeocyathans coexisted with other enigmatic sponge-like animals. Radiocyatha and Cribricyatha were two diverse Cambrian classes comparable to Archaeocyatha, alongside genera such as Boyarinovicyathus, Proarchaeocyathus, Acanthinocyathus, and Osadchiites.

The clade Archaeocyatha have traditionally been divided into Regulares and Irregulares (Rowland, 2001):

 * Hetairacyathida (incertae sedis)
 * Regulares
 * Monocyathida
 * Capsulocyathida
 * Ajacicyathida
 * Irregulares
 * Thalassocyathida
 * Archaeocyathida
 * Kazakhstanicyathida

However, Okulitch (1955), who at the time regarded the archaeocyathans as outside of Porifera, divided the phylum in three classes:

 * Phylum Archaeocyatha Vologdin, 1937
 * Class Monocyathea Okulitch, 1943
 * Class Archaeocyathea Okulitch, 1943
 * Class Anthocyathea Okulitch, 1943

title: Archaeocyatha


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Lophophorata

The Lophophorata or Tentaculata are a Lophotrochozoan clade consisting of the Brachiozoa and the Bryozoa. They have a lophophore. Molecular phylogenetic analyses suggest that lophophorates are protostomes, but on morphological grounds they have been assessed as deuterostomes. Fossil finds of the "tommotiid" Wufengella suggest that they evolved from worm-like animals that resembled annelids.

title: Lophophorata


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Phyla

Phyla, the plural of phylum, may refer to:

 * Phylum, a biological taxon between Kingdom and Class
 * by analogy, in linguistics, a large division of possibly related languages, or a major language family which is not subordinate to another

Phyla, as a singular, may refer to:

 * Phyla (genus), a genus of plants in the family Verbenaceae
 * Phyla-Vell, a Marvel Comics superhero

title: Phyla


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Talk:Battle of Berestechko

Old Stuff (section title added 1/9/2012)
128.etx.etx where did you get numbers for Polish army? in all historic books there is written that Polish army had 57.000 soldiers, period. I read one article by some Ukrainian, who added to that number taken from air number of 100.000 noble servants.

Second, why did you remove working links? This is wikipedia. The more links, the better.

Third, why you impose usage of Ukrainian names? We should stick to standard english usage and i guess you will find a lot more about battle of Beresteczko in English than Berestechko, unless i am mistaken.

fourth, maybe you would consider making account on wikipedia. THis is simple - just log in and mark "make new account". That way you will have your own talk page, you could sign your responses with simple three tildas (like this szopen <- i sign \~\~\~ ), which i guess could be useful in future, since you, i think, you are one of first Ukrainians on wikipedia, so i guess we will meet many times in discussions (which is good, because out of heat of discussion articles get more NPOV szopen

images
There are too many images in this article, the third one doesn't even really fit. I propose we remove the one at the bottom. Ostap 07:15, 17 January 2008 (UTC)
 * The images are rather relevant, I'd rather see the article expanded to accommodate them.--Piotr Konieczny aka Prokonsul Piotrus 18:09, 17 January 2008 (UTC)
 * I guess that does sound better than just deleting. Ostap 18:59, 17 January 2008 (UTC)

Question to Salaga
Can you give sources to the number of Polish troops that you provided ? Shiden (talk) 15:40, 28 January 2008 (UTC)

Significant unsourced changes
Polish casualties went from 7000 to 500. This needs to be sourced. Ostap 22:08, 7 February 2008 (UTC)

Now it's sourced. Regards Shiden (talk) 17:23, 8 February 2008 (UTC)
 * Thank you for the quick response. Ostap 02:35, 9 February 2008 (UTC)
 * You're welcome Shiden (talk) 15:44, 9 February 2008 (UTC)
 * ХУИТА. Only Polish sources are welcome? —Preceding unsigned comment added by 91.200.181.154 (talk) 18:01, 17 February 2009 (UTC)

Memoirs
Were there memoirs of  Ukrainian commanders who fought in that battle ? Regards Shiden (talk) 16:38, 10 February 2008 (UTC)

Samuel Twardowski's poem
The Polish poem is clearly in public domain, but can anyone confirm that the cited English translation is? --Piotr Konieczny aka Prokonsul Piotrus| reply here 12:16, 12 February 2014 (UTC)

External links modified
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A Commons file used on this page or its Wikidata item has been nominated for speedy deletion
The following Wikimedia Commons file used on this page or its Wikidata item has been nominated for speedy deletion: You can see the reason for deletion at the file description page linked above. —Community Tech bot (talk) 21:53, 14 January 2023 (UTC)
 * Berest1.jpg

Significant usourced changes
why Polish casualties went so high??? 37.47.173.38 (talk) 18:42, 6 December 2023 (UTC)

The numbers?????
where are this numbers of Polish forces from??? 37.47.173.38 (talk) 18:45, 6 December 2023 (UTC)

title: Talk:Battle of Berestechko


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Tonic (music)

In music, the tonic is the first scale degree of the diatonic scale (the first note of a scale) and the tonal center or final resolution tone that is commonly used in the final cadence in tonal (musical key-based) classical music, popular music, and traditional music. In the movable do solfège system, the tonic note is sung as do. More generally, the tonic is the note upon which all other notes of a piece are hierarchically referenced. Scales are named after their tonics: for instance, the tonic of the C major scale is the note C.

The triad formed on the tonic note, the tonic chord, is thus the most significant chord in these styles of music. In Roman numeral analysis, the tonic chord is typically symbolized by the Roman numeral "I" if it is major and by "i" if it is minor.

"In very much conventionally tonal music, harmonic analysis will reveal a broad prevalence of the primary (often triadic) harmonies: tonic, dominant, and subdominant (i.e., I and its chief auxiliaries a 5th removed), and especially the first two of these."

- Berry (1976)

These chords may also appear as seventh chords: in major, as IM7, or in minor as i7 or rarely iM7: ""

The tonic is distinguished from the root, which is the reference note of a chord, rather than that of the scale.

Importance and function
In music of the common practice period, the tonic center was the most important of all the different tone centers which a composer used in a piece of music, with most pieces beginning and ending on the tonic, usually modulating to the dominant (the fifth scale degree above the tonic, or the fourth below it) in between.

Two parallel keys have the same tonic. For example, in both C major and C minor, the tonic is C. However, relative keys (two different scales that share a key signature) have different tonics. For example, C major and A minor share a key signature that feature no sharps or flats, despite having different tonic pitches (C and A, respectively).

The term tonic may be reserved exclusively for use in tonal contexts while tonal center or pitch center may be used in post-tonal and atonal music: "For purposes of non-tonal centric music, it might be a good idea to have the term 'tone center' refer to the more general class of which 'tonics' (or tone centers in tonal contexts) could be regarded as a subclass." Thus, a pitch center may function referentially or contextually in an atonal context, often acting as an axis or line of symmetry in an interval cycle. The term pitch centricity was coined by Arthur Berger in his "Problems of Pitch Organization in Stravinsky". According to Walter Piston, "the idea of a unified classical tonality replaced by nonclassical (in this case nondominant) centricity in a composition is perfectly demonstrated by Debussy's Prélude à l'après-midi d'un faune".

The tonic includes four separate activities or roles as the principal goal tone, initiating event, generator of other tones, and the stable center neutralizing the tension between dominant and subdominant.

title: Tonic (music)


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Mesozoa

The Mesozoa are minuscule, worm-like parasites of marine invertebrates. Generally, these tiny, elusive creatures consist of a somatoderm (outer layer) of ciliated cells surrounding one or more reproductive cells.

A 2017 study recovered Mesozoa as a monophyletic group that emerged in the Lophotrochozoa as sister of the Rouphozoa.

Some workers previously classified Mesozoa as the sole phylum of the lonely subkingdom Agnotozoa. Cavalier-Smith argued that at least some of the mesozoans are in fact protistans, not animals.

In the 19th century, the Mesozoa were a wastebasket taxon for multicellular organisms which lacked the invaginating gastrula which was thought to define the Metazoa.

Evolution
Mesozoa were once thought to be evolutionary intermediate forms between Protozoans and Metazoans, but now they are thought to be degenerate or simplified metazoa. Their ciliated larvae are similar to the miracidium of trematodes, and their internal multiplication is similar to what happens in the sporocysts of trematodes. Mesozoan DNA has a low GC-content (40%). This amount is similar to ciliates, but ciliates tend to be binucleate. Others relate mesozoa to a group including annelids, planarians and nemerteans.

Orthonectida have a very reduced muscular and nervous system, only consisting of a few cells, but so far no muscle cells or neurons have been found in Dicyemida.

Groupings
The two main mesozoan groups are the Dicyemida and the Orthonectida. Other groups sometimes included in the Mesozoa are the Placozoa and the Monoblastozoa.

Monoblastozoans consist of a single description written in the 19th century of a species that has not been seen since. As such, many workers doubt that they are a real group. As described, the animal had only a single layer of tissue.

Rhombozoan mesozoans
Rhombozoa, or dicyemid mesozoans, are found in the nephrid tracts of squid and octopuses. They range from a few millimeters long with twenty to thirty cells that include anterior attachment cells and a long central reproductive cell called an axial cell. This axial cell may develop asexually into vermiform juveniles or it may produce eggs and sperm that self-fertilize to produce a ciliated infusiform larva.

There are three genera: Dicyema, Pseudicyema and Dicyemennea.

Molecular evidence suggests that this phylum are derived from the Lophotrochozoa.

Orthonectid mesozoans
Orthonectida are found in the body spaces of various marine invertebrates including tissue spaces, gonads, genitorespiratory bursae. This pathogen causes host castration of different species.

The best known of Orthonectida is the parasite of brittle stars. The multinucleate syncytial stage lives within tissues and spaces of the gonad but can spread into arms. It causes the destruction of starfish ovary and eggs to cause castration (the male gonads are usually unaffected). The stages of the plasmodium develop into more plasmodia by simple fragmentation; at some point, they decide to go sexual. The syncytia are dioecious (either male or female), but young syncytia can fuse to produce both male and female. The males are ciliated and smaller than the females. The females and the males leave the starfish and mate in the sea. Tailed sperm enters the female and fertilizes the numerous oocytes. Each oocyst produces a small ciliated larva which makes its way to another star.

The genome of one of these species – Intoshia linei – has been sequenced. The Orthonectids may be degenerate annelid worms.

title: Mesozoa


text:
Talk:Bohdan Khmelnytsky

100,000 death toll
If it's included, it should be clarified that it is not the consensus among historians, per WP:UNDUE. This is all I have to say. Synotia (moan) 16:27, 28 February 2023 (UTC)

 * Then present a source that says: it is not the consensus among historians and include it - GizzyCatBella  🍁  16:52, 28 February 2023 (UTC)
 * It would be more correct to ask for a source that asserts it is the consensus.
 * If I want, I can claim that Khmelnytsky was bisexual and had 3 testicles. Find me a source that says it is not the consensus. Good luck with that.
 * Further above on this talk page someone wrote this for instance: modern research dedicated to the issue of Jewish casualties supports the 20-30k numbers, but older, more general publications, quoting old research, gives those larger, less realistic numbers.
 * To begin with, recent Jewish sources assert that in the areas affected by the uprising there were not 100,000 Jews to start with. Here for example: It seems that at the beginning of 1648, there were about 40,000 Jews in the affected regions.
 * If you have access to Jstor: This article by the Israeli historian Shaul Stampfer, in the section "The Jewish population on the eve of 1648" in which he quotes a fellow Jew, Maurycy Horn. Horn asserted that in the area there were 45,000 Jews residing in towns and 9,000 in villages. Synotia (moan) 17:13, 28 February 2023 (UTC)
 * Then add that: It is very difficult to determine the totals of Jewish casualties in the years 1648–1649 or something along these lines but don’t remove other sources and info. -  GizzyCatBella  🍁  17:21, 28 February 2023 (UTC)
 * I've done that in the past, but the ref note makes it all weird and inconsistent. Something would need to be done to bridge the "gap". Synotia (moan) 17:25, 28 February 2023 (UTC)

It looks like various editors still keep putting random numbers in the article that are completely unrelated to the sources presented in this or other articles. It seems like outright vandalism, and perhaps a full protection for the article is in order. Any comments are appreciated. —Ynhockey (Talk) 23:42, 5 August 2023 (UTC)

Semi-protected edit request on 3 July 2023
Change "During the uprising the Cossacks led a massacre of thousands of Jewish people during 1648–1649" to "During the uprising the Cossacks led a massacre of dozens thousands of Jewish people during 1648–1649" Saying thousand belittles the slaughter, and supports many anti-semetic and neo nazi people who claim the number of murdered Jews was in the thousands and not dozens of thousands, during this slaughter Jewish babies were boiled alive and their mothers were forced to eat them. This is a horrible side of history that must be remembered and not belittled so people would understand the evil of extremism. Big-pini (talk) 09:06, 3 July 2023 (UTC)
 * Red information icon with gradient background.svg Not done: please provide reliable sources that support the change you want to be made. Lightoil (talk) 12:25, 3 July 2023 (UTC)

Move to : Bohdan Chmielnicki
Why not to move to Bohdan Chmielnicki? born in Poland, suzerein of Poland, so there is already his name in Latin alphabet, there is no necessary of cyrylic transliteration, especially already in 1911 Britannica that was in use 83.23.8.118 (talk) 19:54, 25 December 2023 (UTC)
 * Oppose: There is a consensus of English language sources that support the use the current article name.  // Timothy :: talk  22:22, 25 December 2023 (UTC)
 * @TimothyBlue there is no consensus, again there is already Britannica version from 1911, and many more of it. There is no need for Romanization from artificially created named in Cyril if he was a Polish subject and Poland use Latin alphabet. 83.23.8.118 (talk) 22:27, 25 December 2023 (UTC)

title: Talk:Bohdan Khmelnytsky


text:
Nematomorpha

Nematomorpha (sometimes called Gordiacea, and commonly known as horsehair worms, hairsnakes,  or Gordian worms) are a phylum of parasitoid animals superficially similar to nematode worms in morphology, hence the name. Most species range in size from 50 to 100 mm, reaching 2 m in extreme cases, and 1 to 3 mm in diameter. Horsehair worms can be discovered in damp areas, such as watering troughs, swimming pools, streams, puddles, and cisterns. The adult worms are free-living, but the larvae are parasitic on arthropods, such as beetles, cockroaches, mantises, orthopterans, and crustaceans. About 351 freshwater species are known and a conservative estimate suggests that there may be about 2000 freshwater species worldwide. The name "Gordian" stems from the legendary Gordian knot. This relates to the fact that nematomorphs often coil themselves in tight balls that resemble knots.

Description and biology
Nematomorphs possess an external cuticle without cilia. Internally, they have only longitudinal muscle and a non-functional gut, with no excretory, respiratory or circulatory systems. The nervous system consists of a nerve ring near the anterior end of the animal, and a ventral nerve cord running along the body.

Reproductively, they have two distinct sexes, with the internal fertilization of eggs that are then laid in gelatinous strings. Adults have cylindrical gonads, opening into the cloaca. The larvae have rings of cuticular hooks and terminal stylets that are believed to be used to enter the hosts. Once inside the host, the larvae live inside the haemocoel and absorb nutrients directly through their skin. Development into the adult form takes weeks or months, and the larva moults several times as it grows in size.

The adults are mostly free-living in freshwater or marine environments, and males and females aggregate into tight balls (Gordian knots) during mating.

In Spinochordodes tellinii and Paragordius tricuspidatus, which have grasshoppers and crickets as their hosts, the infection acts on the infected host's brain. This causes the host insect to seek water and drown itself, thus returning the nematomorph to water. P. tricuspidatus is also remarkably able to survive the predation of their host, being able to wiggle out of the predator that has eaten the host. The nematomorpha parasite affects host Hierodula patellifera's light-interpreting organs so the host is attracted to horizontally polarized light. Thus the host goes into water and the parasite's lifecycle completes. Many of the genes the parasites use for manipulating their host have been acquired through horizontal gene transfer from the host genome.

There are a few cases of accidental parasitism in vertebrate hosts, including dogs and humans. Several cases involving Parachordodes, Paragordius, or Gordius have been recorded in human hosts in Japan and China.

Community ecology
Owing to their use of orthopterans as hosts, nematomorphs can be significant factors in shaping community ecology. One study conducted in a Japanese riparian ecosystem showed that nematomorphs can cause orthopterans to become 20 times more likely to enter water than non-infected orthopterans; these orthopterans constituted up to 60% of the annual energy intake for the Kirikuchi char. Absence of nematomorphs from riparian communities can thus lead to char predating more heavily on other aquatic invertebrates, potentially causing more widespread physiological effects.

Taxonomy
Nematomorphs can be confused with nematodes, particularly mermithid worms. Unlike nematomorphs, mermithids do not have a terminal cloaca. Male mermithids have one or two spicules just before the end apart from having a thinner, smoother cuticle, without areoles and a paler brown colour.

The phylum is placed along with the Ecdysozoa clade of moulting organisms that include the Arthropoda. Their closest relatives are the nematodes. The two phyla make up the group Nematoida in the clade Cycloneuralia. During the larval stage, the animals show a resemblance to adult kinorhyncha and some species of Loricifera and Priapulida, all members of the group Scalidophora. The earliest Nematomorph could be Maotianshania, from the Lower Cambrian; this organism is, however, very different from extant species; fossilized worms resembling the modern forms have been reported from mid Cretaceous Burmese amber dated to 100 million years ago.

Relationships within the phylum are still somewhat unclear, but two classes are recognised. The five marine species of nematomorph are contained in Nectonematoida. This order is monotypic containing the genus Nectonema Verrill, 1879 : adults are planktonic and the larvae parasitise decapod crustaceans, especially crabs. They are characterized by a double row of natotory setae along each side of the body, dorsal and ventral longitudinal epidermal cords, a spacious and fluid-filled blastocoelom and singular gonads.

The approximately 320 remaining species are distributed between two families, within the monotypic class Gordioida. Gordioidean adults are free-living in freshwater or semiterrestrial habitats and larvae parasitise insects, primarily orthopterans. Unlike nectonematiodeans, gordioideans lack lateral rows of setae, have a single, ventral epidermal cord and their blastocoels are filled with mesenchyme in young animals but become spacious in older individuals.

title: Nematomorpha