Jean-Baptiste Bordier

Anthony Mirabile

Robin Courant

Marc Christie

Smart Motion Trails for Animating in VR

Keywords: computer animation, VR, user evaluation

The artistic crafting of 3D animations by designers is a complex and iterative process. While classical animation tools have brought significant improvements in creating and manipulating shapes over time, most approaches rely on classical 2D input devices to create 3D contents. With the advent of virtual reality technologies and their ability to dive the users in their 3D worlds and to precisely track devices in 6 dimensions (position and orientation), a number of VR creative tools have emerged such as Quill, AnimVR, Tvori, Tiltbrush or MasterPieceVR. While these tools provide intuitive means to directly design in the 3D space by exploiting both the 6D tracking capacity of the hand devices and the stereoscopic perception by the user, the animation capacities or such tools remain strongly limited, and often reproduce classical 2D manipulators in VR. In this work, we propose the design of smart interactive manipulators which leverage on the specificity of VR to animate poly-articulated animations. We then perform a user study to evaluate the benefits of such manipulators over traditional 2D tools for three groups of users: beginner, intermediate, and professional artists. We build on this user to discuss how smart tools (e.g. using a variety of AI techniques) can be coupled with VR technologies to improve content creation.

I. INTRODUCTION

Given the importance that animations play in the spectators perception and reception of a visual storytelling experience, the design of complex animated contents has always been a challenging and time consuming task for artists. The authoring of animations in professional software essentially relies on keyframing+interpolation techniques: a number of poses are created (the keyframes) and various parameterized interpolation techniques link the keyframes together. Animators generally rely on a clean-and-lean principle which tends to minimize the number of keyframes, and exploit the parameters of the interpolation techniques to craft the desired motion. In the case of curve interpolations such as Bézier or Spline representations, animators indirectly control the curves in 2D panels, by manipulating the individual tangents on each degree of freedom to obtain the desired animation.

Improving such classical animation techniques then requires to assist the artists in the posing task and in the interpolation task. Many techniques have been proposed in the literature (from early inverse kinematics to ease posing of poly articulated figures [START_REF] Aristidou | Inverse kinematics techniques in computer graphics: A survey[END_REF], to more recent approaches using line of action constraints [START_REF] Guay | The line of action: an intuitive interface for expressive character posing[END_REF], or space-time sketching [START_REF] Choi | Sketchimo: sketch-based motion editing for articulated characters[END_REF], [START_REF] Guay | Space-time sketching of character animation[END_REF]). Contributions such as tangent space optimization [START_REF] Ciccone | Tangent-space optimization for interactive animation control[END_REF] follow this trend by favoring direct control of the interpolation, intuitively grabbing and manipulating the interpolation curves, and automatically optimizing the individual positional/rotational tangents to fit the desired manipulation.

Most of these improvements have been designed for traditional desktop animation tools. A recent trend, with the technical improvement in VR technologies, is to use virtual reality as an authoring environment to create and lay out contents. Multiple tools 1 (Quill, AnimVR, Tvori, Tiltbrush or MasterPieceVR,...) have been developed which build on VR specificities such as direct control of 6 degrees of freedom through devices in each hand, and stereo visualization which helps to resolve some depth ambiguities therefore avoiding multiple camera manipulations or multiple orthographic views that were necessary with desktop tools. VR tools were also used in filmmaking contexts with success as in The lion King movie 2 , and Ready Player One movie that exploits VR to place the actors and cameras 3 . Such tools were essentially used for layout tasks, while more complex stages such as the animation of characters were still performed on traditional desktop tools.

The animation capacities of VR content creation tools have only been recently developed, driven by the higher affordances they offer and improved spatial understanding. For example, the MARUI plugin for Maya4 offers all the traditional animation capacities by simply duplicating the 2D interface in VR and enabling direct 3D/6D manipulations. Other tools have also ported animation features to VR (Dreams, Quill, Tvori, AnimVR, MasterpieceVR) by directly transposing the features, or adapting them to the specificities of VR. While there is a demonstrated practice through the design and usage of these tools, the question we raise in this work is how can smarter tools, driven by AI/optimization techniques, rely on the VR capacities to improve 3D content creation.

Some prior work has demonstrated the benefits of animating in VR compared to animating with 2D interfaces [START_REF] Cannavo | Immersive virtual reality-based interfaces for character animation[END_REF], [START_REF] Lamberti | Is Immersive Virtual Reality the Ultimate Interface for 3D Animators?[END_REF]. Researchers evaluated and demonstrated the capacity of VR techniques to handle tasks such as rigging (placing articulations and bones in meshes), skinning (designing the influence of bones on the mesh) and animating. Despite the displayed benefits of VR over traditional interfaces, the experiments proposed by the authors were limited in multiple ways: (i) first the tasks were performed on simplistic models and involved simplistic animations, which are not relevant of the real-life cases in production studios, (ii) second the implemented features only enabled the control of the poses through keyframes placements but did not offer optimized control on the interpolation technique in contrast with classical animation techniques where artists spend significant time in fine tuning trajectories and (iii) third, the paper transposed classical animation widgets (gizmos) in VR without necessarily thinking about their adaptation to VR specificities (natural affordances, 6D manipulation, improved spatial perception), finally (iv) the authors have separated the posing task into multiple subtasks, by separating a keyframing task where users were asked to pose a complex character on only one frame, interpolation task, and path manipulation task. Each was performed on simple and different objects, in an unlimited time which is not entirely representative of the work of an animator in a production environment.

The purpose of our paper is twofold: first to evaluate the benefits of VR techniques for complex animation tasks such as the authoring of character animations, by extending the scope of existing contributions such as [START_REF] Cannavo | Immersive virtual reality-based interfaces for character animation[END_REF], [START_REF] Lamberti | Is Immersive Virtual Reality the Ultimate Interface for 3D Animators?[END_REF], and second to show how VR can benefit from smarter interaction tools using optimization techniques. To this end, we (i) propose a user evaluation of a complex and full animation posing task in a limited time, involving a 17 bones character animated over a sequence of 54 frames, comparing a traditional animation pipeline, with two different VR versions (traditional tools implemented in VR and a and a more sophisticated version with smart optimization-driven tools to manipulate interpolation and bones trajectories) for three categories of users: beginners, intermediate and expert animators, and (ii) propose a second user evaluation to precisely highlight the benefits of smart tools in VR animation tasks.

We formulated our experimental study in a way to verify following hypothesis: (i) VR interfaces improve the productivity of animators in complex animation tasks (keyframing plus interpolation), and (ii) smarter manipulation tools in VR are preferred to traditional tools adapted to VR. We build our evaluation by comparing a traditional animation tool (Unity) with VRTist, an open-source VR animation tool developed by Ubisoft. We selected the Unity animation tool (which is not the mainstream tool for animators) to avoid a strong bias in comparing a tool completely new (VRTist) with a mainstream tool on which users have hundreds of hours of training. We extended the VRTist with dedicated animation features, in particular by implementing dedicated trajectory manipulation tools such as tangent-controlled motion trails. A motion trail is a 3D curve representing an object's position and orientation over time. Over this motion trail, we implemented the tangent space optimization (TO) approach [START_REF] Ciccone | Tangent-space optimization for interactive animation control[END_REF] so that the designers could directly manipulate the trajectories. Details on the system used for the experiments are presented in section 3, experiments are reported in section 4 and 5 before making recommendations and concluding in section 6.

II. RELATED WORK

Virtual Reality technologies have already shown a strong application potential, not only as a device to improve immersion in narratives but also as a mean to better learn and create.

Well known examples include physical education learning where VR shows improvements in spatial orientation and distance estimation [START_REF] Gómez-García | Augment reality and virtual reality for the improvement of spatial competences in physical education[END_REF], or productivity increase in spherical videos editing tasks [START_REF] Nguyen | Vremiere: Inheadset virtual reality video editing[END_REF]. In the following, and in line with our contribution, we will present recent contributions focusing on the creative potential of VR techniques.

A. VR animation tools in the industry

A number of VR animation applications have been developed such as Tvori [START_REF]Tvori[END_REF] or Quill [START_REF][END_REF]. Both propose keyframebased animation systems. Quill is more sketch-oriented, while Tvori is more 3D object oriented. Tvori proposed animation tools using features such as curve manipulation. In Tvori, curves are available only for rigid and non-articulated objects and not for character posing. Furthermore, Tvori enables character animation using inverse kinematics. A constraint system is added that enables to lock some parts of the body (feet on ground/hand on table) while manipulating the animation.

B. Assessing benefits of VR animation tools

In [START_REF] Vogel | AnimationVR-Interactive Controller-Based Animating in Virtual Reality[END_REF] researchers proposed a Unity plugin using VR to animate objects and characters. They proposed some functionalities to keep an environment close to what traditional software proposed. Authors implemented a simplified timeline with blocks of animation instead of keyframes and proposed traditional 3D gizmos together with direct manipulation with VR controllers, as well as inverse kinematics. A current issue in VR selection is the number of actions necessary to move around the scene and to select and interact with entities. Here, the tool implements a local representation table which is a local copy of selected object or character, right next to the operator. It allows the animator to easily select/animate object's components independently from their root position and rotation. Animators can also incarnate the character and directly record the motion. The proposed work only followed a loose user evaluation through interviews with four expert animators. Main feedback was the ease of prototype, at the expense of preciseness.

Galvane et al. [START_REF] Galvane | Vr as a content creation tool for movie previsualisation[END_REF] proposed a VR tool to assist the movie previsualization task. The tool was designed to create storyboards and was reported to be satisfying to use and efficient for the task. The content produced with the tool was however evaluated as insufficient to be more than only previsualization material due to limitations in the features implemented and reported lack of intuitiveness. Regarding animation features, authors implemented a first proof of concept where designers could manipulate the character rig using inverse kinematics techniques, and could perform animation through the control of poses only (and not control on the interpolation techniques). No visual gizmos were added to manipulate the character. The user evaluation relied on a NASA-TLX evaluation (10 volunteers mixing novices and experts) as well as on a Technology Acceptance Model (TAM) evaluation (with 3 experts), yet objective performance measures were not performed.

More formal evaluations were conducted by Lamberti et al. [START_REF] Lamberti | Is Immersive Virtual Reality the Ultimate Interface for 3D Animators?[END_REF] who designed four classes of experiments representative of simple animation tasks, and compared the traditional Blender interface and with a dedicated VR interface.

• Posing task: participants were asked to place a crocodile mesh composed of 17 bones in a pose as close as possible to a given target pose. The pose had to be done for only one frame.

• Keyframing task: participants were asked to place a car at the right position and orientation, but also to animate the car's color along time. • Performance task: participants were given the ability to directly control joints with their 6D controllers (incarnation). Alike a motion capture setup, the selected joints will follow the translations and rotation of VR controllers.

Participants were asked to animate a three joint eagle shaped mesh using IK and reproduce a given animation. • Path task: participants were asked to place two keyframes and create a trajectory of two spheres to match a target trajectory. • Interpolation task: participants were asked to manipulate a bouncing ball, placing 6 keyframes and manipulating the tangents in an editor graph in VR to fit with a target trajectory. Results showed that the time to reproduce an animation in VR was lower than in native Blender interface. The experiment did not report a significant difference in animation accuracy between VR and Blender.

C. Discussion

The work in the literature closest to our own is [START_REF] Lamberti | Is Immersive Virtual Reality the Ultimate Interface for 3D Animators?[END_REF]. Authors performed a separation of classical tasks for animators. Indeed, animators who perform the posing task usually start from a given animatic (represented by a target animation, pose, interpolation etc) and animate their character or object to fit as much as possible the animatic. The partition of this task in multiple smaller tasks with different objects may not be representative of a classical animation task as conducted by professionals. Indeed, the posing task with a complex character composed of 17 bones is very interesting but limited in the choice to do only one pose in one frame.Further, the path task is reduced to a simple primitive (sphere) animation. Despite this simplicity, the results in favor of VR should generalize to more complex objects such as characters with individual joint manipulations. Similarly, the interpolation task have been proven possible with their F-Curve tool in VR but using a simple object with no kinematic involved. To get a better understanding of the possible improvement of VR over traditional interfaces, it would be preferable to conduct and evaluate these tasks together with a posing task on more complex animations with a complicated character, and this is the objective of our work.

III. SYSTEM OVERVIEW

To perform our experiments, we proposed to compare the traditional Unity environment which provides manipulators for character animation, and a VR character animation environment that we developed above the VRTist tool 5 . We could have used a more artist-oriented traditional tool (Maya, Motion Builder, 3DSmax, Blender) rather than Unity, yet we wanted to avoid a too strong bias of intermediate and expert users towards these tools. Indeed, in the Unity interface, the interactions were not exactly the same than what expert and 5 https://github.com/irisa-invictus/vrtist intermediate users are used to. Unity still proposed the same 3D gizmos than in artist-oriented tools and the shortcuts are almost the same. But the whole interface takes a little more adaptation time for intermediate and experts, who generally rely on strong habits.

VRTist is an open-source VR authoring environment developed by Ubisoft scene layout tasks in VR. A large range of features is proposed such as camera/light placement and recording, VR video editing, exporting, or rapid sketching of volumetric shapes.

A. Unity manipulation features

We introduce the features of the Unity animating tools. 1) Timeline and animation clips: . Unity implements animations using animation clips. An animation clip contains all the keyframes and interpolation curves related to a specific object. Keyframe manipulation can also be performed in the animation clip editor, where users can add, remove or setup auto keyframe. Classical auto keyframe mechanisms are also available in Unity (keyframes are placed automatically by the system as the user manipulates advances in time). It is also possible to display the animation curve and edit interpolations curves (e.g. using tangents with Bézier curves).

2) Custom experiment window: During the experiment users had a custom window to control the features: play/pause the animation or use a slider to skip through the animation, display the reference animation as a ghost (translucent character), overlay the ghost to original position to refine the animation, and finally a control to stop the process.

B. VR manipulation features

This section describes the VR features we implemented to animate characters by building on the VRtist tool. Given the possibility to directly manipulate in 6D with a device, manipulation features are essentially based on forward kinematics (FK), inverse kinematics (IK) and tangent space optimization (TO). Since navigating in menus in VR is also a complex task (compared to standard menus), we followed a general process that consisted in replacing feature selection by triggering visual gizmos directly on the entity (the character to manipulate). In our case, the designer was offered a specific gizmo for IK, FK and TO.

1) Experiment window: As in the Unity traditional interface, users had an interface in VR with the same buttons to start the experiment, generate the ghost, play the animation, move in time and terminate the application.

2) Exploiting TO: Tangent space optimization (TO) relies on displaying the temporal trace of an object (or part of an object) trajectory (Fig. 1). By integrating in VRTist the tangent space optimization framework [START_REF] Ciccone | Tangent-space optimization for interactive animation control[END_REF], we provided users with the possibility to directly manipulate in VR the trajectory (positions and rotations of a joint). As the user moves a hand device close to a motion trail, the trail is selected and the area of effect (area between two keyframes) is highlighted. As the user grabs the motion trail, the trajectory is deformed following the controller's translation and rotation, while respecting constraints such as IK angle limits (see [START_REF] Ciccone | Tangent-space optimization for interactive animation control[END_REF] for more details). 3) 3D gizmos: Traditional rotation gizmos were also made available in VR (Fig. 2) as the animators still strongly these tools for precise single axis operations.

4) Timeline: To manipulate time and keyframes, a timeline interface (Fig. 3) is available to users. Participants can add or delete keyframes, or activate the autokey frame mode. The interface also allows the interpolation to be modified to allow blocking (no interpolation) or linear interpolation or Bezier curve interpolation. This window also allows to play the animation in play mode and to move through time in the scene. Fig. 3: Timeline in VRTist. Red dots are keyframes positions.

5) Tools menu:

A dedicated VR tool menu allows to specifically modify the manipulation mode: forward kinematics (FK), inverse kinematics (IK) or tangent space optimization (TO). The user can also display or not the skeleton of the character at each keyframe. Similarly, the offset section allows to display the skeletons and curves placed in space in order to improve the visualization over time.

IV. EXPERIMENT #1

We recruited 14 participants aged between 19 and 51 (M = 30.1; SD = 8.7), separated in three groups according to their animations experience. Four participants (three males one female) were animation experts with more than five thousand hour of animating, five participants (five male) were intermediate level, and five were novice. In these three groups the experience in VR was heterogeneous. In the expert group, one was expert in VR which means more than 100 hours using a headset, and three were novice which means less than ten hours. All participants in intermediate group were novice in VR. In beginner group, one was master in VR experience, three were novice and one was medium (more than 10 less than 50 hours).

A. Protocol

For this experiment, participants had to recreate an animation of a complex humanoid character in 15 minutes. The target animation is a character throwing a bottle into a tire. The character has 54 joints all of which can be manipulated. For the sake of the experiment the 3 joints of each finger were not taken into account to avoid to lengthy experiments. The experiment was realized in three parts and the order was drawn randomly. One part was performed on Unity with the traditional animation interface (TUI) where the participants had to modify the clip animation by manipulating the joints of the character via the rotation gizmo in the same way as on Blender or Maya. Animation curves of each joint could be edited by changing the tangents in the unity dedicated interface. The traditional VR part (VRTT for VR Traditional Tools) offers the same manipulation possibilities than with Unity, which means forward kinematics (FK) manipulation through gizmos or directFK manipulation through the 6 Degrees of freedom of the VR controller (like in [START_REF] Vogel | AnimationVR-Interactive Controller-Based Animating in Virtual Reality[END_REF], [START_REF] Lamberti | Is Immersive Virtual Reality the Ultimate Interface for 3D Animators?[END_REF]) and finally the smart VR part (TO for tangent optimization) allowed users to manipulate the keyframes and motion curves in FK or IK.

B. Evaluation criteria

During the evaluation, the software collected an accuracy metric which is expressed as the sum from frame 1 to last edited keyframe K of angular distances between target animation joint j ′ and participant animation joint j, for all joints but fingers.

∀j, j ′ ∈ J, J ′ , Accuracy = K i=1 (θ(j i , j ′ i )) K (1)
where θ() measures the absolute difference in degrees between two joints. In addition the software collected few crucial quantitative metrics:

• Number of actions: Number of primitive actions performed by the user (trigger pressed, grab pressed, right clicks, left clicks etc...) • Number of frames with a keyframe: total number of frame where the participant placed at least one key frame.

To complete this data, a NASA-TLX form was submitted to subjects to collect qualitative data for each step of the evaluation. An additional form was used to collect impressions about the following points:

• VR Experience: amount of experience in VR;

• Animation Experience: amount of animation experience;

• Tools rating: which tool was found the most efficient, easiest to learn, easiest to perform the task, natural, comfortable, satisfying, less tiring and frustrating; • Motion sickness: did the subject feel any VR sickness?

• VR usage pleasure: did the subject enjoy using VR?

• VR efficiency to animate: does the subject think that VR can be used efficiently as an animation tool? • First thought/last thought: did the subject change his mind about usability of VR as an animation tool after the evaluation?

C. Results

For Experiment#1, the results of the users were grouped according to their experience in animation. We report results in terms of how the techniques influenced the accuracy of animated sequence, the number of keyframes placed (as a proxy for productivity), as well as qualitative results.

1) Influence on accuracy.: As found in literature [START_REF] Lamberti | Is Immersive Virtual Reality the Ultimate Interface for 3D Animators?[END_REF], for all three groups, the results in terms of accuracy between traditional VR (VRTT) and traditional tools (Unity TUI) showed no striking difference. The group with the most difference in accuracy (see Fig. 7) is the professional group where the animation produced on TUI was a little more accurate than the animation produced with the traditional VR tools (paired t-test value=0.878 and p-value < 0.05). Over all the joints for all the frames of the animation, the one made on Unity has on average a difference of 21 degree compared to the reference animation. The traditional VR animation has an average difference of 26 degrees. For the rest of the users the difference is even smaller, with one degree difference between the TUI and VRTT version. However, the most striking difference is between VRTT and Tangent Optimization (TO). It appears from the data that the smart tools have allowed all groups to be more accurate: in the beginners group, a difference of almost 10 degrees was found in average on all joints when using TO (paired t-test=-3.59, p-value < 0.05).

2) Influence on number of keyframes.: For the rest of the quantitative data, several interesting points can be observed. In the figure 4, the group that placed the most keyframes on all three stages is the group of beginners. On average a little more than 14 keyframes were placed with the smart tools, 13 with the VR offering traditional tools, and 9 on the traditional Unity interface. This means that for this group the keyframes placed with TO were more accurate than the keyframes placed with VRTT. The ratio of angular difference per frame is 1.07. For VRTT this ratio is 1.84. For TUI this ratio is even greater (2.66).

For the intermediates group (Fig. 5), similarly, the most productive tool in terms of keyframes created is TO. However this group was also very productive on Unity (a little more than 12 keyframes for TO against a little less than 12 keyframes for TUI). In terms of angular difference per frame, values are 1.47 for TO, 2.05 for VRTT and 1.62 for TUI. Similar to the beginners group, the intermediates were more productive and accurate when using the intelligent tools in VR. However, they performed better on Unity than on the traditional VR tools.

For the group of professionals (Fig. 6), they have created very few keyframes compared to the two previous groups. Indeed, on average, the professionals created a little less than 8 keyframes in TO against a little more than 5 in VRTT and 6.5 in TUI. However, they managed to be overall more accurate (Fig. 7). This can be explained by a greater precision on the created poses as well as an more manipulations of the interpolation curves to fit the best with the reference animation.

This further supports our belief that performing a complete posing phase for complex animations (including interpolation) is necessary to properly evaluate the relevance of a VR animation tool. We obtain a ratio of 2.62 for TO, 4.80 for VRTT and 3.23 for TUI. However, one drawback we can note is that for all groups, the use of intelligent tools in VR requires more actions than the traditional interface. As illustrated in the figures 4, 5 and 6 TO on average required 481 actions against 430 for TUI.

3) Qualitative evaluation: . The qualitative data illustrates the difference in performance among beginners. As shown in Fig. 8(a), the mental load was much higher on TUI than in VR (both VRTT and TO). Surprisingly and identically, beginners found TUI more physically challenging than VR. The level of productivity to validate a pose is also reflected in their responses to the NASA TLX, as in terms of completion time, the TO task was not felt to be especially difficult to complete in 15 minutes while the TUI task was reported to be difficult to complete in the allotted time.

The accuracy score is also reflected in the responses of the beginner participants, who felt that they did very well on the task in TO but not so well on VRTT and even worst TUI. Indeed, the ratio of success to amount of work is much higher on average in TO (2.6) than in TUI (0.5). The feeling of stress and discouragement was also much more present in TUI (5.1) and VRTT (4.2) than in TO (2.1). However, regarding the qualitative data (Fig. 8(b)), the results collected during the experiment are not the same as the participants' feelings. Indeed, as shown in the figure, with TUI, the mental load was much higher than on the TO and a bit higher than VRTT. However, as expected, the physical load was perceived as superior in VR by the intermediates.

For the rest, overall VR setup was preferred to TUI, noted as less stressful, more efficient to perform the animation in the given time, with participants feeling more successful in recreating the animation for less hard work (except for VRTT where participants success feeling is higher in TUI). Regarding the responses of professionals to the NASA TLX, the mental load in TO was less than with TUI but the most demanding task was VRTT.

However, as with the intermediate group and as expected, VR was perceived as a little more physically demanding (Fig. 8(c)). The task seemed much more difficult to do in the time allotted on TUI than in VR (5.5 in TO versus 5.95 in VRTT and 7.3 with TUI). For the feeling of success, the results are in agreement with those of accuracy Fig. 7. Indeed, the professionals estimate that they have done better in TO with a value of 4.5. For the VRTT task they estimate their success at only 3.5 which is less than TUI which obtained a score of 4.2. The task that gave them the most stress and difficulty was the VRTT task with a very high score of 8.2. TO was once again the most appreciated (6.5 and TUI 7).

V. EXPERIMENT #2

The purpose of the second experiment is to better understand which tools proposed in experiment #1 were the major reason of the good performance in animating in VR. This remains a preliminary study due to the low number of participants, and results must be considered with care. Yet first elements seem to display interesting results. Four participants aged between 19 and 30 (M = 25.25; SD = 3.9) were recruited, composed of two groups based on their animation skills and experience. Two were complete beginners in animation and two were intermediate with more than two hundred hours of animating. All participants were male aged between 19 and 33 years old. About VR experience, one in each group had a medium experience in VR (i.e. between 10 and 50 hours of VR). The last in the intermediate group was a confirmed VR user (+100 hours). The last in the beginners group was also a VR novice.

A. Protocol

For the second experiment, there was no limitation of time. Participants had four different steps to validate. All tasks consisted in manipulating a character arm through a wall with a crack, avoiding as much as possible collisions. There were two different setups, an easy mode and a hard mode (Fig. 9) where the wall gap was more complicated with more obstacles. In the easiest mode, three keyframes were already placed and in the hard mode five keyframes were placed. To manipulate the arm joints, different tools were allowed, the same as in experiment #1 in VR. Subjects could manipulate joints with the 3D gizmo to rotate the joints in forward kinematics (FK) precisely, they could also grab the joints in FK (only rotation) or in inverse kinematics (which impacts both translation and rotation). If they used these tools, they necessarily had to add keyframes to edit the animation trajectory in a way to avoid collisions. With the tangent optimization (TO), participants could directly grab the trajectory and adjust it to avoid wall collisions.

The first two tasks were drawn randomly. Both were run with the easiest setup. One task had only enabled the use of TO, the other only allowed to use IKFK. The purpose of these two tasks was to give some training time to the user for each tool. The third and last task were not drawn randomly. Third task was also with the easy setup but with all tools enabled. Participants could choose which tool to manipulate the arm joints position rotation or interpolation. The last task was with the hardest setup. As in the third task, participants had the choice of the tool.

B. Evaluation criteria

As in the previous experiment, there were two types of data collected, quantitative and qualitative. The software collected:

• Completion time: how long did it take to participants to perform the tasks? • Collisions: how many collisions were encountered with the wall during the tasks? • IK interactions: the number of interactions to animate the character with IK. • FK interactions: the number of interactions to animate the character with FK. • TO interactions: the number of interactions to modify the trajectory between pre-placed key frames. • Amount keyframes: the total number of keyframes placed by the designed for the shoulder, forearm and hand. And the form submitted to the participants collected:

• Preferred tool: which tool did the participants prefer for the easy and hard setups? • Motion trails usage in main software (traditional): if participants used motion trails in their main software such as Blender or Maya to display joints trajectory. • Motion trails accuracy and usability in their main software (traditional). If participants answered "no" to the previous question, would they now use it after they tried it in the experiment. • TO and motion trails accuracy and usability in VR:

do participants think that TO/motion trails are accurate and good tools in VR?

C. Results

The first interesting point is the completion time (Fig. 11). For the first two tasks (training) the completion time is almost equivalent. With the third task (the setup being the same), we see that completion times are different, which shows the benefit of the training for the participants. Participants took 40 seconds less than the first two tasks with similar tools. These data are interesting to cross with the figure 10. Indeed, we can see that during the TO task, the participants made much less collisions than with the IKFK for the same completion time. Another interesting point is that for the task where the participants had the choice in the easy setup, they all used the motion trail to validate the task (Fig. 12). However, they made a few more collisions than on the motion trail task. This could be explained by the fact that they went faster (Fig. 11).

The analysis of the data of the difficult task is interesting. Three people out of four preferred to use the TO to perform this task (Fig. 12). The last person was the only one who preferred to manipulate the character in IK rather than via TO. The person had to add numerous keyframes to edit the animation trajectory. However, this took him much longer to complete, taking 222 seconds longer than the average of the other three participants. On accuracy, he also made many more collisions. The tendency of the IK tool to be less accurate is confirmed here again.

For quantitative data, participants were given a questionnaire to complete. Of the two with intermediate experience in animation, neither used TO on their main software. One thought they could be useful for traditional interfaces and one thought not. However, both agreed that they are useful and effective in VR.

VI. DISCUSSION

A form was given to all participants of both experiences concerning VR in general and as an animation tool. No one hated using VR, three people liked it a little and the rest enjoyed it. Concerning the idea of performing animation in VR, three people were skeptical about its practical use, and they all changed their mind. No one changed their mind in the other direction.

Overall VR was found to be more productive and accurate than TUI for all groups of participants. The biggest difference between the two interfaces was logically found in the beginners, proving the superior affordance of VR. The NASA The results of experiment #2 provide a better understanding of the findings of experiment #1 and the difference with the results obtained by [START_REF] Lamberti | Is Immersive Virtual Reality the Ultimate Interface for 3D Animators?[END_REF]. Indeed, the use of VR with traditional tools like rotation gizmos or even the manipulation of characters in inverse kinematics (IK) and forward kinematics (FK) shows an improvement of the completion time. Yet animation created only with these tools made the precision lower or equal to the traditional tools. With tools like tangent optimization (TO), it seems we can further improve the completion time, while improving the accuracy of animation. Our studies clearly show the importance of controlling the accuracy of the animation techniques proposed in VR. Smarter tools should therefore be designed in ways to build on the natural affordances of VR, yet need to compensate for the lack of accuracy, especially is professional designers are targeted. None of the participants complained in NASA-TLX form about exhaustion. One expert artist was already using VR as a content creation tool and has stated to be used to work and spend a long time in VR. She admitted that the back to reality is a bit tiring at first yet became used to it without any drawback.

VII. LIMITATIONS AND FUTURE WORK

Our work illustrated the capabilities of VR in performing complex animations and demonstrated the benefits of smart interaction techniques. This enabled us to draw some general guidelines, typically showing how the lack of accuracy in VR can be compensated with smarter interactive tools. With a focus on animation character posing, there is still a lot of work that can improve animation creation in VR, by exploring how more evolved AI-driven approaches can assist the designers. This requires both to develop creative-driven AI tools, for which techniques such as deep-learning remain problematic due to the limited availability of dedicated professionally animated dataset, and to design ways to interweave such automated approaches with natural interactions, that would improve accuracy and naturalness of interfaces.

Fig. 1 :

 1 Fig. 1: Tangent optimization manipulation on a character where a user grabs a motion trail to edit the trajectory. The tangents are then optimized to fit the required edit.

Fig. 2 :

 2 Fig. 2: Rotation gizmos in VR to manipulate joints precisely on one axis.

Fig. 4 :

 4 Fig. 4: Number of actions performed by beginners to complete the task, and number of frames with at least one keyframe placed for experiment #1

Fig. 5 : 1 Fig. 6 :

 516 Fig. 5: Number of actions performed by intermediates and number of frames with at least one keyframe placed for experiment #1

Fig. 7 :

 7 Fig. 7: Animation accuracy for each group of participant (Beginners/Intermediates/Professionals) VRTT vs TUI, in Experiment #1.

Fig. 8 : 1 Fig. 9 :

 819 Fig. 8: Nasa TLX answers for each group of participants (Beginners/Intermediates/Professionals), experiment #1

Fig. 10 :

 10 Fig. 10: Collision during the experiment #2 between arm joints and walls for each task (TO/ IKFK / Easy / Hard), experiment #2.

Fig. 11 :

 11 Fig. 11: Completion time for the experiment #2 for all tasks (TO / IKFK / Easy / Hard).

Fig. 12 :

 12 Fig. 12: Preferred tool for both tasks in experiment #2

  VIII. ACKNOWLEDGEMENTThis work is part of the INVICTUS project that has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 952147.

https://www.roadtovr.com/vr-painting-drawing-modeling-animation-arttools-quest-pc/

2 https://ai.umich.edu/blog-posts/how-disneys-the-lion-king-became-apioneer-in-the-use-of-virtual-

reality/ 3 https://www.youtube.com/watch?v=W

6vTqIyPmM 4 https://www.marui-plugin.com/


André Nel
email: anel@mnhn.fr

Romain Garrouste

Enrique Peñalver

Antonio Hernández-Orúe

Corentin Jouault

Discovery of the First Blattinopsids of the Genus Glaphyrophlebia Handlirsch, 1906 (Paoliida: Blattinopsidae) in the Upper Carboniferous of Southern France and Spain and Hypothesis on the Diversification of the Family

Keywords: Insecta, polyneoptera, Gzhelian, new insect locality, Pennsylvanian

des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction

The small Palaeozoic polyneopteran family Blattinopsidae currently contains 12 genera, but only five of them can be accurately considered informative because six are based on very fragmentary fossils and one could be related to another group [START_REF] Quispe | Carboniferous Blattinopsidae: Revision of Klebsiella and new genus and species from Avion (Insecta, Paoliida)[END_REF]. Prokop et al. [START_REF] Prokop | Late Palaeozoic Paoliida is the sister group of Dictyoptera (Insecta: Neoptera)[END_REF] revised the systematic placement of the family and include it within the order Paoliida on the basis of putative wing venation synapomorphies (i.e., configuration of the cubital area). Recently, the family Blattinopsidae was the subject of several new descriptions and revisions, which have greatly increased its diversity, improved its temporal and geographical distribution, and refined the limits of its constitutive genera [START_REF] Quispe | Carboniferous Blattinopsidae: Revision of Klebsiella and new genus and species from Avion (Insecta, Paoliida)[END_REF][START_REF] Rasnitsyn | New species of the genus Blattinopsis Giebel, 1867 (Insecta: Blattinopsida: Blattinopsidae) from the Permian of Taimyr Peninsula, Russia. Far East[END_REF][START_REF] Aristov | New and little known Blattinopsidae (Insecta: Blattinopsida) from the Middle Permian of Russia[END_REF][START_REF] Aristov | New species of the genus Glaphyrophlebia (Insecta, Blattinopsida: Blattinopsidae) from the Upper Carboniferous of Ukraine. Far East[END_REF][START_REF] Aristov | New Blattinopsidae (Insecta: Blattinopsida) from the Middle Permian of European Russia[END_REF][START_REF] Aristov | New Blattinopsidae (Insecta: Blattinopsida) in the Permian of the Pechora Basin (Komi Republic, Russia) in the context of landscape and vegetation evolution[END_REF][START_REF] Aristov | A review of Blattinopsida (Insecta) and flora of Latest Early and Early Middle Permian in European Russia[END_REF].

The number of species in blattinopsid genera is highly heterogeneous. Some genera encompass only one species (e.g., Avionblattinopsis Quispe et al., 2021 [START_REF] Quispe | Carboniferous Blattinopsidae: Revision of Klebsiella and new genus and species from Avion (Insecta, Paoliida)[END_REF]) while others, such as Blattinopsis Giebel, 1867, or Glaphyrophlebia [START_REF] Handlirsch | Revision of American Paleozoic insects[END_REF], have more than 20 documented species (https://paleobiodb.org (last access the 19 October 2022)). Of the two most speciose blattinopsid genera, Blattinopsis is the most diversified during the late Carboniferous, while the second most speciose blattinopsid genus, namely Glaphyrophlebia, is diversified later from the early to middle Permian, but is much rarer during the Carboniferous. This particular pattern of diversity is likely related to taphonomic biases because these insects are all of similar sizes and with similar wing shapes. It may indicate that these two genera occupied a similar ecological niche and one diversified when the other was less present (competition or diversity dependence). It may also reflect the effect of features related to global climate change (e.g., an increase of CO 2 concentration in the atmosphere, change in floral assemblages, glaciations) known to occur between the Carboniferous and the Permian (i.e., Carboniferous rainforest collapse) and could have affected the diversity dynamics of major insect clades as it does for vertebrates [START_REF] Pardo | Carboniferous-Permian climate change constrained early land vertebrate radiations[END_REF]. However, the poor delimitation of several blattinopsid genera hampers our understanding of their diversification and extinction. This is notably the case of the genus Glaphyrophlebia, known from two Moscovian and two Gzhelian species, and a few specimens from North America and Western Europe, one of these species possibly not a Glaphyrophlebia (see below). Descriptions of well-preserved specimens are crucial to refining the limits of each genus and gathering information on morphological diagnostic characters. Based on the fossil record of the family and the genera Blattinopsis and Glaphyrophlebia, we propose that the diversification of the family was related to changes in climate and floral assemblages between the Carboniferous and Permian periods.

During preliminary fieldwork in the Gzhelian quarry of Tante Victoire, in the Var department (Southern France), we found a very well-preserved forewing that we confidently attribute to a new species of Glaphyrophlebia. This discovery highlights the importance of the locality of Tante Victoire for future discoveries of fossil insects. We also describe the first specimen of Blattinopsidae from the Palaeozoic of Spain, increasing the distribution range of this family. This study is in line with recent descriptions of the few Carboniferous insects found both historically and recently in Spain [START_REF] Santos | Late Carboniferous insects from the Iberian Peninsula: State of the art and new taxa[END_REF][START_REF] Nel | The first representative of the roachoid family Spiloblattinidae (Insecta, Dictyoptera) from the Late Pennsylvanian of the Iberian Peninsula[END_REF].

Material and Methods

The holotype of the new species was found in 1996 during a preliminary field investigation in the ancient iron quarry of Tante Victoire, Var department (latitude 43.115573 • , longitude 5.827614, altitude 94.05 m). The Spanish specimen was found by one of us (AHO) during Ph.D. research on the revision of the morphogenus Pecopteris on fossils collected at the tip of a small coal mine near El Repoteo in Tremor de Arriba, Province of León. No additional preparation of the fossils was necessary for their study. The French specimen was photographed using a Canon EOS 50D camera with an attached Canon 65 MPE camera lens and mounted on an automated stacking rail (StackShot); all these images are digitally stacked photomicrographic composites of several individual focal planes, which were obtained using the software Helicon Focus 6.7. The figures of the French specimen were composed with Adobe Illustrator CC2019 and Photoshop CC2019 software. The Spanish wing specimen and plant remains (on the same slab's surface) were photographed using a compound microscope Olympus BX53 with an integrated digital camera, and with an Olympus Tough TG-5, respectively. The photograph of the wing fragment is a stacked image, unlike the plant remains images. The plate with these images was composed using Photoshop CS2 version 9.0.

The small ancient iron quarry of Tante Victoire (Playes Massif, Six-Fours-les-Plages town, Var department) is of Gzhelian age (late Stephanian), and the palaeoflora was composed of Pecopteris, Calamites, Walchia, and Sigillaria ('Notice de la Carte Géologique à 1/5000, BRGM, France' of Toulon). The holotype MNHN.F.A71360 is deposited in the Palaeontological collection of the Muséum National d'Histoire Naturelle (MNHN.F), Paris, France.

The wing fragment of the Spanish specimen was found on a sandstone slab at the tip of a small mine 2.4 km at the NW of Tremor de Arriba, Province of León (latitude 42 • 44 5 N, longitude 6 • 11 3 W, altitude 1.180 m). This mine belongs to the El Bierzo outcrop, Noceda Block, Tramo de Espina [START_REF] Fernández García | Revisión y síntesis geológico-minera de la cuenca carbonífera de "El Bierzo" (León)[END_REF] and is of Gzhelian age based on the rich floral assemblage [START_REF] Wagner | The Carboniferous floras of the Iberian Peninsula: A synthesis with geological connotations[END_REF][START_REF] Knight | A summary of upper Pennsylvanian regional substages defined in NW Spain-the chronostratigraphic legacy of Robert H. Wagner[END_REF]. The specimen MGM-822H-1 is deposited in the collection of the Museo Geominero (Instituto Geológico y Minero de España, CSIC), Madrid, Spain.

Wing venation nomenclature follows Prokop et al. [START_REF] Prokop | Late Palaeozoic Paoliida is the sister group of Dictyoptera (Insecta: Neoptera)[END_REF] and Schubnel et al. [START_REF] Schubnel | To be or not to be: Postcubital vein in insects revealed by microtomography[END_REF], especially concerning the presence of postcubital veins in Pterygota. Abbreviations are as follows: A, anal vein(s); arc, arculus reinforced oblique crossvein between M and CuA; C, costal vein; CuA, cubitus anterior; CuP, cubitus posterior; M, median vein; PCu, postcubital vein; RA, radius anterior; RP, radius posterior; and ScP, subcostal posterior.

Abbreviations for Museums: MNHN, Muséum national d'Histoire naturelle, Paris, France; and MGM, Museo Geominero (Instituto Geológico y Minero de España, CSIC), Madrid, Spain.

Published work and nomenclatural acts are registered in ZooBank (http://zoobank. org/, last access: 13 December 2022), with the following LSID (reference): urn:lsid:zoobank.org:pub:DE09A321-00C3-4A35-A018-19BE9BFFEEBC. Diagnosis. Forewing characters only. Wing large and elongate, ca. 18 mm long; costal area at base of RP slightly wider than subcostal area; ScP flexed S-line at its apex; vein bow between RA and main stem of M; RP with six main branches; M with four branches; anterior branch of M forked close to M fork; anterior branch of CuA zigzagged with numerous crossveins between anterior and posterior main branches; and posterior branches of CuA zigzagged.

Results

Systematic

Description. No particular trace of coloration; wing ca. 18.0 mm long and ca. 5.7 mm wide; costal space with veinlets mainly simple; ScP ending on C well distad mid-wing; stem R weakly sigmoidal at base; RA with a posterior branch forked; fork of R located slightly distad r-m crossvein; base of RP at 5.0 mm from wing base, second fork of RP slightly distad M fork; first branch of RP simple; second branch of RP forked close to wing margin; third branch of RP forked, anterior branch forked extremely close to dichotomy with simple posterior branch; fourth branch of RP dichotomous; fifth branch of RP forked; convex arculus entering CuA well before its first fork; M with four branches, fork of anterior branch well-basad fork of second branch; CuA with a zigzagged anterior branch, and with at least 11 zigzagged and rather weak posterior branches, first fork located proximal to M fork; CuP straight and simple; PCu simple and slightly sigmoidal; three main anal veins; numerous simple crossveins in radial and median areas; distinct longitudinal furrows between branches of RP and M, reaching edge of wing; and vein bow between RA and main stem of M only. Remarks. This fossil is undoubtedly a forewing because of the narrow anal area. It can be attributed to the order Paoliida sensu Prokop et al. [START_REF] Prokop | Late Palaeozoic Paoliida is the sister group of Dictyoptera (Insecta: Neoptera)[END_REF] because of the following characters: concave ScP approximating RA in distal half of wing; strongly convex RA with weak, short but distinct anterior branches, unusually prominent steep elevation from ScP to RA forming a characteristic wing profile; costal area between ScP and costal margin with series of simple, oblique veinlets; RP rather concave with numerous branches; M somewhat concave; convex CuA and concave CuP separating from a rather long basal stem Cu; CuA not in contact with the stem R+M; area between CuP and CuA broad compared to median and radial areas (autapomorphy), a general course of CuA making a double curve (autapomorphy); CuA has convex posterior branches, plus some weaker concave anterior branches; CuP simple, nearly straight; and anal fan strongly reduced.

Affinities with the family Paoliidae Handlirsch, 1906, are excluded because the area between CuA and CuP is not very wide, just slightly wider than the area between CuA and M in their basal parts. Affinities with the family Anthracoptilidae Handlirsch, 1922, are excluded because they all have numerous anterior concave branches of CuA, while the new fossil has only one, as in the Blattinopsidae.

Within the known Blattinopsidae, except in Avionblattinopsis, ScP is ending on C as in the new fossil, precluding affinities with the latter genus. Additionally, the anterior branch of CuA is better defined in Avionblattinopsis than in the new fossil, and the area between ScP and R/RA is just half as wide as the area between ScP and C in Avionblattinopsis, while the two areas are of the same width in the new fossil [START_REF] Quispe | Carboniferous Blattinopsidae: Revision of Klebsiella and new genus and species from Avion (Insecta, Paoliida)[END_REF]. Interestingly, the species type of Stephanopsis, namely Stephanopsis incerta [START_REF] Laurentiaux | Les insectes des bassins houillers du Gard et de la Loire. [Insects from the Gard and Loire coalfields[END_REF] (originally in the genus Blattinopsis Giebel, 1867), has an area between ScP and RA much narrower than that of Avionblattinopsis, excluding affinities of the new fossil with this genus [START_REF] Laurentiaux | Les insectes des bassins houillers du Gard et de la Loire. [Insects from the Gard and Loire coalfields[END_REF].

In the genus Klebsiella, ScP is strongly approximating RA before ending on C, and the crossveins in the radial and median areas are much less numerous than in the new fossil, which precludes affinities of the new specimen with this genus [START_REF] Quispe | Carboniferous Blattinopsidae: Revision of Klebsiella and new genus and species from Avion (Insecta, Paoliida)[END_REF].

In the new fossil, and in the described species of the genus Glaphyrophlebia, there are distinct longitudinal furrows between branches of RP and M, reaching the edge of the wing, unlike in Blattinopsis. On the contrary, the new fossil would share with Blattinopsis the presence of numerous crossveins between branches of RP and M, unlike many Glaphyrophlebia [START_REF] Quispe | Carboniferous Blattinopsidae: Revision of Klebsiella and new genus and species from Avion (Insecta, Paoliida)[END_REF][START_REF] Rasnitsyn | New species of the genus Blattinopsis Giebel, 1867 (Insecta: Blattinopsida: Blattinopsidae) from the Permian of Taimyr Peninsula, Russia. Far East[END_REF][START_REF] Aristov | New species of the genus Glaphyrophlebia (Insecta, Blattinopsida: Blattinopsidae) from the Upper Carboniferous of Ukraine. Far East[END_REF], but some species currently attributed to the latter genus also have rather numerous crossveins in the radial and median areas [START_REF] Aristov | New Blattinopsidae (Insecta: Blattinopsida) in the Permian of the Pechora Basin (Komi Republic, Russia) in the context of landscape and vegetation evolution[END_REF][START_REF] Aristov | A review of Blattinopsida (Insecta) and flora of Latest Early and Early Middle Permian in European Russia[END_REF]. Therefore, the new species is attributed to the genus Glaphyrophlebia.

Differences from Other Species of Glaphyrophlebia

Following the key to the Permian Glaphyrophlebia sp. proposed by Aristov et al. [START_REF] Aristov | A review of Blattinopsida (Insecta) and flora of Latest Early and Early Middle Permian in European Russia[END_REF], the character 'M branching (besides terminal forks)' excludes affinities with all these species except G. The new fossil differs from G. anderhalterorum because there is no longitudinal vein emerging from R basad RP [START_REF] Beckemeyer | A new species of Glaphyrophlebia Handlirsch, 1906 (Insecta: Neoptera: Blattinopsidae) from the Lower Permian Wellington Formation of Noble County, Oklahoma, USA, The Carboniferous-Permian transition[END_REF]. Affinities with the species Glaphyrophlebia clava and G. arnulfi are excluded because CuA is divided into an anterior branch with one-two terminal forks and a comb-like posterior branch in the new fossil while the CuA is pectinate in G. clava and in G. arnulfi [START_REF] Hörnschemeyer | Review of Blattinopsidae (Prothortoptera) with description of new species from the Lower Permian of Niedermoschel (Germany)[END_REF]. The new specimen further differs from G. arnulfi owing to its comparatively wide costal space (i.e., wider than subcostal space at the diverging point of RP), while the costal space of G. arnulfi is thinner than the subcostal space [START_REF] Hörnschemeyer | Review of Blattinopsidae (Prothortoptera) with description of new species from the Lower Permian of Niedermoschel (Germany)[END_REF].

Glaphyrophlebia rohwedderi differs from the new fossil and G. jeckenbachi because of its ScP not flexed S-line at apex [START_REF] Hörnschemeyer | Review of Blattinopsidae (Prothortoptera) with description of new species from the Lower Permian of Niedermoschel (Germany)[END_REF]. Glaphyrophlebia rohwedderi also differs from the new specimen owing to the strange branching pattern of the R, i.e., with dichotomy (considered to be an anterior branch of MP in [START_REF] Hörnschemeyer | Review of Blattinopsidae (Prothortoptera) with description of new species from the Lower Permian of Niedermoschel (Germany)[END_REF]) and a second dichotomy creating RP. Similarly, the branching pattern of M (considered as the MP in [START_REF] Hörnschemeyer | Review of Blattinopsidae (Prothortoptera) with description of new species from the Lower Permian of Niedermoschel (Germany)[END_REF]) in G. rohwedderi differs from that in the new specimen because it has a posterior branch (MP as we interpreted it) forking close to the wing margin (vs. well before in the new specimen).

The forewing length and width can be used as discriminatory characters between species when the range of these two measures greatly differs between two species. For example, the forewing length of Glaphyrophlebia jeckenbachi ranges between 10 and 14 mm for a width ranging between 4.1 and 4.8 mm, while in the new fossil, the wing is about 18 mm long (not entirely preserved) for a width of 5.7 mm [START_REF] Hörnschemeyer | Review of Blattinopsidae (Prothortoptera) with description of new species from the Lower Permian of Niedermoschel (Germany)[END_REF]. Additionally, the anterior branch of CuA of G. jeckenbachi is better defined than in the new fossil in which it is more zigzagged with much more crossveins between the anterior and posterior main branches. The vein bow is between RA and CuA in G. jeckenbachi, while it is located between RA and the main stem of M in the new fossil. Lastly, the new specimen has six main branches of RP, while there are only five of them in G. jeckenbachi.

Glaphyrophlebia glinka (Aristov, Rasnitsyn and Naugolnykh, 2022) (lower Permian of the Russian Federation) is based on the basal half of a forewing, ca. 10 mm long, which renders a detailed comparison with the new fossil difficult. Nevertheless, the new fossil differs from G. glinka in possessing a comparatively wide costal space (i.e., wider than subcostal space at the diverging point of RP), but also owing to its RP less pectinated (i.e., wider space between RP branches and apparently less of them) [START_REF] Aristov | A review of Blattinopsida (Insecta) and flora of Latest Early and Early Middle Permian in European Russia[END_REF].

Glaphyrophlebia rossica (middle Permian of the Russian Federation) is based on the middle half of a forewing, with the base and the apex missing, ca. 7.5-8 mm long [START_REF] Martynov | New fossil insects from Tikhie Gory. 2. Neoptera (excluding Miomoptera)[END_REF]. Nevertheless, the illustration of Martynov [START_REF] Martynov | New fossil insects from Tikhie Gory. 2. Neoptera (excluding Miomoptera)[END_REF] suggests that the M is simple (a surprising configuration for this vein), and that the CuA is heavily branched and somewhat pectinate, which strongly differs from the forked M and the non-pectinate CuA of the new specimen.

Glaphyrophlebia pusilla (Moscovian, Mazon Creek, IL, USA), the type species of the genus, is not listed nor keyed in [START_REF] Aristov | A review of Blattinopsida (Insecta) and flora of Latest Early and Early Middle Permian in European Russia[END_REF]. Handlirsch [START_REF] Handlirsch | Revision of American Paleozoic insects[END_REF] indicated nothing on the vein bow. Its forewing is incomplete, but ca. 10 mm long. It also differs from the new fossil in its M with only two branches instead of four in the new fossil, and in its ScP not flexed S-line at its apex (vs. flexed in the new fossil).

Glaphyrophlebia pygmaea (Meunier, 1907) (Gzhelian of Commentry, France, recently attributed to this genus [START_REF] Hörnschemeyer | Review of Blattinopsidae (Prothortoptera) with description of new species from the Lower Permian of Niedermoschel (Germany)[END_REF]) is not listed nor keyed in Aristov et al. [START_REF] Aristov | A review of Blattinopsida (Insecta) and flora of Latest Early and Early Middle Permian in European Russia[END_REF] or in the other recent papers on Blattinopsidae [START_REF] Rasnitsyn | New species of the genus Blattinopsis Giebel, 1867 (Insecta: Blattinopsida: Blattinopsidae) from the Permian of Taimyr Peninsula, Russia. Far East[END_REF][START_REF] Aristov | New and little known Blattinopsidae (Insecta: Blattinopsida) from the Middle Permian of Russia[END_REF][START_REF] Aristov | New species of the genus Glaphyrophlebia (Insecta, Blattinopsida: Blattinopsidae) from the Upper Carboniferous of Ukraine. Far East[END_REF][START_REF] Aristov | New Blattinopsidae (Insecta: Blattinopsida) from the Middle Permian of European Russia[END_REF][START_REF] Aristov | New Blattinopsidae (Insecta: Blattinopsida) in the Permian of the Pechora Basin (Komi Republic, Russia) in the context of landscape and vegetation evolution[END_REF]. It has the forewing venation characters proper to the genus Glaphyrophlebia, especially the presence of longitudinal furrows between branches of RP and M, reaching the edge of the wing. Its forewing is 12.2 mm long and 4.7 mm wide, thus quite shorter than that of the new fossil, and its vein bow is between RA and CuA. Lastly, its posterior branches of CuA are figured better organized, straight and well pectinate (Figure 3), while they are zigzagged in the new fossil. Glaphyrophlebia wettinensis [START_REF] Handlirsch | Revision of American Paleozoic insects[END_REF] (Gzhelian of Germany, recently attributed to this genus [START_REF] Hörnschemeyer | Review of Blattinopsidae (Prothortoptera) with description of new species from the Lower Permian of Niedermoschel (Germany)[END_REF]) is also not listed nor keyed in Aristov et al. [START_REF] Aristov | A review of Blattinopsida (Insecta) and flora of Latest Early and Early Middle Permian in European Russia[END_REF]. It also has a vein bow between RA and CuA, no well-defined anterior branch of CuA, and a straight ScP, unlike the new fossil [START_REF] Hörnschemeyer | Review of Blattinopsidae (Prothortoptera) with description of new species from the Lower Permian of Niedermoschel (Germany)[END_REF][START_REF] Fritsch | Oberste Schichten des Steinkohlen-Gebirges in Schladebach (Wettiner Schichten) [Beschreibung einiger neuen fossilen Insekten in Schleferton des Steinkohlengebirge v Wettin[END_REF]. Additionally, the anterior branch of M is forked close to the first dichotomy of M, while simple or forked far distad the first dichotomy of M in G. wettinensis [START_REF] Hörnschemeyer | Review of Blattinopsidae (Prothortoptera) with description of new species from the Lower Permian of Niedermoschel (Germany)[END_REF].

Glaphyrophlebia delicatula [START_REF] Bolton | New forms from the insect fauna of British coal measures[END_REF], Moscovian, 314.6 Ma, South Wales, UK, recently attributed to this genus [START_REF] Hörnschemeyer | Review of Blattinopsidae (Prothortoptera) with description of new species from the Lower Permian of Niedermoschel (Germany)[END_REF]) is also not listed nor keyed in Aristov et al. [START_REF] Aristov | A review of Blattinopsida (Insecta) and flora of Latest Early and Early Middle Permian in European Russia[END_REF]. It is based on a very incomplete fragment of forewing. Bolton [START_REF] Bolton | New forms from the insect fauna of British coal measures[END_REF] did not indicate the presence of longitudinal furrows between branches of RP and M, and these are not visible in the photograph of the holotype. Therefore, the placement and attribution of the species to the genus Glaphyrophlebia is highly uncertain.

Based on the detailed comparison provided above, the new fossil represents a new species of the genus Glaphyrophlebia, and it is, therefore, the third one from the Carboniferous confidently placed in this genus.

Glaphyrophlebia sp. Glaphyrophlebia wettinensis [START_REF] Handlirsch | Revision of American Paleozoic insects[END_REF] (Gzhelian of Germany, recently attributed to this genus [START_REF] Hörnschemeyer | Review of Blattinopsidae (Prothortoptera) with description of new species from the Lower Permian of Niedermoschel (Germany)[END_REF]) is also not listed nor keyed in Aristov et al. [START_REF] Aristov | A review of Blattinopsida (Insecta) and flora of Latest Early and Early Middle Permian in European Russia[END_REF]. It also has a vein bow between RA and CuA, no well-defined anterior branch of CuA, and a straight ScP, unlike the new fossil [START_REF] Hörnschemeyer | Review of Blattinopsidae (Prothortoptera) with description of new species from the Lower Permian of Niedermoschel (Germany)[END_REF][START_REF] Fritsch | Oberste Schichten des Steinkohlen-Gebirges in Schladebach (Wettiner Schichten) [Beschreibung einiger neuen fossilen Insekten in Schleferton des Steinkohlengebirge v Wettin[END_REF]. Additionally, the anterior branch of M is forked close to the first dichotomy of M, while simple or forked far distad the first dichotomy of M in G. wettinensis [START_REF] Hörnschemeyer | Review of Blattinopsidae (Prothortoptera) with description of new species from the Lower Permian of Niedermoschel (Germany)[END_REF].

Glaphyrophlebia delicatula (Bolton, 1934, Moscovian, 314.6 Ma, South Wales, UK, recently attributed to this genus [START_REF] Hörnschemeyer | Review of Blattinopsidae (Prothortoptera) with description of new species from the Lower Permian of Niedermoschel (Germany)[END_REF]) is also not listed nor keyed in Aristov et al. [START_REF] Aristov | A review of Blattinopsida (Insecta) and flora of Latest Early and Early Middle Permian in European Russia[END_REF]. It is based on a very incomplete fragment of forewing. Bolton [START_REF] Bolton | New forms from the insect fauna of British coal measures[END_REF] did not indicate the presence of longitudinal furrows between branches of RP and M, and these are not visible in the photograph of the holotype. Therefore, the placement and attribution of the species to the genus Glaphyrophlebia is highly uncertain.

Based on the detailed comparison provided above, the new fossil represents a new species of the genus Glaphyrophlebia, and it is, therefore, the third one from the Carboniferous confidently placed in this genus.

Glaphyrophlebia sp. Material. Costo-apical portion of a forewing with the collection number MGM-822H-1 (previous collection number LE-24-101), stored at Museo Geominero (Instituto Geológico y Minero de España, CSIC), Madrid, Spain.

Locality, formation and age. El Bierzo, León Province, Spain, Gzhelian, Carboniferous. Description. Length of fragment ca. 8 mm; area between C and ScP ca. 0.6 mm wide in preserved part; ScP distally straight, ending into C; area between ScP and RA ca. 0.75 mm wide; area between RA and RP ca. 0.6 mm wide; RA with at least six weak apical branches; and RP with six-seven weakly curved posterior branches, with distinct longitudinal furrows between them.

Remarks. This fossil also corresponds to a fragment of a forewing of Glaphyrophlebia because of the presence of distinct longitudinal furrows between branches of RP, ScP ending on C, area between ScP and RA slightly broader than area between ScP and C, and area between RA and RP very broad. The distal part of vein ScP nearly straight excludes affinities with Glaphyrophlebia victoiriensis sp. nov., but could fit with Glaphyrophlebia pygmaea. Nevertheless, the incompleteness of this fossil prevents its attribution to a precise species. A floral assemblage was found on the same slabs or on slabs close to the isolated wing (Figure 4B-F).

Macroevolutionary, Taphonomic, and Palaeoecological Comments

The Blattinopsidae arose during the late Carboniferous and diversified during a period of drastic palaeoenvironmental changes, i.e., the transition from Carboniferous wetlands to more arid forests and conditions during the Permian. The late Carboniferous is renowned for its 'Coal Forests'-widely distributed in Europe and North America around the equatordeveloped under ever wet conditions, sometimes with a drier season [START_REF] Wilson | Dynamic Carboniferous tropical forests: New views of plant function and potential for physiological forcing of climate[END_REF]. A dramatic collapse of these rainforests began during the Pennsylvanian (commonly called the Carboniferous rainforest collapse, CRC), and led by the early Permian to their replacement in many regions by dryland vegetation as a more arid climate developed [START_REF] Cleal | Plant biodiversity changes in Carboniferous tropical wetlands[END_REF][START_REF] Prevec | South African Lagerstätte reveals middle Permian Gondwanan lakeshore ecosystem in exquisite detail[END_REF]. We investigate a plausible link between these events and the diversification of the Blattinopsidae, a link that could be extended to other insect lineages.

Currently, the fossil record of the Blattinopsidae is heterogeneous from the Middle Pennsylvanian to the middle Guadalupian (Figure 5A), with its highest diversity during the Gzhelian and Asselian, i.e., around the Carboniferous/Permian boundary (C/P boundary) (https://paleobiodb.org (last access the 19 October 2022)). Another period of high diversity is the Kungurian, but it is difficult to assess the effect of one or a few variables (e.g., changes in floral assemblages, temperature, and concentration of CO 2 in the atmosphere) on changes in the dynamics of the family (Figure 5). From a pure correlation perspective, which does not necessarily imply causality, the highest level of diversification of Blattinopsidae and of the genus Blattinopsis is documented during a relatively cold period corresponding with the C/P boundary [START_REF] Prokoph | Compilation and time-series analysis of a marine carbonate δ18O, δ13C, 87Sr/86Sr and δ34S database through Earth history[END_REF][START_REF] Condamine | The rise of angiosperms pushed conifers to decline during global cooling[END_REF]. Conversely, the genus Glaphyrophlebia is highly diversified during the Kungurian, a comparatively hot period [START_REF] Prokoph | Compilation and time-series analysis of a marine carbonate δ18O, δ13C, 87Sr/86Sr and δ34S database through Earth history[END_REF][START_REF] Condamine | The rise of angiosperms pushed conifers to decline during global cooling[END_REF]. This observation is not surprising as variations in warming and cooling periods are a probable driver of the diversification of some insect clades and are known to result in diversification changes over the evolutionary history of insects [START_REF] Condamine | Global patterns of insect diversification: Towards a reconciliation of fossil and molecular evidence?[END_REF][START_REF] Halsch | Insects and recent climate change[END_REF].

The Blattinopsidae and the genus Blattinopsis are also highly diversified just after the CRC, i.e., after the gradual rise of opportunistic ferns during the late Moscovian [START_REF] Pfefferkorn | Changes in dominance patterns in Upper Carboniferous plant fossil assemblages[END_REF], during the earliest Kasimovian by the extinction of the dominant lycopsids, and their replacement by tree fern-dominated ecosystems [START_REF] Dimichele | Climate change, plant extinctions and vegetational recovery during the Middle-Late Pennsylvanian transition: The case of tropical peat-forming environments in North America[END_REF][START_REF] Davies | Evolution of fixed-channel alluvial plains in response to Carboniferous vegetation[END_REF]. As aforementioned, the period of diversification of the Blattinopsidae also corresponds with the beginning of the development of arid and warm temperate biome and with the diminution of wet tropical [START_REF] Lehtonen | Environmentally driven extinction and opportunistic origination explain fern diversification patterns[END_REF]. Therefore, we assume that the diversification of the Blattinopsidae is linked with the CRC (i.e., with changes in floral assemblages), the rise of new plant lineages and their diversification, and the expansion of arid biome after the C/P boundary. Similar correlations have already been demonstrated for other insect clades and are likely to occur for putative phytophagous lineages strongly linked with their host plants [START_REF] Jouault | Multiple drivers and lineage-specific insect extinctions during the Permo-Triassic[END_REF]. At the outcrop of El Bierzo, the thin slab where the wing fragment and associated plant remains were found is a sandstone, containing fossils with a shallow relief (positive molds) preserving only testimonial portions of carbonaceous films. The plants in this assemblage are very diverse, containing many species represented (see Table 1: list of plants from El Bierzo): cf. Asterophyllites equisetiformis (Schlotheim, 1820 and Brongniart, 1828), Sphenophyllum oblongifolium (Germar and Kaulfuss, 1831 and Gutbier, 1843) (Figure 4F), Sphenophyllum cf. alatifolium (Renault, 1890), Oligocarpia gutbieri (Göppert, 1841), Oligocarpia leptophylla (Bunbury, 1853 and Grauvogel-Stamm and Doubinger, 1975) (Figure 4D), Sphenopteris sp.-1, Sphenopteris sp. aff. mathetii (Figure 4F), Diplazites unitus (Brongniart, 1836 and Wagner and Martínez-García, 1998), Pecopteris daubreei (Zeiller, 1888) (Figure 4E), Pecopteris sp., Dicranophyllum gallicum (Grand'Eury, 1877), cf. Mixoneura sp., cf. Odontopteris sp. (Figure 4F) and Dicksonites sp. Although there are many plant species/morphotypes (14 + wing) most of them were broken remains, occasionally really tiny, in accordance with their deposition in the stream of a river. Only three plant fossil species are large enough to be considered parautochthonous: Oligocarpia gutbieri (Figure 4B): this plant lived in variable habitats, from lowland places to hillside environments [START_REF] Knight | The Stephanian A-B flora and stratigraphy of the Sabero Coalfield (León, N.W. Spain). Compte Rendu 7e Congrès Int. Stratigr[END_REF].

Dicranophyllum gallicum (Figure 4C): this species developed on mesophytic or even xerophytic communities on basin-margin slopes [START_REF] Remy | Die Floren des Erdaltertums[END_REF][START_REF] Barthel | Pflanzengruppen und Vegetationseinheiten der Manebach-Formation[END_REF][START_REF] Barthel | Die Rotliegendflora des Thüringer Waldes. Teil 3: Farne. Veröffentlichungen Naturhist[END_REF][START_REF] Rasnitsyn | History of Insects[END_REF].

Diplazites unitus (Figure 4D,F): as O. gutbierii, occupied variable habitats, from lowland places such as floodplains or swampy areas to hillside environments [START_REF] Knight | The Stephanian A-B flora and stratigraphy of the Sabero Coalfield (León, N.W. Spain). Compte Rendu 7e Congrès Int. Stratigr[END_REF][START_REF] Barthel | Die Rotliegendflora des Thüringer Waldes. Teil 3: Farne. Veröffentlichungen Naturhist[END_REF].

The sample contains an essentially allochthonous flora, but in part parautochthonous plants that allow us to infer the palaeoenvironment where the Glaphyrophlebia could live. The sandstone was formed from the sediments deposited by a river far from the most basal parts of the basin and that ran through areas close to topographic reliefs that allowed the development of mesophytic or even xerophytic floras.

Similarly, the presence of Walchia in the French locality also supports mesophytic affinities of the flora, but additional studies have to be conducted to provide a full picture of the floral assemblage and taphonomy of Tante Victoire.

Despite the fact that the remains of the genus Glaphyrophlebia are mainly fossilized in water bodies or very humid local environments of preservation, on a regional scale it seems these insects developed or lived in mesophytic and/or xerophytic palaeoenvironments. The genus Glaphyrophlebia likely could have fed on spores (phytophagous) according to Aristov et al. [START_REF] Aristov | A review of Blattinopsida (Insecta) and flora of Latest Early and Early Middle Permian in European Russia[END_REF], even if very little is known about their mouthparts, as Rasnitsyn [START_REF] Rasnitsyn | History of Insects[END_REF] only indicated that they had 'clypeus not much convex, mouthparts chewing'. Therefore, very limited conclusions can be inferred about the biology of these insects. Its fossil record also fits with a long xerophytic period (Pennsylvanian-late Permian). The expansion of this genus in the Permian of Russia, which corresponds to a relatively arid and warm time period, might be correlated with an increase in the abundance of xerophytic vegetation (to which the Glaphyrophlebia are putatively adapted), but additional data and statistical testing will be required.

It is also important to mention that the reduced number of specimens and species of Blattinopsidae (compared with the Carboniferous or earliest Permian) found in Permian deposits may be directly linked with the fossilization that occurred mostly in palaeolakes. The latter are often surrounded by non-xerophytic vegetation and are, therefore, not favorable to the development of Blattinopsidae, which limits their potential for fossilization.

Remark. Rasnitsyn [START_REF] Rasnitsyn | The winged insects (Pterygota Lang, 1888)[END_REF] put the Blattinopsidae in their own order, 'Blattinopsidea' (name later amended to Blattinosida), into a large clade that would comprise the 'Blattinopseida, Caloneurida, the holometabolous, paraneopteran ('psoco-rhynchotan') and palaeodictyopteran clades', defined on the basis of 'their pterothoracic sterna are characteristically invaginated along the midventral line called discrimen (see Figure 69 in the Ref. [START_REF] Rasnitsyn | The winged insects (Pterygota Lang, 1888)[END_REF]), with the furcal arms mounting a common base elevated inside the thorax.' However, these characters are unknown in the Blattinopsidae and this set of taxa does not constitute a clade, as demonstrated by more recent analyses, after which the Palaeodictyoptera are palaeopteran insects.

Conclusions

Glaphyrophlebia victoiriensis sp. nov. is the third Gzhelian species of this genus. Together with the discovery of the first fossil wing of Glaphyrophlebia from Spain, they increase the diversity and distribution of blattinopsids from the Western European Carboniferous deposits and help to document the wing venation variability found in the genus Glaphyrophlebia. The diversity of this genus is high in early and middle Permian strata, especially in the deposits of the Russian Federation. The new species described here suggests that its diversity in the late Carboniferous is underestimated.

Our study proposes a new hypothesis on the diversification dynamics of insects during the Carboniferous period using the Blattinopsidae, and more specifically the Glaphyrophlebia and Blattinopsis, as study groups. We mainly discuss the hypothetic impact of the Carboniferous rainforest collapse on these groups, but it is also important to mention that other factors may have shaped the diversity dynamics of insects during the late Carboniferous. In fact, it has been demonstrated that the diversification and the extinction process are often found to correlate with multiple variables [START_REF] Jouault | Multiple drivers and lineage-specific insect extinctions during the Permo-Triassic[END_REF][START_REF] Jouault | Estimating the drivers of diversification of stoneflies through time and the limits of their fossil record[END_REF], and it is likely that aside from the CRC, other factors such as glaciations or the proportion of mountain area have also played a key role in the radiation or decline of some lineages.

Diversity 2022 , 16 Figure 1 .

 2022161 Figure 1. Glaphyrophlebia victoiriensis sp. nov., holotype MNHN.F.A71360, Gzhelian of Tante Victoire, France: (A) part; (B) counterpart; and (C) interpretative line drawing of counterpart with names of main veins labelled and vein bow indicated as a dotted line. Scale bars = 2 mm.

Figure 1 .

 1 Figure 1. Glaphyrophlebia victoiriensis sp. nov., holotype MNHN.F.A71360, Gzhelian of Tante Victoire, France: (A) part; (B) counterpart; and (C) interpretative line drawing of counterpart with names of main veins labelled and vein bow indicated as a dotted line. Scale bars = 2 mm.

Figure 2 .

 2 Figure 2. Glaphyrophlebia victoiriensis sp. nov., holotype MNHN.F.A71360, Gzhelian of Tante Victoire, France: (A) wing base, part; (B) wing base, counterpart; (C) region of apex of ScP with main veins labelled. Scale bars = 1 mm (A,B); 0.5 mm (C). urn:lsid:zoobank.org:act:7A5FD9B8-1ACC-4161-9EA7-41089A18A91E Etymology. Named after the type locality Tante Victoire. Type material. Holotype MNHN.F.A71360 (part and counterpart of a nearly complete forewing, with extreme apex missing), stored at Muséum national d'Histoire naturelle, Paris, France. Type locality, formation and age. Tante Victoire, Six-Fours-les-Plages, Var department, France, Gzhelian, Carboniferous. Diagnosis. Forewing characters only. Wing large and elongate, ca. 18 mm long; costal area at base of RP slightly wider than subcostal area; ScP flexed S-line at its apex; vein bow between RA and main stem of M; RP with six main branches; M with four branches; anterior branch of M forked close to M fork; anterior branch of CuA zigzagged with numerous crossveins between anterior and posterior main branches; and posterior branches of CuA zigzagged. Description. No particular trace of coloration; wing ca. 18.0 mm long and ca. 5.7 mm wide; costal space with veinlets mainly simple; ScP ending on C well distad mid-wing; stem R weakly sigmoidal at base; RA with a posterior branch forked; fork of R located slightly distad r-m crossvein; base of RP at 5.0 mm from wing base, second fork of RP slightly distad M fork; first branch of RP simple; second branch of RP forked close to wing margin; third branch of RP forked, anterior branch forked extremely close to dichotomy

Figure 2 .

 2 Figure 2. Glaphyrophlebia victoiriensis sp. nov., holotype MNHN.F.A71360, Gzhelian of Tante Victoire, France: (A) wing base, part; (B) wing base, counterpart; (C) region of apex of ScP with main veins labelled. Scale bars = 1 mm (A,B); 0.5 mm (C).

  anderhalterorum Beckemeyer, 2013 (lower Permian of USA), G. clava Kukalová, 1965 (lower Permian of Czech Republic), G. arnulfi Hörnschemeyer and Stapf, 2001, G. jeckenbachi Hörnschemeyer and Stapf, 2001, and G. rohwedderi Hörnschemeyer and Stapf, 2001 (all three from lower Permian of Germany).

Diversity 2022 , 16 Figure 3 .

 2022163 Figure 3. Glaphyrophlebia pygmaea (Meunier, 1907), holotype MNHN.F.R51519, Gzhelian of Commentry, France. Photograph credits MNHN Gaëlle Doitteau, 2016. Scale bar = 5 mm.

Figure 3 .

 3 Figure 3. Glaphyrophlebia pygmaea (Meunier, 1907), holotype MNHN.F.R51519, Gzhelian of Commentry, France. Photograph credits MNHN Gaëlle Doitteau, 2016. Scale bar = 5 mm.

Figure 4A Diversity

 4A Figure 4A Diversity 2022, 14, x FOR PEER REVIEW 9 of 16

Figure 4 .

 4 Figure 4. Assemblage of wing fragment and plant remains in the same slab (MGM-822H), Gzhelian of El Bierzo, Spain. Photographs: (A) wing fragment of Glaphyrophlebia sp., specimen MGM-822H-1; (B) Oligocarpia gutbieri, MGM-822H-2; (C) Dicranophyllum gallicum, MGM-822H-3; (D) Oligocarpia

Figure 4 .

 4 Figure 4. Assemblage of wing fragment and plant remains in the same slab (MGM-822H), Gzhelian of El Bierzo, Spain. Photographs: (A) wing fragment of Glaphyrophlebia sp., specimen MGM-822H-1; (B) Oligocarpia gutbieri, MGM-822H-2; (C) Dicranophyllum gallicum, MGM-822H-3; (D) Oligocarpia leptophylla (left), MGM-822H-4, and Diplazites unitus (right), MGM-822H-5; (E) Pecopteris daubreei, MGM-822H-6; (F) Diplazites unitus: (1) Sphenopteris sp. aff. mathetii, (2), cf. Odontopteris sp., (3) Sphenophyllum oblongifolium, and (4) specimens MGM-822H-7 to MGM-822H-10, respectively. All stacked images. Abbreviations: RA = radius anterior, RP = radius posterior, ScP = subcostal posterior. Scale bars = 1 mm (A), 1 cm (B-F).

Figure 5 .

 5 Figure 5. Diversity of major blattinopsid clades through time: (A) number of blattinopsid species by stage; and (B) number of species of Glaphyrophlebia and Blattinopsis by stage. Data from https://paleobiodb.org ( last access the 19 October 2022). Abbreviations: C/P = Carboniferous/Permian boundary, Kasi. = Kasimovian, M = Moscovian, Sakm. = Sakmarian, Wor. = Wordian.

Figure 5 .

 5 Figure 5. Diversity of major blattinopsid clades through time: (A) number of blattinopsid species by stage; and (B) number of species of Glaphyrophlebia and Blattinopsis by stage. Data from https://paleobiodb.org (last access the 19 October 2022). Abbreviations: C/P = Carboniferous/Permian boundary, Kasi. = Kasimovian, M = Moscovian, Sakm. = Sakmarian, Wor. = Wordian.

Table 1 .

 1 List of plants from El Bierzo outcrop.

	Allochthonous Flora

•

Dicranophyllum gallicum Grand'Eury, 1877 (Figure

4C

):

Acknowledgments:

We are grateful to the editor and to four anonymous reviewers for their comments and suggestions. C.J. is grateful to Antoine Mantilleri for access to imaging facilities. This work was carried out by C.J. during his Ph.D. The digitalization of the specimen MNHN.F.R51519 was possible thanks to the project RECOLNAT (ANR-11-INBS-0004).

Funding: This research received no external funding.

Institutional Review Board Statement: Not applicable.

Informed Consent Statement: Not applicable.

Data Availability Statement: Not applicable.

Conflicts of Interest:

The authors declare no conflict of interest.