Aaron Kufner

Photograph and illustration of the skull of the new neotype of Aspidosaurus chiton in dorsal view. The skull is an orange-brown color, longer than wide, and largely undistorted.

New paper out today in @zoojlinnsoc.bsky.social for #FossilFriday AKA here's-Bryan's-one-paleo-paper-this-year-to-remind-people-I-still-do-paleo-sometimes: a revision of the #Permian #dissorophid #temnospondyl Aspidosaurus chiton based on a new specimen: doi.org/10.1093/zool... (1/n)

A new metoposaurid (Temnospondyli) bonebed from the lower Popo Agie Formation (Carnian, Triassic) and an assessment of skeletal sorting Metoposaurid-dominated bonebeds are relatively commonplace in Upper Triassic continental deposits with at least ten monodominant, densely-packed bonebeds globally. The biostratinomy of several classic...

Link that works: journals.plos.org/plosone/arti...

Elon Musk: pours tens of millions into a race that has never seen even a fraction of that much money. bribes multiple voters with $1 million checks to vote. offers any Wisconsin voter who proves they voted $50. wears a fucking cheesehead

Wisconsin: votes against his candidate by historic margins

While this site is exceptional insofar as the metoposaurids are concerned, it has so much more to offer in improving our understanding of the paleoecology of the continental early Late Triassic in North America!

16/16

Possible plant fossils including fragments that appear to be stems and a potential root. The lower panel includes fragmentary coprolites that are subrectangular in outline and all white in color.

Last but certainly not least, plants and poops. None of us is a paleobotanist, so take our IDs with a grain of salt. These might represent some of the more complete plants from the Popo Agie, but we'd love to work with someone interested in Triassic plants. And coprolites too...

15/16

Representative unionoid bivalve fossils from the NK bonebed. All of these fossils are preserved as molds of the external surface and appear as smooth ovoid structures with some lineations in red mudstone.

The bivalves from NK have unironically become my favorites because they are a bit of a puzzle. Only external molds on + and - relief! We propose they formed by 1) burial, 2) dissolution of biomineral and retention of outer organic layer, 3) lithification, and 4) loss of organic layer. 🤷‍♂️

14/16

Fish remains from the NK bonebed including a probable fin with an inset showing linear structures interpreted as fin rays (lepidotrichia), a diamond-shaped scale, a tiny toothed element, and a mold and partial fossil of a bone of the gill/skull skeleton called the supracleithrum.

"Fish bits" from within the bonebed including what we think is an almost complete fin. We suggest these are all redfieldiid based on the supracleithrum, but it's possible if not likely there were other ray-finned fish present. We need more complete fish material!

13/16

Two shed teeth from archosauriform reptiles from the NK bonebed that are conical with faint serrations, and a partial phytosaur mandible from above the NK bonebed with a colored in skull showing where the elements in context.

The shed archosauriform teeth are from the bonebed, but this partial phytosaur mandible is from somewhere in the overburden. It's the lowest definitive occurrence of a phytosaur from the Popo Agie aside from some unsubstantiated reports.

12/16

A skull roof of the metoposaurid Buettnererpeton bakeri that evokes memories of Pac-Man ghosts. There are also examples of denticulate palatal plates that form interlocking polygons that would have been embedded in the soft tissue of the palate in life.

Now for the critters! The star of the show is Buettnererpeton bakeri, a metoposaurid species placed in its own genus by @koskinonodon.bsky.social and me a couple years back. That little block with articulated palatal plates (E,F) was found by Bryan when he came out to the site in 2018!

11/16

Tangent: I don't find the "breeding colony die-off" hypothesis in some previous studies particularly convincing because 1) post-breeding die-off is fairly specialized among vertebrates and 2) afaik, it's unknown among any modern amphibians.

10/16

Our interpretation of the depositional setting with getting closer to present from bottom to top. 1) regional view of a floodplain with oxbow lakes and intermeander ponds. 2) local view of a ponded environment (life is good!). 3a) biological cause of death for metoposaurids such as an algal bloom. 3b) abiological cause of death such as seasonal aridity. 4) return to normal and burial of dead individuals.

Still, the cause of death is unknown. I wish we knew what the sediment looks like lateral to the bonebed, but we keep finding bones! If there are mudcracks in the same layer like Site XIII, that would suggest drying, and if not, then it could be biological such as an algal bloom or disease.

9/16

A map of the Nobby Knob quarry. The bones are densely packed, and some specimens are articulated, but this is clearer in the individual field jacket maps included in the supplemental material. A rose diagram in the upper right shows no preferred orientation of the long bones in this quarry.

Different metrics to show how well represented skeletons are at three sites. Estimates for skeletal content were made based on nearly complete articulated skeletons of Dutuitosaurus figured by Dutuit (1976). The first three panels show our preferred method of normalizing the observed number skeletal elements to the expected number based on minimum number of individuals (1 is complete representation, 0 is absent). Note that Nobby Knob has more complete skeletal representation than the other two sites one of which (Site XIII from Morocco) includes articulated skeletons. We think the counts of Site XIII are biased by photographic plates being selected for slabs showing primarily skulls, so not a comprehensive sample of the whole site. The bottom right panel shows a ternary diagram of Voorhies dispersal groups (VDG) and different schema used to assess temnospondyls. Despites differences in the underlying assumptions for which bones are assigned to dispersal potential groups, the conclusions for each sites are roughly the same i.e. more sorted assemblages trend toward overrepresentation of VDG III.

So is Nobby Knob more of the same or is it different?

It's different! Nobby Knob exhibits more even representation of the skeleton than two other bonebeds analyzed by us and likely than both Lamy and Rotten Hill (although raw count data were not accessible for these two sites).

8/16

A similar depositional scenario was suggested for the Rotten Hill bonebed in Texas by the same group of workers (not imaged for brevity). So no North American metoposaurid MMAs appear to be deposited in low energy settings like a drying pond.

7/16

The newly prepared slab NMMNH block 41 from Rinehart et al. (2024). This slab exhibits complete disarticulation and clear overrepresentation of large flat bones, but it also shows some smaller elements such as ribs and intercentra not completely removed.

Three rose diagrams showing the orientation of long bones from NMMNH block 41 from Rinehart et al. (2024). Note the strong alignment of long bones suggestive of unidirectional flow influence during deposition.

TL;DR: Several studies from workers at NMMNHS have demonstrated that the Lamy quarry has undergone sorting and some transportation and is likely the result of a sheetflooding event.

📸 Rinehart et al. (2024) a newly prepared slab from Lamy and the alignment of long bones

6/16

Romer initially interpreted the Lamy quarry as a "drying pond" scenario, but subsequent workers suggest that this is an oversimplification. They use several lines of evidence looking at sediment, long bone orientation, skeletal representation, etc. If you want to know more, we cited them!

5/16

The Harvard slab of the metoposaurid Anaschisma browni from the Lamy amphibian quarry in New Mexico. This slab shows a strong overrepresentation of skulls and plate-like pectoral girdle elements (clavicle and interclavicle) suggestive of loss of small early dispersing elements such as some parts of the vertebrae (neural and hemal arches) and small elements in the limbs (metapodials and phalanges).

Previous metoposaurid MMAs from North America are all high energy deposits and are highly sorted so that most remains that...remain are highly immobile elements such as large flat skull roofs, clavicles, and interclavicles.

📸 Romer (1939) the slab at MCZ from the Lamy amphibian quarry in NM

4/16

The stratigraphic and paleographic context of Nobby Knob from the Carnian-aged (>230 Ma) purple unit of the Popo Agie Formation of Wyoming in paleoequatorial Pangea. Ten other mass mortality assemblages dominated by metoposaurids are shown on the map along with three other assemblages rich in metoposaurid remains but with significant input of other taxa such as phytosaurs.

Metoposaurid bonebeds are relatively common (as far as vert paleo assemblages go). We named this one Nobby Knob, and it is the first unequivocal mass mortality assemblage (MMA) of metoposaurids from the Popo Agie Fm.

3/16

The local stratigraphy of about 10m of strata and site photos of Nobby Knob.

Here we describe the taphonomy of a #metoposaurid bonebed from the Late Triassic Popo Agie Formation of Wyoming. I have been presenting on this site for several years at conferences, so I'm thrilled to finally have it published!

2/16

New publication! My first dissertation chapter is now published in @plosone.org with @paleobadger.bsky.social, @calamanderso.bsky.social, Hannah Miller, Max Deckman, and Brandon Price. Any images not credited below are from this paper.

doi.org/10.1371/jour...

@uwmadscience.bsky.social

1/16

A pretty solid couple of days for publishing some of my dissertation work! 🦎Our description of Milleropsis pricei, a late Permian reptile from South Africa, is out!

🚨Rethink what you know about 'parareptiles'🚨

Link here: doi.org/10.1098/rsos...

Image contains a small theropod dinosaur checking out a dead amphibian in a wetland forested ecosystem

I am incredibly excited to share our new Open Access publication in the @zoojlinnsoc.bsky.social that was released today. Please welcome *Ahvaytum bahndooiveche*, a new species of sauropodomorph(?) dinosaur from the Popo Agie Formation, WY, USA. tinyurl.com/3zx7s3mx (1/x)

Our anatomical description of Hapsidopareion is out in Papers in Palaeontology! Thanks to collaborators and mentors @gondwannabe.bsky.social, Arjan Mann, and @hanssues.bsky.social and ISU undergraduate coauthors for their massive help with segmentation! 😄https://doi.org/10.1002/spp2.1610

No need to see the rest of this. A dead #metoposaurid is enough for me

Sneak peek of an illustration of a new paper coming out tomorrow

Sneak Peek
Tomorrow. New Paper. New Taxon. New illustration

Stay tuned

#paleoart #sciart #paleontology

Artistic reconstruction of Stenokranio by Frederik Spindler. A rather stout temnospondyl is depicted as standing up, facing to the right and with mouth agape in a sort of smile. Its large tongue and many teeth are visible. The torso and limbs are round and cylindrical, with webbed feet. The eyes face upward and to the sides, with faint cranial ridges from the skull visible through the skin. Associated with Werneburg et al. (2024)

Known and inferred distributions of temnospondyls across Pangea during the Middle-Late Triassic based on the combination of empirical data and this study's modeling. In the Middle Triassic, capitosaurs have the widest range, with trematosaurs being more restricted to central Europe and plagiosaurs to north-central Europe. In the Late Triassic, metoposaurids have the widest range, with capitosaurs and plagiosaurids restricted to central/north-central Europe. From Moreno et al. (2024)

Composite reconstruction of the skull of the Late Triassic stereospondyl Ninumbeehan dookoodukah via CT analyses of multiple skulls. The skull is longer than wide and generally triangular, though with a blunted tip of the snout. In lateral view, it angles upwards posteriorly such that the back of the skull is much taller than the snout. The typical interpterygoid vacuities of temnospondyls occur on the palate. The lower jaw is also reconstructed, featuring the typical suite of elements found in temnospondyls. From So et al. (2024)

The holotype skull of the early Permian eryopid Clamorosaurus nocturnus from Russia. The skull is incomplete anteriorly and flattened, with associated postcrania skrewn behind it. Typical eryopid features like a tall suborbital bar and broad posterior skull are discernible. From Werneburg & Witzmann (2024)

For the first #FossilFriday of 2025, here's my annual thread looking back on the #temnospondyl research that came out last year! In general, papers were skewed towards anatomical descriptions of specifically European taxa that were predominantly from Triassic deposits.

🧵👇

(1/30ish)

A nice figure of another junior synonym of Anaschisma browni, "Koskinonodon princeps" from the Popo Agie Fm of Wyoming for #FossilFriday. For some reason, a chunk that could be reattached on the margin of the left orbit was left out and substituted with some filler

@akufner.bsky.social & Gee, 2021

Screenshot of a figure from Rinehart et al. (2024) that purports to show the holotype of "Koskinonodon perfectum" - in fact this specimen, housed in the University of Missouri, is from Wyoming and is the holotype of "Koskinonodon princeps". Both are synonyms of Anaschima browni.

Contra the latest crap paper from Lucas & co., MU 537 from Wyoming is not the holotype of this taxon but rather of "Koskinonodon princeps," which they would know if they had read, and heaven forbid, cited, @akufner.bsky.social & Gee (2021): doi.org/10.1080/0272...

Triptych showing Ninumbeehan in its palaeoenvironment across seasons. First:Ninumbeehan resting on the edge of a river with a low water table as the rainy season ends. Second: A small community of Ninumbeehan in their estivation burrows during the peak of the arid season. Third: The beginning of the rainy season triggering a mass emergence from their estivation burrows (some individuals would not have made it through the estivation period and would have died in their burrows)

Last week saw the description of a REALLY cool burrowing temnospondyl from Late Triassic North America called Ninumbeehan dookoodukah

I was lucky enough to be commissioned to illustrate this amazing species in a triptych showing it in its environment across season