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Posts by Xavier Jenkins

Crazy! I didn’t realize they had that impressive of a range. I was lucky enough to see a few growing up in southern Arizona 🌵

1 week ago 0 0 1 0
Durophagous Palatobaena, found to both sides of the extinction horizon, sitting on an extinct Basilemys with the mandatory T. rex skull in the background. Art by Joschua Knüppe

Durophagous Palatobaena, found to both sides of the extinction horizon, sitting on an extinct Basilemys with the mandatory T. rex skull in the background. Art by Joschua Knüppe

New paper: royalsocietypublishing.org/rsbl/article...

Guilherme & I investigate dietary selectivity on turtle K/Pg extinction - durophagous turtles have higher survivorship probability. Beautiful art by @joschuaknuppe.bsky.social

4 weeks ago 89 34 2 2
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A couple years ago, we reported one from even further south, in Namibia. A giant early tetrapod with affinities to species of tetrapod from the earliest Carboniferous, which we named Gaiasia. But is Gaiasia unique only to the far south, or was it part of a Gondwana-wide fauna?

1 month ago 39 5 1 1
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New paper! How weird could Permian animals get? Turns out, pretty weird. Meet the stem tetrapod Tanyka amnicola from the Pedra de Fogo Formation of northeast Brazil

royalsocietypublishing.org/rspb/article...

1 month ago 898 161 40 19

See Jason’s thread here for some interesting points bsky.app/profile/jdpa...

2 months ago 1 0 0 0
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Carboniferous recumbirostran elucidates the origins of terrestrial herbivory - Nature Ecology & Evolution A new species of pantylid microsaur from the Late Carboniferous of Cape Breton Island, Nova Scotia, has teeth with dental occlusion consistent with herbivory, indicating an early transition to this co...

New pantylid just dropped 👀 www.nature.com/articles/s41...

2 months ago 9 2 1 0
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Rauisuchus, the one who started it all, a friend-sized fella

(do not trust any other repurposed past skeletal reconstruction of this animal)

2 months ago 32 9 1 0
Skull of Scyllacerta, reconstructed based on scans of four nearly complete skulls.

Skull of Scyllacerta, reconstructed based on scans of four nearly complete skulls.

Introducing a new Permian reptile: Scyllacerta creanae

With a tympanic fossa on the quadrate and no lower temporal bar, Scyllacerta challenges long-standing ideas about when-and-how hearing evolved in reptiles 🦎👂

🔗 doi.org/10.1111/pala...

2 months ago 82 38 2 3
Graphic illustrating the reconstruction process for Scyllacerta creanae (SAM-PK-K7710). The holotype aggregation specimen (left) comprises four skulls and at least six nearly complete skeletons preserved in lifelike positions. Using synchrotron micro-CT scans of the skulls, the bones could be segmented, digitally isolating them from the matrix and allowing their full morphology to be studied in detail (top center). Combining information from all four skulls, a reconstructed version could be assembled, depicting the likely life appearance (center, with each bone in a distinct color). This reconstruction can be used to make line drawings for science communication and skeletal reconstructions (bottom center). These reconstructions were the basis for a detailed life restoration of the head of Scyllacerta (bottom right, by @LiterallyMiguel). Despite its incredibly small size (top right, compared to a human hand), the known individuals were likely nearing full maturity.

Graphic illustrating the reconstruction process for Scyllacerta creanae (SAM-PK-K7710). The holotype aggregation specimen (left) comprises four skulls and at least six nearly complete skeletons preserved in lifelike positions. Using synchrotron micro-CT scans of the skulls, the bones could be segmented, digitally isolating them from the matrix and allowing their full morphology to be studied in detail (top center). Combining information from all four skulls, a reconstructed version could be assembled, depicting the likely life appearance (center, with each bone in a distinct color). This reconstruction can be used to make line drawings for science communication and skeletal reconstructions (bottom center). These reconstructions were the basis for a detailed life restoration of the head of Scyllacerta (bottom right, by @LiterallyMiguel). Despite its incredibly small size (top right, compared to a human hand), the known individuals were likely nearing full maturity.

Very excited to share Scyllacerta creanae, a new Permian stem-reptile from South Africa known from an aggregation of several individuals. This specimen provides unprecedented detail regarding the anatomy of the early reptile skull. 🦎

(1/🧵)

2 months ago 46 17 1 0
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The first page of the paper described in the post.

The first page of the paper described in the post.

First paper of 2026 is out for #FossilFriday, and the first of probably several ornithischian papers over the next interval. Here my coauthors and I describe some tantalizing bits that suggest that ornithischian diversity in the Morrison Formation is higher than previously recognized.

2 months ago 18 9 1 0
A small bit of grey rock containing the entwined and overlapping skeletons of several small lizard-like reptiles. On white foam with a scale bar.

A small bit of grey rock containing the entwined and overlapping skeletons of several small lizard-like reptiles. On white foam with a scale bar.

This #FossilFriday we are pleased to have published the new younginid taxon Scyllacerta from the late Permian of South Africa 🇿🇦
This beautiful aggregation has the holotype and has been in the literature for 30 years as “juvenile Youngina”.
Photo taken before scanning at the @esrf.fr

2 months ago 56 18 1 1
Line drawing of Scyllacerta in numerous anatomical views, done by paleontologist Cy Marchant

Line drawing of Scyllacerta in numerous anatomical views, done by paleontologist Cy Marchant

Permian reptiles keep challenging what we know about reptile origins 🦎👂 More to come!

BTW- the CT segmentation, reconstructions, and line drawings were done by ISU undergraduate Cy Marchant @slvrhwk.bsky.social…. He’d be a great fit for any paleo lab! 👀

2 months ago 14 2 0 0

At the same time, we see a suite of changes:
• loss of the lower temporal bar
• origin of a cephalic condyle
• increased cranial mobility

This raises the possibility that tympanic hearing and early cranial kinesis evolved together… much earlier than previously thought.

2 months ago 7 0 1 0
The holotype of Youngina, a little worse for wear but bearing a conspicuous emargination on the back of its overly-prepped quadrate…

The holotype of Youngina, a little worse for wear but bearing a conspicuous emargination on the back of its overly-prepped quadrate…

We suspect this anatomy was missed due to historical preparation techniques, especially in classic specimens like the Youngina holotype. 🔎

Newly discovered (and better-prepared) Youngina specimens all show the same feature….something that was even hinted at by Gow in the 70s….

2 months ago 7 0 1 0
Phylogeny of early reptiles showing the placement of Scyllacerta as an early Younginid and mapping the appearance of the tympanic fossa, loss of lower temporal bar, and appearance of the cephalic Condyle on the quadrate in these taxa.

Phylogeny of early reptiles showing the placement of Scyllacerta as an early Younginid and mapping the appearance of the tympanic fossa, loss of lower temporal bar, and appearance of the cephalic Condyle on the quadrate in these taxa.

That question led Valentin Buffa @valentinbuffa.bsky.social and I to re-examine all non-saurian neodiapsid taxa.

And we found tympanic fossae in more places than expected…. Even Youngina!

2 months ago 9 2 1 0
A close of a monitor lizard (Komodo dragon) with a visible external ear towards the right

A close of a monitor lizard (Komodo dragon) with a visible external ear towards the right

That’s a big deal because tympanic ears were thought to be restricted to living reptiles, and absent in Permian stem-reptiles.

So was Scyllacerta a weird outlier… or had something been overlooked in other fossil reptiles?

2 months ago 9 0 1 0
Zoom in showing the middle ear, tympanum, and occiput of Scyllacerta

Zoom in showing the middle ear, tympanum, and occiput of Scyllacerta

But the most exciting result?

Scyllacerta preserves a tympanic fossa on the quadrate.

This strongly suggests the presence of a tympanic (impedance-matching) ear. 👂

2 months ago 9 1 1 0
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The scans made it immediately obvious that Scyllacerta is a distinct taxon.

It has a remarkably tooth-rich palate, including teeth extending onto the braincase (!) 🦷 🧠

2 months ago 8 0 1 0

During my PhD, I noticed several aspects of its anatomy that didn’t match Youngina at all.

So, with colleagues from Iziko Museums and University of the Witwatersrand, we CT-scanned the specimen at the European Synchrotron Radiation Facility. 🇫🇷

2 months ago 8 0 1 0
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Biostratigraphic map of the Karoo basin in South Africa, showing where in the section Scyllacerta and other younginids are from.

Biostratigraphic map of the Karoo basin in South Africa, showing where in the section Scyllacerta and other younginids are from.

Even more recently, the holotype of Scyllacerta was referred to newly named Akkedops bremneri on the basis of them being from the same locality…..

But they are separated by hundreds of miles and millions of years in stratigraphy…. As are the other specimens to referred to Akkedops 👀 🤷‍♂️

2 months ago 10 1 1 0
The holotype aggregation in multiple views, with numerous individuals visible

The holotype aggregation in multiple views, with numerous individuals visible

Scyllacerta was first discovered in the early 1990s and originally identified as a juvenile aggregation of Youngina capensis.

But it was older (~257 Ma vs ~253 Ma) and from a different assemblage zone in South Africa (sus).

2 months ago 8 0 1 0
Skull of Scyllacerta, reconstructed based on scans of four nearly complete skulls.

Skull of Scyllacerta, reconstructed based on scans of four nearly complete skulls.

Introducing a new Permian reptile: Scyllacerta creanae

With a tympanic fossa on the quadrate and no lower temporal bar, Scyllacerta challenges long-standing ideas about when-and-how hearing evolved in reptiles 🦎👂

🔗 doi.org/10.1111/pala...

2 months ago 82 38 2 3
Top left: photograph of a grey slab containing multiple fossils, with vertebral columns clearly running vertically (SAM-Pk-K7710). This is a group of six Scyllacerta creanae individuals, including the holotype, a late Permian neodiapsid reptile from South Africa (scale bar at top right is 2 cm). Bottom right: a computer reconstruction of the skull based on three of the individuals in the fossil block. Scale bar at top right is 5 mm.

Top left: photograph of a grey slab containing multiple fossils, with vertebral columns clearly running vertically (SAM-Pk-K7710). This is a group of six Scyllacerta creanae individuals, including the holotype, a late Permian neodiapsid reptile from South Africa (scale bar at top right is 2 cm). Bottom right: a computer reconstruction of the skull based on three of the individuals in the fossil block. Scale bar at top right is 5 mm.

The origin of the tympanic fossa in reptiles revealed by a late Permian neodiapsid: new species Scyllacerta creanae onlinelibrary.wiley.com/doi/10.1111/... #FossilFriday @semifossorial.bsky.social @morphobank.bsky.social

2 months ago 31 13 0 0

Come work with the vertebrate paleontology team at the American Museum of Natural History in NYC this summer!

REU Students will have the opportunity to study and reconstruct the skulls of Permian and Triassic reptiles 😃

Reach out to me if you have any questions (: Apply by the 31st!!

3 months ago 18 9 0 1
The petrosal and bony labyrinth of extinct horses (Perissodactyla, Equidae) and their implications for perissodactyl evolution Perissodactyla, or odd-toed ungulates, are represented today by 16 species of rhinoceroses, tapirs, and horses. Perissodactyls were much more diverse in the past, having a rich fossil record spanning ...

peerj.com/articles/204...
My first mammal project, which I started as an REU intern at the AMNH is finally published! Huge thanks to my mentors and coauthors on this project for all their help, and to the reviewers for their comments and suggestions!

3 months ago 9 1 0 0
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more wiki comms and stuff

4 months ago 58 15 1 0

There may be a way to skirt this requirement by sneaking in a zip file, but this isn’t optimal obviously

4 months ago 1 0 1 0
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There’s a way to batch upload, but I think you need permission…. It’s a huge pain without it.

I feel personally punished for working on complete skulls 💀

4 months ago 1 0 1 0

Check the paper out above👆 to learn more!!

Keep an eye out for future work by @valentinbuffa.bsky.social, myself, and others on early reptiles…. 🦎🐍🐢

Some exciting stuff inbound! (:

5 months ago 4 0 0 0
A cladogram of early reptile relationships showing the origin of important anatomical features in the foot of these reptiles

A cladogram of early reptile relationships showing the origin of important anatomical features in the foot of these reptiles

Our postcranial observations, specifically on the foot, suggests that many features of the modern reptile hindlimb are actually present in their closest fossil relatives!

You heard it folks: milleretids are *also* postcranially very neodiapsid-like 😃

5 months ago 6 0 1 0