Aaron Kufner (@akufner.bsky.social)

Aaron Kufner

@akufner.bsky.social

PhD Candidate at UW Madison geoscience. Triassic ecosystems, temnospondyls, and the odd dinosauriform

188 followers 225 following53 posts

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@akufner.bsky.social

This one has been a long time coming! I'm happy to share that another chapter of my PhD has been published! In this one, I'm shaking up the taxonomy of North American metoposaurids. This work was largely done in museum collections, and more on that below. peerj.com/articles/217...

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Jason Anderson

@jsanderso.bsky.social

New paper day! CT scans reveal much new information about the Mesozoic aged horned frog Hungarobatrachus. Well done Alfred and team!

academic.oup.comA frog with horns in the Late Cretaceous: new information on Hungarobatrachus szukacsi (Neobatrachia: Anura)Abstract. The Late Cretaceous Hungarobatrachus szukacsi from Hungary is the only Mesozoic neobatrachian species known in Laurasia. Previously represented b

Aaron Kufner reposted

Xavier A. Jenkins

@semifossorial.bsky.social

Out today: We show that Westlothiana lizziae or "Lizzie," described 35 years ago as the world's oldest reptile - is not a stem amniote at all, but a stem tetrapod. www.nature.com/articles/s41...

Aaron Kufner

@akufner.bsky.social

It's a great week for temnospondyl research!

Thomas R. Holtz, Jr.@arctomet.bsky.social

Jeanerpeton mazonensis, gen. et sp. nov.: a new, exceptionally preserved, late Carboniferous amphibamiform from the Mazon Creek Lagerstätte, Illinois: Journal of Vertebrate Paleontology: Vol 0, No 0 - Get Access www.tandfonline.com/doi/full/10....

tandfonline.comJeanerpeton mazonensis, gen. et sp. nov.: a new, exceptionally preserved, late Carboniferous amphibamiform from the Mazon Creek Lagerstätte, IllinoisThe Mazon Creek fossil assemblage has provided the earliest fossil records of several important early tetrapod lineages, including the oldest dissorophoid temnospondyl, Amphibamus grandiceps. Recen...

Loss of public awareness can put these scientifically and culturally important collections in precarious positions and may even result in the loss of reproducibility of scientific works in extreme cases.

Aaron Kufner

@akufner.bsky.social

TL;DR: We may have been underestimating the species diversity of North American metoposaurids. Figuring out their species is still pretty hard. Maybe it's better to put each species in its own genus so we aren't always flip-flopping generic names. Support your local museums and historical societies.

Lastly, all of this work was conducted through museum collections, and I'd be remiss not to say something at this time of uncertainty in several museums' futures.

Aaron Kufner

@akufner.bsky.social

While the public-facing side of a museum is only a small fraction of its purpose, it is vital to broader public awareness of many museums and their missions. Indeed, one of the museums that I visited in Texas for this work has now been closed to the public for more than a year.

As a result of this uncertainty in interspecies relationships, I ended up naming new genera to accommodate the species once referred to Anaschisma browni because I could not firmly establish them in an existing genus without synonymizing other genera that are generally considered distinct.

Aaron Kufner

@akufner.bsky.social

These results are more in line with some older schools of thought by authors like Colbert and Imbrie (1956) who suggested Anaschisma browni from WY is distinct from other metoposaurids in North America based on their "biometric" analyses (what we'd now call linear or traditional morphometrics).

Alright, I'm going to try and keep the rest of this short. If this interests you, I'd recommend reading the article, but then again, I'm a little biased. So what about the results of the phylogenetic analysis? Well, it's consistent with previous analyses of metoposaurids which is good(?)

Aaron Kufner

@akufner.bsky.social

Once again, there is mostly no resolution for interspecies relationships of metoposaurids. Huzzah! Previous results have been replicated. Science works. BUT there are reasonably well resolved clades of specimens of the species B. bakeri, A. gregorii, and P. howardensis.

So where are the adults? Well, they may have been sitting in front of us all along. I tentatively referred UCMP 27051 to Apachesaurus gregorii based on the abrupt curvature of the temporal LLS toward the squamosal (though not clearly passing onto it) and a narrow cultiform process.

Aaron Kufner

@akufner.bsky.social

Unfortunately, I could not establish this referral for other specimens from the same site. So if you have large Norian-aged metoposaurids, take a closer look at them! And hit me up if anything stands out!

But importantly, the discontinuous cranial LLS present in the type locality specimens (and another small referred specimen 📸 here) of Apachesaurus gregorii may be an indicator of juvenile ontogenetic status.

Aaron Kufner

@akufner.bsky.social

Underdevelopment of the LLS in Apachesaurus has been used to infer that this species may have been "more terrestrial", but read the paper to see why I think this is not the case.

Lateral line canals in ray-finned fish tend to following a specific sequence that concludes after or near the end of a larval stage resulting in the integration of the canal neuromasts into canals. But these begin formation as a series of disconnected segments. 📸 Pastana et al. (2019)

Aaron Kufner

@akufner.bsky.social

Is a modification to this developmental sequence responsible for the presence of sulci rather than roofed canals among stereospondyls? And what other kinds of modifications to this developmental sequence may have been possible? I would argue definitively...Probably? More work needs to be done!

I was fully on board with the idea that Apachesaurus may actually represent a juvenile of what was at the time called Anaschisma, and to my surprise, I found solid evidence for its validity including a unique configuration of the cranial lateral line sulci, see UCMP 63846 from the type locality.

Aaron Kufner

@akufner.bsky.social

The extent of the temporal sulcus onto the squamosal seems to be autapomorphic (at least among metoposaurids, and also present in the holotype), but the discontinuity of this lateral line sulcus (LLS) is worth exploring. It may be related to development of the lateral line system.

With my guilt now acknowledged, let's get on to what I consider the most interesting part of this work: Apachesaurus gregorii.

Aaron Kufner

@akufner.bsky.social

There has been some back and forth about the ontogenetic status of referred specimens of Apachesaurus because all specimens of this taxon are small-bodied. Histology of small Apachesaurus-like intercentra suggests very convincingly that these are juvenile forms. peerj.com/articles/3183/

The second I am calling Tecovaserpeton perfectum, and it is known (not surprisingly) primarily from the Tecovas Fm in TX. Its holotype was originally named Buettneria perfecta by Case in 1922, and it is a shockingly "perfect" specimen aside from being squished and missing the tabular horns.

Aaron Kufner

@akufner.bsky.social

At this point, I have to apologize to all museum curators, collection managers, and exhibit designers who recently changed their Buettneria signs and labels to Anaschisma. Give it another 5-10 years to see how this plays out before making another change 😅

The first is one I am calling Paranaschisma howardensis. Buettneria howardensis was originally described in 1945 by Sawin based on the material from Otis Chalk Quarry 3 in TX. It has bounced around in being considered valid or invalid, but I was able to find a handful of apomorphies for this taxon.

Aaron Kufner

@akufner.bsky.social

This is probably a good time to allude to but not rehash the taxonomic kerfuffle of Buettneria from the mid-2000s. The occupation of the name Buettneria certainly did not simplify the taxonomic history of these metoposaurids. We see you Buettneria maculiceps (although I've literally never seen it).

The results were a little surprising to me since I was able to find evidence that Anaschisma browni may have been a bit of a wastebasket and ended up restricting that species to just specimens from the Popo Agie Fm of WY. (And a rare lateral view of a metoposaurid for your viewing pleasure)

Aaron Kufner

@akufner.bsky.social

What about the rest of the specimens previously referred to Anaschisma? Well, there seem to be at least two, maybe three, species in this boat. Which all already have pre-existing type material.

Recent redescriptions of several metoposaurid taxa including Anaschisma browni (left) and Buettnererpeton bakeri (right) and character matrices attempting to discern metoposaurids relationships made this work reasonably straightforward.

Aaron Kufner

@akufner.bsky.social

I added 29 new characters and modified some pre-existing ones to the matrix of Gee and Kufner (2022; some of these additions were splitting of compound characters), and I scored over 50 specimens from firsthand observation and seven from the work of Sulej (2007).

One interesting example is Metoposaurus krasiejowensis described by Sulej (2007) which exhibits variation in the contribution of the lacrimal to the orbital margin. This character has been used extensively for taxonomic differentiation, so seeing variation within a population is...disconcerting.

Aaron Kufner

@akufner.bsky.social

So what did I do? I went around to museum collections that hold type specimens and numerous referred specimens of metoposaurids from North America and documented as much of the cranial morphology as I could. (See current profile pic for an example 🙂)

In this study and as the title suggests, I set out to reevaluate the taxonomy of North American metoposaurids in light of studies from the last two decades documenting intraspecific variation in populations of metoposaurids known from bone beds.

Aaron Kufner reposted

Xavier A. Jenkins

@semifossorial.bsky.social

28 May

Our paper on turtle origins is finally out in Current Biology, with two major implications for our understanding of reptile evolution 🐢 #Paleontology #Turtles #Evolution www.cell.com/current-biol...

Aaron Kufner

@akufner.bsky.social

23 Feb

In my limited interactions with Hans, he was personable, kind, and encouraging. A true powerhouse in the Triassic and vertebrate paleontology as a whole. And his humor and love for cats was infectious. He will be sorely missed.

Aaron Kufner reposted

BatmanelVisigodo

@batmanelvisigodo.bsky.social

25 Nov 2025

#temnovember2025 day 25 :Buettnererpeton Day 25 and now its time for #Buettnererpeton, a thin skull #metoposaur from the late #Triassic of northamerica #Paleoart #sciart #amphibian #temnospondyl #metoposaurus

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Robert Evans (the Only Robert Evans)

@iwriteok.bsky.social

2 Apr 2025

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