Category: New Publications

New publication ( Description of the metoposaurid Anaschisma browni from the New Oxford Formation of Pennsylvania; Gee & Jasinski, 2021, Journal of Paleontology)

5/4/2021

Title: Description of the metoposaurid Anaschisma browni from the New Oxford Formation of Pennsylvania
Authors: B.M. Gee, S.E. Jasinski
Journal: Journal of Paleontology
DOI: 10.1017/jpa.2021.30

The amazing art above was done by Sergey Krasovskiy; you can find his DeviantArt profile here and his Twitter here! The number of metoposaurids is not random - we know that there were at least two individuals preserved at the site based on the number of duplicate elements from the site.

General summary: This study provides the first detailed description of metoposaurid temnospondyls from Late Triassic deposits in Pennsylvania. Metoposaurids are well-known for their widespread distribution in the Late Triassic, including in the southwestern U.S., but they have a much scarcer record west of Texas. The east coast in particular was geographically closer to other regions that preserve metoposaurids that have drifted apart over the millenia, like northern Africa and western Europe. The east coast is also the only region in North America where a large-bodied temnospondyl that isn't a metoposaurid is known from (this pattern of metoposaurid exclusivity is not observed anywhere else with decent sampling). While previous people have mentioned the Pennsylvania material and ID'd it, they never provided good figures or explicit justification for their ID, so essentially any reader was left to take them at their word. We formally describe the material, identifying it to Anaschisma browni (best known from Arizona, New Mexico, Texas, and Wyoming), which is not the same species that a metoposaurid from Nova Scotia belongs to, and discuss the importance of providing proper documentation and justification for taxonomic identifications (which are fluid hypotheses, not static facts). While the east coast is much more fossil-poor (this is definitely the best metoposaurid material from anywhere in North America west of Texas), it may also be the only region that preserves the transition from a diverse large-bodied temnospondyl assemblage to one that is entirely dominated by metoposaurids.

New publication ( New information on the dissorophid Conjunctio (Temnospondyli) based on a specimen from the Cutler Formation of Colorado, U.S.A.; Gee et al., 2021, JVP)

3/9/2021

Title: New information on the dissorophid Conjunctio (Temnospondyli) based on a specimen from the Cutler Formation of Colorado, U.S.A.
Authors: B.M. Gee, D. S Berman, A. C. Henrici, J.D. Pardo, A. K. Huttenlocker
Journal: Journal of Vertebrate Paleontology
DOI: 10.1080/02724634.2020.1877152

General summary: Much of the early evolution of the armoured dissorophoids, the dissorophids, remains poorly known. Many taxa are what we call 'wildcards,' which means that they shift around a lot in phylogenetic analyses between different studies and can sometimes have a destabilizing effect on the entire tree. One of these longtime wildcards is Conjunctio, a taxon first reported from New Mexico, that has a mixture of primitive and derived features, something that often leads to 'wildcard' status. Like many other dissorophids, Conjunctio is essentially known from one very spatially restricted region (part of New Mexico in this case). Is this a real phenomenon (endemism) that perhaps explains why there are so many different dissorophid taxa, or is it a bias in the fossil record? Our study reports Conjunctio from Colorado for the first time, a region that is very light on temnospondyl fossils in general. While spatially separated, the fossil occurs in the same general stratigraphic horizon as the previously known specimens (the Cutler Formation). It suggests that some of these less sampled Four Corners states might have been home to widely dispersed dissorophids (see also: Platyhystrix).

The Red River

The Red River is a mostly east-west oriented, eastward-flowing indirect tributary of the Mississippi River, stretching from the Texas Panhandle all the way to Louisiana (over 1,350 miles). It forms the border between Texas and Oklahoma (hence where the "Red River Rivalry" in collegiate football between University of Texas and the University of Oklahoma derives from), two of the most historically productive states for early Permian tetrapod fossils (especially the famed Texas redbeds). Much of our record of North American temnospondyls from this time comes from these two states, with more minor contributions from New Mexico, Utah, and Ohio. Dissorophids, the armoured dissorophoids, are among the best known taxa from these redbed deposits, and in many instances, the entire record of a given species is restricted to one or two states. Whether this is an artifact of the fossil record or an accurate representation of a truly restricted geographic range is often unclear; many taxa are in fact known from only one specimen or one site (the two species of Cacops below are examples; figures from Gee & Reisz, 2018 and Anderson et al., 2020).

Land of Enchantment

Conjunctio multidens (reconstruction from Schoch & Sues, 2013) is one such dissorophid, known only from two sites (but the same county) in New Mexico. Although New Mexico and Texas are adjacent states, their faunal assemblages were somewhat different, a result of regional geography no longer present that would have created some degree of spatial segregation. Other examples can be found in the trematopids Anconastes and Ecolsonia, only found in New Mexico, or the dissorophid Broiliellus reiszi, which differs starkly from other members of the genus that are known from Texas. Because the Texas redbeds have been so extensively sampled, with at least a dozen other dissorophids known, it can be reasoned that indeed Conjunctio also did not occur in Texas. But does that mean that it was only found in New Mexico? Not necessarily. The rest of the Four Corners region and the midcontinent is less well-explored, probably because the early Permian deposits that yield tetrapod fossils are less extensive. One of the well-known productive localities in the Four Corners region is in the Placerville area in Colorado, where the Cutler Formation (also found in New Mexico) is several hundred meters thick. First reported by Lewis & Vaughn (1965), the assemblage preserves one of the few sails of the dissorophid Platyhystrix (below on right), the holotype of Diadectes sanmiguelensis, a diadectomorph stem amniote (below on left), and a number of other tetrapods also known from other redbeds deposits. Synapsid fans may also know this as the type locality for the sphenacodontid Cutleria.

Odd man out

Core members

Dissorophids have historically been divided into three or four main groups, which is reflected in the taxonomy of Schoch & Milner (2014) and shown in the figure from Schoch (2012) on the left. Platyhystricines are identified by the hyperelongation of the spine and a single osteoderm closely adhered to the spine (or maybe no osteoderm, just an ornamented spine), as in Platyhystrix (but also Astreptorhachis). Aspidosaurines are also largely defined by the postcranial skeleton due to a paucity of cranial material; their osteoderms are distinctly shingle-shaped and attach to a spine that expands at the top to meet the underside of the osteoderm. The two derived groups, dissorophines and eucacopines are both represented by abundant cranial material and have markedly different skull morphologies that set them apart. One of the main challenges has been resolving the position of various dissorophids that don't clearly fit into these categories, which is predictable because evolution doesn't just hop been discrete bins in the blink of an eye.

Conjunctio multidens, the only species of Conjunctio, has long been one of these taxa that doesn't clearly fit into the existing dissorophid categories (see figures of C. multidens from Schoch & Sues, 2013, on the right). It has a weird mixture of plesiomorphies (e.g., high marginal tooth count, single series of narrow osteoderms) and apomorphies (e.g., rectangular postorbital, shortened posterior skull table) that defy clear placement within any of the established clades. The intuitive proposal is that it represents one of the earliest diverging members of one of these clades (a sort of 'transitional' form), combining primitive and derived features in a unique way. Animals like this tend to be troublesome in phylogenetic analyses.

Terminology: While 'transitional form' or 'transitional fossil' is a commonly used term that even the general public knows (e.g., Archaeopteryx), scientists are moving away from it because it's misleading, suggesting that one animal directly turns into another (one of the most common misconceptions about evolution). In fact, this very rarely occurs (a process called anagenesis), and it does not capture major transitions like the theropod-bird transition or the fish-tetrapod transition. Instead, continual splitting of new species that go extinct is what gradually leads to a shift in a group's anatomy. A given species' suite of features may be transitional insofar as it captures part of this shift, but the species or individual itself is not.

Agree to disagree

Comparison of different phylogenetic results with Conjunctio. Boxes refer to dissorophid subfamilies: green = cacopines, blue = dissorophines.

As one might expect from a taxon with a weird mixture of features, there is no agreement on the position of Conjunctio in phylogenetic analyses of dissorophids, as summarized on the right. Historically, the phylogeny did not support that they were conspecific (expected recovery as exclusive sister taxa), as they were frequently scored separately due to uncertainty over Carroll's referral (the referred specimen was called the "Rio Arriba Taxon"). It doesn't really help that the holotype (C-D) and the much smaller referred specimen (A-B) differ from each other in cranial proportions, somewhat questioning whether they are actually the same taxon (since Bob Carroll created Conjunctio in 1964). You don't have to be a paleontologist to look at the two specimens above and kinda wonder whether they are actually the same (or whether the bottom one can be said to be much of anything really). Sometimes both specimens were recovered as eucacopines (Holmes et al., 2013), sometimes only one was recovered as a eucacopine (Schoch, 2012), sometimes Eucacopinae didn't exist (Maddin et al., 2013), sometimes the composite was recovered as a eucacopine (Schoch & Sues, 2013), and sometimes the composite was recovered as a dissorophine (Liu, 2018). So basically every possible result short of it being recovered as a non-dissorophid!

The Centennial State

The new specimen that we report here was collected from what's known as the Placerville locality by my coauthors, Adam Huttenlocker and Jason Pardo, a few years back. It is not nearly as complete as the other two specimens, but it is well-preserved, enough to show some distinctive features not found in most or all of the other dissorophids. For example, the two bones called the postorbital (right behind the eye) and the supratemporal (a little farther back) usually touch, but here they do not (this is found in two of the species of Cacops as well). The jaw articulation (marked by the quadrate) also sits in front of the level of the back of the skull (marked by the postparietal); this is something found only in Dissorophus and Scapanops. So there is actually quite a lot of information in this little skull despite it being at best 25% complete!

Our phylogenetic analysis, which combines two previous matrices (it was originally intended for a larger sample), finally recovers not just the original two specimens, but also this third one as a proper clade (i.e. what you expect if they really do all belong to the same species)! The statistical support is not very good though, and it's quite possible that a future study could find a different result. Dissorophid phylogenetics remains very much in flux outside of just Conjunctio (something that I'm working on right now).

COVID addendum: Lest someone think that all of us are superhumans who pumped out this paper in the pandemic, it was mostly completed before the pandemic really set in (we submitted the first version in May 2020). Jason and I in particular as current and recently graduated PhD students have really slowed down in putting new work into the pipeline during the pandemic, which I think is important to note since a lot of people are really struggling and should not be concerned with their perceived relative productivity!

Refs

Anderson, J.S., Scott, D. and Reisz, R.R., 2020. The anatomy of the dermatocranium and mandible of Cacops aspidephorus Williston, 1910 (Temnospondyli: Dissorophidae), from the Lower Permian of Texas. Journal of Vertebrate Paleontology, 40(2), p.e1776720.
Carroll, R.L., 1964. Early evolution of the dissorophid amphibians. Bulletin of the Museum of Comparative Zoology, 131, p. 163-250.
Dilkes, D.W., 2020. Revision of the Early Permian Dissorophid ‘Dissorophus’ angustus (Temnospondyli: Dissorophoidea). Journal of Vertebrate Paleontology, 40(4), p.e1801704.
Gee, B.M. and Reisz, R.R., 2018. Cranial and postcranial anatomy of Cacops morrisi, a eucacopine dissorophid from the early Permian of Oklahoma. Journal of Vertebrate Paleontology, 38(2), p.e1433186.
Holmes, R., Berman, D.S. and Anderson, J.S., 2013. A new dissorophid (Temnospondyli, Dissorophoidea) from the Early Permian of New Mexico (United States). Comptes Rendus Palevol, 12(7-8), pp.419-435.
Lewis, G.E., Baird, D. and Vaughn, P.P. 1965. Early Permian vertebrates from the Cutler Formation of the Placerville Area, Colorado. Geological Survey Professional Paper 503-C.
Liu, J., 2018. Osteology of the large dissorophid temnospondyl Anakamacops petrolicus from the Guadalupian Dashankou Fauna of China. Journal of Vertebrate Paleontology, 38(5), p.e1513407.
Maddin, H.C., Fröbisch, N.B., Evans, D.C. and Milner, A.R., 2013. Reappraisal of the Early Permian amphibamid Tersomius texensis and some referred material. Comptes Rendus Palevol, 12(7-8), pp.447-461.
Schoch, R.R., 2012. Character distribution and phylogeny of the dissorophid temnospondyls. Fossil Record, 15(2), pp.121-137.
Schoch, R.R. and Sues, H.D., 2013. A new dissorophid temnospondyl from the Lower Permian of north-central Texas. Comptes Rendus Palevol, 12(7-8), pp.437-445.
Schoch, R.R. and Milner, A.R. 2014. Handbook of Paleoherpetology: Temnospondyli I (Part 3A2). München: Verlag Dr. Friedrich Pfeil.

New publication (Reassessment of historic ‘microsaurs’ from Joggins, Nova Scotia, reveals hidden diversity in the earliest amniote ecosystem; Mann et al., 2020, Papers in Palaeontology)

5/7/2020

Title: Reassessment of historic ‘microsaurs’ from Joggins, Nova Scotia, reveals hidden diversity in the earliest amniote ecosystem
Authors: A. Mann; B.M. Gee, J.D. Pardo, D. Marjanović, G.R. Adams, A.S. Calthorpe, H.C. Maddin, J.S. Anderson
Journal: Papers in Palaeontology
DOI to paper: 10.1002/spp2.1316

General summary: In what is my biggest collaboration to date with nearly all of the early tetrapod workers in Canada, here's probably my last paper of 2020: a very thorough revision of the 'microsaur' Asaphestera from Joggins, Nova Scotia! Joggins is one of the oldest sites with a well-preserved late Carboniferous tetrapod community (315-318 Ma), and it preserves a unique forest swamp environment in which animals are frequently preserved inside of logs (whether or not they lived in the logs is another question). Because of its age, Joggins is critical for exploring the early origins of many groups, as it often preserves the oldest members of many Paleozoic clades in North America, if not globally. For example, the temnospondyl Dendrerpeton from Joggins is the oldest known temnospondyl on the continent. There's a rich suite of 'microsaurs,' the ever controversial group of tetrapods of unclear affinities to either crown reptiles or to crown amphibians, that have been reported from Joggins, but many of the original studies are dated such that the interpretations are of limited utility for modern workers trying to elucidate phylogenetic relationships and other macroevolutionary trends. The frequent disarticulation and fragmentation of specimens also makes referrals of specimens to the same taxon somewhat suspect, with the potential for purportedly well-known taxa to be represented by a chimeric blend of multiple taxa. We spent a lot of time looking at historic specimens of one such 'microsaur,' Asaphestera, because we were particularly interested in exploring some of these very poorly known Carboniferous 'microsaurs' that are really important for understanding the evolution and relationships of the much better known early Permian taxa that everybody on this paper has studied to various degrees. Through this, we identified that the various specimens lumped under Asaphestera intermedia are actually a hodge-podge of different taxa, at least one of which is not even a 'microsaur,' but as we propose, is perhaps the earliest definitive synapsid!

The oldest synapsid?

The oldest synapsid, extremely controversially so, is Protoclepsydrops, also reported from Joggins. As can be seen from Carroll's (1964) illustration of the holotype, the material, mostly postcranial in nature, is perhaps a little lacking for some people, which is why it's remained controversial as to whether it is in fact a synapsid. More unequivocal early synapsids include Archaeothyris and Echinerpeton, which are known from Florence, another locality in Nova Scotia that's a few million years younger than Joggins. You can find the original description of Archaeothyris by my advisor here, and some recent work on Echinerpeton by my friend and the leader author of this study, Arjan Mann, here and here. Long story short, like most other tetrapod groups, identifying unequivocal early members of most of these groups is very difficult.

Holotype of Asaphestera platyris, which we refer to Synapsida here.

The specimen to the left, a former referred specimen of Asaphestera intermedia that was originally the holotype of a separate species called 'Asaphestera platyris,' is what we're identifying as a less dubious synapsid and thus restoring as a valid taxon once again, but under a totally new identity. The specimen is admittedly not the nicest - these are the pancakes that we get at Joggins - but a few features indicate synapsid affinities that we listed in the paper: "large facial process of the maxilla, a single, narrowly triangular, small median postparietal flanked by the tabulars, which are restricted to the occipital surface of the skull, and substantial contact between the postorbital and parietal."

Among synapsids, this specimen most closely resembles the eothyridids, although it shares a number of features with acleistorhinid parareptiles, which were often confused for eothyridids in their earlier history of study (perhaps they still are eothyridids?). Whether or not it could be the same taxon as Protoclepsydrops can't be resolved here because the newly resurrected Asaphestera platyris has no known postcrania at present. Asaphestera would have precedent though, having been named in 1934 versus Protoclepsydrops in 1964.

We didn't intend to search for scant evidence of early synapsids, but surprising things can emerge from detailed surveys of early amniotes, most of which would look like small lizard-y things to the average person.

Microsaur math

So we've already turned part of one 'microsaur' into a synapsid at this point. Net: no change. But the holotype of Asaphestera platyris was not the holotype of Asaphestera intermedia, so the latter was still valid as a 'microsaur' at this point...

The next specimen on the list is one that allegedly had three parts, all of different taxa, but only one was ever figured, the lectotype of what was named Hylerpeton intermedium way back in the day by Dawson (1894). Hylerpeton is its own distinct taxon (a possible gymnarthrid), with Hylerpeton dawsoni as the type species, so when Steen (1934) identified the differences from that species, she then created Asaphestera to accommodate 'Hylerpeton' intermedium. The species was still valid but not part of Hylerpeton, and the lectotype, among other specimens, were packaged into Asaphestera platyris. This is probably really confusing at this point. Seems like a good time to introduce the very helpful schematic created by one of the co-authors, Jason Pardo, below. The synapsid that we identify is specimen RM 2-1192. It was always the holotype of Asaphestera platyris, but not the holotype Asaphestera intermedia, which was the new combination that Carroll (1963) came up with to combine a bunch of new and old specimens, taking Dawson's species name (modified for gender) and Steen's genus name.

Holotype of Hylerpeton intermedium, a nomen dubium after our analysis.

RM 2-1131 was the original holotype of Hylerpeton intermedium and became the holotype of the new Asaphestera intermedia. Here it is above on the right. If the figure does not look that impressive...that's because the specimen is not very impressive. We couldn't identify it to a particular tetrapod clade, let alone diagnose it as a unique taxon of whatever clade that might be, and we designated it as a nomen dubium ("doubtful name"), which is the fancy way of saying "this is not valid because it is not clearly unique." So at this point, we've killed one 'microsaur.' Net: -1 microsaur

But there are a bunch of other specimens that were referred to Asaphestera intermedia (so not the holotype) by Carroll. Now if the holotype of a species is so incomplete that it can't be diagnosed, it usually doesn't matter if you think that you have a much better newer specimen. Even if the holotype was a rib, and you find a complete skeleton that you think is the same thing, the original holotype carries the name. If the holotype is suspect, then the name goes with it. There are instances where you can create "other types," such as neotypes, lectotypes, etc. Wikipedia has a surprisingly good summary (paleontologists don't use all the ones that are listed). Neotypes, for example, are necessitated when the holotype is destroyed and you have a good referred specimen on hand that can become the new bearer of the name. But usually if the holotype is bad, then it becomes a nomen dubium (which has sometimes led to the loss of some otherwise very good names).

Holotype of the new 'microsaur' taxon Steenerpeton silvae.

In any event, we then set about examining the referred specimens of "Asaphestera intermedia," at this point a sunk taxon, because some of them are much nicer. The one above was sufficiently complete to be diagnosed and differentiated from other taxa, and we made it a holotype of a new 'microsaur' taxon: Steenerpeton silvae, which we named for Margaret Steen, (the same Steen I keep mentioning throughout this post), and for 'of the forest,' referring to Joggins original paleoenvironment. So now we've added back one 'microsaur!' Net: +0 microsaurs

Steenerpeton appears fairly derived already, in contrast to traditional interpretations of Asaphestera of any flavour, and we suggest that it may be a recumbirostran, the derived group of 'microsaurs' that host a suite of fossorial adaptations. This actually lines up well with the documented presence of other derived 'microsaurs' like possible pantylids and gymnarthrids at Joggins and provides more evidence that the origin and diversification of recumbirostrans begin earlier than has been historically conceived and probably occurred in an interval without substantial body fossils. The former point in particular is a real running theme at this point for most of the research that all of us do.

There were some other poorly known taxa that we wanted to get a look at because they have also been interpreted as relatively primitive 'microsaurs.' One, Ricnodon, is better known from Europe. Reports of Ricnodon at Joggins are very fragmentary and seem dubious. The taxon is still valid, but it doesn't clearly exist at Joggins. Net change: -1 'microsaur'

A second one is Archerpeton anthracos, a taxon named by Carroll in 1964. It was revised in 1996 by Reisz and Modesto who identified it as a 'microsaur,' rather than as a reptile; of course, with the hypothesis that 'microsaurs' are reptiles, this is a moot point really. In any event, in spite of the nice illustrations of the holotype of Archerpeton, it doesn't preserve much helpful information. In fact, we couldn't diagnose it. The previous diagnosis listed a number of features that aren't truly unique to this taxon. Nomen dubium. Net change: -2 'microsaurs'

Holotype of the indeterminate tetrapod Archerpeton anthracos.

Avengers assemble!

This is the biggest collaboration I've ever worked on (some might say the most ambitious crossover ever). It was born nearly 2.5 years ago at the SVP Annual Meeting in Calgary, which is where Arjan and I both gave talks on different 'microsaurs' (Arjan's turned into his published paper on the new Mazon Creek 'microsaur' Diabloroter, and mine turned into my published paper on new material of Llistrofus from Richards Spur). Jason Pardo (and Jason Anderson) had just had a high-profile paper come out that summer that recovered 'microsaurs' as crown amniotes, a paper I didn't stop hearing about from my advisor even though I spent the whole summer doing fieldwork in Arizona. We all ended up talking about future directions for 'microsaur' work and agreed on needing to reevaluate a lot of the earliest records of what are called "tuditanomorphs" to better characterize them for big tetrapod analyses to continue to sort out different relationships. This in turn spawned what's become a dynamic working group among the three of us and eventually led to us jokingly assigning ourselves as different members of the Avengers as this team of early career researchers doing early tetrapod work on basically every single clade that's out there. If you add up everything that we've collectively published, we account for actinopterygian and sarcopterygian fish, aïstopods (stem tetrapods), temnospondyls, parareptiles, seymouriamorphs, embolomeres, synapsids, and 'microsaurs.' You can see some of the other fruits of this working group in Pardo & Mann (2018), Mann, Pardo & Maddin (2019) and Mann & Gee (2020), with plenty of future work slated for the immediate future (or once things sort of go back to normal)! I will leave it to the readers' imagination as to which members we have self-assigned as...

The final sum

The Joggins 'microsaurs' are the only taxa from Carboniferous localities that have experienced these sorts of "lump/split" boom-bust cycles, going from being remarkably taxonomically diverse to remarkably intraspecific variable and back again. The classic Joggins temnospondyl, Dendrerpeton, is another great example of this; the type species, D. acadianum, includes several defunct genera such as Smilerpeton (great name) and Dendryazousa. There are numerous taxa that have been named that weren't even assigned to the correct clade! A lot of this has been because of historic interpretations based on the often fragmentary and disarticulated specimens at Joggins; we don't get many 3-D specimens, and the distortions can affect interpretations of the anatomy. This means that there's a lot of room to go back and look at specimens that were often collected more than 120 years ago and that haven't been re-examined in detail in more than 60, 70, 80... years to assess the original interpretations. Particularly in light of new discoveries at other localities, updated taxonomy, and the recognition that a lot of clades have deeper origins than was often hypothesized in the early 20th century, exploring one of the oldest (crown) tetrapod assemblages in the world is essential for unraveling a lot of the mysteries of the origin of the modern tetrapod clades.

When we started this project, there were seven 'microsaurs' recognized from Joggins: Archerpeton, Asaphestera, Hylerpeton, Leiocephalikon, Ricnodon, and Trachystegos. We added Steenerpeton (total: 8), but deep-sixed Archerpeton, recognized Asaphestera proper as a synapsid, and cast doubt on the Joggins records of Ricnodon (final count: 5). We've got plans for some of those other ones that didn't get addressed here...stay tuned for plenty more studies coming out on Joggins material and other Carboniferous faunas!

Refs

Carroll RL. 1963. A microsaur from the Pennsyvanian of Joggins, Nova Scotia. Natural History Papers of the National Museum of Canada 22:1-13.
Carroll RL. 1964. The earliest reptiles. Zoological Journal of the Linnean Society 45(304): 61-83. DOI: 10.1111/j.1096-3642.1964.tb00488.x
Dawson JW. 1894. Preliminary note on recent discoveries of batrachians and other air-breathers in teh coal formation of Nova Scotia. The Canadian Record of Science 6:1-7.
Reisz RR, Modesto SP. 1996. Archerpeton anthracos from the Joggins Formation of Nova Scotia: a microsaur, not a reptile. Canadian Journal of Earth Sciences 33(5): 703-709. DOI: 10.1139/e96-053
Steen, MC. 1934. The amphibian fauna from the South Joggins. Nova Scotia. Proceedings of the Zoological Society of London 104(3): 465-504. DOI: 10.1111/j.1096-3642.1934.tb01644.x

New publication: Lissamphibian-like toepads in an exceptionally preserved amphibamiform from Mazon Creek (Mann & Gee; Journal of Vertebrate Paleontology)

3/25/2020

Title: Lissamphibian-like toepads in an exceptionally preserved amphibamiform from Mazon Creek
Authors: A. Mann; B.M. Gee
Journal: Journal of Vertebrate Paleontology e1727490
DOI to paper: 10.1080/02724634.2019.1727490

Note: this paper came out on Wednesday, but it took a little while to get around to the blog post. As you can imagine, it's a little hard to write a blog in the middle of a pandemic. I actually plan to try to rev things back up in a week or two after I finish a bunch of problem sets for my stats classes, so stay tuned...

General summary: Late Carboniferous Lagerstätte (fossil sites with remarkable preservation) are incredibly important for our understanding of the early evolution of many tetrapod clades. Mazon Creek in Illinois is one of the most famous Lagerstätte in North America and has produced a slew of both vertebrates and invertebrate material of great interest to paleontologists across the board (this is also where the famed Tully Monster comes from). The tetrapods have been studied by some of the most preeminent Paleozoic workers, including Moodie, Gregory, Watson, Westoll, Olson, and Baird, as well as by living paleontologists such as Jason Anderson and Andrew Milner. Preservation at Mazon Creek occurs in nodules that can be cracked in half to hopefully reveal a marvelous fossil within (or just a boring clay ball). Not only do these nodules often preserve complete, articulated skeletons, but they often preserve soft tissue structures (which is how we get a lot of records of squishy invertebrates). Here we describe a nice amphibamiform specimen (recalling that amphibamiforms are widely hypothesized to be on the lissamphibian stem) that preserves the oldest (quite possibly the only) record of toepad ('toe pad' with a space?) structures in a temnospondyl that superficially resemble those of lissamphibians. Arjan's doctoral dissertation is on Mazon Creek (the amniotes mostly); talk to him (arjanmann[at]cmail[dot]carleton[dot]ca) if you wanna know more about the exciting stuff going on!

New Publication: Computed tomographic analysis of the cranium of the early Permian recumbirostran 'microsaur' Euryodus dalyae reveals new information of the braincase and mandible (Gee, Bevitt, & Reisz; Papers in Palaeontology)

3/13/2020

Title: Computed tomographic analysis of the cranium of the early Permian recumbirostran 'microsaur' Euryodus dalyae reveals new information of the braincase and mandible.
Authors: B.M. Gee, J.J. Bevitt, R.R. Reisz
Journal: Papers in Palaeontology
DOI to paper: 10.1002/spp2.1304

Holotype of Euryodus dalyae in dorsal and lateral views (fig. 1 from the paper).

General summary: Yes, this is a long title. No, this is not a temnospondyl. I thought I was done with 'microsaurs' with Llistrofus. That has not panned out. So here we are...
Here is more CT of another 'microsaur,' this time the gymnarthrid Euryodus dalyae (with bonus friends from Richards Spur)! This continues what is now a longstanding trend of zapping 'microsaurs' - to date, descriptions via CT data have been made for Quasicaecilia (Pardo et al., 2015), Carrolla (Maddin et al., 2011), Rhynchonkos, Aletrimyti, and Dvellecanus (Szostakiwskyj et al., 2015), Huskerpeton (Huttenlocker et al., 2011), Brachydectes (Pardo & Anderson, 2016), and Llistrofus (Gee et al., 2019), which is way more sampling than anybody's done for a particular temnospondyl clade... Here we scanned the holotype of Euryodus dalyae, a 'microsaur' from the early Permian of Oklahoma (but not Richards Spur) and a specimen from Richards Spur that was identified as E. dalyae. This provides the first published data on gymnarthrid 'microsaurs' and revealed a number of intriguing features, such as extensive ossification of the braincase, as seen in many recumbirostrans, and a second tooth row on the lower jaw, a feature that's never been reported in 'microsaurs.'

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