Hey. Been a while.
Alright, I'm going to ignore the Elephantosaurus in the room (ha, dicynodont joke*) of how long it's been since I last posted here and hopefully ease this blog back in to activity again with a nice and easy look back at dicynodont research in the past year. Compared to 2021 there's a bit less to write about and therefore easier to organise and summarise, so this should be a more manageable post all around.
(*Elephantosaurus is a large, thick-headed kannemeyeriiform from the Middle Triassic of Russia, named so because it was thought to be eponymously elephantine in size. It's known only by a chunk of skull from between the eyes 20 cm across, which although big isn't really any larger than some other wide-headed kannemeyeriiforms like Stahleckeria.)
New 'dont in a block
Only one new dicynodont was named this year, the cistecephalid Kembawacela yajuwayeyi (formerly known as the 'Malawian cistecephalid') from the Late Permian of Malawi, named in September by Araújo et al. Kembawacela itself was originally named in 2019 with the type species K. kitchingi from neighbouring Zambia, and was a member of Cistecephalidae, a highly specialised family of mole-like burrowers. Kembawacela is unique among cistecephalids for still possessing a pair of prominent tusks (which other cistecephalids lost), although K. yajuwayeyi does not preserve this part of the skull. The skull itself is encased in a block of solid matrix, so was studied using a synchrotron micro-CT scanner. K. yajuwayeyi is broadly similar to K. kitchingi superficially, mostly differing in details of how the bones of the skull attach to each other and the internal arrangement of nerves and blood vessels in the snout.
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| The matrix-covered specimen of K. yajuwayeyi and its synchrotron µCT-render of the skull, viewed from above. Modified from Araújo et al. (2022), CC-BY 4.0. |
More broadly, K. yajuwayeyi highlights the level of cistecephalid endemism between even very closely associated basins in East Africa. Although there are broad similarities between the Permian faunas of South and East Africa, recent investigations have shown local species-level variations between these regions. This is particularly true of cistecephalids, where genera appear to be restricted to singular basins. This has been attributed to their mole-like lifestyles, which would have limited their dispersal. The discovery of K. yajuwayeyi in Malawi supports this idea, with two very closely related yet still distinct species from two neighbouring depositional basins.
An aside I'd also like to highlight the etymology of K. yajuwayeyi. The species is named in honour of Dr. Yusuf Juwayeyi, an accomplished friend and colleague of the authors. Usually when a species is named after someone, the suffix -i or -ae is appended to their name and Latinised (say in this case, "juwayeyii"). However, the authors describing K. yajuwayeyi didn't follow this convention, and instead combined his name with ya-, a possessive prefix in Chichewa, the Bantu language spoken locally in Malawi. It's a little detail, but I think it adds something more personal to the name it's honouring than the standard -i suffix.
This wasn't all Kembawacela yajuwayeyi got up to this year, but we'll come back to that.
Redescriptions and revisions
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| Specimens of Dicynodon angielczyki from Tanzania (A, B), Zambia (C) and Mozambique (D), with D. lacerticeps (E, F). From Kammerer et al. (2022). |
(*The former second species, D. huenei, was transferred to Daptocephalus in the same paper naming D. angielczyki, a story that really deserves its own post).
The overlap of Dicynodon angielczki across Tanzania, Mozambique and Zambia is interesting to contrast with the apparent endemism between the two species of Kembawacela. Now admittedly D. angielczyki isn't known from the Chiweta Beds of Malawi, and they likely represent different ages, so it's not a 1:1 comparison. Still, I think it highlights the complexities in dicynodont distribution across the various African basins, with larger species like D. angielczyki being found across (but still collectively endemic to) several neighbouring basins, while smaller and more specialised varieties like cistecephalids speciated even at this geographic scale.
The Shaanbeikannemeyeria Saga
This one comes with a little story first. For the longest time, Shaanbeikannemeyeria xilougouensis was one of the most mysterious dicynodonts to me. For starters, its Wikipedia page was the barest of bones:
"Shaanbeikannemeyeria is an extinct genus of non-mammalian synapsid known from the Middle Triassic (Anisian) of China."
Heck, up until 2018 it had been entirely redirected to the Kannemeyeria page on the basis it was suggested to be synonymous (again, the taxonomy here is its own whole thing probably deserving another post—if anything it should have been redirected to Rechnisaurus!). However, unlike a lot of other dicynodonts with bare-bones Wiki pages for which a bit of sleuthing and perseverance will turn up other results, I could find next to nothing accessible online for Shaanbeikannemeyeria. Papers, photos, illustrations, any more information, I was turning up blanks.
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| The squashed looking skull of 'S. buerdongia' (miscaptioned here as 'Shanbeikannemeyeria'). From Li (1980). |
Well, almost. There is a copy of a paper online naming a second species, S. buerdongia, which is fairly unanimously recognised as a synonym of S. xilougouensis nowadays. However, the skull of this specimen has been heavily eroded, removing most of the skull itself to leave only the lower jaw, palate and occiput. It's also been rather squashed out of shape. Tantalisingly, the whole skull of S. xilougouensis was said to be well preserved by comparison, so this just drove my curiosity further up the wall.
I don't think this was just a case of looking in the wrong places either. As far as I could tell there weren't any published reconstructions of Shaanbeikannemeyeria out there either, so it seems to me that information on this dicynodont really was just hard to come by in general, including as physical publications.
I was thrown a bone this past May when a friend shared with me a scanned copy of Paleovertebrata Sinica Volume III, a publication on China's synapsid fossil record. Naturally, I went to see what it had to say on dicynodonts, and to my surprise saw an illustration of the complete skull of Shaanbeikannemeyeria! I was compelled to make a sketchy reconstruction of it, to my knowledge still the only reconstruction of it currently online, and quite possibly the first one ever—assuming an earlier published reconstruction doesn't exist in a physical publication somewhere.
And then guess what happened.
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| My reconstruction of Shaanbeikannemeyeria, based off an illustration from Paleovertebrata Sinica III and pre-Liu (2022). |
Only just a few days later that June, Jun Liu publishes an open-access description of numerous new specimens of Shaanbeikannemeyeria, including nearly complete postcrania and skulls from individuals of various ages, all lavishly figured with photos. Decades of next to nothing to go on, then when a single old illustration serendipitously makes its way to me, an entire paper with all the reference material I could ever ask for drops within days of reconstructing it. I'm still flabbergasted by the timing of this.*
Overnight Shaanbeikannemeyeria went from one of the least accessible and imaged kannemeyeriiforms to one of the best. If you're a palaeoartist feeling inclined to draw a dicynodont, I encourage you to give Shaanbeikannemeyeria some love. The references are all there now, so let's make up for lost time!
(*This isn't even the first time, believe it or not—some years back I was asked to draw Hulsanpes, at the time a rarely illustrated and poorly understood paravian of uncertain affinity. A week later, Halszkaraptor is published, identifying Hulsanpes as a close relative.)
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| Some of the new Shaanbeikannemeyeria material. Holy cow. From Liu (2022). |
More Research
Another paper published in June was a study by Macungo et al. on the braincase and basicranium of three emydopoids; little Myosaurus and two cistecephalids, Kawingasaurus and the then-unnamed Kembawacela yajuwayeyi (told you it'd be back). This study revealed numerous new details of emydopoid brain anatomy that was informative for both their physiology and phylogeny.
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| A reconstruction of a burrowing cistecephalid that I can only describe as "scrunkly". By Luzia Soares, from Macungo et al. (2022). |
Their study demonstrated the presence of prominent bony crests and hollows on the back of cistecephalid skulls that would have anchored well-developed neck muscles, as well as relatively fused and ossified braincases. This supports a previous suggestion that cistecephalids likely not only used their forelimbs to dig, but also used their heads to shovel dirt and soil out of the way. This had previously been proposed based on the highly complex and strong suturing of their skull bones (Kammerer 2021), and now there's evidence for strong neck lifting muscles and solidified braincases to protect the brain from rapid and powerful head movements.
They also highlighted several novel phylogenetic relations following the inclusion of internal cranial characteristics. One of these was recovering the purported basal-bidentalian Rastodon as a basal emydopoid instead. A relationship to emydopoids had been suspected for Rastodon before, but almost every prior phylogenetic analysis still found it as a bidentalian, and none as an emdyopoid until now. Another notable shift was finding kingoriids to be more basal than emydopids, by definition removing them from Kistcephalia. This upset is accompanied by the removal of Thliptosaurus from its original home in Kingoriidae to a position between them and emydopids, alongside Digalodon. Kembawacela and Sauroscaptor have also shifted from their original placements as more derived than Cistecephalus to having diverged first among cistecephalids.
Lystrosaurus made its obligatory appearance in September with a paper testing for Bergmann's rule across Lystrosaurus populations. Bergmann's rule posits that animals grow to larger sizes at higher latitudes, usually attributed to cooler climates, and a study by Kulik & Sidor set out to test if this rule applied to the distribution of Early Triassic Lystrosaurus. Lystrosaurus body size is already an interesting subject, as it is known to show a marked decrease following the end-Permian mass extinction, albeit apparently not through dwarfism or similar mechanisms but rather seemingly by just living fast and dying younger.
These new results found Lystrosaurus to not follow Bergmann's rule, with the maximum body sizes being much the same between high and mid-latitudes. Curiously though, the average sizes differed between high-latitude Gondwana and mid-latitude China, with Lystrosaurus more regularly reaching larger sizes in mid-latitudes. This corroborates results from a paper the year before (Kulik et al., 2021) which found Lystrosaurus from China to more often grow larger and for longer than their southern relatives. This suggests that regional environmental conditions may have been a greater factor affecting their body size and lifespans than latitude, with wetter and more favourable conditions at mid-latitudes.
Lystrosaurus would make another, very exciting appearance this year too in an August paper from Smith et al. on the taphonomy of Lystrosaurus in the earliest Triassic of South Africa. The paper itself is cool, but that's not what grabbed people's attention. What got people excited was that this was the first official publication of the long-rumoured Lystrosaurus mummies! I'm planning to discuss the paper and the mummies in their own post, so I won't go deeper into it here, but in short these mummies and how they died can tell as whole lot about the environmental conditions and behaviour of Lystrosaurus post Permo-Triassic extinction, and not just about their life appearance.
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| New skulls of Dinodontosaurus brevirostris, plus D. "platygnathus" (5), with lower jaws. From Escobar et al. (2022). |
The phylogenetic results are not much different from existing analyses, strengthening the relationship between Dinodontosaurus to the Stahleckeriidae + Angonisaurus clade. Notably, the reflected lamina is well preserved in one of the new specimens, revealing it to be very large, rounded and unornamented, very much like those of Angonisaurus and stahleckeriids. On the other hand, other features like the shape and structure of the symphysis differ from stahleckeriids, affirming its position outside of Stahleckeriidae proper.
They also highlight potential taxonomic implications for the other Dinodontosaurus species, the Brazilian D. tener, too. Namely, while the mandibles of historic D. tener specimens are evidently distinct from D. brevirostris (e.g. smaller reflected lamina, more stahleckeriine-like jaw symphyses), some specimens seem more similar to those of D. brevirostris. Quite what this means taxonomically without a rigorous osteological analysis of D. tener isn't clear, but it is interesting following comments from Kammerer and Ordoñez (2021) highlighting the variation that exists in D. tener based on skulls, which now seems to also extend to the mandibles as well. Time will tell for however this shakes out in the future.
Dicynodont adjacent
In more general synapsid news, but still of great dicynodont relevance, was the first broad-scale description of the reflected lamina in therapsids by Savannah Olroyd and Christian Sidor in August. This structure, a sheet of bone attached to the angular of the lower jaw, has long been of interest to therapsid researchers and its function has been rather enigmatic. Some have regarded it as a point for muscle attachments, while others have implicated it in the evolution of hearing in therapsids. Olroyd and Sidor (2022) is a major step forward in sorting out just how the reflected lamina evolved and varied in therapsids, as most previous research has focused on specific comparisons within groups, and the broad general anatomy between therapsids as a whole has been poorly characterised.
Dicynodonts were notable in their study for the level of variability in the shape, size, and sculpturing of the reflected lamina compared to other therapsids, which otherwise have rather stereotyped, clade-specific structures. Curiously, bidentalian dicynodonts seem to have lost much of the ridges found on the laminae of other therapsids, especially in the Triassic kannemeyeriiforms, leaving a much less complex surface. This is especially unusual considering that non-bidentalian dicynodonts have some of the more complex and variably structured reflected laminae of any therapsids. Whatever dicynodonts were using the reflected lamina for, clearly they were experimenting with it. The function of the reflected lamina is one of the most fascinating mysteries in therapsid research for me, and so I am very excited to see where this research will go in the future now that it has a standardised framework to work from.
Summary
And that about wraps up the review! A lot of cool stuff, even if it's a bit light compared to previous years. The year seems to have been fairly top heavy, having got off to a slow start but picking up from June onwards. Another new year with at least one new species, so the ball is still rolling on that count. It's always hard to make a call for any "best" discovery of the year, but I think if I had to pick a favourite that would have to go to the Shaanbeikannemeyeria redescription for being a totally unexpected but welcome surprise and also for its truly impeccable timing. 10/10 job.
The phylogenetic scope is definitely more limited this year, with only emydopoids, kannemeyeriiforms, and other dicynodontoids receiving dedicated papers this year. Nothing for basal anomodonts and dicynodonts, endothiodonts, plycaecephalids, or cryptodonts, excepting their appearances in Olroyd and Sidor (2022) with just about every other type of therapsid. Of the groups covered, it's a fairly even split with 2–3 papers each for the three groupings. Lystrosaurus, as usual, seems to be a favourite with two papers, though Kembawacela had a pretty good year too.
That about wraps up 2022, here's hoping for another exciting year of dicynodonts in 2023! I'm proud to say that I'll be taking part in this research myself, as part of my ongoing Masters degree I will be examining and describing a dicynodont specimen, and it's probable you'll be hearing more about this on here down the line. Hopefully I'll get some exciting results from my research, and I look forward to seeing what else the new year will have in store for dicynodonts.
And maybe I'll even get some more actual posts on here too.
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| Scottish dicynodont Gordonia stares doubtfully at the above sentence. |
References
Araújo, R., Macungo, Z., Fernandez, V., Chindebvu, E. G., & Jacobs, L. L. (2022). Kembawacela yajuwayeyi n. sp., a new cistecephalid species (Dicynodontia: Emydopoidea) from the Upper Permian of Malawi. Journal of African Earth Sciences. 196: Article 104726.
Escobar, J. A., Martinelli, A. G., Ezcurra, M. D., Fiorelli, L. E., Von Baczko, M. B., Novas, F. E., & Desojo, J. B. (2022). Reassessment of the mandibular anatomy of non-stahleckeriine kannemeyeriiforms (Synapsida, Dicynodontia) from the Ladinian-early Carnian Chañares Formation (northwestern Argentina), and its taxonomic and phylogenetic significance. Ameghiniana. In press.
Kammerer, C.F. (2021). Elevated cranial sutural complexity in burrowing dicynodonts. Frontiers in Ecology and Evolution. 9: 674151.
Kammerer, C. F., Araújo, R., Cumbane, K., MaCungo, Z., Smith, R. M. H., & Angielczyk, K. D. (2022). New material of Dicynodon angielczyki (Synapsida: Anomodontia) from Mozambique and Zambia with biostratigraphic implications for African Permo-Triassic basins. Journal of Vertebrate Paleontology. 41 (6): e2041652.
Kammerer, C. F., Ordoñez, M. D. (2021). Dicynodonts (Therapsida: Anomodontia) of South America. Journal of South American Earth Sciences. 108: 103171
Kulik, Z. T., Lungmus, J. K., Angielczyk, K. D., & Sidor, C. A. (2021). Living fast in the Triassic: New data on life history in Lystrosaurus (Therapsida: Dicynodontia) from northeastern Pangea. PLOS ONE. 16 (11): e0259369.
Kulik, Z. T., Sidor, C. A. (2022). A test of Bergmann's rule in the Early Triassic: latitude, body size, and sampling in Lystrosaurus. Paleobiology: 1–15.
Li, J-L. (1980). Kannemeyeria fossil from Inner Mongolia. Vertebrata PalAsiatica. 18 (2): 94–99.
Liu, J. (2022). On kannemeyeriiform dicynodonts from the Shaanbeikannemeyeria Assemblage Zone of the Ordos Basin, China. Vertebrata PalAsiatica: 1–38.
Macungo, Z., Benoit, J., Fernandez, V., & Araújo, R. M. N. (2022). X-ray microcomputed and synchrotron tomographic analysis of the basicranial axis of emydopoid dicynodonts: implications for fossoriality and phylogeny. Zoological Journal of the Linnean Society.
Olroyd, S., Sidor, C. A. (2022) Nomenclature, comparative anatomy, and evolution of the reflected lamina of the angular in non-mammalian synapsids. Journal of Vertebrate Paleontology. 42 (1): e2101923.
Smith, R. M. H., Botha, J., Viglietti, P. A. (2022). Taphonomy of drought afflicted tetrapods in the Early Triassic Karoo Basin, South Africa. Palaeogeography, Palaeoclimatology, Palaeoecology. 604: Article 111207.
