Endothiodon (Permian dicynodont) taxonomic revision + Solanutherium, new Late Cretaceous mammal from Argentina + hypercanines

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Ben Creisler

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May 31, 2024, 2:25:22 PMMay 31
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Ben Creisler

Some recent synapsid/mammal related papers:

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Iyra E. M. Maharaj, Zanildo Macungo, Roger M. H. Smith, Anusuya Chinsamy & Ricardo Araújo (2024)
Taxonomic revision of the late Permian dicynodont genus Endothiodon (Therapsida, Anomodontia)
Journal of Systematic Palaeontology 22(1): 2346578
doi: https://doi.org/10.1080/14772019.2024.2346578
https://www.tandfonline.com/doi/full/10.1080/14772019.2024.2346578

The dicynodont genus Endothiodon, known for its unusual anatomy and possession of multiple tooth rows in some specimens, has a complex taxonomic history. We conducted a comprehensive review of 150 Endothiodon specimens from South Africa, Mozambique, Tanzania, Malawi, Zambia, Brazil and India to clarify taxonomy, diagnose species and understand relationships. Additionally, we analysed the biostratigraphic distribution of South African Endothiodon specimens, confined to the Endothiodon Assemblage Zone (AZ). Using 24 specimens, including four outgroup taxa, we created a character matrix with 22 new characters. Phylogenetic analysis revealed three clades: a basal clade representing the species Endothiodon mahalanobisi and two clades formed by the species Endothiodon tolani and Endothiodon bathystoma. Endothiodon bathystoma is diagnosed by a large pineal boss, E. tolani by an enlarged caniniform and a thin collar of bone around the pineal foramen, and E. mahalanobisi by an unornamented pineal foramen. ‘Endothiodon uniseries’ subsumes within E. bathystoma, suggesting that tooth row count must be used with caution as a character. Endothiodon mahalanobisi is exclusive to India, whereas all three of the valid Endothiodon species co-occur in Mozambique, whilst South African specimens exclusively represent E. bathystoma. Assuming contemporaneous deposition, a longitudinal gradient of Endothiodon diversity is evident, with East African basins harbouring the greatest diversity. This taxonomic revision clarifies the species diversity, intrageneric relationships and geographical distribution of Endothiodon. Our findings contribute to understanding the evolutionary history of these unique dicynodonts and emphasize the importance of considering both anatomical characteristics and geographical patterns in taxonomic investigations.

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Solanutherium walshi gen. et sp. nov.

Brigid E. Connelly, Mauricio S. Cardozo, Joshua D. Montgomery & Guillermo W. Rougier (2024)
New mammals from the Upper Cretaceous Allen Formation (Patagonia, Argentina) and reassessment of meridiolestidan diversity.
Cretaceous Research 105935
doi: https://doi.org/10.1016/j.cretres.2024.105935
https://www.sciencedirect.com/science/article/abs/pii/S0195667124001083


Highlights

New species of Late Cretaceous dryolestoid mammal identified from Argentina
Dentition of new species demonstrates dietary diversity among meridiolestidans
Previously known enigmatic taxa are completed by new specimens
A precocious and diverse herbivore/omnivore guild is present in the Late Cretaceous of South America


Abstract

Dryolestoid mammals are classical members of the Jurassic faunas of Laurasia but mostly absent during the Cretaceous. The reverse is true in Gondwana in general and South America in particular, where meridiolestid dryolestoids are dominant in the Late Cretaceous. We describe here 21 new mammalian specimens from the Upper Cretaceous locality Cerro Tortuga (Allen Formation, Patagonia, Argentina) collected via screenwashing, which we identify as meridiolestid dryolestoids. We recognize a new species of meridiolestid and reassign a previously described specimen to the new taxon. The morphology of these new remains represents a new morphotype in the spectrum of meridiolestid diversity, recording a broadening of trophic adaptations from the ancestral insectivory to the more derived herbivory observed among the later and more derived members of the group. The novel dental morphology helps bridge the anatomy of the plesiomorphic sharp-toothed meridiolestidans with that of the more derived and bunodont mesungulatoids. The new taxon suggests that development of both broad cingulids and complex crown morphology precede the development of the wide compressed roots, bunodonty, and thickened enamel characteristic of derived mesungulatids. Other specimens from the collection are referrable to taxa previously known from the same locality. These provide new information about tooth positioning, dental formula, and overall dental morphology. The new material suggests that Groebertherium, previously regarded as a dryolestid taxon, is in fact a likely member of Meridiolestida.

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Free pdf:

Lars Werdelin (2024)
Hypercanines: Not just for sabertooths
The Anatomical Record (advance online publication)
doi: https://doi.org/10.1002/ar.25510
https://anatomypubs.onlinelibrary.wiley.com/doi/10.1002/ar.25510

Free pdf:
https://anatomypubs.onlinelibrary.wiley.com/doi/epdf/10.1002/ar.25510


Hypercanines are here defined as hypertrophied caniniform teeth, that is, canine teeth that are elongated to serve specific functions in different clades of mammals and their synapsid ancestors. This article presents an overview of the occurrence of hypercanines, their growth, and their function across a broad range of clades. Sabertooth felids and felid-like taxa are found to be unique in having determinate growth (although some Dinocerata may also have this). The most common function of hypercanines among herbivores is found to be sexual display and male–male competition. Three clades of small ruminants have evolved hypercanines that can move within their sockets, although the evolutionary details behind this convergent adaptation have not been worked out.


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