Magallanodon terrwerr, new gondwanatherian mammal from Late Cretaceous of Argentina + Jiucaiyuangnathus (Triassic therocephalian) additional material

[Ben Creisler]

Ben Creisler

bcre...@gmail.com

Recent papers:

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Magallanodon terrwerr sp. nov.

Nicolás R. Chimento, Federico L. Agnolín, Damián Moyano-Paz, Makoto Manabe,Takanobu Tsuihiji & Fernando E. Novas (2025)
New fossil mammal remains from the Chorrillo Formation (Maastrichtian, Upper Cretaceous), Santa Cruz Province, Argentina
Journal of Vertebrate Paleontology: e2531263
doi: https://doi.org/10.1080/02724634.2025.2531263
https://www.tandfonline.com/doi/full/10.1080/02724634.2025.2531263


Study of the outcrops of the Chorrillo Formation (Upper Cretaceous, Patagonia, Argentina), resulted in the discovery of a large number of new vertebrates, including mammals, such as the first Cretaceous platypus from South America, gondwanatherians, and a large therian. The aim of the present contribution is to describe new mammalian remains from the Chorrillo Formation. The new specimens include remains of the gondwanatherian Magallanodon baikashkenke, the new species Magallanodon terrwerr, the first report of meridiolestidans (Orretherium, a small indeterminate meridiolestidan and a large indeterminate mesungulatoid), new remains of the therian Patagomaia chainko, and new poscranial remains of indeterminate mammals. The analysis of the Magallanodon terrwerr sp. nov. allowed to modify previous identifications of the isolated molariforms of gondwanatherians. In addition, the tooth assigned to Orretherium expands the knowledge of the upper molariform anatomy of this species. The remains assigned to an indeterminate mesungulatoid are larger than any known Mesozoic meridiolestidan. In comparisons with other fossiliferous localities, Chorrillo/Dorotea Formation mammal assemblage is one of the more diverse known faunas, represented by 6 different taxa, which is only surpassed by the Los Alamitos Formation, with 11 described species. Further, the presence of a monotreme, a very large therian, and Magallanodon indicate that these southern assemblages were far different from those coming from northern Patagonia, a hypothesis supported by other faunal evidence.

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Jun Liu & Fernando Abdala (2025)
Additional material of Jiucaiyuangnathus confusus (Therocephalia) from the Lower Triassic Jiucaiyuan Formation, Xinjiang, China
The Anatomical Record (advance online publication)
doi: https://doi.org/10.1002/ar.70039
https://anatomypubs.onlinelibrary.wiley.com/doi/10.1002/ar.70039


A new baurioid therocephalian, Jiucaiyuangnathus confusus, was recently described from the Lower Triassic Jiucaiyuan Formation of Jimusar, Xinjiang, China. Here, two or three newly collected specimens from the same horizon of Turpan, Xinjiang, including a complete skull with lower jaw and partial skeletons, are referred to this species. The new skull is slightly larger than that of the holotype. Histological features, in conjunction with other anatomical characters, indicate known specimens should be early juveniles with an overall rapid osteogenesis and probably less than 1 year old at death. Different from the holotype, the new specimen has six upper incisors, a short diastema between the last incisor and first maxillary tooth, more distinct canines (and canine boss), and 15 dentary teeth. The new finding indicates that reduced size and/or absence of canine in the juvenile would not be a useful phylogenetic character for therocephalian. The prootics of the new specimen show unreported features from other therocephalians: a prominent medial process (may be present in Olivierosuchus) and strongly folded dorsal margin of the lateral surface. After the description of the new material, the following diagnostic features are proposed for the taxon: maxillary palatal process contacts the premaxillary vomerine process and the vomer; five to six upper incisors. Jiucaiyuangnathus confusus is the best known Baurioidea from Pangea North, and although resembling several features to Ericiolacerta parva of Pangea South, it seems quite likely that most of the similarities are related to both taxa being represented by specimens of early ontogenetic age.