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[dinosaur] Maotherium jaws and dentition + Cretaceous crocodyliform âswim tracksâ from Mongolia

Ben Creisler

New non-dino papers

Thorsten Plogschties & Thomas Martin (2019)
New information on the maxilla, dentary, and dentition of Maotherium sinense, with comments on the zhangheotheriid dental formulae.
PalZ (advance online publication)
DOI: https://doi.org/10.1007/s12542-019-00460-3

Based on a 3D reconstruction, a partial "symmetrodontan" skull from the Yixian Formation, Lujatun Member (Jehol Group) in northeastern China, is assigned to Maotherium sinense. The skull is preserved three-dimensionally including the right mandible, and parts of the maxilla, as well as two upper and eight lower teeth. The dental formula of the studied specimen is ?I, C, 2P, 4M/?i, c, 3p, 5m, and it lacks an m6 which is present in the holotype of M. sinense. No developing teeth inside the maxilla and mandible have been detected, and according to the almost unworn condition of the teeth, the specimen is a young adult. Our studied specimen and Zhangheotherium quinquecuspidens have the same postcanine tooth count of 2P/3p and 4M/5m. Among zhangheotheriids, the early diverged Kiyatherium and Anebodon have a higher number of premolars and a lower number of molars, whereas it is vice versa for the more derived Maotherium and Zhangheotherium.


Yuong-Nam Lee, Hang-Jae Lee, Yoshitsugu Kobayashi, Ariana Paulina-Carabajal, Rinchen Barsbold, Anthony R. Fiorillo & Khishigjav Tsogtbaatar (2019)
Unusual locomotion behaviour preserved within a crocodyliform trackway from the Upper Cretaceous Bayanshiree Formation of Mongolia and its palaeobiological implications.
Palaeogeography, Palaeoclimatology, Palaeoecology (advance online publication)
doi: https://doi.org/10.1016/j.palaeo.2019.109239


The first report of crocodyliform âswim tracksâ in the Late Cretaceous of Asia
The first evidence for punting behaviour of a fossil crocodyliform
Conspicuous dragging behaviour during bottom walking
Division into two categories of crocodyliform "swim tracks"


Crocodyliform tracks are reported from the Upper Cretaceous (?Cenomanian-Santonian) Bayanshiree Formation in southeastern Mongolia. Ten tracks are preserved as natural casts, forming a trackway with a quadrupedal gait pattern with a tail trail. All tracks are short and wide, and dominated by toe traces without plantar impressions. Pes tracks are characterized by four deep claw impressions and push-back marks behind them. Manus tracks have shallow claw marks and long, sub-parallel scratch marks behind. The preferential association of the scratch marks with only the distal digit impressions and irregular pattern of footfalls suggests that this trackway was made by a bottom walking and punting crocodyliform under water. This trackway represents the first crocodyliform "swim tracks" in the Late Cretaceous of Asia and the first evidence for punting behaviour of a fossil crocodyliform. It shows that crocodylians already adopted a very similar behaviour of bottom walking to extant crocodylians in the Cretaceous. The"swim tracks" of crocodyliforms can be divided into two categories such as bottom walking tracks with punting for moving somewhat more quickly and subaqueous walking tracks without punting to be associated with slower underwater speeds.


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