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Alexandria L. Brannick & Gregory P. Wilson (2018)
New Specimens of the Late Cretaceous Metatherian Eodelphis and the Evolution of Hard-Object Feeding in the Stagodontidae.
Journal of Mammalian Evolution (advance online publication)
The Stagodontidae include the largest metatherians known from the Cretaceous of North America. Of the recognized species of the stagodontid genus Eodelphis, E. cutleri is larger and has a more robust dentary, more inflated premolars, and third premolars specialized for crushing, as opposed to the more gracile E. browni. These differences have led to the hypothesis that an E. cutleri-like ancestor gave rise to Didelphodonâanother, mostly younger, stagodontid, which has been interpreted as a durophagous predator-scavenger. If correct, E. cutleri would be expected to show more morphological adaptation toward durophagy than E. browni does. Here, we describe two new dentary fossils referable to E. browni and test the evolutionary hypothesis by applying beam theory to estimate bending force capabilities of 22 dentaries of Cretaceous stagodontids and other metatherians. The resulting diversity of bending force profiles of the sampled dentaries implies that Cretaceous metatherians had a wide range of feeding behaviors. Among the stagodontids, E. cutleri has a mediolateral bending force profile of the dentary that is more similar to that of Didelphodon than it is to that of E. browni; whereas its dorsoventral bending force profile is more similar to that of E. browni. These results indicate that anteriorly the dentary of E. cutleri was capable of resisting high torsional stresses from hard-object feeding but lacked other dorsoventral buttressing associated with exceptionally high bite forces of Didelphodon. Our results imply that some morphological changes associated with durophagy evolved twice within this clade, independently in E. cutleri and Didelphodon.
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D.I. Pashchenko, I.T. Kuzmin, A.G. Sennikov, P.P. Skutschas & M.B. Efimov (2018)Â
On the Finding of Neosuchians (Neosuchia, Crocodyliformes) in the Middle Jurassic (Bathonian) Deposits of the Moscow Region.
Paleontological Journal 2018 5:77-90 (Russian edition)
DOI: 10.1134/S0031031X18050112Â ÂÂ
The remains of neosuchian crocodyliforms (isolated teeth, fragmentary bone from a lower jaw) from the Middle Jurassic (Bathonian) Peski locality in the Moscow Region are described for the first time. Neosuchian from Peski is characterized by the presence of a pronounced ornamentation on the dermal skull bones and bicarinate teeth without serrations, with a triangle-shaped tooth crown, an oval cross-section, and thin striations on the enamel. Similarity of Bathonian vertebrate faunas of the Moscow Region, Great Britain, Western Siberia and Kirgiziya indicates the faunal homogeneity on the territory of Laurasia.
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Eochelone voltregana n. sp.Â
France de Lapparent de Broin, Xabier Murelaga, AdÃn PÃrez-GarcÃa, Francesc FarrÃs, and Jacint Altimiras (2018)
The turtles from the upper Eocene, Osona County (Ebro Basin, Catalonia, Spain): new material and its faunistic and environmental context.
Fossil Record 21: 237-284Â
Eochelone voltregana n. sp. is a new marine cryptodiran cheloniid found at the Priabonian levels (latest Eocene) of the Vespella marls member of the VicâManlleu marls formation. It is the second cheloniid from Santa CecÃlia de Voltregà (Osona County, Spain), the first one being Osonachelus decorata from the same formation. Shell parameters indicate that the new species belongs to a branch of sea turtles including the Eocene AngloâFrancoâBelgian forms Argillochelys, Puppigerus and Eochelone (the shell of the latter was studied here for the first time) as well as Glarichelys from the Oligocene of Switzerland, all of them predating the worldwide living Miocene genera. The description of two other more littoralâcontinental Eocene species is given: Trionyx sp., from an older layer of the same formation; and the podocnemidid erymnochelyine, Cordichelys from a more basal layer of a middle Eocene (Lutetian) formation. The last one is identified as the only evidence of the Shweboemys subgroup in the European record, being distinct from the other known Osona County pleurodire Eocenochelus farresi, which is a member of the Erymnochelys group (same subfamily), from the younger Priabonian Sant Martà Xic layer. Thus, an update on the marine turtle fauna of the eastern Ebro Basin that variably opened in the east during Eocene times is provided. The turtles of Osona County belong to two suborders and five genera with three new species and extend the known distribution of their familiesÂ
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