Brent Adrian, Heather F. Smith, Christopher R. Noto, and Aryeh Grossman (2019)
A new baenid, "Trinitichelys" maini sp. nov., and other fossil turtles from the Upper Cretaceous Arlington Archosaur Site (Woodbine Formation, Cenomanian), Texas, USA.
Palaeontologia Electronica 22.3.81 1â29.
doi:
https://doi.org/10.26879/1001https://palaeo-electronica.org/content/2019/2876-arlington-archosaur-turtlesFree pdf:
https://palaeo-electronica.org/content/pdfs/1001.pdfThe Arlington Archosaur Site (AAS) is a Cenomanian (93-99 Mya) fossil locality in the Woodbine Formation of Texas. Woodbine deposits form primarily terrigenous near shore and shallow marine depositional systems, including shelf, deltaic, and fluvial environments. The AAS is the oldest Upper Cretaceous unit in the Gulf Coastal Plain, and the most complete fossil ecosystem discovered in southwestern Appalachia. It preserves a freshwater/brackish wetland situated in a low-lying coastal plain. The site contains diverse fossil vertebrate and invertebrate faunas and abundant carbonized plant material. The taphonomy of the site is complex, frequently resulting in fragmentary specimens due to a mixture of environmental transport, biological accumulation, pervasive crocodyliform predation, massive storms, wildfires, and widespread flooding events. Numerous new reptilian taxa (particularly crocodyliform) have been recently described, but turtles from the site have not been taxonomically identified. This study documents fossil shell material of AAS turtles, most of which were previously unknown from the site. Results include a new baenid species, "Trinitichelys" maini sp. nov., numerous elements of the helochelydrid Naomichelys, a small trionychid, and a bothremydid. Insights from the turtle faunas at the AAS contribute to our growing understanding of the coastal ecosystems of southwestern Appalachia at the beginning of the Upper Cretaceous.
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Wei Wang, ÂFeimin Ma & ÂChun Li (2019)
First subadult specimen of Psephochelys polyosteoderma (Sauropterygia, Placodontia) implies turtleâlike fusion pattern of the carapace
Letters in Palaeontology (advance online publication)
doi:
https://doi.org/10.1002/spp2.1293https://onlinelibrary.wiley.com/doi/10.1002/spp2.1293Placodonts are a group of turtleâlike animals, including placochelyids that are restricted entirely to the Triassic Tethyan realm. Their fossil remains are rare compared with other contemporaneous marine reptiles. Here, we report the first subadult specimen of the placochelyid Psephochelys polyosteoderma from southâwestern China. It is the most complete specimen of this taxon known. The new fossil is referred confidently to Psephochelys polyosteoderma on the basis of the narrow and spatulate rostrum, toothless premaxillae, and carapace composed of small and numerous armour plates with relatively smooth surfaces. The new specimen provides additional anatomical information for Psephochelys polyosteoderma including the presence of transverse processes on the dorsal vertebrae lacking anteroposterior expansion, and a phalangeal formula in the pes of 1â2â3â4â2. The phylogeny of placodonts, especially the family Placochelyidae, is revised based on a character matrix incorporating additional postcranial characters. This resulted in a betterâresolved tree when compared with previous studies, with Psephochelys as a derived genus within Placochelyidae. On comparison with the adult holotype specimen, the incompletely developed armour in the new specimen reveals a fusion pattern of the carapace beginning with the axial and marginal regions. This surface fusion pattern resembles the ontogenetic process in the embryonic turtle shell, hinting at a possible deep homology with their common diapsid ancestor.