[dinosaur] New lepidosaur species: Clevosaurus hadroprodon + Hoeckosaurus mongoliensis

Ben Creisler

New non-dino papers:

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Clevosaurus hadroprodon sp. nov.Â

Annie S. Hsiou, Randall L. Nydam, Tiago R. SimÃes, FlÃvio A. Pretto, Silvio Onary, AgustÃn G. Martinelli, Alexandre Liparini, Paulo R. Romo de Vivar MartÃnez, Marina B. Soares, Cesar L. Schultz & Michael W. Caldwell (2019)
A New Clevosaurid from the Triassic (Carnian) of Brazil and the Rise of Sphenodontians in Gondwana.
Scientific Reports 9, Article number: 11821Â
DOI: https://doi.org/10.1038/s41598-019-48297-9
https://www.nature.com/articles/s41598-019-48297-9

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https://www.nature.com/articles/s41598-019-48297-9.pdf

The early evolution of lepidosaurs is marked by an extremely scarce fossil record during the Triassic. Importantly, most Triassic lepidosaur specimens are represented by disarticulated individuals from high energy accretion deposits in Laurasia, thus greatly hampering our understanding of the initial stages of lepidosaur evolution. Here, we describe the fragmentary remains of an associated skull and mandible of Clevosaurus hadroprodon sp. nov., a new taxon of sphenodontian lepidosaur from the Late Triassic (Carnian; 237â228 Mya) of Brazil. Referral to Sphenodontia is supported by the combined presence of a marginal dentition ankylosed to the apex of the dentary, maxilla, and premaxilla; the presence of âsecondary boneâ at the bases of the marginal dentition; and a ventrally directed mental process at the symphysis of the dentary. Our phylogenetic analyses recover Clevosaurus hadroprodon as a clevosaurid, either in a polytomy with the Late Triassic to Early Jurassic Clevosaurus and Brachyrhinodon (under Bayesian inference), or nested among different species of Clevosaurus (under maximum parsimony). Clevosaurus hadroprodon represents the oldest known sphenodontian from Gondwana, and its clevosaurid relationships indicates that these sphenodontians achieved a widespread biogeographic distribution much earlier than previously thought.

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Hoeckosaurus mongoliensis sp. nov.ÂÂ

Andrej ÄerÅanskÃ (2019)
The first potential fossil record of a dibamid reptile (Squamata: Dibamidae): a new taxon from the early Oligocene of Central Mongolia.
Zoological Journal of the Linnean Society, zlz047
doi: https://doi.org/10.1093/zoolinnean/zlz047
https://academic.oup.com/zoolinnean/advance-article-abstract/doi/10.1093/zoolinnean/zlz047/5549606

Dibamid reptiles have a known current distribution on two continents (Asia and North America). Although this clade represents an early-diverging group in the Squamata and thus should have a long evolutionary history, no fossil record of these peculiar burrowing squamate reptiles has been documented so far. The fossil material described here comes from the early Oligocene of the Valley of Lakes in Central Mongolia. This material consists of jaws and is placed in the clade Dibamidae on the basis of its morphology, which is further confirmed by phylogenetic analyses. In spite of the fragmentary nature of this material, it thus forms the first, but putative, fossil evidence of this clade. If correctly interpreted, this material demonstrates the occurrence of Dibamidae in East Asia in the Palaeogene, indicating its distribution in higher latitudes than today. The preserved elements possess a unique combination of character states, and a new taxon name is therefore erected: Hoeckosaurus mongoliensis sp. nov. The dentary of Hoeckosaurus exhibits some characters of the two extant dibamid taxa. However, the open Meckelâs groove, together with other characters, show that this group was morphologically much more diverse in the past.

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