Ben Creisler
Some recent non-dino papers:
Eomadtsoia ragei gen. nov.Â
RaÃl O. GÃmez, Fernando F. Garberoglio & Guillermo W. Rougier (2019)
A new Late Cretaceous snake from Patagonia: Phylogeny and trends in body size evolution of madtsoiid snakes.
Comptes Rendus Palevol (advance online publication)
doi:
https://doi.org/10.1016/j.crpv.2019.09.003 https://www.sciencedirect.com/science/article/abs/pii/S1631068319301770Madtsoiids constitute a successful group of extinct snakes widely distributed across Gondwana and the European archipelago during Late Cretaceous times, surviving in reduced numbers to the Pleistocene. They are renowned for including some of the largest snakes that have ever crawled on earth, yet diverse small madtsoiids are also known. Uncovering the evolutionary trends that led these snakes into disparate body sizes has been hampered mainly by the lack of phylogenetic consensus and the paucity of taxa with novel combinations of features. Here we describe a new large madtsoiid snake based on isolated vertebrae from the La Colonia Formation (MaastrichtianâDanian) of Patagonia, Argentina. A comprehensive phylogenetic analysis recovers Madtsoiidae as a basal ophidian lineage and the new snake as sister to a clade of mostly big-to-gigantic taxa, providing insights into early stages and evolutionary trends towards madtsoiid gigantism.
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Axestemys infernalis sp. nov.ÂÂ
Joyce, Walter G., Brinkman, Donald B., and Lyson, Tyler R. 2019.
A new species of trionychid turtle, Axestemys infernalis sp. nov., from the Late Cretaceous (Maastrichtian) Hell Creek and Lance formations of the Northern Great Plains, USA.
Palaeontologia Electronica 22.3.72 1â28.
doi: Â
https://doi.org/10.26879/949https://palaeo-electronica.org/content/2019/2827-a-new-species-of-trionychidThe Late Cretaceous (Maastrichtian) Hell Creek and Lance formations in the states of North Dakota, South Dakota, Montana, and Wyoming, USA, have yielded rich remains of trionychid turtles, but the alpha taxonomy of the group is still poorly resolved, as most fossils are fragmentary. We here describe a new species of trionychid, Axestemys infernalis sp. nov., based on a rich assortment of skulls, shells, and postcranial remains collected from nine fossiliferous sites spread throughout these formations. The new species is attributable to the Axestemys lineage based on the combined presence of large size, a preneural, and a single lateral hyoplastral process. Axestemys infernalis sp. nov. differs from all Paleogene representatives of Axestemys by lacking elongate free ribs and by possessing costal sculpturing that reaches the margin of the shell. It further differs from the only other Mesozoic representative of the lineage, Axestemys splendidus, a species herein restricted to the Campanian, by possessing a rounded carapace. The available Axestemys infernalis sp. nov. material shows much variation, in particular in regards to the maximum size of individuals and the relative size of callosities, but not enough to warrant recognizing multiple species. Instead, this variation is likely caused by random drift or phenotypic variation that accrued over the course of the approximately 1.36 Ma represented in the Hell Creek Formation.
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Cretodus houghtonorum sp. nov.
We describe a partial skeleton of the Late Cretaceous shark, Cretodus, collected from the Blue Hill Shale (middle Turonian) in north-central Kansas, U.S.A. It consists of 134 disarticulated teeth, 61 vertebrae, 23 placoid scales, and fragments of calcified cartilage. The scale morphology suggests that Cretodus was a rather sluggish shark, and the vertebral morphology affirms its placement into Lamniformes. With a strong tendency towards monognathic heterodonty, the dental morphology indicates that the specimen belongs to a new species, C. houghtonorum, sp. nov., increasing the total known species of Cretodus to five. The five species can be divided into three distinct groups: the longiplicatus/semiplicatus-grade, gigantea/houghtonorum-grade, and crassidens-grade. Cretodus, that successively evolved by broadening the tooth crown. The individual of C. houghtonorum, sp. nov., is estimated to be about 515âcm in total length (TL). Our vertebra-based growth analysis suggests that the shark was about 118âcm TL at birth and that the species had an estimated maximum growth length of 684âcm TL. The large size at birth indicates that the intrauterine cannibalism behavior of embryos seen in extant lamniforms had already evolved by the Late Cretaceous. Where C. houghtonorum, sp. nov., preferred nearshore environments, the specimen co-occurred with isolated teeth of Squalicorax and fragments of two dorsal fin spines of a hybodont shark, circumstantially indicating that the individual of Cretodus fed on the much smaller hybodont and was scavenged by Squalicorax.
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News:
Fossil dig leads to unexpected discovery of 91-million-year-old shark new to science