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[dinosaur] Nothosaurus cristatus + Azendohsaurus bone histology + Rhinochelys anatomy + more

Ben Creisler

New non-dino papers:

Nothosaurus cristatus sp. nov.Â

Juliane K. Hinz, Andreas T. Matzke & Hans-Ulrich Pfretzschner (2019)
A new nothosaur (Sauropterygia) from the Ladinian of Vellberg-Eschenau, southern Germany.
Journal of Vertebrate Paleontology Article: e1585364

A new species of Nothosaurus from the Lower Keuper (Lettenkeuper, Ladinian, Erfurt Formation) of Vellberg-Eschenau, southern Germany, is described on the basis of a nearly complete skull that is only missing the lower jaw. Together with Nothosaurus edingerae, it is the only valid Nothosaurus species exclusively known from the Lower Keuper (Ladinian) of the Germanic Basin. Nothosaurus cristatus, sp. nov., differs from all other nothosaurs by exhibiting a postorbital that is excluded from the orbital margin by the postfrontal, the maxilla, and the jugal. The postfrontal and the maxilla form the posterior orbital margin exclusively. The parietal forms a pronounced and sharp crest anterior to the parietal foramen, which is unique among Nothosaurus. The ectopterygoid bears a long posterior process. A phylogenetic analysis of Nothosaurus cristatus, based on Liu et al. (2014, Scientific Reports 4:7142, doi: 10.1038/srep07142) with modified characters after Lin et al. (2017, Journal of Vertebrate Paleontology, doi: 10.1080/02724634.2017.1278703), yielded a nearly unchanged topology that supported the monophyly of (N. jagisteus (N. cristatus (N. mirabilisâ+âN. tchernovi))).


Jorge Cubo and Nour-Eddine Jalil (2019)Â
Bone histology of Azendohsaurus laaroussii: Implications for the evolution of thermometabolism in Archosauromorpha.
Paleobiology 45(2): 317-330

This paper is aimed at constraining the phylogenetic frame of the acquisition of endothermy by Archosauromorpha. We analyzed the bone histology of Azendohsaurus laaroussii. Stylopodial and zeugopodial bones show three tissue types: (1) avascular lamellar zonal bone formed at low growth rates; (2) a scaffold of parallel-fibered bone containing either small primary osteons or simple vascular canals; and (3) fibrolamellar bone formed at high growth rates. We used quantitative histology to infer the thermometabolic regime of this taxon. We define endothermy as the presence of any mechanism of nonshivering thermogenesis that increases both body temperature and resting metabolic rate. Thus, estimating the resting metabolic rate of an extinct organism may be a good proxy to infer its thermometabolic regime (endothermy vs. ectothermy). High resting metabolic rates have been shown to be primitive for the clade ProlacertaâArchosauriformes. Therefore, we inferred the resting metabolic rates of A. laaroussii, a sister group of this clade, and of 14 extinct related taxa, using phylogenetic eigenvector maps. All the inferences obtained are included in the range of variation of resting metabolic rates measured in mammals and birds, so we can reasonably assume that all these taxa (including Azendohsaurus) were endotherms. A parsimony optimization of the presence of endothermy on a phylogenetic tree of tetrapods shows that this derived character state was acquired by the last common ancestor of the clade AzendohsaurusâArchosauriformes and that there is a reversion in Crocodylia.


Free pdf:

Serjoscha W. Evers, Paul M. Barrett & Roger B. J. Benson (2019)
Anatomy of Rhinochelys pulchriceps (Protostegidae) and marine adaptation during the early evolution of chelonioids.Â
PeerJ 7:e6811

Free pdf:

Knowledge of the early evolution of sea turtles (Chelonioidea) has been limited by conflicting phylogenetic hypotheses resulting from sparse taxon sampling and a superficial understanding of the morphology of key taxa. This limits our understanding of evolutionary adaptation to marine life in turtles, and in amniotes more broadly. One problematic group are the protostegids, EarlyâLate Cretaceous marine turtles that have been hypothesised to be either stem-cryptodires, stem-chelonioids, or crown-chelonioids. Different phylogenetic hypotheses for protostegids suggest different answers to key questions, including (1) the number of transitions to marine life in turtles, (2) the age of the chelonioid crown-group, and (3) patterns of skeletal evolution during marine adaptation. We present a detailed anatomical study of one of the earliest protostegids, Rhinochelys pulchriceps from the early Late Cretaceous of Europe, using high-resolution ÎCT. We synonymise all previously named European species and document the variation seen among them. A phylogeny of turtles with increased chelonioid taxon sampling and revised postcranial characters is provided, recovering protostegids as stem-chelonioids. Our results imply a mid Early Cretaceous origin of total-group chelonioids and an early Late Cretaceous age for crown-chelonioids, which may inform molecular clock analyses in future. Specialisations of the chelonioid flipper evolved in a stepwise-fashion, with innovations clustered into pulses at the origin of total-group chelonioids, and subsequently among dermochelyids, crown-cheloniids, and gigantic protostegids from the Late Cretaceous.


Also, only posted as an abstract for now:

"Captorhinus kieranensis"

Michael DeBraga, Joseph J. Bevitt and Robert Reisz (2019)
A new captorhinid from the Permian Cave System near Richards Spur, Oklahoma and the taxic diversity of Captorhinus at this locality.
Frontiers in Earth Science (abstract only)
doi: 10.3389/feart.2019.00112

The early Permian cave system in the Dolese Brothers Limestone Quarry near Richards Spur, Oklahoma represents a unique depositional environment that has been interpreted as preserving an upland biota. The quarry and the region around it represent Paleozoic cave systems that underwent periods of flooding not unlike present-day conditions that are commonly associated with monsoonal episodes. The Richards Spur locality is particularly rich in captorhinid eureptiles which represent one of the earliest reptilian clades to have evolved a specialized dentition. Although the multiple-tooth rowed Captorhinus aguti is the most abundant captorhinid at Richards Spur, at least one other species has been described (Captorhinus magnus) and assigned to the same genus, but five other captorhinid taxa have also been found. We describe a new member of the genus Captorhinus (Captorhinus kieranensis) and explore details of the dental anatomy against the two other members of the genus at Richards Spur, C. aguti and C. magnus, as well as with a member of the genus not presently known from Richards Spur (C. laticeps). Findings suggest that the nature of the ogival dentition described previously as a synapomorphy uniting C. aguti with C. magnus is not supported and we propose a more informative method for differentiating among dental characters within the clade. The discovery of a new species of Captorhinus provides additional evidence for captorhinid taxic diversity at Richards Spur and is supportive of niche partitioning, which is likely associated with reducing intra-specific competition within the clade. Finally, we argue that the captorhinid fossils at Richards Spur likely includes one additional, currently undescribed multiple-tooth rowed form, that renders the current practice of assigning disarticulated cranial remains, specifically dental fragments, to the species C. aguti problematic.

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