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[dinosaur] Purussaurus power bite + fossil pelomedusoid and carettochelyid turtles + iguanian lizard evolution (free pdfs)




Ben Creisler
bcreisler@gmail.com


Some recent non-dino papers withÂfree pdfs:

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Free pdf:

FranÃois Pujos and Rodolfo Salas-Gismondi (2020)
Predation of the giant Miocene caiman Purussaurus on a mylodontid ground sloth in the wetlands of proto-Amazonia.
Biology Letters 16(8): 20200239.
doi: https://doi.org/10.1098/rsbl.2020.0239
https://royalsocietypublishing.org/doi/10.1098/rsbl.2020.0239

Free pdf:
https://royalsocietypublishing.org/doi/pdf/10.1098/rsbl.2020.0239


Thirteen million years ago in South America, the Pebas Mega-Wetland System sheltered multi-taxon crocodylian assemblages, with the giant caiman Purussaurus as the top predator. In these Miocene swamps where reptiles and mammals coexisted, evidence of their agonistic interactions is extremely rare. Here, we report a tibia of the mylodontid sloth Pseudoprepotherium bearing 46 predation tooth marks. The combination of round and bisected, shallow pits and large punctures that collapsed extensive portions of cortical bone points to a young or sub-adult Purussaurus (approx. 4 m in total length) as the perpetrator. Other known crocodylians of the Pebas System were either too small at adulthood or had discordant feeding anatomy to be considered. The pattern of tooth marks suggests that the perpetrator attacked and captured the ground sloth from the lower hind limb, yet an attempt of dismembering cannot be ruled out. This discovery from the Peruvian Amazonia provides an unusual snapshot of the dietary preferences of Purussaurus and reveals that prior to reaching its giant size, young individuals might have fed upon terrestrial mammals of about the size of a capybara.

News:

13 million-year-old bite marks on fossil reveal damage by an ancient caiman relative

https://www.cnn.com/2020/08/25/world/sloth-fossil-bite-marks-scn-trnd/index.html

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Free pdf:

Edwin-Alberto Cadena (2020)
Valanginian occurrence of Pelomedusoides turtles in northern South America: revision of this hypothesis based on a new fossil remain.
https://doi.org/10.7717/peerj.9810
PeerJ 8:e9810
doi: Âhttps://doi.org/10.7717/peerj.9810
https://peerj.com/articles/9810/


Pelomedusoides constitutes the most diverse group of Mesozoic and Cenozoic side-necked turtles. However, when it originated is still being poorly known and controversial. Fossil remains from the Early Cretaceous (Valanginian) Rosa Blanca Formation of Colombia were described almost a decade ago as potentially belonging to Podocnemidoidea (a large subclade inside Pelomedusoides) and representing one of the earliest records of this group of turtles. Here, I revise this hypothesis based on a new fragmentary specimen from the Rosa Blanca Formation, represented by a right portion of the shell bridge, including the mesoplastron and most of peripherals 5 to 7. The equidimensional shape of the mesoplatron allows me to support its attribution as belonging to Pelomedusoides, a group to which the previously podocnemidoid material is also attributed here. Although the Valanginian pelomesudoid material from Colombia is still too fragmentary as to be considered the earliest indisputable record of the Pelomedusoides clade, their occurrence is at least in agreement with current molecular phylogenetic hypotheses that suggest they split from Chelidae during the Jurassic and should occur in the Late Jurassic and Early Cretaceous fossil record.

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Free pdf:


Brent Adrian, Patricia A. Holroyd, J. Howard Hutchison & KE Beth Townsend (2020)
Additional records and stratigraphic distribution of the middle Eocene carettochelyid turtle Anosteira pulchra from the Uinta Formation of Utah, North America.
PeerJ 8:e9775
doi: Âhttps://doi.org/10.7717/peerj.9775
https://peerj.com/articles/9775/



Anosteira pulchra is one of two species of the obligately-aquatic freshwater clade Carettochelyidae (pig-nosed turtles) from the Eocene of North America. Anosteira pulchra is typically rare in collections, and their distribution is poorly documented. The Uinta Formation [Fm.] contains a diverse assemblage of turtles from the Uintan North American Land Mammal Age. Whereas turtles are abundantly preserved in the Uinta Fm., A. pulchra has been reported only from a few specimens in the Uinta C Member.

Methods

We describe new records of Anosteira pulchra from the Uinta Basin and analyze the distribution of 95 specimens from multiple repositories in the previously published stratigraphic framework of the middle and upper Uinta Fm.

Results

Here we report the first records of the species from the Uinta B interval, document it from multiple levels within the stratigraphic section and examine its uncommon appearance in only approximately 5% of localities where turtles have been systematically collected. This study details and extends the range of A. pulchra in the Uinta Fm. and demonstrates the presence of the taxon in significantly lower stratigraphic layers. These newly described fossils include previously unknown elements and associated trace fossils, with new anatomical information presented. This study provides insight into the taxonomy of Anosteira spp. in the middle Eocene, and suggests the presence of a single species, though no synonymy is defined here due to limits in Bridger material.

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Free pdf:

Simon G. Scarpetta (2020)
Combined-evidence analyses of ultraconserved elements and morphological data: an empirical example in iguanian lizards.
Biology Letters 16(8): 20200356.
doi: https://doi.org/10.1098/rsbl.2020.0356
https://royalsocietypublishing.org/doi/10.1098/rsbl.2020.0356

Free pdf:
https://royalsocietypublishing.org/doi/pdf/10.1098/rsbl.2020.0356


Genomic datasets generated by next-generation sequencing are increasingly prevalent in phylogenetics, but morphological data are required to phylogenetically place fossils, corroborate molecular hypotheses and date phylogenies. Combined-evidence analyses provide an integrative assessment of tree topology. However, no attempt has been made to simultaneously analyse next-generation genomic datasets and morphological data, and the future of morphology in the context of genomic data is uncertain. I conducted combined-evidence analyses that include genomic and morphological datasets, specifically, with ultraconserved elements and two morphological matrices. In unweighted maximum-likelihood and Bayesian combined-evidence analyses, morphological signal was dwarfed by the ultraconserved elements, and some node support values were reduced relative to ultraconserved element-only analyses. Increasing the weight of morphological characters allowed those data to influence the tree, but weighting subjectivity should be considered in future analyses. More attempts should be made to simultaneously analyse genomic and morphological datasets.




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