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[dinosaur] Therapsid endocranial casts + Cabindachelys + pangolins + more






Ben Creisler
bcreisler@gmail.com


Some recent non-dino papers:


J. Benoit, V. Fernandez, P.R. Manger & B.S. Rubidge (2017)
Endocranial Casts of Pre-Mammalian Therapsids Reveal an Unexpected Neurological Diversity at the Deep Evolutionary Root of Mammals.
Brain, Behavior and Evolution (advance online publication)
DOI:10.1159/000481525Â
https://www.karger.com/Journal/Issue/276697



The origin and evolution of the mammalian brain has long been the focus of scientific enquiry. Conversely, little research has focused on the palaeoneurology of the stem group of Mammaliaformes, the Permian and Triassic non-mammaliaform Therapsida (NMT). This is because the majority of the NMT have a non-ossified braincase, making the study of their endocranial cast (sometimes called the âfossil brainâ) problematic. Thus, descriptions of the morphology and size of NMT endocranial casts have been based largely on approximations rather than reliable determination. Accordingly, here we use micro-CT scans of the skulls of 1 Dinocephalia and 3 Biarmosuchia, which are NMT with a fully ossified braincase and thus a complete endocast. For the first time, our work enables the accurate determination of endocranial shape and size in NMT. This study suggests that NMT brain size falls in the upper range of the reptilian and amphibian variation. Brain size in the dicynodont Kawingasaurus is equivalent to that of early Mammaliaformes, whereas the Dinocephalia show evidence of a secondary reduction of brain size. In addition, unlike other NMT in which the endocast has a tubular shape and its parts are arranged in a linear manner, the biarmosuchian endocast is strongly flexed at the level of the midbrain, creating a near right angle between the fore- and hindbrain. These data highlight an unexpected diversity of endocranial size and morphology in NMT, features that are usually considered conservative in this group.

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Cabindachelys landanensis, gen. et sp. nov.

Timothy S. Myers, Michael J. Polcyn, OctÃvio Mateus, Diana P. Vineyard, AntÃnio OlÃmpio GonÃalves and Louis L. Jacobs (2017)
Papers in Palaeontology (advance online publication)
DOI: 10.1002/spp2.1100
http://onlinelibrary.wiley.com/doi/10.1002/spp2.1100/full



A new stem cheloniid turtle, Cabindachelys landanensis, gen. et sp. nov., is represented by a nearly complete skull and partial hyoid collected in lower Paleocene shallow marine deposits, equivalent to the offshore Landana Formation, near the town of Landana in Cabinda, Angola. A partial chelonioid carapace previously reported from this locality is referred here to C. landanensis. Cabindachelys landanensis possesses clear synapomorphies of Pan-Cheloniidae, including a rod-like rostrum basisphenoidale, V-shaped basisphenoid crest, and secondary palate, but also retains a reduced foramen palatinum posterius, unlike most other pan-cheloniids. Phylogenetic analysis suggests that C. landanensis forms a weakly-supported clade with Erquelinnesia gosseleti, Euclastes acutirostris, Euclastes wielandi and Terlinguachelys fischbecki, although a close relationship between the protostegid T. fischbecki and these durophagous pan-cheloniids is unlikely. The PaleoceneâEocene strata near Landana have produced a number of turtle fossils, including the holotype specimen of the pleurodire Taphrosphys congolensis. A turtle humerus collected c. 1 m above the holotype skull of C. landanensis differs from humeri of chelonioids and Taphrosphys, indicating that a third turtle taxon is present at Landana. Cheloniid fossil material is rare in the Landana assemblage, in comparison with the abundant remains of Taphrosphys congolensis found throughout the stratigraphic section. This disparity implies that C. landanensis preferred open marine habitats, whereas Taphrosphys congolensis spent more time in nearshore environments. The appearance of new durophagous species such as C. landanensis in the early Paleocene reflects the rapid radiation of pan-cheloniids as they diversified into open niches following the KâPg extinction.




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Philippe Gaubert, Agostinho Antunes, Hao Meng, Lin Miao, StÃphane PeignÃ, Fabienne Justy, Flobert Njiokou, Sylvain Dufour, Emmanuel Danquah, Jayanthi Alahakoon, Erik Verheyen, William T Stanley, Stephen J OâBrien, Warren E Johnson & Shu-Jin Luo (2017)
The complete phylogeny of pangolins: scaling up resources for the molecular tracing of the most trafficked mammals on Earth.
Journal of Heredity, esx097 (advance online publication)
doi: https://doi.org/10.1093/jhered/esx097
https://academic.oup.com/jhered/article-abstract/doi/10.1093/jhered/esx097/4622594?redirectedFrom=fulltext



Pangolins, considered the most-trafficked mammals on Earth, are rapidly heading to extinction. Eight extant species of these African and Asian scale-bodied anteaters are commonly recognized, but their evolutionary relationships remain largely unexplored. Here we present the most comprehensive phylogenetic assessment of pangolins, based on genetic variation of complete mitogenomes and nine nuclear genes. We confirm deep divergence among Asian and African pangolins occurring not later than the Oligocene-Miocene boundary ca. 23 million-years-ago (Ma) (95% HPD=18.7â27.2), limited fossil evidence suggesting dispersals from Europe. We recognize three genera including Manis (Asian pangolins), Smutsia (large African pangolins) and Phataginus (small African pangolins), which first diversified in the Middle-Upper Miocene (9.8â13.3 Ma) through a period of gradual cooling coinciding with a worldwide taxonomic diversification among mammals. Based on large mitogenomic distances among the three genera (18.3â22.8%) and numerous (18) morphological traits unique to Phataginus, we propose the subfamily Phatagininae subfam. nov. to designate small African pangolins. In contrast with the morphological-based literature, our results establish that the thick-tailed pangolin (M.crassicaudata) is sister-species of the Sunda (M. javanica) and Palawan (M. culionensis) pangolins. Mitogenomic phylogenetic delineations supported additional pangolin species subdivisions (n=13), including six African common pangolin (P. tricuspis) lineages, but these patterns were not fully supported by our multi-locus approach. Finally, we identified over 5,000 informative mitogenomic sites and diagnostic variation from five nuclear genes among all species and lineages of pangolins, providing an important resource for further research and for effectively tracing the worldwide pangolin trade.



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R.M. Joeckel, G.A. Ludvigson & J.I. Kirkland (2017)
Lower Cretaceous paleo-Vertisols and sedimentary interrelationships in stacked alluvial sequences, Utah, USA.
Sedimentary Geology 361: 1-24
doi: https://doi.org/10.1016/j.sedgeo.2017.09.009ÂÂ
http://www.sciencedirect.com/science/article/pii/S0037073817301987?via%3Dihub


The Yellow Cat Member of the Cedar Mountain Formation in Poison Strip, Utah, USA, consists of stacked, erosionally bounded alluvial sequences dominated by massive mudstones (lithofacies Fm) with paleo-Vertisols. Sediment bodies within these sequences grade vertically and laterally into each other at pedogenic boundaries, across which color, texture, and structures (sedimentary vs. pedogenic) change. Slickensides, unfilled (sealed) cracks, carbonate-filled cracks, and deeper cracks filled with sandstone; the latter features suggest thorough desiccation during aridification. Thin sandstones (Sms) in some sequences, typically as well as laminated to massive mudstones (Flm) with which they are interbedded in some cases, are interpreted as avulsion deposits. The termini of many beds of these lithofacies curve upward, parallel to nearby pedogenic slickensides, as the features we call âturnups.â Turnups are overlain or surrounded by paleosols, but strata sheltered underneath beds with turnups retain primary sedimentary fabrics. Turnups were produced by movement along slickensides during pedogenesis, by differential compaction alongside pre-existing gilgai microhighs, or by a combination of both. Palustrine carbonates (lithofacies C) appear only in the highest or next-highest alluvial sequences, along with a deep paleo-Vertisol that exhibits partially preserved microrelief at the base of the overlying Poison Strip Member. The attributes of the Yellow Cat Member suggest comparatively low accommodation, slow accumulation, long hiatuses in clastic sedimentation, and substantial time intervals of subaerial exposure and pedogenesis; it appears to be distinct among the members of the Cedar Mountain Formation in these respects.

News:

https://phys.org/news/2017-11-soil-clues-ancient-climate.html