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Wednesday, October 6th, 2021
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| 8:15a | [Paleontology • 2021] The Largest Theropod Track Site in Yunnan, China: A Footprint Assemblage from the Lower Jurassic Fengjiahe Formation
Abstract Yunnan Province is famous for its diversified Lufeng vertebrate faunas containing many saurischian dinosaur remains. In addition to the body fossil record, dinosaur ichnofossils have also been discovered in Yunnan, and the number of published track sites is on the rise. We report a theropod assemblage from the Lower Jurassic Fengjiahe Formation in Xiyang, central Yunnan. It is the third report and description of dinosaur footprints from the Fengjiahe Formation, and this new track site is the largest in number of footprints for theropods in Yunnan. Over one hundred footprints are preserved on different layers of a claystone-dominated succession close to the Lower-Middle Jurassic boundary. The track area is referred to as a lacustrine shallow-water paleoenvironment. Tracks vary in size, morphology, and preservation. All are tridactyl and digitigrade, and some are identified as undertracks. The best preserved footprints were divided into three morphotypes: morphotype A (>8 cm–<21 cm) resembling Grallator; morphotype B (>27 cm–<30 cm) identified as Kayentapus xiaohebaensis; and morphotype C, an isolated footprint (39 cm) referred to the ichnogenus Kayentapus. Although footprint shape is influenced by many factors, biotic or abiotic, morphological differences among tracks such as size, divarication angles and proportions imply that at least three different kinds of theropods were visiting this site frequently. Theropod body fossils found in the surrounding area, such as Sinosaurus, turn out to be similar in body size to the projected size estimated from footprint lengths at the track site. In Yunnan, discoveries of theropod body fossils are rare. In that respect, the track record is a useful diversity indicator which can help to encompass theropod diversity patterns. Broadly speaking, large predators (five meters long or more) were uncommon in Early Jurassic ecosystems. Accordingly, large tracks are scarce on the track site, but not absent. Trackmakers of all sizes presumably coexisted in this tropical Jurassic ecosystem, and were regularly drawn to the track site in search of water or food resources.
 Conclusions: The Xiyang track site preserves 120 exposed footprints made by solitary coelophysoid and tetanuran theropod dinosaurs within a lacustrine setting under tropical paleoclimatic conditions. The footprints are grouped into three morphotypes and show similarities with two widespread ichnogenera: Grallator and Kayentapus. These ichnogenera were both already reported in the Fengjiahe Formation, but not in its lateral equivalent the Lufeng Formation. The track site is dated from the Late Early Jurassic, and the locality is close to the Lower-Middle Jurassic boundary. In equivalent levels of the Lufeng Formation, typical components of the Lufengosaurus fauna are abundant. Hence, the Xiyang track site can be regarded as part of this fauna. Tracks preserved on multiple layers suggest that this area underwent periodic droughts and flood events. It also implies that dinosaurs of different generations and sizes kept visiting the site. In the Fengjiahe Formation, the record is dominated by body fossils while ichnofossils are relatively limited. Curiously, little is known about tracks in the highly fossiliferous Yunnan Province. This might be due to the small number of previous studies and lack of suitable facies for abundant track preservation. The Xiyang track site is the track site with the greatest number of theropod footprints found and reported in Yunnan so far. Thus, it provides valuable insights into the diversity and ecology of Early Jurassic theropods in Yunnan. Because theropods are relatively sparse in Yunnan, and some genera were erected on basis of scattered specimens, tracks can help fill the gap to some extent.  Hongqing Li, Claire Peyre de Fabrègues, Shundong Bi, Yi Wang and Xing Xu. 2021. The Largest Theropod Track Site in Yunnan, China: A Footprint Assemblage from the Lower Jurassic Fengjiahe Formation. PeerJ 9:e11788. DOI: 10.7717/peerj.11788  | ||||||||
| 9:37a | [Paleontology • 2021] Paradoryphoribius chronocaribbeus • A Tardigrade in Dominican Amber
Abstract Tardigrades are a diverse group of charismatic microscopic invertebrates that are best known for their ability to survive extreme conditions. Despite their long evolutionary history and global distribution in both aquatic and terrestrial environments, the tardigrade fossil record is exceedingly sparse. Molecular clocks estimate that tardigrades diverged from other panarthropod lineages before the Cambrian, but only two definitive crown-group representatives have been described to date, both from Cretaceous fossil deposits in North America. Here, we report a third fossil tardigrade from Miocene age Dominican amber. Paradoryphoribius chronocaribbeus gen. et sp. nov. is the first unambiguous fossil representative of the diverse superfamily Isohypsibioidea, as well as the first tardigrade fossil described from the Cenozoic. We propose that the patchy tardigrade fossil record can be explained by the preferential preservation of these microinvertebrates as amber inclusions, coupled with the scarcity of fossiliferous amber deposits before the Cretaceous. Keywords: Paradoryphoribius, Miocene, invertebrate palaeontology, Eutardigrada 
 Systematic palaeontology Phylum Tardigrada Doyère, 1840 Class Eutardigrada Richters, 1926 Order Parachela Schuster, Nelson, Grigarick and Christenberry, 1980 Superfamily Isohypsibioidea Sands, McInnes, Marley, Goodal-Copestake, Convey and Linse, 2008 Genus Paradoryphoribius gen. nov. (Three letter acronym: Pdo.). Etymology: owing to the close resemblance (para-) to the extant genus Doryphoribius [Gąsiorek, et al. 2019]. Diagnosis: tardigrade with Isohypsibius-type claws (i.e. the basal section and secondary branch form a right angle) with the claw pairs slightly different in shape and size. Accessory points present but not clearly visible. Cuticular bar present between claws of the fourth pair of legs. Pseudolunules absent. Bucco-pharyngeal apparatus consists of a rigid buccal tube with a ventral lamina (ventral apophysis) for the apophyses of the stylet muscle insertion (AISM). No dorsal AISM observed. Pharyngeal apophyses and one thin macroplacoid present, but microplacoids appear absent. Cuticle smooth. Cuticular gibbosities (i.e. cuticular protuberances) may be present. Differential diagnosis: by the presence of Isohypsibius-type claws and ventral lamina, the new genus is morphologically similar to Doryphoribius but differs in the presence of a single thin macroplacoid instead of separated granular-shaped macroplacoids present in Doryphoribius. Paradoryphoribius chronocaribbeus sp. nov. Etymology: from the Greek ‘chrono’ (khronos)—meaning time—in reference to the age of the fossil taxon and ‘caribbeus’ reflecting the region of the type locality. Type locality: Dominican Republic mined from La Cumbre; amber from this region dates to the Miocene, with an approximate age of 16 Ma.  Marc A. Mapalo, Ninon Robin, Brendon E. Boudinot, Javier Ortega-Hernández and Phillip Barden. 2021. A Tardigrade in Dominican Amber. Proc. R. Soc. B. 20211760. DOI: 10.1098/rspb.2021.1760 “Once-in-a generation” tardigrade fossil discovery reveals new species in 16-million-year-old amber Researchers announce just the third-ever tardigrade fossil on record, offering a glimpse into the history of the cryptic micro-animal that has survived five mass extinction events over its 500 million years on Earth.  | ||||||||
| 5:33p | [Paleontology • 2021] Pendraig milnerae • A New Small-sized Coelophysoid Theropod from the Late Triassic of Wales
Abstract We describe a new small-bodied coelophysoid theropod dinosaur, Pendraig milnerae gen. et sp. nov, from the Late Triassic fissure fill deposits of Pant-y-ffynnon in southern Wales. The species is represented by the holotype, consisting of an articulated pelvic girdle, sacrum and posterior dorsal vertebrae, and an associated left femur, and by two referred specimens, comprising an isolated dorsal vertebra and a partial left ischium. Our phylogenetic analysis recovers P. milnerae as a non-coelophysid coelophysoid theropod, representing the first-named unambiguous theropod from the Triassic of the UK. Recently, it has been suggested that Pant-y-ffynnon and other nearby Late Triassic to Early Jurassic fissure fill faunas might have been subjected to insular dwarfism. To test this hypothesis for P. milnerae, we performed an ancestral state reconstruction analysis of body size in early neotheropods. Although our results indicate that a reduced body size is autapomorphic for P. milnerae, some other coelophysoid taxa show a similar size reduction, and there is, therefore, ambiguous evidence to indicate that this species was subjected to dwarfism. Our analyses further indicate that, in contrast with averostran-line neotheropods, which increased in body size during the Triassic, coelophysoids underwent a small body size decrease early in their evolution. Keywords: Coelophysoidea, Theropoda, body size evolution, Pendraig, osteology, Triassic
Systematic palaeontology Archosauria Cope, 1869–1870 Dinosauria Owen, 1842 Theropoda Marsh, 1881 Neotheropoda Bakker, 1986 Coelophysoidea Nopcsa, 1928 Pendraig milnerae gen. et sp. nov. Etymology: Pendraig from the Welsh Pen (head, chief or top) and Draig (dragon), literally meaning ‘chief dragon’ but used in a figurative sense in Medieval Welsh to mean ‘chief warrior’. The anglicized form, Pendragon, was the epithet of Uther, father of King Arthur in medieval legend. Milnerae, in honour of Dr Angela C. Milner (1947–2021), in recognition of her major contributions to vertebrate palaeontology, including as one of the leading experts on British theropod dinosaur fossils, and to the Natural History Museum, London, where the type specimen is held. Diagnosis. Pendraig milnerae is a small-sized non-averostran theropod (estimated femoral length: 10.21 cm; lower 95% CI: 8.60 cm; upper 95% CI: 12.08 cm; see below) that differs from other dinosaurs in the following unique combination of character states present in the holotype (autapomorphies indicated with an asterisk): posteriormost dorsal vertebrae with a strongly elongated centrum (centrum length ca 2.6 times its anterior height), ilium with a distinctly anteroventrally slanting dorsal margin of the preacetabular process, and posterodorsal margin of the postacetabular process curving abruptly posteroventrally and, as a result, the posteroventral end of the process is formed by an acute angle of approximately 65° in lateral view*; pubis with pubic fenestra; ischium with well-developed obturator plate but without posteroventral projection forming a deep U-shaped or V-shaped notch with the shaft; and femur with fourth trochanter posteriorly developed to a height similar to the mid-depth of the shaft at that level. In addition, the referred middle–posterior dorsal vertebra differs from other early neotheropods in the absence of an accessory hyposphene–hypantrum articulation, and the presence of an anteriorly expanded neural spine*. 
Stephan N. F. Spiekman, Martín D. Ezcurra, Richard J. Butler, Nicholas C. Fraser and Susannah C. R. Maidment. 2021. Pendraig milnerae, A New Small-sized Coelophysoid Theropod from the Late Triassic of Wales. Royal Society Open Science. 8(10); DOI: 10.1098/rsos.210915 |
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