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[dinosaur] Phytosaur teeth from India + Atreipus + Ichniotherium + Antiquaobatis

Ben Creisler

Some recent non-dino papers:

Debajit Datta, Nishant Kumar & Sanghamitra Ray (2019)
Taxonomic identification of isolated phytosaur (Diapsida, Archosauria) teeth from the Upper Triassic of India and their significances.
Historical Biology (advance online publication)

Numerous isolated teeth recovered from the Upper Triassic Tiki Formation of India have high, cylindrical, triangular to conical crowns with serrated mesial and distal carinae, and oval/subcircular and elliptical crown bases. Within this overall morphology, the teeth are subdivided into six morphotypes based on crown proportions, nature of carinae and serration and crown-base ratios. These ziphodont teeth are compared with those of other dominant Late Triassic carnivores of India to show similarity with that of the phytosaurs based on their shape, recurved nature, crown proportions, the presence of carina(e), nature of serrations and serration density. The different morphotypes reflect positional heterodonty, and three upper jaw dental sets are identified. This finding is corroborated by PCA, where the morphotypes form distinctly separate clusters, though partial overlapping of these convex hull polygons suggests that these teeth belonged to a single phytosaur taxon. As tripartite dentition is a derived condition; it may be concluded that these isolated teeth belonged to a more derived phytosaur, yet to be recovered from the Tiki Formation. The study highlights the importance of examining isolated teeth in order to identify the fossil forms which are yet to be discovered.


John R. Foster & Martin G. Lockley (2019)
Second occurrence of the dinosauriform ichnogenus Atreipus in the western United States, Upper Triassic Chinle Group of Eastern Utah.
Ichnos (advance online publication)

A newly discovered track in the Chinle Group north of Moab, Utah, is attributable to the ichnogenus Atreipus, an ichnotaxon that is relatively common in eastern North America (Newark Supergroup) but very rare in the Late Triassic of the western part of the continent. This is only the second report of the genus from the Chinle Group. Atreipus has been attributed to a silesaurid dinosauriform, and dinosauriform taxa are relatively abundant by skeletal material in the Late Triassic of western North America, but track evidence in the same units is dominated by ichnotaxa attributed to dinosaurs. The rarity of Atreipus is currently an anomaly in the region.


Heitor Francischini, Spencer G. Lucas, Sebastian Voigt, Lorenzo Marchetti, Vincent L. Santucci, Cassandra L. Knight, John R. Wood, Paula Dentzien-Dias & Cesar L. Schultz (2019)Â
On the presence of Ichniotherium in the Coconino Sandstone (Cisuralian) of the Grand Canyon and remarks on the occupation of deserts by non-amniote tetrapods.
PalZ (advance online publication)

The colonization of deserts by tetrapods occurred for the first time in the late Paleozoic. In spite of amniotes being the most abundant and diverse taxon in such environments, fossil tracks indicate that anamniotes also inhabited late Paleozoic deserts. In this paper, the presence of the tetrapod-footprint ichnotaxa Ichniotherium sphaerodactylum and cf. Ichniotherium is documented in the eolian Coconino Sandstone (early Permian), based on 16 trackways found at several localities in Arizona, USA. Because there is a strong association between Ichniotherium and different species of diadectomorphs, we also discuss some aspects of the ichnotaxonomy of this ichnogenus. Diadectomorpha is considered the sister taxon of Amniota and, as a consequence, the tracks described in this paper represent the oldest evidence of occupation of deserts by non-amniote tetrapods. The presence of Ichniotherium in this environmental context also sheds light on the paleobiology of Diadectomorpha and, as a result, the emergence of features typically related to Amniota. The ichnofauna of the Coconino Sandstone has been used as a model for the Chelichnus ichnofacies, which supposedly indicates a low-diversity desert fauna. On the other hand, the tracks described here demonstrate that diadectomorphs were also important faunal components of such deserts and suggests that the significance of this ichnofacies should be reconsidered.


Also may be of interest (marine reptiles were eating these guys...):Â
Free pdf:

Antiquaobatis grimmenensis gen. et sp. nov.Â

Sebastian Stumpf & JÃrgen Kriwet (2019)
A new Pliensbachian elasmobranch (Vertebrata, Chondrichthyes) assemblage from Europe, and its contribution to the understanding of late Early Jurassic elasmobranch diversity and distributional patterns.
PalZ (advance online publication)

Free pdf:

Here we describe a new, previously unrecognized elasmobranch microfossil assemblage consisting of isolated dental material from late Pliensbachian marginal marine, near-shore deposits of Grimmen in north-eastern Germany. The faunal composition indicates close affinities to other European pre-Toarcian elasmobranch-bearing localities, as it is predominantly composed of Hybodontiformes (Hybodus reticulatus?, H. hauffianus?, Lissodus sp.), Synechodontiformes (Palidiplospinax enniskilleni, P. occultidens, Paraorthacodus sp., Sphenodus sp.), and Hexanchiformes (Notidanoides sp.), as well as teeth attributable of the enigmatic Early Jurassic galeomorph shark Agaleus dorsetensis. In addition, the here reported elasmobranch tooth assemblage includes the oldest undisputable fossil records of Orectolobiformes and Batomorphii, each being represented by a single complete tooth only. The orectolobiform specimen is reminiscent of hemiscyllids but left in open nomenclature due to its very generalized morphology preventing any taxonomic identification. The batomorph tooth, conversely, is characterized by a unique combination of morphological features, which allows the introduction of new genus and species, Antiquaobatis grimmenensis gen. et sp. nov. The fossil assemblage presented here contributes to our current knowledge of late Early Jurassic chondrichthyan diversity and distributional patterns, providing some support for the hypothesis that most modern neoselachian lineages were initially linked to marginal marine, near-shore environments, before moving into open marine, offshore habitats by the Toarcian.


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