Ben Creisler
New papers:
Reticuloolithus acicularis oosp. nov.Â
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Seung Choi & Yuong-Nam Lee (2019)
Possible Late Cretaceous dromaeosaurid eggshells from South Korea: a new insight into dromaeosaurid oology.
Cretaceous Research (advance online publication)
doi:
https://doi.org/10.1016/j.cretres.2019.06.013 https://www.sciencedirect.com/science/article/pii/S019566711930031XHighlights
The first comprehensive study for possible dromaeosaurid (one of the most derived dinosaur groups) eggs.
Application of EBSD technique to find out specific features of possible dromaeosaurid eggshells.
The most updated cladogram (a tree of phylogenetic relationships) of dinosaur eggs.
Abstract
Among non-avian maniraptoran eggshells, oofamilies Prismatoolithidae and Elongatoolithidae are usually associated with troodontid and oviraptorosaur dinosaurs, respectively. However, dromaeosaurid eggshells are poorly known so far except for one possible Deinonychus egg associated with the gastralia of Deinonychus. Since then, some Deinonychus eggshell-like non-prismatoolithid and non-elongatoolithid maniraptoran eggshells have been reported including oogenera Reticuloolithus and Montanoolithus. Here we report a new ootaxon Reticuloolithus acicularis oosp. nov. from the Upper Cretaceous Wido Volcanics in South Korea. R. acicularis is characterized by reticulate ornamentation, an acicular mammillary layer, the continuous layer composed of two sublayers, and no external zone. EBSD analysis shows that R. acicularis has predominant low-angled grain boundaries, thereby its misorientation distribution is very similar to those of oviraptorosaurs and paleognaths. The comparisons to other maniraptoran ootaxa show that R. acicularis is morphologically very similar to Deinonychus eggshell, Paraelongatoolithus, and Nipponoolithus. The phylogenetic analysis based on a revised character matrix in this study shows that R. acicularis, R. hirschi, Paraelongatoolithus, and egg of Deinonychus make a polytomic relationship with the Elongatoolithidae. The new cladogram also raises some issues related to possible homology and homoplasy in the evolution of theropod eggshells. The possible dromaeosaurid affinity of R. acicularis is well matched with the body- and ichno-fossil record of the Cretaceous dromaeosaurids in East Asia. In addition, the low-angled misorientation of R. acicularis may imply the brooding behavior of the dromaeosaurids. Although dromaeosaurid eggshells have never been confirmed yet with embryos in ovo, the results of this study suggest that more possible dromaeosaurid eggshells can be clearly identified with EBSD analysis.
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Digital ichnology allowed 3D comparison of tracks from different tracksites and palaeoenvironments.
Analyses shows that there were two types of apex predators in those palaeoenvironments.
Ichnotaxonomical reviews will profit of digital ichnology.
Faunal exchanges between Gondwana and Laurasia are likely, but routes are not evident.
Introduction.
Abstract
Late Jurassic theropod tracks are very common both in North Africa and Europe. Two recently described ichnotaxa Megalosauripus transjuranicus and Jurabrontes curtedulensis from the Kimmeridgian of Switzerland show the coexistence of two apex predators in the same palaeoenvironment. Similar tracks can be found in tracksites from the Iberian Peninsula and from Morocco. Here, we further explore the similarities among the Swiss ichnotaxa and the other tracks from Germany (Kimmeridgian), Spain (Tithonian-Berriasian), Portugal (Oxfordian-Tithonian) and Morocco (Kimmeridgian) through novel three-dimensional data comparisons. Specimens were grouped in two morphotypes: 1) large and gracile (30â<âFoot Length<50âcm) and 2) giant and robust (FLâ>â50âcm). The analyses show a great morphological overlap among these two morphotypes and the Swiss ichnotaxa (Megalosauripus transjuranicus and Jurabrontes curtedulensis, respectively), even despite the differences in sedimentary environment and age. This suggests a widespread occurrence of similar ichnotaxa along the western margin of Tethys during the Late Jurassic. The new data support the hypothesis of a Gondwana-Laurasia faunal exchange during the Middle or early Late Jurassic, and the presence of migratory routes around the Tethys.
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