Highlights
A new specimen of Yabeinosaurus robustus is the largest complete example on record.
Abdominal contents show that this individual had fed on a large crayfish.
Integumentary traces indicate the lizardâs body was strikingly banded in life.
Abstract
The Early Cretaceous lizard Yabeinosaurus is well-represented in the Jehol Biota of northeast China, with specimens yielding information on ontogenetic development, reproductive strategy, and diet, as well as skeletal morphology. However, a large, well-preserved, new specimen of Yabeinosaurus robustus from the Lamadong locality, Liaoning, provides further insights into the morphology and biology of this species. Integumentary traces demonstrate that, in life, Y. robustus was coloured with well-defined light and dark banding through both the body and the tail. The integumentary traces also confirm that Yabeinosaurus was covered with thin, non-overlapping osteoderms, each of which seems to have underlain only part of a scale. Previous specimens have contained fish remains, suggesting that Yabeinosaurus foraged in, or close, to the water. The new specimen supports that hypothesis as it contains the remains of a large crayfish, identified as belonging to the species Palaeocambarus licenti Taylor et al. 1999. Body parts of the crayfish provide an estimated original total length of 120-140 mm.
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Giulio PanascÃ, David J. Varricchio & Ren Hirayama (2019)
New occurrence of Neurankylus sp. (Testudines: Paracryptodiria: Baenidae) in the Upper Cretaceous Frontier Formation of south western Montana (USA).
Cretaceous Research 104318 (advance online publication)
doi:
https://doi.org/10.1016/j.cretres.2019.104318 https://www.sciencedirect.com/science/article/pii/S0195667119302162An incomplete specimen assigned to the genus Neurankylus sp. was collected from Coniacian deposits of the Frontier Formation of Montana (USA). The material consists of anterior plastron, a costal plate and neural plate fragment, and several undetermined skeletal elements. The identification is based on the relatively large size of the specimens, scute elements joining along the mid-line of the plastron with the intergulars reaching the humerals, and complete fusion of the sutures. The specimen represents the first baenid turtle reported from non-marine Frontier Formation deposits and is particularly relevant for understanding stratigraphical and paleogeographical distribution of the Family Baenide. This will have important implications for phylogenetic studies and paleoenvironmental interpretation of non-marine Frontier Formation deposits of south-western Montana.
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The fossil record provides direct empirical data for understanding macroevolutionary patterns and processes. Inherent biases in the fossil record are well known to confound analyses of this data. Sampling bias proxies have been used as covariates in regression models to test for such biases. Proxies, such as formation count, are associated with paleobiodiversity, but are insufficient for explaining species dispersal owing to a lack of geographic context. Here, we develop a sampling bias proxy that incorporates geographic information and test it with a case study on early tetrapodomorph biogeography. We use recently-developed Bayesian phylogeographic models and a new supertree of early tetrapodomorphs to estimate dispersal rates and ancestral habitat locations. We find strong evidence that geographic sampling bias explains supposed radiations in dispersal rate (potential adaptive radiations). Our study highlights the necessity of accounting for geographic sampling bias in macroevolutionary and phylogenetic analyses and provides an approach to test for its effect.