Dinosaur tracks in Hebei fill gap between Yanliao and Jehol Biotas in China + Kansajsuchus neurocranial anatomy

[Ben Creisler]

Ben Creisler

bcre...@gmail.com

New papers:

Tingyuan Yuan, Huan Xu, Xiaojun Jiang, Yongqing Liu, Hongwei Kuang, Nan Peng, Jun Chen & Chao Cen (2024)
Late Jurassic–Early Cretaceous dinosaur track assemblages from northwestern Hebei Province, China: implications for paleoenvironment and paleoecology
Cretaceous Research 105960
DOI: https://doi.org/10.1016/j.cretres.2024.105960
https://www.sciencedirect.com/science/article/abs/pii/S0195667124001332


The relationship between the Middle–Late Jurassic Yanliao Biota and the Early Cretaceous Jehol Biota has long been unresolved due to an approximately 20 Ma “vertebrate fossil gap”. However, a large number of dinosaur tracks have been reported from the Tuchengzi/Houcheng Formation in northern Hebei–western Liaoning, which occupies the stratigraphic position between the Yanliao Biota and the Jehol Biota. This paper presents new discoveries of diverse dinosaur track assemblages from the Upper Jurassic–Lower Cretaceous Houcheng Formation in the Shangyi Basin, northwestern Hebei Province, China. Based on the ichnological analyses, tracks are assigned to the sauropod Parabrontopodus, theropod Grallator, Anchisauripus, Eubrontes, and Therangospodus. The theropod tracks were likely produced by small-sized feathered theropod dinosaurs (Coelurosauria) that thrived in both the Yanliao Biota and the Jehol Biota. These findings imply that these two biotas evolved successively, without evidence of a complete turnover or extinction of biotas. Sedimentological studies of the tracksites reveal their occurrence in diverse sedimentary environments, including braided sandbar, floodplain, and deltaic plain. The coexistence of highly diverse dinosaur tracks with various preservation environments indicates that the living environment during that time was relatively comfortable. The increased diversity of dinosaur tracks in the upper part of the Houcheng Formation closely aligns with the intense volcanic activity of the Zhangjiakou Formation in northwestern Hebei Province. This suggests that volcanic activity likely served a crucial function in the proliferation of the dinosaur fauna in the Shangyi Basin and northern North China during the earliest Cretaceous.

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Ivan T. Kuzmin, Ekaterina A. Sichinava, Evgeniia V. Mazur & Victor A. Gombolevskiy (2024)
Virtual reconstruction of the neurocranial anatomy of Kansajsuchus extensus (Neosuchia: Paralligatoridae) from the Upper Cretaceous of Tadzhikistan with a review of braincase osteology in Neosuchia
Cretaceous Research 105959
doi: https://doi.org/10.1016/j.cretres.2024.105959
https://www.sciencedirect.com/science/article/abs/pii/S0195667124001320

Highlights

Neurocranial anatomy is described for a paralligatorid crocodylomorph Kansajsuchus extensus from the Upper Cretaceous Kansai locality in Tadzhikistan. It is a first detailed study of neuroanatomy in Paralligatoridae.

CT-scanning, segmentation, and 3D modeling allowed to virtually reconstruct the braincase of K. extensus and produce endocast of its internal cavities for the first time.

Detailed comparison of neurocranial osteology among Neosuchia allowed to trace evolutionary modifications in the braincase through the neosuchian–eusuchian transition.

Dyrosaurids have an unusual structure of neurocranium among Neosuchia. Close affinities of Dyrosauridae and Pholidosauridae are questioned based on significant differences in their braincase structure.

Abstract

The braincase features appear phylogenetically informative and key in assessing the still contentious relationships within Crocodylomorpha. Yet, the neurocrania of many non-crocodylian taxa are imperfectly studied. In the present paper, we describe the braincase osteology and neuroanatomy of a paralligatorid crocodylomorph Kansajsuchus extensus from the Upper Cretaceous Kansai locality in Tadzhikistan based on CT-scanning, segmentation, and 3D modeling. The detailed comparison of K. extensus with other taxa expands our understanding of the neurocranial anatomy and evolution in Neosuchia. The braincase anatomy appears to be relatively consistent across most non-crocodylian neosuchians, but important changes in its structure are traced through the neosuchian–eusuchian transition and especially at the base of Crocodylia. We question the close affinities of Dyrosauridae and Pholidosauridae based on significant differences in their braincases.

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