Neuroanatomy of the nodosaurid Struthiosaurus austriacus (Dinosauria: Thyreophora) supports potential ecological differentiations within Ankylosauria

Abstract

Nodosauridae is a group of thyreophoran dinosaurs characterized by a collar of prominent osteoderms. In comparison to its sister group, the often club-tailed ankylosaurids, a different lifestyle of nodosaurids could be assumed based on their neuroanatomy and weaponry, e.g., regarding applied defensive strategies. The holotype of the nodosaurid Struthiosaurus austriacus consists of a single partial braincase from the Late Cretaceous of Austria. Since neuroanatomy is considered to be associated with ecological tendencies, we created digital models of the braincase based on micro-CT data. The cranial endocast of S. austriacus generally resembles those of its relatives. A network of vascular canals surrounding the brain cavity further supports special thermoregulatory adaptations within Ankylosauria. The horizontal orientation of the lateral semicircular canal independently confirms previous appraisals of head posture for S. austriacus and, hence, strengthens the usage of the LSC as proxy for habitual head posture in fossil tetrapods. The short anterior and angular lateral semicircular canals, combined with the relatively shortest dinosaurian cochlear duct known so far and the lack of a floccular recess suggest a rather inert lifestyle without the necessity of sophisticated senses for equilibrium and hearing in S. austriacus. These observations agree with an animal that adapted to a comparatively inactive lifestyle with limited social interactions.

Endocast, brain, and bones: Correspondences and spatial relationships in squamates

“…Cranial endocasts are used to investigate the neuroanatomy of both extant and extinct vertebrates (e.g., Aristide et al, 2019; Benoit et al, 2017; Beyrand et al, 2019; Iwaniuk et al, 2020; Lautenschlager et al, 2018; Lynch & Allen, 2022; Schade et al, 2022; Weisbecker et al, 2021; Zhu et al, 2020). Virtual endocasts, generated by the increasingly widespread use of computed tomographic scanning, provide the potential to track evolution of brain external morphology through deep time, and the possibility to infer cognitive and sensory abilities, as well as behavior, of taxa (e.g., Balanoff & Bever, 2017; Dozo et al, 2022; Holloway et al, 2009; Jerison, 1973; Neubauer, 2014; Racicot, 2021).…”

Divergent strategies in cranial biomechanics and feeding ecology of the ankylosaurian dinosaurs

“…The unique body plan of ankylosaurs has prompted efforts to infer the functional significance of their bizarre characteristics and reconstruct their palaeobiology. Neuroanatomical studies have revealed an interesting morphological diversity of endocranial structures among ankylosaurs, which suggest an array of different sensory capabilities and behaviours, and that ankylosaurids were more active and socially complex than nodosaurids 5 – 9 . The ankylosaur appendicular musculoskeletal system was also unique among ornithischians, related to the acquisition of their specific mode of graviportal, quadrupedal posture and locomotion 10 – 12 .…”

They call me the wanderer – Neurovascular anatomy of dwarfed dinosaur implies precociality in sauropods

“…3, 12, 13 ). However, the floccular recess seems not to be a reliable proxy for the size of the actual neural tissue, also containing e.g., vascular tissue 11 , making its potential use problematic 14 . Whereas most sauropod taxa seem not to spot even the slightest floccular recess on the endocast (see e.g.…”

“…The flocculus is part of the cerebellum and involved in the integration and translation of eye, head and neck movements (VOR, vestibulo-ocular reflex; VCR, vestibulo-collic reflex; see e.g. 11 ). In many previous studies, the floccular recess has been treated as a proxy for the actual cerebellar structure, which induced ecological inferences in fossil taxa (e.g.…”