Endocranial anatomy of the ceratopsid dinosaur Triceratops and interpretations of sensory and motor function

Abstract

Triceratops is one of the well-known Cretaceous ceratopsian dinosaurs. The ecology of Triceratops has been controversial because of its unique morphological features. However, arguments based on brain and inner ear structures have been scarce. In this study, two braincases (FPDM-V-9677 and FPDM-V-9775) were analyzed with computed tomography to generate three-dimensional virtual renderings of the endocasts of the cranial cavities and bony labyrinths. Quantitative analysis, including comparison of linear measurements of the degree of development of the olfactory bulb and inner ear, was performed on these virtual endocasts to acquire detailed neuroanatomical information. When compared with other dinosaurs, the olfactory bulb of Triceratops is relatively small, indicating that Triceratops had a reduced acuity in sense of smell. The lateral semicircular canal reveals that the basicranial axis of Triceratops is approximately 45° to the ground, which is an effective angle to display their horns as well as frill, and to graze. The semicircular canals of Triceratops are relatively smaller than those of primitive ceratopsians, such as Psittacosaurus and Protoceratops, suggesting that sensory input for the reflexive stabilization of gaze and posture of Triceratops was less developed than that of primitive ceratopsians. The cochlear length of Triceratops is relatively short when compared with other dinosaurs. Because cochlear length correlates with hearing frequency, Triceratops was likely adapted to hearing low frequencies.

The rostral neurovascular system of Tyrannosaurus rex

“…The specimen's skull was scanned using computed tomography (CT scanning) to study its internal and external structures in silico. Many subsequent studies applied CT scanning to dinosaur cranial material, focusing mainly on both the braincase and bony labyrinth (Knoll et al, 2006(Knoll et al, , 2012Sereno et al, 2007;Witmer and Ridgely, 2009;Neenan et al, 2019;King et al, 2020;Sakagami and Kawabe, 2020). Recently, an increasing number of studies have focused on the rostral neurovascular anatomy of extant (e.g., Witmer et al, 2008;Leitch and Catania, 2012;Porter andWitmer, 2015, 2016;Jones et al, 2019;Lessner et al, 2019;Lessner and Holliday, 2020) and extinct amniote taxa, including therapsids (Benoit et al, 2016a(Benoit et al, , 2016b(Benoit et al, , 2017b(Benoit et al, , 2019Pusch et al, 2019;Wallace et al, 2019;Pusch et al, 2020;Benoit et al, 2021b;Ekdale and Deméré, 2021), plesiosaurs (Foffa et al, 2014), and archosauromorphs (Lessner et al, 2016;Lessner and Stocker, 2017;Serrano-Martínez et al, 2020;Benoit et al, 2021a), including theropod dinosaurs (Ibrahim et al, 2014(Ibrahim et al, , 2014Barker et al, 2017;Cau, 2020;Cerroni et al, 2020;Porter and Witmer, 2020;Kawabe and Hattori, 2021).…”

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

“…6). The calculated auditory capacities (based on 27 ) impute Europasaurus a relatively wide hearing range with a high upper frequency limit (among non-avian dinosaurs 40,41,42 ). Walsh et al 27 could show a certain correlation between hearing range, complexity of vocalizing and aggregational behaviour in extant reptiles and birds (see also 12, 43 ).…”

Ultraviolet Autofluorescence Microscopy of Nanotyrannus lancensis Sections Reveals Blood Clots in Vessel Canals

“…In recent years, a non-destructive computed tomography (CT) scanning of dinosaur bones has also been employed, resulting in remarkable images of neurovascular and other canals [6,[8][9][37][38][39][40][41][42][43]. This is especially notable with respect to imaging dinosaur jaws (maxillae and mandibles) [8,40,43].…”

“…Soil matrix and metal artifacts can be identified by CT scanning [37], however none of the referenced dinosaur bone CT studies have reported blood products in neurovascular canals. Soft neurovascular elements are not visualized in isolation, and only the cranial cavities are imaged in digital endocasts [42].…”