Testing for a dietary shift in the Early Cretaceous ceratopsian dinosaur Psittacosaurus lujiatunensis

Abstract

Many dinosaurs may have shown ecological differentiation between hatchlings and adults, possibly because of the great size differential. The basal ceratopsian Psittacosaurus lujiatunensis is known from thousands of specimens from the Lower Cretaceous of China and these include many so-called 'juvenile clusters.' During the early stages of ontogeny, P. lujiatunensis underwent a posture shift from quadrupedal to bipedal, and a dietary shift has also been postulated. In this study, we made a 2D mechanical analysis of the jaws of a hatchling and an adult to determine the differences between the two systems; we found some differences, but these were only modest. The adult was better suited to feeding on tough plant material than the hatchling, based on its higher values of absolute and relative bite forces and higher values of mechanical advantage, but there were no substantial shifts in jaw shape or function.

Case study of the convergent evolution in the color patterns in the freshwater bivalves

“…For instance, well-preserved hadrosaurid coprolites from the Late Cretaceous of Montana, U.S.A. include sizeable crustaceans and mollusks, possibly suggesting that the Cretaceous freshwater mollusks were consumed by these herbivorous dinosaurs 42 . In addition, some basal ceratopsian psittacosaurids are hypothesized for the durophagy based on the predicted large bite force in the caudal portion of the toothrow 43 . Among saurischians, some oviraptorosaurian theropods are indicated to consume mollusks with hard shells based on their mandibular features 44 .…”

How Triceratops got its face: An update on the functional evolution of the ceratopsian head

“…These similar values came about in different ways, however, with decreased adductor angles in ceratopsids compared to increased adductor angles in some hadrosaurids, which speaks to the multivariate nature of adaptations in the feeding apparatus that can deliver similar results (Nabavizadeh, 2016). Landi et al (2021) performed the first ontogenetic study of ceratopsian feeding mechanics by analyzing lever arm mechanics in Psittacosaurus specimens (one hatchling and one adult). They reconstructed cranial musculature onto 3D scans of these specimens using all relevant landmarks.…”

“…They reconstructed cranial musculature onto 3D scans of these specimens using all relevant landmarks. Their results showed higher mechanical advantage values overall in the adult, implying a diet of slightly tougher vegetation than its young, highlighting an ecological shift throughout its lifetime (also coinciding with a unique ontogenetic shift from quadrupedality to bipedality in Psittacosaurus ) (Landi et al, 2021). Further future studies such as this one would give us a greater understanding of ontogenetic shifts in feeding ecologies and how it relates to the large‐scale evolution of ceratopsian ecology as a whole.…”

“…The sophisticated feeding apparatus in ceratopsian dinosaurs functioned in large part due to its equally sophisticated cranial muscle architecture (Figures 7-9), which has been reconstructed and discussed for well over a century (Haas, 1955;Holliday, 2009;Landi et al, 2021;Lull, 1908;Mallon & Anderson, 2015;Nabavizadeh, 2016Nabavizadeh, , 2020aNabavizadeh, , 2020bOstrom, 1964Ostrom, , 1966Russell, 1935;Sereno et al, 2010;Tanoue, Grandstaff, et al, 2009;Taylor et al, 2017). Temporal musculature (Figure 8)-the triple-layered m. adductor mandibulae externus (mAME) muscle complex as well as m. pseudotemporalis (mPST)-originates along the inner rim of the supratemporal fenestra.…”

“…Landi et al (2021) performed the first ontogenetic study of ceratopsian feeding mechanics by analyzing lever arm mechanics in Psittacosaurus specimens (one hatchling and one adult). They reconstructed cranial musculature onto 3D scans of these specimens using all relevant landmarks.…”