Similarly, Peterson & Daus (2019) identified feeding traces on a proximal caudal vertebra from an Edmontosaurus (BMR P2007.4.1) likely produced by a T. (2009) based on the strong correlation between the dimensions and spacing of the punctures and the dentition of BMR P2002.4.1 itself ( Figs. These have been interpreted as conspecific bites by Peterson et al. The juvenile specimen used in that study (BMR P2002.4.1) was also found to possess bite marks through the left maxilla and nasal. rex on MDA, suggesting allometric growth in bite force from juvenile to adult. Bates & Falkingham (2012) based their bite force estimate of a late-stage juvenile T. rex, leaving a considerable gap in the understanding of tyrannosaur ontogenetic dietary partitioning and paleoecology. However, bite force estimates have largely focused on adult specimens with few studies providing estimates for juveniles or subadult T. These studies have relied on several methods for estimating bite forces, including multi-body dynamic analysis (MDA) ( Bates & Falkingham, 2012), finite element analysis ( Rayfield, 2005 Rayfield et al., 2007 Maiorino et al., 2015), and actualistic studies. The genus Tyrannosaurus rex and other tyrannosaurids have been the focus of many studies on dinosaur bite force and bite mechanics ( Erickson et al., 1996a Meers, 2002 Barrett & Rayfield, 2006 Bates & Falkingham, 2012 Gignac & Erickson, 2017 Rowe & Snively, 2021 Therrien et al., 2021). A variety of methods have been proposed to determine bite mechanics and bite forces of members of Dinosauria, including stegosaurs, ceratopsians and hadrosaurids ( Weishampel, 1984 Bell, Snively & Shychoski, 2009 Reichel, 2010 Erickson et al., 1996b), and more commonly, theropods ( Rayfield et al., 2001 Rayfield, 2005 Rayfield et al., 2007 Gignac et al., 2010 Lautenschlager et al., 2013). Furthermore, we discuss the implications for feeding mechanisms, feeding behaviors, and ontogenetic niche partitioning.īite mechanics and feeding habits of dinosaurs have long been debated. The results of this study offer further insight into the role of juvenile tyrannosaurs in late Cretaceous ecosystems. These findings are slightly higher than previously estimated bite forces for a juvenile Tyrannosaurus rex of approximately the same size as BMR P2002.4.1 but fall within the expected range when compared to estimates of adult T. Our experimentally derived linear models suggest bite forces up to 5,641.19 N from cortical bone thickness estimated from puncture marks on an Edmontosaurus and a juvenile Tyrannosaurus. Forces required to replicate punctures were recorded and puncture dimensions were measured. The tooth was then pressed into bovine long bones in various locations with differing cortical bone thicknesses at varying speeds for a total of 17 trials. A maxillary tooth of the juvenile Tyrannosaurus specimen BMR P2002.4.1 was digitized, replicated in dental grade cobalt chromium alloy, and mounted to an electromechanical testing system. Here we present bite force estimates for a juvenile Tyrannosaurus rex based on mechanical tests designed to replicate bite marks previously attributed to a T. rex have been traced to juveniles, leaving considerable gaps in understanding ontogenetic changes in bite mechanics and force, and the paleoecological role of juvenile tyrannosaurs in the late Cretaceous. Bite marks attributed to adult Tyrannosaurus rex have been subject to numerous studies.