Biomechanical simulations reveal a trade-off between adaptation to glacial climate and dietary niche versatility in European cave bears

Abstract

The cave bear is one of the best known extinct large mammals that inhabited Europe during the “Ice Age,” becoming extinct ≈24,000 years ago along with other members of the Pleistocene megafauna. Long-standing hypotheses speculate that many cave bears died during their long hibernation periods, which were necessary to overcome the severe and prolonged winters of the Last Glacial. Here, we investigate how long hibernation periods in cave bears would have directly affected their feeding biomechanics using CT-based biomechanical simulations of skulls of cave and extant bears. Our results demonstrate that although large paranasal sinuses were necessary for, and consistent with, long hibernation periods, trade-offs in sinus-associated cranial biomechanical traits restricted cave bears to feed exclusively on low energetic vegetal resources during the predormancy period. This biomechanical trade-off constitutes a new key factor to mechanistically explain the demise of this dominant Pleistocene megafaunal species as a direct consequence of climate cooling.

Toward an “Ancient” Virtual World: Improvement Methods on X-ray CT Data Processing and Virtual Reconstruction of Fossil Skulls

“…Moreover, it is possible to evaluate mesh integrity of the models and the effects of such virtual processes on mesh geometry and topology. We have here described a complete protocol to process data in order to give solutions for the typical problems encountered by paleontologists and to obtain reliable meshes to be used in different analyses across different fields of research, such as ecomorphology (e.g., Drake, 2011;Figueirido et al, 2011Figueirido et al, , 2015Figueirido, 2018;Pérez-Ramos et al, 2019), histology (e.g., Doube et al, 2010;Figueirido et al, 2018;Syahrom et al, 2018), comparative anatomy (e.g., Miyashita et al, 2011;Van Valkenburgh et al, 2014), and biomechanics (e.g., Wroe et al, 2013;Figueirido et al, 2014;Pérez-Ramos et al, 2020) or phenotypic evolution in general (e.g., Drake, 2011;Polly et al, 2016;Martín-Serra et al, 2019), information that could be later used in more holistic palaecological studies (e.g., Figueirido et al, 2012Figueirido et al, , 2019. In this work, the new protocols presented could be extrapolated to the dataset from nCT.…”

“…Once all these processes have been performed, the resulting 3D mesh models are subject to any kind of evolutionary studies such as those based on ecomorphology or biomechanics. In the case of biomechanical studies, models should be imported into software such as Strand 7 18 (Tseng et al, 2017;Pérez-Ramos et al, 2020).…”

“…In the case of paleontology, this "digital revolution" has substantially changed the way of analyzing the scientific material, generating new fields of research at different levels of analysis that were previously inaccessible (Racicot, 2017). For example, this is the case of histological studies in fossils with non-invasive techniques (i.e., virtual paleohistology; e.g., Sanchez et al, 2012), virtual reconstructions of distorted fossil specimens with lacking parts (i.e., retrodeformation techniques; e.g., Tallman et al, 2014), development of powerful biomechanical models (i.e., finite element analysis; e.g., Figueirido et al, 2014Figueirido et al, , 2018Tseng et al, 2017;Pérez-Ramos et al, 2020), or the study of internal structures, non-accessible without using invasive techniques such as brain endocasts (i.e., paleoneurology; e.g., Cuff et al, 2016) or paranasal sinuses and turbinates (i.e., functional anatomy of internal structures; e.g., Curtis and Van Valkenburgh, 2014;Van Valkenburgh et al, 2014;Matthews and du Plessis, 2016). All these techniques undoubtedly lead to new avenues for future research in the paleobiology of extinct organisms.…”

Rethinking the use of finite element simulations in comparative biomechanics research

“…Based on the surveyed publication dataset, I compiled model results from Prybyla, Tseng & Flynn (2018) , Pérez-Ramos et al (2020) , as well as three additional, new models that complement those in the two published studies to assemble a dataset of 3D cranial FE output data (here on referred to as the “full dataset”; Table 1 ). Data from those studies were chosen because together they represent the largest sample of FE models in the literature constructed using a single protocol, thus reducing confounding factors from differences in FE model construction methodology and software programs used.…”

Morphological evolution of the carnivoran sacrum

“…Van Valkenburgh, 1991; Meachen‐Samuels and Van Valkenburgh, 2009a; Figueirido et al ., 2011), herbivorous (e.g. Figueirido et al ., 2010; Pérez‐Ramos et al ., 2019; van Heteren and Figueirido, 2019; Pérez‐Ramos, 2020) and durophagous (e.g. Palmqvist et al ., 2003; Tseng, 2008; Tseng and Wang, 2010; Palmqvist et al ., 2011; Figueirido et al ., 2013) diets have been revealed in the craniodental skeleton.…”