Feeding capability in the extinct giant Siamogale melilutra and comparative mandibular biomechanics of living Lutrinae

Abstract

At 50 kg in estimated weight, the extinct Siamogale melilutra is larger than all living otters, and ranks among the largest fossil otters. The biomechanical capability of S. melilutra jaws as related to their large size is unknown but crucial to reconstructing the species’ potentially unique ecological niche. Here we compare the mandibular biomechanics of S. melilutra using engineering-based performance measures against ten extant otter biomechanical models. Despite a wide range of feeding preferences from durophagy to piscivory, living otter species exhibit a linear relationship between mandible stiffness and volume, as expected in isometric model scaling. In contrast, S. melilutra models exhibit a six-fold increase in stiffness from expected stiffness-volume relationships calculated from extant species models. Unlike stiffness, mechanical efficiency of biting is conserved among living otters and in S. melilutra. These findings indicate that although similar to living bunodont otters in morphology and biting efficiency, jaw strength in S. melilutra far surpasses molluscivores such as sea otters and Cape clawless otters, even after accounting for size. Therefore, Siamogale represents a feeding ecomorphology with no living analog, and its giant size and high mandibular strength confer shell-crushing capability matched only by other extinct molluscivores such as the marine bear Kolponomos.

Evolutionary shifts in extant mustelid (Mustelidae: Carnivora) cranial shape, body size and body shape coincide with the Mid-Miocene Climate Transition

“…However, a caveat to this study is the absence of paleontological data. Extinct mustelids were ecomorphologically diverse, with over 400 described species [41][42][43][44]. Unfortunately, the phylogenetic framework and morphological data needed to incorporate these extinct taxa are unavailable.…”

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

“…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.…”

“…This process is very sensitive and dependent on the material properties such as bone density and mineralization. Subsequently, the virtual model of the object is generated and can be subject to different evolutionary studies using 3D geometric morphometrics (GMM) for ecomorphology (Drake, 2011), finite element analysis for biomechanics (Racicot, 2017;Tseng et al, 2017), or computational fluid dynamics to decipher the behavior of extinct animals in fluid environments (e.g., Rahman, 2017). In addition, such models can be printed out using rapid prototyping to have a physical replica of the object under study and therefore improving the anatomical understanding and opening the possibility of using these models for teaching or public engagement.…”

Why ruminating ungulates chew sloppily: Biomechanics discern a phylogenetic pattern

“…The relationship between bite force, size and shape of the mandible in relation to ingesta has been studied previously in several mammalian clades including Artiodactyla [5–7], Chiroptera [8–12], Primates [13–15] and Carnivora [16–19]. Due to the close interaction between the mammalian feeding mechanism and diet, the biomechanical study of extant species can illuminate ecomorphological adaptations to provide accurate predictions of extant species and potentially acquire valuable tools for the reconstruction of oral behaviour in extinct taxa [20–22].…”