Muscle Functional Morphology in Paleobiology: The Past, Present, and Future of “Paleomyology”

Abstract

Our knowledge of muscle anatomy and physiology in vertebrates has increased dramatically over the last two-hundred years. Today, much is understood about how muscles contract and about the functional meaning of muscular variation at multiple scales. Progress in muscle anatomy has profited from the availability of broad comparative samples, advances in microscopy have permitted comparisons at increasingly finer scales, and progress in muscle physiology has profited from many carefully designed and executed experiments. Several avenues of future work are promising. In particular, muscle ontogeny (growth and development) is poorly understood for many vertebrate groups. We consider which types of advances in muscle functional morphology are of use to paleobiologists. These are only a modest subset for muscle anatomy and a very small subset for muscle physiology. The relationship between muscle and bone - spatially and mechanically-is critical to any future advances in "paleomyology". Anat Rec, 301:538-555, 2018. © 2018 Wiley Periodicals, Inc.

“Keep your feet on the ground”: Simulated range of motion and hind foot posture of the Middle Jurassic sauropod Rhoetosaurus brownei and its implications for sauropod biology

“…However for sauropods, extant bracketing relatives (i.e., birds and crocodiles) are morphofunctionally very dissimilar and therefore may not represent appropriate correlates for soft tissue inferences. Instead, sauropods have been regularly compared to elephants in functional studies (e.g., Christiansen, ; Henderson, ); these examples are “level III inferences” of the Extant Phylogenetic Bracket, which use correlates beyond an immediate phylogenetic bracket (see Perry & Prufrock, ; Witmer, ).…”

Sciuromorphy outside rodents reveals an ecomorphological convergence between squirrels and extinct South American ungulates

“…Beyond that a soft-tissue reconstruction is always an inferential issue, muscular scars are direct evidences of the presence of muscles, and, in some cases, the development of the latter can be estimated reliably from the former 75,76 . In this context, we want to highlight the confidence of our proposal.…”

“…Firstly, a trait-to-trait qualitative analysis of studied specimen in a comparative framework of diverse living species allowed us establishing well-supported potential correspondences (homology hypotheses) between each muscle scars (i.e., direct evidence) and the most probable muscle attached to them (a first level of inference; see refs. 75,76 ). The second step was to check the correspondence or, at least, the absence of marked contradictions, in the development of the origin and insertion scars.…”

“…The second step was to check the correspondence or, at least, the absence of marked contradictions, in the development of the origin and insertion scars. Although it does not always occur, there exist usually a correlation between the development of muscles, and that of their origin and insertion scars 76 , and this can be in turn tested in extant models. If more than one group of homology hypotheses is being considered, the one that fits best in this sense should be chosen.…”

Morphological and biomechanical predictions of cranial kinesis in reptile evolution

“…We modeled jaw muscles as contracting synchronously at maximal force even though it was likely that, as has been shown in other diapsids, there is variation in the firing sequence and magnitude of cranial musculature (Busbey, 1989;Nuijens et al, 1997;van der Meij and Bout, 2008;Vinyard et al, 2008, Perry andPrufrock, 2018). Protractor and adductor muscles show variation in activation pattern during the feeding cycle, and the loads these muscles impart appear to help stabilize the cranial joints (Cundall, 1983;Holliday and Witmer, 2008).…”