Meeting Abstract

P2.114  Monday, Jan. 5  New Insights into the Mandibular Symphyses of Reptiles HOLLIDAY, Casey M; Marshall University hollidayc@marshall.edu

The morphology of the mandibular symphysis likely reflects the functional environment in which it resides and numerous analyses have focused on the correlation between symphyseal structure and masticatory behavior among mammals. However, few studies have investigated symphyseal evolutionary and functional morphology among reptiles. Whereas turtles, birds, and crocodilians have characteristically fused or interdigitated the symphysis, lepidosaurs maintain open symphyses. To further illustrate structure-function relationships of the joint, data on soft and bony tissues that comprise the symphysis were collected among a diverse sample of extant lizards including iguanians, geckos, skinks, and varanids using microCT scanning, followed by standard and polarized light microscopy of undecalcified serial histological sections. Among lizards, soft-biting taxa possessed mostly parallel-fibered, elastic connective tissues whereas hard-biting taxa possessed significantly more cartilaginous and mineralized tissues within the symphysis. Other species displayed connective tissue morphologies within this spectrum and histology suggests a three-dimensionally complex organization of tissues including a laminar organization of loose parallel-fibered tissues, cartilaginous domains and dense parallel and woven fibers. Some of these fibers attach directly to Meckels cartilage whereas most are embedded as extrinsic fibers within the bony symphysis. All species investigated rely on soft tissues, rather than bony interdigitations, to support the joint. These and other data provide the foundation to further explore the adaptive plasticity and in vivo function of the joint among extant taxa as well test hypotheses of the structures evolution among fossil taxa.