Meeting Abstract

P3.132  Monday, Jan. 6 15:30  The functional anatomy of the hindlimb of the ringtail (Bassariscus astutus) LIU, M.C.*; LUCAS, L.; ALLEN, D.; FISHER, R.E.; Arizona State University; The University of Arizona College of Medicine Phoenix; Arizona State University; The University of Arizona College of Medicine Phoenix mcliu2@asu.edu

The ringtail (Bassariscus astutus), a member of the Procyonidae, is capable of 180 degrees of hindlimb reversal during headfirst descent on a vertical substrate. The goal of this study was to determine the presence or absence of myological adaptations related to hindlimb reversal in the ringtail. Data for B. astutus are presented, including muscle weights, moment arms, and muscle maps ascertained from the dissection of four hindlimbs. Data from the current study were compared to published accounts of close relatives of the ringtail, as well as other species capable of hindlimb reversal, including procyonids (raccoon, coati, kinkajou, olingo), viverrids (palm civet, mongoose), a mustelid (marten), the tree squirrel, common tree shrew, and Virginia opossum. The ringtail exhibits extensive fusion between m. gluteus superficialis and its bordering muscles, two heads of mm. semitendinosus and semimembranosus, well-developed muscle bellies of mm. flexor digitorum lateralis and flexor digitorum medialis, and a robust m. flexor digitorum brevis. These traits are present in the majority of species capable of hindlimb reversal. These characteristics, along with available muscle weight and moment arm data, indicate an emphasis on hip extension, abduction, and lateral rotation, as well as powerful plantarflexion of the ankle and greater digit flexion compared to extension. The aforementioned ranges of motion are integral to hindlimb reversal during headfirst descent; thus, the data support the presence of myological adaptations for hindlimb reversal in the ringtail.