Morphology and Evolution of Sesamoid Elements in Bats (Mammalia: Chiroptera)

AMADOR, LUCILA INÉS; GIANNINI, NORBERTO PEDRO; SIMMONS, NANCY B.; ABDALA, VIRGINIA

AMERICAN MUSEUM NOVITATES

AMER MUSEUM NATURAL HISTORY

Año: 2018 vol. 3905 p. 1 - 40

0003-0082

Sesamoids are skeletal elements found within a tendon or ligament as it passes around ajoint or bony prominence. Here we review the distribution of sesamoids in bats, the only mammalscapable of powered flight. Our survey included bat species representing most extant familiesas well as two key Eocene fossil bats in which sesamoids are exquisitely preserved,Onychonycteris finneyi and Icaronycteris index. We identified 46 separate sesamoid elements (orsets of elements) from dissections of selected bat taxa, with no more than 23 of these presentin any given species. Among the sesamoids identified in our survey, 12 have not previously beendescribed in bats. We also identified seven sesamoids previously described in the literature thatare not present in our sample of species. No sesamoids were found to be exclusive to the fossiltaxa in our study; all the sesamoids observed in Onychonycteris and Icaronycteris have apparenthomologs among extant species. We mapped the presence/absence of the 46 sesamoids onto abat phylogeny. Based on these optimizations, we discuss homology issues and evolutionaryhistory of some of the most taxonomically widespread sesamoids. Functional inferences regardingsome sesamoids can be made based on what is known about bat musculoskeletal morphology,although further biomechanical studies are required to test the hypotheses proposed here.Sesamoids will continue to be a source of interesting insights about the evolution of bats andtheir unique locomotor abilities.