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CT Imaging of the Internal Anatomy of Sloth Claws
Author(s) -
Grass Andy
Publication year - 2019
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2019.33.1_supplement.614.2
Subject(s) - claw , sloth , manus , anatomy , biology , rosette (schizont appearance) , dorsum , paleontology , ecology , immunology
One of the most immediately noticeable peculiarities about sloths, among many, are their large, curved claws. Indeed, the name Megalonyx , a giant ground sloth from North America named by Thomas Jefferson, means “great claw.” Sloths have used their claws for a variety of purposes, including suspension from tree branches in modern sloths, hooking branches to pull food closer while eating, to gigantic burrows that have been attributed to some genera of ground sloths. Large claws may also have contributed to the evolution of the pedolateral foot orientation in some ground sloths, where the fifth metatarsal is the primary weight bearing bone, and the dorsal surface of the foot faces laterally. As such, a sloth's claws are and were integral to their existence. For this study sloth claws were scanned in a Micro CT at the American Museum of Natural History, and these scans were segmented to view their internal anatomy. Both manus and pes claws from both genera of modern sloths, Bradypus and Choloepus , were scanned, as well as manus and pes unguals from the ground sloths Megalonyx jeffersonii and Paramylodon harlani , including specimens from the Tarkio Valley M. jeffersonii from the University of Iowa. Two of the ground sloth claws were broken on the ends, which revealed holes on the distal surface. It was unclear if these holes were natural, or the result of taphonomy or tools. The CT scan revealed that these holes are in fact passages for blood vessels, and lead to discrete canals in the interior of the claw. These canals originate from external foramina on the lateral sides of the claws, which are next to very clear external vessel impressions. These two lateral canals come together to form one central canal, which then branches again more distally. Bradypus is considered to be basal to all other sloths, including the other modern sloth, Choloepus . Despite this phylogenetic distance, all of the sloths showed similar patterns of vascular canal branching. There tended to be more vessels on the volar side of the claws, perhaps to supply areas that are more used for touch and pressure sensation. It will be interesting to see if anteaters and armadillos, which also have large claws but use them for more strenuous digging activities than modern sloths, also show similar vasculature patterns and structure. This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .