ALLOMETRIC CHANGE IN THE LIMBS OFTHE PLIOCENE GOAT-LIKE CAMEL CAPRICAMELUS GETTYI (ARTIODACTYLA: CAMELIDAE)

The goat-like miolabine camelid Capricamelus gettyi, described in 2005 by Whistler and Webb from the Pliocene beds of Tecopa Lake, California, is remarkable in how short and stumpy its limbs were, especially the more distal elements, with limb proportions much like that of a mountain goat. How did its limbs scale as they got shorter and stumpier? We remeasured all the limb elements from the original sample of C. gettyi, and compared them to the limbs of its sister-taxon, the middle Miocene miolabine camel Paramiolabis tenuis, to see if there were any allometric size changes as they shrank in size and developed stumpy distal limb elements. The more proximal limb elements, such as the humerus, femur, and tibia, showed some negative allometry and increased robustness compared to Paramiolabis tenuis, with an allometric slope of about 0.8. But the metapodials are extremely short and thick compared to Paramiolabis tenuis, with an allometric slope of 0.2. This extreme allometric shape change results from C. gettyi evolving from a more “normal” camel with the typical long slender limbs. Such extreme allometric shortening is comparable to that of the extinct goat Myotragus balaericus of Mallorca, which also has extremely short broad metapodials, and evolved from goats with relatively longer distal limb elements.