The extinct, giant giraffid Sivatherium giganteum : skeletal reconstruction and body mass estimation

Abstract

Sivatherium giganteum is an extinct giraffid from the Plio–Pleistocene boundary of the Himalayan foothills. To date, there has been no rigorous skeletal reconstruction of this unusual mammal. Historical and contemporary accounts anecdotally state that Sivatherium rivalled the African elephant in terms of its body mass, but this statement has never been tested. Here, we present a three-dimensional composite skeletal reconstruction and calculate a representative body mass estimate for this species using a volumetric method. We find that the estimated adult body mass of 1246 kg (857—1812 kg range) does not approach that of an African elephant, but confirms that Sivatherium was certainly a large giraffid, and may have been the largest ruminant mammal that has ever existed. We contrast this volumetric estimate with a bivariate scaling estimate derived from Sivatherium's humeral circumference and find that there is a discrepancy between the two. The difference implies that the humeral circumference of Sivatherium is greater than expected for an animal of this size, and we speculate this may be linked to a cranial shift in centre of mass.

First comprehensive morphological analysis on the metapodials of Giraffidae

“…This supports that giraffids distribute more body weight on the forelimb instead of the hindlimb, contrary to the typical condition seen in artiodactyls (Alcalde, 2012). The highest metacarpal RI of our analysis, Sivatherium giganteum, could be correlated with the presence of massive ossicones (Falconer and Cautley, 1836;Basu et al, 2016), which would place a higher weight on the anterior part of the body. The same occurs with the robust Bramatherium megacephalum (Lewis, 1939), which also bears huge ossicones and Birgerbohlinia schaubi which bears 50 cm long posterior ossicones (Montoya and Morales, 1991).…”

Reconstruction of the musculoskeletal system in an extinct lion

“…15 -16% (Pitts and Bullard, 1968)). Convex hull models have been used recently to reconstruct body segmental shapes and estimate body masses for skeletons with no preserved soft tissues (e.g., Sellers et al, 2012;Basu et al, 2016;Bates et al, 2016;Brassey et al, 2016). The convex hull model for the entire skeleton of P. atrox produced a volume of 0.185 m 3 (Figure 4).…”

“…This was done by using the "convex hull" filter within Meshlab for the skeletal elements from each of the body segments (e.g., Basu et al, 2016). Body mass estimates were calculated from the sum of all masses from the complete set of convex hulls using a 4 range of densities from 893.36 kg m −3 multiplied by 1.091 to 1.322 (i.e., 974.7 kg m −3 to 1181 kg m −3 -a correction factor due to the underestimation of limb masses) (Sellers et al, 2012).…”

“…However, it becomes more difficult to estimate muscle boundaries when there is no outer limit on the size of the muscles. Using convex hulls (e.g., Basu et al, 2016) or non-uniform rational bsplines (NURBs) (e.g., Bates et al, 2009) it is possible to estimate muscle volumes, but doing so incurs additional uncertainties from assumptions of the volume reconstruction methods. Thus advances in the area of soft tissue reconstruction, especially quantitative methods that can also address uncertainties, are important.…”

Body-Mass Estimation in Paleontology: A Review of Volumetric Techniques

“…The mass of the giant titanosaurian sauropod Dreadnoughtus schrani Lacovara et al, 2014 has been revised from an initial 59 tons (Lacovara et al, 2014) down to 28-38 tons (Bates et al, 2015) on the basis of convex hulling. Likewise, the predicted mass of the giant giraffid Sivatherium giganteum Falconer & Cautley, 1836 has also been reduced from 3000 kg to 1246 kg using this technique (Basu et al, 2016). In both cases, a considerable portion of the skeleton was missing and required reconstruction, either through substitution of equivalent elements from related taxa and/or virtual manipulation of the convex hulls.…”