Giants and Bizarres: Body Size of Some Southern South American Cretaceous Dinosaurs

Abstract

Body masses of some South American dinosaurs are estimated. The sauropod Argentinosaurus huinculensis reached 73 tonnes, and therefore, is the largest of all land animals whose mass has been rigorously obtained. Another sauropod, Antarctosaurus giganteus, was the second largest, at nearly 69 tonnes, while Antarctosaurus wichmannianus reached 34 tonnes. A third sauropod, the bizarre-looking Amargasaurus cazaui, was much smaller, with a body mass of only 2.5 tonnes. Among theropods, the body mass of the strangely looking, horned Carnotaurus sastrei, was volumetrically estimated at 1.5 tonnes, while allometric equations on limb measurements yielded overestimations. Moreover, the holotype specimen of Giganotosaurus carolinii (MUCPv-CH-1) was about as large as the average-sized Tyrannosaurus rex, and only marginally smaller than "Sue", the largest specimen. However, a new dentary of Giganotosaurus (MUCPv-95) is 8% longer than that of the holotype. Assuming geometric similarity, that individual must have had a body mass above 8 tonnes and hence must have been the largest theropod ever found.

Small body size and extreme cortical bone remodeling indicate phyletic dwarfism inMagyarosaurus dacus(Sauropoda: Titanosauria)

“…The nanoid status of M. dacus is unique among titanosaurs, all of which have body masses an order of magnitude greater (1,60). The only other island nanoid sauropod known is Europasaurus from the Upper Jurassic of Germany (8).…”

“…bone histology | Sauropoda | secondary osteon | nanism | island fauna S auropod dinosaurs were the largest animals that ever roamed the surface of the Earth (1,2). Gigantic size was acquired early in the evolutionary history of the group, in the Late Triassic (3).…”

A new sauropod dinosaur from the Early Cretaceous of Tunisia with extreme avian-like pneumatization

“…Although a precise quantification of total body size of ONM DT 1-36 is not possible, comparison between its sacrum and the sacra of more complete diplodocoid specimens suggests an individual at least 14 m long 27 (Table 1), thus more than 150% the adult length of Nigersaurus 13 . The holotype of T. hannibalis is interpreted to represent an ontogenetically mature individual based on the combination of large size, co-ossification of the sacrum, obliterated neurocentral suture in caudal vertebrae (Fig.…”

A new multi-faceted framework for deciphering diplodocid ontogeny

“…Body mass estimates were calculated for fiftyfour diplodocid femora (Appendix 4) following the allometry-based body mass formula of Mazzetta et al (2004). Additional mass estimation methods that incorporate multiple elements (such as humeral and femoral circumference; i.e., Campione and Evans, 2012) and histologic data (Sander and Tückmantel, 2003;Lehman and Woodward, 2008;Griebeler et al, 2013) should produce more accurate estimates because these methods incorporate more variables regarding the individual and its life history.…”