A.simus (yuk) vs. A. angustidens vs. U.m.tyrannus Jan 8, 2011 18:20:56 GMT -9
Post by grrraaahhh on Jan 8, 2011 18:20:56 GMT -9
What a BEAST!!!
The Largest Known Bear, Arctotherium angustidens, from the Early Pleistocene Pampean Region of Argentina: With a Discussion of Size and Diet Trends in Bears
The South American giant short-faced bear (Arctotherium angustidens Gervais and Ameghino, 1880) is one of five described Arctotherium species endemic to South America and it is known for being the earliest, largest, and most carnivorous member of the genus. Here we report an extraordinarily large A. angustidens individual exhumed from Ensenadan sediments (early to middle Pleistocene) at Buenos Aires Province, Argentina. Based on overall size, degree of epiphyseal fusion, and pathologies, this bear was an old-aged male that sustained serious injuries during life. Body mass of the bear is estimated and compared to other ursid species based on a series of allometric equations. To our knowledge, this specimen now represents the largest bear ever recorded. In light of this discovery, we discuss the evolution of body size in Arctotherium (from large-to-small) and compare this to bears that exhibited different evolutionary trajectories. We suggest that the larger size and more carnivorous nature of A. angustidens, compared to later members of the genus, may reflect the relative lack of other large carnivores and abundance of herbivores in South America just after the Great American Biotic Interchange.
Ulna comparison between A. angustidens vs. U.m.tyrannus
Ursus maritimus tyrannus (B.M. 24361 Kew Bridge specimen)
L, total length of the ulna.
PD, greatest proximal diameter, measured anteroposteriorly from the tip of the coronoid process to Margo dorsalis.
SD, inner diameter of the semilunar notch, measured vertically.
BS, minimum transverse breadth of shaft. This is in the distal portion of the shaft, at some distance above the capitulum. The extreme constriction lies close to the capitulum in the Brown Bear and the spelaeids, but higher on the shaft in the Polar Bears, including the Kew specimen.
1 L, length; PD, maximum proximal diameter; SD, inner diameter of semilunar notch; BS, minimum shaft diameter.
Ursus maritimus tyrannus
Ursus maritimus tyrannus (Plate # 2 Ulnae)
Kurten, Bjorn 1964, The evolution of the Polar Bear Ursus maritimus Phipps.
Greatest length: Right; Left, 570.
Greatest width of olecranon processWidth from posterior border to tip of coronoid process: Right, 108; Left, 109.
Least distance from sigmoid notch to posterior
border: Right, 66; Left, 70.
Greatest diameter of distal epiphyses: Right, 63; Left, 62.5.