Wednesday, May 18, 2011

Triassic Crocodile Cousin Walked


 picture from Google

First described over a century ago, Poposaurus is a “rauisuchian,” part of an extinct lineage of reptiles whose diverse array of members included the precursors of crocodiles and their closest relatives. Rauisuchians differed from crocodiles as we know them today in holding their limbs upright beneath their bodies rather than out to the side. This arrangement made them more efficient at walking and running on land, and, until recently, all rauisuchians were thought to have walked on all fours. The newly described Poposaurus was found in the Triassic Chinle Formation of southern Utah’s Grand Staircase-Escalante National Monument. The fossil included most of the postcranial skeleton from midway down the neck to the tip of the tail, stretching about 4.5 meters in all. According to the new research, the anatomy of the creature’s pelvis and hind limbs shows that Poposaurus walked upright, planting its feet close to the midline of its body. In fact, the hip anatomy would have made it impossible for Poposaurus to sprawl its limbs out to the side, like living crocodiles, although the exact way the rauisuchian’s feet touched the ground is unclear. Poposaurus may have stood on tiptoe, walked with the whole foot touching the ground, or it might have alternated between both foot postures depending on how fast it was moving.

 Article from http://news.sciencemag.org/sciencenow/2011/05/triassic-crocodile-cousin-walked.html?rss=1