Credit: THE ROYAL SOCIETY

Proc. R. Soc. B doi:10.1098/rspb.2009.0911 (2009)

Vertebrates have been out on a limb for longer than previously thought, say Jörg Fröbisch at the Field Museum in Chicago, Illinois, and Robert Reisz of the University of Toronto at Mississauga in Canada.

Their preliminary description of the anatomy of Suminia getmanovi, a 260-million-year-old distant relative of mammals, concludes that the species represents the oldest evidence of a tree-dwelling vertebrate.

Comparison of the features of S. getmanovi fossils with those of modern reptiles and mammals reveals numerous features indicative of a life spent in trees. These include elongated limbs, a long and perhaps prehensile tail, and digits seemingly adapted for grasping and climbing, possibly with opposable thumbs.