Media Releases

How Does This Grab You? New U Of T Mississauga Study Identifies First Ancestor With A ‘Grasping Hand’

July 30, 2009

TORONTO, ON — Elon­gat­ed fin­gers, an oppos­able “thumb”, and a grasp­ing tail–a new fos­sil study by researchers at the Uni­ver­si­ty of Toron­to Mis­sis­sauga sug­gests that a small plant-eat­ing mam­mal rel­a­tive is the old­est known tree-climb­ing ver­te­brate.

The tree-climb­ing lifestyle of Sum­inia get­manovi, a Pale­o­zoic ani­mal that lived 260 mil­lion years ago, is par­tic­u­lar­ly impor­tant because it gave this small her­bi­vore the first access to new food resources high off the ground, and also pro­vid­ed pro­tec­tion from ground-dwelling preda­tors. The evi­dence for this lifestyle is based on sev­er­al skulls and more than a dozen com­plete skele­tons from cen­tral Rus­sia, as well as from copro­lites (fos­silized feces) that were found on the same sed­i­ments as the skele­ton. The find­ings appear online in the Pro­ceed­ings of the Roy­al Soci­ety B.

“Inde­pen­dent­ly, this ani­mal appears to have acquired this evo­lu­tion­ary inno­va­tion of a grasp­ing hand,” says Pro­fes­sor Robert Reisz, chair of the Depart­ment of Biol­o­gy at the Uni­ver­si­ty of Toron­to Mis­sis­sauga. “That would have allowed it to climb trees very effi­cient­ly and to grasp things. It would have allowed the ani­mal to bring food to its mouth.” Reisz, the senior author of the paper, notes that mod­ern ani­mals like chameleons and fly­ing lemurs have sim­i­lar fore­leg struc­ture.

The study also pro­vides the first evi­dence of “resource par­ti­tion­ing” — with small­er arbo­re­al ani­mals tak­ing advan­tage of food and safe­ty from preda­tors in trees while larg­er her­bi­vores remained on the ground. This was a change from a large num­bers of ter­res­tri­al plant-eaters sup­port­ing a few top preda­tors, and even ear­li­er ter­res­tri­al ver­te­brate com­mu­ni­ties com­posed of var­i­ous sized preda­tors and rel­a­tive­ly few her­bi­vores.

The first author, Joerg Froe­bisch, is cur­rent­ly a post­doc­tor­al fel­low at the Field Muse­um in Chica­go. Fund­ing for the study came from the Gov­ern­ment of Cana­da, the Ger­man Research Foun­da­tion, the Ger­man Aca­d­e­m­ic Exchange Ser­vice, the Uni­ver­si­ty of Toron­to, the Nat­ur­al Sci­ences and Engi­neer­ing Research Coun­cil of Cana­da and the Nation­al Geo­graph­ic Soci­ety.

*Images avail­able upon request.


For more infor­ma­tion, please con­tact:
Robert Reisz
Depart­ment of Biol­o­gy
Uni­ver­si­ty of Toron­to Mis­sis­sauga

Nicolle Wahl
Com­mu­ni­ca­tions and Mar­ket­ing
Uni­ver­si­ty of Toron­to Mis­sis­sauga