First tree-climbing vertebrate fossil discovered

Suminia getmanovi

From the Ottawa Citizen in Canada:

Canadian expert unearths tree-climbing pioneer

Fleet-fingered species had early opposable thumb

By Randy Boswell, Canwest News Service

August 3, 2009

A Canadian scientist and his U.S. colleague have discovered fossil evidence of two key moments in the evolution of higher-order animals, including humans: The emergence of both an “opposable thumb” and a “tree-climbing lifestyle” in a mammal-like, vertebrate species about 260 million years ago.

University of Toronto paleontologist Robert Reisz and his former student Jorg Frobisch, now with Chicago’s Field Museum, have published a study documenting the grasping abilities and tree-dwelling habits of suminia gemanovi [sic; Suminia getmanovi]– a long-tailed, lizard-like creature that was nevertheless more closely related to our own mammalian ancestors than to any reptile.

Part of a dead-end family of proto-mammals that disappeared before the dinosaur age, suminia shared a distinctive skull structure with mammals that distinguished it from lizards and birds.

Reisz was a key player in its discovery in central Russia in 1990, then co-published a breakthrough study in 2001 with U of T student Natalia Rybczynski, now a paleontologist with the Canadian Museum of Nature in Ottawa.

The 2001 paper revealed the half-metre-long Suminia to be the oldest-known land vertebrate able to grind vegetation with its teeth rather than just swallowing leaves whole.

The chewing adaptation would become a major evolutionary step for mammals.

But the latest study shows suminia pioneered two other key innovations for land animals that would also prove crucial — much, much later — for our own primate ancestors: a dexterity-aiding inner digit on its hands, and a knack for moving about in trees to escape predators, find food and take shelter.

“It was a new niche for vertebrates,” Frobisch said in a summary of the study. “There was food … and they avoided predators on the ground.”

The findings were made possible by the discovery of “several excellent skulls and more than a dozen exceptionally well-preserved, complete skeletons from a single large block of red mudstone” in Russia’s Kirov region.

Frobisch said analysis of suminia’s hand “shows a divergent thumb-like finger, which is indeed the earliest record of this feature in any vertebrate.”

The squeezing ability made possible by the feature would have helped the animal manoeuvre in trees and bushes.

With its “long limbs, very large hands and feet and particularly long fingers,” Frobisch said, “as well as a long tail that was likely grasping,” the evidence suggests the “tree-climbing lifestyle of the animal, again, making it the first known vertebrate to explore this habitat.”

See also here.

1 thought on “First tree-climbing vertebrate fossil discovered

  1. Pingback: Trees in history and religions | Dear Kitty. Some blog

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