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Re: Oldest Footprints Identified



The other way around: these footprints are the oldest ones that are currently identifiable to species level (or genus -- *Orobates* is monotypic). That's interesting enough, but the oldest known vertebrate footprints are Devonian. (Trilobite footprints go all the way down to the base of the Cambrian, apparently.)

The work could also lead to a rethinking of how some of the first land
creatures stood and walked. Mammals tend to have legs and limbs that drop
vertically from the pelvis to the ground, while those of reptiles tend to
extend away from the body horizontally before turning back downward. The
new reptiles had a "mammalian" arrangement for their limbs.

"We know from the trackways that these animals had their feet planted
almost under their body," Berman said, "whereas in textbooks, they give
them a sprawling gait as if the limbs are extended out from the body
considerably. This just isn't true. You look at the trackway and you see
that the footprints are very close to the midline of the body."

Diadectids had vertical limbs? Fascinating! Entirely unexpected. They still aren't "reptiles", however, no matter how those are defined; they aren't amniotes. They are hidden in Diadectomorpha at http://tolweb.org/Terrestrial_Vertebrates/14952.