Bats fly, whales swim, gibbons swing from tree to tree, horses gallop, and humans swipe on their phones — the different habitats and lifestyles of mammals rely on our unique forelimbs. No other group of vertebrate animals has evolved so many different kinds of arms: in contrast, all birds have wings, and pretty much all lizards walk on all fours. Our forelimbs are a big part of what makes mammals special, and in a new study in the Proceedings of the National Academy of Sciences, scientists have discovered that our early relatives started evolving diverse forelimbs 270 million years ago — a good 30 million years before the earliest dinosaurs existed.
“Aside from fur, diverse forelimb shape is one of the most iconic characteristics of mammals,” says the paper’s lead author Jacqueline Lungmus, a research assistant at Chicago’s Field Museum and a doctoral candidate at the University of Chicago. “We were trying to understand where that comes from, if it’s a recent trait or if this has been something special about the group of animals that we belong to from the beginning.” …
Lungmus and Angielczyk found that a wide variety of different forelimb shapes evolved within the therapsids 270 million years ago. “The therapsids are the first synapsids to increase the variability of their forelimbs — this study dramatically pushes that trait back in time,” says Lungmus. Prior to this study, the earliest that paleontologists had been able to definitively trace back mammals’ diverse forelimbs was 160 million years ago. With Lungmus and Angielczyk’s work, that’s been pushed back by more than a hundred million years. Paper. (open access) – Jacqueline K. Lungmus, Kenneth D. Angielczyk. Antiquity of forelimb ecomorphological diversity in the mammalian stem lineage (Synapsida). Proceedings of the National Academy of Sciences, 2019; 201802543 DOI: 10.1073/pnas.1802543116 More.
So many good ideas seem to have got started quite early and been around nearly forever. One wonders if flexible forelimbs got started quickly too…
See also: “Super-Ancient Mobile Organisms” Push Mobile Life Back To 2.1 Billion Years Ago
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