Fishapod fossil had pointed forearm, simple hinge elbow — SkimNews
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- Thomas Stewart at Penn State and colleagues CT-scanned a 350-million-year-old fishapod fossil discovered on Ellesmere Island — an isolated fin that didn't match any of the 16 known fishapods they compared it against.
- The specimen's radius bone was long and triangular, ending in a sharp point at the wrist, and its elbow formed a simple hinge bending in a single plane — far more restrictive than the twisting, rotating elbows of other fishapods like Tiktaalik.
- The fossil's intermedium bone, a suspected wrist precursor, was relatively longer than in Tiktaalik and its close relatives, adding to a growing catalog of unusual fin-limb geometries from the water-to-land transition.
- Stewart framed the discovery as evidence of 'trial and error' in early arm formation, noting his team in 2022 described Qikiqtania wakei — a fishapod that evolved weight-supporting fins before reverting to full-time swimming.
- Julia Molnar at NYIT suggested the animal may have used its fins to 'walk' in shallow water or push through vegetation to escape predators, while Brian Swartz at UC Berkeley cautioned the variation suited current environments — not some future life on land.
- Stewart's framing: when animals explore new movements they 'might be kind of awkward' but 'good enough. It's a matter of sufficiency, not optimality.'
Why it matters: For paleontologists, this fossil chips away at the tidy Tiktaalik-to-tetrapod narrative — showing the water-to-land transition wasn't a straight line but a proliferation of experimental appendage forms, some of them clunkier than others. The finding reinforces Stewart's principle that early evolution ran on 'sufficiency, not optimality,' meaning awkward intermediates weren't failed drafts on the way to us.
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