Fishapod fossil shows early elbows came in a variety of forms — SkimNews
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- Thomas Stewart at Pennsylvania State University and colleagues analyzed a single isolated fin fossil from Ellesmere Island and CT-scanned it, comparing its arm-like bones against 16 other known fishapods — the specimen matched none, indicating a distinct species.
- The radius bone in the new fossil was long, triangular, and came to a sharp point at the wrist end, with a narrow "bean-shaped" upper end rather than the rounded knob seen in other fishapods, suggesting an elbow that bent in a single plane without the twisting rotation possible in other species.
- The fossil's intermedium — a small bone scientists suspect evolved into part of the wrist — was relatively longer than in Tiktaalik and its close relatives, adding another anatomical wrinkle to the fishapod record.
- Stewart frames the discovery as part of a broader pattern: Qikiqtania wakei, which his team described in 2022, first evolved weight-supporting fins before reverting to full-time swimming, and dozens of finned tetrapodomorphs have now been found with surprisingly varied limb geometries.
- Julia Molnar at the New York Institute of Technology said the wide variation in radius shape likely represents "different approaches to the problems and opportunities of this changing world," while Brian Swartz at UC Berkeley cautioned that the unusual fins were adapted for the animal's own environment — not future life on land.
- Stewart suggested the awkward, restrictive elbow may have been "good enough" rather than optimal, using the phrase "sufficiency, not optimality" to describe early exploratory appendages that might have helped the animal push through vegetation or shallow-water "walk" past predators.
- The study was published in the Journal of Vertebrate Paleontology (DOI: 10.1080/02724634.2026.2708076).
Why it matters: With only a single isolated fin to examine, researchers still extracted enough anatomy from CT scans to confirm a previously unknown fishapod species whose hinge-only elbow could not rotate like Tiktaalik's — proof that even the iconic water-to-land transition was messier than textbook diagrams suggest, with multiple lineages independently experimenting with appendage shapes suited to their own shallow-water niches.
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