Magazine article ROM Magazine

Overgrown Bone: A ROM Paleontologist Identifies the Fish with the Swollen Head

Magazine article ROM Magazine

Overgrown Bone: A ROM Paleontologist Identifies the Fish with the Swollen Head

Article excerpt

Q I found this object on a beach in Oman. I think it might be part of a fish skull. if it is, can you tell me what kind of fish it is from?--Mike Silver, Toronto

A You are indeed correct: it is part of a fish skull, but not just any ordinary fish skull. I knew the moment I saw the swollen and thickened bones that this skull has hyperostosis, which means "excessive thickening of bone." Several skulls in our comparative fish-bone collection display this same phenomenon.

Originally scientists interpreted these bone overgrowths as tumours, but we now know that they are a regular part of the growth process in some species. Exactly why some fish do this and others don't is still a mystery.

Within a species, the same bones are always hyperostotic. But across species, the patterns are different--so the overgrowth is species-specific. In many fish, part of the skull is affected, such as the supraoccipital of the spadefish. In others, such as in the crevalle jack, it's the ribs, vertebrae, or other skull bones that are involved.

Even though I knew this was a hyperostotic skull, I still had trouble identifying your particular fish species. ROM ichthyologists (fish specialists) pointed me to various books on the fishes of Oman and the Persian Gulf, but none had skeletal illustrations. I was pretty sure no similar skull would be in our comparative collection since we have few from that part of the world, but I checked them all just to be sure--and found no match. The thousands of whole preserved fish in the ichthyology collection were not likely to be any help either, because I needed to see their skeletons. …

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