ピクノドン科魚類：形態変異，生態・形態学的適応ならびに進化史に関する新解釈

抄録

Some examples of morphologic variation of body and fins morphology in Pycnodontiformes are shown; not all are butterfly fish-like, as the common place assumes. Pycnodonts are characterized by a heterodontous dentition; teeth on the vomer and the prearticulars are molariform, yet of diverse shapes, whereas teeth on the premaxilla and the dentary do exhibit even more diverse morphologies. This morphologic variation is also analyzed, and the inaccuracy of another common place, the "crushing" or "durophagous" dentition of the pycnodonts, is explained: these terms refer to function, not to form.

The ecomorphologic evaluation of both sources of morphologic variation, body and dentition, indicate that pycnodonts may have been adapted to a large variety of potential diets and environments. The environment of pycnodont fishes is often believed to have been reefal, but this is not necessarily the case, since their adaptations are not exclusively functional in reefs or even in marine environments only. Examples of freshwater pycnodonts are mentioned, showing that these fishes are potentially misleading palaeoenvironmental indicators: their mere presence in any given locality is not an unambiguous indication of its palaeoenvironment.

The ecomorphologic plasticity of pycnodonts was a key factor for their success as a group. This, together with a re-evaluation of their fossil record, leads to a new interpretation of the evolutionary history of the Pycnodontiformes.