Only one small specimen of
Callistiopterus clappi has ever been found.
![Callistiopterus clappi Callistiopterus clappi](../mig-img/mig_callistiopterus_p.jpg)
(76 kb) The 7.5-centimetre fossil is kept among the collections in the Museum of Comparative Zoology at Harvard University. Assigning this specimen to a precise group has proven quite difficult.
Callistiopterus has the fusiform body of an osteolepiform (that is, a body tapered at both ends), but a heterocercal tail like those of porolepiforms. Its skull is poorly preserved and its paired pectoral and pelvic fins are missing due to the way the rock broke. Moreover, its small size suggests it was a young animal, and the proportions of the adult animal may be quite different.
Callistiopterus is tentatively classified as an osteolepiform, but it could also be a porolepiform, or even an actinistian. Such big names for such a small fish!