The supraotic bone in neopterygian fishes (Osteichthyes, Actinoptergii). American Museum novitates ; no. 3267
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Date
1999
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New York, NY : American Museum of Natural History
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Abstract
"The supraotic is a chondral bone that has a relatively restricted phylogenetic occurrence, since it occurs only in some extinct neopterygian fishes. Like the supraoccipital in teleosts, coelacanths, and tetrapods, the supraotic is positioned at the dorsal midline in the posterior part of the braincase, but the supraotic and supraoccipital have been distinguished on topographic grounds. The supraotic is situated anterior to the occipital segment, presumably within the synotic tectum. The supraoccipital may be confined to the occipital segment (as in the Jurassic stem teleost Pholidophoroides), or it can extend into the otic region following fusion of the synotic tectum and occipital arch (as in many modern teleosts and tetrapods). In some Recent teleosts (e.g., Oryzias, Danio, Betta) the supraoccipital may form entirely within the synotic tectum, a presumably secondary arrangement. The topographic distinction between the supraotic and supraoccipital is therefore obscured secondarily in Recent teleosts and is more evident in fossils. In Amia and extinct stem teleosts such as Pholidophoroides, the dorsal part of the cranial fissure persists during development, separating the occipital pila from the synotic tectum even in the adult. Such persistence of the cranial fissure dorsally in extinct halecomorphs may have prohibited the supraotic from extending onto the occipital arch. The supraotic bone is present in the early Cretaceous amiid Calamopleurus cylindricus, but it is absent in the Recent Amia calva, suggesting a previously unsuspected bone loss in amiid evolution. In Calamopleurus cylindricus and Ionoscopus cyprinoides the supraotic encloses the dorsal parts of the anterior and posterior semicircular canals. In I. cyprinoides the supraotic also forms the mesial wall of the lateral cranial canal, which in pholidophorid teleosts lies within the pterotic. The supraotic may be exposed in the skull roof at the posterior midline (as in Ionoscopus, Oshunia), or it may be located entirely beneath the parietals (as in Calamopleurus). A peculiar median chondral bone in the roof of the otic region in the pycnodontiform Neoproscinetes penalvai is probably also a supraotic, although its morphology is highly specialized"--P. [1]-2.
Description
52 p. : ill. ; 26 cm.
Includes bibliographical references (p. 48-52).
Includes bibliographical references (p. 48-52).
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