Meeting Abstract

63.3  Tuesday, Jan. 6  Tooth Whorls in Chondrichthyes: The Edestoids, Helicoprion, and other Nightmarish Sharks of the Past LUND, R.*; GROGAN, E.D.; Carnegie Museum; Saint Joseph’s University rlund@sju.edu

Tooth arches or whorls of the Edestoid and Helicoprionid Chondrichthyes (Euchondrocephali) of the Upper Paleozoic are borne upon calcified cartilage and bear triangular serrated teeth like those of Carcharodon megalodon. Virtually no head or postcranial information accompanies these specimens. The sizes of these arches or whorls approach 1 meter in length or diameter. Past restorations have placed these on the snout, anterior to the dorsal or/and anal fins, and at the tip of the dorsal lobe of the tail before settling in the mouth. Most recently they have been theorized to be part of a pharyngeal apparatus. Data from new taxa shed broader light on the question of what and where these structures are found. Tooth whorls mounted on parasymphysial and symphysial cartilages are found in most basal Chondrichthyes and virtually all known Euchondrocephali (Holocephali); they are absent in Elasmobranchii. Tooth whorls are also found in basal chondrichthyan taxa that lack mandibular arch teeth. Analyses suggest they are under the control of separate developmental fields from that of mandibular arch teeth. Thus, even the anterior upper dental positions of the cochliodont Holocephali, which are also under control of separate developmental fields, are hypothesized to be parasymphysial elements fused to the neurocranium. While multiple upper and lower whorls or families are found in some Iniopterygians, the basic euchondrichthyan pattern of tooth whorls is for paired uppers and a median lower whorl. This is also the condition in the few known edestoids, including Edestus mirus. There is no evidence for large tooth whorls in any chondrichthyan pharynx. A two foot diameter Helicoprion symphysial tooth whorl translates into an approximately 50 foot long fish.