AN ASSOCIATED DENTITION OF AGASSIZODUS (CHONDRICHTHYES, EUGENEODONTIFORMES) FROM THE UPPER CARBONIFEROUS OF MISSOURI
DUFFIN, Christopher, Surrey, England; WARD, David J., Orpington, United Kingdom; LAUER, Bruce H., Wheaton, IL, United States of America; LAUER, Rene L., Wheaton, IL, United States of America
The Lauer Foundation for Paleontology, Science, and Education has recently come into ... [Show full abstract] possession of an associated, but largely disarticulated, dentition of the edestoid eugeneodontiform fish, Agassizodus. The dentition (LF 3199), scattered over several blocks, comes from the Pennsylvanian (Late Carboniferous) Hushpuckney Shale Member (Swope Limestone Formation, Bronson Sub-Group, Kansas City Group) of Kansas City, Missouri. The genus Agassizodus was originally raised by St John and Worthen in 1875 in honour of Jean Louis Rodolphe Agassiz (1807–1873), the famous Swiss palaeoichthyologist who had emigrated to America in 1846.
An articulated revolver of four robust symmetrical symphyseal teeth, each with a high upright central cusp, is supplemented by two disarticulated specimens from the same tooth family. Prominent labial nodes, low down on the crown, are buttressed with root tissue and are a distinctive characteristic of the teeth. The post-symphyseal components of the dentition show linear gradient monognathic heterodonty, with tooth size increasing from small, stud-like parasymphyseals, through low-crowned, elongate and increasingly robust laterals, to smaller posterolaterals. The disarticulated nature of the dentition permits detailed description of the 3-D morphologies of most tooth positions which will prove useful in defining the heterodonty more closely and comparing the dentition with those of other edestoids.
Much confusion currently exists concerning the nomenclatural validity of the genus. The Belgian palaeontologist and chemist from Louvain, Laurent-Guillaume de Koninck (1809– 1887), erected Campodus agassizianus in 1844, based upon isolated teeth from the Late Carboniferous of Liège. Further material was described by Maximin Marie Joseph Lohest (1857–1926), Professor of Geology at the University of Liège, in 1885. During the intervening years Lt-Col Hennadius Romanowsky (dates unknown) of St Petersburg had defined the genus Lophodus, with several species, for teeth which he noted resembled those of Helodus, and which were collected from the Carboniferous of Tula in Central Russia. Romanowsky’s generic name was used by Newberry and Worthen in 1870 to define L. variabilis, a species which was then adopted by St John and Worthen as the type species of Agassizodus. It is hoped that further work on LF3199 will help to unravel some of this taxonomic confusion.