Ageleodus pectinatus (early shark)
Hundreds of small fossil teeth belonging to Ageleodus pectinatus were recovered from shallow channel deposits referred by the scientists at Red Hill as microfossil lenses. These lenses contain well-sorted coarse sand and numerous disarticulated smaller vertebrate fossils. These microfossil lenses were probably created when sandy sediments of the main channel were dumped near the riverbank during flooding. Ageleodus fossils were found exclusively in these microfossil lenses.
Like the majority of fossil shark species, Ageleodus pectinatus is known only from its teeth. It was first described by Louis Agassiz in 1838 from teeth collected from an early Carboniferous marine deposit in Scotland. Additional specimens have since been collected from other Carboniferous localities in Europe, Australia and North America. The record of Ageleodus from Red Hill represents the earliest occurrence (Late Devonian) of this genus anywhere. It's also the largest collection of Ageleodus teeth from any single locality.
The large number of teeth collected from Red Hill allowed a comprehensive study of variation within this species. The considerable differences among the 382 specimens illustrates the challenge facing the scientists who study these fossils. Crown lengths ranged from 0.8-8.7 mm while cusp numbers ranged from 3 to 33. However, the vast majority of teeth had between 5 and 10 cusps and were 2-5 mm long.
Examination of Ageleodus teeth under an electron microscope indicated that these teeth exhibited relatively little wear. Most modern sharks also exhibit little wear in their discarded teeth. If modern sharks are any guide, the teeth may have been shed and replaced within a matter of weeks. In contrast, most Paleozoic sharks exhibit considerably more tooth wear, and are beleived to have had much slower tooth replacement.
- Scientific Papers:
- Downs, J. P. and E. B. Daeschler. 2001. "Variation within a large sample of Ageleodus pectinatus teeth (Chondrichthyes) from the Late Devonian of Pennsylvania, U.S.A." J. Vert. Paleo. 21(4): 811-814.