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ABSTRACT
A collection of over 550 elasmobranch teeth (Family Lonchidiidae) were obtained from fresh water fluvial deposits of the Middle–Upper Triassic (Ladinian–Carnian) Paramillo Formation, in northwestern Mendoza Province, Argentina. The new hybodontid species, Lonchidion paramilloensis, sp. nov., solely based on teeth, is within a 20-m-thick interval containing black shale interbedded with andesitic sills and intercalated with lensoidal calcarenites. The teeth have a characteristic labial peg with an accessory cusplet and a low gracile crown that is narrower labiolingually and more elongate laterally. The teeth are similar to some North American Late Triassic and Late Cretaceous species of the genus Lonchidion (e.g., L. humblei, L. griffisi, L. selachos), but are distinct in having a low primary cusp, up to seven pairs of lateral cusplets, a rounded-triangular-shaped labial peg with one accessory cusplet, and an absence of other crown ornaments. Color analyses of upper tooth crowns indicate an ichthyolith alteration index (IAI)/conodont alteration index (CAI) value of 6.0–6.5 (360–610°C). Considerable pitting and alteration of specimens indicates thermal alteration to 610°C and (or) chemical alteration.
ACKNOWLEDGMENTS
Special thanks are given to J. Fischer for providing literature and very helpful comments on an early review of the taxonomic part of the manuscript and a final comprehensive review of the completed manuscript. J. Rees provided valuable suggestions that have significantly improved the quality of the manuscript. This is our first submission to the Journal of Vertebrate Paleontology and the editors J. Harris, R. B. Holmes, A. Michel, and C. Underwood greatly helped to improve the manuscript presentation according to style and content standards. C. R. Barnes, School of Earth and Ocean Sciences, University of Victoria, British Columbia, Canada, is thanked for funding (through Natural Sciences and Engineering Research Council Discovery Grant) that supported the scanning electron microscope work and laboratory space and equipment. Supports from CONICET and Universidad Nacional de Córdoba, Argentina, are much appreciated.
Handling editor: Charlie Underwood