Shrinking the World's Largest Dinosaur Tracks: Observations on the Ichnotaxonomy of Gigantosauropus asturiensis and Hispanosauropus hauboldi from the Upper Jurassic of Asturias, Spain

Abstract

The type material of the ichnospecies Gigantosauropus asturiensis Mensink and Mertmann 1984 is re-examined and shown to represent a sauropod rather than a theropod. This interpretation confirms the recent suggestions of several authors. We describe the trackway in detail but conclude that it is not diagnostic at any taxonomic level, below the general category of sauropod. Thus, G. asturiensis may legitimately be considered a nomen dubium, and the name should be restricted to the original material and not extended to formally describe other poorly preserved specimens. Claims that the largest pes tracks are 1.35 or even 1.5 m in length are incorrect. Pes length ranges from 98–125 cm (mean 110.75 cm).

Hispanosauropus hauboldi Mensink and Mertmann 1984 is also of doubtful utility as previously defined. The holotype, a field specimen, which clearly represents a theropod dinosaur, cannot be located, and may be lost to erosion. The paratype is a sauropod track and therefore has no relevance to the ichno-species description. Therefore, we select a new paralectotype and provide a more detailed description of specimens that can be assigned to this ichnotaxon. Hispanosauropus is similar to tracks recently described under the label Megalosauripus. However, the status of this latter ichnogenus, and the spectrum of track types to which it refers, is disputed. Thus, we provisionally restrict the name Hispanosauropus to the original illustrated holotype and a paralectotype from the same locality. On the grounds of morphological similarity, the name may be applied to similar material from elsewhere in the Upper Jurassic of Asturias.

Keywords:

• Ichnotaxonomy
• saurischian tracks
• Late Jurassic
• Asturias
• Spain

ACKNOWLEDGEMENTS

This study was supported by the Proyecto de Investigación Concertada FC-02-PC-CIS01–56 (FICYT)-Consejeria de Educación y Cultura del Principado de Asturias, and by the offices of the Dinosaur Traces Museum, University of Colorado at Denver. We thank Spencer Lucas, New Mexico Museum of Natural History and Science, and Andrew Milner, St. George Dinosaur Discovery Site, for their helpful reviews. We also thank Reiji Kukihara for his help with the diagrams.