Fish trace fossils from the Lower Cretaceous of Puebla, Mexico

Abstract

A great amount of studies dealing with vertebrate paleoichnology, are based on footprints made by terrestrial vertebrates; studies on fish paleoichnology, however, are less common, in spite that fish behaviour has the potential to leave different types of bioerosion and/or bioturbation structures. Recent fieldwork on southeastern Puebla (Central Mexico), has yielded two Lower Cretaceous fish trace fossils, from the sedimentary sequence of the San Juan Raya Formation (upper Valanginian to lower Hauterivian). Osculichnus tepitsin isp. nov., is represented by small epichnial traces, lenticular in outline, with two elongate lip-like lobes, separated by a M-shaped elongate furrow. The lower jaw lobe is thick, and nearly subrectangular; the upper jaw lobe bears a ventral convex projection of the medial portion; two short, sub-triangular, maxillary barbel impressions are preserved. Osculichnus tepitsin ichnosp. nov., is a benthic feeder fish trace fossil that represents, to date, the smallest ichnospecies of the ichnogenus Osculichnus; it is the first time that this ichnogenus is reported from Mexico, from the American Continent, and from Lower Cretaceous rocks anywhere in the world. Daandavichnus batoideum ichnogen. and ichnosp. nov., is a trace fossil circumscribed within a small, sub-circular to trapezoid, outline; the anterior area bears a deep impression with a M-shaped external boundary; the posterior area, preserves two circular depressions, with smooth borders; Daandavichnus batoideum ichnogen. and ichnosp. nov., is interpreted as the impression of the distal part of the jaw apparatus of a small-sized member of Batoidea, originated during the symmetrical protrusion, while feeding in the benthos. Together with the ichnogenera Piscichnus and Osculichnus, Daandavichnus becomes the third ichnogenus that represents a fish feeding trace fossil, in this case a small member of Batoidea. The close assoaciation of these new trace fossils, together with invertebrate traces such as Skolithos and Helminthoidichnites; as well as xiphosuran feeding traces (Selenichnites), give insights into the well stablished trophic relationships of one of the Lower Cretaceous ecosystems, represented within the sedimentary sequence of the San Juan Raya Formation in southern Puebla, Mexico.