El Barrancazo: a new locality of possible semi-aquatic turtle tracks from the Upper Triassic of Cortes de Pallás (Eastern Iberia)

Abstract

This work describes the new vertebrate tracksite named El Barrancazo, located in Cortes de Pallás (Eastern Iberia). This new site turns this area into the one that concentrates the largest number of vertebrate footprints from the Upper Triassic of Iberia. The footprints are presented as natural casts distributed in isolated blocks belonging to the Manuel Formation (K2, Keuper facies), deposited during the Carnian Pluvial Episode (Late Triassic). The blocks come from two beds of the same outcrop. The tracks are made up of sub-parallel digital impressions, displaying occasional curved traces, often without forming a complete outline, and showing a set of features such as lateral and posterior overhangs, longitudinal striations or digital reflectures, among others. These features, taken together with the sedimentological analysis carried out, suggest that animals moving in totally or partially buoyant conditions in a fluvial environment produced most of these tracks. The size and morphology of these paleoichnological impressions suggest that they were probably produced, in some cases, by turtles, adding to the understanding of the paleoenvironmental and paleofaunistic conditions of the Late Triassic of Iberia during the Carnian, a key period in the evolution of different groups of continental vertebrates. In this paper we show the comparative study of the three sites described to date in Cortes de Pallás and an analysis of the interplay of trackmaker organism, animal behavior and substrate in the resulting morphology of tracks made under subaqueous conditions.