Unusual sauropod tracks in the Jurassic-Cretaceous transition. Cameros Basin (Burgos, Spain)

F. Torcida Fernández-Baldor,I. Díaz-Martínez,R. Contreras,D. Montero,P. Huerta,V. Urién

doi:10.5209/rev_jige.2015.v41.n1.48660

Abstract

The Las Sereas site includes at least 14 ichnological outcrops along 5.6 km, in the Lara area, southwest Burgos Province. 67 ichnites of dinosaurs are documented at Las Sereas 7, identified as theropod and sauropod trackways occurring in shallow carbonates of lacustrine environment. Sauropod trackways have intermediate-gauge and low heteropody, and show different anatomical features to other tracks found in the ichnological record, especially in the disposition and orientation of pes digits. They are similar to Polyonyx from the Middle Jurassic of Portugal. However, since they do not preserve reliable manus data they are classified as aff. Polyonyx. The three sauropod trackways are related to the same kind of trackmaker. They differ from each other only in size, and gregarious behavior has not been detected. Analysis of these trackways reveals changes in travel direction even when there are few tracks in each sequence. At the Las Sereas 7 tracksite, the pace length (PL), width of the angulation pattern (WAP) and the WAP/PL ratio and depth analysis via photogrammetry show a direction change in two sauropod trackways. This tracksite and that at La Pedraja are unique in the Tithonian-Berriasian interval of the Iberian Peninsula that occur in a lacustrine environment, and could be indicate of the relationship between the diversity of Iberian, Tithonian-Berriasian sauropod tracks and sedimentary environments.

Highlights

In the Iberian Peninsula, the dinosaur ichnological record of Tithonian-Berriasian (Jurassic-Cretaceous transition) interval is abundant
Fig. 4.- a) Picture, b) false-color depth map of the photogrammetric model and c) contour lines map with 0.5 cm of equidistance of a part of the sauropod trackways LS7A and LS7B. d) Picture, e) false-color depth map of the photogrammetric model and f) contour lines map with 0.5 cm of equidistance of a part of the sauropod trackway LS7B. g) Picture, h) false-color depth map of the photogrammetric model and i) contour lines map with 0.25 cm of equidistance of theropod track LS7D,4
The biped trackways LS7D and LS7E and some isolated footprints have the same orientation in the direction of progression (W-E)

Summary

Introduction

In the Iberian Peninsula, the dinosaur ichnological record of Tithonian-Berriasian (Jurassic-Cretaceous transition) interval is abundant. Tracksites have been found in the Tithonian of Portugal (e.g., Santos, 2003; Mateus and Milàn, 2008, 2010), and in the Tithonian-Berriasian interval Some authors have suggested that there are differences between Jurassic and Cretaceous dinosaur ichnofaunas G., Lockley et al, 2004; Hunt and Lucas, 2006; Moratalla, 2009). Hunt and Lucas (2006) considered that ornithopod tracks are more abundant in Cretaceous outcrops. Lockley et al (2004) observed that narrow-gauge sauropod trackways are predominant in Jurassic units and wide-gauge in the Cretaceous ones. The study of TithonianBerriasian interval tracksites from Iberia is important for understanding dinosaur evolution

Objectives

Discussion

Conclusion