Speeds and stance of titanosaur sauropods: analysis of Titanopodus tracks from the Late Cretaceous of Mendoza, Argentina

Bernardo J González Riga

doi:10.1590/s0001-37652011005000002

Abstract

Speed estimations from trackways of Titanopodus mendozensis González Riga and Calvo provide information about the locomotion of titanosaurian sauropods that lived in South America during the Late Cretaceous. Titanopodus ichnites were found at Agua del Choique, a newly discovered track site in the Loncoche Formation, Late Campanian-Early Maastrichtian of Mendoza, Argentina. This speed study follows the hypothesis of dynamic similarity proposed by Alexander. As a refinement of this method, a complementary equation is presented here based on an articulated titanosaurian specimen collected in strata that are regarded as correlative to those that have yielded Titanopodus tracks (Allen Formation, Neuquén Basin). This analysis indicates that hip height can be estimated as 4.586 times the length of the pes track in derived titanosaurs. With an estimation of the hip height and the stride measurements, the speed is calculated. The study of two wide-gauge trackways indicates that Titanopodus ichnites were produced by medium-sized titanosaurs (hip height of 211-229 cm) that walked at 4.7-4.9 km/h towards the south and southwest, following, in part, a sinuous pathway. These speeds and some taphonomic features of tracks (prominent rims, distorted elongated shapes)indicate the capacity of derived titanosaurs for walking effectively over a very wet and slippery substrate. In the ichnological record, the walking speeds of Titanopodustrackmakers are somewhat faster than those previously inferred for most sauropods.

Highlights

Important dinosaur tracksites have been described in South America, in Chile (Casamiquela and Fasola 1968, Moreno and Pino 2002, Moreno et al 2004, Moreno and Benton 2005), Bolivia, and Brazil (Leonardi 1989, Meyer et al 2001, Lockley et al 2002)
In Argentina, dinosaur track sites are known from Salta, Neuquén, and Mendoza provinces
The objective of this paper is to study, for the first time, the speeds and stance of the Titanopodus trackmakers

Summary

Introduction

Important dinosaur tracksites have been described in South America, in Chile (Casamiquela and Fasola 1968, Moreno and Pino 2002, Moreno et al 2004, Moreno and Benton 2005), Bolivia, and Brazil (Leonardi 1989, Meyer et al 2001, Lockley et al 2002). In Salta (near eastern Puna), theropod and ornithopod tracks were discovered in the upper levels of the Yacoraite Formation (Maastrichtian) (Alonso 1980, Alonso and Marquillas 1986). In this province, sauropod footprints have not been described yet. In Neuquén (northern Patagonia), dinosaur tracks have been found in the Picún Leufú and El Chocón areas (Fig. 1) These tracks were found in outcrops of the Candeleros Formation (Cenomanian), a unit that is characterized by deposits corresponding to meandering rivers, poorly channeled ephemeral flows, and playa lakes. Titanosaurian tracks from this formation were named Sauropodichnus giganteus (Calvo 1991, 1999)

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