Fast-running theropods tracks from the Early Cretaceous of La Rioja, Spain

Abstract

Theropod behaviour and biodynamics are intriguing questions that paleontology has been trying to resolve for a long time. The lack of extant groups with similar bipedalism has made it hard to answer some of the questions on the matter, yet theoretical biomechanical models have shed some light on the question of how fast theropods could run and what kind of movement they showed. The study of dinosaur tracks can help answer some of these questions due to the very nature of tracks as a product of the interaction of these animals with the environment. Two trackways belonging to fast-running theropods from the Lower Cretaceous Enciso Group of Igea (La Rioja) are presented here and compared with other fast-running theropod trackways published to date. The Lower Cretaceous Iberian fossil record and some features present in these footprints and trackways suggest a basal tetanuran, probably a carcharodontosaurid or spinosaurid, as a plausible trackmaker. Speed analysis shows that these trackways, with speed ranges of 6.5–10.3 and 8.8–12.4 ms−1, testify to some of the top speeds ever calculated for theropod tracks, shedding light on the question of dinosaur biodynamics and how these animals moved.

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“…Evidence of running dinosaurs has been reported in several tracksites (e.g. Farlow, 2018;Navarro-Lorbés et al, 2021;Pérez-Lorente, 1996). Alexander (1976) hypothesised that animals run when the ratio between stride length (Sl) and the acetabular height (h) is greater than 2 (Sl/h > 2), and if this ratio is less than 2, the animal walks.…”

“…A recent study identified two running theropod trackways (Fig. 3A, D) among the fastest calculated for dinosaurs in the Lower Cretaceous of La Rioja (Spain) showing a speed between 6.5 and 10.3 ms −1 and between 8.8 and 12.4 ms −1 (Navarro-Lorbés et al, 2021). It is newsworthy that all of the previously mentioned trackways, which are the fastest in the world to date, have in common a similar size (similar footprint length), showing that the "best runners" were trackmakers with feet between 29 and 39 cm long (Farlow, 2018;Lockley et al, 2021;Navarro-Lorbés et al, 2021).…”

“…3A, D) among the fastest calculated for dinosaurs in the Lower Cretaceous of La Rioja (Spain) showing a speed between 6.5 and 10.3 ms −1 and between 8.8 and 12.4 ms −1 (Navarro-Lorbés et al, 2021). It is newsworthy that all of the previously mentioned trackways, which are the fastest in the world to date, have in common a similar size (similar footprint length), showing that the "best runners" were trackmakers with feet between 29 and 39 cm long (Farlow, 2018;Lockley et al, 2021;Navarro-Lorbés et al, 2021). Nevertheless, biomechanical models based on musculoskeletal reconstructions and the application of physical dynamics suggest higher values of maximum speed than those obtained from the ichnological record (see table 3 of Navarro-Lorbés et al, 2021).…”

“…The tracks shown in the examples come from tracksites (named in the sequence figured in the text) located in the Maestrazgo basin (Teruel Province) and eastern Cameros basin (La Rioja and Soria provinces). These tracksites are: Aliaga-Miravete megatracksite (Camarillas Fm., Barremian, Navarrete et al, 2014); Río Alcalá tracksite (Camarillas Fm., Barremian, Cobos et al, 2016); Las Cuestas I tracksite (Huérteles Fm., Berriasian, Castanera et al, 2012;Pascual-Arribas et al, 2008); Las Villasecas (Huérteles Fm., Berriasian, Barco et al, 2005;Castanera et al, 2015); Valdehijuelos tracksite (Huérteles Fm., Berriasian, Pascual-Arribas and Hernández-Medrano, 2011;Castanera et al, 2015); Barranco de La Canal (Enciso Gr., Barremian-Aptian, Pérez-Lorente, 2003;Razzolini et al, 2016); La Torre 6B tracksite (Enciso Gr., Barremian-Aptian, Navarro-Lorbés et al, 2021); La Virgen del Campo 4 trackiste (Enciso Gr., Barremian-Aptian, Ezquerra et al, 2007); La Laguna tracksite (Urbion Gr., Barremian-Aptian, Navarro-Lorbés et al, 2023); Las Cerradicas tracksite (Villar del Arzobispo Fm/Cedrillas Fm, Tithonian, Castanera et al, 2011Castanera et al, , 2013aCastanera et al, , 2013bAurell et al, 2019;Campos-Soto et al, 2017); Fuentesalvo tracksite (Huérteles Fm., Berriasian, Castanera et al, 2013b); and Soto 2 tracksite (Oncala Gr., Berriasian, Pérez-Lorente, 2015).…”

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“…In a landmark paper, Alexander (1976) used a variety of extant animals with known running speeds to relate speed, stride length, and hip height. As a result, measuring distances between tracks and track length has been a crucial component of characterizing track sites (e.g., Farlow, 1981; Kozu et al, 2017; Moreno et al, 2012; Navarro‐Lorbés et al, 2021). More recently, evolutionary robotics and biomechanical modeling approaches have been employed with body fossils to assess both gait and running speed (Bates et al, 2012; Hutchinson, 2004; Sellers & Manning, 2007).…”