The first theropod tracks from the Middle Jurassic of Gansu, Northwest China: new and rare evidence of quadrupedal progression in theropod dinosaurs

Abstract

A new Middle Jurassic tracksite dominated by non-avian theropod footprints from the Wangjiashan Formation in Pingchuan District, Baojishan Basin, Gansu Province has yielded a unique trackway with four consecutive manus-pes sets. Only three previous examples, all Early Jurassic in age, of theropod trackways are known with convincing examples of manus tracks and in each case, only two tracks were recorded in association with pes tracks with metatarsal impressions and pelvic traces indicating crouching behavior. Thus, this is the first example of manus tracks registered while a theropod trackmaker was walking. This unique configuration is here designated as Grallator pingchuanensis ichnosp. nov. which shows the trackmaker forelimbs registering in a wide straddle gait, much wider than the pes trackway width. G. pingchuanensis confirms previous reports that theropods could occasionally register tridactyl, ectaxonic manus traces. In the case of the Pingchuan trackway, the short step indicates an animal moving at a slow speed, probably due to a soft substrate.

Tracking the Pliensbachian–Toarcian Karoo firewalkers: Trackways of quadruped and biped dinosaurs and mammaliaforms

“…Regarding trackmaker identity, there are no universally recognized theropod trackway morphotypes (ichnotaxa) that indicate obligate quadrupeds. On the contrary, the only trackways that include manus tracks are associated with crouching or squatting behavior (see [95] for review). The only possible exception appears to be the Atreipus trackmaker with its Grallator-like pes.…”

Theropod Tridactyl Tracks Across the Triassic–Jurassic Boundary in Southern Africa: Implications for Pedal Morphology Evolution

“…Due to the conservative nature of tridactyl track morphology, distinguishing between different dinosaurian trackmakers can be riddled with complexities, e.g., theropod versus ornithopod (see Moratalla et al, 1988;Romilio and Salisbury, 2011), theropod versus "prosauropod" (see Weems, 2019). Nevertheless, Kayentapus is widely accepted to have a theropod trackmaker (e.g., Lockley et al, 2011;Sciscio et al, 2017), while, based on the eastern North American track record, Grallator-Anchisauripus-Eubrontes have been attributed to at least two distinct trackmakers (Farlow et al, 2018), which are generally accepted to be theropods (e.g., Lockley, 1991;Olsen et al, 1998;Castanera et al, 2016;Li et al, 2019;cf. Weems, 2019).…”

Saurischian dinosaur tracks from the Upper Triassic of southern Queensland: possible evidence for Australia’s earliest sauropodomorph trackmaker

“…Footprints can only be registered when an animal is alive. As such, tracks have the potential to provide insights into the temporal and spatial occurrences of trackmaker taxa, a plethora of their behaviours (e.g., posture, stance, sociality), as well as revealing aspects of their ecology (e.g., coeval trackmaker diversity, preferred environments) (Gierliński and Potemska 1987;Whyte et al 2007;Xing et al 2011;Avanzini et al 2012;Lim et al 2012;Romilio et al 2013Romilio et al , 2021Li et al 2019;Romilio 2020a). Similarly, when tracks are fossilised, they can provide a resource for ascertaining information about once living trackmakers.…”