Cretaceous Research 51 (2014) 186e207 Contents lists available at ScienceDirect Cretaceous Research journal homepage: www.elsevier.com/locate/CretRes Large dinosaurian tracks from the Upper Cretaceous (CenomanianeTuronian) portion of the Winton Formation, Lark Quarry, central-western Queensland, Australia: 3D photogrammetric analysis renders the ‘stampede trigger’ scenario unlikely * Anthony Romilio , Steven W. Salisbury School of Biological Sciences, The University of Queensland, Brisbane, Qld 4072, Australia article info abstract Article history: The largest dinosaurian tracks at Lark Quarry, central-western Queensland, Australia, were re-examined Received 13 November 2013 using revised analytical protocols that incorporate three-dimensional (3D) structure. Comparisons were Accepted in revised form 8 June 2014 made with archival photographs, replica specimens (c. 1977) and the in situ tracks (2013) to account for Available online changes to the track surface. Damage caused both during and after the excavation of the tracks was evident, and in cases where the archival photographs and 1970's replicas strongly differ from the in situ Keywords: tracks, it is apparent that restoration has modified the original track morphology. Ichnology Even after accounting for recent damage and alteration, several of the track morphologies obtained Dinosaur tracks Winton Formation from new 3D evaluation models differ considerably from the track outlines that were published in the Cretaceous original description of the site. Compared with the new set of representations, some of the original Australia outlines seem to represent simpler, stylized versions of the tracks. A number of the original outlines are >20% larger than the in situ tracks, while others appear to incorporate cracks as part of the margin of digit impressions. Overall, the best-preserved tracks show blunt digit impressions, reaffirming the idea that the trackmaker was a large ornithopod and supporting a reassignment to cf. Iguanodontipus. The new analysis also reveals the nature of the displacement rims associated with the tracks, and the overprinting of these rims by other ichnitesdinitially by tool marks (presumably caused by floating vegetation) and then by other dinosaurian tracks (assignable to Wintonopus latomorum). In the context of these observations, we see no evidence for an interaction between the cf. Iguanodontipus trackmaker and the smaller-bodied W. latomorum trackmakers, as neither can be inferred to have been present at the tracksite at, or even close to the same time. Similarly, there is no evidence to support the idea that the approach of the cf. Iguanodontipus trackmaker in some way triggered the movement of the W. latomorum trackmakers. Rather than a snap-shot of dinosaurian ‘stampede’, this study supports the idea that Lark Quarry most likely represents a complex time-averaged assemblage of multiple dinosaurian ichnites, preserved over an extended period of time (hours to days) and bracketed by discrete phases of track- maker activity and fluctuations in water depth. © 2014 Elsevier Ltd. All rights reserved. 1. Introduction the composition of dinosaurian communities and palaeoecology (Adams and Breithaupt, 2003; Matsukawa and Lockley, 2007). In Dinosaurian tracks and trackway data preserved in a single instances where several ichnotaxa are represented on the same bedding horizon have the potential to reveal information on the track surface, some researchers (e.g. Bird, 1954, 1985; Farlow et al., abundance and diversity of contemporaneous dinosaurian track- 2012) have also speculated on possible palaeobiological in- makers in a given area (Fastovsky and Smith, 2004; Matsukawa and teractions between trackmakers with similarly oriented trackways. Lockley, 2007). This information may in turn provide insights into However, the presence of multiple tracks on a track surface typi- cally indicates the formation of ichnites within a single recording period, and not necessarily the presence of multiple trackmakers at * Corresponding author. the same moment (Fastovsky and Smith, 2004). E-mail address: [email protected] (A. Romilio). http://dx.doi.org/10.1016/j.cretres.2014.06.003 0195-6671/© 2014 Elsevier Ltd. All rights reserved. A. Romilio, S.W. Salisbury / Cretaceous Research 51 (2014) 186e207 187 The Lark Quarry dinosaurian tracksite (within the Cen- omanianeTuronian portion of the Winton Formation), located 95 km south-west of Winton, central-western Queensland (Fig. 1), has multiple tracks assigned to different ichnotaxa. The tracks occur on a single track surface (Fig. 2), arousing speculations of possible interactions between the dinosaurian trackmakers (e.g. Thulborn and Wade, 1984; Paul, 1988; Lockley and Matsukawa, 1999; Roach and Brinkman, 2007; Thulborn, 2013). Numerous tracks have been interpreted as preserving evidence for the pres- ence of two types of small dinosaurian trackmakersdsmall-bodied ornithopods and theropodsdand a much larger bipedal dinosau- rian trackmaker, initially considered to be a theropod (Thulborn and Wade, 1984). Most of the trackways produced by the small- bodied dinosaurs have the same orientation, and it was originally speculated that their trackmakers formed a co-operative, mixed herd of more than 150 individuals caught up in a terrestrial stam- pede (Thulborn and Wade, 1984). Several alternative in- terpretations have also been proposed: the small-bodied theropodan trackmakers were an avian or near-avian species posing no threat to the co-herding ornithopodan trackmakers (Roach and Brinkman, 2007); the small-bodied theropodan track- makers were a threat and co-operatively hunted the herding ornithopodan trackmakers (Paul, 1988); some of the small-bodied trackmakers were swimming (Moreno et al., 2004; Romilio et al., 2013); the small-bodied trackmakers were either two types of theropods, two types of ornithopods, or “a single taxon of either group” (Matsukawa and Lockley, 2007: 30). Romilio et al. (2013) re- e evaluated the small dinosaurian tracks and concluded that the two Fig. 2. Lark Quarry tracksite, April 2013. Several of the largest tracks (tracks 4 7; R2eL4) are discernable, as are tool marks (tm) possibly caused by partially buoyed previously recognized ichnotaxa (i.e. Wintonopus latomorum and vegetation. Thousands of very small dinosaur tracks appear as numerous ‘pits’ over the © Skartopus australis) represented ichnomorphs (sensu Fastovsky and exposed surface. Photograph S. W. Salisbury. Smith, 2004) and not separate ichnotaxa, with all of these tracks being assignable to the ornithopodan ichnotaxon W. latomorum. The complex track patterns present at Lark Quarry had also led indicates the large-bodied trackmaker “was heading in the oppo- to speculation that the small-bodied dinosaurian trackmakers may site direction” (Thulborn, 2013:3)dand in some way “triggered” a have interacted or responded in some way to the presence of a stampede (Thulborn and Wade, 1984: 413, 443). This scenario re- much larger one (Thulborn and Wade, 1984). In the context of this quires the largest Lark Quarry tracks to have been formed at “about interpretation, the largest Lark Quarry trackmaker was considered the same time” as the small-bodied dinosaur traces (Thulborn and to have ‘approached’ the smaller trackmakers (Thulborn and Wade, Wade, 1984: 446). Thulborn and Wade (1984) described the largest 1984: 413, 443, 445, 455)deven though the trackway data tracks and those formed by small-bodied dinosaurian trackmakers Fig. 1. A, A map of north-eastern Australia, with the position of the Lark Quarry dinosaur tracksite (23.0161 S, 142.4114 E); B, Stratigraphy of the Eromanga Basin, central-western Queensland. Abbreviations: C.B., Carpenteria Basin; E.B., Eromanga Basin; S.B., Surat Basin; G.A.B., Great Artesian Basin; W.F., exposed Winton Formation; QLD, Queensland; NSW, New South Wales; SA, South Australia; NT, Northern Territory. Adapted from Romilio et al. (2013), Tucker et al. (2013: 1) and Berrell et al. (in press). 188 A. Romilio, S.W. Salisbury / Cretaceous Research 51 (2014) 186e207 as having been formed only when a period of subaqueous condi- and the overall interpretation of the site proposed by Thulborn and tions had lapsed, leaving the surface subaerially exposed. During Wade (1984) were correct. the inferred initial period of subaqueous exposure, partially buoyed While documenting tracks as 2D drawn outlines has been one of vegetation floated over the site, leaving a series of parallel drag the traditional methods employed in dinosaur ichnology, there is marks (tool marks). In this scenario, the tool marks are made prior no escaping the fact that the vast majority of tracks are 3D struc- to the large dinosaurian tracks. tures. Any representations of tracks in 2D means that information Romilio et al. (2013) examined the Lark Quarry dinosaurian relating to depth is subsequently lost or ‘compressed’, with the ichnites and concluded that the apparent en masse interactions of depicted outlines being reliant on the interpretation of the inves- the small-bodied dinosaurian trackmakersdwhich would be tigator, making them highly subjective (Bates et al., 2008b). necessary for a stampededas proposed by Thulborn and Wade Thulborn and Wade (1984) documented the largest Lark Quarry (1984), was highly unlikely. Instead, Romilio et al. (2013) pro- tracks using traditional methods of photography and drawn out- posed that different sized swim traces could be linked to likely lines. All the tracks were depicted in dorsal view as 2D outlines