Reevaluation of the Lark Quarry dinosaur Tracksite (late Albian–Cenomanian Winton Formation, central-western Queensland, Australia): no longer a stampede?

Abstract

Extensive and well-preserved tracksites in the coastally exposed Lower Cretaceous (Valanginian-Barremian) Broome Sandstone of the Dampier Peninsula provide almost the entire fossil record of dinosaurs from the western half of the Australian continent. Tracks near the town of Broome were described in the late 1960s as Megalosauropus broomensis and attributed to a medium-sized theropod trackmaker. Brief reports in the early 1990s suggested the occurrence of at least another nine types of tracks, referable to theropod, sauropod, ornithopod, and thyreophoran trackmakers, at scattered tracksites spread over more than 80 km of coastline north of Broome, potentially representing one of the world's most diverse dinosaurian ichnofaunas. More recently, it has been proposed that this number could be as high as 16 and that the sites are spread over more than 200 km. However, the only substantial research that has been published on these more recent discoveries is a preliminary study of the sauropod tracks and an account of the ways in which the heavy passage of sauropod trackmakers may have shaped the Dampier Peninsula's Early Cretaceous landscape. With the other types of dinosaurian tracks in the Broome Sandstone remaining undescribed, and the full extent and nature of the Dampier Peninsula's dinosaurian tracksites yet to be adequately addressed, the overall scientific significance of the ichnofauna has remained enigmatic.At the request of the area's Goolarabooloo Traditional Custodians, 400C hours of ichnological survey work was undertaken from 2011 to 2016 on the 25 km stretch of coastline in the Yanijarri-Lurujarri section of the Dampier Peninsula, inclusive of the coastline at Walmadany (James Price Point). Forty-eight discrete dinosaurian tracksites were identified in this area, and thousands of tracks were examined and measured in situ and using three-dimensional photogrammetry. Tracksites were concentrated in three main areas along the coast: Yanijarri in the north, Walmadany in the middle, and Kardilakan-Jajal Buru in the south. Lithofacies analysis revealed 16 repeated facies types that occurred in three distinctive lithofacies associations, indicative of an environmental transgression between the distal fluvial to deltaic portions of a large braid plain, with migrating sand bodies and periodic sheet floods. The main dinosaurian track-bearing horizons seem to have been generated between periodic sheet floods that blanketed the preexisting sand bodies within the braid plain portion of a tidally influenced delta, with much of the original, gently undulating topography now preserved over large expanses of the present day intertidal reef system. Of the tracks examined, 150 could be identified and are assignable to a least eleven and possibly as many as 21 different track types: five different types of theropod tracks, at least six types of sauropod tracks, four types of ornithopod tracks, and six types of thyreophoran tracks. Eleven of these track types can formally be assigned or compared to existing or new ichnotaxa,...

Investigating the stratigraphy and palaeoenvironments for a suite of newly discovered mid-Cretaceous vertebrate fossil-localities in the Winton Formation, Queensland, Australia

“…Interlaminated sandy siltstones to silty mudstones are moderately common throughout the outcrop and core (Table 4) ponding in inactive fluvial channels, closely followed by minor stream flow (Thulborn and Wade, 1984;Buatois andMangano, 1995, 2011;Romilio et al, 2013).…”

“…Iguanodontipus (Romilio and Salisbury, 2014). Originally, Thulborn and Wade (1979) interpreted the Lark Quarry trackway to preserve a 'pursuit scenario' set within lacustrine setting, yet, recent revisions by Romilio et al (2013;2014) have interpreted Lark Quarry to preserve a timeaveraged (day's) track assemblage along a developing riverbank undergoing a waning flow period. Track evidence indicates that trackmakers interacted with both higher flow depths (swimming tracks) and shallower depths (walking and running) within a short period of time (days).…”

The tracks of giant theropods (Jurabrontes curtedulensisichnogen. & ichnosp. nov.) from the Late Jurassic of NW Switzerland: palaeoecological & palaeogeographical implications

“…If this is not the case, pads but with tapering sharply to V-shaped tips and evidence for long, robust and sharply-pointed claws, and with dII and dIV distinctly shorter than dIII. Recently, Romilio et al (2013) have re-analysed this trackway and assigned it to Amblydactylus cf. A. gethingi, which in turn was questioned by Thulborn (2013) and addressed again by Romilio & Salisbury (2014).…”

A close look at Victoria's first known dinosaur tracks

“…Furthermore, the Victoria tracks resemble Iguanodontipus, which has been attributed to Early Cretaceous iguanodontids (Sarjeant et al, 1998;Cobos and Gascó, 2012), although these are often much larger (Castanera et al, 2013). In Australia, Wintonopus of the Lower Cretaceous Winton Formation (Queensland) is another small ornithopod track comparable to the Victoria specimens (Thulborn and Wade, 1984;Romilio et al, 2013). In short, similarities between the Victoria tracks and these ichnogenera affirm that their likely tracemakers were small ornithopods.…”