RESEARCH ARTICLE The first megatheropod tracks from the Lower Jurassic upper Elliot Formation, Karoo Basin, Lesotho L. Sciscio1*, E. M. Bordy1, M. Abrahams1, F. Knoll2, B. W. McPhee3 1 Department of Geological Sciences, University of Cape Town, Cape Town, South Africa, 2 Fundacio´n Conjunto Paleontolo´gico de Teruel-Dino´polis, Teruel, Spain, 3 Departamento de Biologia, FFCLRP, Universidade de São Paulo, São Paulo, Brazil a1111111111 * [email protected] a1111111111 a1111111111 a1111111111 a1111111111 Abstract A palaeosurface with one megatheropod trackway and several theropod tracks and track- ways from the Lower Jurassic upper Elliot Formation (Stormberg Group, Karoo Supergroup) in western Lesotho is described. The majority of the theropod tracks are referable to either OPEN ACCESS Eubrontes or Kayentapus based on their morphological characteristics. The larger mega- Citation: Sciscio L, Bordy EM, Abrahams M, Knoll theropod tracks are 57 cm long and have no Southern Hemisphere equivalent. Morphologi- F, McPhee BW (2017) The first megatheropod cally, they are more similar to the Early Jurassic Kayentapus, as well as the much younger tracks from the Lower Jurassic upper Elliot Upper Cretaceous ichnogenus Irenesauripus, than to other contemporaneous ichnogenera Formation, Karoo Basin, Lesotho. PLoS ONE 12 (10): e0185941. https://doi.org/10.1371/journal. in southern Africa. Herein they have been placed within the ichnogenus Kayentapus and pone.0185941 described as a new ichnospecies (Kayentapus ambrokholohali). The tracks are preserved Editor: William Oki Wong, Institute of Botany, on ripple marked, very fine-grained sandstone of the Lower Jurassic upper Elliot Formation, CHINA and thus were made after the end-Triassic mass extinction event (ETE). This new mega- Received: June 29, 2017 theropod trackway site marks the first occurrence of very large carnivorous dinosaurs (estimated body length 8–9 meters) in the Early Jurassic of southern Gondwana, an evolu- Accepted: September 21, 2017 > tionary strategy that was repeatedly pursued and amplified in the following ~135 million Published: October 25, 2017 years, until the next major biotic crisis at the end-Cretaceous. Copyright: © 2017 Sciscio et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Introduction Data Availability Statement: All photogrammetry During the first 30 million years of their evolution, dinosaurs constituted a relatively morpho- data is available from the Figshare database: DOI: logically non-diverse group of land vertebrates compared to contemporaneous crurotarsans 10.6084/m9.figshare.4747525. All silicon rubber [1, 2] with which they shared many Late Triassic ecosystems. The outset of the Jurassic wit- replicas of Kayentapus ambrokholohali are nessed the global evolutionary radiation of Dinosauria, with events associated with the end- available from the Ichnology Collection of the Evolutionary Studies Institute (ESI) at the Triassic mass extinction (ETE) and the Triassic-Jurassic boundary (TJB) often hypothesised to University of Witwatersrand, South Africa have played an important role [3]. The earliest Jurassic is thus a period of particular interest as (accession number: BP/6/735). it spans a post-extinction recovery period during which dinosaurs continued to thrive and Funding: This work was supported by the National diversify globally [3, 4]. This observation has been instrumental in recent interpretations that Research Foundation of South Africa Competitive favour abiotic contingency (“opportunism”) [5, 6] over competitive superiority in explaining Programme for Rated Researches [NRF Grant the ultimate success of the dinosaurs [3, 7]. PLOS ONE | https://doi.org/10.1371/journal.pone.0185941 October 25, 2017 1 / 28 Lower Jurassic megatheropod tracks from the Elliot Formation number 93544 Bordy]. LS and MA are recipients of During the Late Triassic and Early Jurassic, the largest carnivorous dinosaurs seldom sur- postdoctoral and postgraduate funding, passed 5 m in body length, as evidenced by both the skeletal and ichnofossil record [5]. Olsen respectively, from the DST-NRF Centre of et al. [5] suggested that “ecological release” associated with the disappearance of incumbent Excellence in Palaeosciences (CoE in Palaeosciences). BWM is a recipient of non-dinosaurian archosaurian predators across the TJB possibly explains the sudden leap in postdoctoral funding from FAPESP (Sao Paulo carnivorous dinosaur size thresholds in the Early Jurassic, as evidenced by the ichnospecies Research Foundation). FK is an ARAID researcher Eubrontes giganteus. (Aragon Agency for Research and Development, Thus, body size constraints have been linked to shifts in global ecosystem composition, Zaragoza, Spain). The funders had no role in study with medium to larger sized dinosaurs argued to be able to command a greater range of mor- design, data collection and analysis, decision to publish, or preparation of the manuscript. Opinions phospace following the ETE [2, 3]. This hypothesis, which potentially explains the appearance expressed and conclusions arrived at are those of of relatively large-bodied theropod dinosaurs within the earliest Jurassic, was based mainly on the authors and are not necessarily to be attributed the ichnology of the Newark Supergroup (USA) and has been received with some scepticism to the CoE in Palaeosciences or NRF CPRR. The e.g., [8, 9]. funders had no role in study design, data collection Amongst dinosaurs, Theropoda is remarkable for demonstrating continuous evolutionary and analysis, decision to publish, or preparation of novelty throughout the history of the clade, a phenomenon which is particularly noticeable at the manuscript. nodes proximate to the theropod-bird transition [10]. In the last decade, there have been many Competing interests: The authors have declared studies interested in dinosaurian, and specifically theropod, macroevolutionary patterns, with that no competing interests exist. the dynamics of changing body size playing a central role within this literature [2, 3, 10]. How- ever, reconstructing early theropod evolutionary patterns is much more problematic, with studies focused on discrete (morphological) characters depicting gradualistic rates of change for the group across the TJB [2]. In contrast, investigations utilising mass-estimates suggest a significant increase in body size for Theropoda within the Late Triassic [10]. A source of this confusion is the lack of theropod body fossils from this period. Theropod body fossils from the Early Jurassic are relatively rare, with Coelophysis bearing the largest number of well-preserved specimens globally [11, 12]. In contrast, the theropod ichnite record is comparatively rich and represents a good source of additional information independent of skeletal material. In general, Upper Triassic strata are dominated by an abundance of theropod ichnites between 20 cm to 25 cm in length (gralla- torid-sized) [8]. However, there does appear to be a preponderance for an increase in their size in the Early Jurassic based on the increased number of larger theropod ichnites, with the oldest known example of Eubrontes (35 cm) in North America (in a unit that is 10 ky younger than TJB-defined by palynomorphs [5]) and 34 cm in South Africa [13]. Despite the abundance of these Lower Jurassic theropod tracks and trackways, they are currently of relatively low generic diversity due to similarities in track morphology. This limits descriptions to within the one plexus of three ichnogenera (i.e. Grallator, Anchisauripus and Eubrontes) which are primarily distinguished by differences in size [8, 14]. In southern Africa, rare theropod body fossils and isolated teeth are present in Lower Juras- sic rocks [15–18]; whereas theropod tracks are common from the Late Triassic (e.g. [19]) and into the Early Jurassic (e.g. [20, 21]). These tridactyl tracks and trackways, despite their conser- vative foot morphology, allow for a more holistic treatment of theropod evolution, over the TJB. Here, we report, for the first time, a tridactyl dinosaur trackway site from the Elliot For- mation in the Roma Valley (Maseru District, Lesotho; Fig 1) that preserves the largest Early Jurassic theropod trackway to date. This new ichnofossil data from western Lesotho considerably expands the range of body- size displayed by carnivorous dinosaurs in the Early Jurassic in Gondwana, providing insight into the rate and tempo of body-size increase experienced by Theropoda across the ETE and the TJB (i.e., a punctuated, “release-type” versus a more step-wise body-size increase mirroring that of large-bodied dinosaurian herbivores, represented primarily by Sauropodomorpha). In addition to the morphological description of the tracks, we also document the associated taphono-sedimentary context of the trackway site and, using photogrammetry, provide a PLOS ONE | https://doi.org/10.1371/journal.pone.0185941 October 25, 2017 2 / 28 Lower Jurassic megatheropod tracks from the Elliot Formation Fig 1. Geological context of the megatheropod trackway (Matobo) site in the Roma Valley (Maseru District, Lesotho). (A) Location of the study area in western-central Lesotho within the main Karoo Basin of southern Africa. The inset shows the location of the site (footprint logo) and spatial distribution of the Upper Triassic to Lower Jurassic Elliot