Hidden for one hundred years: a diverse theropod ichnoassemblage and cross-sectional tracks from the historic Early Jurassic Tsikoane ichnosite (Clarens Formation, northern Lesotho, southern Africa)

Abrahams, Miengah; Bordy, Emese M.; Knoll, Fabien

doi:10.1080/08912963.2020.1810681

Cited by 13 publications

(6 citation statements)

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“…In addition, trace fossils (termite nests, vertebrate tracks) and plant remains, especially petrified wood, have also been documented (e.g. Ellenberger, 1970; Bamford, 2004; Bordy, 2008; Bordy et al ., 2009, 2021; Bordy & Head, 2018; Abrahams et al ., 2021; Mukaddam et al ., 2021). The diverse fossil record of the Clarens Formation is the ultimate evidence for wetter conditions and thriving localized ecosystems within this overall desert setting.…”

Section: Geological Backgroundmentioning

confidence: 99%

Lake dynamics in an Early Jurassic desert: Evidence from the Clarens Formation in southern Africa

Head

Bordy

2022

Sedimentology

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Interdune deposits are sensitive to climatic fluctuations and ancient interdune lacustrine systems can reveal the drivers of erg dynamics through time and space. This southern African study details the dynamics of interdune deposition in a vast ancient desert system that was active over Pangaea in the Middle Mesozoic and formed part of one of the largest known sand seas in Earth's history. Focusing on the Sinemurian to Pliensbachian Clarens Formation in the main Karoo Basin (south-west Gondwana), three facies associations were identified that formed in meso-scale and macro-scale lakes amongst aeolian dunes and sand sheets of the Clarens erg system. The northern facies association is restricted to interdune hollows within an actively climbing dune system. High-sediment availability and high-wind speeds limited the space available for these meso-scale lakes to expand. Here, migrating dunes outpaced the water table rise promoting the formation of discontinuous lenses of lake deposits, as is typical in erg centres. The southern facies associations developed both in spatially isolated meso-scale lakes, where flooding was controlled by groundwater inundation (water table rise), as well as in macro-scale lakes, where flooding was related to groundwater inundation and floods (surface runoff) that induced terminal splays. Relative to the north, the southern facies associations, with their more significant thickness and lateral extent, show that, here, the basin was characterized by a higher rate of relative subsidence. Moreover, the southern lake systems were established along the erg's margin, where the interdunes expanded during pluvial phases. Ultimately, the facies associations in the Clarens Formation show that the widespread arid conditions in the Early Jurassic of south-west Gondwana were subjected to prolonged and repeated pluvial phases in an otherwise harsh environment. Given the prominence of Jurassic aeolianites across Pangea, this study provides a southern African perspective on global palaeoerg dynamics and Early Jurassic climatic shifts.

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Section: Geological Backgroundmentioning

confidence: 99%

Lake dynamics in an Early Jurassic desert: Evidence from the Clarens Formation in southern Africa

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Bordy

2022

Sedimentology

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“…In the early Mesozoic ichnological record of the main Karoo Basin of southern Africa, tracks referable to Grallator are not rare. [6][7][8][9][10][33][34][35][36][37] Being only ~1 cm longer than the smallest Grallator tracks in southern Africa (described 10 from the lower part of the upper Elliot Formation in Lesotho), the Storm Shelter tracks, with their average footprint length of 7.5 cm, are among the smallest Grallator-like tracks in the Lower Jurassic of this region, and certainly the smallest of all dinosaur tracks in the Clarens Formation to date. parameters (e.g.…”

Section: Discussionmentioning

confidence: 99%

Darting towards Storm Shelter: A minute dinosaur trackway from southern Africa

Bordy

2021

S. Afr. J. Sci.

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Theropod dinosaurs are considered the main terrestrial carnivores in the Jurassic and Cretaceous. Their rise to dominance has been linked to, among others, body size changes in their early history, especially across the Triassic–Jurassic boundary. However, to qualitatively assess such temporal trends, robust skeletal and trace fossil data sets are needed globally. The richly fossiliferous southern African continental rock record in the main Karoo Basin offers an unparalleled perspective for such investigations. Herein, by documenting a newly discovered Early Jurassic trackway of very small, functionally tridactyl tracks near Storm Shelter (Eastern Cape) in South Africa, the track record can be expanded. Based on ichnological measurements at the ichnosite and digital 3D models, the footprint dimensions (length, width, splay), locomotor parameters (step length, stride, speed), and body size estimates of the trackmaker are presented. In comparison to other similar tracks, these footprints are not only the smallest Grallator-like tracks in the Clarens Formation, but also the most elongated dinosaur footprints in southern Africa to date. The tracks also show that the small-bodied bipedal trackmaker dashed across the wet sediment surface at an estimated running speed of ~12.5 km/h. During the dash, either as a predator or as a prey, the trackmaker’s small feet sunk hallux-deep into the sediment. The tracking surface is overgrown by fossilised microbial mats, which likely enhanced the footprint preservation. Based on track morphometrics and the regional dinosaur skeletal record, the trackmakers are attributed to Megapnosaurus rhodesiensis (formerly Syntarsus rhodesiensis), a small-to-medium-sized, early theropod common in southern Africa.

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“…Track quantification, using modern ichnological standards (Falkingham et al, 2018) has been executed since 2015 (e.g., Sciscio et al, 2016Sciscio et al, , 2017Abrahams et al, 2017Abrahams et al, , 2020aBordy et al, 2017;Abrahams, 2020;Bordy, 2021). This study assumes that the tridactyl tracks reviewed herein have correctly been assigned to Kayentapus, Grallator, and Eubrontes by these authors.…”

Section: Methodsmentioning

confidence: 99%

“…Assessing the morphology of fossil tracks is important for ichnology, as it is the root of ichnotaxonomy and in turn, critical for inferences on paleodiversity, paleoecology and paleoethology (e.g., Farlow et al, 2018;Lallensack et al, 2019). Recent technological advances in 3D photogrammetric modeling and geometric morphometric landmark-based principal component analysis have shifted trackbased studies from primarily descriptive to quantitative (e.g., Weems, 1992;Olsen et al, 1998;Dalman and Weems, 2013;Razzolini et al, 2014;Castanera et al, 2015Castanera et al, , 2016Lallensack et al, 2016Lallensack et al, , 2019Wings et al, 2016;Belvedere et al, 2018;Falkingham et al, 2018;Farlow et al, 2018;Abrahams et al, 2020a). Statistical studies, incorporating extensive dinosaur track databases, have successfully been used to refine ichnotaxonomic assignment by accounting for morphological variability, distinguish between tridactyl theropod and ornithopod tracks, and better understand pedal function.…”

Section: Introductionmentioning

confidence: 99%

“…Although the exact placement of the Triassic-Jurassic boundary within the upper Stormberg Group is unknown, recent radiometric dating suggests a Norian-Rhaetian age for the lower Elliot Formation (lEF), a Hettangian to Sinemurian age for the upper Elliot Formation (uEF) and a Sinemurian to Pliensbachian age for the Clarens Formation (Figure 1; Bordy et al, 2020). Upper Stormberg Group vertebrate tracks, attributed to dinosaurs, have been known since in the 1800s (Dieterlen, 1885) and formally documented since the early 1900s (Dornan, 1908) with a boom in systematic documentation in the second half of the 20th century and post-2015 (e.g., Ellenberger, 1955Ellenberger, , 1970Ellenberger, , 1972Ellenberger, , 1974Ellenberger and Ellenberger, 1956, 1958, 1960Ellenberger et al, 1963;Ambrose, 2003;Raath and Yates, 2005;Smith et al, 2009;Sciscio et al, 2016Sciscio et al, , 2017Abrahams et al, 2017Abrahams et al, , 2020aBordy et al, 2017;Rampersadh et al, 2018;Bordy, 2021). Like many other early Mesozoic vertebrate ichnoassemblages attributed to dinosaurs (e.g., Petti et al, 2008;Belvedere et al, 2010;Moreno et al, 2012;Lockley et al, 2013;Läng et al, 2013;Pérez-Lorente, 2015;D'Orazi Porchetti et al, 2016;Xing et al, 2020), the upper Stormberg Group dinosaur track record comprises tracks primarily assigned to Kayentapus, Grallator, Anchisauripus, and Eubrontes.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2022

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The end-Triassic mass extinction events mark a pivotal period in archosaur history, and have been proposed to contribute to the rise and dominance of dinosaurs throughout the Mesozoic. In southern Africa, the Triassic–Jurassic boundary is contained within the richly fossiliferous fluvio-lacustrine-aeolian deposits of the upper Stormberg Group in the main Karoo Basin. Due to an absence of high-resolution radioisotopic age constraints, the exact placement of the boundary remains difficult. The Stormberg Group theropod osteological record is limited to scarce, fragmentary material; therefore, the abundant Norian–Pliensbachian tridactyl tracks attributed to theropods are vital for unraveling theropod dinosaur evolutionary trends in southwestern Gondwana. This study considers over 200 upper Stormberg Group tridactyl tracks assigned to the Kayentapus-Grallator-Anchisauripus-Eubrontes (K-GAE) plexus, to quantify their morphological variation across a time span of ∼35 million years. Our findings show that within the upper Stormberg Group, and across the Triassic–Jurassic boundary, the younger tracks become larger, have a decreased mesaxony and a reduced digit III projection. This reduced emphasis of the medial digit is also observed across the K-GAE plexus, and for the individual ichnotaxa across time in the main Karoo Basin, e.g., Eubrontes tracks become less mesaxonic and have a reduced digit III projection higher up in the stratigraphy. This suggests that these morphological trends are not simply linked to size but may reflect a change in autopod morphology through time, which has implications for pedal functionality. Furthermore, being morphologically distinct from contemporaneous North American K-GAE tracks (e.g., reduced elongation and mesaxony, no correlation between digit divarication angles and size), these southern African footprints warrant further investigation.

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Hidden for one hundred years: a diverse theropod ichnoassemblage and cross-sectional tracks from the historic Early Jurassic Tsikoane ichnosite (Clarens Formation, northern Lesotho, southern Africa)

Cited by 13 publications

References 74 publications

Lake dynamics in an Early Jurassic desert: Evidence from the Clarens Formation in southern Africa

Lake dynamics in an Early Jurassic desert: Evidence from the Clarens Formation in southern Africa

Darting towards Storm Shelter: A minute dinosaur trackway from southern Africa

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

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