Sauropodomorph dinosaur trackways from the Fleming Fjord Formation of East Greenland: Evidence for Late Triassic sauropods JENS N. LALLENSACK, HENDRIK KLEIN, JESPER MILÀN, OLIVER WINGS, OCTÁVIO MATEUS, and LARS B. CLEMMENSEN Lallensack, J.N., Klein, H., Milán, J., Wings, O., Mateus, O., and Clemmensen, L.B. 2017. Sauropodomorph dinosaur trackways from the Fleming Fjord Formation of East Greenland: Evidence for Late Triassic sauropods. Acta Palaeonto- logica Polonica 62 (4): 833–843. The Late Triassic (Norian–early Rhaetian) Fleming Fjord Formation of central East Greenland preserves a diverse fossil fauna, including both body and trace fossils. Trackways of large quadrupedal archosaurs, although already reported in 1994 and mentioned in subsequent publications, are here described and figured in detail for the first time, based on photogrammetric data collected during fieldwork in 2012. Two trackways can be referred to Eosauropus, while a third, bipedal trackway may be referred to Evazoum, both of which have been considered to represent sauropodomorph dinosaur tracks. Both the Evazoum and the Eosauropus trackways are distinctly larger than other trackways referred to the respective ichnogenera. The trackmaker of the best preserved Eosauropus trackway is constrained using a synapo- morphy-based approach. The quadrupedal posture, the entaxonic pes structure, and five weight-bearing digits indicate a derived sauropodiform trackmaker. Other features exhibited by the tracks, including the semi-digitigrade pes and the laterally deflected unguals, are commonly considered synapomorphies of more exclusive clades within Sauropoda. The present trackway documents an early acquisition of a eusauropod-like pes anatomy while retaining a well-developed claw on pedal digit IV, which is reduced in eusauropods. Although unequivocal evidence for sauropod dinosaurs is no older than the Early Jurassic, the present trackway provides evidence for a possible Triassic origin of the group. Key words: Dinosauria, Sauropodomorpha, trackway, Triassic, Greenland. Jens N. Lallensack [[email protected]], Steinmann-Institut für Geologie, Mineralogie und Paläontologie, Rheinische Friedrichs-Wilhelm Universität Bonn, Nußallee 8, 53115 Bonn, Germany. Hendrik Klein [[email protected]], Saurierwelt Paläontologisches Museum, Alte Richt 7, D-92318 Neu- markt, Germany. Jesper Milàn [[email protected]], Geomuseum Faxe/Østsjællands Museum. Østervej 2, DK-4640 Faxe, Denmark, and Natural History Museum of Denmark, Øster Voldgade 5-7, DK-1350 Copenhagen, Denmark. Oliver Wings [[email protected]], Zentralmagazin Naturwissenschaftlicher Sammlungen (ZNS), Martin-Luther-Uni- versität Halle-Wittenberg, Domplatz 4, 06108 Halle (Saale), Germany. Octávio Mateus [[email protected]], GEOBIOTEC, Faculdade de Ciências e Tecnologia, FCT, Universidade Nova de Lisboa, 2829-526 Caparica, Portuga, and Museu da Lourinhã, Rua João Luís de Moura, 2530-157 Lourinhã, Portugal. Lars B. Clemmensen [[email protected]], Department of Geosciences and Natural Resource Management, University of Copenhagen, Øster Voldgade 10, DK-1350 Copenhagen, Denmark. Received 21 April 2017, accepted 28 June 2017, available online 4 September 2017. Copyright © 2017 J.N. Lallensack et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License (for details please see http://creativecommons.org/licenses/by/4.0/), which permits unre- stricted use, distribution, and reproduction in any medium, provided the original author and source are credited. fossil within the Jurassic (Racey and Goodall 2009; McPhee Introduction et al. 2015). The sauropod status of Late Triassic forms The Triassic body fossil record of sauropods is extremely such as Antetonitrus is unclear, given current disagree- poor. Although Isanosaurus from the Nam Phong Formation ments on the taxonomic definition of Sauropoda (McPhee of Thailand had been described as the oldest known sauro- et al. 2014). Thus, undisputed evidence for Sauropoda pod (Buffetaut et al. 2000), its proposed late Norian or sensu stricto from the Triassic is currently lacking, with Rhaetian age was recently questioned, possibly placing the some authors arguing that sauropods diverged from other Acta Palaeontol. Pol. 62 (4): 833–843, 2017 https://doi.org/10.4202/app.00374.2017 834 ACTA PALAEONTOLOGICA POLONICA 62 (4), 2017 sauropodomorphs as late as close to the Triassic–Jurassic mammaliaforms, possible sphenodonts and lepidosaurs, boundary (McPhee et al. 2015). testudinatans, phytosaurs, aetosaurs, a possible rauisu- Jenkins et al. (1994) briefly mentioned the occurrence chian, pterosaurs, and dinosaurs (theropods and basal sau- of three large, quadrupedal trackways referable to large ropodomorphs), while the ichnofauna includes a large num- archosaurs from the Late Triassic (Norian–Rhaetian) ber of theropod-like (Grallator), sauropodomorph-like, and Fleming Fjord Formation of East Greenland. The best pre- stem-crocodylian archosaur trackways (Sulej et al. 2014; served of these trackways (herein, trackway S1) was noted Clemmensen et al. 2016; Klein et al. 2016). The three sau- to show “four clawed digits, oriented anterolaterally” and ropodomorph-like trackways described herein come from “small, crescentic impressions of the manus” (Jenkins et the Track Mountain locality at Wood Bjerg-Macknight Bjerg al. 1994: 19), and included in a sitemap showing its posi- (Fig. 1) along Carlsberg Fjord near the eastern margin of the tion amongst multiple smaller, bipedal trackways referred basin (Clemmensen et al. 2016). Trackway S1 (71°24.853’ N, to the ichnogenus Grallator. These large trackways were 22°33.322’ W; 534 m above sea level) and trackway S2 frequently mentioned in subsequent literature, but have (71°24.955’ N, 22°32.952’ W) represent quadrupedal track- never been described or illustrated in detail. Lockley and ways, while trackway S3 (71°24.857’ N, 22°33.334’ W) is Meyer (2000) suggested that these tracks are attributable bipedal. The tracks are preserved as concave epireliefs on a to basal sauropodomorph (“prosauropod”) dinosaurs, and thin, laterally extensive siltstone bed that is under- and over- possibly to the ichnogenus Tetrasauropus. Lockley et al. lain by red mudstone. The siltstone bed has a thickness be- (2001, 2006a) mention that the trackways might be those of tween 1 and 5 cm, is multistorey and contains wave-formed sauropod trackmakers, with Lockley et al. (2006a) stating structures including even lamination and tiny wave ripples. that the tracks are similar to those referred to the ichno- The upper surface is cut by polygonal mudcracks and re- genus Eosauropus. Fieldwork carried out in 2012 was able veals micro-ridges of uncertain origin. Tridactyl Grallator to relocate two of the three trackways (Sulej et al. 2014; tracks are seen locally in close association with the sau- Clemmensen et al. 2016). The better-preserved trackway ropodomorph-like tracks. Selected high-resolution photo- was identified as that of a biped with “rounded pes and graphs showing the described trackways in the field are weak indications of outwards-rotated claws”, and “a weak provided as SOM 1 (Supplementary Online Material avail- impression that could indicate the presence of a thin semi- able at http://app.pan.pl/SOM/app62-Lallensack_etal_SOM. lunate-shaped manus” (Clemmensen et al. 2016: 43). A sec- pdf). During Late Triassic times, the study area was located ond trackway, “quadrupedal, with an extreme degree of at the northern rim of the Pangaean supercontinent at about heteropody” and elongated pes imprints (Clemmensen et al. 40 ͦ N (Clemmensen et al. 2016). The track-bearing siltstone 2016: 43), was ascribed to a different type. A newly discov- bed is situated in the lowermost part of the Tait Bjerg Beds of ered third trackway showing tetradactyl pes prints was re- the Ørsted Dal Member within the Fleming Fjord Formation ferred to cf. Evazoum, suggesting a basal sauropodomorph (Clemmensen et al. 1998, 2016). The Ørsted Dal Member trackmaker (Sulej et al. 2014; Clemmensen et al. 2016). has been dated to the late Norian–early Rhaetian, based on Klein et al. (2016) noted that, given the lack of a complete invertebrate fossils, land-derived palynomorphs, and pa- description and detailed figures, it cannot be excluded that leomagnetic data; the track-bearing bed probably formed these tracks might not belong to dinosaurs but to large chi- around 208 mya (Clemmensen 1980; Kent and Clemmensen rotheriids. The purpose of the present paper is to describe 1996; Clemmensen et al. 1998, 2016). The track-bearing part these trackways in detail for the first time. In light of a of the succession was deposited in an ephemeral to semi-pe- possible sauropod affinity of the quadrupedal trackways, rennial lake with annual and longer-term fluctuations in footprint features are compared with skeletal features of lake water. The siltstone bed records flooding events of sauropodomorphs, allowing for trackmaker identification mudflats by lake water (Clemmensen et al. 1998). based on synapomorphies, and possibly providing addi- tional data on the poorly known early evolutionary history of sauropods. Material and methods Other abbreviations.—LM, left manus; LP, left pes; PL, pes The three trackways described herein (S1, S2, S3) were found length; RM, right manus; RP, right pes; WAP, width of the in close proximity to each other (Fig. 1C). Descriptions and angulation pattern. measurements are based on high-resolution photogrammet- ric 3D-models generated