Downloaded from http://sp.lyellcollection.org/ by guest on September 30, 2021 The theropod that wasn’t: an ornithopod tracksite from the Helvetiafjellet Formation (Lower Cretaceous) of Boltodden, Svalbard JØRN H. HURUM1,2, PATRICK S. DRUCKENMILLER3, ØYVIND HAMMER1*, HANS A. NAKREM1 & SNORRE OLAUSSEN2 1Natural History Museum, University of Oslo, PO Box 1172, Blindern, 0318 Oslo, Norway 2The University Centre in Svalbard (UNIS), PO Box 156, 9171 Longyearbyen, Norway 3Department of Geosciences, University of Alaska Museum, University of Alaska Fairbanks, 907 Yukon Drive, Fairbanks, AK 99775, USA *Corresponding author (e-mail: [email protected]) Abstract: We re-examine a Lower Cretaceous dinosaur tracksite at Boltodden in the Kvalva˚gen area, on the east coast of Spitsbergen, Svalbard. The tracks are preserved in the Helvetiafjellet For- mation (Barremian). A sedimentological characterization of the site indicates that the tracks formed on a beach/margin of a lake or interdistributary bay, and were preserved by flooding. In addition to the two imprints already known from the site, we describe at least 34 additional, pre- viously unrecognized pes and manus prints, including one trackway. Two pes morphotypes and one manus morphotype are recognized. Given the range of morphological variation and the pres- ence of manus tracks, we reinterpret all the prints as being from an ornithopod rather than a thero- pod, as previously described. We assign the smaller (morphotype A, pes; morphotype B, manus) to Caririchnium billsarjeanti. The larger (morphotype C, pes) track is assigned to Caririchnium sp., differing in size and interdigital angle from the two described ichnospecies C. burreyi and C. bill- sarjeanti. The occurrence of a quadrupedal, small to medium-sized ornithopod in Svalbard is puz- zling, considering the current palaeogeographical reconstructions and that such dinosaur tracks have mainly been described from Europe but not North America. Gold Open Access: This article is published under the terms of the CC-BY 3.0 license. Globally, only a small number of sites preserve Boltodden in the Kvalva˚gen area (Fig. 1), which evidence of dinosaurs that lived at polar latitudes. were described as belonging to a medium-sized In the Arctic, skeletal remains and footprints of theropod by Edwards et al. (1978). In 2012 and Jurassic and Cretaceous dinosaurs are known from 2014, we revisited the Boltodden site and, during Alaska, Canada, Siberia and Svalbard (Gangloff the course of our field investigations, discovered 2012). The first indisputable evidence that dinosaurs numerous other individual footprints and at least inhabited the palaeo-Arctic was discovered in 1960 one trackway. Based on pes morphology and the at Festningen, in western Spitsbergen, Svalbard. presence of several manus imprints, we interpret These discoveries consist of ornithopod dinosaur the new finds, as well as two previously described tracks in a Lower Cretaceous (Barremian–Aptian) tracks, as being made by an ornithopod and not a sandstone unit of the Helvetiafjellet Formation theropod. Here, we describe the new tracks and (Lapparent 1960, 1962). New tracks were subse- also provide, for the first time, a detailed palaeo- quently discovered when the same locality was environmental context for the site. revisited in the early 2000s (Hurum et al. 2006). Ornithopod ichnotaxonomy has been in a state of Other Spitsbergen dinosaur tracks from the same flux. Of large ornithopod ichnotaxa, eight Barre- formation were also reported at Hanaskogdalen mian and nine Aptian ichnogenera have been and Ullaberget, in the doctoral work of Ivar Mid- described worldwide (Dı´az-Martı´nez et al. 2015). tkandal (Midtkandal et al. 2007), and at Olsokneset, In their recent review of large ornithopod dinosaur described in a popular paper by Smelror et al. tracks, Dı´az-Martı´nez et al. (2015) only considered (2006). three genera valid. Iguanodontipus in the Berria- In 1976, two tracks were discovered in east- sian–Valanginian, Caririchnium in the Berria- ern Spitsbergen in the Helvetiafjellet Formation at sian–Albian and, finally, Hadrosauropodus in the From:Kear, B. P., Lindgren, J., Hurum, J. H., Mila`n,J.&Vajda, V. (eds) Mesozoic Biotas of Scandinavia and its Arctic Territories. Geological Society, London, Special Publications, 434, http://doi.org/10.1144/SP434.10 # 2016 The Author(s). Published by The Geological Society of London. Publishing disclaimer: www.geolsoc.org.uk/pub_ethics Downloaded from http://sp.lyellcollection.org/ by guest on September 30, 2021 J. H. HURUM ET AL. (a)(b) 50 80° Kvalhovddalen 100 Nordaustlandet 100 Kval- hovden 79° 344 Ny-Ålesund Spitsbergen Hanaskogdalen TS 78° Festningen TS Longyearbyen Edgeøya Ullaberget TS Boltodden TS 77° Svalbard TS Olsokneset TS Sporodden Boltodden 100 km 500 m Fig. 1. (a) Map of Svalbard showing the study area at Boltodden in the Kvalva˚gen area and other tracksites (TS) described from Spitsbergen. Outcrops of the Adventdalen Group (Jurassic–Cretaceous) are shown in a darker shade (simplified: cf. Dallmann et al. 2002). (b) The Boltodden tracksite and the Kvalhovden stratigraphic reference site. Aptian–Maastrichtian. From this review, it follows Glørstad-Clark et al. 2010). Although these areas that all large ornithopod tracks from the Barremian experienced no major extensional or compression are of the genus Caririchnium. Four ichnospecies tectonics, the deposition of the Mesozoic basin fill of Caririchnium are known (Dı´az-Martı´nez et al. was controlled by faulting, halokenesis in some 2015): C. magnificum is found in Berrasian–Albian- basins, volcanism, and the vertical movement and aged deposits of Brazil and Spain; C. kortmeyeri is tilting of major structural elements (Steel & Wors- only known from the Aptian–Albian of Canada; ley 1984; Grogan et al. 1999, 2000; Glørstad-Clark C. billsarjeanti is from the Aptian of Switzerland; et al. 2010; Anell et al. 2014; Senger et al. 2014). and C. lotus is known from the Barremian–Albian The nearly 2 km-thick Middle Jurassic–Early of China and Spain (for a discussion, see Dı´az-Mar- Cretaceous Adventdalen Group is dominated by tı´nez et al. 2015). In the Aptian, only one Hadro- mudstone and heterolithic fine-grained sandstone– sauropodus species is known, H. kyoungsookimi, mudstone (Steel & Worsley 1984; Mørk et al. which is found in Korea. 1999). The Adventdalen Group is subdivided into four formations (Mørk et al. 1999). The Batho- nian–Valanginian Agardhfjellet Formation, like its Geological setting offshore counterparts in the Barents Sea, the Fuglen and Hekkingen formations, was deposited under The Barents Sea platform and its exposed part, Sval- conditions with a low sediment supply and periodic bard, are located on the NW corner of the Eurasian high organic production in an inner- to outer-shelf continental plate (Fig. 1). In the Early Cretaceous, environment (Dypvik et al. 1991). The overlying Svalbard was situated at 63–668 N (Torsvik et al. Valanginian–Hauterivian Rurikfjellet Formation 2012). The Mesozoic basin fill in the western mar- consists of inner-shelf mudstone passing upwards gin of the Barents Platform was deposited within into prodelta/lower shoreface/distal delta-front the Mesozoic Atlantic rift system (Faleide et al. environments and defines a large-scale regressive 2008). In contrast, the Triassic–Lower Cretaceous unit (Gjelberg & Steel 1995). The overlying Helve- basin fill in Svalbard and the western platform tiafjellet Formation, in which the dinosaur tracks are areas were deposited in a subsiding epicontinental found, is a sandstone-dominated Barremian–early sag basin (Steel & Worsley 1984; Faleide et al. Aptian unit, up to 155 m thick. It was deposited 2008; Worsley 2008; Midtkandal & Nystuen 2009; in fluvial, deltaic, tidal and paralic environments Downloaded from http://sp.lyellcollection.org/ by guest on September 30, 2021 AN ORNITHOPOD TRACKSITE IN SVALBARD (Gjelberg & Steel 1995; Midtkandal & Nystuen boundary (Midtkandal & Nystuen 2009). The for- 2009). Finally, the uppermost formation of the mation thickens towards the south and SE (Parker group is the Aptian–Albian Carolinefjellet Forma- 1967), without any systematic change in the amount tion, which is more than 1200 m thick and consists of marine facies associations (Gjelberg & Steel of shallow shelf sandstones and offshore mudstones 1995). This suggests higher accommodation space with scattered carbonate beds (Maher et al. 2004). to the south and SE. The formation was sourced In the Early Cretaceous, the sediment source from the NW and had the main drainage system ori- area in Svalbard and the western Barents Sea was entated towards the SE (Gjelberg & Steel 1995; towards the north or NW (Steel & Worsley 1984; Midtkandal & Nystuen 2009). Although biostrati- Gjelberg & Steel 1995; Midtkandal & Nystuen graphic resolution is poor, the interpreted incised 2009). This drainage pattern is linked to the opening valley fill and aggrading nature of the lower part of the Amerasian Basin (Lawver et al. 2002; of the formation (Nemec 1992; Gjelberg & Steel Golonka et al. 2003; Do¨rr et al. 2012) and associated 1995; Midtkandal & Nystuen 2009) suggest near- volcanism (Senger et al. 2014 and references chronostratigraphic correlation between eastern therein). The sudden influx (i.e. forced regression: and western Spitsbergen. Gjelberg & Steel 1995) of the SE-directed fluvio- The dinosaur tracks at Boltodden are situated deltaic Helvetiafjellet Formation above the distal in the lower part of the Helvetiafjellet Formation clastic