# First record of Lagarodus (Chondrichthyes: Euchondrocephali) from the Carboniferous of Svalbard, Arctic Norway

Gilles Cuny, Jakob Bruun Kristensen, Lars Stemmerik

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Gilles Cuny, Jakob Bruun Kristensen, Lars Stemmerik. First record of Lagarodus (Chondrichthyes: Euchondrocephali) from the Carboniferous of Svalbard, Arctic Norway. Norwegian Journal of Geology, 2016, 96 (1), pp.1-5. 10.17850/njg96-1-01. hal-02331970

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# First record of *Lagarodus* (Chondrichthyes: Euchondrocephali) from the Carboniferous of Svalbard, Arctic Norway

Gilles Cuny<fnref n="1" />,<fnref n="2" />, Jakob Bruun Kristensen<fnref n="3" />,<fnref n="4" /> & Lars Stemmerik<fnref n="3" />,<fnref n="4" />

E-mail corresponding author (Gilles Cuny): gilles.cuny@univ-lyon1.fr

The rather enigmatic genus *Lagarodus* is reported for the first time from the Bashkirian of Svalbard. *Lagarodus* first appeared in the equatorial region during the Tournaisian and then extended its geographical distribution to the intertropical zone around the Euramerican continent. The Svalbard discovery hints at the possibility that the northern species was different from the southern one.

Keywords: *Lagarodus*, Svalbard, Bashkirian, carbonate platform

Received 24. September / Accepted 13. November / Published online 18. December 2015

## Introduction

This paper documents the first occurrence of Chondrichthyan fishes from the Mid Carboniferous of Spitsbergen, Arctic Norway. A single tooth belonging to the genus *Lagarodus* was found in the middle to late Bashkirian Trikolorfjellet Member of the Ebbadalen Formation. It adds to our knowledge of the geographic and stratigraphic distribution of *Lagarodus* which was hitherto known from the Moscow region in Russia, Ohio, Colorado, Arizona, Kansas and New Mexico in the US, North Greenland and Belgium (Stahl, 1999; Elliott et al., 2004; Hamm & Cicimurri, 2005), and confirms the connection from Spitsbergen and eastwards to the open marine platform areas of the Timan-Pechora Basin and Novaya Zemlya in Arctic Russia (e.g., Stemmerik, 2000). Its occurrence also indicates a temporary presence of fully marine conditions during Bashkirian rifting in Svalbard and the adjacent Norwegian Barents Sea.

*Institutional abbreviations.* NHMUK – Natural History Museum, London, NHMD-VP – Natural History Museum of Denmark, collection of vertebrate palaeontology.

## Setting and stratigraphy

During Late Palaeozoic times Svalbard formed part of a huge E-W-oriented shelf along the northern margin of Pangea. It was located around 35°N during the Bashkirian (Golonka & Ford, 2000), and from the Bashkirian to Sakmarian deposition took place in a warm and arid climate (e.g., Johannessen & Steel, 1992; Beauchamp, 1994; Stemmerik, 2000).

The western part of the shelf was affected by rifting during the early Bashkirian and several NNW-SSE-

<footnote n="1">¹The Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5-7, DK-1350 Copenhagen K, Denmark.</footnote>

<footnote n="2">²Present address: LGLTPE, UMR CNRS ENS 5276, Université Claude Bernard Lyon 1, Campus de la Doua, Bâtiment Géode, 2, rue Raphaël Dubois, F-69622 Villeurbanne Cedex, France.</footnote>

<footnote n="3">³The Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5-7, DK-1350 Copenhagen K, Denmark.</footnote>

<footnote n="4">⁴University Centre in Svalbard, P.O. Box 156, N-9171, Longyearbyen, Norway.</footnote>
oriented half-grabens started to form in the western Barents Sea and on Spitsbergen (Steel & Worsley, 1984). Initial deposition was non-marine, but the half-grabens were gradually transgressed during the Bashkirian and by Moscovian times most of the shelf formed a mosaic of open marine carbonate platforms (Larssen et al., 2005). The investigated specimen is from the uppermost carbonate bed in the Trikolorfjellet Member, Ebbadalen Formation, at western De Geerfjellet (N 78° 41'/E 16° 45'), central Spitsbergen (Fig. 1). The Trikolorfjellet Member forms an up to 200 m-thick unit of interbedded gypsum and carbonates with minor siliciclastics believed to reflect deposition in sabkha and marginal marine environments (Johannessen & Steel, 1992). The recorded specimen (Fig. 2) is from a 2 m-thick biogenic

wackestone with more grain-rich layers dominated by crinoids and other echinoderms. The fauna also includes fragments of brachiopods, gastropods and bony fish. The bony fish are represented by two tooth morphotypes (Fig. 3), which cannot be identified beyond the actinopterygian level.

The upper Trikolorfjellet Member is of middle to late Bashkirian age based on the presence of a microbiota of fusulinid, endothyrid and archadiscid foraminifers in carbonate beds immediately below and above (Cutbill & Challinor, 1965; Mamet et al., 1993). It forms the upper part of the Bashkirian syn-rift succession in central Spitsbergen and is limited to the Billefjorden Trough (Fig. 1).

<figure><img src="image_2.png" /><figcaption>**Figure 1.** (A) Map of northern Billefjorden, central Spitsbergen, with outcrops of the Ebbadalen Formation highlighted in green. The arrow north of Adolfbukta is showing the location of the investigated material. (B) Distribution of outcrops of Upper Carboniferous-Permian sedimentary rocks in Svalbard. Major faults are indicated. (C) Pre-drift position of Spitsbergen, north of Greenland. The arrows show the locations of the Spitsbergen and Greenland specimens mentioned in the text.</figcaption></figure>
<figure><img src="image_3.png" /><figcaption>Figure 2. Lateral tooth of *Lagarodus* sp. (NHMD-VP-9518) in (A) apical, (B) lingual, (C) basal and (D) labial views. Scale bar: 15 mm.</figcaption></figure>

## Systematic Palaeontology

Class Chondrichthyes Huxley, 1880

Subclass Euchondrocephali Lund & Grogan, 1997

Order indet.

Family Lagarodontidae Lebedev, 2008
Genus *Lagarodus* Jaekel, 1898

*Lagarodus* sp.

NHMD-VP-9518 measures 18 mm mesio-distally, 6 mm labio-lingually and 7 mm apico-basally (Fig. 2). The crown is slightly twisted labio-lingually and S-shaped in apical view, the lingual side being mainly concave and the labial one mainly convex. Most of the enameloid cover has been worn off, and the apical surface of the crown shows a dense network of circular depressions corresponding to the openings of the dentinal canals of the tubular dentine (orthotrabeculine). Some concentric ridges are preserved on the mesial and distal extremities, as well as on part of the labial border, where the enameloid has been preserved. The lingual face of the crown is almost vertical and is ornamented by irregular, anastomosed ridges oriented mesio-distally. The labial face is inclined and overhangs the root. Its enameloid cover is not preserved. It is separated from the root by a constriction, which is also seen on the mesial and distal sides. It disappears on the lingual side.

The base is quadrangular and slightly twisted labio-lingually like the crown. Lingually, it is almost as thick as the crown, but labially the crown is thicker than the base. Its vascularisation is anaulacorhize, with small foramina

scattered over the labial, lingual, mesial and distal faces. On the mesial side, the base forms an angle with the crown, whereas on the distal one, it is in continuation with the crown.

## Discussion

The crown is made of orthotrabeculine and the thick enameloid cover of at least its mesial and lingual sides are characters typical of the family Lagarodontidae (Lebedev, 2008). This family is exclusively known from isolated teeth and its phylogenetic relationships among enchondrocephals are poorly understood. It is currently monogeneric and monospecific (Lebedev, 2008). The twisted shape of NHMD-VP-9518 matches that of the lateral teeth of *Lagarodus specularis* from the Moscovian-Kasimovian of Russia, a senior synonym of *Lagarodus angustus* (Lebedev, 2008), although the teeth of the latter species possess straighter labial and lingual margins of the crown than NHMD-VP-9518 (Hansen, 1986; Zidek & Kietzke, 1993; Elliott et al., 2004; Hamm & Cicimurri, 2005; Lebedev, 2008). It suggests that NHMD-VP-9518 belongs to a different species, but a single lateral tooth does not represent sufficient material to erect a new species. The tooth described from the upper Moscovian *Wedekindellina* zone of Greenland as *Lagarodus* sp. (Bendix-Almgreen, 1975) is an incomplete parasymphysial one, such that a meaningful comparison with NHMD-VP-9518 is not possible.

NHMD-VP-9518 shares with NHMUK P63892 a rather elongated shape mesio-distally, a labio-lingually twisted crown and a similar ornamentation of the non-occlusal parts of the crown (Stahl, 1999, fig. 86H). The provenance of NHMUK P63892 was given by Stahl (1999) as: Lower Carboniferous, British Isles. However, a check
<figure><img src="image_4.png" /><figcaption>**Figure 3.** *Actinopterygian tooth morphotypes. (A-B) Morphotype A (NHMD-VP-9519) in (A) lateral and (B) apical views. (C-D) Bone fragment bearing six teeth of morphotype B (NHMD-VP-9520) in (C) apical and (D) lateral views. Scale bars: 100 µm*</figcaption></figure>

in the original register at the Natural History Museum, London gives: ?*Psammodus* sp. from the Moscovian of Mjatschkova, Russia (M. Richter, pers. comm., 2014). As the Myachkovo quarry is the locality where the neotype of *Lagarodus specularis* comes from (Lebedev, 2008), it is likely that NHMUK P63892 in fact represents a lateral (*specularis* morphotype) tooth of *Lagarodus*.

The investigated material is older than the mid-
continent faunas of the US which are of late Atokan
– Desmoinesian age and older than the Greenland
fauna described by Bendix-Almgreen (1975) since later
biostratigraphic work has shown that the Greenland
fauna is of Moscovian age (Davydov et al., 2001). As
the record of *Lagarodus* in the Lower Carboniferous of
Russia now appears doubtful (Lebedev, 2008), the oldest
record of this genus is from the Tournaisian of Belgium
(De Koninck, 1878; Hansen, 1986), which would anyway
suggest that this genus appeared in the equatorial region.
However, De Koninck (1878) provided a rather crude
description and illustration of the Belgian tooth so that
its precise phylogenetic affinities are quite difficult to
decipher. Its convex labial margin in apical view is quite
similar to that of NHM-D-VP-9518, but its lingual
margin is much straighter. The Belgian tooth appears also
quite unusual as it seems that there are well-developed
nodes at the base of the lingual face (De Koninck, 1878,
fig. 6b). Anyway, the species *L. specularis* is thereafter
known from the equatorial region in Russia during the
Moscovian and Kasimovian (Lebedev, 2008) and in the
southern tropical region in North America during the
Moscovian (Elliott et al., 2004; Hamm & Cicimurri,

2005). Its record in the northern tropical region in the
Bashkirian of Svalbard and the Moscovian of Greenland
(Bendix-Almgreen, 1975) is still patchy, but the tooth
described here from Svalbard might suggest that the
northern species was different from the southern one.

Conclusion

The discovery of *Lagarodus* in Svalbard adds to its
range and distribution. It was restricted to the coast of
the Euroamerican continent and the vast majority of
the finds are in mid-latitude areas with warm and arid
climate. Data concerning *Lagarodus* are still patchy, but
they suggest that the genus appeared in the equatorial
region during the Tournaisian and then extended its
geographical distribution to the intertropical zone
around the Euramerican continent. The Svalbard
discovery hints at the possibility that the northern
species was different from the southern one.

*Acknowledgements.* We would like to thank Snorre Olaussen (UNIS) for organising the field work, Martha Richter (Natural History Museum, London) for her help with NHMUK P63892 and Wayne Itano (University of Colorado) for his help with the *Lagarodus* fossil record of the United States as well as for providing us, together with Jürgen Polerspöck, with hard-to-find bibliography. We welcomed comments from Michal Ginter and Hans Arne Nakrem, which helped us to improve the manuscript. Fieldwork was supported by the University Centre in Svalbard (UNIS), Lundin Norway AS and Det norske oljeselskap ASA.
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