Alcheringa: An Australasian Journal of Palaeontology

ISSN: 0311-5518 (Print) 1752-0754 (Online) Journal homepage: https://www.tandfonline.com/loi/talc20

First record of (, Mosasauridae) from the uppermost of Stevns Klint, Denmark

Jesper Milàn, John W.M. Jagt, Johan Lindgren & Anne S. Schulp

To cite this article: Jesper Milàn, John W.M. Jagt, Johan Lindgren & Anne S. Schulp (2018) First record of Carinodens (Squamata, Mosasauridae) from the uppermost Maastrichtian of Stevns Klint, Denmark, Alcheringa: An Australasian Journal of Palaeontology, 42:4, 597-602, DOI: 10.1080/03115518.2017.1391878 To link to this article: https://doi.org/10.1080/03115518.2017.1391878

Published online: 29 Nov 2017.

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Full Terms & Conditions of access and use can be found at https://www.tandfonline.com/action/journalInformation?journalCode=talc20 First record of Carinodens (Squamata, Mosasauridae) from the uppermost Maastrichtian of Stevns Klint, Denmark

JESPER MILÀN , JOHN W.M. JAGT, JOHAN LINDGREN and ANNE S. SCHULP

MILÀN, J., JAGT, J.W.M., LINDGREN,J.&SCHULP, A.S., November 2017. First record of Carinodens (Squamata, Mosasauridae) from the uppermost Maastrichtian of Stevns Klint, Denmark. Alcheringa 42, 597–602. ISSN 0311-5518.

Here we report on an important addition to the Late fossil record of marine from Denmark: a crown of the rare duropha- gous Carinodens minalmamar found in the uppermost Maastrichtian strata at the UNESCO World Heritage Site Stevns Klint. The tooth was found within the uppermost few metres of the Maastrichtian chalk placing it within the latest 50.000 years prior to the K/Pg boundary. The new find is a shed crown probably representing a tooth from the 11th to 13th position in the . The tooth represents the northernmost occurrence of the Carinodens. Previous mosasaur finds from Denmark have all been from the hypercarnivorous mosasaurids hoffmannii and Plio- sp., thus our specimen adds a new trophic niche exploited by marine tetrapods in the food web of the latest Maastrichtian of Denmark.

Jesper Milàn* [[email protected]], Geomuseum Faxe/Østsjællands Museum, Østervej 2, 4640 Faxe, Denmark; John W.M. Jagt [john.jagt@maas- tricht.nl], Natuurhistorisch Museum Maastricht, De Bosquetplein 6–7, 6211 kJ Maastricht, the Netherlands; Johan Lindgren [johan.lindgren@- geol.lu.se], Department of Geology, Lund University, Sölvegatan 12, 223 62 Lund, Sweden. Anne S. Schulp† [[email protected]], Natuurhistorisch Museum Maastricht, De Bosquetplein 6–7, 6211 kJ Maastricht, the Netherlands. *Also affiliated with: Natural History Museum of Denmark, Øster Voldgade 5–7, 1465 Copenhagen K, Denmark. †Also affiliated with: Naturalis Biodiversity Center, Darwinweg 2, 2333 CR Leiden, the Netherlands, and Faculteit Bètawetenschappen, Vrije Universiteit Amsterdam, De Boelelaan 1085, 1081 HV Amsterdam, the Netherlands. Received 11.7.2017; revised 4.10.2017; accepted 10.10.2017.

Key words: Marine reptiles, Maastrichtian, northern Europe, palaeogeography, food chain.

THE SMALL durophagous mosasaur Carinodens belgi- described here, but was recovered in October 2016 by cus (Woodward 1891) (see Dollo 1913) is known from a an amateur collector Stefan Lips from Havelsee, handful of dentaries from the Maastrichtian type area and Germany. It was declared as value to the Danish state Morocco, and a few dozen isolated teeth (e.g., Jagt 2005, under Danekræ (DK-907), and is now accessioned into Holwerda et al. 2013, Mulder et al. 2013, Schulp, Polcyn the Natural History Museum of Denmark under the et al. 2013, Jagt 2015); the smaller and somewhat more catalogue number NHMD-157504. gracile Carinodens minalmamar is even rarer (Schulp, Averianov et al. 2010, Schulp, Bardet et al. 2010). This mosasaur genus has been reported from both sides of the Institutional abbreviations Northern and Southern Atlantic, and additional occur- NHMD: Natural History Museum of Denmark, Copen- rences range into the eastern Tethyan realm. To date, the hagen, Denmark; DK: Danekræ Collection, Natural His- taxon has been reported from the Netherlands, Belgium, tory Museum of Denmark, Copenhagen, Denmark. Bulgaria, Russia, Ukraine, Morocco, Jordan, Angola and OESM: Østsjællands Museum, Denmark; OCP: Office the Congo Basin, the USA, and Brazil (Schulp et al. Chérifien des Phosphates, Khouribga, Morocco. 2004, Mulder et al. 2013 and references therein). Inter- estingly, most of these occurrences have been recognized and reported only in the last decade. Geological setting In the eastern Atlantic Province, the northernmost NHMD-157504 derived from the K/Pg boundary section occurrences so far were the teeth reported from the in the ca 40-m-thick succession exposed in the coastal Maastrichtian type area. An isolated tooth crown found cliffs at Mandehoved at Stevns Peninsula (Fig. 2). The just below the K/Pg boundary section at the UNESCO K/Pg strata at Stevns Klint comprise the uppermost part World Heritage Site of Stevns Klint, Denmark (Fig. 1), of the Maastrichtian Møns Klint Formation, which is now extends the palaeogeographical range of Carin- represented by mounded chalk rich in bryozoan frag- odens further north to Denmark. This specimen is ments, overlain by evenly bedded benthos-poor chalk belonging to the Sigerslev Member of the Møns Klint Formation (Surlyk et al. 2006, 2013). The Sigerslev © 2017 Geological Society of Australia Inc., Australasian Palaeontologists fl https://doi.org/10.1080/03115518.2017.1391878 Member is topped by a thick nodular int band and two

Published online 29 Nov 2017 598 JESPER MILÀN et al. ALCHERINGA

Fig. 2. Stratigraphy of the Maastrichtian–Danian boundary section at the Stevns Peninsula. The tooth crown of Carinodens minalmamar (NHMD-157504) originated from the uppermost part of the Højerup Member (Møns Klint Formation, upper Maastrichtian; modified from Surlyk et al. 2006, 2013, Lauridsen et al. 2012).

Fig. 1. A, Map of northwest Europe showing the distribution of land areas and marine sedimentation during the . Stevns Klint (marked by a star) is the peninsula in the southeastern part of the Danish island of Sjælland, approximately 60 kilometres south of Copenhagen (modified from Ziegler 1990, Voigt et al. 2008). B, Map of Stevns Peninsula. The tooth crown (NHMD-157504) was recovered from the northern side of Mandehoved, indicated by an asterisk. incipient hardgrounds that, in turn, are overlain by the few metres thick mounded bryozoan-rich chalk of the Fig. 3. Locality; provenance from scree at the northern side of Man- uppermost Maastrichtian Højerup Member. The K/Pg dehoved where merely the highest metre of the late Maastrichtian boundary is exposed in the upper part of the cliff where Højerup Member (Møns Klint Formation) is exposed. The locality (55°19ʹ52.4ʺN; 12°27ʹ10.8ʺE) is indicated by an asterisk. The red bro- the basal Clay and Cerithium Limestone members ken line indicates the K/Pg Boundary. Photograph by Stefan Lips. of the Rødvig Formation occur in small depressions topped by an erosional hardground and overlain by Lower Danian bryozoan limestone mounds of the Stevns Systematic palaeontology Klint Formation. The Stevns Klint Formation is locally SQUAMATA Oppel 1811 interfingering with the middle Danian Faxe Formation, MOSASAURIDAE Gervais 1853 which is geographically restricted to the area around Gervais 1853 Faxe Limestone quarry (Fig. 2). The Carinodens tooth GLOBIDENSINI Russell 1967 was found in a scree where only the upper metre of the Højerup Member is exposed (Lauridsen et al. 2012). Carinodens Thurmond 1969 This provenance suggests stratigraphical origin from Carinodens minalmamar Schulp, Bardet et al. within the uppermost Maastrichtian (Fig. 3). 2010 ALCHERINGA FIRST DANISH CARINODENS 599

Fig. 4. Tooth crown of Carinodens minalmamar (NHMD-157504), in lingual, labial and occlusal views (photograph by Sten Lennart Jakobsen).

Description As preserved, the tooth crown is 13.5 mm mesiodistally, approximately 7.6 mm high (from the point of basal enamel flexure to the apex) and 5.8 mm labiolingually. The crown represents a small, shed replacement tooth, as evidenced by the worn apex and the absence of a root (Fig. 4). In lateral view, the tooth is ~1.78× wider than tall. This ratio corresponds to the 11th to 13th tooth positions in Carinodens belgicus (Schulp, Bardet et al., 2010, fig. 4) and also approximates the 10th tooth position in the holotype (OCP DEK/GE 453) of Carinodens minalmamar (Schulp, Bardet et al., 2010, fig. 1E). The tooth is asymmetrical in lateral view, with the worn apex offset posteriorly from the midline. The enamel surface is wrinkled, as characteristically occurs in globidensine (Schulp, Averianov et al. 2010, Schulp, Bardet et al. 2010). The enamel thickness increases towards the apex. In both labial and lingual view, two incipient sulci extend diagonally from the apex. They are less conspicuous than those on the labial side of the teeth in C. minalmamar (Schulp, Bardet et al., 2010, fig. 1D), although, the enamel of OCP DEK/GE 453 is damaged. The tapering posterior end of Fig. 5. Palaeolatitudinal distribution of Carinodens belgicus and Carinodens minalmamar. Palaeolatitudes reconstructed using Van the tooth is pronounced in occlusal view, which is con- Hinsbergen et al. 2015/paleolatitude.org; jaw outlines modified/traced sistent with the tightly imbricated tooth positioning of from Schulp, Averianov et al. 2010. 600 JESPER MILÀN et al. ALCHERINGA

Fig. 6. Reconstruction (artwork by Esther van Hulsen) of the three mosasaurid genera known to date from Stevns Klint, Denmark, with inserted pictures of their respective tooth crowns recovered from Stevns Klint. A, sp. (OESM 8617) Photograph by Leif Rasmussen. B, Mosasaurus hoffmannii (OESM 8783) Photograph by Leif Rasmussen. C, Carinodens minalmamar (NHMD-157504). Photograph by Sten Lennart Jacobsen. ALCHERINGA FIRST DANISH CARINODENS 601

C. minalmamar. Strong labiolingual compression (labio- 2015; www.paleolatitude.org). Carinodens belgicus longual/mesiodistal ratio = 2.33) also compares well appears to have been more widespread (Mulder et al. with Carinodens minalmamar (Schulp, Bardet et al., 2013) and probably occupied an ecological niche similar 2010, p. 166). to that of C. minalmamar based on their closely compa- rable dentitions. Carinodens belgicus seems to have been distributed across a palaeolatitudinal range from at least Discussion 40°N to 30°S (Fig. 5). In contrast, C. minalmamar has not yet been reported from the Southern Hemisphere, Stratigraphical age and its documented occurrences extended between 20°N The Højerup Member reaches its maximum thickness and 45°N palaeolatitude, suggesting that both (up to 4.5 metres) in the southern end of Stevns Klint, were able to exploit a wide range of habitats. and gradually thins out towards the north (Surlyk et al. 2006). At Mandehoved, the unit attains a thickness of about 1.5 metres (Surlyk et al. 2006). The exact age of Stevns Klint Late Cretaceous food web the Højerup Member is difficult to determine precisely. The vertebrate fossil assemblage from the upper Maas- Its basal level predates the terminal cooling event at ca trichtian of Denmark comprises 31 selachian species 200 kyr prior to the K/Pg boundary (Thibault & Husson (Adolfssen & Ward 2014), with additional evidence 2016, Thibault et al. 2016). It is represented by an from coprolites (Milàn et al. 2015), and at least eight incipient hardground, which reflects a hiatus of taxa of teleosteans (Bonde et al. 2008, Bonde & Leal unknown duration. Owing to the complex stratigraphy 2017, Schwarzhans & Milàn 2017). Most of the identi- of Stevns Klint, the top of the Højerup Member is fied sharks and rays were relatively small-bodied with either an erosive surface or overlain by the Fiskeler maximum lengths of less than 1.2 metres. Exceptions Member of the Rødvig Formation (Surlyk et al. 2006). include representatives of the genera Sphenodus, Noti- Based on the average sedimentation rate during the danodon, Cretalamna, Squalicorax and Pseudocorax, late Maastrichtian in eastern Denmark, the Højerup whose adult body lengths probably exceeded two Member corresponds to a time span of 50 000– metres (Adolfssen & Ward 2014). Marine 60 000 years (Thibault et al. 2016). Because NHMD- remains are comparatively rare and represented only by 157504 originates from a locality with a complete K/Pg a single chelonioid (Karl & Lindow 2009), iso- succession (Fig. 3), its age can be correlated to within lated thoracosaurid crocodilian teeth (Gravesen & the youngest half of the final 50 000–60 000 years of Jakobsen 2012), and the apex predator mosasaurids the Maastrichtian (Thibault & Husson 2016, Thibault Mosasaurus hoffmannii, Plioplatecarpus sp. (see Lind- et al. 2016). gren & Jagt 2005), together with Carinodens minalma- mar (Fig. 6), which was diminutive (ca 2 metres) by comparison and durophagous (Schulp 2005), thus occu- Taphonomy pying a lower trophic level within the ecosystem. Even though Carinodens has been reported from sites worldwide (Mulder et al. 2013 and Refs. therein), its fossil record is mostly limited to the largest, isolated Conclusion teeth, as well as an occasional dentary; these presum- ably constituted the most robust parts of the skeleton. (1) An isolated tooth crown (NHMD-157504) from the The largest crowns were situated at around the 10th to uppermost Maastrichtian of Stevns Klint, Denmark 13th tooth positions and a most frequently represented is identified as belonging to the rare durophagous in the fossil record (compare Mulder et al. 2013). Previ- mosasaur Carinodens minalmamar. ous work on stable isotopes from enamel of Carinodens (2) This is the northernmost palaeolatitudinal occur- belgicus suggests this species lived near the shore and rence of C. minalmamar, and thus extends the at shallow depths (Schulp, Vonhof et al. 2013). This palaeogeographical range of the taxon northwards might explain why this taxon has never previously been to include the Danish Basin. reported from Stevns Klint, which is an offshore deposi- (3) This new record of Carinodens in the Maastrichtian tional setting (Surlyk et al. 2006, 2013). of Denmark provides an important addition to the otherwise sparsely represented assemblage of mar- ine reptiles from the Late Cretaceous Danish Basin. Distribution and palaeobiogeography To date, Carinodens minalmamar is known from Mor- occo, southern Russia and eastern Denmark (Schulp, Acknowledgements Averianov et al. 2010, Schulp, Bardet et al. 2010). The We are grateful to Stefan Lips (Havelsee, Germany), who palaeolatitude of Stevns Klint at the end of the Creta- collected the specimen and brought it to the attention of ceous was approximately 43°N (Van Hinsbergen et al. one of us (JM). Sten Lennart Jakobsen (Natural History 602 JESPER MILÀN et al. ALCHERINGA

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