Foss. Rec., 21, 55–66, 2018 https://doi.org/10.5194/fr-21-55-2018 © Author(s) 2018. This work is distributed under the Creative Commons Attribution 4.0 License. Eggs for breakfast? Analysis of a probable mosasaur biting trace on the Cretaceous echinoid Echinocorys ovata Leske, 1778 Christian Neumann and Oliver Hampe Museum für Naturkunde – Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Invalidenstrasse 43, 10115 Berlin, Germany Correspondence: Christian Neumann ([email protected]) Received: 28 September 2017 – Revised: 16 January 2018 – Accepted: 19 January 2018 – Published: 28 February 2018 Abstract. Fossil biting traces (praedichnia) represent indi- race between predator and prey. Direct evidence of preda- rect evidence of predation and shed light on fossil predator– tion, such as preserved gut contents, coprolites, or regurgi- prey interactions and fossil food webs. Especially from tated masses containing identifiable prey remains are rare and echinoderm skeletons, biting traces are well known. Here, exceptional findings. The study of the signs and traces pre- we describe the oral surface of a large Cretaceous (Maas- served on the hard skeletal parts of prey organisms that reflect trichtian) holasteroid echinoid Echinocorys ovata Leske, predatory behaviour is therefore of exceptional importance. 1778 from Hemmoor (northern Germany) which exhibits These traces (praedichnia) include skeletal breakage, biting four circular punctures arranged in a semi-circular arc. traces, borings, but also regeneration and repair patterns mir- Whereas three of the punctures penetrated the skeleton, one roring unsuccessful attacks. puncture only just hit the margin of the echinoid test at the Among marine invertebrates, the study of predation traces ambitus, leaving a long incision furrow in the skeleton. The found in echinoids (Echinodermata) proves to be peculiarly punctures were not lethal to the sea urchin as is indicated rewarding. Echinoids are the diet of a wide variety of marine by progressed skeletal regeneration and closure of the frac- predators including gastropods, crustaceans, starfish, other tures. The overall appearance of the punctures suggests that echinoids, elasmobranch and teleost fish, turtles, birds and they were produced during a single mechanical event, most marine mammals (Kowalewski and Nebelsick, 2003). Previ- likely by the biting action of the teeth of a large vertebrate ously, most authors focused on drilling predation by cassid animal. We analysed the shape and arrangement of the biting gastropods (“helmet conchs”), since their predatory strategy trace and conclude that it was probably produced by a ma- leaves the echinoid test entirely intact except for a small but rine reptile possessing a prognath tooth position, most likely diagnostic borehole that can be easily recognized. In contrast, by a globidensine mosasauroid. Our finding not only sheds the study of shell-breaking predation is more challenging, light on mosasaur feeding behaviour and prey selection but assuming that a successful attack would result in the com- also increases the knowledge of the food webs in the chalk plete destruction of the echinoid test. However, the stereomic sea ecosystem during the uppermost Cretaceous. nature of the echinoid skeleton favours the preservation of biting traces (“tooth marks”) of unsuccessful attacks (Kähn, 1928; Gripp, 1929; Thies, 1985), allowing conclusions to be drawn as to the predator’s taxonomic identity. Biting trace 1 Introduction analysis is based on the following two concepts or assump- tions (Bowers, 2003): (i) the dental characteristics of teeth Predation plays an important role in modern and ancient involved in biting are unique in species level and (ii) this ecosystems. Trophic relationships based on predation not asserted uniqueness is transferred and recorded in the bit- only shape communities but also affect the evolution of both ing trace. As a consequence, ideally preserved biting traces predators and their prey. Thus, fossil evidence of predator– allow conclusions to be made about the predators’ dentition prey interactions is important for the understanding of en- and consequently their identity (e.g., Neumann, 2000; Jacob- ergy flow in ancient ecosystems, food webs, and the arms Published by Copernicus Publications on behalf of the Museum für Naturkunde Berlin. 56 C. Neumann and O. Hampe: Eggs for breakfast? Analysis of a probable mosasaur biting trace sen and Bromley, 2009). However, the shape and pattern of of the trace from various angles has been undertaken with biting traces is influenced by many factors, which not only a digital DSLR after coating the specimen with ammonium include the biters tooth morphology and dental arrangement, chloride in order to bring out details of ornament. which in addition may vary among individuals of one species For the execution of the biting experiment, a resin model due to ontogeny or individual wear, but also by biting angle, skull with a movable jaw and a total length of 53 cm was pro- power of biting force, and nature of the substrate. Moreover, duced using the skull of the type specimen of Prognathodon echinoids possess an enormous capability to survive and re- solvayi Dollo, 1889 as a reference (Fig. 2). We decided to pair traumatic damage of the test, even when the test is pene- build such a model, because the preservation of the origi- trated (Bonasoro et al., 2004; Carnevali, 2006). Hence, skele- nal Prognathodon skull (isolated and fragile bones in a metal tal regeneration process of non-lethal lesions produced by a frame) appeared unsuitable for either producing casts or ap- biting attack may alter or even obscure the original shape of plying bite experiments. Our choice of Prognathodon solvayi the biting trace. is explained by its completeness, and because it matches the Here, we describe an exceptional biting trace found on requirements of tooth morphology, tooth position, and strati- the basal–ambital region of a holasteroid echinoid Echinoco- graphic and geographic appearance (Lingham-Soliar and rys ovata Leske, 1778 from the lower Maastrichtian chalk Nolf, 1989). Differences in dental ornamentation occurring of Hemmoor. Repair features indicate that the echinoid sur- among different species of the genus (e.g., Lingham-Soliar vived this unsuccessful attack. The large size, circular out- and Nolf, 1989; Christiansen and Bonde, 2002; Grigoriev, line, and arc-shaped arrangement of tooth traces suggests that 2013) are negligible in our experiment. In our experiment, the echinoid was bitten by a large predator possessing coni- biting traces from various angles were produced by pressing cal pointed teeth, most probably a marine reptile. We hypoth- the lower and upper jaw of the model into artificial Echinoco- esize that the echinoid was bitten by a mosasaur and experi- rys test “dummies” made of modeling clay. The resulting mentally tested this assumption by producing biting traces by traces were measured, photographed, and compared with the applying a mosasaur jaw model and echinoid clay dummies. fossil biting trace. 2 Material and methods 3 Geological context The specimen of interest is of early Maastrichtian age Our query for biting traces focussed on the echinoid genus (Belemnella sumensis Zone) and was collected in the in- Echinocorys, a common epifaunal deposit-feeding echinoid active quarry at Hemmoor, which is situated about 60 km with a worldwide distribution known from the Turonian west of Hamburg (53◦4105200 N 9◦0800700 E). Previously, the (Upper Cretaceous) to the Palaeogene. The applicability of quarry exposed a 141.5 m thick chalk succession of late early Echinocorys as a model taxon for the ichnofossils-based and early late Maastrichtian age (Belemnella sumensis Zone study of biotic interactions (parasitism, predation) in deep- to Tylocidaris baltica/Oxytoma danica Zone, see Schmid et time has been emphasized in case studies by Neumann and al., 2004). The chalk sediment is truly pelagic with minimal Wisshak (2006, 2009) and Wisshak and Neumann (2006). terrigenous influx and was deposited in a distal shelf envi- We examined more than 7000 Echinocorys specimens ob- ronment far away from the coast (Schönfeld et al., 1995). tained through our own fieldwork in the chalk of northern Throughout this section, the epifaunal deposit-feeding holas- Germany as well as from collection specimens stored at the teroid echinoid Echinocorys ovata Leske, 1778 is the most Natural History Museum, Berlin, the Geological Museum, abundant macrofossil. Whereas Echinocorys tests from this Copenhagen, the Swedish Royal Museum of Natural History, locality often exhibit biting traces produced by sharks and Stockholm and the Federal Institute for Geosciences and teleosts (Gripp, 1929; Thies, 1985; Neumann, 2003), cases Natural Resources (BGR) in Hanover, Germany. Our query of probable mosasauroid predation have not been observed resulted in the recognition of numerous predation traces. so far. Among these, a peculiar and outstanding biting trace situ- ated on the test of a large Echinocorys ovata from the Maas- trichtian of Hemmoor (MB.E. 6565, stored in the Natural 4 Results: Description of the biting trace found on History Museum, Berlin) has been discovered which is de- Echinocorys ovata scribed in the present study (Fig. 1a–c). For descriptive purposes, each tooth imprint has been The Echinocorys specimen exhibiting the biting traces mea- numbered (P1–P4, see Fig. 1a). Metric measurements of the sured 95 mm in length and 80 mm in width during life. The test dimensions and the biting trace were taken with the aid test is relatively stout and thick, measuring 4.3 mm at the of a precision slide caliper. Terms generally used to describe base. Although somewhat fragmented with most of the abo- teeth (labial, lingual, mesial, distal) are used here to describe ral side missing, the oral (i.e., lower) surface of the echinoid the tooth traces, a practice commonly used in forensic bite is well preserved. In the posterior-central part of the oral sur- mark analysis (Bowers, 2003). Photographic documentation face, four conspicuous punctures (P1–P4) are visible which Foss. Rec., 21, 55–66, 2018 www.foss-rec.net/21/55/2018/ C.