Mosasauroid Predation on an Ammonite – Pseudaspido- Ceras – from the Early Turonian of South-Eastern Morocco

View metadata, citation and similar papers at core.ac.uk brought to you by CORE Acta Geologica Polonica, Vol. 67 (2017), No. 1, pp. 31–46 provided by Portsmouth University Research Portal (Pure) DOI: 10.1515/agp-2017-0003 Mosasauroid predation on an ammonite – Pseudaspido- ceras – from the Early Turonian of south-eastern Morocco ANDREW S. GALE1, WILLIAM JAMES KENNEDY2 and DAVID MARTILL3 1Department of Earth and Environmental Sciences, University of Portsmouth, Portsmouth PO1 3QL, United Kingdom.E-mail: [email protected] 2Oxford University Museum of Natural History, Parks Road, Oxford OX1 3PW, and Department of Earth Sciences, South Parks Road, Oxford OX1 3AN, United Kingdom. E-mail: [email protected] 3Department of Earth and Environmental Sciences, University of Portsmouth, Portsmouth PO1 3QL, United Kingdom. E-mail: [email protected] ABSTRACT: Gale, A.S., Kennedy, W.J. and Martill, D. 2017. Mosasauroid predation on an ammonite – Pseudaspidoceras – from the Early Turonian of south-eastern Morocco. Acta Geologica Polonica, 67 (1), 31–46. Warszawa. A juvenile specimen of the ammonite Pseudaspidoceras from the Early Turonian of the Goulmima area in the Province of Er-Rachida in south-eastern Morocco shows clear evidence of predation by a tooth-bearing verte- brate. Most of the body chamber is missing, as a result of post-burial compactional crushing. The adapertural part of the shell on the left flank of the surviving fragment of body chamber bears six circular punctuations; the right flank four. These are interpreted as the product of a single bite by a mosasauroid, probably aTethysaurus . The taxonomy of the Goulmima Pseudaspidoceras is discuused in an appendix. Key words: Predation; Ammonite; Mosasauroidea; Cretaceous; Turonian; Morocco. INTRODUCTION taceous, it is the mosasaurs that have been identified as ammonite predators, beginning with the study of Kauff- The subject of predation on ammonites has a long man and Kesling (1960), who described a 300mm diam- history, but the identity of the predators involved usually eter Placenticeras (first illustrated by Fenton and Fenton remains problematic. Of early records, Frentzen (1936) in 1958) from the Late Campanian Pierre Shale of South described specimens of the Early Jurassic ammonite Dakota that had been bitten, in their interpretation no less Amaltheus in saurian stomach contents, whilst chunks than 16 times, by what they concluded to be a platycar- bitten from the adapical part of the body chamber of pine mosasaur (we suggest that the mosasaur was playing Jurassic haploceratid and oppellid ammonites and the with its prey, as do contemporary cetaceans). Kauffman Cretaceous perisphinctid Endemoceras were ascribed (1990) took this view further, and wrote of coevolution to decapod crustaceans by Roll (1935) and Thiermann of ammonites and mosasaurs, and claimed them as the (1964) respectively. Martill (1990) suggested that circular ecologically dominant predators of Cretaceous marine holes arranged in an arc on an example of Kosmoceras seas, and indicated the existence in collections of around from the Middle Jurassic Oxford Clay of Cambridgeshire 30 more specimens with definite predation marks. The in eastern England were made by a semionotid fish with predation interpretation did not gain universal support. durophagous dentition. Damage to ammonite shells, in Thus Kase et al. (1998) and Seilacher (1998) concluded part the result of predation, and subsequent repair is re- that the supposed mosasaurUnauthenticated bite marks and punctuations viewed by Hoffmann and Keupp (2015). In the late Cre- were the Downloadcrushed impressions Date | 9/26/17 of limpet12:44 PM pits. 32 ANDREW S. GALE ET AL. By far the best documented account of the subject, that was cemented at a relatively early point in the post- which definitively defends the predatorvs limpet view burial history of the shells, because they retain their of the damage to Placenticeras shells is that of Tsujita original proportions, and do not show signs of crushing. and Westermann (2001). These authors studied over The circular depressions are shallow, with a concave 200 perforated specimens from the Late Campanian base, and are formed in the material that makes up the Bearpaw Formation of southern Alberta, suggesting internal mould. Some are weathered free of enclos- that approximately 10% of the Placenticeras shells ing shale matrix; others have a lining of compacted from the area and interval had been so afflicted. shale. The structures on phragmocones resemble those Evidence of mosasaur attack on externally shelled describes as lobe voids by Seilacher (1966); there are cephalopods outside of the northern part of the Western striking similarities between text-fig. 1d, e, in Odunze Interior of the United States and Canada is limited. Saul and Mapes (2013) and text-fig. 2a in Seilacher (1998). (1976) recorded possible mosasaur bite impressions on The single internal mould of a body chamber with pits a specimen of Anapachdiscus peninsularis (Anderson (Odunze and Mapes 2013, text-fig. 2e; see Zaborski and Hanna, 1935) from the Early Maastrichtian Rosario 1982, text-fig. 34a, b for a much better picture of this Formation of Baja California, Mexico. The specimen, specimen) cannot, however be so explained. There are 11.8 cm in maximum diameter, has a series of punctua- a number of possible processes that may have produced tions, interpreted as the result of two bites (Saul 1976); the shallow, circular depressions in this specimen, and Kauffman (2004, p. 97) rejected this interpretation, and possibly the others: suggested that a large fish was responsible. He noted, 1. The depressions record the presence of low cir- however, a punctured shell of the ammonite Pachydis- cular domes of thickened shell material laid down on cus suiciaensis (Meek, 1861) described in Ludvigsen the inner surface of the body chamber of the juvenile and Baird (1994) from the Late Campanian Lambert ammonites, and, as growth proceeded, were left on Formation of Vancouver Island, British Columbia, Can- the wall of successive camerae. Following burial and ada. Kauffman (2004) defended the bites interpretation, cementation of the material infilling the camerae, the and described evidence for mosasaur attack on nauti- original aragonitic shell material dissolved, leaving loids from the Campanian of San Diego County, Califor- depressions in the infilling of the camerae, into which nia. A twice-bitten specimen referred to as Argonautilus subsequent compaction impressed shale matrix. catarinae Sundberg (presumably Anglonautilus catari- 2. Rather that the result of thickenings in the shell, nae Sundberg, 1984) was interpreted as sick or recently there were depressions in the shell of the ammonite dead on the basis of the inferred direction of attack. An that did not perforate the shell. These depressions cor- external mould at the same outcrop as this specimen was responded to low domes on the interior of the shell, interpreted, on the basis of a latex cast, as being from which gave rise to the shallow depressions as a result of a nautiloid bitten by both a large and a small mosasaur, the diagenetic sequence proposed above. Conceivably, “of the same species (i.e. a mother and her offspring)”, these depressions could be the result of bites that did not interpreted as “possibly showing a mother teaching a perforate the shell, but convincing evidence is lacking. juvenile to subdue its prey” (Kauffman 2004, p. 100). All of the convincing well-documented examples Kauffman and Skwarko (2013) recorded over 100 of mosasaur-bitten ammonite shells are thus from specimens of Placenticeras, Sphenodiscus and, less North America, the overwhelming majority from the commonly, Baculites that “show mosasaur and, rarely, Late Campanian of the northern part of the Western giant fish predation marks”. They also described a nau- Interior of the United States and Alberta in Canada. tiloid (Eutrephoceras) with mosasaur bite marks from The only older record is “One possible Globidens the Early Maastrichtian Pierre Shale south of Boulder bite mark (with blunt, shell-crushing teeth) is known in Jefferson County, Colorado. from an Upper Cenomanian Metoicoceras from Texas” Odunze and Mapes (2013) described and illustrated (Kauffman 1990, p. 188). Without illustration or de- what they termed “nearly circular, oval and irregular scription it is impossible to evaluate this record (an ex- holes in Cretaceous ammonoids” from the latest Cam- amination of more than 30 Metoicoceras and Placen- panian to Early Maastrichtian Nkoporo Formation of ticeras with aragonitic shell preserved from the Late southern Nigeria (rather better illustrations of most of Cenomanian Britton Formation of north-central Texas the specimens are to be found in Zaborski 1984, text- housed in the collections of the Oxford University Mu- figs 17, 29, 32, 34). These structures on all but one of seum of Natural History revealed only one undoubt- the specimens discussed by these authors are on inter- edly damaged shell, OUM KT1631, a Metoicoceras nal moulds of phragmocones. The internal moulds are with an irregular break toUnauthenticated the entire periphery of the preserved in buff, well-cemented fine-grained material body chamber,Download succeeded Date | 9/26/17 by an approximately12:44 PM 30° sec- MOSASAUROID PREDATION ON AN EARLY TURONIAN AMMONITE FROM MOROCCO 33 tor of regenerated shell without puncture marks of the THE PREY type regarded as characteristic of mosasaur attack. ) We describe below, what we consider to be a con- The predated ammonite, OUM KX17236 (Text-figs vincing example of attack by a mosasauroid on a ju- 1–3) comes from the Akrabou Formation (Ettachifi and venile Pseudasidoceras from the Early Turonian of Androu 2004) in the Goulmima area of Er-Rachida Goulmima in south-eastern Morocco, the earliest, and Province in south-eastern Morocco (see Kennedy et al. only convincing example from outside North America. 2008, text-figs 1and 2 for a locality map and lithostrati- 50 mm Text-fig. 1. Pseudaspidoceras madagascariensis (Basse, 1954). OUM KX17236, from the Early Turonian of Goulmima inUnauthenticated south-eastern Morocco.

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