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A new peculiar muensterellid coleoid (Cephalopoda) from the Kimmeridge Clay Formation of Dorset (England)
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Proceedings of the Geologists’ Association xxx (2017) xxx–xxx
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A new peculiar muensterellid coleoid (Cephalopoda) from the Kimmeridge Clay Formation of Dorset (England) Dirk Fuchs SNSB - Bavarian State Collection of Palaeontology and Geology, Richard-Wagner-Str. 10, 80333 Munich, Germany
A R T I C L E I N F O
Article history: Received 5 April 2017 Received in revised form 4 July 2017 Accepted 5 July 2017 Available online xxx Keywords: Coleoidea Muensterellidae Gladius morphology Lower Tithonian Kimmeridge Clay Formation
A B S T R A C T
A concretion from the lower Tithonian Kimmeridge Clay Formation (Pectinatus Zone) found by Steve Etches yielded a gladius of a coleoid cephalopod. It is peculiar in shape and has an unusual ornamentation of radiating ribs and tubercles. The new form is named Etchesia martilli n. gen. n. sp. and preliminarily placed within the octobrachian family Muensterellidae based on its limpet-like gladius. Through the presence of radiating ribs as well as the absence of a narrow anterior rachis E. martilli n. gen. n. sp. is similar to Pearceiteuthis buyi from the Oxford Clay Formation (Callovian). The new muensterellid is unique in having an enrolled patella apex, which is located close to the posterior gladius rim. E. martilli n. gen. n. sp. represents the first muensterellid coleoid from the Kimmeridge Clay Formation. A phylogenetic relationship of E. martilli n. gen. n. sp. (and Pearceiteuthis) with cirrate and incirrate octopods is discussed, although further information on soft parts such as the muscular mantle is necessary. © 2017 The Geologists' Association. Published by Elsevier Ltd. All rights reserved.
1. Introduction Muensterellidae Roger, 1952 is a Jurassic family of coleoid cephalopods, whose limpet-like gladius (pen) in the dorsal mantle is easy to be identified. Muensterellids are tiny compared to their gigantic relatives, the Enchoteuthidae Larson, 2010 from the Upper Cretaceous of North America, who has been categorized as “prehistoric sea monsters” (Hoganson, 2010, 2014). The enormous body sizes of these squid-like animals have been reconstructed on the basis of gladius lengths of up to two metres. As all Mesozoic gladius-bearing coleoids, muensterellids and enchoteuthids are eight-armed and therefore precursors of octopuses (e.g., Kröger et al., 2011; Klug et al., 2015; Sutton et al., 2015; Donovan and Fuchs, 2015; Fuchs, 2016). The Kimmeridge Clay Formation previously attracted the interests of coleoid experts when Hewitt and Wignall (1988) found that the gladius of Trachyteuthis was originally composed of organic material rather than of a biomineralized fabric (compare Naef, 1922). Their observation has later applied to all Mesozoic gladiusbearing coleoids (Donovan, 2016 and references therein). Apart from Hewitt and Wignall (1988), Kimmeridge Clay Formation coleoids have – compared to the approximately contemporaneous lithographic limestones in South Germany (Nusplingen and Altmühltal formations) – been scarcely studied (Owen, 1855; Wignall, 1990).
E-mail address: [email protected] (D. Fuchs).
The Etches Collection houses a gladius-like structure, whose peculiar ribbing provoked Dave Martill to contact me. Indeed, the specimen found by Steve Etches in Kimmeridge Bay near Kimmeridge represents a complete and weakly compressed gladius preserved in a calcareous concretion. Although the capulus-like elevation is characteristic for a muensterellid gladius, its overall morphology is nevertheless unique. On the occasion of the opening of the Etches Collection, it is the purpose of the present contribution to describe and discuss this enigmatic specimen. The Etches Collection is owned by a Trust and has a constitution that protects the collection in perpetuity. It is a public collection and already has several holotypes in the collection and many more figured specimens. 2. General morphology of the muensterellid gladius According to Fuchs (2016), who has recently reviewed their general morphology and terminology, Mesozoic gladii are subdivided into three main morphotypes: the prototeuthid, loligosepiid, and teudopseid type representing the three suborders Prototeuthina, Loligosepiina, and Teudopseina. The two families Muensterellidae and Enchoteuthidae belong to the Teudopseina; their limpet-like gladius is therefore a modification of the teudopseid gladius (Fig. 1A–D). In all three main morphotypes, the median gladius field and its lateral fields jointly originate in the rear of the mantle and only grow anteriorwards (the gladius nucleus is situated in the rear of the mantle; Fig. 1A, C). Muensterellid and enchoteuthid gladii are unique in having a posterior growth front (the gladius nucleus is not situated in the rear of the mantle; Fig.1B, D). Consequently, the lateral fields exceed the posterior
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Please cite this article in press as: D. Fuchs, A new peculiar muensterellid coleoid (Cephalopoda) from the Kimmeridge Clay Formation of Dorset (England), Proc. Geol. Assoc. (2017), http://dx.doi.org/10.1016/j.pgeola.2017.07.004
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Fig. 1. The teudopseid gladius morphotype (A, C) and its muensterelloid modification (B, C). A and B in dorsal aspect; C and D in lateral aspect with focus on the posterior gladius; blue, hyperbolar zones; grey, lateral fields; pink circle, position of gladius nucleus (=patella apex in muensterelloids); yellow, median field. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
end of the median field forming a structure that appears like a limpet. Fuchs (2016) called this posterior gladius part a patella. The capuluslike apex of the patella marks the posterior end of the median field. The median field is hence shorter than the total gladius length. As a result of this modification, the muensterellid and enchoteuthid gladius can be subdivided into an anterior free median field (or rachis) and a posterior patella. The relative length of the free median field (ratio patella length-to-total gladius length) can reach considerable lengths (Enchoteuthidae) or can be short (Muensterellidae). The chemical components of the new gladius were not analysed, but its originally chitinous composition has most probably been replaced by francolite as in all Mesozoic gladii (see Donovan, 2016). 3. Geological setting The new muensterellid gladius has been collected in Kimmeridge Bay near Kimmeridge (Dorset, UK) and in detail from the Pectinatus Zone of the lower Tithonian Kimmeridge Clay Formation. The author follows the stratigraphic scheme of Gallois (2010, 2016), although the author is aware that alternative schemes exist (e.g., Cope, 1978, 2015). 4. Systematic palaeontology Subclass Coleoidea Bather, 1888 Superorder Octobrachia Haeckel, 1866 (=Vampyropoda sensu Boletzky, 1992) Order Octopoda Leach, 1817 (=Octobrachia sensu Boletzky, 1992)
Suborder Teudopseina Starobogatov, 1983 Family Muensterellidae Roger, 1952 Type genus: Muensterella Schevill, 1950, p. 117 Other genera included: Celaenoteuthis Naef, 1922, p. 153,Etchesia n. gen. Stratigraphical and geographical range: Upper Jurassic (upper Kimmeridgian — lower Tithonian) of UK, south-western Germany, and Antarctica. Remarks: Late Cretaceous genera such as Enchoteuthis Miller and Walker, 1968, Niobrarateuthis Miller, 1957, and Tusoteuthis Logan, 1898 were placed within the Muensterellidae until Larson (2010) separated them and erected the family Enchoteuthidae. “Muensterella” tonii Wade, 1995 from the Lower Cretaceous of Australia is in this context regarded as a member of the Enchoteuthidae (own observation). Lower Tithonian Listroteuthis Wagner, 1859 has been considered as a third genus of the Muensterellidae, although the gladius morphology strongly resembles the type species Muensterella. Its systematic and morphological independence is currently under investigation. The Callovian genus Pearceiteuthis Hewitt and Jagt, 1999, originally attributed to the Muensterellidae, is here regarded as a member of a new muensterelloid family (Fuchs and Schweigert, Submitted for publication). Genus Etchesia n. gen.
Please cite this article in press as: D. Fuchs, A new peculiar muensterellid coleoid (Cephalopoda) from the Kimmeridge Clay Formation of Dorset (England), Proc. Geol. Assoc. (2017), http://dx.doi.org/10.1016/j.pgeola.2017.07.004
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Etymology: after Steve Etches, local at Kimmeridge (Dorset), worldwide acknowledged fossil collector, and initiator of the Etches Collection in the Museum of Jurassic Marine Life. Type species: Etchesia martilli n. sp. Diagnosis: small-sized muensterelloids; gladius spearhead-like, wide (ratio patella width-to-gladius length 0.88) without rachislike anterior projection; median field wide (opening angle 40 ); free median field gently constricted, anteriorly blunt, slightly shorter than patella (ratio patella length-to-gladius length 0.58); patella moderate in width (ratio median field widthhypz-to-lateral field widthmax 0.35–0.45), wide oval in shape (ratio patella widthto-patella length 1.43); apex shifted close to posterior gladius rim (ratio median field length-to-gladius length 0.82), ratio hyperbolar zone length-to-median field length 0.53; patella margin distinctly serrated; dorsal surface ornamented with radial ribs and tubercles; spines unknown; soft tissues unknown. Included species: only the type species
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Stratigraphical and geographical range: known only from the type locality E. martilli n. sp. Fig. 2A–C Etymology: after David M. Martill, a merited British palaeontologist and expert on fossil cephalopods. Holotype: MJML K1802 (housed in the Etches Collection, Museum of Jurassic Marine Life) Type locality: Kimmeridge Bay, Kimmeridge, Dorset, England (grid reference SY 9058 7914) Type horizon: Kimmeridge Clay Formation, Pectinatites pectinatus Zone (=lower Tithonian, Semiformiceras semiforme/fallauxi Chronozones of international standard) Description: the holotype consists of a nearly complete gladius in dorsal view; only its outer margins are partly incomplete (and therefore blurring the bilateral symmetry of the gladius). The shape is roughly spearhead-like with the tip anteriorwards. The gladius measures 47 mm in total length and 32 mm in total width.
Fig. 2. The gladius of Etchesia martilli n. gen. n. sp., holotype (MJML K1802), Kimmeridge Bay (Dorset, UK), Kimmeridge Clay Formation (lower Tithonian, Pectinatus Zone). A, dorsal view, B, schematic outline with diagnostic measurements; C, lateral view. Alpha, opening angle; blue, hyperbolar zones; grey, lateral fields; pink circle, position of gladius nucleus; yellow, median field. scale bar = 10 mm. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Please cite this article in press as: D. Fuchs, A new peculiar muensterellid coleoid (Cephalopoda) from the Kimmeridge Clay Formation of Dorset (England), Proc. Geol. Assoc. (2017), http://dx.doi.org/10.1016/j.pgeola.2017.07.004
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A subdivision in median field, hyperbolar zones and lateral fields is indistinct since neither growth increments nor asymptotes are visible. However, a distinct constriction after c. 66% of the preserved length can be interpreted as the anterior end of the hyperbolar zone. At this point, the median field is c.15 mm wide. Towards anterior, the free median field appears to show a gentle constriction. The anterior tip of the median field might have been weakly pointed, whereas the posterior margin was most probably rounded. Posterior to the main constriction are the gladius margins fringed or serrated, while anteriorly margins appear even. The patella apex is situated only 5 mm away from the posterior end of the gladius. In lateral view, one can see that it is clearly elevated (c. 3–4 mm above the level of the outer margins) and slightly enrolled giving the apex a capulus-like appearance. In contrast to otherwise convex gladius surface is the posteriormost part strongly concave and pulled below the patella apex. The apex is the centre of numerous radiating ribs on the dorsal gladius surface. The most pronounced rib corresponds to the median keel, which is flanked on either side by 6–7 ribs continuously decreasing in size. The rib pair that meets with the anterior end of the hyperbolar zone is considered to be equivalent with the inner asymptotes and therefore with the opening angle of the median field. It diverges at an angle of 40 . Additional very delicate ridges ornament the posteriormost part of the gladius. There are tubercles visible on the top of the ribs as well as in between the ribs. At least in the posterior gladius half, one gets the impression that the ribs slightly protrude the sectors between the ribs, which would suggest a serrated outer gladius margin. Soft tissues are not preserved. 5. Discussion The limpet-like gladius unambiguously identifies E. martilli n. sp. as a muensterelloid teudopseid. The lack of a long free rachis excludes affinities with Enchoteuthidae (see Larson, 2010) and instead favours affinities with the Muensterellidae. E. martilli n. sp. can be distinguished from slightly older Muensterella scutellaris (Figs. 3 A and 4 ) and Celaenoteuthis incerta (Figs. 3B and 4) by the absence of a free rachis-like anterior median field and by the
possession of ribs ornamenting the dorsal gladius surface. With respect to the latter features, the new muensterellid resembles Callovian Pearceiteuthis buyi (Fig. 3C). By contrast to P. buyi, E. martilli n. sp. is mainly characterized by a posteriorly shifted apex, which is moreover slightly enrolled. Phylogenetically, evidence of tubercles on the radiating ribs is surprising as a dorsal tuberculation (or granulation) has previously been thought to be characteristic of the teudopseid family Trachyteuthidae (Fuchs et al., 2007; Fuchs, 2016). Fuchs (2009), Fuchs and Larson (2011) and more recently Fuchs et al. (2016) reconstructed a sister group relationship between muensterellid and the palaeololiginid teudopseids. Such a relationship would expose the presence of dorsal tubercles on muensterellid and trachyteuthid gladii as a convergent character. Fuchs (2009) picked up an idea proposed by Haas (2002) and Bizikov (2004) whereupon the gladius vestige of extant octopuses (Octopoda: finned Cirrata and fin-less Incirrata) derived from a teudopseid gladius and put forward arguments for a derivation specifically from muensterellid teudopseids. In extant cirrate octopods, the gladius vestige represents an important attachment site for the muscular fins. Morphogenetically, this fin support is commonly regarded as missing anterior portions of the median field by which it is significantly shorter than the mantle length (Fuchs, 2016). In Muensterella (and most probably Celaenoteuthis as well), the median field reaches the anterior mantle edge (Fuchs et al., 2003; Fuchs, 2009). This fact shows that the latter taxa secreted a fully developed gladius, a character, which excludes both from the list of direct ancestors. The gladius morphology displayed by E. martilli n. sp. can neither support or reject the idea of muensterellids being stem lineage octopods owing to the lack of fossilized mantle tissues. In case future records of E. martilli n. sp. (and Pearceiteuthis) provide evidence about a gladius significantly shorter than their mantle, they should be regarded as stem octopods. Gladii of Trachyteuthis from the Kimmeridge Clay Formation preserved in association with fossilized mantle musculature (own obs.) demonstrates that E. martilli n. sp. can likewise been found with remains of the mantle. Stratigraphically, E. martilli n. sp. represents the first muensterellid from the Upper Jurassic of UK (Fig. 4) and – besides P. buyi
Fig. 3. Schematic comparison of muensterelloid gladii. A, Muensterella scutellaris (Münster, 1842), upper Kimmeridgian – lower Tithonian; B, Celaenoteuthis incerta Naef, 1922, lower Tithonian; C, Etchesia martilli n. gen. n. sp., lower Tithonian (Bolonian); D, Pearceiteuthis buyi Hewitt & Jagt, 1999, Callovian. Blue dashed line, border between anterior free median field and posterior patella; pink circles, position of of patella apex. If the anterior gladius rim of Etchesia and Pearceiteuthis corresponds to the anterior mantle edge (as in Muensterella and Celaeonoteuthis) remains unclear. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Please cite this article in press as: D. Fuchs, A new peculiar muensterellid coleoid (Cephalopoda) from the Kimmeridge Clay Formation of Dorset (England), Proc. Geol. Assoc. (2017), http://dx.doi.org/10.1016/j.pgeola.2017.07.004
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Fig. 4. Stratigraphy of Upper Jurassic muensterellids from the Kimmeridge Clay Formation of Dorset (after Gallois, 2010) and the lithographic limestones of South Germany.
from the Middle Jurassic Oxford Clay – the second muensterellid from the UK at all. Within the Kimmeridge Clay Formation, E. martilli n. sp. is, together with Trachyteuthis sp., the only octobrachian coleoid. Two octobrachians are compared to 13 species in the approximately contemporaneous lithographic limestones of South Germany (Nusplingen and Altmühltal formations) very low (Fuchs, 2015). The diversity of belemnitid coleoids, on the other hand, is similarly low in both localities (3 in the Kimmeridge Clay Formation vs. 5 in the lithographic limestones; compare Wignall, 1990 and Fuchs, 2015). Acknowledgements The author is grateful to Günter Schweigert (Staatliches Museum für Naturkunde Stuttgart) and a second anonymous referee, whose helpful comments have considerably improved the manuscript. References Bather, F.A., 1888. Shell-growth in Cephalopoda (Siphonopoda). Annals and Magazine of Natural History (Series 6) 1, 298–310. Bizikov, V.A., 2004. The shell in Vampyropoda (Cephalopoda): morphology, functional role and evolution. Ruthenica Supplement 3 1–88. Boletzky, S.v., 1992. Evolutionary aspects of development, life style, and reproduction mode in incirrate octopods (Mollusca, Cephalopoda). Revue Suisse de Zoologie 4, 755–770. Cope, J.C.W., 1978. Ammonite faunas and stratigraphy of the upper part of the Upper Kimmeridge Clay Formation of Dorset. Palaeontology 21, 469–534. Cope, J.C.W., 2015. Detailed stratigraphy of the uppermost Kimmeridge Clay Formation (Upper Jurassic) from the Swanworth Boreholes, Dorset, UK. Proceedings of the Geologists' Association 126 (1), 100–106. Donovan, D.T., 2016. Part M, chapter 9C: composition and structure of gladii in fossil Coleoidea. Treatise Online 75, 1–5. Donovan, D.T., Fuchs, D., 2015. Part M, chapter 10: fossilized soft tissues in Coleoidea. Treatise Online 73, 1–30. Fuchs, D., 2009. Octobrachia—a diphyletic taxon? Berliner Paläobiologische Abhandlungen 10, 182–192.
Fuchs, D., 2015. Tintenfische. In: Arratia, G., Schultze, H.P., Tischlinger, H., Viohl, G. (Eds.), Solnhofen. Ein Fenster in die Jurazeit. Pfeil, München, pp. 229–238. Fuchs, D., 2016. Part M, chapter 9B: the gladius and gladius vestige in fossil Coleoidea. Treatise Online 83, 1–23. Fuchs, D., Engeser, T., Keupp, H., 2007. Gladius shape variation in coleoid cephalopod Trachyteuthis from the Upper Jurassic Nusplingen and Solnhofen Plattenkalks. Acta Palaeontologica Polonica 52, 575–589. Fuchs, D., Keupp, H., Engeser, T., 2003. New records of soft parts of Muensterella scutellaris MUENSTER, 1842 (Coleoidea) from the Late Jurassic Plattenkalks of Eichstätt and their significance for octobrachian relationships. Berliner Paläobiologische Abhandlungen 3, 101–111. Fuchs, D., Larson, N.L., 2011. Diversity, morphology and phylogeny of coleoid cephalopods from the Upper Cretaceous Plattenkalks of Lebanon – part II: Teudopseina. Journal of Paleontology 85, 815–834. Fuchs, D., Reitano, A., Insacco, G., Iba, Y., 2016. The first coleoid cephalopods from the Upper Cenomanian of Sicily (Italy) and their implications for the systematicphylogenetic position of the Palaeololiginidae (Teudopseina). Journal of Systematic Palaeontology 1–14. Fuchs, D., Schweigert, G., Submitted for publication. Middle-late Jurassic gladius vestiges provide new evidence on the detailed origin of incirrate and cirrate octopuses (Coleoidea). Paläontologische Zeitschrift. Gallois, R.W., 2016. The stratigraphy of the Kimmeridge Clay Formation (Jurassic) at Westbury, Wiltshire, U.K. Proceedings of the Geologists’ Association 127 (2), 280–287. doi:http://dx.doi.org/10.1016/j.pgeola.2015.12.008. Gallois, R.W., 2010. The stratigraphy of the Kimmeridge Clay Formation (Jurassic) of the Isle of Portland Dorset, UK. Geoscience in South-West England 12, 201–208. Haas, W., 2002. The evolutionary history of the eight-armed Coleoidea. In: Summesberger, H., Histon, K., Daurer, A. (Eds.), Cephalopods — Present & Past. Abhandlungen der Geologischen Bundesanstalt, pp. 341–351. Haeckel, E.H.P.A., 1866. Generelle Morphologie der Organismen. Georg Reimer, Berlin. Hewitt, R.A., Jagt, J.W.M., 1999. Maastrichtian Ceratisepia and Mesozoic cuttlebone homeomorphs. Acta Palaeontologica Polonica 44, 305–326. Hewitt, R.A., Wignall, P.B., 1988. Structure and phylogenetic significance of Trachyteuthis (Coleoidea) from the Kimmeridge Clay Formation of England. Proceedings of the Yorkshire Geological Society 47, 149–153. Hoganson, J.W., 2010. Tusoteuthis longa: North Dakota’s 80-million-year-old Giant Squid. Geo News 37, 1–4. Hoganson, J.W., 2014. Prehistoric “Sea monsters” of North Dakota. Geo News 41, 19– 25. Klug, C., Fuchs, D., Schweigert, G., Röper, M., Tischlinger, H., 2015. New anatomical information on arms and fins from exceptionally preserved Plesioteuthis (Coleoidea) from the Late Jurassic of Germany. Swiss Journal of Palaeontology 134, 245–255.
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Kröger, B., Vinther, J., Fuchs, D., 2011. Cephalopod origin and evolution: a congruent picture emerging from fossils, development and molecules. BioEssays 33, 602– 613. Larson, N.L., 2010. Fossil coleoids from the Late Cretaceous (Campanian & Maastrichtian) of the Western Interior. Ferrantia 59, 78–113. Leach, W.E., 1817. Synopsis of the orders, families, and genera of the class Cephalopoda. The Zoological Miscellany, being descriptions of new or interesting animals 3, 137–141. Logan, W.N., 1898. The invertebrates of the Benton, Niobrara and Fort Pierre Groups. Kansas University Geological Survey 4, 431–583. Miller, H.W., 1957. Niobrarateuthis bonneri, a new genus and species of squid from the Niobrara Formation of Kansas. Journal of Paleontology 31, 809–811. Miller, H.W., Walker, M.L., 1968. Echnoteuthis melanae and Kansasteuthis lindneri, new Genera and species of Teuthids, and Sepiids from the Niobrara Formation of Kansas. Transactions of the Kansas Academy of Science 71, 176–183. Münster, G.G. zu, 1842. Über einige neue fossile schalenlose Cephalopoden und eine neue Gattung Ringelwürmer. Beiträge zur Petrefaktenkunde 5, 95–99. Naef, A., 1922. Die fossilen Tintenfische — Eine paläozoologische Monographie. Gustav Fischer, Jena.
Owen, R., 1855. Notice of a new species of an extinct genus of dibranchiate Cepalopod (Coccoteuthis latipinnis) from the upper Oolithic Shales at Kimmeridge. Quaterly Journal of the Geological Society of London 11, 124. Roger, J., 1952. Sous-classes des Dibranchiata OWEN 1836. In: Piveteau, J. (Ed.), Traité de Paléontologie. Masson, Paris, pp. 689–755. Schevill, W.E., 1950. Münsterella, new name for Kelaeno MÜNSTER 1842 non MÜNSTER 1839. Journal of Paleontology 24, 117–118. Starobogatov, Y.I., 1983. The system of the Cephalopoda. In: Starobogatov, Y.I., Nesis, K.N. (Eds.), Taxonomy and Ecology of Cephalopoda. Zoological Institute, USSR Academy of Sciences Leningrad, pp. 4–7. Sutton, M., Perales-Raya, C., Gilbert, I., 2015. A phylogeny of fossil and living neocoleoid cephalopods. Cladistics 32, 297–307. Wagner, A., 1859. Revision der bisherigen systematischen Bestimmungen der Überreste von nackten Dintenfischen aus dem Süddeutschen Juragebirge. Gelehrte Anzeigen der Königlich Bayerischen Akademie der Wissenschaften. mathematisch-physikalische Classe 34, 273–278. Wignall, P.B., 1990. Benthic palaeoecology of the Late Jurassic Kimmeridge Clay Formation of England. Special Papers in Palaeontology 43, 1–74.
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A new peculiar muensterellid coleoid (Cephalopoda) from the Kimmeridge Clay Formation of Dorset (England) Dirk Fuchs SNSB - Bavarian State Collection of Palaeontology and Geology, Richard-Wagner-Str. 10, 80333 Munich, Germany
A R T I C L E I N F O
Article history: Received 5 April 2017 Received in revised form 4 July 2017 Accepted 5 July 2017 Available online xxx Keywords: Coleoidea Muensterellidae Gladius morphology Lower Tithonian Kimmeridge Clay Formation
A B S T R A C T
A concretion from the lower Tithonian Kimmeridge Clay Formation (Pectinatus Zone) found by Steve Etches yielded a gladius of a coleoid cephalopod. It is peculiar in shape and has an unusual ornamentation of radiating ribs and tubercles. The new form is named Etchesia martilli n. gen. n. sp. and preliminarily placed within the octobrachian family Muensterellidae based on its limpet-like gladius. Through the presence of radiating ribs as well as the absence of a narrow anterior rachis E. martilli n. gen. n. sp. is similar to Pearceiteuthis buyi from the Oxford Clay Formation (Callovian). The new muensterellid is unique in having an enrolled patella apex, which is located close to the posterior gladius rim. E. martilli n. gen. n. sp. represents the first muensterellid coleoid from the Kimmeridge Clay Formation. A phylogenetic relationship of E. martilli n. gen. n. sp. (and Pearceiteuthis) with cirrate and incirrate octopods is discussed, although further information on soft parts such as the muscular mantle is necessary. © 2017 The Geologists' Association. Published by Elsevier Ltd. All rights reserved.
1. Introduction Muensterellidae Roger, 1952 is a Jurassic family of coleoid cephalopods, whose limpet-like gladius (pen) in the dorsal mantle is easy to be identified. Muensterellids are tiny compared to their gigantic relatives, the Enchoteuthidae Larson, 2010 from the Upper Cretaceous of North America, who has been categorized as “prehistoric sea monsters” (Hoganson, 2010, 2014). The enormous body sizes of these squid-like animals have been reconstructed on the basis of gladius lengths of up to two metres. As all Mesozoic gladius-bearing coleoids, muensterellids and enchoteuthids are eight-armed and therefore precursors of octopuses (e.g., Kröger et al., 2011; Klug et al., 2015; Sutton et al., 2015; Donovan and Fuchs, 2015; Fuchs, 2016). The Kimmeridge Clay Formation previously attracted the interests of coleoid experts when Hewitt and Wignall (1988) found that the gladius of Trachyteuthis was originally composed of organic material rather than of a biomineralized fabric (compare Naef, 1922). Their observation has later applied to all Mesozoic gladiusbearing coleoids (Donovan, 2016 and references therein). Apart from Hewitt and Wignall (1988), Kimmeridge Clay Formation coleoids have – compared to the approximately contemporaneous lithographic limestones in South Germany (Nusplingen and Altmühltal formations) – been scarcely studied (Owen, 1855; Wignall, 1990).
E-mail address: [email protected] (D. Fuchs).
The Etches Collection houses a gladius-like structure, whose peculiar ribbing provoked Dave Martill to contact me. Indeed, the specimen found by Steve Etches in Kimmeridge Bay near Kimmeridge represents a complete and weakly compressed gladius preserved in a calcareous concretion. Although the capulus-like elevation is characteristic for a muensterellid gladius, its overall morphology is nevertheless unique. On the occasion of the opening of the Etches Collection, it is the purpose of the present contribution to describe and discuss this enigmatic specimen. The Etches Collection is owned by a Trust and has a constitution that protects the collection in perpetuity. It is a public collection and already has several holotypes in the collection and many more figured specimens. 2. General morphology of the muensterellid gladius According to Fuchs (2016), who has recently reviewed their general morphology and terminology, Mesozoic gladii are subdivided into three main morphotypes: the prototeuthid, loligosepiid, and teudopseid type representing the three suborders Prototeuthina, Loligosepiina, and Teudopseina. The two families Muensterellidae and Enchoteuthidae belong to the Teudopseina; their limpet-like gladius is therefore a modification of the teudopseid gladius (Fig. 1A–D). In all three main morphotypes, the median gladius field and its lateral fields jointly originate in the rear of the mantle and only grow anteriorwards (the gladius nucleus is situated in the rear of the mantle; Fig. 1A, C). Muensterellid and enchoteuthid gladii are unique in having a posterior growth front (the gladius nucleus is not situated in the rear of the mantle; Fig.1B, D). Consequently, the lateral fields exceed the posterior
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Fig. 1. The teudopseid gladius morphotype (A, C) and its muensterelloid modification (B, C). A and B in dorsal aspect; C and D in lateral aspect with focus on the posterior gladius; blue, hyperbolar zones; grey, lateral fields; pink circle, position of gladius nucleus (=patella apex in muensterelloids); yellow, median field. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
end of the median field forming a structure that appears like a limpet. Fuchs (2016) called this posterior gladius part a patella. The capuluslike apex of the patella marks the posterior end of the median field. The median field is hence shorter than the total gladius length. As a result of this modification, the muensterellid and enchoteuthid gladius can be subdivided into an anterior free median field (or rachis) and a posterior patella. The relative length of the free median field (ratio patella length-to-total gladius length) can reach considerable lengths (Enchoteuthidae) or can be short (Muensterellidae). The chemical components of the new gladius were not analysed, but its originally chitinous composition has most probably been replaced by francolite as in all Mesozoic gladii (see Donovan, 2016). 3. Geological setting The new muensterellid gladius has been collected in Kimmeridge Bay near Kimmeridge (Dorset, UK) and in detail from the Pectinatus Zone of the lower Tithonian Kimmeridge Clay Formation. The author follows the stratigraphic scheme of Gallois (2010, 2016), although the author is aware that alternative schemes exist (e.g., Cope, 1978, 2015). 4. Systematic palaeontology Subclass Coleoidea Bather, 1888 Superorder Octobrachia Haeckel, 1866 (=Vampyropoda sensu Boletzky, 1992) Order Octopoda Leach, 1817 (=Octobrachia sensu Boletzky, 1992)
Suborder Teudopseina Starobogatov, 1983 Family Muensterellidae Roger, 1952 Type genus: Muensterella Schevill, 1950, p. 117 Other genera included: Celaenoteuthis Naef, 1922, p. 153,Etchesia n. gen. Stratigraphical and geographical range: Upper Jurassic (upper Kimmeridgian — lower Tithonian) of UK, south-western Germany, and Antarctica. Remarks: Late Cretaceous genera such as Enchoteuthis Miller and Walker, 1968, Niobrarateuthis Miller, 1957, and Tusoteuthis Logan, 1898 were placed within the Muensterellidae until Larson (2010) separated them and erected the family Enchoteuthidae. “Muensterella” tonii Wade, 1995 from the Lower Cretaceous of Australia is in this context regarded as a member of the Enchoteuthidae (own observation). Lower Tithonian Listroteuthis Wagner, 1859 has been considered as a third genus of the Muensterellidae, although the gladius morphology strongly resembles the type species Muensterella. Its systematic and morphological independence is currently under investigation. The Callovian genus Pearceiteuthis Hewitt and Jagt, 1999, originally attributed to the Muensterellidae, is here regarded as a member of a new muensterelloid family (Fuchs and Schweigert, Submitted for publication). Genus Etchesia n. gen.
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Etymology: after Steve Etches, local at Kimmeridge (Dorset), worldwide acknowledged fossil collector, and initiator of the Etches Collection in the Museum of Jurassic Marine Life. Type species: Etchesia martilli n. sp. Diagnosis: small-sized muensterelloids; gladius spearhead-like, wide (ratio patella width-to-gladius length 0.88) without rachislike anterior projection; median field wide (opening angle 40 ); free median field gently constricted, anteriorly blunt, slightly shorter than patella (ratio patella length-to-gladius length 0.58); patella moderate in width (ratio median field widthhypz-to-lateral field widthmax 0.35–0.45), wide oval in shape (ratio patella widthto-patella length 1.43); apex shifted close to posterior gladius rim (ratio median field length-to-gladius length 0.82), ratio hyperbolar zone length-to-median field length 0.53; patella margin distinctly serrated; dorsal surface ornamented with radial ribs and tubercles; spines unknown; soft tissues unknown. Included species: only the type species
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Stratigraphical and geographical range: known only from the type locality E. martilli n. sp. Fig. 2A–C Etymology: after David M. Martill, a merited British palaeontologist and expert on fossil cephalopods. Holotype: MJML K1802 (housed in the Etches Collection, Museum of Jurassic Marine Life) Type locality: Kimmeridge Bay, Kimmeridge, Dorset, England (grid reference SY 9058 7914) Type horizon: Kimmeridge Clay Formation, Pectinatites pectinatus Zone (=lower Tithonian, Semiformiceras semiforme/fallauxi Chronozones of international standard) Description: the holotype consists of a nearly complete gladius in dorsal view; only its outer margins are partly incomplete (and therefore blurring the bilateral symmetry of the gladius). The shape is roughly spearhead-like with the tip anteriorwards. The gladius measures 47 mm in total length and 32 mm in total width.
Fig. 2. The gladius of Etchesia martilli n. gen. n. sp., holotype (MJML K1802), Kimmeridge Bay (Dorset, UK), Kimmeridge Clay Formation (lower Tithonian, Pectinatus Zone). A, dorsal view, B, schematic outline with diagnostic measurements; C, lateral view. Alpha, opening angle; blue, hyperbolar zones; grey, lateral fields; pink circle, position of gladius nucleus; yellow, median field. scale bar = 10 mm. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
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A subdivision in median field, hyperbolar zones and lateral fields is indistinct since neither growth increments nor asymptotes are visible. However, a distinct constriction after c. 66% of the preserved length can be interpreted as the anterior end of the hyperbolar zone. At this point, the median field is c.15 mm wide. Towards anterior, the free median field appears to show a gentle constriction. The anterior tip of the median field might have been weakly pointed, whereas the posterior margin was most probably rounded. Posterior to the main constriction are the gladius margins fringed or serrated, while anteriorly margins appear even. The patella apex is situated only 5 mm away from the posterior end of the gladius. In lateral view, one can see that it is clearly elevated (c. 3–4 mm above the level of the outer margins) and slightly enrolled giving the apex a capulus-like appearance. In contrast to otherwise convex gladius surface is the posteriormost part strongly concave and pulled below the patella apex. The apex is the centre of numerous radiating ribs on the dorsal gladius surface. The most pronounced rib corresponds to the median keel, which is flanked on either side by 6–7 ribs continuously decreasing in size. The rib pair that meets with the anterior end of the hyperbolar zone is considered to be equivalent with the inner asymptotes and therefore with the opening angle of the median field. It diverges at an angle of 40 . Additional very delicate ridges ornament the posteriormost part of the gladius. There are tubercles visible on the top of the ribs as well as in between the ribs. At least in the posterior gladius half, one gets the impression that the ribs slightly protrude the sectors between the ribs, which would suggest a serrated outer gladius margin. Soft tissues are not preserved. 5. Discussion The limpet-like gladius unambiguously identifies E. martilli n. sp. as a muensterelloid teudopseid. The lack of a long free rachis excludes affinities with Enchoteuthidae (see Larson, 2010) and instead favours affinities with the Muensterellidae. E. martilli n. sp. can be distinguished from slightly older Muensterella scutellaris (Figs. 3 A and 4 ) and Celaenoteuthis incerta (Figs. 3B and 4) by the absence of a free rachis-like anterior median field and by the
possession of ribs ornamenting the dorsal gladius surface. With respect to the latter features, the new muensterellid resembles Callovian Pearceiteuthis buyi (Fig. 3C). By contrast to P. buyi, E. martilli n. sp. is mainly characterized by a posteriorly shifted apex, which is moreover slightly enrolled. Phylogenetically, evidence of tubercles on the radiating ribs is surprising as a dorsal tuberculation (or granulation) has previously been thought to be characteristic of the teudopseid family Trachyteuthidae (Fuchs et al., 2007; Fuchs, 2016). Fuchs (2009), Fuchs and Larson (2011) and more recently Fuchs et al. (2016) reconstructed a sister group relationship between muensterellid and the palaeololiginid teudopseids. Such a relationship would expose the presence of dorsal tubercles on muensterellid and trachyteuthid gladii as a convergent character. Fuchs (2009) picked up an idea proposed by Haas (2002) and Bizikov (2004) whereupon the gladius vestige of extant octopuses (Octopoda: finned Cirrata and fin-less Incirrata) derived from a teudopseid gladius and put forward arguments for a derivation specifically from muensterellid teudopseids. In extant cirrate octopods, the gladius vestige represents an important attachment site for the muscular fins. Morphogenetically, this fin support is commonly regarded as missing anterior portions of the median field by which it is significantly shorter than the mantle length (Fuchs, 2016). In Muensterella (and most probably Celaenoteuthis as well), the median field reaches the anterior mantle edge (Fuchs et al., 2003; Fuchs, 2009). This fact shows that the latter taxa secreted a fully developed gladius, a character, which excludes both from the list of direct ancestors. The gladius morphology displayed by E. martilli n. sp. can neither support or reject the idea of muensterellids being stem lineage octopods owing to the lack of fossilized mantle tissues. In case future records of E. martilli n. sp. (and Pearceiteuthis) provide evidence about a gladius significantly shorter than their mantle, they should be regarded as stem octopods. Gladii of Trachyteuthis from the Kimmeridge Clay Formation preserved in association with fossilized mantle musculature (own obs.) demonstrates that E. martilli n. sp. can likewise been found with remains of the mantle. Stratigraphically, E. martilli n. sp. represents the first muensterellid from the Upper Jurassic of UK (Fig. 4) and – besides P. buyi
Fig. 3. Schematic comparison of muensterelloid gladii. A, Muensterella scutellaris (Münster, 1842), upper Kimmeridgian – lower Tithonian; B, Celaenoteuthis incerta Naef, 1922, lower Tithonian; C, Etchesia martilli n. gen. n. sp., lower Tithonian (Bolonian); D, Pearceiteuthis buyi Hewitt & Jagt, 1999, Callovian. Blue dashed line, border between anterior free median field and posterior patella; pink circles, position of of patella apex. If the anterior gladius rim of Etchesia and Pearceiteuthis corresponds to the anterior mantle edge (as in Muensterella and Celaeonoteuthis) remains unclear. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Please cite this article in press as: D. Fuchs, A new peculiar muensterellid coleoid (Cephalopoda) from the Kimmeridge Clay Formation of Dorset (England), Proc. Geol. Assoc. (2017), http://dx.doi.org/10.1016/j.pgeola.2017.07.004
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Fig. 4. Stratigraphy of Upper Jurassic muensterellids from the Kimmeridge Clay Formation of Dorset (after Gallois, 2010) and the lithographic limestones of South Germany.
from the Middle Jurassic Oxford Clay – the second muensterellid from the UK at all. Within the Kimmeridge Clay Formation, E. martilli n. sp. is, together with Trachyteuthis sp., the only octobrachian coleoid. Two octobrachians are compared to 13 species in the approximately contemporaneous lithographic limestones of South Germany (Nusplingen and Altmühltal formations) very low (Fuchs, 2015). The diversity of belemnitid coleoids, on the other hand, is similarly low in both localities (3 in the Kimmeridge Clay Formation vs. 5 in the lithographic limestones; compare Wignall, 1990 and Fuchs, 2015). Acknowledgements The author is grateful to Günter Schweigert (Staatliches Museum für Naturkunde Stuttgart) and a second anonymous referee, whose helpful comments have considerably improved the manuscript. References Bather, F.A., 1888. Shell-growth in Cephalopoda (Siphonopoda). Annals and Magazine of Natural History (Series 6) 1, 298–310. Bizikov, V.A., 2004. The shell in Vampyropoda (Cephalopoda): morphology, functional role and evolution. Ruthenica Supplement 3 1–88. Boletzky, S.v., 1992. Evolutionary aspects of development, life style, and reproduction mode in incirrate octopods (Mollusca, Cephalopoda). Revue Suisse de Zoologie 4, 755–770. Cope, J.C.W., 1978. Ammonite faunas and stratigraphy of the upper part of the Upper Kimmeridge Clay Formation of Dorset. Palaeontology 21, 469–534. Cope, J.C.W., 2015. Detailed stratigraphy of the uppermost Kimmeridge Clay Formation (Upper Jurassic) from the Swanworth Boreholes, Dorset, UK. Proceedings of the Geologists' Association 126 (1), 100–106. Donovan, D.T., 2016. Part M, chapter 9C: composition and structure of gladii in fossil Coleoidea. Treatise Online 75, 1–5. Donovan, D.T., Fuchs, D., 2015. Part M, chapter 10: fossilized soft tissues in Coleoidea. Treatise Online 73, 1–30. Fuchs, D., 2009. Octobrachia—a diphyletic taxon? Berliner Paläobiologische Abhandlungen 10, 182–192.
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