Hostname: page-component-cd9895bd7-jkksz Total loading time: 0 Render date: 2024-12-18T08:04:51.988Z Has data issue: false hasContentIssue false
  • English
  • Français

New information on the skull roof of Protoichthyosaurus (Reptilia: Ichthyosauria) and intraspecific variation in some dermal skull elements

Published online by Cambridge University Press:  14 November 2019

Dean R Lomax Open the ORCID record for Dean R Lomax [Opens in a new window] ,
Judy A Massare  and
Mark Evans
Dean R Lomax*
Affiliation:
Department of Earth and Environmental Sciences, University of Manchester, Oxford Road, Manchester M13 9PL, UK
Judy A Massare
Affiliation:
Department of Earth Sciences, State University of New York, College at Brockport, Brockport, NY14420, USA
Mark Evans
Affiliation:
Centre for Palaeobiology Research, School of Geography, Geology and the Environment, University of Leicester, Leicester LE1 7RH, UK British Antarctic Survey, High Cross, Madingley Road, Cambridge CB3 0ET, UK
*
Author for correspondence: Dean R Lomax, Email: [email protected]
Get access Rights & Permissions [Opens in a new window]

Abstract

A previously unrecognized specimen of Protoichthyosaurus prostaxalis, LEICT G142.1991, from the Lower Jurassic of Barrow-upon-Soar, Leicestershire, UK, includes an almost complete three-dimensional skull that provides new information on the configuration of the skull roof. The position of the pineal foramen (between the frontals and the parietals) and an elongated internasal foramen in a depression along the midline of the nasals are clearly shown. The maxilla makes up a significant portion of the external naris ventral margin, an unusual character for the genus/species. This reflects intraspecific variation, not evidence of a new taxon. The specimen enables comparisons of skull roof morphology with Ichthyosaurus and Stenopterygius, two common Early Jurassic taxa. In particular, the position of the pineal foramen is similar to Stenopterygius, but distinguishes Protoichthyosaurus from Ichthyosaurus. The lack of a frontal–prefrontal contact and the posteriorly wide nasals distinguishes Protoichthyosaurus from Stenopterygius. We also present a revised reconstruction of the skull roof morphology of Ichthyosaurus. Three additional specimens of Protoichthyosaurus are referred to the genus: another partial skull, referred to P. prostaxalis, and two isolated forefins, identified by their unique morphology.

Keywords

intraspecific variationIchthyosaurusStenopterygiusBarrow-upon-SoarLower Jurassic
Type
Original Article
Information
Geological Magazine , Volume 157 , Issue 4 , April 2020 , pp. 640 - 650
Copyright
© Cambridge University Press 2019

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Appleby, RM (1979) The affinities of Liassic and later ichthyosaurs. Palaeontology 22, 921–46.Google Scholar
Bonaparte, CL (1841) A new systematic arrangement of vertebrated animals. Transactions of the Linnean Society of London 18, 247–304.CrossRefGoogle Scholar
de Blainville, HMD (1835) Description de quelques espèces de reptiles de la Californie, précédée de l’analyse d’un systéme général d’erpétologie et d’amphibiologie. Nouvelles Annales du Muséum d’Histoire Naturelle 4, 236–96.Google Scholar
Dick, DG, Schweigert, G and Maxwell, EE (2016) Trophic niche ontogeny and palaeoecology of early Toarcian Stenopterygius (Reptilia: Ichthyosauria). Palaeontology 59, 423–31.CrossRefGoogle Scholar
Foffa, D, Young, MT, Stubbs, TL, Dexter, KG and Brusatte, SL (2018) The long-term ecology and evolution of marine reptiles in a Jurassic seaway. Nature Ecology & Evolution 2, 1548–55.CrossRefGoogle Scholar
Ji, C, Jiang, D-Y, Motani, R, Rieppel, O, Hao, W-C and Sun, Z-Y (2016) Phylogeny of the Ichthyopterygia incorporating recent discoveries from South China. Journal of Vertebrate Paleontology 36, e1025956. doi: 10.1080/02724634.2015.1025956.CrossRefGoogle Scholar
Lomax, DR and Massare, JA (2017) Two new species of Ichthyosaurus from the lowermost Jurassic (Hettangian) of Somerset England, UK. Papers in Palaeontology 3, 1–20.CrossRefGoogle Scholar
Lomax, DR and Massare, JA (2018) A second specimen of Protoichthyosaurus applebyi (Reptilia: Ichthyosauria) and additional information on the genus and species. Paludicola 11, 164–78.Google Scholar
Lomax, DR, Massare, JA and Mistry, RT (2017) The taxonomic utility of forefin morphology in Lower Jurassic ichthyosaurs: Protoichthyosaurus and Ichthyosaurus. Journal of Vertebrate Paleontology 37, e1361433. doi: 10.1080/02724634.2017.1361433.CrossRefGoogle Scholar
Lomax, DR, Porro, LB and Larkin, NR (2019) Descriptive anatomy of the largest known specimen of Protoichthyosaurus prostaxalis (Reptilia: Ichthyosauria) including computed tomography and digital reconstruction of a three-dimensional skull. PeerJ 7, e6112. doi: 10.7717/peerj.6112.CrossRefGoogle ScholarPubMed
Maisch, MW and Hungerbühler, A (1997) Revision of Temnodontosaurus nuertingensis (v. Huene, 1931), a large ichthyosaur from the Lower Pliensbachian (Lower Jurassic) of Nurtingen, South Western Germany. Stuttgarter Beiträge zur Naturkunde Serie B (Geologie und Paläontologie) 248, 1–11.Google Scholar
Maisch, MW and Matzke, AT (2000) The Ichthyosauria. Stuttgarter Beiträge zur Naturkunde Serie B (Geologie und Paläontologie) 298, 1–159.Google Scholar
Martin, JE, Frey, E and Riess, J (1986) Soft-tissue preservation in ichthyosaurs and a stratigraphic review of the Lower Hettangian of Barrow-upon-Soar, Leicestershire. Transactions of the Leicestershire Literary & Philosophical Society 80, 58–72.Google Scholar
Massare, JA (1987) Tooth morphology and prey preference of Mesozoic marine reptiles. Journal of Vertebrate Paleontology 7, 121–37.CrossRefGoogle Scholar
Massare, JA and Lomax, DR (2016)  A new specimen of Ichthyosaurus conybeari  (Reptilia: Ichthyosauria) from Watchet, Somerset, U.K. and a re-examination of the species.  Journal of Vertebrate Paleontology 36, e1163264.CrossRefGoogle Scholar
Massare, JA and Lomax, DR (2017) A taxonomic reassessment of Ichthyosaurus communis and I. intermedius and a revised diagnosis for the genus. Journal of Systematic Palaeontology 16, 263–77.CrossRefGoogle Scholar
McCann, AG (1981) Montagu Browne (Alexander Montagu Browne-Anderson) 1842(?)–1923. Guild of Taxidermists Newsletter 7, 21–2.Google Scholar
McGowan, C and Motani, R (2003) Handbook of Paleoherpetology, Ichthyopterygia. Munich: Verlag Dr. Friedrich Pfeil, 175 pp.Google Scholar
McGowan, C (1973) The cranial morphology of the Lower Liassic latipinnate ichthyosaurs of England. Bulletin of the British Museum (Natural History) 24, 1–109, 9 pl.Google Scholar
McGowan, C (1974) A revision of the latipinnate ichthyosaurs of the Lower Jurassic of England (Reptilia: Ichthyosauria). Life Science Contributions of the Royal Ontario Museum 100, 1–30.Google Scholar
Maxwell, EE, Fernandez, MS and Schoch, RR (2012) First diagnostic marine reptile remains from the Aalenian (Middle Jurassic): a new ichthyosaur from southwestern Germany. PLOS ONE 7, 1–13.CrossRefGoogle ScholarPubMed
Motani, R (1999a) On the evolution and homologies of ichthyopterygian forefins. Journal of Vertebrate Paleontology 19, 28–41.CrossRefGoogle Scholar
Motani, R (1999b) Phylogeny of the Ichthyopterygia. Journal of Vertebrate Paleontology 19, 473–96.CrossRefGoogle Scholar
Motani, R (2005) True skull roof configuration of Ichthyosaurus and Stenopterygius and its implications. Journal of Vertebrate Paleontology 35, 338–42.CrossRefGoogle Scholar
Romer, AS (1956) Osteology of the Reptiles. Chicago: University of Chicago Press, 772 pp.Google Scholar
Smith, AS and Radley, JD (2007) A marine reptile fauna from the Early Jurassic Saltford Shale (Blue Lias Formation) of central England. Proceedings of the Yorkshire Geological Society 56, 253–60.CrossRefGoogle Scholar
Sollas, WJ (1916) The skull of Ichthyosaurus, studied in serial sections. Philosophical Transactions of the Royal Society of London, Series B 208, 63–126.Google Scholar