Hostname: page-component-76fb5796d-dfsvx Total loading time: 0 Render date: 2024-04-26T08:30:45.741Z Has data issue: false hasContentIssue false
  • English
  • Français

A partial skeleton of the basal mosasaur Halisaurus platyspondylus from the Severn Formation (Upper Cretaceous: Maastrichtian) of Maryland

Published online by Cambridge University Press:  20 May 2016

Robert B. Holmes  and
Hans-Dieter Sues
Robert B. Holmes
Affiliation:
Canadian Museum of Nature, P.O. Box 3443, Station D, Ottawa, Ontario K1P 6P4, Canada,
Hans-Dieter Sues
Affiliation:
Department of Paleobiology, Royal Ontario Museum, 100 Queen's Park, Toronto, Ontario M5S 2C6, Canada,
Get access Rights & Permissions [Opens in a new window]

Abstract

A new specimen of the basal mosasaur Halisaurus platyspondylus from the Severn Formation of Prince Georges County, Maryland (Upper Cretaceous: middle Maastrichtian) represents the most complete partial skeleton of this uncommon taxon to be described to date. The characteristic dorsoventral compression of the vertebral centrum is most pronounced in the anterior trunk vertebrae, and the centra of the posterior trunk vertebrae exhibit proportions more similar to those in other mosasaurs such as Plioplatecarpus. The postorbitofrontal forms its primary contact with the frontal rather than the parietal, and the supraoccipital is firmly attached to the ventral side of the parietal. The plane of articulation between the parietals and supratemporal is neither vertical (as in Varanidae) nor horizontal (as in Mosasauridae), but forms an angle of about 55 degrees with the horizontal. The quadrate bears a long, ventrally-flared suprastapedial process but appears to lack an infrastapedial process. Close similarities in the structure of the frontal and parietal with “Clidastes” sternbergii support referral of the latter to Halisaurus, but reference of Phosphorosaurus ortliebi to Halisaurus is questionable. Halisaurus has been recorded from the Santonian to the late Maastrichtian.

Type
Research Article
Information
Journal of Paleontology , Volume 74 , Issue 2 , March 2000 , pp. 309 - 316
Copyright
Copyright © The Paleontological Society 2000

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

Baird, D. 1986a. Halisaurus and Prognathodon, two uncommon mosasaurs from the Upper Cretaceous of New Jersey. The Mosasaur, 3:37–45.Google Scholar
Baird, D. 1986b. Upper Cretaceous reptiles from the Severn Formation of Maryland. The Mosasaur, 3:63–85.Google Scholar
Baird, D., and Case, G. R. 1966. Rare marine reptiles from the Cretaceous of New Jersey. Journal of Paleontology, 40:1211–1215.Google Scholar
Bell, G. L. Jr. 1993. A phylogenetic revision of Mosasauroidea (Squamata). Unpublished Ph.D. dissertation, University of Texas at Austin, Austin, 293 p.Google Scholar
Baird, D. 1997. A phylogenetic revision of North American and Adriatic Mosasauroidea, p. 293–332. In Callaway, J. M. and Nicholls, E. L. (eds.), Ancient Marine Reptiles. Academic Press, San Diego.Google Scholar
Bukowski, F. 1983. Halisaurus platyspondylus—the third reported occurrence of this mosasaur in New Jersey. The Mosasaur, 1:119–121.Google Scholar
Caldwell, M. W., and Bell, G. L. Jr. 1995. Halisaurus sp. (Mosasauridae) from the Upper Cretaceous (?Santonian) of east-central Peru, and the taxonomic utility of mosasaur cervical vertebrae. Journal of Vertebrate Paleontology, 15:532–544.CrossRefGoogle Scholar
Carroll, R. L., and deBraga, M. 1992. Aigialosaurs: Mid-Cretaceous varanoid lizards. Journal of Vertebrate Paleontology, 12:66–86.CrossRefGoogle Scholar
Cope, E. D. 1869-1870. Synopsis of the extinct Batrachia, Reptilia, and Aves of North America. Transactions of the American Philosophical Society, N. S., 14:1–252.Google Scholar
deBraga, M., and Carroll, R. L. 1993. The origin of mosasaurs as a model of macroevolutionary patterns and processes. Evolutionary Biology, 27:245–322.Google Scholar
Dollo, L. 1889. Première note sur les mosasauriens de Mesvin. Bulletin de la Société Beige de Géologie, de Paléontologie, et d'Hydrologie, 3:271–304.Google Scholar
Frazetta, T. H. 1962. A functional consideration of cranial kinesis in lizards. Journal of Morphology, 111:287–319.CrossRefGoogle Scholar
Gervais, P. 1853. Observations relatives aux reptiles fossiles de France. Comptes Rendus de l'Académie des Sciences Paris, 36:374–377, 470-474.Google Scholar
Holmes, R. 1996. Plioplatecarpus primaevus (Mosasauridae) from the Bearpaw Formation (Campanian, Upper Cretaceous) of the Western Interior Seaway. Journal of Vertebrate Paleontology, 16:673–687.CrossRefGoogle Scholar
Johnson, J. Y. 1864. Descriptions of three new genera of marine fishes obtained at Madeira. Proceedings of the Zoological Society of London, 1863:403–410.Google Scholar
Lingham-Soliar, T. 1991. Mosasaurs from the Upper Cretaceous of Niger. Palaeontology, 34:653–670.Google Scholar
Lingham-Soliar, T. 1994. The mosasaur Plioplatecarpus (Reptilia, Mosasauridae) from the Upper Cretaceous of Europe. Bulletin de l'Institut Royal des Sciences Naturelles de Belgique, Sciences de la Terre, 64:177–211.Google Scholar
Lingham-Soliar, T. 1996. The first description of Halisaurus (Reptilia Mosasauridae) from Europe, from the Upper Cretaceous of Belgium. Bulletin de l'Institut Royal des Sciences Naturelles de Belgique, Sciences de la Terre, 66:129–136.Google Scholar
Marsh, O. C. 1869. Notice of some new mosasauroid reptiles from the green sand of New Jersey. American Journal of Science, ser. 2, 48:392–397.CrossRefGoogle Scholar
Marsh, O. C. 1870. [Remarks on Hadrosaurus minor, Mosasaurus crassidens, Liodon laticaudus, Baptosaurus, and Rhinoceros matutinus.] Proceedings of the Academy of Natural Sciences of Philadelphia, 1870:2–3.Google Scholar
McDowell, S. B. Jr., and Bogert, C. M. 1954. The systematic position of Lanthanotus and the affinities of the anguinomorph lizards. Bulletin of the American Museum of Natural History, 105:1–142.Google Scholar
Merriam, J. C. 1894. Ueber die Pythonomorphen der Kansas-Kreide. Palaeontographica, 41:1–39.Google Scholar
Rieppel, O. 1992. The skull in a hatchling of Sphenodon punctatus . Journal of Herpetology, 26:80–84.CrossRefGoogle Scholar
Romer, A. S. 1956. Osteology of the Reptiles. University of Chicago Press, Chicago, 772 p.Google Scholar
Russell, D. A. 1964. Intracranial mobility in mosasaurs. Postilla, 86:1–19.Google Scholar
Russell, D. A. 1967. Systematics and morphology of American mosasaurs (Reptilia, Sauria). Bulletin of the Peabody Museum of Natural History, Yale University, 23:1–241.Google Scholar
Russell, D. A. 1970. The vertebrate fauna of the Selma Formation of Alabama, Pt. VII, The Mosasaurs. Fieldiana: Geology Memoirs, 3:363–380.Google Scholar
Wiman, C. 1920. Some reptiles from the Niobrara Group in Kansas. Bulletin of the Geological Institution of the University of Upsala, 18:11–18.Google Scholar
Woodward, A. S. 1905. Note on some portions of mosasaurian jaws obtained by Mr. G. E. Dibley from the Middle Chalk of Cuxton, Kent. Proceedings of the Geologists' Association London, 19:185–187.CrossRefGoogle Scholar