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Information about Eonatator

Eonatator
Enlarge picture
An early etching of a mosasaur.

An early etching of a mosasaur.
Conservation status
Extinct (fossil)
Scientific classification
Kingdom:Animalia
Phylum:Chordata
Class:Sauropsida
Order:Squamata
Family:Mosasauridae
Subfamily:Halisaurinae
Genus:Eonatator
Bardet et al., 2005
Species


Eonatator sternbergii
Eonatator is a genus of halisaurine mosasaur from the Upper Cretaceous of North America and Europe. Originally, this taxon was included within Halisaurus, but was placed in its own genus by Bardet et al. (2005). Eonatator is presently known from the Smoky Hill Chalk Member of the Niobrara Chalk Formation (Upper Coniacian - Lower Campanian) of Kansas, from the Eutaw Formation (Santonian) and Mooreville Chalk Formation (Selma Group; Santonian-Lower Campanian) of Alabama, and from the Kristianstad Basin of southern Sweden (late early Campanian). The name Eonatator means "dawn swimmer" (Greek eos = dawn + Latin natator = swimmer). At this time it contains only a single species, E. sternbergii. The species is named in honour of Charles H. Sternberg and his son, Levi, who discovered the type specimen in the Niobrara Chalk during the summer of 1918.

Like many mosasaurs, this genus has a complicated taxonomic history. The type specimen (UPI R 163, Uppsala University Palaeontological Institute, Uppsala, Sweden), a nearly complete skeleton, was originally referred to the genus Clidastes by Wiman (1920) and then to Halisaurus by Russell (1970). Hence, Clidastes sternbergii became Halisaurus sternbergii. However, by the late 1980s, some paleontologists began to suggest that H. sternbergii belonged in its own genus and that Halisaurus was polyphyletic (Wright, 1988).

Bardet et al. (2005, p. 465) diagnose Eonatator sternbergii as follows: "Ambiguous characters: premaxilla-maxilla lateral suture ending posterior to 9th maxillary teeth; tail about 40% of the head and trunk length (convergent in mosasaurines); caudal vertebra length greater than width; fewer than four pygal vertebrae; femur length about twice distal width (convergent in Clidastes). Autapomorphies: parietal with smooth triangular table extending very far posteriorly, bearing medium-sized circular foramen, located at distance twice its diameter from the frontal-parietal suture, and surrounded anteriorly and posteriorly by two parallel ridges; rounded quadrate with regularly convex tympanic ala; vertebral formula: seven cervicals, 24 dorsals, four pygals, 28 median caudals and at least 41 terminal caudals; humerus length approximately 2.5x distal width." A cladistic analysis of the Halisaurinae (Bardet et al., 2005) has indicated that Eonatator is the sister group to the clade Halisaurus and that it represents one of the most basal of known mosasaur taxa.

Eonatator was among the smaller mosasaurs. The length of the type skeleton, which represents an adult, is only 2.65 meters in length. Like many mosasaurs, it likely fed primarily on fish and smaller marine reptiles.

References

  • Bardet N., Suberbiola, X. P., Iarochene, M., Bouyahyaoui, F., Bouya, B., and Amaghzaz, M. 2005. A new species of Halisaurus from the Late Cretaceous phosphates of Morocco, and the phylogenetical relationships of the Halisaurinae (Squamata: Mosasauridae). Zoological Journal of the Linnean Society 143: 447-472.
  • Lindgren, J. et Siverson, M. 2005. Halisaurus sternbergii, a small mosasaur with an intercontinental distribution. Journal of Paleontology 79(4):763–773
  • Russell, D. A., 1970. The vertebrate fauna of the Selma Formation of Alabama. Part VII: The mosasaurs. Fieldiana, Geology Memoirs 3(7):369-380.
  • Wiman, C. J. 1920. Some reptiles from the Niobrara group in Kansas. Bulletin of the Geological Institute of Upsala 18:9-18, 9 figs., pls. II-IV.
  • Wright, K. R. 1988. A new specimen of Halisaurus platyspondylus (Squamata; Mosasauridae) from the Navesink Formation (Maastrichtian) of New Jersey. Journal of Vertebrate Paleontology 8(Supplement 3): 29A-30A.

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conservation status of a species is an indicator of the likelihood of that species continuing to survive either in the present day or the future. Many factors are taken into account when assessing the conservation status of a species: not simply the number remaining, but the
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For other uses of the term, see Fossil (disambiguation)


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Chordata
Bateson, 1885

Typical Classes

See below

Chordates (phylum Chordata) are a group of animals that includes the vertebrates, together with several closely related invertebrates.
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Sauropsida*
Goodrich, 1916

Subclasses
  • Anapsida
  • Diapsida
Synonyms
  • Reptilia Laurenti, 1768
Reptiles are tetrapods and amniotes, animals whose embryos are surrounded by an amniotic membrane, and members of the class
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Squamata
Oppel, 1811

black: range of Squamata


Suborders
see text

This article is about the Squamata order of reptiles. For the Roman scale armour see: Lorica squamata.

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Mosasauridae
Gervais, 1853

Subfamilies

Halisaurinae
Mosasaurinae
Plioplatecarpinae
Tylosaurinae

Mosasaurs (from Latin Mosa meaning the 'Meuse river' in the Netherlands, and Greek sauros
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Halisaurinae
Bardet et al., 2005

Genera
See text.
Halisaurinae (Bardet et al., 2005) is a subfamily of mosasaurs, a diverse group of Late Cretaceous marine squamates.

Bardet et al. (2005, p.
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genus (plural: genera) is part of the Latinized name for an organism. It is a name which reflects the classification of the organism by grouping it with other closely similar organisms.
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Mosasauridae
Gervais, 1853

Subfamilies

Halisaurinae
Mosasaurinae
Plioplatecarpinae
Tylosaurinae

Mosasaurs (from Latin Mosa meaning the 'Meuse river' in the Netherlands, and Greek sauros
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The Cretaceous Period is one of the major divisions of the geologic timescale, reaching from the end of the Jurassic Period (i.e. from 145.5 ± 4.0 million years ago (Ma)) to the beginning of the Paleocene epoch of the Tertiary Period (about 65.5 ± 0.3 Ma).
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Chalk (IPA: /ˈtʃɔːk/) is a soft, white, porous sedimentary rock, a form of limestone composed of the mineral calcite.
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The Coniacian is a stage of the Late Cretaceous Epoch. It spans the time between 89.3 ± 1 Ma and 85.8 ± 0.7 Ma (million years ago).

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The Campanian is a stage on the geologic time scale occurring from 83.5 ± 0.7 Ma to 70.6 ± 0.6 Ma (million years ago).

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The Santonian is a stage (geologic Age [1] ) of the Late Cretaceous Epoch. It spans the time between 85.8 ± 0.7 Ma and 83.5 ± 0.7 Ma (million years ago).

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