Halisaurinae

Taxobox
name = Halisaurinae
fossil_range = Late Cretaceous

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image_width = 250px
image_caption = "Halisaurus"
regnum = Animalia
phylum = Chordata
classis = Sauropsida
subordo = Scleroglossa
infraordo = Anguimorpha
familia = Mosasauridae
subfamilia = Halisaurinae
subfamilia_authority = Bardet et al., 2005 Bardet N, Suberbiola XP, Iarochene M, Bouyahyaoui F, Bouya B, 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.]
subdivision_ranks = Genera
subdivision =
* "Eonatator"
* "Halisaurus"Halisaurinae is a subfamily of mosasaurs, a diverse group of Late Cretaceous marine squamates.

Bardet et al. (2005, p. 464) diagnosed the Halsaurinae as all mosasaurs more closely related to "Halisaurus" than "Moanasaurus". Unambiguous character states were listed as follows: "premaxilla-maxilla sutural contact vertical anteriorly, oblique at midpoint and horizontal posteriorly; contact plane between the parietal and the supratemporal oblique; preaxial ridge extending on two-thirds of the length of the radius; tibia and fibula long and slender with slightly expanded extremities. Ambiguous characters include "dorsal median ridge borne on the anterior two-thirds of the frontal; frontal with ventral boss; parietal foramen surrounded by a ventral boss; quadrate with large infrastapedial process; coalescent infra- and suprastapedial processes of quadrate; zygosphene-zygantrum complex absent; synapophyses of the cervical vertebrae extending ventrally to the ventral surface of the centrum; fused haemal spines."

Designation of this subfamily followed many decades of confusion surrounding the type genus, "Halisaurus," especially "H. sternbergii", a species from the Mooreville Chalk of Alabama and the Niobrara Chalk of Kansas. Originally, the species had been referred to the mosasaurine "Clidastes" Wiman CJ. 1920. Some reptiles from the Niobrara group in Kansas. "Bulletin of the Geological Institute of Uppsala" 18: 9-18 (9 figs., pls. II-IV).] , then to "Halisaurus" (Russell, 1967; p. 369 Russell DA. 1967. Systematics and morphology of American mosasaurs. "Peabody Museum of Natural History, Yale University, Bulletin" 23.] ), which was also considered a member of the Mosasaurinae at that time. Later workers Wright KR. 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.] Bell GL. Jr. 1997. A phylogenetic revision of North American and Adriatic Mosasauroidea. pp. 293-332 In: Callaway JM. and Nicholls EL, (eds.), "Ancient Marine Reptiles", Academic Press: 501 pp.] questioned the phylogenetic position and monophyly of "Halisaurus", in part because of striking morphological differences between "H. sternbergii" and the other known species of the taxon. Finally, Bardet et al. (2004) determined that "H. sternbergii" was not conspecific with the other members of the genus and erected a new genus, "Eonatator", as well a new new subfamily, consisting of "Eonatator" and "Halisaurus". Halisaurines (as members of this subfamily are collectively and informally known) were small to medium-sized mosasaurs averaging 4.5-6+ meters in length. Of all known mosasaurids, they were the least adapted to a marine lifestyle. Halisaurines are known from North America, Europe, South America, and Africa. The earliest known remains of halisaurines occur in rocks of Santonian age and the subfamily persists until the latest Maastrichtian. The etymology of this group derives from the genus "Halisaurus" (Greek "halis" = "sea" + Greek "sauros" = "lizard").

Phylogeny and Taxonomy

"Halisaurus" is an important taxon in studies of mosasaur phylogeny as it has been repeatedly considered the sister group to all other mosasaurs. A cladistic analysis by Bardet et al. (2005, p. 462-463 ) supported this model and the clade composed of "Halisaurus" and "Eonatator" was christened the Halisaurinae, "the sister group of more advanced mosasaurids."

*Halisaurinae
**"Halisaurus"
***"H. platyspondylus"
***"H. ortlebi"
***"H. arambourgi"
***"H. onchognathus" ("nomen dubium"; holotype destroyed during World War II)
**"Eonatator"
***"E. sternbergii"

References

Further reading

Bardet N, Suberbiola XP. 2001. The basal mosasaurid "Halisaurus sternbergii" from the Late Cretaceous of Kansas (North America): a review of the Uppsala type specimen. "Comptes Rendus de l'Academie des Sciences - Series IIA - Earth and Planetary Science" 332: 395-402.

External links

* [http://www.oceansofkansas.com/Halisaurus.html Oceans of Kansas' "Kansas Mosasaurs in Sweden" page, devoted to the holotype of "Halisaurus sternbergii", includes many photos]