|
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 Formation 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'' 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Halisaurinae」の詳細全文を読む スポンサード リンク
|