Phosphorosaurus

Phosphorosaurus ("phosphate lizard") is an extinct genus of marine lizard belonging to the mosasaur family. Phosphorosaurus is classified within the Halisaurinae subfamily alongside the genera Pluridens, Eonatator, and Halisaurus. Stratigraphically, Phosphorosaurus is only known from the Maastrichtian age of the Late Cretaceous. Although treated as synonymous with Halisaurus in the past, recent studies recognize it as a valid genus. Two species are known: Phosphorosaurus ortliebi, from the Craie de Ciply Formation in Belgium, and P. ponpetelegans, from the Hakobuchi Formation of Hokkaido in Japan. P. ponpetelegans is only known from the very earliest Maastrichtian, whilst P. ortliebi lived throughout the Maastrichtian.

Phosphorosaurus ("phosphate lizard") is an extinct genus of marine lizard belonging to the mosasaur family. Phosphorosaurus is classified within the Halisaurinae subfamily alongside the genera Pluridens, Eonatator, and Halisaurus. Stratigraphically, Phosphorosaurus is only known from the Maastrichtian age of the Late Cretaceous. Although treated as synonymous with Halisaurus in the past, recent studies recognize it as a valid genus. Two species are known: Phosphorosaurus ortliebi, from the Craie de Ciply Formation in Belgium, and P. ponpetelegans, from the Hakobuchi Formation of Hokkaido in Japan. P. ponpetelegans is only known from the very earliest Maastrichtian, whilst P. ortliebi lived throughout the Maastrichtian.

Classification

Belgian palaeontologist Louis Dollo defined the genus in 1889, with the description of Phosphorosaurus ortliebi from the upper Maastrichtian Craie phosphateé of Ciply in Belgium. The holotype is a fragmented and incomplete skull that is estimated to have been around 42 cm long. It was reclassified as Halisaurus ortliebi in 1996, but this was not taken up by later authorities due to differences in the cranium. Below is a cladogram following an analysis by Takuya Konishi and colleagues (2015) done during the description of P. ponpetelegans, which showcases the internal relationships within the Halisaurinae. The analysis excluded the dubious Halisaurus onchognathus and the genus Pluridens. In their 2023 description of the new Halisaurus species, H. hebae, Shaker et al. performed a phylogenetic analyses of members of the Halisaurinae. They suggested that Phosphorosaurus ponpetelegans and Eonatator coellensis were more closely related to the genus Halisaurus than the type species of their respective genera. They tentatively assigned these species to Halisaurus, with "Phosphorosaurus" ponpetelegans possibly representing a distinct genus in need of a new name. The results of their analyses are displayed in the cladogram below:

References

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