Phosphorosaurus

Phosphorosaurus ("Phosphate Lizard") is an extinct genus of mosasaur from the Late Cretaceous (Maastrichtian). Although treated as synonymous with Halisaurus in the past, recent study recognizes it as valid. Two species are known, Phosphorosaurus ortliebi from Belgium, and P. ponpetelegans from Hokkaido in Japan.

Taxonomy

Belgian palaeontologist Louis Dollo defined the genus in 1889,^[1] 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,^[2] but this was not taken up by later authorities due to differences in the cranium.^[3]

The genus Phosphorosaurus is classified in the subfamily Halisaurinae, alongside Halisaurus and Eonatator.^[4]

Two species are known, P. ortliebi and P. ponpetelegans, the latter from the oldest Maastrichtian beds located in Hokkaido, Japan.^[5][2][4] The skull of the latter species is thought to be around 50 cm long.^[4]

Palaeobiology

Analysis of Phosphorosaurus biology suggests that this mosasaur was a deep-water or nocturnal hunter, preying on animals such as squid and bioluminescent fish similar to the modern lanternfish present in the same areas. The large eyes of Phosphorosaurus had overlapping fields of vision, giving it depth perception, which would have given it an advantage when chasing such animals in poorly-lit conditions. Studies also indicate that the animal was likely an ambush predator that would lie in wait for prey, as it was not as efficient a swimmer as larger mosasaurs. ^[6]

With a length of around 3 m (10 ft), it was small compared to most other mosasaurs.^[6]

References