Pliotrema
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''Pliotrema'' is a
genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
of
sawshark A sawshark or saw shark is a member of a shark order (Pristiophoriformes ) bearing a unique long, saw-like rostrum (snout or bill) edged with sharp teeth, which they use to slash and disable their prey. There are eight species within the Pristi ...
s found in the Western
Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or approximately 20% of the water area of Earth#Surface, Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia (continent), ...
. Members of this genus differ from sawsharks of the genus '' Pristiophorus'' in having six gill slits. The presence of six pairs of gill slits highlights this genus among sharks; outside
Hexanchiformes The Hexanchiformes Help:IPA/English, /hɛkˈsæŋkɪfɔːrmiːz/ are a primitive Order (biology), order of sharks, numbering just five extant species in two Family (biology), families, Chlamydoselachidae and Cow shark, Hexanchidae. Chlamydoselach ...
order, ''Pliotrema'' is the only shark genus with more than five gill slits. The genus was formerly monotypic, featuring only ''P. warreni'' until the two new species were described in 2020.


Taxonomy

The
genus name Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial spec ...
''Pliotrema'' comes from
Ancient Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...
''pléōn'', meaning "many", and ''-trḗma'', meaning "holes". The specific name ''warreni'' honours Ernest Warren (1871–1945), who sent specimens to the British Museum. The specific names of the two new species are named for female relatives of Simon Weigmann, the senior author - his daughter for ''P. kajae'' and his niece for ''P. annae''.


Species

There are currently three recognized species in this genus: * '' Pliotrema annae'' Weigmann, Gon, Leeney & Temple, 2020 (Anna's sixgill sawshark) * '' Pliotrema kajae'' Weigmann, Gon, Leeney & Temple, 2020 (Kaja's sixgill sawshark) * ''
Pliotrema warreni The sixgill sawshark, ''Pliotrema warreni'' is a sawshark of the family Pristiophoridae. Unlike other sawsharks, the barbs on this shark's rostrum continue onto the sides of the head. Its barbels are also closer to its mouth than in other speci ...
'' Regan, 1906 (Warren's sixgill sawshark)


References

Shark genera Pristiophoriformes Taxa named by Charles Tate Regan {{batoid-stub