Pliotrema

Pliotrema Temporal range: Middle Miocene–Recent [1] PreꞒ Ꞓ O S D C P T J K Pg N
Sixgill sawshark, (P. warreni)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Chondrichthyes
Subclass:	Elasmobranchii
Division:	Selachii
Order:	Pristiophoriformes
Family:	Pristiophoridae
Genus:	Pliotrema Regan, 1906
Type species
Pliotrema warreni Regan, 1906

Pliotrema is a genus of sawsharks found in the Western Indian Ocean. Members of this genus differ from sawsharks of the genus Pristiophorus in having six gill slits. ^[2] The presence of six pairs of gill slits highlights this genus among sharks; outside Hexanchiformes 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. ^[3]

Taxonomy

The genus name Pliotrema comes from Ancient 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. ^[4]

Species

There are currently three recognized species in this genus: ^{[5] [6]}

• Pliotrema annae Weigmann, Gon, Leeney & Temple, 2020 (Anna's sixgill sawshark)
• Pliotrema kajae Weigmann, Gon, Leeney & Temple, 2020 (Kaja's sixgill sawshark)
• Pliotrema warreni Regan, 1906 (Warren's sixgill sawshark)

References

1. Maurice Guicharrousse-Vargas; Jaime A. Villafaña; Jorge D. Carrillo-Briceño; Pablo Oyanadel-Urbina; Romina Figueroa; José R. Pérez-Marín; Marcelo M. Rivadeneira; Jürgen Kriwet (2021). "The first fossil record of the sawshark Pliotrema (Pristiophoridae) from the Neogene of the south-eastern Pacific (Chile)". Ameghiniana. 58 (2): 122–131.
2. Compagno, Leonard J.V. (1984). Sharks of the World: An Annotated and Illustrated Catalogue of Shark Species Known to Date. Rome: Food and Agriculture Organization. ISBN   92-5-101384-5.
3. Per Berggren; Andrew Temple (March 18, 2020). "We've just discovered two new shark species – but they may already be threatened by fishing". theconversation.com.
4. Christopher Scharpf & Kenneth J. Lazara (15 January 2023). "Family PRISTIOPHORIDAE Bleeker 1859 (Saw Sharks)". The ETYFish Project Fish Name Etymology Database. Christopher Scharpf and Kenneth J. Lazara. Retrieved 9 April 2025.
5. Froese, Rainer; Pauly, Daniel (eds.). "Species in genus Pliotrema". FishBase . April 2025 version.
6. Simon Weigmann; Ofer Gon; Ruth H. Leeney; Ellen Barrowclift; Per Berggren; Narriman Jiddawi; Andrew J. Temple (March 18, 2020). "Revision of the sixgill sawsharks, genus Pliotrema (Chondrichthyes, Pristiophoriformes), with descriptions of two new species and a redescription of P. warreni Regan". PLOS ONE. 15 (3) e0228791. Bibcode:2020PLoSO..1528791W. doi: 10.1371/journal.pone.0228791 . PMC   7080233 . PMID   32187191.