How Many Living Species of Pristid Sawfishes are there in the World Today?
Jason C. Seitz © 2014
Extant pristid sawfishes are large highly modified and elongate rays that swim like a shark and have a long snout with laterally-placed spines. The snout (called a ‘rostrum’) is actually an extension of the skull (known as a ‘chondrocranium’) and the lateral spines are called ‘rostral teeth’ by scientists. Like the rest of the skeleton of pristids, the rostrum is composed of cartilage, albeit reinforced with extra calcium. The rostrum and rostral teeth are used in food gathering. Pristids use the rostrum to stun fishes and to a lesser extent, invertebrates, which they then suck into its mouth positioned under the head. There is no cutting or tearing and pristids can only consume fish and invertebrates that fit into the mouth whole. The longest species of extant pristid, the green sawfish (Pristis zijsron), is reported to reach a total length of 7.3 m according to Last and Stevens (1994).
Pristid sawfishes can be distinguished from saw sharks (Pristiophurus spp. and Pliotrema warreni) by the lack of barbels, ventrally located gills (versus laterally located), dorso-ventrally compressed body, and uniformly sized rostral teeth. Pristids grow much larger than do saw sharks. Further, pristids prefer warm coastal waters while saw sharks inhabit deeper cooler offshore waters.
Living pristids species are globally distributed in tropical and sub-tropical coastal marine and estuarine waters, and sometimes inhabit rivers and associated freshwater bodies such as Lake Nicaragua. The center of distribution for the family is the western Pacific including northern Australia and Papua New Guinea.
All modern pristid species are considered imperiled and regarded by the International Union for the Conservation of Nature (IUCN) as ‘critically endangered’ with declining populations (www.iucnredlist.org). Unfortunately, the IUCN is not a regulatory agency and thus no protection is afforded by this group. Although up until recently, only two species were given protection under the endangered species act of 1972 (ESA), and only in waters of the United States, today, all five living species are protected by the ESA throughout their respective ranges, effective 12 January 2015 (Federal Register 79:73977–74005 [NMFS 2014]). The Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) has provided protection to all species of sawfish from international trade of sawfish parts since 2007 (www.cites.org). However, the confusing taxonomy of modern sawfishes has hampered conservation efforts and such efforts are further disadvantaged by the poorly known geographical population structure.
Pristid sawfishes can be distinguished from saw sharks (Pristiophurus spp. and Pliotrema warreni) by the lack of barbels, ventrally located gills (versus laterally located), dorso-ventrally compressed body, and uniformly sized rostral teeth. Pristids grow much larger than do saw sharks. Further, pristids prefer warm coastal waters while saw sharks inhabit deeper cooler offshore waters.
Living pristids species are globally distributed in tropical and sub-tropical coastal marine and estuarine waters, and sometimes inhabit rivers and associated freshwater bodies such as Lake Nicaragua. The center of distribution for the family is the western Pacific including northern Australia and Papua New Guinea.
All modern pristid species are considered imperiled and regarded by the International Union for the Conservation of Nature (IUCN) as ‘critically endangered’ with declining populations (www.iucnredlist.org). Unfortunately, the IUCN is not a regulatory agency and thus no protection is afforded by this group. Although up until recently, only two species were given protection under the endangered species act of 1972 (ESA), and only in waters of the United States, today, all five living species are protected by the ESA throughout their respective ranges, effective 12 January 2015 (Federal Register 79:73977–74005 [NMFS 2014]). The Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) has provided protection to all species of sawfish from international trade of sawfish parts since 2007 (www.cites.org). However, the confusing taxonomy of modern sawfishes has hampered conservation efforts and such efforts are further disadvantaged by the poorly known geographical population structure.
The author holds a juvenile female Pristis pectinata (smalltooth sawfish) caught and released in April 2014 during directed sampling in the lower Peace River in southwestern Florida by the Florida Fish and Wildlife Conservation Commission (FWC). Various metrics were recorded for study, a small portion of a dorsal fin was clipped off and retained for genetic analysis, and the animal was tagged prior to release so its movements can be tracked. The FWC sawfish research program has proven to be highly successful as of this writing as the program has tagged nearly 300 individuals, maintains almost 100 acoustic receivers, and has published 13 scientific journal articles (and counting).
Until very recently, there was six valid living species worldwide.
The Knifetooth Complex of sawfish currently consists of one living species:
Pristis microdon and Pristis perotteti have been problematic for researchers because the two species cannot be reliably differentiated by morphology and thus, these species were differentiated solely by geographic region. For specimens lacking collection data, this presents a challenge as the species may not be reliably determined at all. Molecular work has shown that these species group closely together in terms of genetic background (Naylor et al. 2012).
Because of the fact that Pristis microdon and Pristis perotteti are indistinguishable by morphology and share similar genetic backgrounds, it was proposed in 2013 by researchers that these two species should be combined. In a paper published in early 2013 and authored by Faria et al. (2013), all the Largetooth Complex species were combined into a composite species under the resurrected name of Pristis pristis. The resurrection of the formerly invalid name of Pristis pristis was based on Rule 23.1 (principle of priority) of the International Code of Zoological Nomenclature, which states that ‘the valid name of a taxon is the oldest available name applied to it’ (International Commission on Zoological Nomenclature 1999). Since the species name Pristis pristis was published in 1758 (as Squalus pristis by Carl Linnaeus), it precedes the naming of all other Largetooth Complex species. For this reason and because this name was used as a valid species after 1899, Pristis pristis is proposed by Faria et al. (2013) for use in place of Pristis microdon, Pristis perotteti, and the species of questionable validity, Pristis zephyreus.
Based on Faria et al. (2013), there are a total of five valid living species of pristids:
The Knifetooth complex (one species):
It is possible that in the future, changes may occur within the taxonomy of the living member of the genus Anoxypristis, Anoxypristis cuspidata. Gene flow between Indian Ocean and western Pacific specimens was found to be very low in a study by Faria et al. (2013). Specimens from the Indian Ocean were found to have a higher mean number of rostral teeth per side (mean of 25.6) versus western Pacific specimens (mean of 21.2) (faria et al. 2013). Results of the Faria et al. (2013) study suggest that Anoxypristis cuspidata may actually represent multiple species. In fact, a DNA-sequencing based analysis by Naylor et al. (2012) showed that Anoxypristis cuspidata had considerable genetic differences from all other living members of the family. This suggests that in the future Anoxypristis cuspidata (and perhaps the extinct members of this genus) may even be placed into a separate family distinct from the other pristids.
It is clear that there is still a lot to learn about pristids. Although it is uncertain what changes will occur in pristid taxonomy, or what new information will come to light from future scientific research, it certain that this interesting group of animals will continue to captivate scientists and layman alike for many years to come.
For more information about the species discussed above, the author suggests the following biological profiles provided by the Florida Museum of Natural History:
Sources
Faria, V.V. 2007. Taxonomic Review, Phylogeny, and Geographical Population Structure of the Sawfishes (Chondrichthyes, Pristiformes). PhD dissertation, Iowa State University, Ames, IA.
Faria, V.V., M.T. McDavitt, P. Charvet, T.R. Wiley, C.A. Simpfendorfer, and G.J.P. Naylor. 2013.Species delineation and global population structure of critically endangered sawfishes (Pristidae). Zoological Journal of the Linnean Society 167(1):136–164.
International Commission on Zoological Nomenclature. 1999. International Code of Zoological Nomenclature. The International Trust for Zoological Nomenclature, The Natural History Museum, London, UK.
Last, P.R. and J.D. Stevens. 1994.Sharks and Rays of Australia. CSIRO Division of Fisheries, Victoria, Australia.
National Marine Fisheries Service. 2014. Endangered and threatened wildlife and plants; final endangered listing of five species of sawfish under the Endangered Species Act. Federal Register 79(239):73977–74005. http://www.gpo.gov/fdsys/pkg/FR-2014-12-12/pdf/2014-29201.pdf
Naylor, G.J.P., J.N. Caira, K. Jensen, K.A.M., Rosana, W.T. White, and P.R. Last. 2012.A DNA sequence-based approach to the identification of shark and ray species and its implications for global elasmobranch diversity and parasitology. Bulletin of the American Museum of Natural History 2012(367):1–262.
The Knifetooth Complex of sawfish currently consists of one living species:
- Anoxypristis cuspidata (knifetooth sawfish [western Pacific and Indian oceans])
- Pristis clavata (dwarf sawfish [western Pacific Ocean]
- Pristis pectinata (smalltooth sawfish [eastern and western Atlantic Ocean])
- Pristis zijsron (green sawfish [western Pacific and Indian oceans])
- Pristis microdon (freshwater sawfish [western Pacific and Indian oceans])
- Pristis perotteti (largetooth sawfish [eastern and western Atlantic Ocean, eastern Pacific Ocean])
Pristis microdon and Pristis perotteti have been problematic for researchers because the two species cannot be reliably differentiated by morphology and thus, these species were differentiated solely by geographic region. For specimens lacking collection data, this presents a challenge as the species may not be reliably determined at all. Molecular work has shown that these species group closely together in terms of genetic background (Naylor et al. 2012).
Because of the fact that Pristis microdon and Pristis perotteti are indistinguishable by morphology and share similar genetic backgrounds, it was proposed in 2013 by researchers that these two species should be combined. In a paper published in early 2013 and authored by Faria et al. (2013), all the Largetooth Complex species were combined into a composite species under the resurrected name of Pristis pristis. The resurrection of the formerly invalid name of Pristis pristis was based on Rule 23.1 (principle of priority) of the International Code of Zoological Nomenclature, which states that ‘the valid name of a taxon is the oldest available name applied to it’ (International Commission on Zoological Nomenclature 1999). Since the species name Pristis pristis was published in 1758 (as Squalus pristis by Carl Linnaeus), it precedes the naming of all other Largetooth Complex species. For this reason and because this name was used as a valid species after 1899, Pristis pristis is proposed by Faria et al. (2013) for use in place of Pristis microdon, Pristis perotteti, and the species of questionable validity, Pristis zephyreus.
Based on Faria et al. (2013), there are a total of five valid living species of pristids:
The Knifetooth complex (one species):
- Anoxypristis cuspidata (knifetooth sawfish [western Pacific and Indian oceans])
- Pristis clavata (dwarf sawfish [western Pacific Ocean])
- Pristis pectinata (smalltooth sawfish [eastern and western Atlantic Ocean])
- Pristis zijsron (green sawfish [western Pacific and Indian oceans])
- Pristis pristis (largetooth sawfish [eastern and western Atlantic, eastern and western Pacific, and Indian oceans])
It is possible that in the future, changes may occur within the taxonomy of the living member of the genus Anoxypristis, Anoxypristis cuspidata. Gene flow between Indian Ocean and western Pacific specimens was found to be very low in a study by Faria et al. (2013). Specimens from the Indian Ocean were found to have a higher mean number of rostral teeth per side (mean of 25.6) versus western Pacific specimens (mean of 21.2) (faria et al. 2013). Results of the Faria et al. (2013) study suggest that Anoxypristis cuspidata may actually represent multiple species. In fact, a DNA-sequencing based analysis by Naylor et al. (2012) showed that Anoxypristis cuspidata had considerable genetic differences from all other living members of the family. This suggests that in the future Anoxypristis cuspidata (and perhaps the extinct members of this genus) may even be placed into a separate family distinct from the other pristids.
It is clear that there is still a lot to learn about pristids. Although it is uncertain what changes will occur in pristid taxonomy, or what new information will come to light from future scientific research, it certain that this interesting group of animals will continue to captivate scientists and layman alike for many years to come.
For more information about the species discussed above, the author suggests the following biological profiles provided by the Florida Museum of Natural History:
- Biological Profile for Anoxypristis cuspidata (knifetooth sawfish): http://www.flmnh.ufl.edu/fish/Gallery/Descript/KTSawfish/KTSawfish.html
- Biological Profile for Pristis clavata (dwarf sawfish): http://www.flmnh.ufl.edu/fish/Gallery/Descript/DwarfSawfish/DwarfSawfish.html
- Biological Profile for Pristis pectinata (smalltooth sawfish): http://www.flmnh.ufl.edu/fish/Gallery/Descript/STSawfish/STSawfish.html
- Biological Profile for Pristis zijsron (green sawfish): http://www.flmnh.ufl.edu/fish/Gallery/Descript/GreenSawfish/GreenSawfish.htm
- Biological Profile for Pristis microdon (freshwater sawfish): http://www.flmnh.ufl.edu/fish/Gallery/Descript/Freshwatersawfish/Freshwatersawfish.htm
- Biological Profile for Pristis perotteti (largetooth sawfish): http://www.flmnh.ufl.edu/fish/Gallery/Descript/LTSawfish/LTSawfish.html
Sources
Faria, V.V. 2007. Taxonomic Review, Phylogeny, and Geographical Population Structure of the Sawfishes (Chondrichthyes, Pristiformes). PhD dissertation, Iowa State University, Ames, IA.
Faria, V.V., M.T. McDavitt, P. Charvet, T.R. Wiley, C.A. Simpfendorfer, and G.J.P. Naylor. 2013.Species delineation and global population structure of critically endangered sawfishes (Pristidae). Zoological Journal of the Linnean Society 167(1):136–164.
International Commission on Zoological Nomenclature. 1999. International Code of Zoological Nomenclature. The International Trust for Zoological Nomenclature, The Natural History Museum, London, UK.
Last, P.R. and J.D. Stevens. 1994.Sharks and Rays of Australia. CSIRO Division of Fisheries, Victoria, Australia.
National Marine Fisheries Service. 2014. Endangered and threatened wildlife and plants; final endangered listing of five species of sawfish under the Endangered Species Act. Federal Register 79(239):73977–74005. http://www.gpo.gov/fdsys/pkg/FR-2014-12-12/pdf/2014-29201.pdf
Naylor, G.J.P., J.N. Caira, K. Jensen, K.A.M., Rosana, W.T. White, and P.R. Last. 2012.A DNA sequence-based approach to the identification of shark and ray species and its implications for global elasmobranch diversity and parasitology. Bulletin of the American Museum of Natural History 2012(367):1–262.