Macrochelys

Macrochelys; Temporal range:
	Alligator snapping turtle (Macrochelys temminckii)
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	Testudines
Suborder:	Cryptodira
Family:	Chelydridae
Genus:	Macrochelys; Gray, 1856[1]
Type species
	Macrochelys temminckii; Troost, 1835

Macrochelys is a genus of very large freshwater turtles in the family Chelydridae, native to the Southeastern and Midwestern United States. Only a single extant species was recognized until 2014, when a study divided it into two, or possibly three species.[2] These turtles are easily recognized by three distinct dorsal ridges with raised spikes.

Extant species

Skeleton of an alligator snapping turtle (Macrochelys temminckii) on display at the Museum of Osteology

Traditionally, only a single extant species (M. temminckii) was recognized, but following reviews, two species are now recognized:[3][4] Anatomical differences between the two species of Macrochelys include the shape of the caudal notch at the rear of the carapace and the angle of the squamosal bone at the rear of the skull.[5] The two species are estimated to have diverged less than 3.5 million years ago. [5]

Macrochelys suwanniensis Thomas et al., 2014 – Suwannee snapping turtle
Macrochelys temminckii (Troost, 1835) – alligator snapping turtle

A third species has been proposed,[5][6] but its validity is disputed.[7] Neither the Reptile Database[3] nor IUCN's Tortoise and Freshwater Turtle Specialist Group recognize it as separate from M. temminckii.[4]

Macrochelys apalachicolae Thomas et al., 2014 – Apalachicola snapping turtle

Fossil history and extinct species

Unlike the family Chelydridae as a whole, the genus Macrochelys is exclusively North American. Hutchison (2008) considered the genus Chelydrops to be a junior synonym of Macrochelys, and recombined its type species, Chelydrops stricta from the Miocene (Early Barstovian) of Nebraska, as the (then) fourth species of Macrochelys.[8]

There are two other species known only from fossil remains:

†Macrochelys auffenbergi Dobie, 1968 (from the Middle Pliocene of Florida)
†Macrochelys schmidti (from the Early Middle Miocene of Nebraska)

References

Rhodin, Anders G.J.; van Dijk, Peter Paul; Inverson, John B.; Shaffer, H. Bradley; Roger, Bour (2012-12-31). "Turtles of the world, 2012 update: Annotated checklist of taxonomy, synonymy, distribution and conservation status" (PDF). Chelonian Research Monographs. 5: 000.251. doi:10.3854/crm.5.000.checklist.v5.2012. ISBN 978-0965354097. Archived from the original (PDF) on 2013-06-16.
John R. Platt (April 17, 2014). "Alligator Snapping Turtles, the Dinosaurs of the Turtle World, Are Actually 3 at-Risk Species". Scientific American.
Reptile Database: Macrochelys. Retrieved 26 September 2017.
Turtle Taxonomy Working Group [Rhodin, A.G.J., Iverson, J.B., Bour, R. Fritz, U., Georges, A., Shaffer, H.B., and van Dijk, P.P.] (2017). "Turtles of the World: Annotated Checklist and Atlas of Taxonomy, Synonymy, Distribution, and Conservation Status (8th Ed.)." In: Rhodin, A.G.J., Iverson, J.B., van Dijk, P.P., Saumure, R.A., Buhlmann, K.A., Pritchard, P.C.H., and Mittermeier, R.A. (Eds.). "Conservation Biology of Freshwater Turtles and Tortoises: A Compilation Project of the IUCN/SSC Tortoise and Freshwater Turtle Specialist Group." Chelonian Research Monographs 7:1–292. doi:10.3854/crm.7.checklist.atlas.v8.2017.
Thomas, T., Granatosky, M. Bourque, J., Krysko, K., Moler, P., Gamble, T., Suarez, E., Leone, E., Enge, K. & Roman, J. (2014). "Taxonomic assessment of Alligator Snapping Turtles (Chelydridae: Macrochelys), with the description of two new species from the southeastern United States." Zootaxa 3786(2): 141–165.
Joshua E. Brown (April 24, 2014). "Research splits alligator snapping turtle, 'dinosaur of the turtle world,' into three species". Phys.org.
Folt, B.; and C. Guyer (2015). "Evaluating recent taxonomic changes for alligator snapping turtles (Testudines: Chelydridae)." Zootaxa 3947(3): 447–450.
J. Howard Hutchison (2008). "History of fossil Chelydridae". In A.C. Styermark; M.S. Finkler; R.J. Brooks (eds.). Biology of the Snapping Turtle (Chelydra serpentina). Johns Hopkins University Press. pp. 14–30.

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[1] Rhodin, Anders G.J.; van Dijk, Peter Paul; Inverson, John B.; Shaffer, H. Bradley; Roger, Bour (2012-12-31). "Turtles of the world, 2012 update: Annotated checklist of taxonomy, synonymy, distribution and conservation status" (PDF). Chelonian Research Monographs. 5: 000.251. doi:10.3854/crm.5.000.checklist.v5.2012. ISBN 978-0965354097. Archived from the original (PDF) on 2013-06-16.

[2] John R. Platt (April 17, 2014). "Alligator Snapping Turtles, the Dinosaurs of the Turtle World, Are Actually 3 at-Risk Species". Scientific American.

[ReptileDatabase-3] Reptile Database: Macrochelys. Retrieved 26 September 2017.

[IUCNTurtle-4] Turtle Taxonomy Working Group [Rhodin, A.G.J., Iverson, J.B., Bour, R. Fritz, U., Georges, A., Shaffer, H.B., and van Dijk, P.P.] (2017). "Turtles of the World: Annotated Checklist and Atlas of Taxonomy, Synonymy, Distribution, and Conservation Status (8th Ed.)." In: Rhodin, A.G.J., Iverson, J.B., van Dijk, P.P., Saumure, R.A., Buhlmann, K.A., Pritchard, P.C.H., and Mittermeier, R.A. (Eds.). "Conservation Biology of Freshwater Turtles and Tortoises: A Compilation Project of the IUCN/SSC Tortoise and Freshwater Turtle Specialist Group." Chelonian Research Monographs 7:1–292. doi:10.3854/crm.7.checklist.atlas.v8.2017.

[thomas14-5] Thomas, T., Granatosky, M. Bourque, J., Krysko, K., Moler, P., Gamble, T., Suarez, E., Leone, E., Enge, K. & Roman, J. (2014). "Taxonomic assessment of Alligator Snapping Turtles (Chelydridae: Macrochelys), with the description of two new species from the southeastern United States." Zootaxa 3786(2): 141–165.

[6] Joshua E. Brown (April 24, 2014). "Research splits alligator snapping turtle, 'dinosaur of the turtle world,' into three species". Phys.org.

[Folt2015-7] Folt, B.; and C. Guyer (2015). "Evaluating recent taxonomic changes for alligator snapping turtles (Testudines: Chelydridae)." Zootaxa 3947(3): 447–450.

[8] J. Howard Hutchison (2008). "History of fossil Chelydridae". In A.C. Styermark; M.S. Finkler; R.J. Brooks (eds.). Biology of the Snapping Turtle (Chelydra serpentina). Johns Hopkins University Press. pp. 14–30.