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Extant species

Traditionally, only a single extant species (M. temminckii) was recognized, but following reviews, two species are now recognized:²³ 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.⁴ 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,⁶⁷ but its validity is disputed.⁸ Neither the Reptile Database⁹ nor IUCN's Tortoise and Freshwater Turtle Specialist Group recognize it as separate from M. temminckii.¹⁰

• 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.¹¹

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

1. John R. Platt (April 17, 2014). "Alligator Snapping Turtles, the Dinosaurs of the Turtle World, Are Actually 3 at-Risk Species". Scientific American. http://blogs.scientificamerican.com/extinction-countdown/2014/04/17/alligator-snapping-turtles-dinosaurs/ ↩

2. Reptile Database: Macrochelys. Retrieved 26 September 2017. http://reptile-database.reptarium.cz/advanced_search?genus=Macrochelys&exact%5B0%5D=genus&submit=Search ↩

3. 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. /wiki/Turtle_Taxonomy_Working_Group ↩

4. 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. ↩

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. 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. ↩

7. Joshua E. Brown (April 24, 2014). "Research splits alligator snapping turtle, 'dinosaur of the turtle world,' into three species". Phys.org. http://phys.org/news/2014-04-alligator-snapping-turtle-dinosaur-world.html ↩

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

9. Reptile Database: Macrochelys. Retrieved 26 September 2017. http://reptile-database.reptarium.cz/advanced_search?genus=Macrochelys&exact%5B0%5D=genus&submit=Search ↩

10. 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. /wiki/Turtle_Taxonomy_Working_Group ↩

11. 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. ↩