The Amazon River as well as its tributaries and surrounding rain forest hold approximately 45 freshwater turtle and terrestrial tortoise species. They're organized into 15 genera, according to the Turtle Taxonomy Working Group’s 2011 annotated checklist. The region’s turtles exhibit remarkable diversity in terms of evolutionary history, ecology and morphology.
Aquatic and Semiaquatic Cryptodira
The Amazon basin is home to 14 aquatic and semiaquatic species of the order Cryptodira, which retract their heads straight back into their shells. Five species of slider turtle (Trachemys), three mud turtles (Kinosternon) and the South American snapping turtle (Chelydra acutirostris) all have relatives in North America. The sliders are gregarious, diurnal turtles that consume plants and animals. The mud and snapping turtles are primarily carnivorous, nocturnal turtles. The snapping turtle is the largest, sometimes approaching 20 inches in length. Five species of wood turtle (Rhinoclemmys) native to the region vary greatly in their biology and natural history. Wood turtles are omnivorous. The spot-legged wood turtle (Rhinoclemmys punctularia) is primarily aquatic, the brown wood turtle (Rhinoclemmys annulata) primarily terrestrial.
Two native terrestrial tortoises, members of order Cryptodira, inhabit the Amazon rain forests. Yellow-footed (Chelonids denticulata) and red-footed (Chelonidis carbonaria) tortoises are similar in many respects, but yellow-footed tortoises prefer the humid rainforest interior while red-footed tortoises prefer the rainforest margins and adjacent savannas. The red-footed tortoise reaches only about 18 inches in length and 30 pounds; most yellow-footed tortoises are larger, sometimes reaching 30 inches in length. Both have broad diets, relative to other tortoises, but are primarily herbivorous, subsisting on flowers, fruits and herbaceous plants.
Mesoclemmys and Podocnemis
South America is home to 29 species of the order Pleurodira; also known as the side-necked turtles. Two genera contain more than half of these species: Mesoclemmys and Podocnemis. Genus Mesoclemmys has the most representatives, with 10 described species – almost 22 percent of the region’s total turtle diversity. Genus Podocnemis contains six species, including the giant Amazon River turtle (Podocnemis expansa). At one time, Amazon River turtles formed aggregations of more than 100,000 individuals on sandy beaches -- this no longer occurs, as the turtles and their eggs have been overhunted. Among the largest freshwater species in the world, these turtles may exceed 30 inches and 200 pounds.
Other Pleurodira Genera and Species
Thirteen more members of the order Pleurodira live in the Amazon basin. Four species in the genus Phrynops -- another group of turtles known as the side-necked turtles -- are highly aquatic and can reach 18 inches. Genus Peltocephalus has one species, the bigheaded Amazon River turtle (Peltocephalus dumerillianus), which reaches 18 inches, too. The single genus Platemys species, the twist-neck turtle (Platemys platycephala), is closely related to the three local species of Acanthochelys. Most of these species are small, though the recently discovered Pantanal swamp turtle (Acanthochelys macrocephala) reaches 9 inches or more. Both species of the genus Hydromedusa, the snake-necked turtles, are primitive species who prefer shallow, clear streams of the region. The red side-necked turtle (Rhinemys rufipes) is a poorly known species of South America who inhabits the Amazon River and some of its tributaries. The monotypic genus Chelus contains only the bizarre mata mata (Chelus fimbriata) whose name literally means "I kill." Mata matas lurk in murky waters, their fringelike protuberances helping camouflage them from passing fish. Mata matas capture prey by quickly sucking in the victim with a large quantity of water.
- Turtle Taxonomy Working Group: Turtles of the World, 2011 Update; Annotated Checklist of Taxonomy, Synonymy, Distribution and Conservation Status
- ReptileChannel.com: Amazon Turtles
- British Chelonia Group: The South American Tortoises
- National Aquarium: Giant Amazon River Turtle
- University of North Carolina: The Mata Mata
- Arkive.org: Big-headed Amazon River Turtle
- California Turtle and Tortoise Club: Twist-Necked Turtle, Platemys Platycephala
- Arkive.org: Pantanal Swamp Turtle
- Tortoise Trust: Rhinoclemmys Pulcherimma Manni
- IUCN Redlist: Rhinoclemmys Annulata
- Hemera Technologies/PhotoObjects.net/Getty Images