Giant Fossil Turtle Found in Peru was Among Largest Freshwater Turtles Ever Known | Sci.News
Roughly 10 to 15 million years ago, an extinct species of side-neck turtle called Chelus colombiana inhabited the vast wetlands of what is now northern South America. A newly described shell from the Peruvian Amazon suggests the species grew to enormous sizes.
First described in 1976, Chelus colombiana belongs a genus of freshwater turtles in the family Chelidae.
The genus is native to slow-moving rivers, swamps and other aquatic habitats in northern South America.
Its best-known member is the matamata turtle (Chelus fimbriata), famous for its flattened, rough, highly camouflaged shell and bizarre, knobby head and neck.
The genus is adapted to a largely aquatic lifestyle and includes turtles that ambush prey by rapidly expanding their throat and sucking water and prey into their mouths.
“The Chelidae are the most diverse group of extant pleurodiran (side-necked) turtles, comprising at least 60 species,” said Dr. Edwin-Alberto Cadena, a researcher with the Universidad del Rosario, Smithsonian Tropical Research Institute and the Field Museum of Natural History, and his colleagues.
“They are distributed across Australia, New Guinea, Indonesia, and South America.”
“The largest living chelid is Chelus fimbriata, with females — typically larger than males — reaching a maximum straight carapace length of 52.6 cm (1.7 feet).”
“However, the average carapace length for adult females is approximately 29.5 cm (1 feet).”
In a new study, Dr. Cadena and co-authors examined two new fossil shells of Chelus colombiana.
The larger specimen, cataloged as MUSM-920, measures 84.6 cm (2.8 feet) along its longest edge.
The researchers estimate that the individual weighed about 65 kg (143 pounds).
The MUSM-920 shell was found in 2005 along the margin of the Inuya River in Peru’s Fitzcarrald Arch region.
The second specimen, MUSM-5003, was found in 2010 in lignite deposits near Iquitos, in northern Peru.
Both are held at the Museo de Historia Natural of the Universidad Nacional Mayor de San Marcos in Lima.
“The MUSM-920 specimen represents the largest completely preserved shell ever recorded for the genus and species,” the scientists said.
“Its size is comparable to that of a partially preserved specimen from Brazil, which, based on the scale provided in the original study, measures 77.4 cm (2.5 feet) and was estimated to have reached approximately 90 cm (3 feet) in total length.”
“Together, these specimens represent the largest known chelid turtles on record.”
The finds extend the known range of Chelus colombiana, previously recorded in Colombia and Brazil, to the southwestern edge of the Pebas system, a huge complex of lakes, swamps and rivers that dominated western Amazonia during the Miocene.
The specimens fit a broader pattern of gigantism among Miocene turtles in northern South America, attributed to the wetland system’s size and connectivity rather than to climate.
“Fossil localities in Venezuela, Colombia, Brazil, and those newly identified in Peru continue to hold significant potential for yielding complete skeletons that could ultimately resolve the taxonomic controversy surrounding the fossil record of Chelus,” the authors said.
The findings appear in the October 2026 issue of the journal Palaeoworld.
_____
Edwin-Alberto Cadena et al. 2026. New fossil material of Chelus (Testudines: Chelidae) from the Middle Miocene of Peru. Palaeoworld 35 (5): 201135; doi: 10.1016/j.palwor.2026.201135