And the first known jaw specimen of Stupendemys Geographicus, a species of side-neck freshwater turtle that lived 5-10 million years ago (Miocence period). ) in South America. Together, fossils shed new light on the biology, past distribution and phylogenetic position of the giant tortoise.
Reconstitution of Stupendemys Geographicus male (front) and female (center-left), with the giant alligator Purussaurus mirandai and the great catfish Phractocephalus nassi. Image credit: Jaime Chirinos.
Reconstitution of Stupendemys Geographicus male (front) and female (center-left), with the giant alligator Purussaurus mirandai and the great catfish Phractocephalus nassi. Image by Jaime Chirinos.
“Since the extinction of dinosaurs, northern neotropics have housed missing vertebrates today that were extremely large within their respective clades,” said team director Dr. Marcelo Sánchez, director of the Institute and Museum of Paleontology at the University of Zurich and colleagues.
“Among them are the largest snake, the alligator crocodile, the gavial and some of the largest rodents.”
“One of the most emblematic species of these species is the gigantic geographic turtle of Stupendemys, because it is the largest non-sea turtle ever known from a full shell.”
“Stupendemys Geographicus was first described in 1976 from the Urumaco formation in northwestern Venezuela, but our knowledge of this animal was based on partial specimens that led to a problematic taxonomy, in particular due to the lack of specimens with elements skull and shell associates. “
Paleontologist Rodolfo Sánchez and an 8 million-year-old shell of Stupendemys male geography of Urumaco, Venezuela.
Dr. Sánchez and his co-authors have discovered and examined new specimens of Stupendemys geography in the Urumaco region in Venezuela and in the La Tatacoa desert in Colombia.
The findings included the largest shell reported by any existing or extinct turtle, with a shell length of 2.4 m (8 feet) and an estimated mass of 1,145 kg, almost 100 times the size of its closest living relative.
“The shell of some Stupendemys Geographicus individuals has reached almost 3 m (10 feet), which makes it one of the largest turtles, if not the largest, that ever existed,” said Dr. Sanchez.
In some specimens, the researchers observed a particular and unexpected feature: the horns.
“The two types of shells indicate that there were two sexes of geographical Stupendemys: males with shells with horns and females with shells without horns,” said Dr. Sanchez.
“This is the first time that a sexual dimorphism in the form of horned shells has been reported for one of the lateral neck turtles, one of the two main turtle groups in the world.”
Scientists have also been able to review the evolutionary relationships of this species within the tree of life of the turtles.
“Based on studies on the anatomy of turtles, we now know that some live turtles in the Amazon region are the closest living relatives,” said Dr. Sánchez.
“In addition, new discoveries and research on existing fossils from Brazil, Colombia and Venezuela indicate a much wider geographical distribution of Stupendemys Geographicus than previously thought. The animal lived throughout the northern part of South America. “
“Despite its enormous size, the turtle had natural enemies,” the authors added.
“In many regions, the presence of geographical Stupendemys coincides with Purussaurus, the largest alligators.”
“It was probably a giant tortoise predator, not only for its size and food preferences, but also as suggested by bite marks and perforated bones in the fossilized shells of Stupendemys Geographicus.”