New insights on the anatomy and ontogeny of the largest extinct freshwater turtles

Abstract

There are many questions regarding the largest freshwater turtle that ever existed, including how its morphology changed during its ontogeny and how a single ecosystem was able to support more than one group of giant turtles. Here, we report the first individual preserving an associated skull and shell for Stupendemys geographica (currently the largest known side-necked turtle) and a nearly complete skull of Caninemys tridentata found in Miocene rocks of the Tatacoa Desert in Colombia. These two specimens indicate that more than two large freshwater turtle species shared a single ecosystem during the middle Miocene in northern South America. We also show the changes in the shell and scutes that occurred along the ontogeny of S. geographica , including a flattening of the carapace, constriction of the vertebral scutes, and increase in the height and thickness of the nuchal upturn wall; some of these changes are also evident in extant representatives of Podocnemididae , and have implications for a better understanding of their phylogeny.

The latest freshwater giants: a new Peltocephalus (Pleurodira: Podocnemididae) turtle from the Late Pleistocene of the Brazilian Amazon

“…dumerilianus; electronic supplementary material, figure S7) implies a less carnivorous diet. Size difference has been proposed to explain the coexistence of the Miocene Caninemys tridentata and S. geographica [10] and could also prevent ecological competition among extant Amazon podocnemidids, which were likely living during the Late Pleistocene [24,25]. The 27.8 cm long dentaries of Pe.…”

“…We modified a recent matrix of Pleurodira [ 10 ] by incorporating some characters from Evers et al . [ 11 ], as well as three new characters.…”

“…We modified a recent matrix of Pleurodira [10] by incorporating some characters from Evers et al [11], as well as three new characters. We scored MERO.PV.H 007, excluded most non-Podocnemidoidae, using TNT v. 1.5 [12] (detailed descriptions on electronic supplementary material, file S1).…”

The Miocene La Venta Biome (Colombia): A century of research and future perspectives

“…Selection of fossils from La Tatacoa Desert housed at the Museo de Historia Natural La Tatacoa , including some specimens featured in this thematic issue: A , Lepidosiren paradoxa (VPPLT 1483); B , parieto-supraoccipital frontal fragment of Phractocephalus sp. (VPPLT 1272; Carrillo-Briceño et al 2023); C , skull of Purussaurus neivensis; D , skeleton of Caimaninae; E , skull of Caninemys tridentata Meylan, Gaffney & de Almeida Campos, 2009 (VPPLT-1720; Cadena et al 2021); F , shell of Podocnemis tatacoensis Cadena & Vanegas, 2023 (VPPLT 1727; Cadena & Vanegas 2023); G , skull of Miocochilius anomopodus Stirton, 1953 (VPPLT 1512); H , skull of “ Prodolichotis” pridiana Fields, 1957 (VPPLT 1614); I , skull of Anachlysictis gracilis Goin, 1997 (VPPLT 1612; Suarez et al 2023); J , partial mandible of Megadolodus molariformis McKenna, 1956 (VPPLT 974; Carrillo et al 2023); K , skull of Cebupithecia sarmientoi Stirton & Savage, 1950. Abbreviation: VPPLT , Vigías del Patrimonio Paleontológico La Tatacoa.…”

“…Turtles represent one of the most abundant fossil vertebrate finds in the La Venta fauna, including nearly complete specimens or shell fragments from various localities and stratigraphic horizons throughout the entire region (Wood 1997). To date, both major groups of extinct and living turtles – the cryptodirans or hidden-necked, and the pleurodirans or side-necked turtles – have been recorded (Wood 1997; Cadena et al 2020a, b, 2021, 2023; Cadena & Vanegas 2023). Currently, a revision based on new specimens of Chelonoidis is underway, as well as the description of a new genus and species of podocnemidid, showing that our knowledge of the paleodiversity of turtles that inhabited this region during the Middle Miocene is far from complete.…”