Cenozoic batoids from Contamana (Peruvian Amazonia) with focus on freshwater potamotrygonins and their paleoenvironmental significance

Biogeography of the neotropical freshwater stingrays (Myliobatiformes: Potamotrygoninae) reveals effects of continent‐scale paleogeographic change and drainage evolution

“…The special ecological circumstances of the Pebas are thought to have also spurred diversification in crocodylians(Salas- Gismondi et al, 2015) and mollusks(Nuttall, 1990). Supporting our arguments,Chabain et al (2017) show that proposed potamotrygonid fossil teeth recovered from the Oligocene-late Miocene from the Contamana region in Peru show morphological disparities that relate to ecological adaptations and diversification.The estimate for the age of origin of Potamotrygoninae (26 Ma) is older than the 23 Ma proposed byLovejoy et al (1998), but younger than the 38.2 (30.1-47.7) Ma proposed byBloom and Lovejoy (2017).However, all three of these estimates roughly coincide with the age of Miocene marine incursions and the Pebas wetlands, and the error estimate for the age proposed here (21 to 32 Ma) overlaps with these earlier estimates. Our age estimates for the Potamotrygoninae origin contrasts with older ages proposed by some authors based on fossil evidence.…”

“…We used four different dating priors in the BEAST2 analysis. We used the earliest-known proposed fossil for the potamotrygonine subfamily, Potamotrygon ucayalensis (Adnet et al, 2014) from the middle Eocene (∼41 Ma), and the fossils of P. contamanensis, P. canaanorum and P. rajachloeae (Chabain et al, 2017) from the late Oligocene-early Miocene (∼30-20 Ma). We assigned a log-normal distributed prior for the origin of the subfamily Potamotrygoninae using these fossils, and to accommodate date uncertainty, set this prior to have an offset of 20.0, standard deviation (S) of 0.75 and mean (M) of 12.0.…”

“…Based on the phylogenetic position of nonpotamotrygonine fossil stingrays from the Green River and Monte Bolca formations,Carvalho et al (2004) suggest that the origin of the potamotrygonines was older than the Oligocene-Miocene. Fossil evidence for Neotropical freshwater stingrays is scarce, mostly consisting of disarticulated teeth(Adnet et al, 2014;Chabain et al, 2017) Adnet et al (2014). studied stingray teeth from freshwater Eocene deposits from Contamana in the Peruvian Amazon (CTA-27) that they attributed to potamotrygonines; however, these teeth do not exhibit phylogenetically diagnostic characters for potamotrygonines and their classification depends on their freshwater provenance.Using ecological setting to determine the phylogenetic position of fossils is weakened by the fact that different lineages of stingrays have invaded freshwater habitats on multiple occasions.…”

“…studied stingray teeth from freshwater Eocene deposits from Contamana in the Peruvian Amazon (CTA-27) that they attributed to potamotrygonines; however, these teeth do not exhibit phylogenetically diagnostic characters for potamotrygonines and their classification depends on their freshwater provenance.Using ecological setting to determine the phylogenetic position of fossils is weakened by the fact that different lineages of stingrays have invaded freshwater habitats on multiple occasions. More recently,Chabain et al (2017) describe additional fossil stingray teeth from Oligocene-Miocene deposits also from Contamana…”

Contribution to the reappraisal of the mid Paleogene ichtyofauna of Western Africa with three new enigmatical elasmobranchs from Thanetian–Lutetian of Senegal

“…South American fossils of this subfamily drew particular attention this last decade (e.g. Brito and Deynat, 2004;Adnet et al, 2014;Chabain et al, 2017) with evidences that they were abundant in middle Eocene deposits of Peruvian Amazonia. In contrast, the living styracurines (amphi-American whipray) are less abundant.…”