Corydoras revelatus explained

Corydoras revelatus is an extinct species of callichthyid catfish known from a single specimen found in Late Paleocene strata of the Mais Gordo Formation in Salta, Argentina. According to chronological dating of the strata, the fossil specimen is about 58.2–58.5 million years old.^{[1] [2]}

Compared to modern species, C. revelatus has a short, comparatively rounded head, and rather low-set eyes. Although the species's position within the genus Corydoras is tentative and unresolved, its anatomy confirms that it is a member of the subfamily, Corydoradinae, and demonstrates that the callichthyids had already diverging or diversifying before the end of the Paleocene.^{[1] [2]}

Corydoras revelatus is the oldest known definitive fossil loricarioid.^[2] The Moroccan Afrocascudo, deriving from the Late Cretaceous (Cenomanian, ~100–95 Ma) Kem Kem Group, has been initially described as the oldest known member in 2024.^[3] Some researchers suggest that this taxon might actually represent a juvenile obaichthyid lepisosteiform, possibly a junior synonym of Obaichthys,^[4] though this has been disputed based on the complete ossification of the bones indicating full maturity and the absence of important holostean characters.^[5]

Notes and References

1. Cockerell . T. D. A. . 1925-10-30 . A Fossil Fish of the Family Callichthyidae . . en . 62 . 1609 . 397–398 . 10.1126/science.62.1609.397.c . 0036-8075.
2. Lundberg . John G. . Sullivan . John P. . Rodiles-Hernández . Rocío . Hendrickson . Dean A. . 2007-06-01 . Discovery of African roots for the Mesoamerican Chiapas catfish, Lacantunia enigmatica, requires an ancient intercontinental passage . . 156 . 1 . 39–53 . 10.1635/0097-3157(2007)156[39:DOARFT]2.0.CO;2 . 0097-3157. https://web.archive.org/web/20090326130159/https://webspace.utexas.edu/deanhend/www/pdfs/Lundberg_2007_African_roots_Lacantunia.pdf . 2009-03-26 .
3. Brito . Paulo M. . Dutheil . Didier B. . Gueriau . Pierre . Keith . Philippe . Carnevale . Giorgio . Britto . Marcelo . Meunier . François J. . Khalloufi . Bouziane . King . Andrew . de Amorim . Pedro F. . Costa . Wilson J. E. M. . A Saharan fossil and the dawn of Neotropical armoured catfishes in Gondwana . 2024 . . 132 . 103–112 . 10.1016/j.gr.2024.04.008 . 2024GondR.132..103B .
4. Britz, R.. Pinion, Amanda K.. Kubicek, Kole M.. Conway, Kevin W.. 2024. Comment on “A Saharan fossil and the dawn of Neotropical armoured catfishes in Gondwana” by Brito et al. Gondwana Research. 10.1016/j.gr.2024.06.014.
5. Brito . Paulo M. . Dutheil . Didier B. . Keith . Philippe . Carnevale . Giorgio . Meunier . François J. . Khalloufi . Bouziane . Gueriau . Pierre . 2024. A reply to a comment on Brito et al., 2024, A Saharan fossil and the dawn of the Neotropical armoured catfishes in Gondwana by Britz, Pinion, Kubicek and Conway. Gondwana Research. 10.1016/j.gr.2024.06.013.