The intriguing Atacamichthys fish from the Middle Jurassic of Chile ? an amiiform or a teleosteomorph?

ARRATIA, G.; SCHULTZE, H-P.; GOUIRIC CAVALLI, SOLEDAD; QUEZADA-ROMEGIALLI, CLAUDIO

Ancient Fishes and their Living Relatives: a Tribute to John G. Maisey

Verlag Friedrich Pfeil

Año: 2021; p. 19 - 36

The Oxfordian El Profeta Formation in northern Chile was an important place of teleosteomorph or stem teleostean diversification in the southern Paleo-Pacific Ocean. Among the diverse fish fauna recovered in this formation is ?Atacamichthys greeni, which exhibits an interesting combination of amiiform and teleostean morphological features. As a consequence, the fish has been interpreted as a?caturid-like fish? or Halecostomi incertae sedis or a teleost incertae sedis in the past, but a phylogenetic analysis was missing. This paper re-examines the morphological characters of ?Atacamichthys, and the phylogenetic position of the fish is investigated using a pre-existing data matrix whose characters were re-polarized using more distant phylogenetic outgroup taxa, e. g., ?Birgeria, and Polypterus. The new results suggest ?Atacamichthys greeni is a teleosteomorph or stem teleost placed above the phylogenetic level of ?Prohalecites and below that of ?Pholidophoridae. Changes in the outgroup taxa did not affect the position of ?Atacamichthys. ?Atacamichthys greeni is suggested as a member of ?Atacamichthyidae new family, which is supported by a combination of morphological characters differentiating it from other Jurassic families worldwide and increasing the endemism of the fish faunas of the Paleo-Pacific Ocean during the Jurassic.