First record of Pachycormiformes (Osteicththyes, Actinopterygii) from the Mesozoic of Antarctica and the past distribution of the suspension-feeding clade

GOUIRIC CAVALLI, SOLEDAD; RASIA, LUCIANO LUIS

Congreso; Congreso de la Asociación Paleontológica Argentina; 2016

The ecospace (=mode of life) combines key ecological parameters and do not implies limiting conditions, resources or competition among species; evaluating how many of the potential modes of life that could exist were actually present in a particular regional or temporal framework. The modern vertebrate suspension feeding ecospace includes baleen whales (mysticetes), some sharks (whale shark, megamouth, and basking sharks), mobulid rays, and some seals (crabeater and leopard seals). The Mesozoic vertebrate suspension-feeding ecospace was mainly occupied by a clade of actinopterygian fishes: the suspension-feeder Pachycormiformes. During the Jurassic, this clade is represented by three genera: Leedsichthys Woodward, 1889 and Asthenocormus Wagner, 1863, and Martillichthys Liston, 2008; while in the Cretaceous they are represented by two: Rhinconichthys Friedman, Shimada, Martin, Everhart, Liston, Maltese, and Triebold, 2010, and Bonnerichthys Friedman, Shimada, Martin, Everhart, Liston, Maltese, and Triebold, 2010. In the Southern Hemisphere, isolated and scattered suspension-feeder pachycormiform remains were reported for the Late Jurassic of Chile and Argentina. During the last years of Antarctic field expeditions to Marambio (=Seymour) Island and the Antarctic Peninsula, pachycormiform remains referred here to suspension-feeders were recovered in Upper Cretaceous levels of the Lopez de Bertodano Formation and Upper Jurassic levels of the Ameghino (=Nordenskjöld) Formation. In accordance with these new Antarctic reports, suspension-feeder pachycormiforms shows a wider distribution during the Late Jurassic and Late Cretaceous than previously known. This new reports may help to have a better understanding about the evolutionary and paleobiogeographic history of suspension-feeder pachycormiforms.