Journal of Paleontology, 89(5), 2015, p. 791–801 Copyright © 2016, The Paleontological Society 0022-3360/16/0088-0906 doi: 10.1017/jpa.2015.52


Kooiichthys jono n. gen. n. sp., a primitive catfish (Teleostei, Siluriformes) from the marine Miocene of southern South America


María de las Mercedes Azpelicueta,1 Alberto Luis Cione,2 Mario Alberto Cozzuol,3 and Juan Marcos Mirande4


1División Zoología Vertebrados, Museo de La Plata, 1900 La Plata, Argentina ⟨azpeli@gmail.com⟩ 2División Paleontología Vertebrados, Museo de La Plata, 1900 La Plata, Argentina ⟨acione@museo.fcnym.unlp.edu.ar⟩ 3Departamento de Zoologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Av. Antônio Carlos, 6627 Pampulha,


31270-910, Belo Horizonte, MG, Brazil ⟨mario.cozzuol@gmail.com⟩ 4Fundación Miguel Lillo, Miguel Lillo 251, San Miguel de Tucumán (4000), Tucumán, Argentina ⟨mcmirande@gmail.com⟩


Abstract.—A specimen of a remarkable new catfish genus and species was collected in middle/late Miocene marine beds of the Puerto Madryn Formation at the base of the marine cliff of the sea lion colony area near Puerto Pirámide, southern coast of Península Valdés, northeastern Patagonia, Argentina. Siluriforms (catfishes) constitute a most important monophyletic ostariophysan group of mainly freshwater fishes that occurs in almost all continents but it is especially diverse in South America. Catfishes are presently distributed in tropical to temperate areas and a small number of species are marine or amphibiotic. The new catfish shows many primitive features for catfishes in the maxilla, autopalatine, hyal elements, and Weberian apparatus. The genus is clearly distinguished by four autapomorphies: sand clock–shaped autopalatine, posterior limb of autopalatine widening strongly, post-articular arm of autopalatine longer, and a metapterygoid longer than broad. One tree was obtained both under equal and implied weighting with the following topology: a basal polytomy in the Siluriformes formed by Diplomystidae, Bachmanniidae, Kooiichthys and the Siluroidei. The new species appears to have been a marine or amphibiotic taxon: it was collected in beds considered to represent the Maximum Flooding Horizon of the transgression that deposited the Puerto Madryn Formation. The coast at this moment was at approximately 90 km to the west. According to faunistic evidence, the sea was warm temperate.


Introduction


Siluriformes (catfishes) comprise one of the most diverse vertebrate groups both morphologically and taxonomically (Fink and Fink, 1996; Nelson, 2006). Presently, there are approximately 37 families with almost 3,400 species in all continents except Antarctica (Ambruster, 2011). However, they inhabited Antarctica at least during the Eocene, when radically climatic conditions prevailed in the world (Grande and Eastman, 1986). Only a small number of catfishes (most of the ariids and many of the plotosids) are marine and some species of other families can enter brackish waters (Nelson, 2006). The most plesiomorphic catfishes in a morphological


sense are the living Diplomystidae of Patagonia and central Chile (Arratia, 1987; Azpelicueta, 1994) and the Eocene Bachmanniidae of Patagonia (Azpelicueta and Cione, 2011). The oldest fossils assignable to Siluriformes occur in the Campanian (late Cretaceous) of southern South America (Cione and Laffite, 1980; Cione, 1987). Moreover, South America is the only continent where catfishes are relatively common in Cretaceous rocks (Argentina: Cione and Lafitte, 1980; Cione et al., 1985; Arratia and Cione, 1996. Bolivia: Gayet and Meunier, 2003.Brazil: Bertini et al., 1993). The only extra–South American Cretaceous records are otoliths in North America


(Nolf and Stringer, 1996) and one spine from India (Cione and Prasad, 2002). South America is the continent where siluriforms are most


diverse and where the most primitive catfishes occur (Azpelicueta and Cione, 2011). Since the Cretaceous, lineage-splitting should have been coupled with many independent evolutionary experi- ments and ecological specializations. They are relatively common in Cenozoic rocks in the continent (Arratia and Cione, 1996; Azpelicueta and Cione, 2011). The discovery of the present catfish in Miocene beds of Patagonia deserves special attention; unfortunately, only the anterior part of the neurocranium, great part of visceral skeleton, anterior vertebrae, and great part of pectoral girdle were preserved. No other material was collected despite repeated collecting visits to the area. In this paper, we describe the new genus and species and


discuss its relationships based on morphological features with the most primitive siluriform taxa and the rest of catfishes.


Stratigraphy


The fossil-bearing bed is formed of muddy sandstones included in the Puerto Madryn Formation (Fig. 1). These beds were deposited during the late part of the extensive marine encroachment that lasted from the late Oligocene until the late


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