A new genus of coccolepidid fishes (Actinopterygii, Chondrostei) from the continental Jurassic of Patagonia

Abstract

Jurassic freshwater fish faunas are still poorly known, with the only assemblage of that age known from southern South America being the "Almada fauna" of the Cañadón Calcáreo Formation (Oxfordian-Tithonian) of Chubut, Argentina. This fauna is composed mainly by abundant teleosts and a much rarer basal actinopterygian, originally described as †Oligopleurus groeberi and currently usually placed in the genus †Coccolepis. This taxon is here redescribed on the basis of the original specimens and more numerous and better preserved new material from several localities within the Cañadón Calcáreo Formation. The species shows several differences to other coccolepidid taxa, including the apomorphic presence of a sensory canal in the gular plate, and cannot be referred to a known genus. Thus, a new genus name, †Condorlepis gen. nov., is proposed. The detailed anatomical description of †Condorlepis gen. nov. groeberi provides further evidence for the chondrostean affinities of the Coccolepididae and their close relationships with the Acipenseriformes, since this species shows six characters that were hitherto considered to be autapomorphies of the latter clade. A comparison of the Almada fauna with other Gondwanan Jurassic freshwater fish faunas shows close similarities with the roughly contemporaneous fauna of Talbragar, Australia, which also includes an abundant basal teleost and coccolepidids. In contrast, there are marked differences with the faunas of the Early to Middle Jurassic Kota Formation of India, the Late Jurassic to Early Cretaceous Stanleyville beds of the Democratic Republic of the Congo, and the probably Late Jurassic Tacuarembó Formation of Uruguay, in which basal, non-teleostean neopterygians and sarcopterygians are abundant.

U-Pb and Lu-Hf zircon geochronology of the Cañadón Asfalto Basin, Chubut, Argentina: Implications for the magmatic evolution in central Patagonia

“…8). The fauna of the La Manea locality includes the spinicaudatan Congestheriella rauhuti (Gallego et al, 2010), and fish species, Luisiella feruglioi (Bordas, 1943) and Condorlepis groeberi (Bordas, 1943) Arbarello et al, 2013;Monferran et al, 2016). This fossil record is also consistent with an Oxfordian to Tithonian age.…”

“…At the top of the section occurs an intercalation of sandstones with silicified tree trunks in life position (Cabaleri et al, 2010a). Tuffs, sandy tuffites, and red, laminated sandstones and rhythmites with fish remains (López-Arbarello, 2004;López-Arbarello et al, 2013) cover these sandstones. The Puesto Almada Member has been bracketed between the Callovian and the Tithonian (Cabaleri et al, 2010b;Gallego et al, 2011;Hauser et al, 2012), which is supported by dinosaur remains, ostracods and spinicaudatan associations from the Late Jurassic (Musacchio et al, 1990;Musacchio, 1989Musacchio, , 1995Musacchio, , 2001Rich et al, 1999;Rauhut et al, 2005;Gallego et al, 2011;Monferran et al, 2013).…”

New holostean fishes (Actinopterygii: Neopterygii) from the Middle Triassic of the Monte San Giorgio (Canton Ticino, Switzerland)

“…The processus ascendens anterior is related to the processus basypterigius of the endochondral neurocranium ( Stensiö , 1932 : 273; Nielsen , 1942 : 105, 324), and it is thus usually referred to as the basypterigoid process of the parasphenoid (e.g., Gardiner , 1984 ), especially in neopterygians (e.g., Patterson , 1975 ; Grande & Bemis , 1998 ; Grande , 2010 ). The precessus ascendens anterior is poorly developed in several taxa including Pteronisculus and Boreosomus ( Nielsen , 1942 ; Lehman , 1952 ), and Amia and other halecomorphs ( Jarvik , 1980 ; Grande & Bemis , 1998 —their pterosphenoid process of the parasphenoid), and it is absent in several actinopterygians including the chondrosteans Birgeria ( Nielsen , 1949 ), Condorlepis ( López-Arbarello, Sferco & Rauhut , 2013 ), Chondrosteus ( Hilton & Forey , 2009 ), and Acipenser ( Hilton, Grande & Bemis , 2011 ), but also in Australosomus ( Nielsen , 1949 ) and Perleidus ( Stensiö , 1932 ; Lehman , 1952 ). The two species of Ticinolepis differ in the degree in which the basipterygoid processes of the parasphenoid are developed.…”

Environmental and climatic proxies for the Cañadón Asfalto and Neuquén basins (Patagonia, Argentina): review of Middle to Upper Jurassic continental and near coastal sequences

“…These rhythmites are characteristic from the Puesto Almada Member and are well represented in the outcrops at Estancia El Torito (type locality), Sierra de la Manea, Cañadón de los Chivos, and Puesto de Limonao localities (Figure1 C). They are known by their fi sh content (Coccolepis groeberi Bordas, Tharrias feruglioi Bordas, and Luisiella inexcutata Bocchino) since the publications of Bordas (1942) and Bocchino (1967), and also mentioned in a modern synthesis of López-Arbarello (2004) and López-Arbarello et al (2013). However, the latter authors consider the fi sh bearing strata as belonging to the overlying Cañadón Calcáreo Formation and not to the Puesto Almada Member of the Canadón Asfalto Formation as Cabaleri et al (2010b) proposed.…”