The first spinicaudatan (Crustacea: Diplostraca) from Permo-Triassic continental sequences of South America and its palaeoecological context

Abstract

Tassi, L.V., Monti, M., Gallego, O.F., Zavattieri, A.M. & Lara, M.B., 2013. The first spinicaudatan (Crustacea:Diplostraca) from Permo-Triassic continental sequences in South America and its palaeoecological context. Alcheringa 37, 187–199. ISSN 0311-5518.

Cornia martinsnetoi sp. nov., the first spinicaudatan from Permian–Triassic continental sequences of southern South America, is described. The new species has characters diagnostic of the typical late Palaeozoic–Early Triassic subfamily Vertexiinae from Gondwana. This new taxon was found in tuffaceous siltstones in the upper part of the Quebrada de los Fósiles Formation (Puesto Viejo Group), which may span the Permo-Triassic boundary in Argentina. The lower and coarser-grained interval of the Quebrada de los Fósiles Formation was deposited in distal alluvial fans and low- to high-sinuosity rivers. The upper fine-grained interval of this formation, which hosts the spinicaudatans and associated fossils (ostracods, megaspores, fish scales), was deposited in shallow floodplain lakes. Intense volcanic activity influenced the sedimentary evolution of this succession and was accompanied by aridification and some climatic seasonality that likely generated stressful conditions for the biota. Previous biostratigraphic studies support an Early Triassic age for the beds containing Cornia martinsnetoi sp. nov.

[Lara Vaz Tassi [larinhatassi@hotmail]com], Área Paleontología (Centro de Ecología Aplicada del Litoral—Centro Científico Tecnológico Nordeste—Consejo Nacional de Investigaciones Científicas y Técnicas), Casilla de Correo 128, 3400 Corrientes, Argentina; Mariana Monti [[email protected]], Departamento de Geología, Museo de Historia Natural de San Rafael—Parque Mariano Moreno s/n°, 5600 San Rafael, Mendoza, Argentina; Oscar Florencio Gallego [[email protected]], Micropaleontología (Facultad de Ciencias Exactas y Naturales y Agrimensura—Universidad Nacional del Nordeste), Corrientes, Argentina and Área Paleontología (Centro de Ecología Aplicada del Litoral—Centro Científico Tecnológico Nordeste—Consejo Nacional de Investigaciones Científicas y Técnicas), Casilla de Correo 128, 3400 Corrientes, Argentina; Ana María Zavattieri [[email protected]], Laboratorio de Paleopalinología (Instituto Argentino de Nivología y Glaciología y Ciencias Ambientales—Centro Científico Tecnológico—Consejo Nacional de Investigaciones Científicas y Técnicas), Casilla de Correo 131, 5500 Mendoza, Argentina; Maria Belén Lara [[email protected]], Área Paleontología (Centro de Ecología Aplicada del Litoral—Centro Científico Tecnológico Nordeste—Consejo Nacional de Investigaciones Científicas y Técnicas), Casilla de Correo 128, 3400 Corrientes, Argentina. Received 3.5.2012; revised 22.8.2012; accepted 11.9.2012.

本文描述了南美南部二叠纪-三叠纪陆相地层中首次发现的有刺有尾两栖动物的一个新种Corniamartinsnetoi sp. nov.。新种具有冈瓦纳大陆典型的晚古生代至早三叠世亚科Vertexiinae的标准特征。这个新分类群发现于Quebrada de los Fósiles组(Puesto Viejo群)上部的凝灰质粉砂岩中, 这个层位可能跨阿根廷二叠纪-三叠纪界线。Quebrada de los Fósiles组下部较粗粒地层沉积于冲积扇和弯度低至高的河流中; 而上部细粒地层含有刺尾两栖动物及相关化石(介形虫、大孢子、鱼鳞), 沉积于浅冲积平原湖泊中。强烈的火山活动影响了地层的沉积演变, 与此并存的是干燥作用和一些气候季节性变化, 导致对生物群极不利的环境。根据以前的生物地层研究, 我们将含该新种的地层确定为早三叠世。

Key words:

• Spinicaudata
• Conchostraca
• Permo-Triassic
• Puesto Viejo Group
• San Rafael Block
• Argentina

Acknowledgements

The authors would like to especially thank Marcelo de la Fuente (PICT-2007-00373) for providing access and logistics for the fieldwork and useful comments on the manuscript. We also thank Shekhar Ghosh for his guidance and suggestions for the description of the new species. Special thanks to the journal reviewers, Jean Vannier and Heinz Kozur and also to the Editor Stephen McLoughlin for their detailed suggestions that improve the manuscript. This contribution was partially supported by the Consejo Nacional de Investigaciones Científicas y Técnicas, Secretaría General de Ciencia y Técnica, Universidad Nacional del Nordeste and by the Agencia Nacional de Promoción Científica y Tecnológica (Grants PI-64/04 and PI-075/07 and PI-2010/F022; PIP-CONICET 5581; PICTOUNNE 0226/07). Biol. Victoria Zavattieri is thanked for compiling the line drawings.