New materials and an overview of Cretaceous vertebrates from the Chubut Group of the Golfo San Jorge Basin, central Patagonia, Argentina

https://doi.org/10.1016/j.jsames.2019.102460Get rights and content

Highlights

  • South-central Patagonia preserves a rich and important vertebrate fossil record.

  • New materials described augment our understanding of Cretaceous vertebrate.

  • The information mentioned constitutes an important source for future comparisons.

Abstract

In this paper, we present an updated revision of fossil vertebrates from the Chubut Group, Golfo San Jorge Basin, while also describing some new remains. Extensive exposures of both Lower and Upper Cretaceous sedimentary sequences are present in central Patagonia. These outcrops have, over the past several decades, yielded a varied vertebrate fauna, including fishes, turtles, crocodyliforms, pterosaurs, and dinosaurs, currently herein characterized and described. Although vertebrate diversity in the Chubut Group in central Patagonia is remarkable, the most abundant vertebrates recovered are dinosaurs. The Matasiete Formation (Hauterivian?–Albian) is markedly less prolific in terms of fossils discoveries than either the Bajo Barreal Formation (Cenomanian–early Turonian) or the recently recognized Lago Colhué Huapi Formation (Coniacian–Maastrichtian). The Bajo Barreal fauna is, at a high level, typical of coeval Gondwanan faunas. However, interestingly, several taxa occupy a basal position within their respective groups. The Lago Colhué Huapi Formation has produced a more derived vertebrate fauna, again similar to those from other Gondwanan regions. Finally, in a broad context, the new materials described augment our understanding of Cretaceous terrestrial vertebrate assemblage of central Patagonia and add to the generally meager record of vertebrate in the Cretaceous of the Southern Hemisphere.

Introduction

South-central Patagonia (Chubut Group; Golfo San Jorge Basin) preserves a rich and important vertebrate fossil record (Casal et al., 2016). Although this record is mostly represented by dinosaurs, other vertebrates have also been discovered with increasing frequency (Ibiricu et al., 2012a; Casal et al., 2016; Lamanna et al., 2019). Many of these discoveries were made by the Laboratory of Paleontology of the Universidad Nacional de la Patagonia San Juan Bosco (UNPSJB), who worked systematically in the area for more than 30 years.

The continental sediments of the Chubut Group are exposed over a vast area in the Golfo San Jorge Basin (central Patagonia; Fig. 1). Cretaceous continental strata carriers of fossil remains in the basin (in ascending order) include the Matasiete, Bajo Barreal, and Lago Colhué Huapi formations (see Casal et al., 2015, 2016, Fig. 2). Many fossil vertebrates have been recovered from these units, and have been described by some of the authors of this work (Table 1 and Table 2).

This contribution review the major vertebrate groups found in the Cretaceous Chubut Group of the Golfo San Jorge Basin, and describe new fossil vertebrate remains as well. This contribution is significant because it greatly enhances our understanding of the central Patagonia Cretaceous fossil vertebrate record through the description of new fossil specimens and revision of those already described.

Section snippets

Geologic context of south-central Patagonia, Chubut Group

The Golfo San Jorge Basin is an intraplate extensional basin on the South American plate (Fitzgerald et al., 1990), with its long axis running east-west. The Chubut Group (Lesta and Ferello, 1972) encompasses a significant section of the Cretaceous sedimentary sequence of the basin, originally divided into five formations: Pozo D-129, Matasiete, Castillo, Bajo Barreal and Laguna Palacios formations. The Pozo D-129 Formation is of lacustrine origin, whereas the Matasiete, Castillo, Bajo Barreal,

Localities

The south-central region of Chubut Province, Argentina, hosts excellent outcrops of the continental Cretaceous sedimentary sequences deposited in the Golfo San Jorge Basin (Fig. 1). As mentioned above, the fossiliferous units summarized herein are, in ascending age order, the Matasiete, Bajo Barreal and Lago Colhué Huapi formations (Fig. 2). These Cretaceous strata are extensively exposed in several localities across south-central Chubut Province, south-central Patagonia, Argentina. These

Institutional abbreviations

CPPLIP, Centro de Pesquisas Paleontológicas Llewellyn Ivor Price, Minas Gerais, Brazil; MACN, Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”, Buenos Aires, Argentina; MDT, Museo “Desiderio Torres”, Sarmiento, Chubut, Argentina; MMCH, Museo Municipal “Ernesto Bachmann”, Villa El Chocón, Neuquén, Argentina; MLP, Museo de La Plata, La Plata, Argentina; MPM, Museo Padre Manuel Jesús Molina, Rio Gallegos, Santa Cruz, Argentina; UCPC, University of Chicago Paleontological Collection,

Vertebrates from the Matasiete Formation (Early Cretaceous, Hauterivian?–Aptian; Lesta and Ferello, 1972, but see Paredes et al., 2007)

  • Titanosauriformes (Salgado et al., 1997a)

  • Titanosauriformes indet. (This paper)

  • Material. Right scapula (UNPSJB-PV 408; Fig. 3)

Remarks. The Early Cretaceous vertebrate fossil record in Argentina in general, and in central Patagonia in particular, is scarce compared with the Mid- and Late Cretaceous record. Therefore, any new vertebrate remains derived from Lower Cretaceous strata are potentially important and informative. In light of this, herein we describe a fragmentary, and isolated right

Vertebrates from the Bajo Barreal Formation (Cenomanian–lower Turonian; see Casal et al., 2015)

  • Rebbachisauridae (Bonaparte, 1997)

  • Katepensaurus goicoecheai (Ibiricu et al., 2013a, 2015)

  • Holotype. UNPSJB-PV 1007

An associated partial skeleton including: a fragment of the right frontal, three anterior to middle cervical vertebrae, an incomplete anterior dorsal vertebra, an incomplete anterior to middle dorsal vertebra, three middle to posterior dorsal vertebrae, an incomplete anterior to middle dorsal neural arch, an indeterminate neural arch fragment and partial cervical ribs, five

Vertebrates from the Lago Colhué Huapi Formation (Coniacian–Maastrichtian; Casal et al., 2015)

  • Titanosauria (Bonaparte and Coria, 1993)

  • Aeolosaurus colhuehuapensis (Casal et al., 2007)

  • Holotype. UNPSJB-PV 959. Partial skeleton including 21 articulated caudal vertebrae from the anterior to the middle section and seven haemal arches.

Remarks. Aeolosaurine titanosaurs were widely distributed in South America during the Late Cretaceous, with a decent fossil record in both Brazil and Argentina (Salgado and Bonaparte, 2007). Aeolosaurines are characterized by anteriorly inclined anterior and

Discussion and concluding remarks

The vertebrate assemblage of the Chubut Group of south-central Patagonia is rich and abundant. Although it mostly comprises dinosaur remains, other vertebrates are also present and have enhanced our understanding of vertebrate distribution and evolution as a whole. The Early Cretaceous, specifically the Hauterivian?–Albian interval in south-central Patagonia, is represented by extensive and well-exposed outcrops of the Matasiete Formation. The fossil record of this formation is scarce when

CRediT authorship contribution statement

Lucio M. Ibiricu: Conceptualization, Methodology, Investigation, Formal analysis, Writing - original draft, Writing - review & editing. Gabriel A. Casal: Conceptualization, Methodology, Investigation, Formal analysis, Writing - original draft. Rubén D. Martínez: Formal analysis. Bruno N. Alvarez: Formal analysis. Stephen F. Poropat: Formal analysis, Writing - original draft.

Declaration of competing interest

The authors of this works do not have conflict of interest.

Acknowledgments

We are indebted to M. Luna (Head of fossil preparation and field extraction) for their assistance and excellent work for more than 20 years. We also thank M. Lamanna (Carnegie Museum) for the continued support and work with the team of UNPSJB for several years. To all the students, mainly from UNPSJB, who participated in several of the field seasons, especially we thank E. Ivany for its constant field collaboration. The owners of the ranches (flias: Martínez, Salgao, Cretton, Perujo, Insua,

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