Elsevier

Cretaceous Research

Volume 37, October 2012, Pages 191-200
Cretaceous Research

A new peirosaurid from the Upper Cretaceous of Argentina: Implications for specimens referred to Peirosaurus torminni Price (Crocodyliformes: Peirosauridae)

https://doi.org/10.1016/j.cretres.2012.03.017Get rights and content

Abstract

Two crocodyliform specimens recovered from the Upper Cretaceous of Argentina and originally referred to Peirosaurus torminni Price from Minas Gerais State, Brazil are reassigned to Gasparinisuchus peirosauroides gen. et sp. nov. No unique features are shared between the Brazilian and Argentinian specimens and many traits, including the presence of five premaxillary teeth, a noticeably smooth perinarial region, a lateral notch at the premaxilla–maxilla contact for the reception of an enlarged anterior dentary tooth, and the shape of the external nares, are widely distributed among peirosaurids and, in some cases, other mesoeucrocodylians. Though overlapping elements are limited to the premaxilla and the dentition, the broad, rounded rostrum, anteroposteriorly short premaxilla, reduced perinareal fossa, and short premaxillary interdental spaces in Gasparinisuchus differentiate it from P. torminni. Additionally, Gasparinisuchus is unique among peirosaurids for its broad rostrum and apparent absence of an antorbital fenestra. Reassignment of the Argentinian material formerly referred to Peirosaurus therefore removes one of the few specific links between the Cretaceous terrestrial biotas of Brazil and Argentina.

Highlights

► Re-analyses of crocodyliform specimens originally referred to Peirosaurus torminni. The material is reassigned to new genus and species: Gasparinisuchus peirosauroides. ► Peirosaurus torminni is no longer present in the Late Cretaceous of Argentina.

Introduction

Peirosaurid crocodyliforms represent a relatively common component of many Cretaceous terrestrial faunas known from Gondwana. At present, South American members of Peirosauridae include at least seven taxa: Barcinosuchus gradilis (Leardi and Pol, 2009), Itasuchus jesuinoi (Price, 1955), Lomasuchus palpebrosus (Gasparini et al., 1991), Montealtosuchus arrudacamposi (Carvalho et al., 2007), Peirosaurus torminni (Price, 1955), Pepesuchus deiseae (Campos et al., 2011), and Uberabasuchus terrificus (Carvalho et al., 2004). These taxa are thus far restricted to the Cretaceous (Aptian–Maastrichtian) of Argentina and Brazil, with the Late Cretaceous taxon Peirosaurus torminni representing the only peirosaurid common to both countries (Gasparini, 1982; Gasparini et al., 1991; but see below). African taxa include Hamadasuchus rebouli (Buffetaut, 1994; Larsson and Sues, 2007) from the Albian–Cenomanian of Morocco and Stolokrosuchus lapparenti (Larsson and Gado, 2000) from the Aptian of Niger, though several recent studies (e.g., Lapparent de Broin, 2002; Carvalho et al., 2007; Turner and Buckley, 2008) exclude Stolokrosuchus from Peirosauridae. The broad-snouted crocodyliform Mahajangasuchus insignis (Buckley and Brochu, 1999; Turner and Buckley, 2008) from the Maastrichtian of Madagascar was originally described as a potential peirosaurid, though more recent phylogenetic analyses exclude it from this clade (e.g., Turner, 2006; Carvalho et al., 2007; Larsson and Sues, 2007; Turner and Buckley, 2008; Sereno and Larsson, 2009; Turner and Sertich, 2010). An additional taxon from these same deposits in Madagascar, Miadanasuchus oblita (Buffetaut and Taquet, 1979; Simons and Buckley, 2009), may also represent a peirosaurid taxon, though currently described specimens are too fragmentary for a confident assignment.

Within Peirosauridae, little consensus exists regarding ingroup relationships, specifically the phylogenetic position of African taxa relative to South American taxa from which the family was originally established (Gasparini, 1982). Additionally, the phylogenetic position of Peirosauridae within Mesoeucrocodylia is still poorly resolved. Among widely divergent recent phylogenetic hypotheses, Peirosauridae has been recovered as the sister-group of Neosuchia (e.g., Pol and Apesteguía, 2005; Gasparini et al., 2006; Turner and Buckley, 2008; Leardi and Pol, 2009); nested within the clade Sebecia, closely related to sebecid crocodyliforms (e.g., Sebecus and Bretesuchus) (Larsson and Sues, 2007); included in a clade with Mahajangasuchus, Trematochampsa, and Araripesuchus spp. (Turner, 2006); recovered within Neosuchia (Sereno and Larsson, 2009); or recovered within Notosuchia (Carvalho et al., 2004; Turner and Sertich, 2010). The phylogenetic relationships of Peirosauridae among mesoeucrocodylians are beyond the scope of this project and will not be discussed here.

Originally described by Price (1955), Peirosaurus torminni (Mesoeucrocodylia, Peirosauridae) is based upon a single fragmentary specimen, DGM-433-R. This specimen was discovered at the site known as “Ponto 2 do Price”, near the rural town of Peirópolis (Uberaba County, Minas Gerais State, Brazil), in the Serra da Galga Member, Marília Formation (Bauru Group, Maastrichtian). The holotype of P. torminni (DGM-433-R) consists of the left premaxilla with five teeth (Fig. 1), various associated, isolated teeth, the right palpebral, and many postcranial elements (i.e., radius, ulnae, fragments of the ischia and pubis, vertebrae, ribs, chevrons, and osteoderms). Of these elements, only the premaxilla, selected teeth, and osteoderms have been figured (Price, 1955; Marinho et al., 2006).

Subsequent to the original description of Peirosaurus torminni by Price (1955), cranial and postcranial remains (MOZ 1750 PV; Fig. 2, Fig. 3, Fig. 4, Fig. 5) from Loma de la Lata, Neuquén Province, Argentina (Bajo de la Carpa Formation, Santonian, Neuquén Group; Calvo and Porfiri, 2010; Garrido, 2010) were referred to the Brazilian taxon. In addition, incomplete cranial remains (PV-CRIDC-12) were preliminarily described and tentatively assigned to P. torminni by Praderio et al. (2009; see Fig. 6). This material, which also includes undescribed postcranial elements, was recovered from the area known as Cañadón Amarillo, in the southernmost region of Malargüe District, Mendoza Province, Argentina (Praderio et al., 2009), from the Santonian Anacleto Formation of the Neuquén Group.

The referral of specimen MOZ 1750 PV from the Upper Cretaceous of Argentina to Peirosaurus torminni greatly enhanced the anatomical and taxonomic understanding of the species, providing the basis for Gasparini (1982) to define Peirosauridae. Following the comprehensive description of this material (Gasparini, 1982; Gasparini et al., 1991), the presence of P. torminni in both the Santonian of Argentina and Maastrichtian of Brazil was widely accepted. Additionally, the nearly complete skull of MOZ 1750 PV has become the primary source of phylogenetic information for P. torminni in most analyses of mesoeucrocodylian relationships.

The holotype of Peirosaurus torminni (DGM-433-R) and the primary referred Argentinian material (MOZ 1750 PV) unfortunately share very few overlapping elements (the premaxilla and the dentition). The recent description of several new South American peirosaurid taxa (e.g., Uberabasuchus, Montealtosuchus) have demonstrated that previously apomorphic features shared by the Argentinian and Brazilian specimens of P. torminni have a broader distribution among mesoeucrocodylians. Detailed reinvestigation and re-evaluation of putative features shared between P. torminni (holotype, DGM-433-R) and referred Argentinian specimens (MOZ 1750 PV and PV-CRIDC-12) indicate substantial differences. Thus, critical re-examination of material referred to P. torminni and evaluation of their taxonomic status is undertaken here. Furthermore, a preliminary discussion of the taxonomy of peirosaurid taxa from Peirópolis (Minas Gerais State, Brazil) is also undertaken.

Institutional abbreviations. CPPLIP, Centro de Pesquisas Paleontológicas Llewellyn Ivor Price, Peirópolis, Uberaba County, Minas Gerais, Brazil; CRIDC, Centro Regional de Investigación y Desarrollo Cultural, Malargüe, Mendoza, Argentina; DGM, Departamento Nacional da Produção Mineral, Museu de Ciências da Terra, Rio de Janeiro, Brazil; MOZ, Museo Provincial de Ciencias Naturales “Profesor-Dr. Juan A. Olsacher”, Zapala, Neuquén, Argentina.

Section snippets

Systematic palaeontology

  • Archosauria Cope, 1869

  • Crocodyliformes Hay, 1930 (sensu Clark, in Benton and Clark, 1988)

  • Mesoeucrocodylia Whetstone and Whybrow, 1983

  • Peirosauridae Gasparini, 1982

  • Gasparinisuchus gen. nov.

Derivation of name. Gasparini, in honour of the accomplished vertebrate paleontologist Zulma Brandoni de Gasparini for her prolific work on South American crocodyliforms, and suchus from the Greek Souchos, with reference to the Egyptian crocodile-headed god Sobek.

Type and only known species. Gasparinisuchus

Features shared by Peirosaurus and Gasparinisuchus (MOZ 1750 PV) and their distribution among mesoeucrocodylians

In order to re-evaluate systematically the previous referral of Argentinian specimen MOZ 1750 PV to Peirosaurus torminni (Gasparini, 1982; Gasparini et al., 1991), features used to unite these specimens are assessed here. Because overlap between these two specimens is limited to the dentition and premaxilla, many features previously used to unite them (Gasparini, 1982; Gasparini et al., 1991) are now recognized to be widely distributed among basal mesoeucrocodylians.

Smooth perinarial fossa. The

Conclusions

A partial peirosaurid specimen (MOZ 1750 PV) from the Upper Cretaceous of Neuquén, Argentina originally referred to the Brazilian taxon Peirosaurus torminni (Gasparini, 1982; Gasparini et al., 1991; Praderio et al., 2009), can be morphologically distinguished on the basis of its broad and rounded rostrum, anteroposteriorly short premaxilla, reduced perinareal fossa, and short premaxillary interdental spaces. These morphological differences, together with its unique combination of characters

Acknowledgements

We thank L. Borges Ribeiro for access to Uberabasuchus, A.C. Arruda Campos and S. Tavares for access to Montealtosuchus, R. da Rocha Machado for access to Peirosaurus. Special thanks go to J.M. Leardi and F.L. Agnolin for comments on an early version of the manuscript. The development of this manuscript benefited greatly from discussions with T. Marinho, A. Turner, D. Pol, I.S. Carvalho, D. Riff, and C.R. Candeiro. AGM was supported by a CNPq (Brazil) scholarship under the direction of Dr.

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