New remains of a gavialoid crocodilian from the late Oligocene-early Miocene of the Pirabas Formation, Brazil HELOISA MORAES-SANTOS 1 *, JEAN BOCQUENTIN VILLANUEVA 2 and PETER MANN TOLEDO 3 1 Coordenação de Ciências da Terra e Ecologia, Museu Paraense Emilio Goeldi, Av. Perimetral, 1901 66077-830, Belém, Para, Brazil 2 LPP, Universidade Federal da Acre, Acre, Brazil 3 CCST, Instituto Nacional de Pesquisas Espaciais, São José do Rio Preto, Brazil Received 2 June 2009; revised 14 April 2010; accepted for publication 19 October 2010 New specimens of gavialoids collected from the Pirabas Formation, Brazil, provide additional information about the evolutionary evolution of Gavialoidea during the late Oligocene-early Miocene. We describe a specimen that has a more gracile symphyseal mandible than any other South American gavialoid. This fossil represents an unusually diverse radiation of gavialoids that were probably ecologically differentiated from each other by size and dietary specialization. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 163, S132–S139. doi: 10.1111/j.1096-3642.2011.00710.x ADDITIONAL KEYWORDS: marine deposits – phylogeny – rostrum. INTRODUCTION The Late Oligocene was a time of extensive marine invasions, probably because of a combination of tec- tonic subsidence and high sea level stands. Marine sediments of this age are common in North and South America and the Greater Antilles (Iturralde-Vinent & MacPhee, 1999). The Pirabas Formation, on the northern coast of Brazil (Fig. 1), was considered Oligo-Miocene in age by Ferreira (1982), based on the presence of the gastropod Orthaulax pugnax. Accord- ing to Góes et al. (1990) and Rossetti (2001), distinct facies characterize the Pirabas Formation as having been deposited in an open marine environment with warm, shallow, agitated waters, including areas of lagoons, estuaries, and mangroves. Significant sea level falls were successively followed by major sea level rises and transgressions. Remains of fossil vertebrates and invertebrates are relatively common in Neogene faunas of the Pirabas Formation in the north-eastern Amazon region, where they have been collected for more than 120 years (White, 1887; Rossetti & Góes, 2004). A small collection of isolated and fragmentary remains of fossil Crocodyliformes has accumulated in the collections of the Museu Paraense Emilio Goeldi, Belém, Brazil, over the past 20 years (Toledo et al., 1997; Rossetti, 2001; Rossetti & Góes, 2004). These specimens, collected from the late Oligocene-early Miocene Pirabas Formation, are the subject of this paper. The presence of gavialoid species in South America has often been discussed by different authors and has resulted in several con- troversies. Longirostrine crocodylians occur in the Cenozoic along the Atlantic coast of North America. These forms include the fossils generally referred to Gavialosuchus (Toula & Kail, 1885) or Theca- champsa (Cope, 1867) known from the Late Miocene of Florida and Middle Miocene of Virginia and Maryland (Mook, 1921a; Myrick, 2001). Longirostrine crocodylians from South America have been known since Burmeister (1885) reported *Corresponding author. E-mail: hmoraes@museu-goeldi.br Zoological Journal of the Linnean Society, 2011, 163, S132–S139. With 5 figures © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 163, S132–S139 S132 Downloaded from https://academic.oup.com/zoolinnean/article-abstract/163/suppl_1/S132/2627061 by guest on 31 May 2020