Cretaceous Research 60 (2016) 194e209 Contents lists available at ScienceDirect Cretaceous Research journal homepage: www.elsevier.com/locate/CretRes A new Late Cretaceous crocodyliform from the western margin of Gondwana (La Rioja Province, Argentina) Lucas E. Fiorelli a, b, *, Juan M. Leardi a, c, E. Martín Hechenleitner a, b, Diego Pol a, d, Giorgio Basilici a, b, e, Gerald Grellet-Tinner a, b, f a Consejo Nacional de Investigaciones Científicas y Tecnicas (CONICET), Argentina b Centro Regional de Investigaciones Científicas y Transferencia Tecnologica (CRILAR), Entre Ríos y Mendoza s/n, 5301, Anillaco, La Rioja, Argentina c IDEAN, Departamento de Ciencias Geologicas, Universidad de Buenos Aires, Ciudad Universitaria Pab. II, Ciudad Autonoma de Buenos Aires C1428EHA, Argentina d Museo Paleontologico Egidio Feruglio, Avenida Fontana 140, Trelew, 9100, Chubut, Argentina e Department of Geology and Natural Resources, Institute of Geosciences, State University of Campinas, 13083-870, Campinas, SP, Brazil f Orcas Island Historical Museum, 181 N Beach Rd, 98245, Eastsound, WA, USA article info abstract Article history: The Cretaceous witnessed the greatest diversity of Gondwanan notosuchian crocodyliforms, which Received 14 September 2015 displayed high levels of diversity and a notable array of specialized forms that developed in different Received in revised form ecological niches. Among this diversity, the advanced notosuchians are a clade of mid body sized forms 26 November 2015 which displays a remarkable abundance but is restricted to two lithological units from the Late Creta- Accepted in revised form 3 December 2015 ceous of South America, the Adamantina Formation in southeastern Brazil and the Bajo de la Carpa Available online xxx Formation in Patagonia (Argentina). The only exceptions known so far were the Late Cretaceous Labi- diosuchus from the Marilia Formation in Brazil and Yacarerani from the Cajones Formation in Bolivia. Keywords: Llanosuchus tamaensis Crocodyliforms Herein we report a new Cretaceous crocodyliform, gen. nov. et sp. nov., found in Notosuchia the Los Llanos Formation (Campanian?) in northwestern Argentina (La Rioja Province). The small Upper Cretaceous specimen includes well preserved fragments of the cranium and mandible with an estimated skull size of Los Llanos Formation about 9 cm lengths. This crocodyliform shares several derived characters with Notosuchus terrestris from La Rioja the Bajo de la Carpa Formation (Patagonia) and it was found in a weakly developed sandy paleosol profile Argentina formed in wet local conditions but in a region characterized by semi-arid climate and active eolian sedimentation. The presence of a new advanced notosuchian in the Cretaceous of western Gondwana, and its intermediate geographical region between the known South American species (Brazil, Argentina and Bolivia), has interesting implications, and adds another record of an advanced notosuchian in de- posits with inferred warm climates and semi-arid paleoenvironments. Finally, Llanosuchus tamaensis supports a Late Cretaceous age for Los Llanos Formation with important geological implications for La Rioja Province. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction comprises two distinct and major radiations, during the Early Cretaceous (peirosaurids uruguaysuchids and ziphosuchians) þ The Cretaceous of Gondwana witnessed the greatest diversity of and during the Late Cretaceous (South American peirosaurids, crocodyliforms, and the notosuchians are the prime example of this advanced notosuchians, and sebecosuchians). The most notable diversification (de la Fuente et al., 2007; Pol and Gasparini, 2007; feature of the clade is the extraordinary array of specialized forms Pol et al., 2014). According to Pol et al. (2014), Notosuchia that exploited specific ecological niches (Carvalho et al. 2010; Osi,€ 2013; Pol et al., 2014). Their diversification reached its peak in South America, where the majority of the advanced notosuchians are known from two units, in northern Patagonia (Argentina) and in * Corresponding author. Centro Regional de Investigaciones Científicas y Trans- ferencia Tecnologica (CRILAR), Entre Ríos y Mendoza s/n, 5301, Anillaco, La Rioja, Brazil (Candeiro and Martinelli, 2006; Pol and Gasparini, 2007; Argentina. Tel.: 54 0 3827 494251. Nobre and Carvalho, 2013; Pol et al., 2014). In this contribution þ E-mail address: lucasfi[email protected] (L.E. Fiorelli). http://dx.doi.org/10.1016/j.cretres.2015.12.003 0195-6671/© 2015 Elsevier Ltd. All rights reserved. L.E. Fiorelli et al. / Cretaceous Research 60 (2016) 194e209 195 we use the term advanced notosuchians as it was used by Pol et al. 2013; Hechenleitner et al., 2014) in different beds of this strati- (2014): a group that is deeply nested within Notosuchia and that graphic succession at Tama and other nearby localities. The asso- includes Mariliasuchus amarali, Labidiosuchus amicum, Notosuchus ciated vertebrate fossil fauna (ornithischians, titanosaurids, terrestris, Morrinhosuchus luziae and Sphagesauridae (Pol et al., abelisaurian and coelurosaurian theropods, plus the notosuchian 2014). This informal grouping has been used by other authors described here) and the microfossils, suggest a Late Cretaceous age recently and is usually recovered with high support in their ana- for the unity in Los Llanos region. lyses (e.g., Leardi et al, 2015a, 2015b). This clade also fits the In the Tama area, the Los Llanos Formation consists of a sedi- phylogenetic definition of Notosuchidae given by Sereno (2005), mentary succession more than 150 m thick with beds dipping 2e3 although the latter was made based on analyses with reduced WNW constituted of poorly sorted, medium- to fine-grained taxon sampling that did not include any member of Sphagesaur- sandstones with small pebbles, and secondarily conglomerate idae. Despite the fact that the Cretaceous terrestrial ecosystems and sandstones. It is characterized by a succession of cumulative pale- their faunas are well known in these regions (Gasparini et al., 2007; osol profiles (Basilici et al., 2014). Although beds with high calcium Novas, 2009), the diversity of advanced notosuchians outside carbonate content are present throughout the succession, they are northern Patagonia and Brazil is virtually unknown, with the sole particularly common in the lower section. Despite the absence of exception of the Late Cretaceous Yacarerani boliviensis from the sedimentary structures, conglomeratic sandstone at the base of the Cajones Formation of Bolivia (Novas et al., 2009; Leardi et al., formation shows ‘ghosts’ of cross-stratifications. The specimen 20115a). presented here was recovered from a paleosol profile ~30 m above The Cretaceous vertebrate fossil-bearing beds in La Rioja Prov- the contact with the underlying unit (see Supplementary ince, northwestern Argentina, remained poorly known and almost Information for more details and discussions of the geology and unstudied, aside from the Sanagasta neosauropod nesting site in sedimentology of Los Llanos Formation). Los Llanos Formation, being one of the most important recent findings (Grellet-Tinner and Fiorelli, 2010). Field works on the outcrops of the Los Llanos Formation (Tama locality, southeastern 3. Systematic paleontology La Rioja Province, NW Argentina), lead to the discovery of a new terrestrial vertebrate assemblage. This fossil fauna includes repre- Crocodylomorpha Walker, 1970 (sensu Clark, 1986) sentatives of three major dinosaur clades, and their association Crocodyliformes Hay, 1930 (sensu Clark, 1986) with microfossils suggests a Late Cretaceous age for the unit Mesoeucrocodylia Whetstone and Whybrow, 1983 (Fiorelli et al., 2012; Hechenleitner et al., 2014). Notosuchia Gasparini, 1971 Here, we report a new crocodyliform from the Los Llanos For- Llanosuchus tamaensis gen. et sp. nov. mation that consists of skull and lower jaw fragments with incomplete but well-preserved dentition, which represents a new Etymology. From Llanos (Los Llanos geographic region), the south species of a small-bodied notosuchian crocodyliform. In this paper east plains of La Rioja; also from Sierra de Los Llanos (Los Llanos we describe the remains of this new notosuchian and test its mountain range), where the type outcrops of the Los Llanos For- phylogenetic relationships using a recently published dataset. mation are located; and souchos (Gr.), crocodile; specific epithet Institutional abbreviationsdCRILAR Pv, Centro Regional de tamaensis after the Tama village, La Rioja province, Argentina. Investigaciones Científicas y Transferencia Tecnologica, Paleo- Holotype. CRILAR-Pv 502. The specimen includes fragments of the vertebrate collection, Anillaco, La Rioja, Argentina; MLP, Museo left and right maxilla (supporting the left palatal lamina), both with de La Plata, La Plata, Argentina; MUCPv, Museo de Geología y maxillary teeth, fragments of the left jugal, left pterygoid and Paleontología, Paleo-vertebrate collection, Universidad Nacional ectopterygoid, right dentary with teeth, and a small fragment of del Comahue, Neuquen, Argentina. right dentary with surangular (Figs. 2e7). 2. Geological setting Type locality. The holotype comes from the Colozacan valley in the vicinity of Tunacata and Guasamayo, 4 km south of Tama village The new taxon was discovered SW of Tama village in La Rioja (Gral. Angel V. Penaloza~ department), western slope of Sierra de Los Province, northwestern Argentina (Fig. 1), in exposures at the type Llanos mountain range in the southeastern region of La