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A new cretaceous notosuchian (Mesoeucrocodylia) with bizarre dentition from Brazil

A new cretaceous notosuchian (Mesoeucrocodylia) with bizarre dentition from Brazil
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   A new cretaceous notosuchian (Mesoeucrocodylia)with bizarre dentition from Brazil zoj_711 109..115  ALEXANDER W. A. KELLNER*, RODRIGO G. FIGUEIREDO, SERGIO A. K. AZEVEDOand DIOGENES A. CAMPOS  Departamento Nacional de Produção Mineral, Museu de Ciências da Terra, Avenida Pasteur, 404,Urca, RJ-22290-040, Brazil  Received 4 May 2010; revised 6 May 2011; accepted for publication 19 October 2010  A new species of Notosuchia,  Labidiosuchus amicum  gen. et sp. nov. , is described based on an incomplete lower jaw (DGM 1480-R) from the Upper Cretaceous Marília Formation (Maastrichtian) recovered from a quarry nearthe Peirópolis municipality, Minas Gerais State, Southeastern Brazil. The mandibular symphysis is long, strong anterodorsally projected and ‘Y-shaped’. The bizarre dentition is formed by at least eight teeth placed in asymphyseal tooth battery, some located lateral to each other. The first pair is larger than all others andprocumbent. Some teeth are obliquely implanted (anterolabially to posterolingually) and have sub circular toelliptical outline. At least the posterior teeth are single cuspidate with acute apex.  Labidiosuchus amicum  showsa rather bizarre dentition, increasing the taxonomic diversity and potential feeding strategies of notosuchiancrocodylomorphs. © 2011 The Linnean Society of London,  Zoological Journal of the Linnean Society , 2011,  163 , S109–S115.doi: 10.1111/j.1096-3642.2011.00711.x  ADDITIONAL KEYWORDS:  Cretaceous – Gondwana –  Labidiosuchus  – Marília Formation – Notosuchia. INTRODUCTION The crocodylomorph fossil record of South America isnotably rich and diverse (e.g. Price, 1955; Gasparini,1982; Kellner, 1987; Kellner & Campos, 1999; Brochu,2003; Aguilera, Riff & Villanueva, 2006; Calvo  et al .,2007; Barbosa, Kellner & Viana, 2008; Campos  et al .,2011), especially the Notosuchia, which were welladapted to terrestrial environments (e.g. Carvalho &Bertini,1999;Pol,2003;Pol&Apesteguía,2005;Nobre& Carvalho, 2006; Andrade & Bertini, 2008a; Kellner  et al ., 2009). This clade was first defined by Gasparini(1971) and comprises small terrestrial crocodylomor-phs that except for one species (Wu & Sues, 1996) aretypically found in Cretaceous deposits of Gondwana.The phylogenetic content of Notosuchia are stilldebated, and some authors include groups like Bau-rusuchidae and Araripesuchidae in this clade (Ortega  et al .,2000;Sereno  et al .,2001;Pol,2003;Sereno  et al .,2003; Turner, 2006; Pol & Gasparini, 2009). Further-more, the taxonomic status of some taxa, such as  Sphagesaurus , is presently being reviewed (Kellner  et al ., 2011). Amongst the striking features of notosuchians isthe diversified dentition of several species, which sup-ports a variety of feeding habits including omnivorousand possibly herbivorous animals (e.g. Clark, Jacobs& Downs, 1989; Andrade & Bertini, 2008c; Lecuona &Pol, 2008).In 1987, the Departamento Nacional da ProduçãoMineral, associated with the Municipality of Uberaba,reopened the palaeontological excavation for verte-brate remains in the Peirópolis neighbourhood, MinasGerais State, Brazil, where several important fossilquarries were opened by Llewellyn Ivor Price between1948 and 1969 (Campos & Kellner, 1999). Those quar-ries have yielded particularly dinosaur remains(Kellner & Campos, 2000) but other fossil vertebrateshave also been found (e.g. Price, 1955; Bertini  et al .,1993; Kellner & Campos, 1999; Carvalho, Ribeiro & Avilla, 2004). During an excavation at the quarryclose to the ‘Serra do Veadinho’, one of us (S. A. K. A.)collected a fragmentary bone embedded in sandstone *Corresponding author. E-mail:  Zoological Journal of the Linnean Society , 2011,  163 , S109–S115. With 5 figures © 2011 The Linnean Society of London,  Zoological Journal of the Linnean Society , 2011,  163 , S109–S115  S109  that was preliminary identified as a dinosaur element(Campos & Azevedo, 1992). Further preparationrevealed that this specimen is a lower jaw of a newnotosuchian crocodylomorph that shows a quite dis-tinct dentition and is described here.  A  NATOMICAL ABBREVIATIONS ang, angular; den, dentary; for, foramen; emf, man-dibular fenestra; spl, splenial; syp, symphyseal plat-form; sur, surangular; d1 - d8, dentary tooth 1–8. SYSTEMATIC PALAEONTOLOGY  Crocodylomorpha Walker, 1970Crocodyliformes Hay, 1930Mesoeucrocodylia Whetstone & Whybrow, 1983Notosuchia Gasparini, 1971 G ENUS  L  ABIDIOSUCHUS  GEN .  NOV  . Type species: Labidiosuchus amicum  gen. et sp. nov.  Etymology:  The generic name is derived from theGreek word  labis  for forceps, tongs and  souchos  thatmeans crocodile.  Diagnosis:  As for the type and only species.  L  ABIDIOSUCHUS AMICUM   SP .  NOV  .  Holotype:  Incomplete lower jaw housed at the EarthScience Museum of the Departamento Nacional daProdução Mineral under the number DGM 1480-R(Figs 1–5). Cast at the Museum Nacional/UFRJ (MN).  Etymology:  The specific name comes from the Latin amicus  for friend, honouring the community that hashelped to protect the palaeontological site at Peirópo-lis, especially the members of the Associação dos Amigos do Sítio Paleontológico de Peirópolis (Associa-tion of the Friends of the Peirópolis PalaeontologicalSite). Type locality:  ‘Serra do Veadinho’, Municipality of Peirópolis, Minas Gerais State, south-eastern Brazil. Type horizon:  Upper Cretaceous (Maastrichtian)Marília Formation of the Bauru Group (Dias-Brito  et al ., 2001).  Diagnosis:  Notosuchian that can be separated fromall other members of this clade based on the following combination of characters (autapomorphies are indi-cated with an asterisk): the mandible is stronglyanterodorsally projected; there is a symphyseal plat-form holding the teeth*; the surangular is anteriorlybifurcated; strong heterodont dentition both in sizeand shape, formed by teeth with circular and ellipti-cal cross section; discrepancy of size of the first ante-rior pair of teeth that are much larger than all othermandibular teeth*; first anterior teeth strongly Figure 1.  Right lateral view of   Labidiosuchus amicum gen.  et  sp. nov.  lower jaw (DGM 1480-R). A, drawing; B,photograph. Abbreviations: ang, angular; den, dentary;emf, external mandibular fenestra; sur, surangular; syp,symphyseal platform. Scale bars  =  10 mm. Figure 2.  Dorsal view of   Labidiosuchus amicum  gen. et  sp. nov.  mandible (DGM 1480-R). The white arrowsindicate the anterior bifurcation of the surangular. Abbre- viations: den, dentary; spl, splenial; sur, surangular. Scalebar  =  10 mm. S110  A. KELLNER  ET AL .  © 2011 The Linnean Society of London,  Zoological Journal of the Linnean Society , 2011,  163 , S109–S115  inclined anterodorsally; presence of small teeth on themedial side of the anterior portion of the dentary*;proportionally large number of the teeth, tightlypacked, at the anterior symphysis*; presence of asymphyseal tooth battery.  Description and comparisons The holotype of   Labidiosuchus amicum  consists of an incomplete lower jaw (DGM 1480-R) with theanterior part of the dentary complete, lacking mostof the right mandibular ramus and the posteriorend of the left mandibular ramus (Figs 1–4). Thepreserved part is about 70.5 mm long and clearlysuggests that the jaw had a Y-shaped outline indorsal view (Fig. 2). Although the surface of some parts of this specimenis broken, there are no perceptible taphonomic defor-mations. The preservation of DGM 1480-R is thesame as observed in other dinosaur bones collected inthis area, also including other crocodylomorphs (e.g.Campos & Kellner, 1999; Kellner & Campos, 2000;Carvalho  et al ., 2004).The dentaries are strongly bent dorsally with aconcave dorsal and convex ventral margin, respec-tively. The anterior portion is projected anterodorsallyat about 35°, similar to  Adamantinasuchus navae (Nobre & Carvalho, 2006). Opposite dentaries are notfused to form an actual symphysis but one probablydeveloped in ontogenetically older individuals. Thecontact region of opposite dentaries is longer thanwide as in other notosuchians, differing from theputative notosuchians  Anatosuchus  and  Simosuchus (Buckley  et al ., 2000; Sereno  et al ., 2003). The distal-most end of the dentaries forms a symphyseal plat-form, which consists of a horizontal shelf with atightly packed set of teeth.The lateral surface of the dentary ramus is flat andslightly compressed in the anterior to mid-sections,which can also be observed in  Comahuesuchus , Chimaerasuchus ,  Malawisuchus ,  Mariliasuchus ,  Notosuchus ,  Simosuchus , the skull attributed to  Sph-agesaurus huenei  (see Kellner  et al ., 2011 for detailsabout the taxonomic status of   Sphagesaurus ), and Uruguaysuchus  (Gasparini, 1971; Bonaparte, 1991;Wu & Sues, 1996; Gomani, 1997; Carvalho & Bertini,1999; Buckley  et al ., 2000; Martinelli, 2003; Pol, 2003;Fiorelli & Calvo, 2008). The alveolar margins of thedentaries are flat and smooth and they do not project. All anterior-most alveoli are separated by thin septa;however, the distal-most alveoli are well separated bythick walls.The mandibular fenestra is large and elliptical withthe dorsal margin formed by the dorsal branch of thedentary and the anterior border of the surangular.The latter is bifurcated and has a lateral ramuscontacting the dentary and a medial ramus directedto the splenial (Fig. 2), similar to  Mariliasuchus  and‘  Sphagesaurus ’  montealtensis  (Carvalho & Bertini,1999; Andrade & Bertini, 2008a). The anteromedialmargin of the surangular is dorsally arched as in Comahuesuchus ,  Mariliasuchus ,  Notosuchus ,  Simosu-chus , and ‘  Sphagesaurus ’  montealtensis  (Bonaparte,1991; Carvalho & Bertini, 1999; Buckley  et al ., 2000; Andrade & Bertini, 2008a; Fiorelli & Calvo, 2008;Kellner  et al ., 2011), differing from the straight tonear-straight margins observed in  Anatosuchus ,  Araripesuchus gomesii ,  Malawisuchus , and  Uruguay-suchus  (Price, 1959; Gasparini, 1971; Gomani, 1997;Sereno  et al ., 2003).The most striking feature of   L. amicum  is thedentition, with the teeth tightly packed in thesymphyseal platform made by the dentaries. Alto-gether there are eight teeth present in this region,which is at a higher level relative to the remaining part of the lower jaw. As already noted, there is notaphonomic modification that could account eitherfor the shape of the mandibular symphysis or forthe particular position of the teeth. No tooth is com-plete, but almost every alveolus shows a partialtooth inside (Fig. 4). The first tooth (d1) is projectedanterodorsally at about 35°, similar to the conditionobserved in  Adamantinasuchus ,  Armadillosuchus ,and  Mariliasuchus  (Carvalho & Bertini, 1999; Nobre& Carvalho, 2006; Marinho & Carvalho, 2009).However, in  L. amicum  this tooth is much largerthan all others. Three teeth (d2 - d4) follow, sepa-rated from each other by thin septa. The most ante-rior one (d2), the smallest of the jaw, is placed closeto the midline. This tooth is unlikely to be areplacement tooth because it is far too small com-pared to the first tooth and located in the wrong position to be replacing the fourth tooth (d4), which Figure 3.  Anterior view of the mandibular symphysis of   Labidiosuchus amicum  gen.  et  sp. nov.  (DGM 1480-R). Abbreviation: for, foramen. Scale bar  =  10 mm. NEW NOTOSUCHIAN WITH BIZARRE DENTITION  S111  © 2011 The Linnean Society of London,  Zoological Journal of the Linnean Society , 2011,  163 , S109–S115  is located posteriorly at the medial half of the jaw. The next tooth (d3) reaches the lateralmargin of the dentary and has a rather elliptictransverse section (Fig. 4). Two other teeth (d5 andd6) follow, with elliptic and rounded transversesections, respectively. These teeth are stronglyobliquely implanted relative to the lateral margin of the dentary, with giroversion of about 50 and 40°,respectively. The oblique implantation of teeth istypical of the Sphagesauridae, although  Mariliasu-chus  and  Notosuchus  also have some teeth with themain axis at an angle relative to the lateral marginof the jaw (Andrade & Bertini, 2008b, c). In  Corin- gasuchus anisodontis  the obliquely implanted teethdiffer by their anterolingual to posterolabial direc-tion (Kellner  et al ., 2009).Posterior to those, a much larger tooth (d7) witha subcircular transverse section can be found, Figure 5.  Last tooth (d8) of   Labidiosuchus amicum  gen.  et  sp. nov.  (DGM 1480-R), positioned on the mandibularramus. A, photograph and B, drawing of labial view; C, photograph and D, drawing of lingual view. Scale bars  =  1 mm. Figure 4.  Detail of the symphysis of   Labidiosuchus amicum  gen.  et  sp. nov.  (DGM 1480-R) in occlusal view. A,drawing; B, photograph showing the dentition. Abbreviations: d1 - d8, dentary teeth 1 to 8. Scale bars  =  5 mm. S112  A. KELLNER  ET AL .  © 2011 The Linnean Society of London,  Zoological Journal of the Linnean Society , 2011,  163 , S109–S115  situated in a slightly dorsally projected part of themandible. It is followed by a similar but slightlysmaller tooth (d8), both being somewhat obliquelyimplanted.The last tooth (d8) is positioned at the diverging point of the mandibular rami and can only beobserved on the right side (Fig. 5). It is not fullybroken and shows a well striated surface. Smallridges are located in a small posterolingual carina,differing from the robust ridges observed in sphag-esaurids (Price, 1950; Pol, 2003). The tooth apex isacute like in  Chimaerasuchus ,  Malawisuchus , and Uruguaysuchus  (Gasparini, 1971; Wu & Sues, 1996;Gomani, 1997) with a single cusp. There is no con-striction at the transitional region from the crown tothe root as reported in some notosuchians, such as Candidodon ,  Malawisuchus ,  Mariliasuchus , and‘  Sphagesaurus huenei ’ (Gomani, 1997; Andrade &Bertini, 2008b, c). DISCUSSION AND CONCLUSIONS The phylogenetic position of   L. amicum  is not easyto establish because of the incompleteness of theholotype. The overall shape of the lower jaw allowsthe allocation of this new species to the Notosuchia, arather diverse group of crocodylomorphs that shows agreat variety of dentition.  Labidiosuchus amicum  isthe only one where the teeth are so closely placed ina horizontal platform with medial and lateral teethpositioned close to each other. Anterior projection of the lower jaw is also recorded in  Adamantinasuchus .Some teeth show an oblique implantation that istypical of the Sphagesauridae. The Y-shaped conditionof the lower jaw is shared with  Adamantinasuchus ,  Notosuchus ,  Mariliasuchus , and ‘  Sphagesaurus mon-tealtensis ’ and probably with  Candidodon . The strong protruding forward inclination of the first pair of teeth (commonly referred to as incisiforms) present in  L. amicum  is also present in  Adamantinasuchus ,  Armadillosuchus , and  Mariliasuchus  (Carvalho &Bertini, 1999; Nobre & Carvalho, 2006; Marinho &Carvalho, 2009). However, in  Notosuchus  and  Spha- gesaurus  they are slightly anteriorly projected(Gasparini, 1971; Andrade & Bertini, 2008a). Fur-thermore,  L. amicum  lacks the typical sphagesauriddentition (Price, 1950; Pol, 2003). Therefore, although  L. amicum  can be regarded as a notosuchian, theclose relationship of this taxon within the claderemains to be established.The occurrence of yet another notosuchian with aquite distinctive dentition corroborates previous sug-gestions that this group of crocodylomorphs havedeveloped a quite diverse range of feeding habits. Although it is not easy to establish what  L. amicum might have been feeding on, the tightly packed teethlocated on a platform made of the dentaries indicatethat this species could have used the jaws for crush-ing food, suggesting that it was feeding on ratherresistant material. Although seeds and similar itemscould have been a possibility, making this anotherpotential omnivorous or even herbivorous species (e.g.Clark  et al ., 1989; Buckley  et al ., 2000; Andrade &Bertini, 2008a, b, c; Lecuona & Pol, 2008), at presentthe feeding preferences of   L. amicum  cannot be deter-mined with certainty. Nevertheless, the new speciesshows yet another bizarre variation of the notosu-chian dentition adding to the diversity of this clade.  ACKNOWLEDGEMENTS We thank Alejandro Kramarz and Fernando Novasfrom the Museo Argentino de Ciências Naturales andMarcelo Reguero and Zulma Gasparini from theMuseo de La Plata for access to specimens undertheir care. We are also grateful to Gustavo Oliveirafor help with the photographs and André Pinheiro(Museu Nacional/UFRJ) is thanked for the drawingsthat illustrate this paper. We also acknowledge MarcoBrandalise de Andrade (University of Bristol) and ananonymous reviewer for comments on the originalmanuscript. This project was partially funded by theCoordenação de Aperfeiçoamento de Pessoal de NívelSuperior (CAPES) (fellowship to R. G. F.) and by theFundação Carlos Chagas de Amparo à Pesquisa doRio de Janeiro (FAPERJ, grant number E-26/152.885/ 2006 to A. W. A. K.) and Conselho Nacional de Desen- volvimento Científico e Tecnológico (CNPq, grants486313/2006-9 and 501267/2008-5 to A. W. A. K.). REFERENCES  Aguilera O, Riff D, Villanueva JB. 2006.  A new giant  Purussaurus  (Crocodyliformes, Alligatoridae) from theUpper Miocene Urumaco Formation, Venezuela.  Journal of  Systematic Palaeontology  4:  221–232.  Andrade MB, Bertini RJ. 2008a.  A new  Sphagesaurus (Mesoeucrocodylia: Notosuchia) from the Upper Cretaceousof Monte Alto City (Bauru Group, Brazil), and a revision of the Sphagesauridae.  Historical Biology  20:  101–136.  Andrade MB, Bertini RJ. 2008b.  Morphological and ana-tomical observations about  Mariliasuchus amarali  and  Notosuchus terrestris  (Mesoeucrocodylia) and their relation-ships with other South American notosuchians.  Arquivos do Museu Nacional  66:  5–62.  Andrade MB, Bertini RJ. 2008c.  Morphology of the dentalcarinae in  Mariliasuchus amarali  (Crocodylomorpha, Noto-suchia) and the pattern of tooth serration among basalMesoeucrocodylia.  Arquivos do Museu Nacional  66:  63–82. Barbosa JA, Kellner AWA, Viana MSS. 2008.  New dyro-saurid crocodylomorph and evidences for faunal turnover at NEW NOTOSUCHIAN WITH BIZARRE DENTITION  S113  © 2011 The Linnean Society of London,  Zoological Journal of the Linnean Society , 2011,  163 , S109–S115
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