A new specimen of the theropod dinosaur Baryonyx from the early Cretaceous of Portugal and taxonomic validity of Suchosaurus

Sunday, June 19, 2011

Although the Late Jurassic of Portugal has provided abundant dinosaur fossils, material from the Early Cretaceous is scarce. This paper reports new cranial and postcranial material of the theropod dinosaur Baryonyx walkeri found in the
Barremian (Papo Seco Formation) of Portugal. This specimen, found at Praia das Aguncheiras, Cabo Espichel, consists of a partial dentary, isolated teeth, pedal ungual, two calcanea, presacral and caudal vertebrae, fragmentary pubis, scapula,
and rib fragments. It represents the most complete spinosaurid yet discovered in the Iberian Peninsula and the most complete dinosaur from the Early Cretaceous of Portugal. This specimen is confidently identified as a member of Baryonychinae
due to the presence of conical teeth with flutes and denticles in a dentary rosette. The specimen ML1190 shares the following characteristics with Baryonyx walkeri: enamel surface with small (nearly vertical) wrinkles, variable denticle
size along the carinae, 6–7 denticles per mm, wrinkles forming a 45 degree angle near the carinae, and tooth root longer than crown. In addition, dubious taxa based on teeth morphology such as Suchosaurus cultridens (Owen, 1840–1845), and
Suchosaurus girardi (Sauvage 1897–98; Antunes & Mateus 2003) are discussed, based on comparisons with well-known material such as Baryonyx walkeri Charig & Milner, 1986. Suchosaurus cultridens and S. girardi are considered as nomina dubia due to the lack of diagnostic apomorphies, but both specimens are referred to Baryonychinae incertae sedis.

Spinosauridae is a group of theropod dinosaurs with snout and tooth morphology convergent with that of crocodiles (Sereno et al. 1998; Rayfield et al. 2007). The group is placed as part of spinosauroid (Sereno et al. 1998, Rauhut 2003), or megalosauroid (Benson 2010), tetanurans, and divided into Baryonychinae (with Baryonyx walkeri Charig & Milner, 1986 and Suchomimus tenerensis Sereno et al., 1998, and possibly also Cristatusaurus lapparenti Taquet & Russell, 1998 pending verification of its synonymy with S. tenerensis) and Spinosaurinae (with Spinosaurus aegyptiacus Stromer, 1915 and Irritator challengeri Martill et al., 1996) (Charig & Milner 1986, 1997; Sereno et al. 1998; Sues et al. 2002). The Thai form Siamosaurus suteethorni Buffetaut & Ingavat, 1986 also seems to belong to Spinosauridae (Buffetaut et al. 2008). Although dinosaur bones and tracks from the Late Jurassic of Portugal are well known (Mateus & Antunes 2000, 2003; Ricqlès et al. 2001; Antunes & Mateus 2003; Mateus 2006; Mateus & Milàn 2008), Lower Cretaceous
fossils are rare, and are restricted to isolated teeth and bone remains (Sauvage 1897–98; Antunes & Mateus 2003) and tracks (Mateus & Antunes 2003, and references therein). The only genera reported are Iguanodon and a possible basal macronarian sauropod attributed to the dubious taxa ‘Astrodon’ or ‘Pleurocoelous’ (Sauvage 1897–98), and ‘Megalosaurus’.

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