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(Lower Jurassic) of Alhadas, Portugal A new plesiosauroid from the Toarcian (Lower Jurassic) of Alhadas, Portugal ADAM S. SMITH, RICARDO ARAÚJO, and OCTÁVIO MATEUS Smith, A.S., Araújo, R., and Mateus, O. 2012. A new plesiosauroid from the Toarcian (Lower Jurassic) of Alhadas, Portu− gal. Acta Palaeontologica Polonica 57 (2): 257–266. A partial plesiosauroid skull from the SãoGião Formation (Toarcian, Lower Jurassic) of Alhadas, Portugal is re−evalu− ated and described as a new taxon, Lusonectes sauvagei gen. et sp. nov. It has a single autapomorphy, a broad triangular parasphenoid cultriform process that is as long as the posterior interpterygoid vacuities, and also a unique character com− bination, including a jugal that contacts the orbital margin, a distinct parasphenoid–basisphenoid suture exposed between the posterior interpterygoid vacuities, lack of an anterior interpterygoid vacuity, and striations on the ventral surface of the pterygoids. Phylogenetic analysis of Jurassic plesiosauroids places Lusonectes as outgroup to “microcleidid elasmo− saurs”, equivalent to the clade Plesiosauridae. Lusonectes sauvagei is the only diagnostic plesiosaur from Portugal, and the westernmost occurrence of any plesiosaurian in Europe. Key words: Elasmosauridae, Plesiosauridae, Plesiosauria, Lusonectes sauvagei, plesiosaur, Jurassic, Toarcian, Lusita− nian basin, Portugal. Adam S. Smith [[email protected]], Thinktank, Birmingham Science Museum, Millennium Point, Curzon Street, Birmingham, B4 7XG, UK; Ricardo Araújo [[email protected]], Roy M. Huffington Department of Earth Sciences, PO Box 750395, Dallas, Texas, 75275−0395; and Museu da Lourinhã, Rua João Luis de Moura, 2530−157 Lourinhã, Portugal; Octávio Mateus [[email protected]], CICEGe, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829−516 Caparica, Portugal; and Museu da Lourinhã, Rua João Luis de Moura, 2530−157 Lourinhã, Portugal. Received 13 March 2011, accepted 16 May 2011, available online 20 May 2011. Introduction vertebra assigned to Cryptoclidus is reported from the Ceno− manian of Alcântara (Castanhinha and Mateus 2007). The The Lusitanian depositional basin in Portugal has yielded a most significant of these fossils is a partial plesiosaurian rich array of Mesozoic terrestrial vertebrates, particularly di− skull (MG33) from the SãoGião Formation (Toarcian, nosaurs and mammals (Antunes and Mateus 2003; Mateus Lower Jurassic) of Alhadas, and this forms the basis of this 2006). In contrast, marine vertebrates are rare. Castanhinha paper. and Mateus (2007) reviewed the known marine reptile mate− Other vertebrates from the Early Jurassic of Portugal in− rial from Portugal and recorded a total of just 28 specimens, clude the bony fishes Furo cf. arthastamus (Amiiformes) including 23 ichthyosaurians, four plesiosaurians, and one and Proleptolepis sp. (Pachycormiiformes) from the Sine− mosasauroid. The ichthyosaurian remains have been referred murian of Água de Madeiros (Antunes et al. 1981), Ichthyo− to Ichthyosaurus intermedius and Stenopterygius sp. (Antunes saurus sp. from the Sinemurian of São Pedro de Moel (Sau− et al. 1981; Castanhinha and Mateus 2007), and the single vage 1897–1898), the thalattosuchian crocodilian Mystrio− mosasauroid was assigned to Mosasaurus sp. (Sauvage 1897– saurus (= Steneosaurus) bollensis from Tomar (Antunes 1898; Veiga Ferreira 1958). Many of these fossils were col− 1967), and the thyreophoran dinosaur Lusitanosaurus liasi− lected in Portugal during the nineteenth century and have been cus Lapparent and Zbyszewski, 1957, possibly also from the overlooked by modern researchers, so re−evaluation of this Sinemurian of São Pedro de Moel. material is necessary. Sauvage (1897–1898: 21–22, pl. 3: 1–3) originally de− The rare plesiosaurian fossils from Portugal range in age scribed and figured MG33 in the first report on plesiosaurian from Toarcian to Cenomanian (Castanhinha and Mateus remains from Portugal as Plesiosaurus sp., but refrained 2007). The material has been referred to Cryptoclidus sp. and from identifying it to species level. Some recent authors have Plesiosaurus sp. or has been regarded as indeterminate. For also listed it as Plesiosaurus sp. (Bardet et al. 2008; Ruiz− example, undescribed plesiosaurian teeth are known from Omeñaca et al. 2009). Castanhinha and Mateus (2007) allo− the Kimmeridgian− to Tithonian−aged Lourinhã Formation of cated the skull to Plesiosauria indet., and Smith et al. (2010) Santa Cruz (Castanhinha and Mateus 2007), and an isolated provided a short description of the skull but refrained from Acta Palaeontol. Pol. 57 (2): 257–266, 2012 http://dx.doi.org/10.4202/app.2011.0023 258 ACTA PALAEONTOLOGICA POLONICA 57 (2), 2012 identifying it. This paper provides a redescription of this rare Type locality: 1500 m WNW of Alhadas, near Murtede, Portugal Portuguese plesiosaurian specimen and assesses its system− (40°11’N, 8°47'W). atic status based on detailed comparison with other Lower Type horizon: Toarcian (Lower Jurassic) beds of the SãoGião Forma− Jurassic plesiosauroid taxa. tion, which extends from the lower Toarcian (Dactylioceras poly− morphum Ammonite Biozone) to the mid–upper Toarcian (Hammato− Institutional abbreviations.—BMNH, Natural History Mu− ceras speciosum Ammonite Biozone) (Kullberg et al. 2012). seum, London, UK; MG, Museu Geológico, Lisbon, Portu− Diagnosis.—Lusonectes possesses a single autapomorphy, a gal; MMUM, The Manchester Museum, The University of broad triangular parasphenoid cultriform process that is as Manchester, Manchester, UK; SMNS, Staatliches Museum long as the posterior interpterygoid vacuities. The taxon is für Naturkunde, Stuttgart, Germany; SMUSMP, Southern further diagnosed by the following unique combination of Methodist University, Shuler Museum of Palaeontology, characters: jugal contacts the orbital margin, a distinct para− Dallas, USA. sphenoid–basisphenoid suture exposed between the poste− rior interpterygoid vacuities, an unkeeled ventral parabasi− sphenoid with a flat anterior and gently convex posterior re− Historical note gion of the ventral surface, lack of an anterior interpterygoid vacuity, and palatal striations on the ventral surface of the There is some confusion over the provenance of MG33 be− pterygoids. The teeth have no ornamentation or striations, cause one of the labels associated with the specimen contra− but this may be due to abrasion. dicts the others. Two detailed labels are considered correct and state that MG33 originated from “600 m a N30E du pys. Description dans Alhadas” and “mélange du lias moyen avec q.q. fossiles MG33 is a small substantially complete cranium (127 mm du Toarcien”. This is corroborated by Sauvage (1897–1898: long as preserved) with the mandible in articulation (Fig. 1). 2) who identified the skull as “d’anciennes récoltes faites The anterior and posterior portions of the skull are broken à 1500 métres O.N.O. du village d’Alhadas, et prèsde off and missing. Most of the elements from the skull roof Murtede, présentent un mélange de Charmouthien et de are missing and parts of the dorsal surface represent an Toarcien” (= collected at 1500 m WNW from the village of eroded internal mould of the skull (Fig. 1C). The palatal Alhadas, near Murtede, which yield a mix of Charmouthian surface is well preserved and exhibits clear sutures and sur− [equivalent to Pliensbachian] and Toarcian fossils). A large face detail. quantity of material was collected from the extensive out− Skull roof.—The skull roof is poorly preserved, but the overall crops around Alhadas by the geologist Paul Choffat (1849– shape can be discerned. There are large oval orbital openings 1919) and his team as they mapped the area. It is possible that and the anterior margins of the temporal fenestrae are visible MG33 was collected during those expeditions. Alhadas has (Fig. 1C). The left orbital opening is complete (42 mm long yielded several other vertebrate remains including ichthyo− and 33 mm wide). The external nares are not apparent but saurs and fishes, and a new fossil fish locality was identified must have been very small. An alveolus visible on the broken during a prospecting trip in November 2007. An erroneous anterior surface of the cranium indicates that the total pre− label gives the location of MG33 as São Pedro de Moel. orbital length of the skull was not much longer than the pre− served portion, and the preorbital region was therefore particu− larly short. A short snout is also present in Zarafasaura from Systematic palaeontology the Maastrichtian of Morocco (Vincent et al. 2011). The rela− tive length of the preorbital region is of potential systematic Sauropterygia Owen, 1860 significance in plesiosaurians (O’Keefe 2001; Ketchum and Plesiosauria de Blainville, 1835 Benson 2010), but the postorbital region is incomplete in MG33, so meaningful comparative skull proportions cannot Plesiosauroidea Welles, 1943 be obtained. Plesiosauridae Gray, 1825 A broad and deep midline trough extends from the anterior Genus Lusonectes nov. margin of the skull and between the orbits. This trough occu− pies the probable position of the premaxillae and frontals and Type species: Lusonectes sauvagei sp. nov.; see below. contrasts with the condition in other plesiosaurs, which pos− Etymology: From Latin Luso, Portuguese and Greek nectes, swimmer. sess a distinct midline prominence formed by the posterior Lusonectes sauvagei sp. nov. rami of the premaxillae (e.g., Libonectes, SMUSMP 69120, Figs. 1, 2. RA personal observation, and Nichollssaura Druckenmiller Holotype: MG33, a partial
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