Thursday 8 November 2018

Lavocatisaurus agrioensis: A new species of Rebbachisaurid Sauropod Dinosaur from the Early Cretaceous of Argentina.

The Rebbachisaurids are a group of Diplodocimorph Sauropod Dinosaurs known from the Cretaceous of South America, Africa and Europe. They are considered to be the sister group to the other two Diplodocimorph clades, the Diplodocids and the Dicraeosaurid, which along with their presence on both sides of the Atlantic (implying they must have appeared before this ocean opened) suggests that they first appeared in the Middle Jurassic, though the earliest fossils confidently assigned to the group date from the middle of the Early Cretaceous, with the group persisting till the middle of the Late Cretaceous, making them the last surviving Diplodocimorph group.

In a paper published in the journal Acta Palaeontologica Polonica on 29 October 2018, José Canudo of the Facultad de Ciencias at the Universidad de Zaragoza, José Carballido of the Museo ‘Egidio Feruglio’, Alberto Garrido of the Museo Provincial de Ciencias Naturales ‘Prof. Dr. Juan Olsacher’ and the Departamento Geología y Petróleo at the Universidad Nacional del Comahue, and Leonardo Salgado of the Instituto de Investigación en Paleobiología y Geología at the Universidad Nacional de Río Negro, describe a new species of Rebbachisaurid from the Early Cretaceous Rayoso Formation at Agrio del Medio in Neuquén Province in Patagonia.

The new species is named Lavocatisaurus agrioensis, where ‘Lavocatisaurus’ honours the French palaeontologist René Lavocat (1909-2007), who described Rebbachisaurus, the first known Rebbachisaurid and the genus from which the group takes its name, and ‘agrioensis’ means ‘from Agrio’. The species is described from a fragmentary yet still partly articulated skeleton comprising both dentaries, the left surangular, premaxillae and maxillae, the left jugal, the right squamosal, the quadrates, 23 isolated teeth and two series of 8 and 9 maxillary teeth, thehyoid bone, 11 cervical vertebrae (including the atlas and axis), 28 caudal vertebrae, cervical ribs, 2 dorsal ribs, a humerus, and a fragment of what is probably the radius, plus 24 other bone fragments thought to have come from juvenile specimens of the same species.

Rebbachisaurid Sauropod Lavocatisaurus agrioensis from Agrio del Medio (Argentina), Aptian–lower Albian. (A) Axis in lateral view (A₁) photograph, (A₂) drawing; eight cervical vertebrae in lateral view view (A₃) photograph, (A₄) drawing; anterior caudal vertebra in lateral view (A₅); middle caudal vertebra in lateral view (A₆); posterior caudal vertebra in lateral view (A₇); posteriormost caudal vertebra in lateral view (A₈); left tibia in lateral view (A₉). (B) Left scapula from a juvenile specimen, in lateral view. (C) Skeletal reconstruction based on the holotype and paratype specimens. Scale bars are 10 cm. Canudo et al. (2018). 

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