Describer

Ortega, Escaso & Sanz 2010

Time

Cretaceous Early Barremian

Classification

Saurischia Theropoda Tetanurae Carnosauria Carcharodontosauridae

Diet

Carnivore

Fossilsite

Calizas de Huérgina Formation, Konservat-Lagerstätte of Las Hoyas in Cuenca, Spain.

Info

Abstract

Carcharodontosaurs were the largest predatory dinosaurs, and their early evolutionary history seems to be more intricate than was previously thought. Until recently, carcharodontosaurs were restricted to a group of large theropods inhabiting the Late Cretaceous Gondwanan land masses but in the last few years Laurasian evidence has been causing a reevaluation of their initial diversification. Here we describe an almost complete and exquisitely preserved skeleton of a medium-sized (roughly six metres long) theropod from the Lower Cretaceous series (Barremian stage) Konservat-Lagerstätte of Las Hoyas in Cuenca, Spain.

Cladistic analysis supports the idea that the new taxon Concavenator corcovatus is a primitive member of Carcharodontosauria, exhibiting two unusual features: elongation of the neurapophyses of two presacral vertebrae forming a pointed, hump-like structure and a series of small bumps on the ulna. We think that these bumps are homologous to quill knobs present on some modern birds; the knobs are related to the insertion area of follicular ligaments that anchor the roots of the flight feathers (remiges) to the arm. We propose that Concavenator has integumentary follicular structures inserted on the ulna, as in modern birds. Because scales do not have follicles, we consider the structures anchored to the Concavenator arms to be non-scale skin appendages homologous to the feathers of modern birds. If this is true, then the phylogenetic bracket for the presence of non-scale skin structures homologous to feathers in theropod dinosaurs would be extended to the Neotetanurae, enlarging the scope for explaining the origin of feathers in theropods.

Holotype

Specimen MCCM-LH 6666 at Museo de las Ciencias de Castilla-La Mancha, Cuenca, Spain, a nearly complete and articulated skeleton.

Etymology

Concavenator fromConca (Latin), for the Spanish province of Cuenca , and venator (Latin), a hunter; corcovatus (Latin), refers to the hump-like structure formed by the elongation of two presacral vertebrae.

Horizon and locality

Las Hoyas site. Calizas de La Huérguina Formation, Upper Barremian (Lower Cretaceous); La Cierva township, Cuenca, Spain.

Diagnosis

A carcharodontosaurian having four recesses, three of them connected, on the nasal bones; a large, rounded, thickened postorbital brow occupying one-third of the orbit; tall neurapophyses of the eleventh and twelfth dorsal vertebrae (five times the height of the centra); relatively high, cranially directed neurapophyses of the second and third caudal vertebrae; and a small, thorn-like caudal process at the base of each neurapophysis of the proximal caudal vertebrae. In addition, Concavenator presents a unique combination of characters: the heavily rugose (wrinkled) dorsal surface of the nasal bone, shared with more derived carcharodontosaurids and abelisaurids; the anterior end of the jugal bone posterior to the internal antorbital fenestra; the thick dorsoventral anterior process of the lacrimal bone; light rugosity on the lacrimal horn; no fenestra on the lacrimal bone; the anteriormost point of the lateral lamina of the ventral process in the lacrimal situated dorsal to themid-height of the ventral process, with a distinct rugose patch on the lateral surface; no suborbital process on the lacrimal bone; weak enamel wrinkles on teeth adjacent to the carinae that do not extend across the labial and lingual tooth surfaces, (shared with Tyrannotitan and carcharodontosaurines); no crown recurvature, (shared with carcharodontosaurines); accessory centrodiapophyseal lamina on the transverse processes of the posterior dorsal vertebrae, (shared with baryonychines); the prominent rugose distal tubercle on the ischium (part of the hip bone); quill knobs in the posterolateral margin of the ulna, (shared with derived maniraptorans); and the preacetabular blade of the ilium having a convex ventral portion of the cranial edge and hook-like ventral process, (shared with tyrannosaurs ).

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