Lophostropheus

Lophostropheus was described and named by Argentine paleontologist Martin Ezcurra (Museo Argentino de Ciencias Naturales) and French paleontologist Gilles Cuny of the Université Pierre et Marie Curie in 2007, and the type species is Lophostropheus airelensis. The composite term Lophostropheus is derived from the Greek words "lophè" (λόφη) meaning "crest" and the word "stropheus" (στροφεύς) meaning "pertaining to the vertebrae";[1] thus, "crest vertebrae". This naming is a reference to the prominent dorsal and ventral laminae observed in the cranial cervical vertebrae. The specific name, "airelensis" is a reference to the locality where the specimen was discovered, the Airel Quarry.

Estimates suggest that Lophostropheus was at best 3 m (10 ft) long and weighed 100 kilograms (220 pounds) at most.[2] In 2016 Molina-Pérez and Larramendi gave a higher estimation of 5.2 meters (17 ft) and 136 kg (300 lbs).[3] It is based on a partial skeleton first described in 1966 as a specimen of Halticosaurus.

Lophostropheus differs from other theropods in several ways. It has features reminiscent of more derived theropods, such as having a ball connection to the front of its neck vertebrae, a socket connection to the front of its tail vertebrae, and a vertical ridge on the ilium. These characteristics have all been interpreted as convergences, however.[4] It also has prominent crests on the tops and bottoms of its neck vertebrae (for which it was named),[4] and an extra pair of cavities in its neck vertebrae, unlike Liliensternus.[5] It was closer to the coelophysids, including the well-known Coelophysis, than to Liliensternus.[4] It has been assigned to the superfamily Coelophysoidea. An analysis of early dinosaurs by Baron, Norman and Barrett (2017) placed Lophostropheus in a position close to the derived theropods Sinosaurus and Cryolophosaurus.[6]

In 1966, the French paleontologists Claude Larsonneur and Albert-Félix de Lapparent described a partial theropod skeleton from the Triassic-Jurassic boundary of Normandy, found in 1959 by Claude Pareyn, as Halticosaurus sp.[7] This specimen consisted of a tooth, five neck vertebrae, two vertebrae from the back, four sacral vertebrae, tail vertebrae, portions of all the pelvic bones, and an unidentified fragment.[4] It was reinterpreted in 1993 by Gilles Cuny and Peter Galton as belonging to a new species, assigned to Liliensternus and named L. airelensis.[8] Other researchers began to notice differences between L. airelensis and the type species, L. liliensterni,[5][9] such as those observed in the pleurocoels of the cervical vertebrae,[5] and in 2007, Martin Ezcurra and Gilles Cuny assigned it to its own genus, Lophostropheus.[4]

Lophostropheus, as a coelophysoid, would have been a small to medium-sized bipedal carnivore,[10] probably comparable in size and habits to Liliensternus (best specimen estimated at 5.15 meters long, or 16.9 feet).[11] Very few dinosaurs are known from its time period; in fact, it is the only theropod genus known from good remains at the Triassic-Jurassic boundary.[4]