Lophostropheus (meaning "crest vertebrae") was a genus of coelophysoid dinosaur from the Rhaetian-Hettangian stage border (about 200 Ma) Moon-Airel Formation of Normandy, France. It is based on a partial skeleton first described in 1966 as a specimen of Halticosaurus. It is one of the few dinosaurs known from rocks near the Triassic-Jurassic boundary.
The type species, Lophostropheus airelensis, was named by Argentine palaeontologist Martin Ezcurra of the Museo Argentino de Ciencias Naturales in Buenos Aires and French paleontologist Gilles Cuny of the Universite Pierre et Marie Curie in Paris. Cuny had previously helped describe the specimen in 1993 as a species of Liliensternus (L. airelensis).
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 are all interpreted as convergences, however. It was closer to the coelophysids, including the well known Coelophysis, than to Liliensternus.
In 1966, the French paleontologists C. Larsonneur and Albert-Felix de Lapparent described a partial theropod skeleton from the Triassic-Jurassic boundary of Normandy as Halticosaurus sp. This specimen, now held at the University of Caen, 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. It was reinterpreted in 1993 by Gilles Cuny and Peter Galton as belonging to a new species, assigned to Liliensternus and named L. airelensis. Other researchers began to notice differences between L. airelensis and the type species, L. liliensterni, and in 2007, Martin Ezcurra and Cuny assigned it to its own genus, Lophostropheus.
Lophostropheus, as a coelophysoid, would have been a small- to medium-sized bipedal carnivore probably comparable in size and habits to Liliensternus (best specimen estimated at 5.15 meters long, or 16.9 feet). 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.