Calamosaurus (meaning "reed lizard") was a genus of small theropod dinosaur from the Barremian-age Lower Cretaceous Wessex Formation of the Isle of Wight, England. It is based on two cervical vertebrae (BMNH R901), collected by Reverend William Fox.

History and taxonomy

Richard Lydekker came across these bones when cataloguing the Fox collection and named them Calamospondylus foxi, noting their similarity to those of Coelurus. Unfortunately, Calamospondylus had already been coined in 1866 (ironically by Reverend Fox himself, the very man honored in Lydekker's species name). Lydekker renamed it in 1891 to its present title. He also at this time provisionally referred to it the right tibia NHMUK R.186, which was discovered by William D. Fox in 1865 or 1866 and was identified by Naish et al. (2001) as belonging to a basal coelurosaurian like a compsognathid, and has recently been referred to Ornithomimosauria by Allain et al. (2014). NHMUK R.186 has since been moved to Calamospondylus. Because of its sparse remains, it has received little attention. Often, it has been synonymized with Calamospondylus as part of a long, confusing taxonomic tangle, although there is no comparable material between the two genera. Modern reviews have regarded it as a dubious theropod, although potentially a valid coelurosaurian. In 2002 Paul Turner found a dorsal vertebra near Grange Chine on the Isle of Wight. An associated partial tibia and metatarsal fragment were subsequently discovered by Oliver Mattsson and referred to Calamosaurus. Another specimen referred to Calamosaurus was collected by local fossil hunter Kai Bailey in 2014. Both specimens are on display at the Dinosaur Expeditions, Conservation and Palaeoart Centre near Brighstone, Isle of Wight. A neck vertebra of a Calamosaurus was found near Chilton Chine on the Isle of Wight by local fossil hunter Dave Badman. The newly discovered vertebra has gone on display at the Dinosaur Isle Museum in Sandown, Isle of Wight.

Specimen NHMUK R.186

NHMUK R.186 was discovered by William D. Fox in 1865 or 1866 and was first assigned to Hypsilophodon foxii by Lydekker (1888). Lydekker (1891) moved NHMUK R.186 to Aristosuchus pusillis, and Galton (1973) agreed with this classification. Welles & Long (1974) referred it to the Ornithomimidae, while Norman (1990), Kirkland et al. (1998) and Long and Molnar (1998) referred NHMUK R.186 to Coelurosauria. Galton and Molnar (2005) noted the similarities of NHMUK R.186 to the holotype of Coelurus fragilis, and Allain et al. (2014) agreed with the placement of NHMUK R.186 within Coelurosauria. Naish et al. (2001) tentatively referred the tibia to Calamosaurus foxi, and NHMUK R.186 has since been moved to Calamospondylus oweni.

Paleobiology

As a possible basal coelurosaur, Calamosaurus would have been a small, agile, bipedal carnivore. Naish et al. (2001) estimate the living animal would have been around 3 – long, with a small head given the build of the neck vertebrae.