Proceratosaurus, Huene, 1923

Rauhut, Oliver W. M., Milner, Angela C. & Moore-Fay, Scott, 2010, Cranial osteology and phylogenetic position of the theropod dinosaur Proceratosaurus bradleyi (Woodward, 1910) from the Middle Jurassic of England, Zoological Journal of the Linnean Society 158 (1), pp. 155-195 : 156

PROCERATOSAURUS

Woodward’s (1910: 114) main argument for the generic placement in Megalosaurus was the number of premaxillary teeth (four), which differs from that of Ceratosaurus (three) and Allosaurus (five), the only other theropods for which good cranial material was then known.

The name Proceratosaurus first appeared in a phylogenetic scheme illustrated by Huene (1923: fig. 3), which was not accompanied by any mention of the taxon in the text, so that Proceratosaurus Huene, 1923 , has to be regarded as a nomen nudum. However, three years later, Huene (1926a, b) validated this name with a short differential diagnosis, and a new reconstruction of the skull, in two publications, which are almost identical in respect to the statements referring to P. bradleyi . Indeed, the name is referred to as ‘ Proceratosaurus , gen. nov. ’ in both papers, raising the question as to which of these publications merits the status of original description of the genus. However, Huene (1926a) pre-dates Huene (1926b), so that the former reference has date priority, and should be regarded as the formal designation of the genus.

Concerning the systematic position of Proceratosaurus, Huene (1926a: 474, 1926b: 69 ) stated that ‘its near relationship with Ceratosaurus nasicornis has been pointed out by A. S. Woodward’, even though Woodward (1910: 114) specifically emphasized the different premaxillary tooth count in Ceratosaurus and P. bradleyi as an argument against a referral of the species to that genus. However, as is clear from the choice of the new generic name, as well as from the phylogenetic schemes presented by Huene (1923, 1926b, 1932), he regarded Proceratosaurus as an early representative of the lineage leading to Ceratosaurus . It is also worth noting that Huene (1932) considered both of these taxa to be coelurosaurians.

Paul (1988a, b) reconsidered Proceratosaurus and argued that it was closely related to Ornitholestes from the Upper Jurassic (Kimmeridgian–Tithonian) Morrison Formation of North America. Apart from the overall similarity, the main argument for this relationship was the alleged presence of a nasal horn core in the North American genus – a feature that was argued to be an artefact of preservation by Rauhut (2003a; see also Carpenter et al. 2005a). Interestingly, Paul (1988b) did not consider ‘ornitholestians’ to be coelurosaurs, but thought them to be closely related to allosaurids, in a separate subfamily Ornitholestinae . Furthermore, he referred the much larger Middle Jurassic French theropod Piveteausaurus divesensis ( Walker, 1964) to the genus Proceratosaurus , although the only overlapping elements between the type and only known specimens of both taxa (the ventral parts of the braincase) were hidden in matrix at the time. Finally, in their redescription of Ceratosaurus, Madsen & Welles (2000) included Proceratosaurus in the Ceratosauridae , thus following the ideas of Huene, but without discussing their reasons for so doing.

The first formal phylogenetic analyses to include Proceratosaurus found it to be the most basal coelurosaur of all the taxa included in the analyses ( Holtz, 2000; Rauhut, 2003a). The most important argument for this placement, which was only weakly supported in both analyses, was the enlarged antorbital fossa. However, two other recent phylogenetic analyses ( Holtz, 2001; Holtz et al., 2004) supported a close relationship between Proceratosaurus and Ornitholestes , as argued by Paul (1988a, b), although within Coelurosauria. However, support for this placement is also rather weak, and several of the characters uniting these taxa are questionable, especially the alleged presence of a median cranial crest, which is highly doubtful in Ornitholestes (see above).

INSTITUTIONAL ABBREVIATIONS

AMNH, American Museum of Natural History , New York, USA ; BSPG, Bayerische Staatssammlung für Paläontologie und Geologie, Munich , Germany ; GPIT, Geologisch – Paläontologisches Institut der Universität Tübingen, Tübingen, Germany ; IVPP, Institute for Vertebrate Paleontology and Paleoanthropology, Beijing, China ; NHM, Natural History Museum, London , UK ; OUM, Oxford University Museum of Natural History , Oxford, UK ; PVSJ, Paleontología de Vertebrados , Universidad Nacional de San Juan, San Juan, Argentina ; SAM, Iziko South African Museum , Cape Town, South Africa ; SMNS, Staatliches Museum für Naturkunde, Stuttgart , Germany .