FOWLER, D. W. (2007), Recently rediscovered baryonychine teeth (Dinosauria: Theropoda): new morphologic data, range extension, & similarity to Ceratosaurus, Journal of Vertebrate Palaeontology 27(3, supp), 76A [15mb pdf of poster]

ABSTRACT

Newly identified baryonychine teeth from the UK Wealden illustrate the morphologic variability and stratigraphic range of this taxon. Whilst common in the formations in which they occur, their distinctive fluted and finely serrated teeth are often misidentified as crocodilian, which are superficially similar in appearance. Fourteen teeth from mainland Weald collections of the British Museum of Natural History (some collected over 150 years ago, all stored with goniopholid specimens) demonstrate the presence of baryonychines in the Hauterivian and possibly Valanginian stages of the Early Cretaceous: the oldest record of this group. An unusual laterally compressed, posteriorly recurved, and fluted tooth from the Purbeck Limestone (Late Jurassic – earliest Cretaceous) may extend the range of baryonychines even further.

Some specimens from the Barremian Wessex Fm (Isle of Wight ,UK) and older mainland deposits show both lingual and labial fluting, previously seen only in teeth from Spain . Spanish specimens can no longer be considered phylogenetically distinct based on this character. The fluted premaxillary and anterior dentary teeth of Ceratosaurus (and to a lesser extent, some other ceratosaurs e.g. Masiakasaurus) bear remarkable similarity to the fluted teeth of baryonychines. Whether this represents convergence or a real phylogenetic signal requires further analysis. However, isolated teeth identified as Ceratosaurus sp . from the Late Jurassic of Tendaguru, Tanzania, can no longer be assigned with confidence to this taxon and should be reassessed, especially as ceratosaur lateral teeth are unknown from these strata.

The observed phylogenetic trend towards reduced denticle size in baryonychines through to spinosaurines suggests that the hypothetical ancestral condition possessed larger denticles, similar to typical theropods and what is seen in the Tendaguru teeth. A ceratosaur origin for baryonychines has been previously suggested and subsequently rejected by recent workers. However, this relationship should be critically reassessed considering the similarity between these taxa, and recent phylogenetic analyses placing Ceratosaurus closer to the Tetanurae.