Spinosaur taxonomy and evolution of craniodental features: Evidence from Brazil

PLoS One. 2017 Nov 6;12(11):e0187070. doi: 10.1371/journal.pone.0187070. eCollection 2017.

Abstract

Fossil sites from Brazil have yielded specimens of spinosaurid theropods, among which the most informative include the cranial remains of Irritator, Angaturama, and Oxalaia. In this work some of their craniodental features are reinterpreted, providing new data for taxonomic and evolutionary issues concerning this particular clade of dinosaurs. The mesial-most tooth of the left maxilla of the holotype of Irritator is regarded as representing the third tooth position, which is also preserved in the holotype of Angaturama. Thus, both specimens cannot belong to the same individual, contrary to previous assumptions, although they could have been the same taxon. In addition, the position of the external nares of Irritator is more comparable to those of Baryonyx and Suchomimus instead of other spinosaurine spinosaurids. In fact, with regards to some craniodental features, Brazilian taxa represent intermediate conditions between Baryonychinae and Spinosaurinae. Such a scenario is corroborated by our cladistic results, which also leave open the possibility of the former subfamily being non-monophyletic. Furthermore, the differences between spinosaurids regarding the position and size of the external nares might be related to distinct feeding habits and degrees of reliance on olfaction. Other issues concerning the evolution and taxonomy of Spinosauridae require descriptions of additional material for their clarification.

MeSH terms

  • Animals
  • Brazil
  • Dinosaurs / anatomy & histology
  • Dinosaurs / classification*
  • Fossils*
  • Geology
  • Humans
  • Paleontology
  • Skull / anatomy & histology*
  • Tooth / anatomy & histology*

Grants and funding

The first author received a Ph.D. grant from the Conselho Nacional de Desenvolvimento Científico e Tecnológico (Grant 141268/2013-1) and a short-term research grant from the Deutscher Akademischer Austauschdienst (Grant 57130097). The informed funders provided support for data collection throught visits to scientific paleontological collections in Brazil and Europe.