from Brazil. The spinosaurines share unserrated straight teeth that are widely spaced (e.g., 12 on one side of the maxilla), as opposed to the baryonychines, which have serrated curved teeth that are numerous (e.g., 30 on one side of the maxilla). An analysis of Spinosauridae by Arden and colleagues (2018) named the clade Spinosaurini and defined it as all spinosaurids closer to Spinosaurus aegyptiacus than to Irritator challengeri or Oxalaia quilombensis; it also found Siamosaurus suteethorni and Icthyovenator laosensis to be members of Spinosaurinae. Phylogeny The subfamily Spinosaurinae was named by Sereno in 1998, and defined by Holtz and colleagues (2004) as all taxa closer to Spinosaurus aegyptiacus than to Baryonyx walkeri. The subfamily Baryonychinae was named by Charig & Milner in 1986. They erected both the subfamily and the family Baryonychidae for the newly discovered Baryonyx, before it was referred to Spinosauridae. Their subfamily was defined by Holtz and colleagues in 2004, as the complementary clade of all taxa closer to Baryonyx walkeri than to Spinosaurus aegyptiacus. Examinations by Marcos Sales, Cesar Schultz, and colleagues (2017) indicate that the South American spinosaurids Angaturama, Irritator, and Oxalaia were intermediate between Baronychinae and Spinosaurinae based on their craniodental features and cladistic analysis. This indicates that Baryonychinae may in fact be non-monophyletic. Their cladogram can be seen below. The cladogram below depicts the findings of Arden and colleagues (2018): Paleobiology Function of neural spines The function of the dinosaur's sail or hump is uncertain; scientists have proposed several hypotheses including heat regulation and display. In addition, such a prominent feature on its back could make it appear even larger than it was, intimidating other animals. The structure may have been used for thermoregulation. If the structure contained abundant blood vessels, the animal could have used the sail's large surface area to absorb heat. This would imply that the animal was only partly warm-blooded at best and lived in climates where night-time temperatures were cool or low and the sky usually not cloudy. It is also possible that the structure was used to radiate excess heat from the body, rather than to collect it. Large animals, due to the relatively small ratio of surface area of their body compared to the overall volume (Haldane's principle), face far greater problems of dissipating excess heat at higher temperatures than gaining it at lower. Sails of large dinosaurs added considerably to the skin area of their