The anterior part is very expanded, forming the typical spinosaurid rosetta, being most constricted between the 6th and 7th alveoli. This terminal expansion of Oxalaia is similar to that observed in Suchomimus and Cristatusaurus by having the lateral margins getting gradually thinner posteriorly, lacking the small constriction present between the 3rd and 4th alveoli in the Algerian spinosaurid (MNHN SAM 124) and Spinosaurus cf. S. aegyptiacus that in those taxa give the anterior portion of the rosetta a rather triangular shape (Dal Sasso et al. 2005: Fig. 1b, Taquet and Russell 1998: Fig. 1a). Ventrally, the maxillae extend anteriorly, forming two elongated processes that are encased laterally by the premaxillae. These rostral extensions of the maxillae, which border a triangular opening, are rather thin and less exposed ventrally compared to other spinosaurids (e.g., Suchomimus, the Algerian spinosaurid, Cristatusaurus). The bone surface of this portion of the premaxillae is well ornamented, differing from the smoother condition observed in other spinosaurids. Except for the replacement teeth, no tooth shows the apical portion of the crown. Teeth fragments are present in the 3rd and 5th alveoli of the right side and in the 2nd and 3rd alveoli of the left side. All preserved portions lack serrations. Where observable, the teeth are not lateromedially compressed as in other theropods (e.g., Currie et al. 1990), but show an oval transverse section, a typical feature of spinosaurid teeth (e.g., Stromer 1915, Kellner and Mader 1997). In the 3rd alveolus of each side, two replacement teeth are present, an unusual feature within theropods (Fig. 3 a). Other replacement teeth are found in the 1st, 2nd, 3rd and 6th alveoli of the left side and on the 2nd and 3rd of the right side. The more apical section of the crown of the replacement teeth is straight, slightly flattened labiolingually. The interdental plates are prominent especially between the 2nd and 3rd; and 3rd and 4th alveoli.