Several Teleosaurus skulls were described during the nineteenth century. Unfortunately, all skulls from this genus were destroyed during World War II. The only available skull is currently preserved in the MNHN. Thanks to a new preparation, new anatomical features can be seen, such as the morphology of the nasal cavity, the external otic recess, and the distribution of the foramina for the cranial nerves. A phylogenetic analysis is presented, including 14 thalattosuchian taxa. This analysis has generated four equally most parsimonious trees, where the thalattosuchians are closely related to the pholidosaurids and dyrosaurids, forming a longirostrine taxa. These relationships have been often considered to be based on homoplasies, related to the longirostrine morphology. This is also suggested herein, as the deletion of the longirostrine dependant characters or of the most longirostrine thalattosuchians in the analysis provide a consensus tree where thalattosuchians are basal crocodyliforms, a result more generally accepted. As the deletion of the most longirostrine thalattosuchians precludes the longirostrine problem in the phylogenetic analysis of Crocodyliformes, this deletion seems to be the less unsatisfactory solution to assess the crocodyliform relationships. The phylogenetic analysis also provides interesting information on the thalattosuchian relationships: Teleosaurus is the basal-most thalattosuchian, Teleosauridae is paraphyletic and Pelagosaurus is neither the basal-most thalattosuchian nor the basal-most metriorhynchid. The metriorhynchid relationships support previous works, as ‘Teleidosaurus’ is paraphyletic and the basal-most metriorhynchid, Metriorhynchus is more closely related to other metriorhynchid than ‘Teleidosaurus,’ and Enaliosuchus, for which the relationships are tested for the first time, is the sister taxon of Dakosaurus. Geosaurus is the sister taxon of the clade Dakosaurus Enaliosuchus.