Etymology: Reptile double toothed; referred to the two kinds of dentition
Etymology: Reptile double toothed; referred to the two kinds of teeth
|Systematic Palaeontology: Lepidosauromorpha; Lepidosauria; Sphenodontia;|
|Distribution: Upper strata of the Calcari di Zorzino (Norian Age)|
|Locality: Cene (Bergamo, Lombardy, Northern Italy|
|Repository: Museo Civico di Scienze Naturali "Caffi" di Bergamo|
The specimen, that represents a juvenile individual, is exposed on its ventral side, it is nearly complete and articulated, missing only the middle and posterior portions of the skull. The analysis of the skeleton identifies it as an advanced diapsid. All detectable synapomorphies suggest that it belongs to the Lepidosauromorpha, and no arcosauromorph character is present. Within the Lepidosauromorpha, many of the synapomorphies of the primitive sphenodontids are shared by the specimen: the posterior process of the dentary ends behind the coronoid, a well-developed posterior tubercle is present on the posterior margin of the ischium; the frontals are fused, posterior teeth are fully acrodont; there are less than seven premaxillary teeth. Among the Sphenodontidae the most similarities can be found in two genera - Diphydontosaurus and Planocephalosaurus. Apparently these two genera are distinguished by very few characters, mainly skull features. The evaluation of skull features in this specimen raises problems, owing to poor preservation and its probable juvenile stage. Apparently there are four premaxiliary teeth, but this cannot be stated with confidence; the anterior maxiliary and dentary teeth may bave been pleurodont, as in Diphydontosaurus. The specimen shows the same shape of the scapula of Planocephalosaurus but in the dentition a small ridge can be dedected on the dentary tooth, but no flanges on maxillary and dentary teeth, typical of this genus can be observed. In the present state of knowledge, there are no valid reasons for the erection of a new genus for this specimen, and it is tentatively ascribed to the genus Dyphidontosaurus, on the basis of the pattern of dentition.
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