Tethyshadros insularis Dalla Vecchia, 2009 was originally described as an insular, pygmy hadrosauroid closely related to hadrosaurids, based on a complete and articulated specimen from the Upper Campanian–Early Maastrichtian Liburnian Formation, northeastern Italy. Recent preparation of a second specimen (SC 57247) and additional information from a third skull (SC 57026) provide important new elements on the anatomy and systematics of this taxon. T. insularis was originally diagnosed on a mosaic of primitive and derived characters, the latter particularly present in the skull, such as a long anteorbital region due to elongated maxillae and nasal bones. SC 57247 represents a 20 % larger individual based on skull length, with more massive appendicular proportions. The skull is remarkably shorter and brachyrostrine, features also present in SC 57026, displaying proportions more reminiscent of iguanodontoid-grade ornithischians rather than hadrosauromorphs. Histological thin sections from the ribs of SC 57247 indicate this larger individual is approaching somatic maturity, with the development of an incipient external fundamental system. After the reinterpretation of the holotype as pertaining to an immature individual, the systematic position of the taxon shifts more basally towards affinities with smallerbodied hadrosauroids, casting doubts on previous claims of insular dwarfism in this ornithopod dinosaur.
The first multi-individual assemblage of a Mesozoic dinosaur from Italy: systematic, osteohistological and morphological re-evaluations of Tethyshadros insularis (Dinosauria: Ornithopoda)
Fanti FSupervision
2020
Abstract
Tethyshadros insularis Dalla Vecchia, 2009 was originally described as an insular, pygmy hadrosauroid closely related to hadrosaurids, based on a complete and articulated specimen from the Upper Campanian–Early Maastrichtian Liburnian Formation, northeastern Italy. Recent preparation of a second specimen (SC 57247) and additional information from a third skull (SC 57026) provide important new elements on the anatomy and systematics of this taxon. T. insularis was originally diagnosed on a mosaic of primitive and derived characters, the latter particularly present in the skull, such as a long anteorbital region due to elongated maxillae and nasal bones. SC 57247 represents a 20 % larger individual based on skull length, with more massive appendicular proportions. The skull is remarkably shorter and brachyrostrine, features also present in SC 57026, displaying proportions more reminiscent of iguanodontoid-grade ornithischians rather than hadrosauromorphs. Histological thin sections from the ribs of SC 57247 indicate this larger individual is approaching somatic maturity, with the development of an incipient external fundamental system. After the reinterpretation of the holotype as pertaining to an immature individual, the systematic position of the taxon shifts more basally towards affinities with smallerbodied hadrosauroids, casting doubts on previous claims of insular dwarfism in this ornithopod dinosaur.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
