Redescription of a remarkably large Gryposaurus notabilis (Dinosauria: Hadrosauridae) from Alberta, Canada

Abstract

MSNM V345 is a partial skeleton of the North American hadrosaur species Gryposaurus notabilis, Lambe 1914, discovered in 1922 in the Dinosaur Park Formation of Dinosaur Provincial Park, Alberta, Canada. It was shipped in several crates to the<br/>Museo di Storia Naturale di Milano (MSNM), Italy, where it arrived in October 1958. Careless transportation during its long journey<br/>to Milan meant that the skeleton arrived extremely damaged and required heavy restoration work by MSNM staff.<br/>A preliminary study of the specimen was conducted by Vittorio Vialli in 1960 while part of it was still under preparation. That<br/>study was followed by a more detailed, although still partial, osteological description by Giovanni Pinna in 1979. On the centennial<br/>of the species’ discovery, we decided to examine the specimen in even greater detail in order to improve knowledge on the dinosaur’s<br/>skeletal anatomy and help clarify the taxonomy of the genus.<br/>Here, we redescribe the dinosaur’s osteology, focusing on unpublished elements, such as metapodials, phalanges, sacral vertebrae,<br/>and some caudal vertebrae, recently discovered to be located at the MSNM. Isolated appendicular elements found at the same quarry<br/>and tentatively referable to other individuals of the same taxon or to other dinosaur species are also briefly mentioned. Histological<br/>analysis of a core obtained from the femur revealed that it was made of fibrolamellar bone with a high number of Haversian systems.<br/>The presence of an external fundamental system indicates that the individual was fully adult at the moment of death.<br/>Of note, the skeletal remains present with traces of at least four pathological conditions: a cavity in the predentary is speculated<br/>to be the result of osteomyelitis; the fifth dorsal vertebra is fused to the left rib through a overgrowth of bone, and is interpreted as<br/>osteosclerosis subsequent to a fracture; the neural spine of the 26th caudal vertebra is fractured and healed, and the centrum has a strap<br/>of bone growing up to the side of the preceding centrum, explainable as idiopathic skeletal hyperostosis.<br/>A review of the skeletal reconstructions of the genus is also presented, followed by a summary of the skin remains and remarks on<br/>other anatomical traits. Altogether, the new data obtained on MSNM V345 have allowed us to present a more accurate and up-to-date<br/>skeletal reconstruction and in vivo restoration of G. notabilis.