Abstract
A new genus and species of non-hadrosaurid hadrosauroid, Gobihadros mongoliensis, is described from a virtually complete and undeformed skull and postcranial skeleton, as well as extensive referred material, collected from the Baynshire Formation (Cenomanian-Santonian) of the central and eastern Gobi Desert, Mongolia. Gobihadros mongoliensis is the first non-hadrosaurid hadrosauroid from the Late Cretaceous of central Asia known from a complete, articulated skull and skeleton. The material reveals the skeletal anatomy of a proximate sister taxon to Hadrosauridae in remarkable detail. Gobihadros is similar to Bactrosaurus johnsoni and Gilmoreosaurus mongoliensis, but can be distinguished from them in several autapomorphic traits, including the maximum number (three) of functional dentary teeth per tooth position, a premaxillary oral margin with a ‘double-layer morphology’, and a sigmoidal dorsal outline of the ilium with a well-developed, fan-shaped posterior process. All of these characters in Gobihadros are inferred to be convergent in Hadrosauridae. Phylogenetic analysis positions Gobihadros mongoliensis as a Bactrosaurus-grade hadrosauromorph hadrosauroid. Its relationship with Maastrichtian hadrosaurids from Asia (e.g., Saurolophus angustirostris, Kerberosaurus manakini, Wulagasaurus dongi, Kundurosaurus nagornyi) are sufficiently distant to indicate that these latter taxa owe their distribution to migration from North America across Beringia, rather than having a common Asian origin with Go. mongoliensis.
Highlights
Ornithopod dinosaurs have been known since before the concept of Dinosauria originated [1, 2]
The present paper describes a new, derived hadrosauroid taxon, Gobihadros mongoliensis gen. et sp. nov., which is the only non-hadrosaurid taxon known from the early Late Cretaceous (Santonian) of the Gobi Desert in Mongolia
Non-hadrosaurid hadrosauroids from the Late Cretaceous are relatively rare, but are significant for understanding the sequence of character acquisition in the origin of Hadrosauridae and their historical biogeography
Summary
Ornithopod dinosaurs have been known since before the concept of Dinosauria originated [1, 2]. Of particular importance to the understanding of ornithopod evolution is the plethora of new species of hadrosauroids phylogenetically nested between Iguanodon and the origin of Hadrosauridae that have been described in the last two decades (e.g., [14,15,16,17,18,19,20,21,22,23,24,25]). Most of these new taxa are known from the Early Cretaceous of China, a few are known from the Late Cretaceous. These new discoveries, together with a resurgence of phylogenetic interest in the group, have resulted in a better understanding of the origin of Hadrosauridae (= the least inclusive clade containing Hadrosaurus foulkii Leidy and Lambeosaurus lambei Parks, sensu [26]), but have produced a series of conflicting or poorly-resolved phylogenetic hypotheses of the relationships within Hadrosauroidea (e.g., [9, 11,12,13, 18, 23, 26,27,28,29])
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