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| Gobihadros mongoliensis
Tsogtbaatar, Weishampel, Evans & Watabe, 2019
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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.
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| Fig 2. Skull and mandible of Gobihadros mongoliensis. Skull and mandible (MPC-D100/763) in left lateral (A), dorsal (B), ventral (C), and posterior (D) views.
Abbreviations: an, angular; ar, articular; at, atlas; atr, atlantal rib; ax, axis; boc, basioccipital; bsp, basisphenoid; cop, coronoid process; c3, 3rd cervical vertebra; d, dentary; exo, exoccipital; f, frontal; gl, glenoid for the lateral quadrate condyle; hy, hyoid; j, jugal; l, lacrimal; mx, maxilla; n, nasal; p, parietal; pa, palpebral; pat, proatlas; pd, predentary; pf, prefrontal; pl, palatine; pm, premaxilla; po, postorbital; poc, paroccipital process; pt, pterygoid; q, quadrate; qj, quadratojugal; rap, retroarticular process; s, surangular; scl, sclerotic ring; soc, supraoccipital; sq, squamosal; v, vomer.
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| Fig 33. Skeletal reconstructions of Gobihadros mongoliensis. Skull (MPC-D100/763) of Gobihadros mongoliensis in left lateral (A), anterior (B), dorsal (C), and posterior (D) views. Schematic reconstruction of the skeleton of Gobihadros mongoliensis (E) in lateral view.
Abbreviations: an, angular; boc, basioccipital; bsp, basisphenoid; d, dentary; exo, exoccipital; f, frontal; fm, foramen magnum; hy, hyoid; j, jugal; l, lacrimal; mx, maxilla; n, nasal; p, parietal; pa, palpebral; pd, predentary; pf, prefrontal; pm, premaxilla; po, postorbital; pt, pterygoid; q, quadrate; qj, quadratojugal; s, surangular; soc, supraoccipital; sq, squamosal.
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Systematic Palaeontology
ORNITHISCHIA Seeley, 1887
ORNITHOPODA Marsh, 1881 [42]
IGUANODONTIA sensu Sereno, 1998
HADROSAUROIDEA sensu Sereno 1998
Gobihadros nov. gen.
Gobihadros mongoliensis nov. sp.
Etymology. Hadrosauroid from the Gobi Desert of Mongolia.
Holotype. MPC-D100/746, a complete, nearly articulated skeleton from sub-locality I of Bayshin Tsav.
Locality and horizon. Bayshin Tsav (South Gobi Aimag); Khoorai Tsav (South Gobi Aimag); Khongil Tsav (East Gobi Aimag); Baynshire Formation (Cenomanian-Santonian), Upper Cretaceous.
Diagnosis. Small hadrosauroid that differs from all other non-hadrosaurid hadrosauroids (including Bactrosaurus and Gilmoreosaurus) in the presence of a premaxilla with a ‘double-layer’ oral margin and up to three functional teeth in the dentary tooth row (both convergent in Hadrosauridae). Gobihadros differs from Bactrosaurus johnsoni, Probactrosaurus gobiensis, Eolambia caroljonesi, Claosaurus agilis, Tethyshadros insularis, in the sigmoidal dorsal outline of the ilium and the greater lateral expression of the supracetabular crest. Gobihadros differs from T. insularis, Plesiohadros djaktaensis, and Hadrosauridae in the possession of a spike-like manus digit 1.
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| Fig 34. Schematic depicting the limb proportions of Gobihadros mongoliensis relative to other iguanodontians. The forelimbs of several iguanodontians on the left scaled to a generalized hindlimb on the right, following [Norman, 1980], to show differences in limb proportions. The phalangeal formula of the manus occurs below each forelimb of the corresponding taxon. Modified from Figure 81 of [Norman, 1980]. |
Khishigjav Tsogtbaatar, David B. Weishampel, David C. Evans and Mahito Watabe. 2019. A New Hadrosauroid (Dinosauria: Ornithopoda) from the Late Cretaceous Baynshire Formation of the Gobi Desert (Mongolia). PLoS ONE. 14(4): e0208480. DOI: 10.1371/journal.pone.0208480
