Gilmoreosaurus mongoliensis, Gilmore, 1933

Prieto-Márquez, Albert & Norell, Mark A., 2010, Anatomy and Relationships of Gilmoreosaurus mongoliensis (Dinosauria: Hadrosauroidea) from the Late Cretaceous of Central Asia, American Museum Novitates 2010 (3694), pp. 1-52 : 4-5

G. mongoliensis Gilmore, 1933

LECTOTYPE: AMNH FARB 30735 , a complete right ilium.

REFERRED MATERIAL: AMNH FARB 30653, right maxilla; AMNH FARB 30655, left lacrimal; AMNH FARB 30656, right lacrimal; AMNH FARB 30657, partial right jugal; AMNH FARB 30658, partial right squamosal; AMNH FARB 30659, left quadrate; AMNH FARB 30660, partial right quadrate; AMNH FARB 30654, partial right dentary; AMNH FARB 30661, dentary tooth; AMNH FARB 30662 through 30669, eight maxillary tooth crowns; AMNH FARB 30670, cervical vertebral centrum; AMNH FARB 30671–30673, three nearly complete middleposterior cervical vertebrae; AMNH FARB 30674 and 30675, two anterior dorsal centra; AMNH FARB 30676 and 30677, two anterior dorsal neural arches with diapophyses and neural spines; AMNH FARB 30678, 30679, and 30680, three nearly complete vertebrae; AMNH FARB 30681 and 30682, two partial middle dorsal vertebrae; AMNH FARB 30683–30685, three partial posterior dorsal vertebrae; AMNH FARB 30686, four fused sacral neural arches with neural spines; AMNH FARB 30687, four coossified sacral centra; AMNH FARB 30688, three coossified sacral centra with partial transverse processes and neural arches; AMNH FARB 30689 through 30695, seven proximal caudal vertebrae; AMNH FARB 30696 through 30721, 26 distal caudal vertebrae; AMNH FARB 30722, 30723, and 30724, three left coracoids; AMNH FARB 30725, left scapula; AMNH FARB 30726 and 30727, two right scapulae; AMNH FARB 30728, right humerus; AMNH FARB 30729, left ulna and left radius; AMNH FARB 30730, left metacarpal IV; AMNH FARB 30731, right metacarpal IV; AMNH FARB 30732, right manual phalanx II-1; AMNH FARB 30733, right manual phalanx III-1; AMNH FARB 30734, partial left ilium; AMNH FARB 30735 and 30736, two right ilia; AMNH FARB 30737, preacetabular process of left ilium; AMNH FARB 30738, partial right pubis; AMNH FARB 30739, left ischium;

AMNH FARB 30740, right ischium; AMNH FARB 30741, right femur; AMNH FARB 30742– 30745, four left tibiae; AMNH FARB 30746 and 30747, two right tibiae; AMNH FARB 30748 and 30749, two left fibulae; AMNH FARB 30750 a left astragalus; AMNH FARB 30751 and 30752, two right astragali; AMNH FARB 30753, right calcaneum; AMNH FARB 30754 and 30755, two right metatarsals III; AMNH FARB 30756 and 30757, two right metatarsals IV; AMNH FARB 30758, left pedal phalanx II-1; AMNH FARB 30759 and 30760, two right pedal phalanges II-1; AMNH FARB 30765, left pedal phalanx II-2; AMNH FARB 30761, right pedal phalanx III-1; AMNH FARB 30762, left pedal phalanx III-1; AMNH FARB 30763, left pedal phalanx IV-1; AMNH FARB 30764, right pedal phalanx IV-1; AMNH FARB 30766, right distal pedal phalanx from digit IV; AMNH FARB 30767, left distal pedal phalanx from digit IV; AMNH FARB 30768–30773, six ungual phalanges; and AMNH 6369, a nearly complete predentary ( Gilmore [1933] originally listed this specimen as cotype of Gilmoreosaurus mongoliensis ; however, because the International Code of Zoological Nomenclature currently does not contemplate cotypes [ International Commission on Zoological Nomenclature, 1999], this specimen is here included in the hypodigm). All these bones, including the lectotype ilium, represent a minimum number of four individuals, based on the maximum number of bones from the same side of the most abundant element in the sample, the tibia.

Except AMNH FARB 6369 , all the elements were originally cataloged as a single lot as AMNH FARB 6551 . Current cataloguing practices do not provide for lot cataloging of separate individuals. Therefore, we have recataloged the individual elements as separate numbers and designated AMNH FARB 30735 , a complete right ilium, the lectotype specimen. The only evidence for association of more than one bone to a single specimen was found in the only left radius and ulna; these two elements match in size and articulate with each other in such a way that it is likely that they correspond to the same individual .

OCCURRENCE: Approximately 14 km east of the Iren Dabasu telegraph station ( Gilmore, 1933) and 14 km northeast of the town of Erenhot, Inner Mongolia (northern China), near the border with Mongolia ( Young, 1958; Godefroit et al., 1998). The two quarries (AMNH localities 145 and 149) where the bones were collected are located approximately 1 km apart from one other ( Godefroit et al., 1998) and lie in the Iren Dabasu Formation. Considerable debate has surrounded the age of this formation: it has been estimated as Early Cretaceous ( Berkey and Morris, 1927), Cenomanian ( Rozhdestvensky, 1966; 1977), pre-Turonian ( Weishampel and Horner, 1986), pre-Santonian ( Brett-Surman, 1979), Early Late Creatceous ( Godefroit et al., 1998), Early Campanian ( Jerzykiewicz and Russell, 1991; Currie and Eberth, 1993), and Maastrichtian ( Chen, 1983; Liu and Wu, 1990). More recently, Van Itterbeeck et al. (2005) restudied the stratigraphy and sedimentology of the Iren Dabasu Formation and concluded that it is most probably latest Campanian–Early Maastrichtian in age. They base this conclusion on the age provided by microfossils, particularly four species of charophytes and eight species of ostracods.

EMENDED DIAGNOSIS: Hadrosauroid ornithopod characterized by the following autapomorphies and unique combination of characters: paddle-shaped postacetabular process that is less then 70% of the length of the iliac central plate; ilium combining the presence of ischial tuberosity and supraacetabular process with apex located posterodorsal to ischial peduncle; manual phalanx III-1 with greatly asymmetrical distal surface.