Describer

Norman, 1998

Time

Cretaceous Early Aptian Albian

Classification

Ornithischia Ornithopoda Iguanodontia Iguanodontidae

Diet

Herbivore

Fossilsite

Khukhtekskaya Svita , Dundgov, Ovorhkangai, Shinekhuduskaya Svita, Dundgov, Mongolia

Length

7-8 meter

Info

Genus - Typespecies - Skull

Altirhinus kurzanovi (Norman, 1998) > Iguanodon mongoliensis (Whitfield, 1992) >> \\\\\\\"Iguanodon orientalis\\\\\\\" (Rozhdestvensky, 1952)

Diagnosis of genus (as for the typespecies) \\\\\\\"Iguanodontid\\\\\\\" late Aptian/early Albian age; body size up to 8 meters in length, with anatomical similarities to Iguanodon bernissartensis, nasal bones strongly dorsally flexed, with elongate rostral process; internasal groove; premaxillarly beak ventrally deflected; occluded antorbital fenestra; rostral end of dentary downturned; deeper portions of maxilla and dentary supporting three teeth in vertical tooth row; large, conial, laterally compressed ungual phalanx of manual digit I; carpus not co-ossified; manual digit IV having short, broad ungual; ilium with robust, downturned rostral process, sinuous dorsal margin, strongly everted trochateric edge above ischial tuber, brevis shelf absent; shaft of ischium straight, parallel-sided, showing axial twist. (Norman and Sues , 2000)

Holotype: PIN 3386/8 (some elements numbered 3388), cranial remains including much of left side of well-preserved skull, right side of skull crushed, damaged, and represented by isolated right nasal, predentary, dentary, pterygoid fragments, quadrate, squamosal, postorbital, jugal, surangular, angular, prearticular, and paroccipital wing), postcrania including left and right atlas neural arches, left scapula, left coracoid, pubis, ischia, manus digit V, ungual of manuses IV and III, three pedal phalanges including one ungual.

This genus was erected to contain the big-nosed iguonodont that has usually been incorrectly referred to \\\\\\\"Iguanodon orientalis\\\\\\\". Known from a fairly complete skull, parts of another skull and jaw, and various parts of the skeleton from three adult individuals and two possible juveniles.

The name means \\\\\\\"high snout named \\\\\\\"in recognition of the highly arched nasal bones of the skull which give the snout of this animal a distinctively elevated profile\\\\\\\"; for a large (7-8 m. (23-26 ft.)) iguanodont from Khuren Dukh, Dornogov (East Gobi Province), south-central Mongolia, notable for the unusual expanded shape of its snout.

The name \\\\\\\"Iguanodon orientalis\\\\\\\" was originally proposed based jaw fragments from Mongolia that appear to belong to an animal distinct from the new \\\\\\\"high-snouted\\\\\\\" iguanodont; Norman (1996) considered Rozhdestvensky\\\\\\\'s type material to poor for diagnoses \\\\\\\"Iguanodon orientalis\\\\\\\" in a scientifically useful way.

Emended diagnosis: (Paul, 2007) Adults large. Overall lightly constructed. Premaxillary tip to anterior orbital rim/latter to paraoccipital process tip length ratio ~1.6 via elongation of posterior nasal, maxillary process of premaxilla and maxilla; dentary pre-coronoid process length/minimum depth ratio under 5. Premaxilla and nasal form large crest.

Premaxilla projects well below level of tooth rows, maxillary process is moderately deep. Dorsal apex of maxilla set posteriorly. Antorbital fossa small. Lacrimal long, contacts nasal. Accessory palpebral absent. Lateral temporal fenestra moderate in size. Posterior portion of jugal long. Quadratojugal tall. Quadrate short, transversely narrow, shaft straight, lateral foramen set high, dorso-posterior buttress absent. Diastema short.

Tooth positions 26 in maxilla, 24 in dentary, incipient 3rd row in many positions. Scapula blade narrow and constricted at middle of blade, base rather narrow, acromion process placed rather dorsally. Deltopectoral crest of humerus distally placed, modest in size. Manus narrow, pollex spike and other unguals moderate in size. Anterior prong of ilium robust, strongly arced ventrally, main body deep. Prepubic process of pubis moderate in depth.

---

Carpenter & Ishida (2010) Early and “Middle” Cretaceous Iguanodonts in Time and Space Journal of Iberian Geology 36 (2) 145-164

Altirhinus kurzanovi, Norman 1998.

Locality: near Choyr, Mongolia.

Horizon: Khuren Dukh Formation (= Shinekhudag Formation as used by Hicks et al., 1999).

Age: middle - late Albian (Hicks et al., 1999; Ito et al.,2006; Nichols, et al., 2006).

Comments: The ilium is characterized by a deep body, short, tapering, rounded postacetabular process with a prominent postacetabular notch. The preacetabular process is sharply angled ventrally, but there is still a wide preacetabular notch. A prominent triangular lateral process is located along the lateral iliac crest. The ischial peduncle lacks the lateral expansion onto the lateral surface of the ilium seen in more derived iguanodonts.

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