Describer

Rozhdestvensky, 1966

Time

Cretaceous Early Barremian Aptian

Classification

Ornithischia Ornithopoda Iguanodontia Probactrosaurs

Diet

Herbivore

Fossilsite

Dashuigou Formation, Nei Mongol Zizhiqu, China

Length

4 > 6 meters

Info

Genus - Typespecies - Skull

Probactosaurus gobiensis (Rozhdestvensky, 1966) > Probactrosaurus alashanicus (Rozhdestvensky, 1966)

Diagnosis of genus (As for the type species)

Ornithopod reaching probable maximum body length of 4 to 6 meters; premaxillary beak amrgin ventrally defelcted; small, vertical ectopterygoid sutural facet on jugal; jugal slender; maxillary teeth narrow, with prominent primary ridge, no sunsidiary ridges; dentary teeth narrow. diamond shaped, with low, distally offset primary ridge, no subsidiary ridges, dentary teeth narrow, diamond-shaped, with low, distallyoffset primary ridge; shorter and low subsidary ridges mesially and distally; tall, interlocking teeth forming high, caudally inclined battery; two replacements crowns beneath functional teeth in dental battery, marginal denticles mammillate; prominent \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\"acromial\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\"process on anterior adge of scapula; scapular blade staight; little expanded distally; deltopectoral crest low, rounded; radius and ulna elongate; small conial pollex spine; elongate and bunched metacarpals II-IV; six fused sacral vertebrae; elongate horizontal anterior process to ilium; prepubic blade deep, distally expanded; ischium stout, curved, \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\"booted\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\", with large triangular, proximally positioned obturator process\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\'curved distal femoral shaft; distally expanded condyles on femur; anterior intercondylar groove partially enclosed. (Norman, 2002)

Specimens referred to P. gobiensis

PIN 2232/1 (holotype) , mounted partial skeleton including partial skull roof, right premaxilla; PIN 2232/1-2, left jugual, PIN 2232/1-1a, right surangular; PIN 2232/1-4, seven poorly preserved carvical vertebrae, six dorsals, four sacrals; 22 caudals, scapulae, left coracoid, right and partial left humeri, ulnae, radii, metacarpals ?11, ?III, IV and ?V, left femur, left tibia, fibilae, and left metatarsals II-IV; PIN 2232/2-9 metacarpal; PIN 2232/3-1 metacarpal; PIN 2232-9-2, partial left maxilla; PIN 2232-10, mounted partial and restored skeleton including right dentary, partial skull roof, maxilla; PIN 2232/10-2, six cervical, 18 dorsal, seven sacral, and 24 caudal vertebrae, coracoids, left sternal plate, humeri, radii, mani, ilia, ischia, pubis (acetabular fragments), femora, tibiae, fibulae, right metatarsals II-IV, left pedal phalanges (II-i-iv, IV-i-v, manual phalanx \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\"V-ii or Viii; PIN 2232/11-4 polex ungual; PIN 2232/11-5 ungual manus II; PIN 2232/17-1 skull roof; PIN 2232/18-1, partial left dentary; PIN 2232/18-5metacarpal III; PIN 2232/18-6, metacarpal; PIN 2232/18-8, phalanx manus II-i; PIN 2232/19-9 right femur; PIN 2232/10-1, left ilium; PIN 2232/21-1, humerus; PIN 2232/23-1, predentary; PIN 2232/23-2 two isolatyed dentary teeth with roots; PIN 2232/23-3 quadrate; PIN 2232/23-56, pubis; PIN 2232/24-1 worn dentary tooth; PIN 2232/27-3 scapula; PIN 2232/29-2, right ischium; PIN 2232/32-1, left tibia; PIN 2232/32-1, left tibia; PIN 2232/36-1, skull roof; PIN 2232/36-2, dentaries; PIN 2232/36-3, dentaries; PIN 2232/37-7, ?ilium (labeled P. alashanicus); PIN 2232-39-1, left femur; PIN 2232/3, left dentary with teeth; PIN 2232/2 (field number 12017), metacarpals, left ilium, and (field number 12068) metacarpal II.

Emended diagnosis

(Paul, 2007) Probably modest sized as adults. Overall lightly constructed.Premaxillary tip to anterior orbital rim/latter to paraccipital process tip length ratio ~1.1; dentary pre-coronoid process length/minimum depth ratio under 5. Premaxilla projects well below level of tooth rows, maxillary process is anteriorly shallow and posteriorly deep. Lateral temporal fenestra moderate in size. Posterior portion of jugal long. Quadrate tall, transversely narrow, shaft moderately curved, lateral foramen set high, dorso-posterior buttress small. Diastema short.

Tooth positions 23 in dentary, incipient 3rd row in many positions, battery tightly packed. Posterior dorsal centra compressed antero-posteriorly. 6 fused sacrals. Scapula blade narrow, not strongly constricted at middle of blade, base rather narrow, acromion process placed rather dorsally and directed anteriorly. Deltopectoral crest of humerus distally placed, fairly large and incipiently hatchet shaped. Forelimb very slender. Olecranon process moderate in size. Manus very narrow, digits further abbreviated, pollex spike and other unguals small. Main body of ilium deep. Prepubic process of pubis deep, postpubic process very short. Femoral shaft moderately curved. Metatarsal II shortened.
 

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

Probactrosaurus gobiensis Rozhdestvensky 1966

Locality

Maortu, Nei Mongol Province, People’s Republic of China.

Horizon

Dashuigou Formation

Age

Barremian-Albian (van Itterbeeck et al., 2004).

Comments

Two ilia show difference in the depth of the preacetabular notch, and slight difference in the ventral angulation of the preacetabular process. The lateral iliac process is a small inverted triangular thickening near the posterior end of the suprailiac crest. A narrow brevis shelf is present along the ventral edge of the large, triangular postacetabular process. The postacetabular notch is small. Laterally, the ischial peduncle is expanded onto the lateral surface of the ilium.

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