Describer

Maleev, 1955

Time

Cretaceous Late Campanian Maastrichtian

Classification

Saurischia Theropoda Tyrannosauria Tyrannosauridae

Diet

Carnivore

Fossilsite

Nemegt Formation, Mongolia

Fall Under

Tarbosaurus

Info

Skull

Tarbosaurus bataar (Maleev, 1955) = Tyrannosaurus bataar * (Maleev, 1955) > Tarbosaurus efremovi (Maleev, 1955) Gorgosaurus lancinator (Maleev, 1955) ? Albertosaurus periculosus (Riabinin, 1930) ?Tyrannosaurus turpanensis (Zhai, Zheng, & Tong, 1978) * Jenghizkhan (Olshevsky vide Olshevsky, Ford & Yamamoto, 1995)

(\\\\\\\"Efremov\\\\\\\'s frightening lizard\\\\\\\") for a nearly complete skeleton about 10-12 meters long (PIN 551-2)

Barsbold, 1983

Holotype

PIN no. 551-2; skull and postcranial skeleton.

Description

Massive, high skull, laterally compressed. Relatively small maxillary fenestra. Premaxilla with ventral process. Large, high maxilla. Basisphenoid capsule absent. Basipterygoid processes massive, elongated, and directed anteroventrally. Mobile basipterygoid articulation. Parabasal canal and osseous middle ear absent. Lateral wall of braincase composed of three auditory bones and the laterosphenoid, which are connected by a complex suture with the temporal.

The coronoid almost reaches the lower jaw symphysis, with a groove-like, mobile articulation that connects the anterior and posterior sections of the lower jaw. Large teeth with anterior and posterior serrations, and a blunt apex. The postcranial skeleton is remarkable for its gigantic size. Ten cervical vertebrae, 13 dorsals, and 5 sacrals.

Caudal vertebrae with elongate prezygapophyses. Sternum absent. Scapulocoracoid relatively large, mostly at the expense of the elongated scapular blade. Fairly high [ilium], with [bifurcate] anterior and narrower posterior processes. Pubis with massive distal end, whose anteroposterior length reaches 2/3 the length of the shaft.

Ischium slightly shorter than pubis, with a proximally placed obturator process and narrow distal end. The manus has a non-pulley carpus, with a reduced metacarpal III and remains of the basal phalanx of digit I. Metatarsal III highly laterally compressed, and practically excluded from the ankle joint.

Comparisons

According to absolute dimensions, Tarbosaurus can be completely equated with the American Tyrannosaurus, however the skull was less massive and more extended in the former, the configuration of the elements comprising the skull is somewhat different, and the teeth are highly laterally compressed.

From the representatives of other closely related tyrannosaurid genera – Albertosaurus and Daspletosaurus – Tarbosaurus is differentiated by the general proportions, the absence of bony extensions from the skull, different relationships and configurations of the rostral and post-rostral skull regions, and the shape and construction of the teeth (Russell, 1970).

Discussion

Rozhdestvensky (1965) placed the various Mongolian tyrannosaurids into a single species, Tarbosaurus bataar (Maleev, 1955), which seems to merit attention in the context of new materials. At the same time, types existed that differed greatly from Tarbosaurus and also from Tyrannosaurus, because they have a larger skeleton and also different limb proportions, numbers of teeth, and details of skull construction, apparently on the example of Alioramus (Kurzanov, 1974). All this assumes a considerable variety in tyrannosaurids, and their Mongolian representatives in particular. However, systematic independence of some tyrannosaurids must be refined based on more complete materials. The brevity of the given characteristics of Tarbosaurus is conditional on the details in the existing literature (Maleev, 1974).

Material

Complete skull and well preserved postcranial skeleton of one specimen (no. 100/59), and also skull and skeletal fragments of others with varying preservation.

From: Maleev, E. A. (1955). [New carnivorous dinosaurs from the Upper Cretaceous of Mongolia]. Doklady Akad. Nauk S.S.S.R. 104: 779-783. (In Russian)

Translated by F. J. Alcock

Type of genus

Tarbosaurus efremovi sp. nov.

Diagnosis of genus

The diagnosis was made on the basis of the study of the skull and the postcranial skeleton of Tarbosaurus efremovi. These were large carnivorous dinosaurs attaining the length of 10 to 12 m and from 4.2 to 5.0 m in height. The skull (Fig. 1) – large, massive, with 2 large premaxillary foramina and a third small foramen between the premaxilla and maxilla. The orbits – large, and pisolitic. Maxilla long, raised. and equipped with powerful saber-like teeth, slightly compressed and serrated marginally. In the transverse cross-section the teeth were oval, elongated, and the anteroposterior diameter surpasses the transverse one. All the teeth are dissimilar; each tooth differs slightly in the larger or smaller labial position of the serrated termini, and in the size of the crown. Premaxilla bears 4teeth, maxilla 12, dentary 15 teeth, and the largest tooth attains 112 mm. The interdental plates of the alveoli rise from 1.5 to 2 cm in the form of triangular plates.

The neck is short and consists of 8 to 9 vertebrae. The cervical vertebrae are opisthocoelous, short, and broad. The articulated surfaces of the centra are inclined, and the posterior surface is more slanted than the anterior. The dorsal vertebrae are amphicoelous or slightly procoelous, the centra were tall and strongly laterally compressed. The thoracic ribs are long, strongly curved in the upper part, and slant convex medially. The ventral ribs [abdominal] were represented by a central rib and a whole series of lateral ribs. The forelimbs are reduced. Scapula long, narrow, the coracoid short, broad. Humerus very short and equipped with a strong deltopectoral crest; the proportion of the length of humerus to the length of the scapula 3:1. Radius and ulna thin, short; the proportion of ulna to humerus 3:1. Manus short with two digits (I, II). The digits terminated in strongly curved, sharp claws. The pelvis girdle developed very strongly and excels the dimensions of the skull. Ilium tall, long. Pubis massive. Pubic symphysis strongly elongate anteriorly and curved ventrally forming a powerful bony foot, suggesting an enormous pressing iron in shape. Ischia long, broad in proximal part, but tapering ventrally. Femur massive, long with well-developed head. The proportion of the femur length to the length of humerus 1:4. Tibia massive, strong. The proportion of the femur\\\\\\\'s length to tibia 1:1. Metatarsals massive, long. The proximal part of Mt3 extremely tapered and solidly compressed between lateral metatarsals. Pes massive. Only three digits are well developed (II, III, IV). The first digit developed rather poorly. The phalanges of the claws strong, sharp. Tail long, and consists of at least 35 to 45 vertebrae.

Comparative Notes

According to the absolute measurements of Tarbosaurus efremovi it is smaller than Tyrannosaurus rex (Osborn, 1905), and Tyrannosaurus bataar (Maleev, 1955) Skull less massive and more elongated. Teeth more compressed laterally. Forelimbs shorter. The Mongolian form differs from Gorgosaurus libratus (Lambe, 1914) and Gorgosaurus sternbergi (Matthew & Brown, 1923) by the huge size of the skull, the absence of the bony projection on the lacrimal, by the pisolitic orbit, and by the extremely reduced forelimbs (Tarbosaurus). All of these characteristics compel us to regard the described form as a new genus of the family [Deinodontidae], to be referred to as Tarbosaurus gen. nov. (Gorgosaurus lancensis (Gilmore, 1946), Gorgosaurus lancinator sp. nov., Gorgosaurus novojilovi sp. nov. differ greatly in the structure of their skull and are smaller in size than Tarbosaurus efremovi).

The complex of species of the genus Tarbosaurus consists of a single species, T. efremovi sp. nov. (The diagnosis of the species coincides with that of the genus Tarbosaurus).

Type of species

Skull and postcranial skeleton. Collected by the Paleontological Institute, Academy of Sciences USSR, #551-2.

Locality

Nemegt, 350 km WSW of the center of Dalan-Dzadagad, Mongolian People’s Republic.

Period

Upper Cretaceous.

Material

The excavation conducted in the years 1948-1949 in the main basin of Nemegt resulted in obtaining 4 almost complete skeletons and many miscellaneous bones. The bones were well preserved and white in color. Numerous remains were also found in the site of Tsagan- Ula, approximately 60 km west of Nemegt.
 

• < Prev
• Next >