Alectrosaurus (Unmarried lizard)

Short Info

Alectrosaurus (Unmarried lizard)

Phonetic : Ah-lec-tro-sore-us.

Named By : Charles Gilmore – 1933

Diet : Carnivore

Size : Estimated 5 meters long

Type of Dinosaur : Large Theropod

Type Species : A. olseni (type)

Found in : China, Mongolia – Iren Dabasu Formation

When it Lived : Late Cretaceous, 90-70 million years ago

Alectrosaurus (/@,lektroU’so:r@s/ which translates to “alone lizard”) is one of the genus of theropod tyrannosauroid dinosaurs, which was found throughout Asia in the Late Cretaceous period, about around 996 million years old, in the present-day Iren Dabasu Formation.


Alectrosaurm olseni
Gilmore, C. W., Public domain, via Wikimedia Commons

The animal was medium-sized and moderately built bipedal carnivore that was a ground dweller with a range of 5-6 m (16 to 20 feet) and a body form like its more advanced cousin, Tyrannosaurus. Alectrosaurus was a remarkably swift-running tyrannosauroid, as evident by its elongated hindlimbs, which likely served as an animal that hunted and a trait that is believed to be lost to the more robust and advanced Tyrannosaurids.

In 1923 it was the Third Asiatic Expedition of the American Museum of Natural History headed by principal paleontologist Walter W. Granger, was searching to find dinosaur remains in Mongolia. On the 25th of April in the gobi desert Assistant paleontologist George Olsen excavated and recovered the Holotype AMNH 6554, which was a near whole right hindlimb. It included a nearly entire right hindlimb, with parts from the left pes as well as two manual unguals. In May 2004, Olsen discovered another specimen about 30 meters (98.4 feet) far from his first find, which was catalogued under the AMNH number 6368. The specimen contained an humerus on the right and two manual digits that were not complete as well as four fractured caudal vertebrae as well as three or four unidentified elements that were later discarded because of poor preservation. The discoveries were made in the Iren Dabasu Formation in what is currently known as the Inner Mongolia Autonomous Region (Nei Mongol Zizhiqu) of China.

The genus and species were described in detail and named by American paleontologist Charles Gilmore in 1933. The common term, Alectrosaurus, can be translated as “alone lizard” or “mateless lizard” and is which comes by the Greek words alektros (meaning in unmarried or alone) as well as sauros (meaning lizard). The name that is used, olseni, is in the honor of George Olsen, who discovered the first specimens.

Then, further evidence has been identified as Alectrosaurus. Two additional specimens in the Bayan Shireh Formation were reported and described by Mongolian paleontologist Altangerel Perle in 1977. This specimen IGM 100/50 is comprised of a partially maxilla, manual ungual and scapulocoracoid and the specimen IGM 100/51 is fragments of a skull that has lower jaws, as well as other parts including a ilium that is not complete, as well as metatarsals on the left foot. The fossils were discovered within Outer Mongolia. Iren Dabasu and Bayan Shireh dinosaur faunas are very similar, and it’s not surprising that a species belonging to Alectrosaurus might be discovered there. Additionally, a number of skeletons that are partial discovered throughout each of Inner as well as Outer Mongolia might belong to Alectrosaurus. Alexander Averianov and Hans-Dieter Sues 2012 have concluded that the Iren Dabasu Formation is Santonian in age, which is in line with that with the Upper Bayan Shireh Formation. Van Itterbeeck et al. 2005 suggested that the Iren Dabasu Formation is probably Campanian-Maastrichtian in age and possibly correlated with the Nemegt Formation.

Nearby to the holotype AMNH 6556 specimen AMNH 6556 was located in the same strata , but at different locations in 1923. It is composed of premaxillary and lateral teeth, a missing left lacrimaland maxillary processes in the left jugal part of the right quadratojugal, Jugal process of the right ectopterygoid, and the quadrate ramus that connects to the right pterygoid. However, the specimen may be a smaller specimen. Its relationship to Alectrosaurus isn’t completely clear since the specimen does not have hindlimbs which makes direct comparisons to Alectrosaurus extremely difficult.


Alectrosaurus Skeleton Reconstruction
PaleoNeolitic, CC BY-SA 4.0, via Wikimedia Commons

The lectotype AMNH6554 is fragmentary. It consists of an almost complete right hindlimb but lacking the distal tarsal components; left metatarsals II, III , and IV. There is also an elongated distal foot of a pubis. However, it is unclear what pubis actually represents.

The animal was medium-sized tyrannosauroid with a length of 5 and 6 meters (16 to 20 feet) and a weight range of 454 to 907 kilograms (1,001 to 2,000 lbs). In general, the hindlimbs were relatively gracile contrary to the more robust tyrannosaurids. The length of the Tibia (shinbone) and the femur (thighbone) are very similar and in contrast to the majority of Tyrannosauroids, whose Tibia is larger. The femur is 72.7 centimeters (727 millimeters) while the tibia measures is 73 millimetres (730 millimeters). The metetarsals also are larger than the tibia than other tyrannosauroids. The metetarsals are typically longer. The third is the biggest one, with a length of 48 centimeters (480 millimeters) long. The calcaneum and astragalus are both well preserved, but the astragalus appears to be somewhat damaged. They are both strongly connected but are not fused.

In keeping with the initial description of Alectrosaurus It can be identified by these characteristics that are long slender-limbed types of tyrannosauroid; humerus lengthy and slender; ungual as well as the digit I phalanx is robust with a laterally compressed shape and curving; femur and tibia are subequal in length. The astragalus length one-fourth of the length of both astragalus and the tibia.

Based on Carr in 2005 Alectrosaurus is distinguished due to the distinct characteristics that it displays in the hindlimbs like the spike-like structure which extends from the caudodorsal side in the medial condyle the femur, and the presence of a sudden increase in the size of the anterior edge of the joint’s surface for the tibia, which is located on the fibula, the tendon pit next to the ventrolateral lateral buttress of the astragalus, cutting through the medial portion of the buttress. dorsal edge of the proximal side of the pedal phalanx II-2 sharp, with a decreased pedal digit III the condyle on the lateral side of the pedal phalanx III-1 substantially deeper than the condyle on the medial side in distal views the an elongated pedal phalanx IV-2 that is stocky, when examined from a proximal perspective and the dorsal portion of the joint’s surface metatarsal IV and metatarsal III appears to be slightly dilated in the front, and numerous other.

Source: Wikipedia