Segnosaurus ‭(‬Slow lizard‭)

Short Info

Segnosaurus ‭(‬Slow lizard‭)

Phonetic : Seg-no-sore-us

Named By : Altangerel Perle‭ ‬-‭ ‬1979

Diet : Herbivore

Size : Estimated 4 – 6 meters long

Type of Dinosaur : Large Theropod

Type Species : S.‭ ‬galbinensis‭ (‬type‭)

Found in : Mongolia,‭ ‬Bayan Shireh Formation

When it Lived : Late Cretaceous, 97-88 million years ago

Segnosaurus is the name given to a species in therizinosaurid dinosaurs which lived in the area that is today the southeastern region of Mongolia in the Late Cretaceous, about 102-86 million years ago. A number of fragments that were not preserved were found inside the Gobi Desert in the 1970s. Then, in 1979, the genus and species Segnosaurus galbinensis were identified. The name used for the species is generic. Segnosaurus is a reference to “slow lizard” and the specific name galbinensis refers to the Galbin region. The most well-known parts of this dinosaur comprises the lower jaw the spine vertebrae, neck and the tail as well as the pelvis, shoulder girdle and the bones of the limbs. Some of the specimens are missing or injured since being taken.

Segnosaurus skeletalIJReid, CC BY 4.0, via Wikimedia Commons

Segnosaurus was a massive-bodied therizinosaur which is believed to have measured between 6 to 7 meters (20-23 feet) in length and to weigh about 1.3 tonnes (1.4 shorter tons). It was likely to have been bipedal with its trunk body inclined towards the upwards. Its head had a small size, with a beaks at the tips of the jaws. its neck was broad and slim. Lower jaws were turned down to the front and the teeth were distinct by having denticles in addition to in third cut edges on certain of the teeth in the back. The forelimbs are strong as they had 3 fingers that had large claws. the feet were supported by four toes. the feet. Apart from therizinosaurs Theropods all had feet with three toes. The pelvis’s front was designed to support an enlarged belly. The bone of the pubic was flipped to the back, a characteristic that is seen only in birds and dinosaurs that are the closest relatives to them.

The affinity of Segnosaurus were at first a mystery, and it was given its own family of theropods, Segnosauridae as well as, later on, when similar genera were identified as an infraorder Segnosauria. Other classification schemes were considered until more detailed relatives were discovered in the 1990s. This confirmed their status as theropods. The fossils that were discovered in the 1990s also proved Segnosauridae was a synonym junior of the previously-named family Therizinosauridae. Segnosaurus and its close relatives are believed to be slow-moving animals which, as evidenced by their peculiar appearance, were mostly herbivores and a majority of other groups of theropods were carnivores. Therizinosaurs likely used their lengthy forelimbs, necks, and beaks while hunting, as well as huge guts to process food. Segnosaurus is located in the Bayan Shireh Formation, where it was found in the same area as of therizinosaurs Erlikosaurus and Enigmosaurus These related genera may have been niche-divided.

A joint Soviet and Mongolian expedition that was investigating the Bayan Shireh Formation at the Amtgay location located in the Gobi Desert in the southeastern part of Mongolia discovered fossils, which included the skeleton fragments of a dinosaur that was not known to the public. Between 1974 and 1975, further remains were discovered within Khara-Khutul and Amtgay and Khara-Khutul locales Although the skeletons were not complete, the bones were preserved well. Other locales mentioned in the literature are Bayshin-Tsav and Urilbe-Khuduk. The fossils were first described scientifically in 1979 by paleontologist Altangerel Perle, who named the new species and genus Segnosaurus galbiensis. The name of the generic species comes of segnis, which is the Latin term segnis (“slow”) as well as”slow”) and Ancient Greek sauros (“lizard”). The particular name is a reference specifically to the Galbin region in the Gobi Desert.

The holotype specimen of the Amtgay locality is kept in the Mongolian Academy of Sciences under the specimen number IGM 100/80 (Mongolian Institute of Geology, also known as GIN). It comprises mandible (lower jaws) as well as an incomplete humerus with a fully-formed radius and the ulna (lower arm bone) as well as phalanges of fingers and forelimbs, a forelimb ungual (claw bone) as well as a nearly-complete pelvis and a femur that is not complete. It also includes an incomplete right with six sacral vertebrae 10 caudal vertebrae that are located at towards the back of the tail 15 from the back of the tail the gastral rib’s first gastral, and fragments of dorsal ribs. Two additional specimens were identified as paratypes: IGM 100/82 and IGM 100/82 of Khara Khutul. Khara Khutul locality includes a fibula, tibia, and femur (leg bones) as well as metatarsals and tarsals five toe phalanges that include the foot ungual and rib fragments, a full ilias, top portion of an ischium, as well as the lower section of the pubis. The specimen IGM 100/83 has the left scapulocoracoid (shoulder girdle) and an ulna, a radius forelimb ungual, and the fragment of cervical (neck) vertebra. In the year 1980, Perle and the paleontologist Rinchen Barsbold assigned a different sample in the same group to Segnosaurus; IGM 100/81 from the Amtgay location contained an left tibia and a fibula.

The year 1983 was the first time Barsbold added additional samples 100/87, 100/88. In 2010 however, paleontologist Lindsay E. Zanno suggested they could refer to Paratypes IGM 100/82 or IGM 100/83 (which were already identified in 1979) since the translation from Russian to English of the article by Barsbold has numerous typographical errors pertaining specific specimen numbers. Zanno also pointed out that by the time she conducted her research there were numerous issues in the Segnosaurus IGM specimens, such as damage that occurred by collection, the disappearance of elements belonging to the holotype and incorrect the identification of the assigned elements plus more than one person with the same specimen number. Holotype elements Zanno could access in 2010 comprised an extremely damaged ilium and a sacrum that was missing right sacral ribs, which had the result that it could not connect well with the remainder of the Ilium, and an ischium and pubic bone lacking their upper sections. Other bones that bear the specimen code IGM 100/82 were found, but weren’t mentioned in Perle’s description. Likewise, the location of some paratype elements was not known. In a re-description from 2016 of the mandible that was holotype that had not been studied in the years since its discovery, Zanno and colleagues reported that the majority of the tooth crowns were damaged following their collection, and a majority of them had missing tips. The the hemimandibles (halves of lower jaw) the right one is near complete, however only the backmost part as well as the front portion of the mandibular symphysis (the part where the two mandible halves connect) is missing. The left hemimandible is broken and still has the front part with some bone displacement because of crushing.

Source: Wikipedia