Aralosaurus ‭(‬Aral lizard‭ ‬-‭ ‬after the Aral sea‭)

Short Info

Aralosaurus ‭(‬Aral lizard‭ ‬-‭ ‬after the Aral sea‭)

Phonetic : Ah-ral-o-sore-us.

Named By : Anatoly Konstantinovich Rozhdestvensky‭ ‬-‭ ‬1968

Diet : Possibly Herbivore (Uncertain due to lack of fossil material)

Size : Estimated 8 meters long

Type of Dinosaur : Euornithopod

Type Species : A.‭ ‬tuberiferus‭ (‬type‭)

Found in : Kazakhstan

When it Lived : Late Cretaceous, 94-84 million years ago

Aralosaurus was one of the genus’s of hadrosaurid dinosaurs that lived in the Late Cretaceous in what is today Kazakhstan. It is recognized only through the posterior half of the skull (devoid of its mandible) and a few bones from the post-cranial region discovered inside the Bostobe Formation in rocks dated from the Lower Campanian-Upper Santonian boundary, around 83.6 Ma (millions of years). One species is identified, Aralosaurus tuberiferus, described by Anatoly Konstantinovich Rozhdestvensky in the year 1968. The genus name translates to Aral Sea lizard, because it was discovered to east of Aral Sea. Tuberiferus refers to having a tuber due to the fact that the posterior portion that is the bone of the nasal rises dramatically over the orbits as an outgrowth. Aralosaurus was first reconstructed using an arch in the nasal area like the one in North American Kritosaurus (a comparison that is based on a specimen currently classified within the family of Gryposaurus). For a long time, Aralosaurus was thus placed within the clade known as Hadrosaurinae. The classification was retracted in 2004 after a re-examination of skulls of this animal that enabled the identification in Aralosaurus numerous typical characteristics of Lambeosaurinae. Particularly, this study found that Aralosaurus was a bony hollow structure that was located in front of the orbits that was in contact with breathing tract. The structure is damaged at its bottom and its size are still unknown. In recent times, Aralosaurus has been identified as the basal Lambeosaurinae and grouped with its closest cousin Canardia of the higher Maastrichtian in France as part of the new Clade of Aralosaurini.

Aralosaurus skull
I. Reid (User:IJReid), Public domain, via Wikimedia Commons

The skull fragments of Aralosaurus was discovered in the year 1957 close to the Shakh-Shakh location during an Soviet exploration in Central Kazakhstan (which in the past was part of USSR). Along with the skull (which is missing the majority of the snout, and the mandible as a whole) it also contained isolated teeth as well as postcranial structures that were often fragmentary (ulna radius, femur, radius and tibia, as well as the fibula astragalus, metatarsals). The only elements that were complete were a humerus and metatarsal. It was not until 1968 that Rozhdestvensky identified and named the animal. The skull’s size was estimated by Rozhdestvensky to be around 65 cm, and the overall size of the animal as around 6.5 meters long. Because the cranial sutures were not fusion-proof the specimen is likely undeveloped. In the early days, Rozhdestvensky argued that the skull of Aralosaurus showed the closest similarity to that of Kritosaurus due to the existence an arch in the nasal area the front of the orbits (the similarities were based on skulls that are attributed to Gryposaurus and not Kritosaurus). Therefore, the animal was classified as a member of the Hadrosaurinae that are the only hadrosaurs that lack a the cranial crest, or having the presence of a bony crest.

In 2004 The skull of Aralosaurus was examined again by Godefroit and his colleagues According to their findings the bones fragments that were identified by Rozhdestvensky as being the middle portion of the arch nasal as well as the posterior part of the premaxilla are believed to have disappeared. These bones were previously in isolation, while the rest part of the skull was articulated (including the posterior portion that was part of the nasal). Therefore, it is not possible to verify the existence of an arch on the nasal of Aralosaurus. However this study demonstrates that Aralosaurus was not a gryposaur like hadrosaurine as the claimed nasal boss was actually part of hollow structure. Godefroit and his colleagues didn’t find any characteristic features in Aralosaurus. However Aralosaurus’ skull Aralosaurus has several distinct characteristics (in the maxilla and the parietal and squamosal regions, but most notably the nasal) which suggests its position in the Lambeosaurinae. In particular, the posterior portion of the nasal is clearly articulated with the rest of the skull appears just before the orbits and forms or an elongated crest that is hollow. Since this structure is fractured at the base, it isn’t easy to determine its dimensions and shape. But, when viewed from a rostral perspective it is clear that the nasal area is hollow and is and rostrally excavated by a large groove that is directly connected to the ventral aspect of the posterior section of bone. This is why it is clear the fact that within Aralosaurus it is the nasal crest that is an element of respiratory systems. The expansion in the nasal cavity in the hollow crest is usually an osauririne characteristic, making it clear that there is a place for Aralosaurus in the group of. Aralosaurus also has several facial features that indicate it was a member of the basal part within the group. Even though it has a hollow nasal structure, it was situated directly in the front of the orbits. This was an early position for lambeosaurines. In the most advanced forms from the group, it is observed that the nose moves towards a caudodorsal location because of the crucial growth of the premaxillae in these types of. Additionally, in developed lambeosaurines the skull roof is modified in order to form an anchoring zone to support the hollow crest while the crest in Aralosaurus it’s skull’s roof is not subject to any specific modification. The size and shape of the crest-like structures of Aralosaurus is not known. The fragments, which were originally thought to be part of the nasal arch of a gryposaur and might have been able to recreate the circumnarial region of Aralosaurus however, are now lost. Thus, the discovery of more complete pieces is crucial to gain a better understanding of the form and dimensions of the hollow structure.

Aralosaurus had a bulge of low size in the front of its eyes as did Hadrosaurus. It was possible to inflate it as balloons, which would create an obnoxious sound, which might have been used for visual identification, to alert predators to keep away or to draw partners. They cut down twigs, flowering plants and leaves using their beaks that were toothless and then chewed them with their teeth grinding back. They were like Maiasaura and might have taken care of their babies in communal nesting areas and moved in herds to provide protection.

Source: Wikipedia