Pronunciation: jak-SAH-toe-SOR-us
Meaning: Jaxartes [River] lizard
Author/s: Riabinin (1938)
Synonyms: None known
First Discovery: Kyrkkuduk, Kazakhstan
Discovery Chart Position: #176
Jaxartosaurus aralensis
Due to wildly conflicting information regarding its name, classification, possible synonyms and place of discovery, coupled with the fact that the paper in which it was initially described is seemingly nowhere to be found, Jaxartosaurus is the dinosaur where most self-respecting DinoCheckers fear to tread. Fortunately, self respect has never been our strong point. Here's the skinny, from what we can gather.
Based on a veritable hotch potch of remains from various localities across southern Kazakhstan, Anatoly Nikolaenvich Riabinin named Jaxartosaurus aralensis in 1939. The limb bones which were assigned here appear to offer nothing to its diagnosis, not that it matters, because they've been lost anyway, but the skull is choc-a-bloc with unique features and non-pronounceable words that we won't bore you with. Suffice to say, it was wide and low with distinct sutures between the bones which suggests it was a juvenile. It's a bit difficult to evaluate the shape of its crest because the crest itself was not preserved. However, the shape and size of the bones to which a crest would have been attached are similar to those of the helmet-crested Corythosaurus from Alberta, so Jaxartosaurus probably sported a helmet crest too, but somewhat thicker.
Juveniles of most specimens often find themselves sunk into other genera somewhere down the line, but Jaxartosaurus bucked this trend by taking on remains that were previously known as Tanius prynadai and Bactrosaurus prynadai that Riabinin managed to name in 1939 based on the exact same remains, and parts of Procheneosaurus convincens (a fairly complete skeleton that spent a short time as Corythosaurus convincens). Unsuprisingly, not all experts agree, and Procheneosaurus convincens may be worthy of its own generic name.
Because the likes of Jaxartosaurus and Aralosaurus of Kazakhstan, Tsintaosaurus of eastern China, and Amurosaurus of eastern Russia are the most basal and/or oldest lambeosaurine and saurolophine hadrosaurids, some experts reckon that the hadrosaur ancestor arose in Asia. Its descendants may have migrated into Western North America over a land bridge called the Beringian Isthmus and into Europe via a temporary opening of the Turgai Strait (aka the Turgay or West Siberian Sea) during the Mid-Late Cretaceous, then diversified into the advanced Parasaurolophini and Corythosaurini before following the same routes back to Asia sometime during the later Cretaceous.
Based on a veritable hotch potch of remains from various localities across southern Kazakhstan, Anatoly Nikolaenvich Riabinin named Jaxartosaurus aralensis in 1939. The limb bones which were assigned here appear to offer nothing to its diagnosis, not that it matters, because they've been lost anyway, but the skull is choc-a-bloc with unique features and non-pronounceable words that we won't bore you with. Suffice to say, it was wide and low with distinct sutures between the bones which suggests it was a juvenile. It's a bit difficult to evaluate the shape of its crest because the crest itself was not preserved. However, the shape and size of the bones to which a crest would have been attached are similar to those of the helmet-crested Corythosaurus from Alberta, so Jaxartosaurus probably sported a helmet crest too, but somewhat thicker.
Juveniles of most specimens often find themselves sunk into other genera somewhere down the line, but Jaxartosaurus bucked this trend by taking on remains that were previously known as Tanius prynadai and Bactrosaurus prynadai that Riabinin managed to name in 1939 based on the exact same remains, and parts of Procheneosaurus convincens (a fairly complete skeleton that spent a short time as Corythosaurus convincens). Unsuprisingly, not all experts agree, and Procheneosaurus convincens may be worthy of its own generic name.
Because the likes of Jaxartosaurus and Aralosaurus of Kazakhstan, Tsintaosaurus of eastern China, and Amurosaurus of eastern Russia are the most basal and/or oldest lambeosaurine and saurolophine hadrosaurids, some experts reckon that the hadrosaur ancestor arose in Asia. Its descendants may have migrated into Western North America over a land bridge called the Beringian Isthmus and into Europe via a temporary opening of the Turgai Strait (aka the Turgay or West Siberian Sea) during the Mid-Late Cretaceous, then diversified into the advanced Parasaurolophini and Corythosaurini before following the same routes back to Asia sometime during the later Cretaceous.
Etymology
Jaxartosaurus is derived from "Jaxartes" (an ancient name for the Syr Darya River, close to where the fossils were found) and the Greek "sauros" (lizard).The species epithet, aralensis, combines "Aral" (for Kazakhstan's Aral Mountains) with the Latin "ensis" (from).
Discovery
The first fossils of Jaxartosaurus were discovered at Kyrk-Kuduk (aka Station Sary-Agach, Chingeldy) in the Dabrazhin Formation (Dabrazinskaya Svita) near the Alym-Tau range, Ongtustik (southern) Qazaqstan (Kazakhstan) Oblysy/Oblast (Province), Kazakhstan. The holotype, PEN AN SSR 1/5009, is the first of two partial skulls, housed at The Museum of the Central Science and Research Institute for Geological Exploration, at Leningrad.
