Aralosaurus

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Aralosaurus
Temporal range: Late Cretaceous, 83.6  Ma
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Aralosaurus skull.png
Skull of Aralosaurus. Known material white. This is the former reconstruction of Aralosaurus depicting incorrectly the animal as a Gryposaur-like Hadrosaurinae. [1]
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Ornithischia
Clade: Ornithopoda
Family: Hadrosauridae
Subfamily: Lambeosaurinae
Genus: Aralosaurus
Rozhdestvensky, 1968
Type species
Aralosaurus tuberiferus
Rozhdestvensky, 1968

Aralosaurus was a genus of hadrosaurid dinosaur that lived during the Late Cretaceous in what is now Kazakhstan. It is known only by a posterior half of a skull (devoid of its mandible) and some post-cranial bones [2] found in the Bostobe Formation in rocks dated from the Upper Santonian-Lower Campanian boundary, at about 83.6 Ma (millions of years). [3] Only one species is known, Aralosaurus tuberiferus, described by Anatoly Konstantinovich Rozhdestvensky in 1968. The genus name means Aral Sea lizard, because it was found to the northeast of the Aral Sea. [2] The specific epithet tuberiferus means bearing a tuber because the posterior part of the nasal bone rises sharply in front of the orbits like an outgrowth. [2] Aralosaurus was originally reconstituted with a nasal arch similar to that of North American Kritosaurus (a comparison based on a specimen now placed in the genus Gryposaurus ). [2] For many years, Aralosaurus was thus placed in the clade of the Hadrosaurinae. This classification was invalidated in 2004, following the re-examination of the skull of the animal which allowed to identify in Aralosaurus many typical characters of Lambeosaurinae. In particular, this study revealed that Aralosaurus had a hollow bony structure located far in front of the orbits, which communicated with the respiratory tract. [1] This structure being broken at its base, its shape and size remains undetermined. [1] More recently, Aralosaurus has been identified as the most basal Lambeosaurinae, and placed with its close relative Canardia from the upper Maastrichtian of France in the new clade of Aralosaurini. [3]

Contents

Discovery

Aralosaurus hypothetical head Aralosaurus LM.png
Aralosaurus hypothetical head

The partial skull of Aralosaurus was discovered in 1957 near the Shakh-Shakh locality during a Soviet expedition in central Kazakhstan (which at the time was part of the USSR). In addition to the skull (which lacks most of the snout and the entire mandible), the material also included isolated teeth and postcranial elements most often fragmentary (ulna, radius, femur, tibia, fibula, astragalus, metatarsals). The only complete elements were a humerus and a metatarsal. It is only in 1968 that Rozhdestvensky described and named the animal. He estimated the size of the skull at about 65 cm and the size of the animal at about 6.5 m long. As the cranial sutures are far from fusioned, this specimen was probably immature. At the time, Rozhdestvensky argued that the skull of Aralosaurus presented the greatest resemblance with the skull of Kritosaurus with the presence of a nasal arch in front of the orbits (the comparisons were based with specimens attributed today to Gryposaurus , not to Kritosaurus). So, the animal was classified among the Hadrosaurinae, which are hadrosaurs devoid of cranial crest or with a solid bony crest. [2]

In 2004, the skull of Aralosaurus was re-examined by Godefroit and colleagues, and according to them, the bone fragments identified by Rozhdestvensky as the middle part of the nasal arch and the posterior portion of the premaxilla seem to have been lost. These fragments were originally found isolated while the rest of the skull was articulated (including a posterior fragment of the nasal). So that it is no longer possible today to confirm the presence of a nasal arch in Aralosaurus. On the other hand, this study shows that Aralosaurus was not a gryposaur-like hadrosaurine, because the purported nasal boss was in fact a fragment of a hollow structure. Indeed, Godefroit and colleagues did not find any hadrosaurine diagnostic characters in Aralosaurus. On the contrary, the skull of Aralosaurus presents several features (in the maxilla, parietal, squamosal and especially the nasal) which indicates its inclusion among the Lambeosaurinae. Notably, the posterior fragment of the nasal, which is clearly articulated to the rest of the skull, rises just in front of the orbits and forming or participating to a hollow crest-like structure. As this structure is broken at its base, it is not possible to deduce its size and shape. However, in rostral view, the nasal is clearly hollow, it is deeply excavated rostrally by a broad groove that communicates directly with the ventral side of the posterior part of the bone. It is therefore clear that in Aralosaurus the nasal crest surrounded part of the respiratory system. The extension of the nasal cavity inside a hollow crest is typically a lambeosaurine feature, thus confirming the inclusion of Aralosaurus among them. [1] Aralosaurus also exhibits several cranial characters which indicate that it was a basal member of the group. Although having a hollow nasal structure, the latter was located in front of the orbits, a primitive position in lambeosaurines. In the most advanced representatives of the group, the nasal migrates to a caudodorsal position because of the important development of the premaxillae in these forms. In addition, in more derived lambeosaurines, the skull roof is modified to form a fixation zone for the hollow crest, whereas in Aralosaurus the skull roof does not present any particular modification. The shape and the size of the crest-like structure of Aralosaurus is unknown. The fragments that were previously interpreted as a part of a gryposaur-like nasal arch and could have helped to reconstruct the circumnarial region of Aralosaurus, have been lost. [1] So, the discovery of more complete specimens is necessary for a better knowledge of the shape and the size of this hollow structure.

Classification

Life restoration Life reconstruction of Aralosaurus tuberiferus.png
Life restoration

The following cladogram was produced by Albert Prieto-Márquez and his colleagues in 2013, it shows the phylogeny of Lambeosaurinae. Aralosaurus is closely related to Canardia and both genera are included in the tribe of Aralosaurini, which are identified as the most basal members of Lambeosaurinae.

  Lambeosaurinae  
Aralosaurini

Aralosaurus

Canardia

Jaxartosaurus

Tsintaosaurini

Tsintaosaurus

Pararhabdodon

Parasaurolophini

Charonosaurus

Parasaurolophus

Parasaurolophus cyrtocristatus

Parasaurolophus tubicen

Parasaurolophus walkeri

Lambeosaurini
Lambeosaurus

Lambeosaurus lambei

Lambeosaurus magnicristatus

Corythosaurus

Corythosaurus casuarius

Corythosaurus intermedius

"Hypacrosaurus" stebingeri

Hypacrosaurus

Olorotitan

Arenysaurus

Blasisaurus

Magnapaulia

Velafrons

Amurosaurus

Sahaliyania

Paleobiogeography

Aralosaurus lived about 20 million years before its close relative Canardia. The latter inhabited the Ibero-Armorican Island, which was the westernmost island of the Late Cretaceous European Archipelago. [4] As no lambeosaurines were known in the rich localities of late Campanian and early Maastrichtian ages of the Ibero-Armorican Island, it was suggested that the descendants of Aralosaurus had to reach this island rather late, perhaps at the end of the early Maastrichtian or during the late Maastrichtian. [3] The discovery later in Spain of numerous lambeosaurines remains in the highest levels of the lower Maastrichtian argues for the first hypothesis. [5] [6] This migration was probably carried out in several stages, firstly by temporary terrestrial links between the landmass of Western Asia and the eastern islands of the European archipelago, then between the different European islands up to the Ibero-Armorican Island. [4] Canardia was a rather archaic form for its time and the Ibero-Armorican Island was perhaps an ultimate refuge for the Aralosaurini. [3]

Paleoecology

The sediments of the Bostobe Formation consist mainly of clays and sandstones, and correspond to floodplain and estuarine environments in a subtropical to tropical climate. [7] These different biotopes were located on the west coast of the Asian continent of the time, on the edge of the ancient Turgai Sea which connected the Tethys to the Arctic Ocean. [7] The shallow marine waters west of this fluvial coastal plain were the site of intense organic productivity due to upwelling conditions caused by strong winds from the mainland. [7] These winds were also the cause of a significant aridification of the climate in this region during the Santonian and early Campanian, causing a change in the flora of angiosperms, with a rarefaction of broad-leaved forms and a proliferation of small and narrow-leaved species of the family Ulmaceae. Angiosperms accounted for 75% of the flora of these biotopes, the rest being conifers and rare ginkgos and cycads. [7]

The locality of Shakh Shakh, where Aralosaurus was found, yielded a diverse fauna including many fish (chondrichthyans, chondrosteans, and holosteans), [7] Anura, [7] at least six species of turtles [7] some of which had a carapace at least 75 cm long, [8] a scincomorph, [7] crocodylians, [7] pterosaurs ( Aralazhdarcho ), [9] birds, [7] mammals, [7] and several undetermined dinosaur species (Ankylosauridae, Sauropoda, Tyrannosauroidea, Ornithomimidae, Therizinosauroidea, Troodontidae, and Dromaeosauridae). [10] [11] [12] [7] Elsewhere in this formation, the site of Akkurgan is distinguished by the presence of the two basal hadrosauroids Arstanosaurus [13] and Batyrosaurus , [14] as well as the pterosaur Samrukia (whose jaw was first attributed to an Caenagnathid oviraptorosaur, then to a giant bird), [15] [16] which could be a junior synonym of Aralazhdarcho. [7]

See also

Related Research Articles

<i>Lambeosaurus</i> Hadrosaurid dinosaur genus from Late Cretaceous US and Canada

Lambeosaurus is a genus of hadrosaurid dinosaur that lived about 75 million years ago, in the Late Cretaceous period of North America. This bipedal/quadrupedal, herbivorous dinosaur is known for its distinctive hollow cranial crest, which in the best-known species resembled a mitten. Several possible species have been named, from Canada, the United States, and Mexico, but only the two Canadian species are currently recognized as valid.

<i>Saurolophus</i> Hadrosaurid dinosaur genus from the Late Cretaceous period

Saurolophus is a genus of large hadrosaurid dinosaur from the Late Cretaceous period of Asia and North America, that lived in what is now the Horseshoe Canyon and Nemegt formations about 70 million to 68 million years ago. It is one of the few genera of dinosaurs known from multiple continents. The type species, S. osborni, was described by Barnum Brown in 1912 from Canadian fossils. A second valid species, S. angustirostris, is represented by numerous specimens from Mongolia, and was described by Anatoly Konstantinovich Rozhdestvensky.

<i>Olorotitan</i> Extinct genus of dinosaurs

Olorotitan was a genus of lambeosaurine duckbilled dinosaur from the middle or latest Maastrichtian-age Late Cretaceous, whose remains were found in the Udurchukan Formation beds of Kundur, Amur River Region, Far Eastern Russia. The type, and only species is Olorotitan arharensis. It was one of the last non-avian dinosaurs and it went extinct during the Cretaceous–Paleogene extinction event.

<i>Amurosaurus</i> Extinct genus of dinosaurs

Amurosaurus is a genus of lambeosaurine hadrosaurid dinosaur found in the latest Cretaceous period of eastern Asia. Fossil bones of adults are rare, but an adult would most likely have been at least 6 metres (20 ft) long. According to Gregory S. Paul, it was about 8 metres (26 ft) long and weighed about 3,000 kilograms (6,600 lb).

<i>Barsboldia</i> Extinct genus of dinosaurs

Barsboldia is a genus of large hadrosaurid dinosaur from the early Maastrichtian Nemegt Formation of Ömnogöv', Mongolia. It is known from a partial vertebral column, partial pelvis, and some ribs.

<i>Tsintaosaurus</i> Hadrosaurid ornithopod dinosaur from Late Cretaceous period

Tsintaosaurus is a genus of hadrosaurid dinosaur from China. It was about 8.3 metres (27 ft) long and weighed 2.5 tonnes. The type species is Tsintaosaurus spinorhinus, first described by Chinese paleontologist C. C. Young in 1958.

<i>Pararhabdodon</i> Extinct genus of dinosaurs

Pararhabdodon is a genus of tsintaosaurin hadrosaurid dinosaur, from the Maastrichtian-age Upper Cretaceous Tremp Group of Spain. The first remains were discovered from the Sant Romà d’Abella fossil locality and assigned to the genus Rhabdodon, and later named as the distinct species Pararhabdodon isonensis in 1993. Known material includes assorted postcranial remains, mostly vertebrae, as well as maxillae from the skull. Specimens from other sites, including remains from France, a maxilla previously considered the distinct taxon Koutalisaurus kohlerorum, an additional maxilla from another locality, the material assigned to the genera Blasisaurus and Arenysaurus, and the extensive Basturs Poble bonebed have been considered at different times to belong to the species, but all of these assignments have more recently been questioned. It was one of the last non-avian dinosaurs known from the fossil record that went extinct during the Cretaceous-Paleogene extinction event.

<i>Charonosaurus</i> Extinct genus of dinosaurs

Charonosaurus is a genus of dinosaur whose fossils were discovered by Godefroit, Zan & Jin in 2000 on the south bank of the Amur River, dividing China from Russia. It is monotypic, consisting of the species C. jiayinensis.

<i>Nipponosaurus</i> Hadrosaurid dinosaur genus from Late Cretaceous Japan

Nipponosaurus is a lambeosaurine hadrosaur from sediments of the Yezo Group, in Sinegorsk on the island of Sakhalin, which was part of Japan at the time of the species' classification. The type and only species is N. sachalinensis, known only from a single juvenile specimen discovered in 1934 and named in 1936, by Takumi Nagao, with further material of the same individual found in 1937. Since then, the taxon has been largely ignored, and its validity has been doubted, with synonymy with other Asian hadrosaurs or status as a nomen dubium being suggested. Redescriptions from 2004 and 2017, however, have supported recognition as a distinct species. Dating the only specimen has been difficult, but based on associated mollusc taxa, the species likely lived sometime in the upper Santonian or lower Campanian, around 80 million years ago.

<span class="mw-page-title-main">Lambeosaurini</span> Extinct tribe of dinosaurs

Lambeosaurini, previously known as Corythosaurini, is one of four tribes of hadrosaurid ornithopods from the family Lambeosaurinae. It is defined as all lambeosaurines closer to Lambeosaurus lambei than to Parasaurolophus walkeri, Tsintaosaurus spinorhinus, or Aralosaurus tuberiferus, which define the other three tribes. Members of this tribe possess a distinctive protruding cranial crest. Lambeosaurins walked the earth for a period of around 12 million years in the Late Cretaceous, though they were confined to regions of modern-day North America and Asia.

<i>Koutalisaurus</i> Extinct genus of dinosaurs

Koutalisaurus is a potentially dubious genus of extinct hadrosaurid dinosaur from the Arenysaurini. It is based on a mostly complete dentary from the Maastrichtian-age Upper Cretaceous Tremp Formation near the town of Abella de la Conca, Lleida, Spain.

The Bostobe Formation is a geological formation in Qaraghandy & Qyzylorda, Kazakhastan whose strata date back to the Late Cretaceous.

The Marnes d’Auzas Formation is a geological Formation in southwestern France whose strata date back to the Late Maastrichtian. It is about 100 metres thick and consists primarily of marls with some interbeds of sandstones. It corresponds to sediments whose depositional environment evolved from the paralic domain at the base of the formation, towards a more continental domain in its upper part. The Marnes d’Auzas Formation was deposited in the west coast of the former Ibero-Armorican Island, which included much of France and Spain.

<i>Kazaklambia</i> Extinct genus of dinosaurs

Kazaklambia is an extinct genus of herbivorous lambeosaurine dinosaur known from the Late Cretaceous Dabrazinskaya Svita of southern Kazakhstan. It contains a single species, Kazaklambia convincens.

<i>Canardia</i> Extinct genus of dinosaurs

Canardia is an extinct genus of lambeosaurine dinosaur known from the Late Cretaceous Marnes d'Auzas Formation of Haute-Garonne department, in Occitanie region, southwestern France. The type species Canardia garonnensis was first described and named by Albert Prieto-Márquez, Fabio M. Dalla Vecchia, Rodrigo Gaete and Àngel Galobart in 2013. It is only known from juvenile specimens. The name of the genus comes from “canard”, the French word for “duck”, an allusion to the fact that this animal belongs to the hadrosaurids which are also known as duck-billed dinosaurs. The specific epithet garonnensis refers to the Haute-Garonne department where this dinosaur has been found. Although universally recognized as a lambeosaurine, its precise position within them is debated. Some authors consider it as a close relative of the genus Aralosaurus from Central Asia with which it would form the tribe Aralosaurini, while others include it in a more derived clade, the Arenysaurini in which all lambeosaurines from Europe and North Africa are placed. Canardia was one of the last non-avian dinosaurs and lived between 67,5 and 66 my on the former Ibero-Armorican Island, which included much of France and Spain.

<span class="mw-page-title-main">Aralosaurini</span>

Aralosaurini is a proposed tribe of hadrosaurid dinosaurs belonging to the subfamily Lambeosaurinae. The members of this group lived in Asia and Europe during the end of the Late Cretaceous about 83.6 to 66.0 million years ago. The clade may not be monophyletic, with Canardia and Aralosaurus potentially instead being unrelated primitive members of the subfamily.

<span class="mw-page-title-main">Tsintaosaurini</span> Extinct tribe of dinosaurs

Tsintaosaurini is a tribe of basal lambeosaurine hadrosaurs native to Eurasia. It is thought to contains the genera Tsintaosaurus, Pararhabdodon and Koutalisaurus, though some studies have questioned its existence as a natural grouping.

<span class="mw-page-title-main">Timeline of hadrosaur research</span>

This timeline of hadrosaur research is a chronological listing of events in the history of paleontology focused on the hadrosauroids, a group of herbivorous ornithopod dinosaurs popularly known as the duck-billed dinosaurs. Scientific research on hadrosaurs began in the 1850s, when Joseph Leidy described the genera Thespesius and Trachodon based on scrappy fossils discovered in the western United States. Just two years later he published a description of the much better-preserved remains of an animal from New Jersey that he named Hadrosaurus.

<i>Adynomosaurus</i> Extinct genus of dinosaurs

Adynomosaurus is a genus of lambeosaurine dinosaur from the Late Cretaceous of what is now Catalonia, Spain. First discovered in 2012, it was named in 2019 with the type and only species Adynomosaurus arcanus, as an addition to the very incomplete fossil record of hadrosaurides dinosaurs from the Late Cretaceous of Europe. It is only known from scant material, but is distinguished from other hadrosaurs by its weakly developed shoulder blade which would have had underdeveloped musculature, which lends it its scientific name, partially from the Greek word for "weak". Its exact relationships with other hadrosaurs remain unresolved, with it not consistently being recovered as a relative of any other specific genera, though some studies have allied it with Tsintaosaurini or even found it outside of Hadrosauridae. It would have lived as part of a diverse coastal estuaryweak ecosystem, made up of meandering rivers and mud flats, and fits into a picture of major ecological turnover in the Maastrichtian age of Europe.

<span class="mw-page-title-main">Arenysaurini</span> Extinct tribe of dinosaurs

Arenysaurini is a proposed tribe of primitive lambeosaurine hadrosaurs. It is composed of genera found in Europe and North Africa during the end of the Cretaceous period, and has been suggested to unite all lambeosaurs from the former continent into a singular monophyletic group.

References

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