| Australovenator | |
|---|---|
 | |
| Reconstructed skeleton, Australian Age of Dinosaurs Museum, Winton, Australia | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | Theropoda |
| Clade: | †Megaraptora |
| Family: | †Megaraptoridae |
| Genus: | †Australovenator Hocknullet al. 2009 |
| Species: | †A. wintonensis |
| Binomial name | |
| †Australovenator wintonensis Hocknullet al. 2009 | |
Australovenator (meaning "southern hunter") is agenus ofmegaraptorantheropoddinosaur fromCenomanian (Late Cretaceous)-ageWinton Formation (dated to 95 million years ago[1]) ofAustralia. Some specimens from theAlbian-agedEumeralla Formation as well as theWonthaggi Formation may belong toAustralovenator. It is known from partial cranial andpostcranial remains which were described in 2009 byScott Hocknull and colleagues, although additional descriptions and analyses continue to be published. It is the most complete predatory dinosaur discovered in Australia. It has been suggested thatAustralovenator is a sister taxon toFukuiraptor, although some phylogenetic analyses find it to be a more derived member of the Megaraptora, possibly being part of the main Megaraptoridae family itself.
Australovenator isbased on a theropod specimen (AODF 604), affectionately nicknamed "Banjo" afterBanjo Paterson, which was found intermingled with the remains of the sauropodDiamantinasaurus matildae at the "Matilda site" (AODL 85). The parts of theholotype as it was initially described, which are held at theAustralian Age of Dinosaurs Museum of Natural History, consists of a leftdentary, teeth, partial forelimbs and hindlimbs, a partial rightilium, ribs, andgastralia.Australovenator was described in2009 by paleontologistScott Hocknull of the Queensland Museum, and colleagues. Thetype species isA. wintonensis, in reference to nearbyWinton.[2] Although the holotype was first discovered in 2006 and first described in 2009,[2] the process of excavating the "Matilda site" is still ongoing and papers describing new elements of the holotype are still being published.Additional arm elements of the holotype were described in 2012,[3] more leg elements were described in 2013,[4] and a right dentary was described in 2015.[5]
For some time, Australovenator was considered to be within the same genus as another Australian Megaraptorid calledRapator.Rapator is based on a metacarpal first described byFriedrich von Huene during the early 1900s and for prior to the recognition of Megaraptora, it was considered to be either analvarezsaurid, or an intermediate theropod.[6] After the discovery of Australovenator, some scientists noted the similarity betweenRapator andAustralovenator. While Hocknullet al. (2009) identified a few distinguishing characters between the two taxa, based on a poorly preserved metacarpal I from the holotype ofAustralovenator.[2] Agnolinet al. (2010), reclassifiedRapator, instead finding it a megaraptoran, potentially sister taxon toAustralovenator. They mentioned thatMegaraptor, the only other taxon also preserving metacarpal I, was less similar toRapator thanAustralovenator. However, there were no clear differences between the two latter taxa.[7] The metacarpals of both taxa were redescribed in Whiteet al. (2014), who determined that they were not synonymous, adding multiple features two the potential characters identified by Hocknullet al. and Angolanet al.[1]
In 2019, material from theEumeralla Formation (Albian age) was referred tocf.Australovenator.[8] In 2020, a heavily eroded specimen was described, belonging to an indeterminate megaraptoran found near the type locality. The fossil material comprises "two fragmentary vertebrae, three partial metatarsals and the distal end of a pedal phalanx" as well as other indeterminate bone fragments. The animal was slightly larger than the holotype individual ofAustralovenator.[9]
According to Gregory S. Paul, it was estimated at 6 m (20 ft) long, with a body mass of 500 kilograms (1,100 lb).[10] A 2014 study estimated its body mass around 310 kilograms (680 lb).[11] Because it was a relatively lightweight predator, Hocknull coined it as the "cheetah of its time".[12] Like other megaraptorans,Australovenator would have been abipedalcarnivore.[13]
Aphylogenetic analysis foundAustralovenator to be an allosauroid carnosaurian, with similarities toFukuiraptor andcarcharodontosaurids. In the initial analysis, it was shown to be thesister taxon of theCarcharodontosauridae.[2] More detailed studies found that it formed a clade with several other carcharodontosaurid-like allosaurs, theNeovenatoridae.[14] Recent phylogenetic analysis suggestsAustralovenator is atyrannosauroid, like with all othermegaraptorans.[15] A phylogenetic analysis in 2016 focusing on the newneovenatoridGualicho found thatAustralovenator and other megaraptorids were either allosauroids or basal coelurosaurs as opposed to being tyrannosauroids.[16]
The ankles ofAustralovenator andFukuiraptor are similar tothe Australian talus bone known as NMVP 150070 that had previously been identified as belonging toAllosaurus sp., and this bone likely representsAustralovenator or a close relative of it.[2][17] Alternatively, this bone could belong to anabelisaur.[18]
Thecladogram below follows the 2010 analysis by Benson, Carrano and Brusatte.[14] Another study published later in 2010 also found the Australian theropodRapator to be a megaraptoran extremely similar toAustralovenator.[7]
| Neovenatoridae |
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The cladogram below follows the 2014 analysis by Porfiriet al. that finds megaraptorans to be tyrannosauroids.[19]
| Megaraptora |
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With very comprehensive and well-preserved hand and foot remains,Australovenator has been made a topic of various research papers studying the dynamics of theropod appendages.
A 2015 study tested the range of motion ofAustralovenator's arms using computer models and found that it had flexible arms, with the forearms capable of making an angle of 144 to 66 degrees with thehumerus, an elbow range of motion similar to that ofmaniraptoriforms. Unusually, itsradius could slide independently of theulna when its arm was flexed, similar to that of birds but unlike most non-avian dinosaurs. However, the study also found thatAustralovenator's fingers were capable ofextension far beyond those of any other sampled theropod, with onlyDilophosaurus having capabilities even near it. This study concluded thatAustralovenator's flexibility, facilitated by a combination of traits in both primitive and advanced theropods, played a role in prey capture, giving it the ability to grasp prey towards its chest to make it easier for its weak jaws to disembowel food.[20] The gracile morphology of the skull also concludes that this genus had a specialisation towards prey capture using its arms and hands.[21]
A 2016 study used CT scans of anemu foot to digitally reconstruct the musculature and soft tissue of anAustralovenator foot, as well as determine how soft tissue affects flexibility. The study determined that muscular range of motion is often overestimated when not accounting for soft tissue, and that soft tissue reconstruction is vital for making future analyses of theropod flexibility more accurate. A review of hindlimb elements described in 2013 re-identified several phalanges which were initially positioned incorrectly. In addition, it noted thatAustralovenator's phalanx II-3 was splayed, a pathology that may have resulted from the impacts of kicking motions. Some modern birds, such as thecassowary, are known to use their second toe as weapons in defensive or territorial fights.[22]
A 2017 followup to the 2016 study used a 3-D printed model of the reconstructed foot to make footprints in a matrix of clay and sand in an effort to understand the creation ofdinosaur footprints. The study specifically was designed to clarify the identity of particular controversial footprints fromLark Quarry, which may have been left from either a large theropod (likeAustralovenator) or an ornithopod (likeMuttaburrasaurus). The study found that the artificialAustralovenator footprints were similar to those at Lark Quarry, concluding that the trackways in question were likely those of a theropod. The writers of the study expressed interest in creating a reconstruction of aMuttaburrasaurus foot as an extension of the study, although noMuttaburrasaurus pedal material is known.[23]
AODL 604 was found about 60 kilometres (37 mi) northwest of Winton, nearElderslie Station. It was recovered from the lower part of theWinton Formation, dated to the late Cenomanian. AODL 604 was found in a clay layer betweensandstone layers, interpreted as anoxbow lake, orbillabong, deposit. Also found at the site were thetype specimen of thesauropodDiamantinasaurus,bivalves, fish, turtles,crocodilians, and plant fossils. The Winton Formation had a faunal assemblage including bivalves,gastropods,insects, thelungfishMetaceratodus, turtles, thecrocodilianIsisfordia,pterosaurs, and several types of dinosaurs, such as the sauropodsDiamantinasaurus andWintonotitan, and unnamedankylosaurians andhypsilophodonts. Plants known from the formation includeferns,ginkgoes,gymnosperms, andangiosperms.[2]
Three new dinosaurs discovered in Australia atWikinews
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