| Muttaburrasaurus | |
|---|---|
 | |
| Mounted skeleton | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | †Ornithischia |
| Clade: | †Ornithopoda |
| Clade: | †Iguanodontia |
| Genus: | †Muttaburrasaurus Bartholomai &Molnar,1981 |
| Species: | †M. langdoni |
| Binomial name | |
| †Muttaburrasaurus langdoni Bartholomai & Molnar, 1981 | |
Muttaburrasaurus was agenus ofherbivorousiguanodontianornithopoddinosaur that lived in what is now north-easternAustralia sometime between 112 and 103million years ago[1] during the earlyCretaceousperiod. It has been recovered in some analyses as a member of the iguanodontian cladeRhabdodontomorpha, or alternately as a member ofElasmaria.[2] AfterKunbarrasaurus, it is Australia's most completely known dinosaur from skeletal remains. It was named afterMuttaburra, the site inQueensland, Australia, where it was found. The dinosaur was selected from twelve candidates to become theofficial fossil emblem of the State of Queensland.[3][4]
The species was initially described from a partial skeleton found by grazier Doug Langdon in 1963 at Rosebery Downs Station besideThomson River nearMuttaburra, in the Australianstate ofQueensland, which also provides the creature's generic name. The remains were collected bypaleontologist DrAlan Bartholomai andentomologist Edward Dahms. After a lengthy preparation of the fossils, it was named in 1981 by Bartholomai andRalph Molnar, who honoured its discoverer with itsspecific name,langdoni.[5]
Theholotype, specimen QM F6140, was found in theMackunda Formation dating to theAlbian–Cenomanian. It consists of a partial skeleton with skull and lower jaws. The underside of the skull and the back of themandibula, numerous vertebrae, parts of the pelvis, and parts of the front and hind limbs have been preserved.
Some teeth have been discovered further north, nearHughenden,[6] and south atLightning Ridge,[6] in north-westernNew South Wales. At Lightning Ridge, there have been foundopalised teeth and ascapula that may be from aMuttaburrasaurus. A skull, known as the "Dunluce Skull", specimen QM F14921, was discovered by John Stewart-Moore and 14-year-old Robert Walker on Dunluce Station, between Hughenden andRichmond in 1987. It originates from somewhat older layers of theAllaruMudstone and was considered by Molnar to be a separate, yet unnamed species, aMuttaburrasaurus sp.[6] The same area produced two fragmentary skeletons in 1989. There have also been isolated teeth and bones found at Iona Station, south-east of Hughenden.
Reconstructed skeleton casts ofMuttaburrasaurus, sponsored byKellogg Company, have been put on display at a number of museums, including theQueensland Museum,Flinders Discovery Centre, andNational Dinosaur Museum in Australia.
Muttaburrasaurus was about 8 metres (26 ft) and weighed around 2.8 metric tons (3.1 short tons).[7] Thefemur of the holotype has a length of 1,015 millimetres (40.0 in).
WhetherMuttaburrasaurus is capable of quadrupedal movement has been debated; it was originally thought to be an "iguanodontid", though recent studies indicate a rhabdodont position. Ornithopods this basal were incapable of quadrupedal movement. Originally reconstructingMuttaburrasaurus with a thumb spike, Molnar later doubted such a structure was present.[6] The foot was long and broad, with four toes.
The skull ofMuttaburrasaurus was rather flat, with a triangular cross-section when seen from above; the back of the head is broad but the snout pointed. The snout includes a strongly enlarged, hollow, upward-bulging nasal muzzle that might have been used to produce distinctive calls or for display purposes. However, as no fossilised nasal tissue has been found, this remains conjectural. This so-calledbulla nasalis was shorter in the olderMuttaburrasaurus sp., as is shown by the Dunluce Skull. The top section of thebulla of the holotype has not been preserved, but at least the second skull has a rounded profile.[6]
Molnar originally assignedMuttaburrasaurus to theIguanodontidae. Later authors suggested morebasal euornithopod groups such as theCamptosauridae,Dryosauridae, orHypsilophodontidae. Studies by Andrew McDonald indicate a position in theRhabdodontidae.[2][8] A 2022 phylogenetic analysis recoveredMuttaburrasaurus andTenontosaurus as basal rhabdodontomorphs and found them to likely represent sister taxa to Rhabdodontidae.[9]
The following cladogram was recovered by Dieudonné and colleagues in 2016:[10]
| Iguanodontia |
| ||||||||||||||||||
However, in 2024, Fonseca and colleagues consideredMuttaburrasaurus to be outside Rhabdodontomorpha and instead classified it as a member of the Gondwanan cladeElasmaria, alongsideFostoria dhimbangunmal.[11]
Muttaburrasaurus had very powerful jaws equipped with shearingteeth. Whereas in more derivedornithopod species, the replacement teeth alternated with the previous tooth generation to form a tooth battery, inMuttaburrasaurus, they grew directly under them, and only a single erupted generation was present, thus precluding a chewing motion. An additional basal trait was the lack of a primary ridge on the teeth sides, which show eleven lower ridges. In 1981, Molnar speculated that these qualities indicated anomnivorous diet, implying thatMuttaburrasaurus occasionally ate carrion. In 1995, he changed his opinion, suspecting thatMuttaburrasaurus's dental system is evolutionarily convergent with theceratopsian system of shearing teeth. They would have been an adaptation for eating tough vegetation such ascycads.[12]
