Muttaburrasaurus

File:Muttaburrasaurus skull.jpg skull]]

The species was initially described from a partial skeleton found by grazier Doug Langdon in 1963 at Rosebery Downs Station beside Thomson River near Muttaburra, in the Australian state of Queensland, which also provides the creature's generic name. The remains were collected by paleontologist Dr Alan Bartholomai and entomologist Edward Dahms. After a lengthy preparation of the fossils, it was named in 1981 by Bartholomai and Ralph Molnar, who honoured its discoverer with its specific name, langdoni.{{cite journal |last1=Bartholomai |first1=Alan |author-link1=Alan Bartholomai |last2=Molnar |first2=R.E. |author-link2=Ralph Molnar |name-list-style=and |year=1981 |title=Muttaburrasaurus: a new Iguanodontid (Ornithischia:Ornithopoda) dinosaur from the Lower Cretaceous of Queensland |url=https://www.biodiversitylibrary.org/item/188348#page/93/mode/1up |journal=Memoirs of the Queensland Museum |volume=20 |issue=2 |pages=319–349}}

The holotype, specimen QM F6140, was found in the Mackunda Formation dating to the Albian-Cenomanian. It consists of a partial skeleton with skull and lower jaws. The underside of the skull and the back of the mandibula, numerous vertebrae, parts of the pelvis, and parts of the front and hind limbs have been preserved.

Some teeth have been discovered further north, near Hughenden,{{cite journal |last=Molnar |first=Ralph E. |author-link=Ralph Molnar |year=1996 |title=Observations on the Australian ornithopod dinosaur, Muttaburrasaurus". |url=https://www.biodiversitylibrary.org/item/123909#page/151/mode/1up |journal=Memoirs of the Queensland Museum |volume=39 |issue=3 |pages=639–652}} and south at Lightning Ridge, in northwestern New South Wales. At Lightning Ridge, there have been found opalised teeth and a scapula that may be from a Muttaburrasaurus. 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 and Richmond in 1987. It originates from somewhat older layers of the Allaru Mudstone and was considered by Molnar to be a separate, yet unnamed species, a Muttaburrasaurus sp. The same area produced two fragmentary skeletons in 1989. There have also been isolated teeth and bones found at Iona Station, southeast of Hughenden.

Reconstructed skeleton casts of Muttaburrasaurus, sponsored by Kellogg Company, have been put on display at a number of museums, including the Queensland Museum, Flinders Discovery Centre, and National Dinosaur Museum in Australia.

File:Muttaburrasaurus Scale.svg

Muttaburrasaurus was about {{convert|8|m}} and weighed around {{convert|2.8|MT|ST}}.{{cite book |last=Paul |first=G.S. |author-link=Gregory S. Paul |title=The Princeton Field Guide to Dinosaurs |publisher=Princeton University Press |year=2010 |page=286}} The femur of the holotype has a length of {{convert|1015|mm}}.

Image:Muttaburrasaurus NT.jpg]]

Whether Muttaburrasaurus 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 reconstructing Muttaburrasaurus with a thumb spike, Molnar later doubted such a structure was present. The foot was long and broad, with four toes.

The skull of Muttaburrasaurus 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-called bulla nasalis was shorter in the older Muttaburrasaurus sp., as is shown by the Dunluce Skull. The top section of the bulla of the holotype has not been preserved, but at least the second skull has a rounded profile.

File:Muttaburrasaurus langdoni TMAG 20171118-036.jpg

Molnar originally assigned Muttaburrasaurus to the Iguanodontidae. Later authors suggested more basal euornithopod groups such as the Camptosauridae, Dryosauridae, or Hypsilophodontidae. Studies by Andrew McDonald indicate a position in the Rhabdodontidae.{{Cite journal |last=McDonald |first=Andrew T. |editor-last=Farke |editor-first=Andrew A. |title=Phylogeny of Basal Iguanodonts (Dinosauria: Ornithischia): An Update |doi=10.1371/journal.pone.0036745 |journal=PLOS ONE |volume=7 |issue=5 |pages=e36745 |year=2012 |pmid=22629328 |pmc=3358318 |bibcode=2012PLoSO...736745M |doi-access=free }} A 2022 phylogenetic analysis recovered Muttaburrasaurus and Tenontosaurus as basal rhabdodontomorphs and found them to likely represent sister taxa to Rhabdodontidae.{{cite journal |last=Poole |first=Karen E. |date=25 October 2022 |title=Phylogeny of iguanodontian dinosaurs and the evolution of quadrupedality |url=https://palaeo-electronica.org/content/2022/3707-iguanodontian-phylogeny |journal=Palaeontologia Electronica |volume=25 |issue=3 |doi=10.26879/702 |access-date=25 February 2023|doi-access=free }}

The following cladogram was recovered by Dieudonné and colleagues in 2016:{{Cite journal |last1=Dieudonné |first1=Paul-Emile |last2=Tortosa |first2=Thierry |last3=Torcida Fernández-Baldor |first3=Fidel |last4=Canudo |first4=José Ignacio |last5=Díaz-Martínez |first5=Ignacio |date=2016-06-22 |editor-last=Farke |editor-first=Andrew A. |title=An Unexpected Early Rhabdodontid from Europe (Lower Cretaceous of Salas de los Infantes, Burgos Province, Spain) and a Re-Examination of Basal Iguanodontian Relationships |journal=PLOS ONE |language=en |volume=11 |issue=6 |pages=e0156251 |doi=10.1371/journal.pone.0156251 |issn=1932-6203 |pmc=4917257 |pmid=27333279 |bibcode=2016PLoSO..1156251D |doi-access=free }}

{{clade| style=font-size:85%;line-height:85%

|label1=Iguanodontia

|1={{clade

|1={{clade

|1=Anabisetia

|2={{clade

|1=Tenontosaurus

|2=Dryomorpha }} }}

|label2=Rhabdodontomorpha

|2={{clade

|1=Muttaburrasaurus

|2={{clade

|1=Vegagete Ornithopod

|label2=Rhabdodontidae

|2={{clade

|1=Mochlodon

|2={{clade

|1=Rhabdodon

|2=Zalmoxes }} }} }} }} }} }}

However, in 2024, Fonseca and colleagues considered Muttaburrasaurus to be outside Rhabdodontomorpha and instead classified it as a member of the Gondwanan clade Elasmaria, alongside Fostoria dhimbangunmal.{{Cite journal |last1=Fonseca |first1=André O. |last2=Reid |first2=Iain J. |last3=Venner |first3=Alexander |last4=Duncan |first4=Ruairidh J. |last5=Garcia |first5=Mauricio S. |last6=Müller |first6=Rodrigo T. |date=December 2024 |title=A comprehensive phylogenetic analysis on early ornithischian evolution |journal=Journal of Systematic Palaeontology |volume=22 |issue=1 |at=2346577 |bibcode=2024JSPal..2246577F |doi=10.1080/14772019.2024.2346577}}

File:Hughenden-dinosaur-outback-queensland-australia.JPG, Australia]]

Muttaburrasaurus had very powerful jaws equipped with shearing teeth. Whereas in more derived ornithopod species, the replacement teeth alternated with the previous tooth generation to form a tooth battery, in Muttaburrasaurus, 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 an omnivorous diet, implying that Muttaburrasaurus occasionally ate carrion. In 1995, he changed his opinion, suspecting that Muttaburrasaurus{{'}}s dental system is evolutionarily convergent with the ceratopsian system of shearing teeth. They would have been an adaptation for eating tough vegetation such as cycads.{{cite conference |last=Molnar |first=R.E. |author-link=Ralph Molnar |year=1995 |editor1-last=Sun |editor1-first=A. |editor2-last=Wang |editor2-first=Y. |title=Possible convergence in the jaw mechanisms of ceratopians and Muttaburrasaurus |conference=Sixth Symposium on Mesozoic Terrestrial Ecosystems and Biota, short papers |location=Beijing |publisher=China Ocean Press |pages=115–117}}

{{Reflist}}

{{Commons category|Muttaburrasaurus}}

• {{cite journal |last=Cannon |first=Libby |year=2006 |title=The Muttaburra Lizard |journal=Australian Age of Dinosaurs |issue=4 |pages=16–31}}

{{Ornithopoda|O.}}

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{{Portal bar|Dinosaurs|Paleontology|Australia}}

Category:Elasmaria

Category:Dinosaur genera

Category:Albian dinosaurs

Category:Fossil taxa described in 1981

Category:Taxa named by Ralph Molnar

Category:Dinosaurs of Australia