Minmi paravertebra

Minmi is a genus of small herbivorous ankylosaurian dinosaur that lived during the early Cretaceous Period of Australia, about 119 to 113 million years ago.

Minmi
Temporal range: Early Cretaceous
~119–113 Ma
Minmi paravertebra dinosauria
Hypothetical restoration, mainly based on Kunbarrasaurus
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Ornithischia
Clade: Eurypoda
Suborder: Ankylosauria
Genus: Minmi
Molnar 1980
Species:
M. paravertebra
Binomial name
Minmi paravertebra
Molnar 1980

Discovery and species

Australian thyreophoran localities
Australian thyreophoran localities: 2 denotes where the holotype was found

In 1964, Dr Alan Bartholomai, a collaborator of the Queensland Museum, discovered a chalkstone nodule containing an ankylosaurian skeleton in Queensland near Minmi Crossing, along the Injun Road, one kilometre south of Mack Gulley, north of Roma.[1]

In 1980, Ralph E. Molnar named and described the type species, in this case the only species known in the genus, Minmi paravertebra. The generic name, at the time the shortest of a Mesozoic dinosaur, refers to Minmi Crossing. The meaning of "minmi" itself is uncertain; it refers to a large lily in the local aboriginal language but might also be derived from min min, a kind of will-o'-the-wisp. The specific name refers to strange bone elements found along the vertebrae, for which Molnar coined the designation paravertebrae.[1]

The holotype, QM F10329, was discovered in a layer of the Bungil Formation, the Minmi Member, a lagoon deposit which was first dated to the Barremian-Valanginian, but later was recalibrated to the Aptian. It consists of a partial skeleton, lacking the skull. It preserves a series of eleven back vertebrae, ribs, a right hindlimb, and plates of the belly armour.[1] It was the first specimen of a member of the Thyreophora discovered in the Southern Hemisphere.

In 1989, a much more complete skeleton was discovered, specimen QM F1801 that includes the skull and shows an articulated body armour. It was referred to a Minmi sp. Since 1989, most information provided on Minmi in books and illustrations is based on this second exemplar, but in 2015, it was named as a separate genus, Kunbarrasaurus.[2]

Between 1989 and 1996 several other specimens were discovered and ultimately referred to a Minmi sp. These include QM F33286: a rump with pelvis and osteoderms; AM F35259: ribs with osteoderms; QM F33565: a partial thighbone; and QM F33566: a partial shinbone, perhaps of the same individual as QM F33565. AM F35259 is part of the collection of the Australian Museum.[3] Later specimen QM F119849 was reported, consisting of ribs and osteoderms.[4]

Description

Minmi was a small herbivorous quadrupedal armoured ankylosaurian. In 2016, Gregory S. Paul estimated its length at 3 metres (9.8 ft), its weight at 300 kilograms (660 lb).[5] For an ankylosaurian, Minmi had long limbs, perhaps used to quickly search cover under brushes when threatened by large predators which might have been able to flip the small animal on its back.[6]

Unlike other ankylosaurians, Minmi had horizontally oriented plates of bones that ran along the sides of its vertebrae, hence its specific name, paravertebra. Molnar in 1980 acknowledged that these were ossified tendons, but denied that they were homologous to the ossified tendons of other Ornithischia and claimed that they resembled the pathological tendon aponeurosis of modern crocodiles. Victoria Megan Arbour in 2014 deemed this unlikely and could find only one autapomorphy in the holotype:[7] the high vertical extent of the musculus articulospinalis tendon ossification at its outer front end, wrapping itself around the side process of the vertebra. In 2015, Arbour and Philip Currie concluded that even this was not unique, which would mean the holotype had no diagnostic features and Minmi would be a nomen dubium.[8] However, the 2015 description of Kunbarrasaurus announced that new distinguishing traits of Minmi had been discovered and that it should be considered a valid taxon.[2]

Phylogeny

In 1980, Molnar placed Minmi in the Ankylosauria.[1] In 1987, he thought it was a member of the Nodosauridae.[9] In 2011, a new cladistic analysis performed by Thompson et al. recovered Minmi as the basalmost known ankylosaurid.[10] Arbour & Currie entered Minmi and Minmi sp. as separate operational taxonomic units in their analysis and recovered Minmi as the basalmost ankylosaurid but Minmi sp. (= Kunbarrasaurus) as a more basal ankylosaurian, too "primitive" to be included in either the Ankylosauridae or Nodosauridae.[8] Paul in 2010 suggested that both taxa were part of a Minmidae, an ancient and very basal ankylosaurian lineage, also including Antarctopelta, that had become isolated on Gondwana.[6]

See also

References

  1. ^ a b c d Molnar, R.E. (1980). "An ankylosaur (Ornithischia: Reptilia) from the Lower Cretaceous of southern Queensland". Memoirs of the Queensland Museum. 20: 65–75.
  2. ^ a b Lucy G. Leahey; Ralph E. Molnar; Kenneth Carpenter; Lawrence M. Witmer; Steven W. Salisbury (2015). "Cranial osteology of the ankylosaurian dinosaur formerly known as Minmi sp. (Ornithischia: Thyreophora) from the Lower Cretaceous Allaru Mudstone of Richmond, Queensland, Australia". PeerJ. 3: e1475. doi:10.7717/peerj.1475. PMC 4675105. PMID 26664806.
  3. ^ Molnar, R.E. (1996). "Preliminary report on a new ankylosaur from the Early Cretaceous of Queensland, Australia". Memoirs of the Queensland Museum. 39 (3): 653–668.
  4. ^ Leahey, L.G.; Salisbury, S.W. (2013). "First evidence of ankylosaurian dinosaurs (Ornithischia: Thyreophora) from the mid-Cretaceous (late Albian-Cenomanian) Winton Formation of Queensland, Australia". Alcheringa. 37 (2): 249–257. doi:10.1080/03115518.2013.743703.
  5. ^ Paul, Gregory S. (2016). The Princeton Field Guide to Dinosaurs. Princeton University Press. p. 258. ISBN 978-0691167664.
  6. ^ a b Paul, Gregory S. (2010). The Princeton Field Guide to Dinosaurs. Princeton University Press. p. 227. ISBN 978-0691137209.
  7. ^ Arbour, Victoria Megan, 2014, Systematics, evolution, and biogeography of the ankylosaurid dinosaurs Ph.D thesis, University of Alberta
  8. ^ a b Arbour, Victoria M.; Currie, Philip J. (2015). "Systematics, phylogeny and palaeobiogeography of the ankylosaurid dinosaurs". Journal of Systematic Palaeontology. 14 (5): 1. doi:10.1080/14772019.2015.1059985.
  9. ^ Molnar, R.E.; Frey, E. (1987). "The paravertebral elements of the Australian ankylosaur Minmi (Reptilia: Ornithischia, Cretaceous)". Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen. 175: 19–37.
  10. ^ Richard S. Thompson; Jolyon C. Parish; Susannah C. R. Maidment; Paul M. Barrett (2011). "Phylogeny of the ankylosaurian dinosaurs (Ornithischia: Thyreophora)". Journal of Systematic Palaeontology. in press (2): 301. doi:10.1080/14772019.2011.569091.

Further reading

External links

Ankylosauridae

Ankylosauridae () is a family of armored dinosaurs within Ankylosauria, and is the sister group to Nodosauridae. Ankylosaurids appeared 122 million years ago and went extinct 66 million years ago during the Cretaceous–Paleogene extinction event. These animals were mainly herbivorous and were obligate quadrupeds, with leaf-shaped teeth and robust, scute-covered bodies. Ankylosaurids possess a distinctly domed and short snout, wedge-shaped osteoderms on their skull, scutes along their torso, and a tail club.Ankylosauridae is exclusively known from the northern hemisphere, with specimens found in western North America, Europe, and East Asia. The first discoveries within this family were of the genus Ankylosaurus, by Peter Kaiser and Barnum Brown in Montana in 1906. Brown went on to name Ankylosauridae and the subfamily Ankylosaurinae in 1908.

Aptian

The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous epoch or series and encompasses the time from 125.0 ± 1.0 Ma to 113.0 ± 1.0 Ma (million years ago), approximately. The Aptian succeeds the Barremian and precedes the Albian, all part of the Lower/Early Cretaceous.The Aptian partly overlaps the upper part of the regionally used (in Western Europe) stage Urgonian.

The Selli Event, also known as OAE1a, was one of two oceanic Anoxic events in the Cretaceous period, which occurred around 120 Ma and lasted approximately 1 to 1.3 million years. The Aptian extinction was a minor extinction event hypothesized to have occurred around 116 to 117 Ma.

Dinosaur size

Size has been one of the most interesting aspects of dinosaur science to the general public and to scientists. Dinosaurs show some of the most extreme variations in size of any land animal group, ranging from the tiny hummingbirds, which can weigh as little as three grams, to the extinct titanosaurs, which could weigh as much as 90 tonnes (89 long tons; 99 short tons).Scientists will probably never be certain of the largest and smallest dinosaurs to have ever existed. This is because only a tiny fraction of animals ever fossilize, and most of these remain buried in the earth. Few of the specimens that are recovered are complete skeletons, and impressions of skin and other soft tissues are rare. Rebuilding a complete skeleton by comparing the size and morphology of bones to those of similar, better-known species is an inexact art, and reconstructing the muscles and other organs of the living animal is, at best, a process of educated guesswork. Weight estimates for dinosaurs are much more variable than length estimates, because estimating length for extinct animals is much more easily done from a skeleton than estimating weight. Estimating weight is most easily done with the laser scan skeleton technique that puts a "virtual" skin over it, but even this is only an estimate.Current evidence suggests that dinosaur average size varied through the Triassic, early Jurassic, late Jurassic and Cretaceous periods. Predatory theropod dinosaurs, which occupied most terrestrial carnivore niches during the Mesozoic, most often fall into the 100- to 1,000-kilogram (220 to 2,200 lb) category when sorted by estimated weight into categories based on order of magnitude, whereas recent predatory carnivoran mammals peak in the 10- to 100-kilogram (22 to 220 lb) category. The mode of Mesozoic dinosaur body masses is between one and ten metric tonnes. This contrasts sharply with the size of Cenozoic mammals, estimated by the National Museum of Natural History as about 2 to 5 kg (4.4 to 11.0 lb).

Minmi (disambiguation)

Minmi may refer to:

Minmi (born 1974), a Japanese hip hop singer.

Minmi paravertebra, a dinosaur species found in Australia

Minmi, New South Wales, a suburb of Newcastle, New South Wales, Australia

Timeline of ankylosaur research

This timeline of ankylosaur research is a chronological listing of events in the history of paleontology focused on the ankylosaurs, quadrupedal herbivorous dinosaurs who were protected by a covering bony plates and spikes and sometimes by a clubbed tail. Although formally trained scientists did not begin documenting ankylosaur fossils until the early 19th century, Native Americans had a long history of contact with these remains, which were generally interpreted through a mythological lens. The Delaware people have stories about smoking the bones of ancient monsters in a magic ritual to have wishes granted and ankylosaur fossils are among the local fossils that may have been used like this. The Native Americans of the modern southwestern United States tell stories about an armored monster named Yeitso that may have been influenced by local ankylosaur fossils. Likewise, ankylosaur remains are among the dinosaur bones found along the Red Deer River of Alberta, Canada where the Piegan people believe that the Grandfather of the Buffalo once lived.The first scientifically documented ankylosaur remains were recovered from Early Cretaceous rocks in England and named Hylaeosaurus armatus by Gideon Mantell in 1833. However, the Ankylosauria itself would not be named until Henry Fairfield Osborn did so in 1923 nearly a hundred years later. Prior to this, the ankylosaurs had been considered members of the Stegosauria, which included all armored dinosaurs when Othniel Charles Marsh named the group in 1877. It was not until 1927 that Alfred Sherwood Romer implemented the modern use of the name Stegosauria as specifically pertaining to the plate-backed and spike-tailed dinosaurs of the Jurassic that form the ankylosaurs' nearest relatives. The next major revision to ankylosaur taxonomy would not come until Walter Coombs divided the group into the two main families paleontologists still recognize today; the nodosaurids and ankylosaurids. Since then, many new ankylosaur genera and species have been discovered from all over the world and continue to come to light. Many fossil ankylosaur trackways have also been recognized.

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