About Minmi
| Scientific Name (Genus) | Minmi |
| Meaning of Name |
Named after Minmi (a place name in Australia)
Minmi [Place name] |
| Classification | Ornithischia, Thyreophora (Parankylosauria) |
| Total Length | Approx. 3m |
| Diet | Herbivorous |
| Period | Early Cretaceous (approx. 120 to 115 million years ago) |
| Sub-classification / Species Name | Minmi paravertebra |
| Year of Paper Publication | 1980 |
| Genus Name Publication |
An ankylosaur (Ornithischia: Reptilia) from the Lower Cretaceous of southern Queensland.
Memoirs of the Queensland Museum. 20. 65–75. by Molnar, R.E. 1980. |
A Small Armored Dinosaur Representing Australia
Minmi was a small armored dinosaur that lived on the Australian continent during the Early Cretaceous. It was once thought that armored dinosaurs (Thyreophora) only existed in the Northern Hemisphere, but Minmi was the first armored dinosaur discovered in the Southern Hemisphere.
As an endemic species representing Australian dinosaurs, its appearance has been depicted in many encyclopedias for a long time. However, recent research has revealed that the image of Minmi we have known was actually a confusion of "two different dinosaurs."
The First Dinosaur: Features of "Minmi"
The fragmentary fossils first discovered in Queensland, Australia, in 1964 are the real "Minmi" (Minmi paravertebra). These fossils included vertebrae, ribs, and belly armor.
Its most prominent feature is the special bony plates running along the sides of its spine called "paravertebrae." This structure is similar to how modern crocodiles reinforce their backs when walking with their bodies lifted. It is thought that Minmi also maintained its core and was able to run thanks to these paravertebrae. In addition, its legs were relatively long and slender compared to typical armored dinosaurs of the Northern Hemisphere, leading to the speculation that it was capable of "active escape behavior," running away even from large carnivorous dinosaurs.
An ossified tendon-like structure that provides a strong attachment point for back muscles. It is thought to have prevented the spine from undulating excessively while running, efficiently converting the power generated by its long legs into forward propulsion.
Furthermore, on its belly—which is the greatest weak point for general armored dinosaurs—it had "belly armor" consisting of densely packed small bony plates like paving stones. This structure served as the last line of defense to prevent a fatal blow even if it was flipped over by a carnivorous dinosaur.
The Second Dinosaur: Separation into "Kunbarrasaurus"
In 1989, a miraculous fossil of an armored dinosaur (the Marathon specimen) with its skull, tail, and full-body armor preserved in three dimensions was discovered in Australia. Initially, this was thought to be a "complete specimen of Minmi," and the appearance of Minmi depicted in encyclopedias around the world was based on this specimen.
*Note: Most of the reconstructions and skeletons known as "Minmi" actually belong to a different species, Kunbarrasaurus.
However, in 2015, as a result of detailed investigations using the latest technologies such as CT scanning, it was found that this fossil was a completely different species from Minmi. It was named "Kunbarrasaurus" (Kunbarrasaurus ieversi), meaning "shield" in the local indigenous language. Therefore, a real Minmi skull has still not been found, and its full-body appearance remains shrouded in mystery.
Diet: Discovery of Cololite (Fossilized Intestinal Contents)
A rare fossil called a "cololite" has been discovered from the fossil of Kunbarrasaurus, which was once thought to be the same genus as Minmi. This was an important discovery for understanding the ecology of this group, including Minmi.
The "last meal" left in the stomach or intestines of a dinosaur that has been fossilized as is. It is extremely valuable evidence that allows us to directly know exactly what and how herbivorous dinosaurs ate.
When the cololite was examined under a microscope, it contained ferns, seeds, and fruits. These plants were not ground up by gastroliths (stomach stones), but were neatly sliced into pieces about 1-2 millimeters long, as if cut with scissors. This indicates that they had a sophisticated chewing ability to precisely chop plants in their mouths.
"Parankylosauria", a Uniquely Evolved Group
According to a 2021 study, the armored dinosaurs that lived in the Southern Hemisphere (Gondwana), such as Minmi and Kunbarrasaurus from Australia and Stegouros from South America, were grouped into a new unique group called "Parankylosauria."
Meaning "beside Ankylosaurus," this is a group of armored dinosaurs specific to the Southern Hemisphere. It is thought that they split from the Northern Hemisphere groups around the Middle Jurassic and evolved independently in different environments.
While armored dinosaurs in the Northern Hemisphere (such as Ankylosaurus) grew their bodies and went down the path of heavy armor to counter large carnivorous dinosaurs, the Parankylosauria in the Southern Hemisphere chose a completely different evolutionary path. They found "another optimal solution" of surviving by maintaining a small body size, utilizing the mobility provided by their long legs, and using belly armor as a clever defense in emergencies.
Discovery and Paper Publication
Source: An ankylosaur (Ornithischia: Reptilia) from the Lower Cretaceous of southern Queensland.
Memoirs of the Queensland Museum. 20. 65–75.
by Molnar, R.E. 1980.
In 1964, a collaborator of the Queensland Museum in Australia discovered the first fossil (holotype specimen) near Minmi Crossing, north of Roma. Later, in 1980, it was described by paleontologist Ralph E. Molnar as a new genus and species, "Minmi paravertebra."
Incidentally, at the time of its naming, the name "Minmi" was widely known and loved for having the shortest name among Mesozoic dinosaurs. (Today, this record has been broken by dinosaurs discovered in China, such as "Mei" and "Yi.")
Minmi Stamp and Fossil Gallery
