Minmi
Name: Minmi
(After Minmi crossing, Australia).
Phonetic: Min-me.
Named By: Ralph Molnar - 1980.
Classification: Chordata, Reptilia, Dinosauria,
Ornithischia, Thyreophoroidea, Ankylosauria.
Species: M. paravertebra
(type).
Diet: Herbivore.
Size: estimated between 2 and 3 meters long.
Known locations: Australia, Minmi crossing.
Time period: Aptian of the Cretaceous.
Fossil representation: Two confirmed individuals,
one of which is almost complete. Possible further fragments.
Well
preserved dinosaur remains are rare from Australia, but Minmi
is one
of the exceptions. This is in part due to the small body size of
Minmi which meant that it would have been more
easily buried than a
larger animal, something that would have protected the remains from
being scattered by scavengers and weather. Fortunately the remains
were discovered before they were exposed to the full effects of
today’s Australian climate which can quickly erode and damages
valuable fossil specimens when they are exposed.
The
phylogenetic placement of Minmi is a little
awkward, but currently it
sits within the Ankylosauria as a basal ankylosaur.
Minmi
is not
considered to be a true member of the more advanced ankylosaurids
because it lacks some key defining characteristics of this group.
Still Minmi was what is termed an armoured
dinosaur, and it seems
that Minmi had a variety of different armoured
osteoderms (bony
armour plates that are also sometimes referred to as scutes) that ran
across its back. While the main body seems to have had an assortment
of smaller osteoderms, larger ones were present on more vulnerable
areas such as the neck, head, shoulders and hips, all areas that
predators usually target to make a quick kill. Although still
uncertain, the large osteoderms may have formed tall spikes that
would have made it even more difficult for a predatory dinosaur to jump
onto, or larger ones like Australovenator
to bite down on. It’s
also considered possible that these larger osteoderms spikes also
continued down the length of the tail, but fossil material is still
lacking to confirm this. One key area of difference between the
armour of Minmi and that of the later ankylosaurids
are the
horizontally arranged osteoderms that ran parallel to the vertebra
rather than the ribs. This is reflected in the specific species name
of M. paravertebra.
Perhaps
the most exciting discovery associated with Minmi
is that of a
cololite, a food pellet that would have been inside the stomach of
the living dinosaur that reveals what kind of food it ate. Analysis
revealed the presence of seeds, fruit and both fibrous vascular
(stems, leaves) and vesicular (spore) plant tissue. While
the fruit and seeds seem to have been swallowed the more fibrous
tissues show signs of being cleanly cut in very small sections. This
has helped confirm the theory that armoured dinosaurs like Minmi
relied upon processing their food in their mouths rather than using
gastroliths (swallowed stones) to process the food for them.
Teeth in these dinosaurs are more adapted to chopping rather mashing,
and wear damage in other genera shows that the teeth of the upper and
lower jaws came together in a shearing action. By chopping food in
the mouth into smaller pieces, a greater surface area is exposed to
the digestive acids so that far more efficient digestion can take
place. This also hints that in life Minmi, and
other similar
dinosaurs, actually had cheeks to stop food from falling out of the
sides of the mouth as it was being processed.
One
more bit of trivia, Minmi once had the shortest
dinosaur name, a
title it held onto for twenty-four years until the naming of Mei
in
2004. Now dinosaur names are even shorter with the 2015 naming of the
genus Yi.
Further reading
- An ankylosaur (Ornithischia, Reptilia) from the Lower Cretaceous of
southern Queensland - Ralph E. Molnar - 1980.
- The paravertebral elements of the Australian ankylosaur Minmi
(Reptilia: Ornithischia, Cretaceous). - Neues Jahrbuch f�r Geologie und
Pal�ontologie, Abhandlungen. 175: 19–37. - R. E. Molnar & E.
Frey - 1987.
- Preliminary report on a new ankylosaur from the Early Cretaceous of
Queensland, Australia. - Memoirs of the Queensland Museum. 39 (3):
653–668. - R. E. Molnar - 1996.
- Gut Contents of a Small Ankylosaur. - Journal of Vertebrate
Paleontology. & Taylor & Francis, Ltd. 20 (1): 194–196.
- Ralph E. Molnar & H. Trevor Clifford - 2000.
- First evidence of ankylosaurian dinosaurs (Ornithischia: Thyreophora)
from the mid-Cretaceous (late Albian-Cenomanian) Winton Formation of
Queensland, Australia. - Alcheringa. 37 (2): 249–257. - L. G. Leahey
& S. W. Salisbury - 2013.
- 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. - Lucy
G. Leahey, Ralph E. Molnar, Kenneth Carpenter, Lawrence M. Witmer
& Steven W. Salisbury - 2015.
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