Minmi paravertebra

Minmi paravertebra was a small armored dinosaur that inhabited what is now Australia during the Early Cretaceous, approximately 119 to 113 million years ago. It is one of the earliest and most complete representatives of ankylosaurs discovered in Gondwana, and its discovery has been key to understanding the early evolution of armored dinosaurs in the Southern Hemisphere. Its specific name, paravertebra , refers to a unique feature: the presence of elongated ossifications located lateral to the dorsal vertebrae, which were initially considered unique dermal structures, although today they are interpreted as modifications within the repertoire of ankylosaurian armor.

The type specimen of Minmi was found in the Bungil Formation of Queensland, in rocks dating back to the Aptian age. Unlike many other ankylosaurs, whose remains are often fragmentary, the holotype of Minmi is remarkably well preserved, including parts of the postcranial skeleton, elements of the skull, and abundant skin covering. This degree of preservation has allowed for detailed anatomical evaluations and has provided crucial evidence about its morphology and lifestyle.

In terms of size, Minmi was small compared to other ankylosaurs, reaching approximately 3 meters in length and weighing around 300 kilograms. Its body was low, stocky, and wide, giving it stability, and was covered by bony plates (osteoderms) of various sizes, distributed on the back, flanks, and possibly the tail. These structures formed an effective passive defense against predators, which in its ecosystem could have included theropods such as Australovenator . Unlike more advanced ankylosaurs such as Ankylosaurus , Minmi lacked a developed bony caudal club, suggesting a defensive approach more based on static armor and low mobility than on active confrontation.

A distinctive feature of Minmi is the presence of ossa paravertebralia: bony plates aligned parallel to the dorsal vertebrae, the function of which is still debated. These could have served as structural reinforcement of the spine, or as additional anchorage for the axial musculature, contributing to greater trunk rigidity. They could also have had a secondary protective function, forming a more internal barrier between the spine and potential bites.

Minmi 's dentition was simple, with small crowns and slightly serrated edges, adapted for a herbivorous diet based on low vegetation. Its skull was small and broad, with a robust lower jaw but no evidence of extensive bite musculature. This indicates passive, low-process oral feeding, likely complemented by efficient intestinal fermentation. Like other ankylosaurians, Minmi had a wide digestive canal, suggesting a specialized fermentation system for extracting nutrients from fibrous, low-quality plants.

From a phylogenetic perspective, Minmi has been the subject of multiple revisions. Although initially considered a basal member of Ankylosauria, some more recent analyses have questioned its exact position, and more conservative proposals place it as a basal taxon within Ankylosauridae or even as a node close to Nodosauridae. Its intermediate morphology and geographic distribution make it an important point of comparison for understanding the evolution and dispersal of ankylosaurs in Gondwana.

Approximate measurements of the Minmi :

• Scale 1:35 - Complete
• Length 77 mm
• Height 38 mm
• Width 26 mm
• Snout-tail length 88 mm

• Scale 1:20 - Complete
• Length 134 mm
• Height 66 mm
• Width 45 mm
• Snout-tail length 150 mm