Spicomellus Fossil Reveals Unusual Dinosaur Armor Design

• Newly uncovered fossils in Morocco suggest early ankylosaurs had elaborate spikes and armor, possibly for display as well as defense.

A Jurassic Discovery with Unconventional Features

Paleontologists have identified a highly unusual dinosaur species from the Jurassic Period, based on fossil remains found in Morocco’s Atlas Mountains. Named Spicomellus, the creature lived approximately 165 million years ago and is now considered the earliest known member of the ankylosaur group. Measuring around four meters in length and weighing up to two tons, it was a slow-moving herbivore with a body covered in spikes and plates. Unlike any other known dinosaur, Spicomellus had sharp spikes protruding from its ribs and a collar of long spines around its neck.

The fossils were discovered near Boulemane and include parts of the back, pelvis, and tail, though the skull was not recovered. Researchers noted that the dinosaur’s armor was unusually elaborate, with some neck spikes reaching nearly one meter in length. These features may have served multiple purposes, including protection from predators and visual signaling during mating or territorial disputes. The impracticality of such large spikes in dense vegetation suggests that display may have played a significant role in their evolution.

Implications for Ankylosaur Evolution

Spicomellus challenges previous assumptions about the early evolution of ankylosaurs, which are typically known for their compact, tank-like bodies and defensive tail clubs. The presence of fused tail vertebrae in the fossil indicates that tail weapons may have appeared in the group 30 million years earlier than previously thought. Later ankylosaurs, such as the well-known Ankylosaurus from North America, had simpler armor and more specialized defensive features. This contrast suggests a shift in evolutionary priorities, possibly driven by increasing predation during the Cretaceous Period.

Ankylosaurs and their close relatives, the stegosaurs, both emerged during the Jurassic but followed different evolutionary paths. While stegosaurs featured bony plates and spiked tails, ankylosaurs developed more extensive body armor and survived until the end of the dinosaur era. Spicomellus stands out for having the most elaborate armor seen in the group, despite being its earliest known representative. Researchers speculate that later species may have streamlined their defenses in response to environmental pressures and predator behavior.

Fossil Context and Broader Significance

The discovery builds on earlier findings, including a rib fragment described in 2021, and offers a more complete picture of Spicomellus’ anatomy. Its back was lined with short spikes, and the pelvis featured a shield with outward-projecting spikes above the hips. Although no tail weapon was found, the fused vertebrae strongly suggest one was present during the animal’s life. These traits align with known ankylosaur characteristics but introduce new complexity to the group’s early development.

Lead researchers Richard Butler and Susannah Maidment emphasized the uniqueness of Spicomellus’ armor and its potential role in social behavior. Comparisons to modern animals, such as deer and peacocks, support the idea that some features evolved for display rather than function. The study, published in Nature, adds to growing evidence that early dinosaurs were more diverse and specialized than previously believed. As new fossils continue to emerge, the understanding of dinosaur evolution and behavior is likely to expand further.