Extreme armour in the world's oldest ankylosaur

Area of Science:

• Paleontology
• Vertebrate Paleontology
• Dinosaur Evolution

Background:

• The early evolution of armored ankylosaurian dinosaurs during the Early-Middle Jurassic is poorly understood due to limited fossil evidence.
• Previous discoveries, like Spicomellus afer from Morocco, were based on scant remains, leaving its evolutionary position uncertain.

Purpose of the Study:

• To describe a new, more complete Spicomellus afer fossil specimen.
• To confirm the ankylosaurian affinities of Spicomellus afer.
• To investigate the evolutionary history of ankylosaur dermal armor and tail weapon development.

Main Methods:

• Paleontological excavation and specimen recovery.
• Detailed anatomical description and comparative analysis of fossil remains.
• Phylogenetic analysis to determine evolutionary relationships.

Main Results:

• The new Spicomellus afer specimen exhibits exceptionally elaborate dermal armor, distinct from any known vertebrate.
• The presence of 'handle' vertebrae in the tail indicates the existence of a tail weapon, predating previously known occurrences in ankylosaurs.
• This finding challenges the established timeline for tail club evolution in ankylosaurs, suggesting an earlier origin in the Early Cretaceous.

Conclusions:

• Spicomellus afer possessed unique, ornate armor possibly used for display and defense.
• The early evolution of tail weapons in ankylosaurs is confirmed to be in the Middle Jurassic.
• Armor reduction in later ankylosaurs may reflect shifts in defensive strategies or social behaviors.