Armoured Exoskeleton

Tyranid Power Armour. That's all you need to know.

An exoskeleton is basically a rigid, usually chitinous structure that acts as a skeletal structure for organisms that lacks a supporting endoskeleton. Invertebrates like insects, crustaceans and arachnids all have an exoskeleton. Advantage of exoskeletons is that they are tough, hard and provide a protective shell. Disadvantages include being inflexible, restrictive and once breached, liable to infection. In 40k, an Exoskeleton is presented in all insectoid Xenos, although the Tyranids are the biggest users of these and they have made theirs 'armoured'.

Overview

There are two forms of Armoured Exoskeletons which serve as armour for the Nids. The first is called the Toughened Exoskeleton, which are the exoskeleton of the creature that has been enhanced through toughening processes, which makes it more durable and able to resist more damage before failing.

The second is called the Bonded Exoskeleton. A Bonded Exoskeleton is only found on larger Tyranid organisms. Bonded Exoskeleton is formed when every bone-like plate and chitinous segment of a bio-form's exoskeleton is grown and fused together to form a tough and virtually impenetrable sheathing which offers a similar level of protection to the ceramite used by Imperial Space Marines in their Power Armour. The most common Tyranid bioforms evolved to have Bonded Exoskeletons are Hive Tyrants, Tyrant Guard, Tervigons, Carnifexes, Trygons and Mawlocs.