Despite their obvious differences, both mollusc shells and arthropod cuticle contain chitin .
There are a few other animal carbohydrates, notably chitin , the substance which constitutes the hard outer casing of insects and crustaceans.
Arthropods have a stiff cuticle made largely of chitin and proteins, forming an exoskeleton that may or may not be further stiffened with calcium carbonate.
Finally, like other fungi, chytrids have chitin strengthening their cell walls, and one subgroup have cellulose as well, a trait unique among living fungi.
Chitinases are hydrolytic enzymes that catalyze the degradation of chitin , a major component of fungal cell walls.
A chitinous exoskeleton is not rigid enough to support a mass of that size.
But this time… ‘Dancer held up her elongated forearms, staring at her pale, chitinous claws.’
Eurypterid cuticle was chitinous and of varying thickness, but generally very thin, and preserved specimens (which were probably mostly molted skins) are usually crushed.
In addition, examination of the chitinous cuticle that covers the surface of the infundibulum reveals a remarkable array of tiny pegs or ‘denticles’.
They are the earliest well-known complex three-dimensional trace fossils; mostly small, chitinous , calcareous, and phosphatic elements of problematic affinity.