A good specimen Macrophtalmus crab discovered in Madagascar which dates to the Pliocene period. The carapace [body shell] and limbs in their placement positions with both claws intact, the back two legs are the swimming appendages, these missing the terminal segments.
After minor preparation and restoration, this Macrophtalmus specimen shows good detail throughout the carapace, this hard bone is a substance known as chitin.
Chitin is a polymer which is the main component of arthropod's exoskeletons. The main composites of the chitin are minerals in the form of calcite or amorphous calcium carbonate, an inorganic mineral. The minerals are tightly woven in a matrix, which gives great strength to the crab's body shell. The numbers of calcium carbonate particles determine the hardness of the exoskeleton, which may vary both according to species.
The fossil beds lie in the former Mahajanga Province [Majunga Province, in colonial French] The fossil carapace date from the Pliocene epoch approximately 5,300,000 years [Zanclean age] to 2,600,000 years [Piacenzian age] ago.