Chrysomallon squamiferum, common name the scaly-foot gastropod, is a species of deep-sea hydrothermal-vent snail, a marine gastropod mollusc in the family Peltospiridae. This vent-endemic gastropod is known only from deep-sea hydrothermal vents in the Indian Ocean, where it has been found at depths of about 2,400–2,800 m (1.5–1.7 mi). Chrysomallon squamiferum differs greatly from other deep-sea gastropods, even the closely related neomphalines. The shell is of a unique construction, with three layers; the outer layer consists of iron sulfides, the middle layer is equivalent to the organic periostracum found in other gastropods, and the innermost layer is made of aragonite. The foot is also unusual, being armored with iron-mineralised sclerites. The snail's oesophageal gland houses symbiotic gammaproteobacteria from which the snail appears to obtain its nourishment. This species is considered to be one of the most peculiar deep-sea hydrothermal-vent gastropods, and it is the only known extant animal that incorporates iron sulfide into its skeleton (into both its sclerites and into its shell as an exoskeleton). Its heart is, proportionately speaking, unusually large for any animal: the heart comprises approximately 4% of its body volume. (Read more...)