On my last visit to Nisqually NWR, a dead spotted ratfish,
Hydrolagus colliei, was washed up on the mudflat.
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I have no idea of the cause of death. While other ratfish species are more typically found in deep water, I have encountered spotted ratfish several times while diving in the San Juan Islands (and they are pretty common in research otter trawls). They are pretty wary of divers and will swim away by flapping their pectoral fins. Unlike the replaceable teeth of sharks, ratfish have plate-shaped incisors on the upper and lower jaw (hence the genus name Hydrolagus = "water" "rabbit").
The ratfish have been placed in their own class, the Holocephali, within the class Chondrichthyes (cartilaginous fishes). Unlike the other Chondrichthyans, the upper jaws of ratfishes are fused to their skulls. Also, ratfishes have a single gill opening per side, while other Chondrichthyans have 5-7 gill slits per side.
Steve