Hinterland Green

Thursday, September 24, 2009

Eastern Pacific Black Ghostshark, An Ancient And Bizarre Fish Discovered in Off Coasts of California And Baja California

An ancient and bizarre species of fishes, distantly related to sharks, has been discovered off the coast of Southern California and Baja California, Mexico. The new species, named the Eastern Pacific black ghostshark (Hydrolagus melanophasma), is the first new species of cartilaginous fish to be described from California waters since 1947. According to Science Daily, chimaeras, also called ratfish, rabbitfish, and ghostsharks, are possibly the oldest and most enigmatic groups of fishes alive today. Their evolutionary lineage branched off from sharks nearly 400 million years ago, and they have remained an isolated group ever since.

They are similar to sharks, in that they have skeletons composed of cartilage and the males have claspers for internal fertilization of females. The difference is manifest in the male chimaeras, which also have retractable sexual appendages on the forehead and in front of the pelvic fins and a single pair of gills. Most species also have a mildly venomous spine in front of the dorsal fin.
Chimaeras were once a very diverse and abundant group, as illustrated by their global presence in the fossil record. They survived through the age of dinosaurs mostly unchanged, but today these fishes are relatively scarce and are usually confined to deep ocean waters, where they have largely avoided the reach of explorers and remained poorly known to science.

This new species belongs to the genus Hydrolagus, Latin for 'water rabbit' because of its grinding tooth plates reminiscent of a rabbit's incisor teeth. This new species was originally collected as early as the mid 1960s, but went unnamed until this year because its taxonomic relationships were unclear. A large blackish-purple form, Hydrolagus melanophasma (melanophasma is Latin for 'black ghost'), is found in deep water from the coast of Southern California, along the western coast of Baja California, and into the Sea of Cortez (Gulf of California). This species is known from a total of nine preserved museum specimens, and from video footage taken of it alive by a deep-water submersible in the Sea of Cortez. Source: Science Daily
This is phenomenal and with continued advances in research and discovery, perhaps more will be known about these living fossils and their diversity in the world's oceans.

Photo credit: ghostshark, Science Daily
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