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I hope I don't offend or confuse any of my fellow bucketeers with this bucket.  Despite the fanciful language it does contain plenty of factual information about some fascinating sharks.  Please see this diary for the back story.

From the fuliginous depths of the hidden city I write.  Casting aside my usual despairing tone as I document the squamous horrors that undulate through the drowned avenues of R'lyeh I will attempt to provide some useful information for those of you clinging to the illusion of normalcy in the sliver of atmosphere lying between the noisesome depths and the frigid emptiness that is yet so horribly not empty and stretches infinitely off from our tiny planet.

But I see I have lapsed into my usual prose.  My apologies as I will try to maintain the reserved tone of the scientist throughout.  It is my understanding that a televised film of unspeakable horror recently aired.  Something to do with voracious sharks that perambulate using waterspouts.  Intriguing to be sure, and no doubt a worthy addition to the canon of Selachian horror.  But there is such a diverse array of foully loathsome and hideously unspeakable Chondrichthians in the inky blackness that is my home that I feel that the film industry is not taking full advantage of its source material.  So as a public service I am presenting an overview of some of the sharks that frequent my 'backyard' if a gaping, jagged-rimmed, cavern with unplumbed depths and noisesome currents in the far deeps of the ocean can be considered a yard.

The Daily Bucket is a place where we post and exchange our observations about what is happening in the natural world in our neighborhoods. Birds, blooms, bugs & more - each note is a record that we can refer to in the future as we try to understand the patterns that are quietly unwinding around us.
Above is the bucket text giving instructions for you dear readers and below the rusting miasma is my essay on my local Elasmobranchs.  Once again my apologies for failing to completely disguise the tone of abyssal melancholy from my report.

Sharks are members of that inchoate and unsettling group of ichthyian beings known as the Chondrichthyes or cartilaginous fishes.  These are the most ancient living group of jawed vertebrates.  The jawless vertebrates are a more ancient and thoroughly noxious pair of lineages whose vermiform modern representatives are the vampiric lampreys and necrophagic hagfish.  Both of which are long overdue for their place in the annals of fiscally restrained cinematic horror.

Lamprey Mouth
The lamprey mouth with it horrifying teeth and uncanny lack of mandible and maxilla.
Pacific Hagfish feeding
Hagfish feeding in their typically foul fashion in the chartless depths.

But I digress. The cartilaginous fishes betray their ancient origins in both their lack of bone and the unusually large of gill openings.  Typical Chondrichthyes have five gill openings on each side but a few have six or even seven.

Before I delve into the abominable morass of shark varieties I will make passing mention of their most unusual relatives the Holocephali or Chimaeras.  Like their mythological namesakes these creatures appear to an amalgam of other animals.  They are mostly creatures of the deep sea and little is known of their habits although I suspect them of raiding my algal gardens from time to time.

Drawing of a Chimaera
Chimaera
Chimaeras as envisioned by an artist driven half mad with unspeakable visions and in the unsettling flesh.

The sharks and their close relatives the rays are united in unspeakable union in a group known as the Elasmobranchii.  Much uncertainty has existed about the relationships among the Elasmobranchs.  Three groups are generally recognized.  Many excellent examples of convergent evolution occur in these groups which can lead to confusion.  The Batoids are the skates, rays and their relatives.  Typically they have pectoral fins that are greatly expanded and extended forward to form a disk.  This disk results in the gill slits being on the underside of the animal rather than on the side.  Some batoids such as guitarfish and sawfish have a sharklike body, they can be recognized as batoids by the position of their gill slits.  Although unearthly in appearance and often armed with vicious weaponry I will leave the batoids for another day.

Those creatures known as sharks are divided into two groups: the Galeomorphs and the Squalomorphs.  Most sharks that the average human, happily ignorant of the true state of the universe, is aware of, are Galeomorphs.  The Squalomorphs are also a diverse and abundant group but are primarily deep or cold water creatures and are much less likely to be encountered by humans foolish enough to enter the primordial sea with all its attendant peril.

Among the most ancient of the sharks is the frilled shark, notable for its extra gill slit on each side.  Also for its elaborate teeth and generally terrifying appearance.  This meter long creature is mostly a deep water animal is rarely found near the surface.  Science claims they are harmless to humanity but their mere appearance could lead to heart-stopping horror.

Frilled Shark

Frilled Shark
Close Up of Frilled Shark Teeth.  
Frilled Shark Teeth
The cookiecutter shark is a small unassuming fish which reveals a truely nightmarish visage when examined closely.  These tiny sharks live in open water and prey on marine animals much larger than themselves.  They have greatly enlarged teeth arranged in a circle around their mouth.  They use these teeth to incise neat chunks of flesh from hapless larger fish and marine mammals.  Normally these sharks live in habitats where humans do not swim but there have been isolated cases of the diminutive and diabolical creatures biting swimmers or divers in deep water.

Cookiecutter Shark

Cookiecutter Shark Head
However the cookiecutter is not the smallest of sharks.  Deep in the ocean dwell a myriad of species of lanternsharks, small, odd-looking fishes with an eerie phosphorescence over parts of their bodies (hence the name).  Supposedly they are harmless but unearthly creatures with huge green eyes that lure unsuspecting prey to their doom using their glowing bellies.

Dwarf Lanternshark

Dwarf Lanternshark
Another close relative is the Viper Dogfish.  Not much is known about this fiend from the frigid void but its dentition should give one pause.  Apparently this fiendish creature uses the elongate teeth to grasp large prey in true ophidian fashion and swallow them whole!

Viper Dogfish

Viper Dogfish (head)
Amongst the Galeomorph sharks there are other weird and antediluvian representatives.  Perhaps the most bizarre is the Goblin Shark.  This pale, flabby-bodied beast has an elongated snout and long slender teeth in an exposed mouth giving it an appearance that is noxious to an almost unprecedented degree.  Although rarely even encountered by humans its ghastly appearance and large size are striking if not downright unearthly.

Preserved Goblin Shark from Australia

Goblin Shark
The Megamouth Shark is a true behemoth of the abyss.  It is also a rarely encountered reminder of how little you blissfully ignorant surface dwellers know about the lightless depths.  Despite its great size this shark was unknown to science until the 1970s.  As its name indicates it has a vast maw which is used to feed on plankton.
Megamouth Shark
Finally here is a shallow water species.  The Tasseled Wobbegong occurs in the waters of the Indopacific region.  I know little of its natural history but from its appearance I would judge it to be an acolyte of the old one that lies lost in dreams in the same drowned city that I call my home.
Tasselled Wobbegong

I'd like to end on a more serious note.  The shark described in this diary generally live in remote habitats deep in the ocean.  They are mostly not the subject of commercial fisheries.  Yet because of the great reach of today's fishing technology they are sometimes caught as by catch.  The extent to which this impacts their populations is unknown.



"Green Diary Rescue" is Back!

After a hiatus of over 1 1/2 years, Meteor Blades has revived his excellent series.  As MB explained, this weekly diary is a "round-up with excerpts and links... of the hard work so many Kossacks put into bringing matters of environmental concern to the community... I'll be starting out with some commentary of my own on an issue related to the environment, a word I take in its broadest meaning."

"Green Diary Rescue" will be posted every Saturday at 1:00 pm Pacific Time on the Daily Kos front page.

Originally posted to Backyard Science on Sun Jul 21, 2013 at 05:06 AM PDT.

Also republished by Community Spotlight.

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