Deep Sea Chimaera

Our Deepwater Backyard: Exploring Atlantic Canyons and Seamounts 2014 (September 27, 2014)

Chimaera spotted while exploring a seamount within the Atlantis II Seamount Complex.

Video courtesy of NOAA Okeanos Explorer Program.

Bizarre, Prehistoric Ratfish Chomped Prey with Buzzsaw Jaws
by Brian Switek 
Helicoprion had saws for jaws. That’s really all there was to the 270 million year old ratfish’s dental cutlery. No upper teeth or anything else to slice against – just an ever-growing whorl of spiky teeth anchored to the lower jaw.
This new, definitive image of Helicoprion debuted last year thanks to the efforts of artist Ray Troll and a team of researchers led by Idaho State University paleontologist Leif Tapanila. A very special fossil – IMNH 37899 – preserved both the upper and lower jaws in a closed position, finally solving the mystery of what the ratfish’s head actually looked like. But determining the exact placement of that vexing spiral was just an initial step.
Paleontologists and artists had often supposed that Helicoprion had upper teeth to pierce slippery cephalopods and squirming fish, but the fossils Tapanila and colleagues examined showed that Helicoprion only had a buzzsaw embedded in the lower jaw. How did this long-lived and prolific genus of Permian fish eat with a saw for a jaw? …
(read more: Laelaps blog - National Geographic)
photograph by Brian Switek

Bizarre, Prehistoric Ratfish Chomped Prey with Buzzsaw Jaws

by Brian Switek 

Helicoprion had saws for jaws. That’s really all there was to the 270 million year old ratfish’s dental cutlery. No upper teeth or anything else to slice against – just an ever-growing whorl of spiky teeth anchored to the lower jaw.

This new, definitive image of Helicoprion debuted last year thanks to the efforts of artist Ray Troll and a team of researchers led by Idaho State University paleontologist Leif Tapanila. A very special fossil – IMNH 37899 – preserved both the upper and lower jaws in a closed position, finally solving the mystery of what the ratfish’s head actually looked like. But determining the exact placement of that vexing spiral was just an initial step.

Paleontologists and artists had often supposed that Helicoprion had upper teeth to pierce slippery cephalopods and squirming fish, but the fossils Tapanila and colleagues examined showed that Helicoprion only had a buzzsaw embedded in the lower jaw. How did this long-lived and prolific genus of Permian fish eat with a saw for a jaw? …

(read more: Laelaps blog - National Geographic)

photograph by Brian Switek

ichthyologist
naturalose:

Species in the Rhinochimaera family are known as long-nosed chimaeras. Their unusually long snouts (compared to other chimaeras) have sensory nerves that allow the fish to find food. Also, their first dorsal fin contains a mildly venomous spine that is used defensively. They are found in deep, temperate and tropical waters between 200 to 2,000 m in depth, and can grow to be up to 140 cm (4.5 ft) in length.
Chimaeras (also known as ghost sharks and ratfish) are an order of cartilaginous fish most closely related to sharks, but they have been evolutionarily isolated from them for over 400 million years.
(Info from WP and .gif from video by NOAA’s Okeanos Explorer—this is not an animation!)

naturalose:

Species in the Rhinochimaera family are known as long-nosed chimaeras. Their unusually long snouts (compared to other chimaeras) have sensory nerves that allow the fish to find food. Also, their first dorsal fin contains a mildly venomous spine that is used defensively. They are found in deep, temperate and tropical waters between 200 to 2,000 m in depth, and can grow to be up to 140 cm (4.5 ft) in length.

Chimaeras (also known as ghost sharks and ratfish) are an order of cartilaginous fish most closely related to sharks, but they have been evolutionarily isolated from them for over 400 million years.

(Info from WP and .gif from video by NOAA’s Okeanos Explorer—this is not an animation!)

The  elephant shark, Callorhinchus milii 
… is a cartilaginous fish (not actually a shark but a ratfish or chimera) native to the Southwest Pacific off southern Australia and New Zealand. Because of its relatively small genome, this species has been targeted as a model organism for vertebrate molecular evolution. In a whole-genome analysis published in Nature today, Byrappa Venkatesh & colleagues report that the elephant shark has the slowest rate of evolution of any known vertebrate. Its genome has not changed substantially in hundreds of millions of years. Comparison of the elephant shark genome with those of other vertebrates also provides intriguing insights into the evolution of vertebrate skeletons and immune systems. 
Check out the paper for details More about this species: Encyclopedia of LifeImage by fir0002 | flagstaffotos.com.au via Wikimedia Commons 

The elephant shark, Callorhinchus milii

… is a cartilaginous fish (not actually a shark but a ratfish or chimera) native to the Southwest Pacific off southern Australia and New Zealand. Because of its relatively small genome, this species has been targeted as a model organism for vertebrate molecular evolution.

In a whole-genome analysis published in Nature today, Byrappa Venkatesh & colleagues report that the elephant shark has the slowest rate of evolution of any known vertebrate. Its genome has not changed substantially in hundreds of millions of years. Comparison of the elephant shark genome with those of other vertebrates also provides intriguing insights into the evolution of vertebrate skeletons and immune systems.

Check out the paper for details

More about this species: Encyclopedia of Life

Image by fir0002 | flagstaffotos.com.au via Wikimedia Commons 

'Elephant Shark' Takes Record for Slowest Evolution
by Bob Homes
It’s a living fossil to beat all others. The elephant shark, Callorhinchus milii, has the slowest-evolving genome of any vertebrate.
C. milii is not actually a true shark but belongs to a group known as ratfish, which diverged from sharks about 400 million years ago. When a team led by Byrappa Venkatesh of the Institute of Molecular and Cell Biology in Singapore compared its genome with those of other vertebrates, they found it had changed less from its presumed ancestral form than any other.
C. milii outstrips the coelacanth, the fish that previously held the slow-evolution record.
Such limited change means the elephant shark’s genome is the closest yet to that of the first jawed vertebrate, which lived more than 450 million years ago and gave rise to many modern animals including humans. It makes the elephant shark an important reference point for unlocking how this long-lost ancestor evolved. As well as jaws, the earliest fish pioneered bony skeletons and a sophisticated immune system, but it is not known when or how these features appeared…
(read more: New Scientist)
photo: Kelvin Aitken/V and W/Image Quest Marine

'Elephant Shark' Takes Record for Slowest Evolution

by Bob Homes

It’s a living fossil to beat all others. The elephant shark, Callorhinchus milii, has the slowest-evolving genome of any vertebrate.

C. milii is not actually a true shark but belongs to a group known as ratfish, which diverged from sharks about 400 million years ago. When a team led by Byrappa Venkatesh of the Institute of Molecular and Cell Biology in Singapore compared its genome with those of other vertebrates, they found it had changed less from its presumed ancestral form than any other.

C. milii outstrips the coelacanth, the fish that previously held the slow-evolution record.

Such limited change means the elephant shark’s genome is the closest yet to that of the first jawed vertebrate, which lived more than 450 million years ago and gave rise to many modern animals including humans. It makes the elephant shark an important reference point for unlocking how this long-lost ancestor evolved. As well as jaws, the earliest fish pioneered bony skeletons and a sophisticated immune system, but it is not known when or how these features appeared…

(read more: New Scientist)

photo: Kelvin Aitken/V and W/Image Quest Marine

Why the Platypus Will Never Have a Stomach

by Charles Q. Choi

Bizarrely, many species of animals, such as the carp and platypus, lost their stomachs in the evolutionary past, and new research suggests they may never evolve the organs back.

The stomach is the part of the gut where the main part of digestion takes place. Glands in this organ secrete enzymes known as pepsins, which break down proteins, and strong acids that soften food and help the enzymes work. The glands first appeared about 450 million years ago, and they represent an evolutionary innovation found exclusively in jawed creatures with backbones.

Surprisingly, the gastric glands that define the stomach are missing in a number of jawed vertebrates. In 1805, the French zoologist Georges Cuvier discovered that many teleosts, or the largest living group of fish, such as the carp family, lack stomachs. The past 200 years of research suggests that up to 27 percent, speaking conservatively, of all teleost species may lack stomachs. Primitive bony fish such as lungfish and some cartilaginous fish such as chimeras lost the organs as well…

(Read more: Live Science)

photos: Stephan Kraft; Gotehal; NOAA

The spotted ratfish aka spotted chimera, Hydrolagus colliei, can be found off the coast of California to depths of about 3,000 feet. Its common name comes from the white spots that cover its body and its pointed rat-like tail. These fish are chimeras, meaning they have characteristics of bony fishes and sharks, from which they descended millions of years ago.
(via:Monterey Bay Aquarium Research Institute)

The spotted ratfish aka spotted chimera, Hydrolagus colliei, can be found off the coast of California to depths of about 3,000 feet. Its common name comes from the white spots that cover its body and its pointed rat-like tail. These fish are chimeras, meaning they have characteristics of bony fishes and sharks, from which they descended millions of years ago.

(via:Monterey Bay Aquarium Research Institute)

Surprise Finds on Kick’em

While exploring the debris slope of the collapsed side of the underwater volcano Kick’em Jenny near Grenada in the Caribbean, the Nautilus expedition crew had a surprising find of a large cold methane seep and rich biology around it. Here are a few of the amazing creatures we spotted there and more can be found at http://www.nautiluslive.org.

Shovelnose Chimera, swimming sea cucumber, deep sea octopus, unidentified species of Snailfish.

denizensofearth

buggerygrips:

I have a new favourite order of fish: chimaeras.

Chimaeras are perhaps the oldest and most enigmatic groups of fishes alive today. Their closest living relatives are sharks, but their evolutionary lineage branched off from sharks nearly 400 million years ago, and they have remained an isolated group ever since. Like sharks, chimaeras have skeletons composed of cartilage and the males have claspers for internal fertilization of females.

Unlike sharks, male chimaeras 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.

Chimaeras are the only vertebrates to retain traces of a third pair of limbs.

The Ghost Shark

Dive 12, August 13, Northeast U.S. Canyons Expedition 2013

A chimaera swims lazily a couple meters above the seafloor in Lydonia Canyon. Chimeras, sometimes called Ghost Sharks or ratfishes, are a group of cartilaginous fishes, elasmobranchs, along with sharks and rays. Many species, such as this one, are dwellers of the deep ocean.

Video courtesy of NOAA Okeanos Explorer Program.

(via: NOAA)

nemertea

no-more-tea-not-ever:

epistemologicalfallacy:

10 More Cool Sharks You Probably Don’t Hear Much About During Shark Week

So I know that Shark Week is over now, but I couldn’t just stop at 10, so here are 10 more!

Angel Shark (Squatina)
There are 23 different species of angel shark and all live in shallow, warm seas, though some migrate to warmer waters during the summer. Most types grow to a length of 5 ft (1.5 m). They hunt at night in their own territories. Unlike rays, they have sharp teeth for feeding on shelled prey and small fish. They disguise themselves from prey by covering their bodies in sand and often having sandy-colored skin. An angel shark is hard to see as it lies on the seabed. Its body is so flat that it appears no more than a low mound in the sand. Unlike a ray, it uses its tail rather than its large fins to swim. Read more about this shark…(read more)
A Deep-Sea Chimaera 
Chimaeras are most closely related to sharks, although their evolutionary lineage branched off from sharks nearly 400 million years ago, and they have remained an isolated group ever since. Like sharks, chimaeras are cartilaginous and have no real bones. The lateral lines running across this chimaera are mechano-receptors that detect pressure waves (just like ears). The dotted-looking lines on the frontal portion of the face (near the mouth) are ampullae de lorenzini and they detect perturbations in electrical fields generated by living organisms. 
This image was captured at the 'Zona Senja' site near Sulawesi, Indonesia, on August 2, 2010.
Image courtesy of NOAA Okeanos Explorer Program, INDEX-SATAL 2010.

A Deep-Sea Chimaera

Chimaeras are most closely related to sharks, although their evolutionary lineage branched off from sharks nearly 400 million years ago, and they have remained an isolated group ever since. Like sharks, chimaeras are cartilaginous and have no real bones. The lateral lines running across this chimaera are mechano-receptors that detect pressure waves (just like ears). The dotted-looking lines on the frontal portion of the face (near the mouth) are ampullae de lorenzini and they detect perturbations in electrical fields generated by living organisms.

This image was captured at the 'Zona Senja' site near Sulawesi, Indonesia, on August 2, 2010.

Image courtesy of NOAA Okeanos Explorer Program, INDEX-SATAL 2010.