#chimaeras

[antiqueanimals]

Reptiles, Amphibia, Fishes and Lower Chordata. Written by Richard Lydekker and others. Published in 1912.

Internet Archive

[doitexchange]

'Ghost sharks' grow forehead teeth to help them have sex, study suggests

Male "ghost sharks"—eerie deep-sea fish known as chimaeras that are related to sharks and rays—have a strange rod jutting from their forehea

[i-am-a-giant-siphonophore]

chimaeras!

chimaeras are relatives of the shark and are often called ‘ghost sharks’!

there are 50 different chimaera species alive today

there are very few coastal species of chimaera as they usually reside at depths below 500m!

chimaeras are opportunistic feeders that consume a wide variety of invertebrates

these fish can grow anywhere from 60cm to 120cm in length

unlike sharks, chimaeras only have one gill opening on each side :]

[crackengolds]

People think Antares keeps Victoria subdued.

Which he does. She’s got a drive to build and cause a little chaos that the army cannot handle.

However

Sometimes someone says something incorrect about fish.

[unofficial-sean]

Here is a taxonomy bracket that I use to help me with shark species categorization and relatedness. The top image is specific to sharks and features images as well as brief descriptions and the criteria for each branch. The bottom image is expanded to include holocephalans (chimaeriformes), as well as skates and rays. Basically, everything under “chondricthyes”

[monophyletic-group-of-the-week]

Taxon Tuesday #5: Chondrichthyes

Chondrichthyes is the class that holds cartilaginous fishes (sharks, rays, skates, etc.)  They’ve been around for well over 400 million years.  Oldies but goodies am I right?  Some of their distinguishing features are: skeletons made mostly of cartilage; skin covered in tooth-like placoid scales or denticles; teeth that are regularly shed and replaced; a piece of anatomy in males called a “pelvic clasper”, used for courtship and mating (I’m not looking that up for you sorry ✌)

These uncalcified friends are found in the clade Gnathostomata (jaw-having vertebrates).  Their cousins are Placoderms (extinct armored fishies) and Euteleostomes (bony boys - includes bony fishies and tetrapods, or land-walking friends).

Chondrichthyes itself is divided into two major subclasses.  The first is Holocephali, which holds the single order Chimaeriformes...the order of the chimaeras.  The second is Elasmobranchii, which holds 3 superorders, each of which hold 4 orders.  Taxonomy is rarely this well-balanced.  There are a lot of names, so I’ve drawn them in the picture below, with subtitles explaining what they contain.  You will have to click on it to view it fully, because it’s extremely crowded :(  Someday I will learn how to make these trees correctly.

Sources used:

https://en.wikipedia.org/wiki/Chondrichthyes

https://www.ucl.ac.uk/museums-static/obl4he/vertebratediversity/chondrichthyes.html

[uncharismatic-fauna]

The Remarkable Spotted Ratfish

requested by @an-earwig

Spotted Ratfish

    The spotted ratfish (Hydrolagus colliei) is a small fish from the Pacific Ocean along the North American coast. These fish are a member of the Chimera group meaning that they have cartilage in the place of bones, and they are closely related to both rays and sharks. Because of its unique morphology, the spotted ratfish is fairly easy to identify. In an uncommon reversal of sexual dimorphism, females are larger than the males at 97 cm long; approximately a half of this length is composed of the fish’s long, pointed tail. In contrast, the head is flat, bulbous, and sports a duckbill-like snout. Like sharks and rays, these fish are smooth and scale-less, and usually iridescent silvery-bronze with speckled white dots.    

    Because of their thinner tail, spotted ratfish are relatively poor swimmers, so to defend themselves they use a poisonous spine on their dorsal fin. When they can, sharks, bass, rockfish, halibut, and marine mammals all readily consume spotted ratfish. In turn, H. colliei hunt slowly on the sandy ocean floor at night, using a combination of chemical and electrical receptors to find their prey; primarily crunchy animals like crustaceans, mollusks, and polychaete worms, as well as small fish. Interestingly, spotted ratfish share a trait with bony fish: the upper jaw is fused with the skull. This gives spotted ratfish a large biting force, which they use in combination with their upper two pairs of teeth to break the shells of of their prey. 

H. colliei, like their prey, are almost exclusively benthic fish, and prefer muddy or rocky habitats. They also tend to stay in cool, shallow waters around 7-9 °C and up to 1000m deep, moving steadily deeper as their range moves south. While populations are found as far as the southern United States, they are most commonly found in the Pacific Northwest, where they are occasionally attracted to shallower waters by dock or boat lights. They also move with the seasons; swimming in more shallow waters in the cooler spring and fall, and deeper again in the summer and winter.

Alongside some sharks, spotted ratfish reproduce by laying eggs in the spring or fall. These fish have a unique copulation process that lasts up to 30 hours, in which the male uses a club-like appendage on the head called a cephalic clasper to grip the female’s pectoral fin. After mating, the female releases one or two eggs over a period of several days. The eggs are attached to the ocean floor by thin tendrils, and the female will guard them for a few weeks to ensure they are not eaten by predators or mistaken by inanimate objects by unsuspecting divers. The eggs themselves take over a year to hatch, and young emerge already 14 cm long and fully independent. 

Conservation Status: The spotted ratfish is currently listed as Least Concern by the International Union for the Conservation of Nature. It is occasionally caught as by-catch in the Pacific Northwest, but it is not harvested for food or materials.

[rjzimmerman]

Animals You Didn’t Know Were Related to Sharks - Ocean Conservancy

Meet the shark’s closest cousins

Excerpt from this Ocean Conservancy story:

Sharks are one of the most iconic animals in the sea—how many other animals can you identify simply by their fins? Sharks may get a lot of time in the spotlight, but these top predators are just one part of a diverse group of cartilaginous fishes in class Chondrichthyes.

Rays.

These are stingrays. © AARON GOULDING

Skates.

Skates are technically a type of ray, and are often confused with stingrays because of their similar body shape. Skates have a shorter, thicker tail and do not have a stinger. They’re also often found in cooler, deeper waters, in contrast with the preferred shallow, tropical habitat of stingrays. © WIKIMEDIA

Sawfish.

You’d be hard-pressed to find one in the wild, as all sawfish species are listed as endangered or critically endangered. Their populations have drastically declined because of habitat loss, hunting for their fins and use in traditional medicines. © SFU

Chimaeras.

The chimaera (not to be confused with the chimera, a mythological Greek lion/goat/snake hybrid) is also known as a ghost shark or rat fish. These strange, ethereal creatures are typically found at depths of more than 1500 feet, so we know very little about them. © NOAA OKEANOS EXPLORER PROGRAM, INDEX-SATAL 2010