Search results
Results From The WOW.Com Content Network
In contrast, bony fishes have a single outer bony gill covering called an operculum. Most sharks and rays have five pairs of gill slits, but a few species have 6 or 7 pairs. Shark gill slits lie in a row behind the head. The anterior edge of a gill slit is motile, moving outward to allow water to exit, but closing to prevent reverse flow.
Bonaparte's original definition of Elasmobranchii was effectively identical to modern Chondrichthyes, and was based around gill architecture shared by all 3 living major cartilaginous fish groups. During the 20th century it became standard to exclude chimaeras from Elasmobranchii; along with including many fossil chondrichthyans within the group.
Batomorphi is a clade of cartilaginous fishes, commonly known as rays, this taxon is also known as the superorder Batoidea, but the 5th edition of Fishes of the World classifies it as the division Batomorphi. [2] They and their close relatives, the sharks, compose the subclass Elasmobranchii. Rays are the largest group of cartilaginous fishes ...
These sharks have pointed snouts, spindle-shaped bodies, and large gill openings. The first dorsal fin is large, high, stiff and angular or somewhat rounded. The second dorsal and anal fins are minute. The caudal peduncle has a couple of less distinct keels. The teeth are gigantic.
In elasmobranchs (sharks and rays) the spiracle bears a small pseudobranch that resembles a gill in structure, but only receives blood already oxygenated by the true gills. [7] The function of the pseudobranch is unknown, but it is believed that it supplies highly oxygenated blood to the optic choroid and retina and may have baroreceptor ...
The gills are composed of comb-like filaments, the gill lamellae, which help increase their surface area for oxygen exchange. [5] When a fish breathes, it draws in a mouthful of water at regular intervals. Then it draws the sides of its throat together, forcing the water through the gill openings, so it passes over the gills to the outside.
In 2018, there were only 66 confirmed unprovoked shark attacks on humans, which is the lowest it's been in years. It's even more rare for the attack to be fatal — last year, the U.S. experienced ...
Ground sharks, like this blacknose shark, have a nictitating membrane which can be drawn over the eye to protect it.. Carcharhiniformes / k ɑːr k ə ˈ r aɪ n ɪ f ɔːr m iː z /, commonly known as ground sharks, are the largest order of sharks, with over 270 species.