More Anatomy

Like octopods and cuttlefishes, giant squid have eight arms. But they use their two much longer feeding tentacles to seize prey. The tentacles have powerful suckers at the ends. More about the giant...
The elongated body, characteristic long and narrow snout, and small teeth make the slender snipe eel ( Nemichthys scolopaceus ) easily identifiable in this X-ray image. Snipe eels live at great...
Sperm whales have conical teeth on their long, narrow, lower jaw. The teeth fit neatly into sockets in the upper jaw, which has no teeth. This arrangement is a perfect adaptation for slurping up soft...
Scientists in the Division of Fishes at the Smithsonian's National Museum of Natural History use X-ray imaging to study the complex bone structure and diversity of fish. This image gallery showcases...
Inside the giant squid's sharp beak is a tongue-like organ called the radula (shown in yellow). Covered with rows of tiny teeth, it rams bite size pieces of food down the squid's throat. The pieces...
These are fossil remains of archaeocetes, ancient whales, from the Paracas Formation of Peru's Pisco Basin . Smithsonian paleobiologist Nicholas D. Pyenson and a team of scientists discovered the...
The feathery strands at the back of this nudibranch’s ( Chromodoris willani ) body are no mere adornment: they’re its gills! Nudibranchs, shell-less snails or sea slugs, are named for these tufted...
The robust oval, spine covered body of a long-spined porcupine fish ( Diodon holocanthus ) is revealed in this X-ray image. To ward off predators, a porcupinefish inflates its body by pumping water...
Many sperm whales stranded on beaches or caught by whalers exhibit telltale circular scars like these. Only one thing could have made them: the strong suckers that line the giant squid’s eight arms...
A mass of white muscle the size of a softball surrounds the dark brown beak of a giant squid. Learn more about this animal's oversized anatomy in our Giant Squid section .
Comb jellies (such as this Bolinopsis species) are named for their combs: the rows of cilia lining their bodies that propel them through the ocean. Read more about jellyfish and comb jellies .
An X-ray image of a Monterey skate ( Raja montereyensis ) reveals a spine that extends like a tail out from the pelvic fin. The skeletons of skates, rays, chimaeras, and sharks are made of cartilage...
The Palauan primitive cave eel ( Protanguilla palau ) has an evolutionary history that dates back some 200 million years . Because of this and the fact that it has retained some primitive features,...
Tropical hatchetfish ( Argyropelecus lychnus ), like the one shown in this X-ray photograph, live in the dark depths of the ocean ; this specimen was collected at about 2,789 feet (850 meters) in the...
In the X-ray image of this Viper Moray Eel ( Enchelynassa canina ), note the second set of jaws in the “throat”; these are the gill arches, which are present in all fish. Gill arches support the...
An X-ray image of grooved razorfish ( Centriscus scutatus ). Razorfish are encased in thin, transparent bony plates attached to their spines, which you can see in the X-ray. Also known as shrimpfish...
A right whale opens its mouth wide, revealing huge plates of baleen hanging from its upper jaw. There are between 200 and 270 baleen plates on each side of a right whale's upper jaw. They work like a...
This common octopus ( Octopus vulgaris ) doesn't have a jetpack to help him zoom through the water, but he's got something pretty close: a siphon that shoots water. (It's the little orange/yellow cup...
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