Alligator Skeleton Labeled – Skull, Belly Ribs and Tail

All 30 bones on the diagram

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Front half 18

Skull A long, low skull with a broad snout. The eyes and nostrils sit on top of the head.
Mandible The lower jaw. It hinges at the very back of the skull.
Teeth Cone-shaped, peg-like teeth in both jaws. A worn tooth is replaced by a new one.
Cervical vertebrae The neck vertebrae. Every one of them carries a pair of short ribs.
Cervical ribs Short ribs on the neck vertebrae. They lie back along the neck and never reach the breastbone.
Osteoderms Bony plates set in the skin of the neck and back. They lie under the horny scales.
Thoracic vertebrae The chest vertebrae. Each one carries a pair of long ribs.
Ribs Long ribs that curve round the chest. Most reach the breastbone, which is cartilage.
Scapula The shoulder blade, a flat bone that widens toward its top.
Coracoid A flat bone running from the shoulder joint down to the breastbone.
Interclavicle A flat rod of bone along the midline of the chest. An alligator has no collarbones.
Humerus The upper bone of the front leg, from shoulder to elbow.
Radius One of the two forearm bones. It is straight and a little shorter than the ulna.
Ulna The longer, slightly curved forearm bone. It forms most of the elbow joint.
Carpals The small wrist bones, in two rows.
Metacarpals Five slender bones in the front foot, one for each toe.
Phalanges The toe bones. The last bone of a clawed toe is pointed and sits inside the claw.
Gastralia Slender belly ribs set in the body wall, between the breastbone and the hips.

Rear half 12

Lumbar vertebrae The loin vertebrae, between the chest and the hips. They carry no ribs.
Sacral vertebrae Two stout vertebrae that hold the hip bones.
Caudal vertebrae The tail vertebrae, the longest run of the backbone. They get smaller toward the tip.
Chevron bones V-shaped bones that hang under the tail vertebrae. Blood vessels of the tail run through them.
Ilium The upper hip bone. It is fixed to the two sacral vertebrae.
Ischium The hip bone that points down and back. It meets its partner in the midline.
Pubis The hip bone that points forward and down. It takes no part in the hip socket.
Femur The thigh bone, from hip to knee.
Tibia The stouter of the two bones of the lower leg. Its top forms most of the knee.
Fibula The long, slender bone of the lower leg, beside the tibia.
Tarsals The ankle bones. One of them, the calcaneum, sticks out behind as a heel.
Metatarsals Four long bones of the hind foot. A fifth is only a small stub.

How this list was compiled: Every bone name and detail line was checked on 2026-10-01, for facts only and with nothing copied: (1) A. M. Reese, The Alligator and Its Allies, 1915 (public domain), the chapter on the skeleton, https://archive.org/details/alligatoritsalli00rees; (2) C. C. Mook, Notes on the Postcranial Skeleton in the Crocodilia, a museum bulletin of 1921 (public domain), https://archive.org/details/bulletin-american-museum-natural-history-44-067-100; (3) Wikipedia, Crocodilia; (4) Wikipedia, Gastralia; (5) Wikipedia, Haemal arch. A bone name that only one source gives is left out of the parts. Licence: own work

The drawing: Drawn for this site on 2026-10-01 from plain shapes. Own original schematic drawing; nothing traced or copied. Licence: own work

How it works

Here is an alligator skeleton labeled from the left side, drawn inside the outline of an American alligator walking with its belly off the ground. The front half and the rear half are shown one at a time.

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Two halves of one alligator

The front half comes first, names showing: the skull and teeth, the neck with its short ribs, the chest, the shoulder and the front leg. The rear half has the loins, the hips, the hind leg and the tail. Tap a name for a line about that bone. Quiz me hides the names.

What sets this reptile apart

Every neck vertebra carries a rib. Slender belly ribs lie in the body wall behind the breastbone. Only two vertebrae hold the hips. V-shaped chevron bones hang under the tail, and bony plates sit in the skin of the back.

The pubis points forward and the ischium points back; the ilium sits on top, against the backbone.
Ribs that reach the breastbone belong to chest vertebrae. Neck ribs are short and stop well above it.

Questions and answers

How many vertebrae does an alligator have?

A 1915 anatomy of the alligator counts 9 in the neck, 10 in the chest, 5 in the loins, 2 at the hips and about 39 in the tail, some 65 in all. The tail count varies from one animal to the next.

Do alligators have ribs on their belly?

Yes. Slender bones called gastralia, or abdominal ribs, lie in the belly wall between the breastbone and the hips. They are not joined to the backbone, so they are not ribs in the usual sense.

What are osteoderms on an alligator?

Bony plates that lie in the skin, under the horny scales. On an alligator they form a small group behind the head and rows down the back. Each plate is flat underneath and has a ridge on top.

Is an alligator skeleton the same as a crocodile skeleton?

Bone for bone, very nearly. The clearest difference is the head: an alligator has a broad, U-shaped snout, and a crocodile's is usually narrower and V-shaped.