Skeleton Diagram of a Frog Without Labels

All 21 bones on the diagram

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Front half 13

Premaxilla A small bone at the very front of the upper jaw. There are two. They carry teeth.
Maxilla The long bone of the upper jaw, one on each side. It carries a row of small teeth; the lower jaw has none.
Frontoparietal One of two long, flat bones that roof the braincase. They lie side by side along the middle of the skull.
Atlas The first vertebra, which meets the skull. Unlike the others, it has no side processes.
Vertebrae A frog has only nine vertebrae. The second to the eighth each carry a pair of side processes, and there are no ribs.
Sacral vertebra The ninth vertebra, with strong side processes. They slant backward and hold the front ends of the two ilia.
Suprascapula A flat plate at the top of the shoulder girdle. It is wider at its free edge and partly cartilage.
Scapula The shoulder blade, running down from the suprascapula. It ends at the joint that holds the head of the humerus.
Humerus The bone of the upper arm. Its rounded head fits the shoulder girdle.
Radio-ulna The frog's forearm is one bone: the radius and ulna joined together.
Carpals The small bones of the wrist, in two rows.
Metacarpals The bones of the palm. A frog has four fingers, and only a hidden stump in place of a thumb.
Phalanges The bones of the fingers and toes. Four fingers on each hand and five toes on each foot.

Rear half 8

Urostyle A long rod of bone that runs back from the ninth vertebra. It reaches the point where the two ilia meet. It is almost as long as the nine vertebrae together.
Ilium One of two long hip bones. Each runs back from the ninth vertebra, and the two meet at the hip joints, in the shape of a V.
Ischium The rear part of the hip girdle. Two plates joined flat against each other behind the hip joints.
Femur The thigh bone, from the hip to the knee. It is long and slightly S-shaped.
Tibio-fibula The frog's shank is one bone: the tibia and fibula joined together. A groove at each end shows where they met.
Astragalus The inner of the two long ankle bones. They lie side by side and add one more long section to the leg.
Calcaneum The outer of the two long ankle bones, beside the astragalus.
Metatarsals The five long bones of the foot. They lie between the ankle bones and the toes.

How this list was compiled: Every bone name and detail line was checked on 2026-09-30, for facts only and with nothing copied: (1) S. J. Holmes, The Biology of the Frog, chapter XIII, The Skeleton, read in the Internet Archive scan at https://archive.org/details/biologyoffrog01holm; (2) A. Ecker, The Anatomy of the Frog, translated by G. Haslam, 1889, The Bones and Joints, https://archive.org/details/anatomyoffrog00ecke; (3) Wikipedia, Frog. A name that only one source gives is left out. Licence: own work

The drawing: Drawn for this site on 2026-09-30 from plain shapes. Own original schematic drawing; nothing traced or copied. Licence: own work

How it works

A skeleton diagram of a frog without labels: the skeleton from above, head to the left, inside the outline of the sitting animal. Twenty-one bones to name: twenty have a line, and one is wide enough to write on.

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The word list, from skull to toes

Skull: premaxilla, maxilla, frontoparietal. Spine: atlas, vertebrae, sacral vertebra, urostyle. Shoulder and arm: suprascapula, scapula, humerus, radio-ulna, carpals, metacarpals, phalanges. Hip and leg: ilium, ischium, femur, tibio-fibula, astragalus, calcaneum, metatarsals.

One line for each pair of bones

Both sides of the frog are drawn, and a bone has its line on one side only. The humerus and radio-ulna are marked on one arm, the wrist and hand bones on the other. The femur, tibio-fibula and metatarsals are marked on one leg, the two ankle bones on the other.

The bone with no line is the suprascapula, the broad plate beside the spine. The short bone between it and the arm is the scapula.
Three lines end on one hand: the wrist cluster is the carpals, the slender bones next the metacarpals, the last small bones the phalanges.
The two dashed rings on the head show where the eyes sit. They are not bones and take no name.

Questions and answers

What are the bones of a frog skeleton to label?

Twenty-one on this sheet: three in the skull, four in the spine, seven in the shoulder and arm, seven in the hip and leg. The nasal bones and the back of the skull are drawn but have no line.

What is the frontoparietal bone of a frog?

Two skull bones in one: a frontal and a parietal, separate while the skull is forming and joined into a single bone later. The pair forms most of the roof of the skull.

Which ankle bone is the astragalus and which is the calcaneum?

Two lines on the hind leg at the foot of the sheet end on a pair of thin bones. The one nearer the body is the astragalus, the inner bone. The one on the outside of the leg is the calcaneum.

Is this the dorsal view of the frog skeleton?

Yes. The skeleton is seen from above, with the back toward you. The parts of the underside, the clavicle, coracoid, sternum and pubis, are hidden in this view and are not on the sheet.

Which bone is the ilium on a frog skeleton?

The long bar on each side of the thin rod in the rear half. The rod between the two bars is the urostyle, and the rounded plate where the bars end, behind the hip joints, is the ischium.