"Ribs long and curved, with capitulum and tuberculum, cartilaginous within.
"Anterior limb slender, humerus with distinct keel; radius and ulna separate; toes four or five.
"Posterior limb with well-developed femur; tibia and fibula shorter, separate; toes five, somewhat long and slender.
"Pelvis large, composed of ilium and ischium."
Interclavicle and numerous scutellæ are present. Upper surface protected with imbricated horny scales. In front two rows of horny tubercles and plates, with epaulettes composed of bristle-like fibers projecting from the skin.
The animal possibly fed on insects, as is indicated by the coprolitic matter associated with the remains of the species.
The following measurements are given by Dawson for the largest individual discovered:
| Length of head | about cm. | 2 |
| Length of neck | " " | 1.3 |
| Length of trunk | " " | 7 |
| Length of posterior limb to heel | cm. | 3 |
| Length of mandible | " | 1.8 |
| Teeth, 5 in 1 mm. | ||
| Length of rib | cm. | 1.3 |
| Length of humerus | " | 1.4 |
| Length of femur | " | 1.8 |
| Length of tibia | " | 1.2 |
| Length of body of vertebra | mm. | 2.5 |
Hylonomus latidens Dawson.