In the femur the head is rather short, the neck thick and but slightly constricted. The internal trochanterial surface is flat, or slightly concave. The transverse section of the shaft is usually oval, but it is variable. The linea aspera is broken and not well marked. The popliteal depression is short and deep; the two tuberosities are usually separated, and the inner one placed on the inner margin of the popliteal depression. The distal extremity is much expanded; the inter-condylar fossa nearly as deep on the outer as on the inner side. From the femur of Euryapteryx it may be distinguished by the shorter and thicker head, and by the internal trochanterial surface being flatter.
The length of the tibia is between 7 ¾ and 11 times that of the width of the shaft in the middle. The shaft is usually straight, but sometimes it is considerably curved inward; its antero-outer surface is usually convex (flat in P. immanis). The distal extremity is much expanded inward, and the distal width is almost always more than 3.3in. The extensor bridge and its tubercle are directed at the outer condyle.
The length of the metatarsus is from 3 to 4 ¼ times that of its mid-width, which is always greater than that of the tibia or femur. The proximal articular surface has the inner margin
sinuated. The proximal interosseous foramina either open separately on the anterior surface, or into a shallow depression situated above the insertion of the tibialis anticus, and there is no rough tubercle on the inner margin of this depression. The trochleæ are much expanded, and the third projects forward more than in any other species.
The differences between the species depend more on the thickness than on the length of the leg-bones.