Although no special study was made of the skeleton, certain conspicuous variations are discussed here.

There are a few pronounced differences between the pelvis of Tympanuchus and that of Pedioecetes. Whereas in the former the thick lateral iliac process has a pronounced overhang with the ventral edge lateral to the ischium (Fig. 1), in Pedioecetes there is no overhang at all and the edge of this process is much thinner. The ischium in Pedioecetes is wider (in dorsoventral extent), especially posteriorly, than in Tympanuchus. In Tympanuchus the posteroventral margin of the ischium is rounded and is free from the pubis, whereas in Pedioecetes it is pointed and fused with the pubis.

In Tympanuchus cupido (both subspecies) the lateral iliac process extends farther ventrally than in T. pallidicinctus, approaching or extending ventral to the level of the pubis in the former species; also the edge of this process is thicker in T. cupido.

All specimens studied have a single synsacro-thoracic vertebra. The number of combined synsacro-thoraco-lumbar and synsacro-lumbar vertebrae is eight in each specimen of Tympanuchus and in one specimen of Pedioecetes phasianellus jamesi and is seven in three specimens of the latter. In most specimens of Tympanuchus there are three synsacro-thoraco-lumbar and five synsacro-lumbar vertebrae, although in two specimens (T. pallidicinctus) there are four of each group; in one of these latter two specimens the parapophysis on one side of the fourth synsacro-thoraco-lumbar vertebra is small. The first (of five) synsacro-lumbar vertebra has a rudimentary parapophysis on one side in one specimen of Tympanuchus and on both sides in another specimen. One specimen of Pedioecetes phasianellus jamesi has five synsacro-lumbar vertebrae and the others have four; all have three synsacro-thoraco-lumbar vertebrae.