. Bulletin. Natural history. 162 PEABODY MUSEUM BULLETIN 36 protrude as far laterally as the iliac and ischial facets (Fig. 46A and DMSW ). This feature which opens the acetabulum more anteriorly than posteriorly is important in the determination of femoral position (see below). The dorsomedial rim of the head of the pubis is occupied by a rugose, strap-shaped surface which articulates with the pubic process of the ilium. At its posterior terminus the surface faces posteriorly and makes contact with the ischium above the obturator foramen. The anterior half of the strap-shaped surface gra
. Bulletin. Natural history. 162 PEABODY MUSEUM BULLETIN 36 protrude as far laterally as the iliac and ischial facets (Fig. 46A and DMSW ). This feature which opens the acetabulum more anteriorly than posteriorly is important in the determination of femoral position (see below). The dorsomedial rim of the head of the pubis is occupied by a rugose, strap-shaped surface which articulates with the pubic process of the ilium. At its posterior terminus the surface faces posteriorly and makes contact with the ischium above the obturator foramen. The anterior half of the strap-shaped surface gradually expands to a wide terminus which together with the expanded anterior edge of the pubic process of the ilium represents the strongest part of the iliopubic symphysis. Below the head the pubis is constricted to form a short neck. From the neck arises a ventromedially directed pubic plate which is laterally concave (pu p, Fig. 45A). Most of the pubic plate is thin and in no specimen is it completely preserved. The plane of the pubic plate appears to be slightly convolute because its anterior edge arises from the anteromedial surface of the neck whereas the posterior edge arises from the posteromedial surface. The anterodorsal edge of the pubic plate is swollen and rod-like (r pu, Figs. 45A, 46A), a primitive feature found is sphenacodontid and other pelycosaurs. The rod is slightly curved, bending ventrolaterally toward its anterior end. It terminates in a round, flat rugosity which has generally been interpreted (see be- low) as an articular facet for a prepubic bone. Opposing pubic plates meet along a thin symphysis, creating a broad, U-shaped basin which is deepest posteriorly along the puboischial contact. In no pubis is the anterior free edge completely preserved; presumably it was very thin and perhaps extended by cartilage. The posterior half of B. ob f fig. 46. Right side of the pelvis in a cynodont, BMNH , possibly referable to ?Aleodon or ?Scalenodon, in A, la
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