. Breviora. 1971 LAGERPETON AND LAGOSUCHUS 7 the iliac rim. The acetabular construction plus the nature of the femoral head indicate rather surely that the femur moved in a fore-and-aft plane close to the body. The ilium (Fig. 3) is of peculiar structure. Above the acetabulum it constricts to a rela- tively narrow neck. Here there projects anterolaterally a short but stout, blunt-ended process of a sort otherwise unknown to me; it is possible that it afforded an origin for an iliofemoralis externus muscle as in the case of a somewhat similar process in some ornithischians (cf. Romer, 1927) and
. Breviora. 1971 LAGERPETON AND LAGOSUCHUS 7 the iliac rim. The acetabular construction plus the nature of the femoral head indicate rather surely that the femur moved in a fore-and-aft plane close to the body. The ilium (Fig. 3) is of peculiar structure. Above the acetabulum it constricts to a rela- tively narrow neck. Here there projects anterolaterally a short but stout, blunt-ended process of a sort otherwise unknown to me; it is possible that it afforded an origin for an iliofemoralis externus muscle as in the case of a somewhat similar process in some ornithischians (cf. Romer, 1927) and Poposaurus (Colbert,. Figure 3. Right ilium and head of femur of Lagosiichiis: external process on ilium restored from left side. From a specimen in the Institute Lillo. X 4/3. 1961). Above the "neck," the ihum expands to form a short blade. In all "normal" thecodonts the iliac blade is a simple single vertical structure; here, however, there lies, internal to the normal external blade, a broad trough, comparable to that seen in ophia- codonts, presumably for accommodation of dorsal axial muscles. Shallow posteriorly, this trough deepens and broadens anteriorly. Medial to this trough is a second iliac blade, tilted somewhat medially, to the inner surface of which the sacral ribs pre- sumably articulated. Lateral and medial blades join anteriorly, closing the dorsal trough at this end. I know of such an iliac "trough" structure in only one other archosaur. In Hesperosuchus, Colbert (1952) found in the pelvic region an element which should have been an ihum but which, because of its pecuHar nature, he concluded could not be that element. Its main peculiarity is its possession of a dorsal "trough" comparable to that of Lagositchus. Parts of pubis and ischium are present in this specimen. It is. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearan
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