the ilium, the ischium and the pubis meet at the acetabulum.
the ilium, the ischium and the pubis meet at the acetabulum.
where do the ilium the ischium and the pubis meet?
acetabulum
the pelvis (hip) shared quite a few similarities with other dinosauriforms not otherwise present in earlier archosauriforms. the ilium (upper blade of the hip) was similar to that of "herrerasaurus" in general shape. the pubis (front lower blade of the hip) was longer than the ischium (rear lower blade of the hip), like dinosauriforms. however, the ischium was also enlarged relative to earlier archosauriforms, as it was longer than the main portion of the ilium. furthermore, the ischium's contact with the pubis is less extensive than in early archosauriforms and it fails to contact the ilium along the boundary of the pubis, as with silesaurids and saurischian dinosaurs. this "gap" between the ilium and ischium along the edge of the pubis becomes more developed in dinosaurs, where it becomes and open cavity that fills up the entire acetabulum (hip socket). however, this had not yet evolved in "marasuchus", which retains a bony inner wall of the acetablum. moreover, the edge of the ischium in "marasuchus" retains contact between the ilium and pubis, unlike dinosaurs. nevertheless, a depression present in that area may be a predecessor to the more advanced condition in dinosaurs.
marasuchus
the shoulder region was very incomplete, preserving fan-shaped scapulae (shoulder blades) similar to that of tanystropheids, as well as fragments of a coracoid and humerus. the hip area was somewhat better preserved and more distinctive in fuyuansaurus. the three bones of the hip (ilium, pubis, and ischium) were separated from each other by short gaps in the skeleton, though the ilium was likely connected to the other bones in life. unusually, the pubis and ischium were separated by a long, straight gap. this is in contrast to typical tanystropheids, which have the pubis and ischium curve towards each other, often contacting each other at the bottom to enclose a hole termed the thyroid fenestra. a portion of the square-shaped femoral head is also preserved.
fuyuansaurus