Large scale replicas of ornithischian and saurischian dinosaur hip fossils. This sculpture was drawn with a 3D pen and finished to perfection. Made with lightweight and durable material to make display an ease.

This was created for an educational display at a museum. Compare and contrast the two different types of hip evolution and talk about the different types of dinosaurs that used them.

Ornithischian dinosaurs were described as having a bird hipped pelvic structure. Saurischian dinosaurs were described as having lizard hipped pelvic structure.

Here is a bit of information that the listing editor used to understand the display:

"One important dinosaurian synapomorphy is the perforate acetabulum, simply a "hip bone" (actually three connected bones, together called the pelvis) with a hole in the center where the head of the femur ("thigh bone") sits. This construction of the hip joint makes an erect stance (hindlimbs located directly beneath the body) necessary — like most mammals, but unlike other reptiles which have a less erect and more sprawling posture. Dinosaurs are unique among all tetrapods in having this perforate acetabulum.

A more in-depth classification of dinosaurs uses modifications to this basic hip structure, and many other characters, to help differentiate between separate groups of dinosaurs, and hence reveal to us dinosaurian diversity.

The Dinosauria contains two major groups of dinosaurs: the Ornithischia, or "bird-hipped" dinosaurs, and the Saurischia, or "lizard-hipped" dinosaurs. The most prominent visible difference between the two types of hip is the orientation of the pubis, shown in white in the picture above. In saurischian dinosaurs, this bone points toward the front of the animal, and flares into a keel at the forward end. Ornithischians have a reversed pubis, which points toward the tail and lies alongside and parallel to the ischium. Additionally, some ornithischians have a projection at the forward end of the pubis.

The first recognition of the two groups was made by H.G. Seeley in 1888. The etymology behind the two names ("bird-hipped" vs. "lizard-hipped") is rather confusing, since some saurischians had bird-like hips, and ornithischians' hips were somewhat birdlike due to convergent evolution, not due to shared ancestry. Birds are apparently descended from saurischian dinosaurs, but have a reversed pubis like ornithischians do. Some close relatives of birds within saurischians have this same feature, too, so the ornithischian-saurischian dichotomy is not so simple. The names "Ornithischia" and "Saurischia" are used to refer to the common ancestry of their respective members. The names don't necessarily have to mean anything. They are just names, that's all." (https://ucmp.berkeley.edu/diapsids/dinomm.html)