To allow the bones to "flex" a bit when the babies head is coming through the birth canal. The head returns to it's normal shape in a few hours to days. Later, the bones fuse, of course.
Fetal pig hooves are typically fused in the same manner as adult pigs. Split hooves, like those found in cattle and deer, are not present in pigs.
The ossa coxae (containing the ililum, ishium, and pubic bones) are not fused in a fetal skeleton like in an adult human.
the calvarium of the adult scull is fused, in the fetus the bones making up the skull are not fused (not joined together), also the're actually quiet a lot of space around the bones - called fontanelles or "soft spots" on a baby's head that you can feel on the back of the head in many babies until 6-9 months or so and on the front of many babies until 15-18 months or so.
In the fetal skeleton, the ossa coxae (hip bones) are not fully fused, and they consist of three separate bones: ilium, ischium, and pubis. In the adult skeleton, these three bones have fused together to form a single hip bone. Additionally, the acetabulum, the socket where the femur connects to the hip bone, is not fully developed in the fetal skeleton but is complete in the adult skeleton.
Many joints are not fused a birth. These include the skull as well. This allows for rapid growth and maturation of the boney skeleton.
nothing at all
Two characteristics of the fetal skeleton skull that differ from the adult skeleton are the presence of fontanelles (soft spots) in the fetal skull that allow for flexibility during childbirth, and the incomplete fusion of cranial bones in the fetus compared to the fully fused bones in adults.
A fetal sternum is less ossified and consists of segments of cartilage called sternal bars, which gradually ossify and fuse into a single bone known as the sternum in adults. The fetal sternum also has more flexible and elastic characteristics to allow for growth and movement during development.
The sacrum is the posterior portion of the pelvis. The pelvis is similar to a shallow bowl and the sacrum is one of the three bones that make up the bowl. The sacrum is made of 5 fused vertebra. This lack of the sacrum is called Sacral Agenesis and is a birth defect. The improper development of the sacrum leads to other defects that include abnormalities of the urinary and lower digestive system as well as defects to the legs such as fused legs. The suspected cause of Sacral Agenesis is believed to be Folic Acid deficiency during fetal development.
The quality of being fusible.
An MRI scan will tell you.