than broad. The C3 has a narrow spinous process and is mostly columnar, but the tailward side is broader. The C4 is more columnar. The C7 and C8 are columnar and taper off tailward, and the neural canal where the central nervous system runs through is still present. In life, Ambulocetus possibly had upwards of 20 tail vertebrae like some mesonychians. If correct, then Ambulocetus would have had a lot fewer and a lot longer tail vertebrae than modern cetaceans. Limbs and girdles Unlike modern cetaceans, Ambulocetus had functional legs which could support the animal's bodyweight on land. The holotype has a robust radius and ulna (the forearm bones). The forearm measures in length. The head of the radius is somewhat triangular, which probably means the forearm was locked in a semi-pronated position (the palms were orientated towards the ground). The olecranon, which formed part of the elbow joint, makes up about a third of the ulna's length and is inclined tailwards, which would have allowed the triceps to more forcefully flex the elbow. The wrist bones indicate a strong flexor carpi ulnaris muscle for wrist flexion. The hand had five widely spaced digits. The first metacarpal (which is in the thumb) is long, the second , the third , the fourth , and the fifth . Like modern beaked whales, the thumb is short and slender. The ilium of the hip of Ambulocetus, like remingtonocetids, features deep depressions to support the rectus femoris and the gluteal muscles. Unlike terrestrial mammals and protocetids, the ischium is expanded dorsolaterally (from left to right, and upwards), which would have increased lever arm for thigh and leg retractor muscles when extended, such as while swimming. This would have also increased the surface area of the gemelli muscles (hip rotators which stabilise the hip) and the tail muscles. The widening of the ischium may have also given Ambulocetus a more streamlined and hydrodynamic body. Ambulocetus had a pubic symphysis connecting the two pubic bones at the base of the pelvis together, which indicates the animal could support its own weight on land. The modern cetacean pubis bone lacks this and only functions to anchor abdominal and urogenital muscles. The leg proportions of Ambulocetus are similar to otters and seals, and American mammalogist Alfred Brazier Howell predicted similar proportions for a transitional cetacean in 1930. The femur measures , a length similar to the presumably