What is the significance of the astragalus and involucrum to the study of whale evolution? Scientists find missing link between the whale and its closest relative, the hippo. 4), has a hinge joint, called a trochlea, where it articulates with the tibia (shin bone). This persisted as a long-standing theory, until 2001, when fossils for the ankles of early whales were discovered and it turned out these whales possessed a modified form of the talus bone, known as the astragalus were recovered. Scientists discovered that whales had an ankle bone called astragalus which shows that they share a common ancestor with the artiodactyls. 4), has a hinge joint, called a trochlea, where it articulates with the tibia (shin bone). In raoellids and other artiodactyls (and in extinct cetaceans), the astragalus has a second trochlea, which is located on the opposite end of the a. astragalus toDPA (ankle bone) is the synapomorphy that dis-tinguishes artiodactyls from other ungulates. In all mammals, this bone, the astragalus or talus (Fig. This whole complex of characteristics unites early whales with artiodactyls, or even-toed hoofed mammals. Late Eocene basilosaurid whales have greatly simplified ankle bones, and later fossil and living whales From the ear bones to the ankle bones, whales belong with the hippos and other artiodactyls. It was an animal about the size of a dog, [clarification needed] which lived in or near the water and ate fish and small animals. A 43 million-year-old fossil whale from Peru marks the first record of whales in the Western Hemisphere. The basilosaurid astragalus still has a pulley and a hooked knob pointing up towards the leg bones as in artiodactyls, while other bones in the ankle and foot are fused. Ankle bones of mesonychians, primitive fossil whales, and early Eocene artiodactyls; astragali above, calcanei below. astragalus bone; (2) a notch in the cuboid for insertion of the calcaneum; and (3) a large convex fibular facet on the calcaneum. Fossil comparison. Pakicetus is an extinct genus of amphibious cetacean of the family Pakicetidae, which was endemic to Pakistan during the Eocene, about 56 to 41 million years ago. ankle. In all mammals, this bone, the astragalus or talus (Fig. This shows that whales evolved from land mammals. As people began finding older fossils of whale ancestors a surprising similarity in the astragalus bone (an ankle bone) was found that connected whales' ancestry with artiodactyls, or even-hooved animals like camels, deer, pigs, cows, sheep, etc. The astragalus, unlike other tali, were shaped like a … The term “double pulley” refers to the presence of two articular surfaces – one with the tibia (leg bone), the other with the os navicular (another foot bone). Question: He Hypothesis That Whales Are Most Closely Related To Hippos Is Based On All Of The Following Evidence EXCEPT: Whales Have An Ankle Bone That Is Also Present In All Artiodactyls And Is A Synapomorphy For This Phylogenetic Group. In 2001, two publications reported on the morphology of whale astragalus bones (ankle bones), which have pulley-shaped grooves that improve flexion and are adaptations for high speed running; extant Cetaceans lack these bones entirely as they lack hindlimbs. b. evidence: whales lack dou-ble pulley astragalus (DPA).