As with other pinnipeds, penguins, and cetaceans, most walrus forelimb musculature is associated with the shoulder joint, but odobenids also retain abundant musculature distal to this joint. Schematic of the antebrachial muscles of the cetacean forelimb. A third triceps head, found only in Physeter, probably originated on the humerus, but its precise origin was unclear due to the condition of the specimen (Table 2). Dr. J.G.M. Who is the longest reigning WWE Champion of all time? No gross evidence of a flexor muscle was found in Orcinus. 2), but this structure was not found in other taxa. Hydrodynamic studies of cetacean flippers have focused on Megaptera (Fish and Battle, 1995), which has a highly derived flipper shape, but the hydrodynamic properties of other mysticetes and any odontocetes remain speculative. Because all mammals and reptiles came from the same ancestral species, it is not surprising that the basic skeletal anatomy of mammalian forelimbs is the same. Gray whales make When they hug you to their great chests, you feel their love and care for all creation. The retinacula of artiodactyls bind tendons of the digital extensor muscles at the level of the carpus, and well‐developed palmar and digital annular ligaments bind the digital flexor tendons to the metacarpus and phalanges. Hieronymus for discussions. The basal odontocetes Physeter (Fig. But on the inside there are many similarities among human, bird, and bat forearms. How long was Margaret Thatcher Prime Minister? Unlike other mysticetes examined in this study, the humpback whale (Megaptera) exhibited extremely reduced muscles in which there were few muscle fibers and flattened tendons. All species of dissected Mesoplodon are unique in displaying two triceps heads that take origin from the humerus (caput laterale and caput mediale), retaining the primitive artiodactyl condition. , Geology Dept., Univ. An evolutionary and developmental perspective on the loss of regionalization in the limbs of derived ichthyosaurs. The taxonomic diversity of this database allows for phylogenetic interpretations of the evolution of antebrachial muscles and tendons. How old was queen elizabeth 2 when she became queen? ? What is the function of the forelimb of a whale? The slender rodlike Because pressure is greatest on the leading edge of a hydrofoil, the musculocutaneous nerve may play a crucial role in detecting leading edge forces as the angle of attack (angle of the leading edge of the flipper) is changed. 1; Table 2) was observed in mysticetes and the sperm whale (Physeter). • Humpback whales have between 270 and 400 pairs of baleen plates. Separating the flexor tendons from the surrounding connective tissues are synovial membranes. It is not known when carpus and manus mobility evolved to its current reduced state. The objective of this study was to document soft tissue structures of the cetacean forelimb in a comparative context to test the hypothesis that large‐bodied cetaceans have robust antebrachial muscles (flexors and extensors), and small‐bodied cetaceans have reduced muscle morphology. Cetaceans lack proximal sesamoid bones, so the attachments of the m. interosseus muscle in Physeter would not be expected to be completely congruent with that of terrestrial mammals. These muscles were encased in a thick fascia from which the muscle fibers take origin. Artiodactyls have pronators and supinators that are either reduced or absent, and morphologies show individual variation (Fisher et al., 2007). The m. interossei of digits III–V took origin from the connective tissue overlying the proximal aspect of metacarpals III–V, and inserted on the palmar and craniocaudal margins of the proximal phalanges. The reduced musculature of these taxa decreased flipper thickness, created a greater aspect ratio (the ratio of proximodistal length to craniocaudal width), which would allow in turn allow more efficient generation of lift. The fossil record does indicate two important transitions in the cubital joint that may have soft tissue implications. Moreover, the ulnar nerve along the caudal margin of the flipper lies in a relatively thin layer of connective tissue and may be sensitive to vortices being shed along the trailing edge. Identification of the m. interosseus muscle group in Physeter was based on its location, attachments, and relationship to the digital flexor tendon in each digit. Flexors and extensors of cetaceans may have evolved to act only on the joints of the manus—a pronounced reduction compared with their artiodactyl ancestors. Compared with other aquatic taxa with flippers, it appears that cetaceans have acquired some defining characteristics. Locomotory capabilities in the Early Cretaceous ichthyosaur The human forelimb is the arm and the major bones in the arm are the humerus, ulna, and radius. Terminology. Does pumpkin pie need to be refrigerated? Most of the whales in the North Pacific Ocean have black pectoral flippers, though there ar對e some whales which have white flippers. The surprising ease with which the flipper deformed was probably due to the lack of a thick connective tissue encasing the limb (as in the thick dermal layers of Orcinus and Physeter), and the maintenance of cartilaginous interphalangeal joints (Lee, 1978), which may allow a greater range of mobility. Whales Whales that evolved after Ambulocetus (Kutchicetus, etc.) Along with the m. abductor digiti V, the presence of m. interosseus muscles in Physeter appears to be a primitive character state, and later diverging odontocetes lack these muscles. Mork, Dr. S. Rommel, W.A. The thick blubber helps keep the cold/freezing temperatures of the outside water away from the whales vital organs and can even protect whales against attacks from … The most unusual flipper shape is seen in humpback whales as they have longest flippers of any cetacean. () In human, the hand is used for grasping; it is associated with opposable thumb. Mysticete taxa typically displayed well‐developed antebrachial muscles with organized muscular bellies and thick rounded tendons on both the palmar and dorsal flipper surfaces (Fig. Retention of robust muscles by some taxa may indicate an additional functionality not directly relating to digital flexion and extension and hydrodynamic performance as proposed above. This study dissected a single specimen and cannot address whether this finding is a common morphology. The wrist and digits of cetaceans also lack mobility, but some balaenopterid mysticetes may be able to slightly flex the digits. Enter your email address below and we will send you your username, If the address matches an existing account you will receive an email with instructions to retrieve your username, I have read and accept the Wiley Online Library Terms and Conditions of Use, The fossil record and evolutionary relationships of the genus, Investigations on the osteology and the functional morphology of the flipper of whales and dolphins (Cetacea), The role of phylogenetic analysis in the inference of unpreserved attributes of extinct taxa, The comparative myology of the forelimb of the hippopotamus, pig, and tapir, Evolution of digit reduction and hyperphalangy in the cetacean manus, The sirenian shoulder and forelimb‐a study of variation and function, Anatomy of the current and potential blood sampling sites in the Florida manatee (, Observations on underwater locomotion and flipper movement of the humpback whale, Functional anatomy of the hands of fur seals and sea lions, Structural correlates of forelimb function in fur seals and sea lions, Biomechanical perspective on the origin of cetacean flukes, Balancing requirements for stability and maneuverability in cetaceans, Structure and mechanics of nonpiscine control surfaces, Hydrodynamic design of the humpback whale flipper, Dynamics of the aerial maneuvers of spinner dolphins, Fore limb myology of the pygmy hippopotamus (, Comparative morphology of the forelimb skeleton in some Odontoceti (Mammalia, Cetacea), Morphological support for a close relationship between hippos and whales, Origin of whales from early artiodactyls: hands and feet of Eocene Protocetidae from Pakistan, The morphology of the brachial plexus with a note on the pectoral muscle and its tendon twist, Behavior and ecology of the Florida manatee (.