whale forelimb function
... Cetacean ﬂ ippers function to stabilize the body and aid in turns ( Woodward et al., 2006 ). Forelimb myology has been described for balaenopterids (e.g., Carte and MacAllister, 1867; Perrin, 1870; Schulte, 1916; Schulte and Smith, 1918) and for a balaenid (Eschricht and Reinhardt, 1866); however, eschrichtiid forelimb myology remains undescribed. Forelimb of a cat and flipper of a whale are analogous organs as both these animals will share the functions, but have different structures. Sensory branches of the musculocutaneous and ulnar nerves may be crucial for gathering hydrodynamic loading information on the flipper. A: Fin whale (Balaenoptera physalus). Antebrachial musculature is reduced in those taxa that are able to locomote quickly and are more agile (e.g., sharp and high‐speed turns, smaller turning radii, Fish, 2002a; Woodward et al., 2006), most delphinid odontocetes and the Megaptera. Perhaps they serve some function such as helping to support the whale's reproductive anatomy, but there are many different types of structures which would be better suited to such a task. The tree shrew is small bodied, moves easily on the ground or in the trees, and has a flexible forelimb for these functions. Results were compared with published descriptions of both artiodactyls and secondarily aquatic vertebrates. Anat Rec, 290:1121–1137, 2007. These muscles were encased in a thick fascia from which the muscle fibers take origin. In addition to these two intrinsic manus muscles, Physeter possessed a flexor retinaculum (Fig. Absence of most soft tissue structures decreases flipper thickness. Extensor muscle contraction may act to stiffen the flipper, but no evidence suggests the ability to extend the digits. Dissection of a phocoenid and several small‐bodied delphinids revealed a radical reduction in this muscular morphology; there was no gross evidence of muscle fibers of antebrachial muscles in these taxa (Fig. Figure 6. In contrast, firm attachments of the extensors suggest a limited range of motion, and inability of the tendons to slide along the digit. The taxonomic diversity of this database allows for phylogenetic interpretations of the evolution of antebrachial muscles and tendons. Some bodies in structure and origin are essentially the same, but altered to conduct distinct tasks in distinct species. The antebrachial musculature displays both large muscle bellies and robust tendons, with relatively the same sized muscle bellies as the otariid, the California sea lion (English, 1976; Gordon, 1983). Carpal Morphology and Function in the Earliest Cetaceans. This head acts to move the flipper caudally, and lowers the leading edge of the flipper ventrally (Benke, 1993). In Physeter, extensor tendons pass over the terminal phalanx, expand craniocaudally, and fan out into the connective tissue along the flipper margin. Organism Organism Common Name for Some between different Forelimb Function of Foreimb Fish Amphibian (Frog Reptile (Lizard) (picture) Reptile (Snake Bird Mammal Rat) Mammal Human (picture Whale Cow All taxa retained a triceps humeral head (m. triceps brachii, caput laterale). The lack of active digital curling against flow is not surprising as Globicephala displays reduced antebrachial muscle morphology (Murie, 1873) and probably lacks the ability to move the digits. Cooper (2004) documented a fixed cubital joint in three fossil mysticete lineages (Aetiocetidae, Eomysticetidae, and “Cetotheriidae”), with the earliest record of a fixed cubital joint occurring in aetiocetids known from the late Oligocene (28Ma) in the North Pacific. Modern whales have a completely different genome in comparison to Indohyus. Functional, physiological, and muscle histochemical studies are needed to test the hypotheses presented here. Odobenid (walrus) forelimbs act as paddles or rudders for steering (Gordon, 1981) and are used to remove sediment when searching for prey (Levermann et al., 2003). Redman, Dr. F.E. This is a PDF for printing on paper.) Learn more. By decreasing thickness, aspect ratio is increased and affords cetaceans a greater ability to generate lift. m. flexor digitorum communis (fdc), m. flexor digitorum radialis (fdr). Largest is blue whale (85-95 feet, 26-29 meters), smallest is vaquita (5 feet, 1.5 meters) Whales that evolved after Ambulocetus (Kutchicetus, etc.) The shovellike paw comprises almost half the length of the limb. Well‐developed flexor and extensor muscles were found in mysticetes and basal odontocetes (i.e., physeterids, kogiids, and ziphiids), whereas later diverging odontocetes (i.e., monodontids, phocoenids, and delphinids) lack or reduce these muscles.