United States Fish and Wildlife Service list of threatened and endangered arthropods species may be treated as endangered or threatened if it resembles in appearance a species which has been listed and enforcement personnel would have difficulty distinguishing between the listed and the unlisted species; if the effect of this difficulty is an additional threat to the listed species; and if such treatment of the unlisted species would improve protection for the listed species. United States Fish and Wildlife Service list of threatened and endangered arthropods List of threatened and endangered arthropods, including insects, arachnids, and crustaceans under the United States Endangered Species Act as of October 2013. Key to Listing Status
Bird feet and legs nest can use the entire foot (toes and tarsometatarsus) with the heel on the ground. Loons tend to walk this way because their legs and pelvis are highly specialized for swimming. They have a narrow pelvis, which moves the attachment point of the femur to the rear, and their tibiotarsus is much longer than the femur. This shifts the feet (toes) behind the center of mass of the loon body. They walk usually by pushing themselves on their breasts; larger loons cannot take off from land. This position, however, is highly suitable for swimming because their feet are located at