Question

1. Give the function of each, particularly as it relates to terrestriality and/or endothermy.

a) zygapophyses

b) turbinates

c) secondary palate

d) sternum

e) true muscular tongue + hyoid apparatus supporting it

f) interclavicle (joins two halves of pectoral girdle to give greater strength)

g) cleidoic egg

Answer 1

a) Zygapophyses a little bone that sticks out in the vertebrae. It interlocks the vertebral system, allows connection for abdominal musculatory system. They form between the neural arches of the vertebrae. They are secondarily lost in endotherms like whales, dolphines because they went back to water from land. Zygapopyses is the modification that took in the skeletal system that allow for the terrestrial habitat.

b) Turbinates are elongated bony structures, covered with nasal mucosa, that project off the nasal side walls and stretch across the entire nasal airway. Respiratory turbinates are the indicators of endothermy in terrestrial habitat as the main cost of endothermy is its high energetic expenditure. Basal metabolic rate of endotherms is 6–10 times higher than the standard metabolic rate of similarly sized ectotherms at equivalent body temperature.

c) Secondary Palate which separates the nasal passage from the mouth, which permits continued eating while the animal's mouth is filled with food. The animal was very active and probably requiring an endothermic metabolism in terrestrial habitat.

d) Sternum is a long flatted breast bone present in the chest. Birds are endothermic and, because they fly, they require large amounts of energy, necessitating a high metabolic rate. The sternum of birds is larger than that of other vertebrates, which accommodates the large muscles required to generate enough upward force to generate lift with the flapping of the wings. The terrestrial hypothesis holds that running was the stimulus for flight, as wings could be used to improve running and then became used for flapping flight.

e) True muscular tongue and hyoid apparatus: The hyoid is a small bone anchored by muscles from the anterior, posterior and inferior directions, and aids in tongue movement and swallowing. As all mammals arose from terrestrial ancestors whose food was not supported by a current of water, the basic (terrestrial) mammalian tongue is adapted for manipulating food. As endotherms, cetaceans maintain elevated body temperature and must avoid undue heat loss. As obligate air-breathers, they dwell near and periodically return to the surface. They have no pharyngeal or other ventilatory slits, so that all water entering the mouth must be swallowed or expelled the way it entered.
f) Interclavicle, a bone located in front of the sternum and between the clavicles in certain vertebrates, such as reptiles and amphibians. Most birds have 9 air sacs, 1 interclavicular sac plus paired cervical, anterior thoracic, posterior thoracic, and abdominal sacs. Dinosaurs are a diverse group of animals that were the dominant terrestrial vertebrates structures. Within dinosaur bone that are typical of endotherms is the interclavicle.

g) Cleidoic egg is an adaptation for terrestrial habitat. Eggs are leathery. After internal fertilization and the habit of laying eggs in terrestrial environments became a reproduction strategy amongst the amniote ancestors. Development of cleidoic egg with four extraembryonic membranes, waterproof covering for embryos is main adaptation for living a completely terrestrial life, even more important than limbs or lungs, they are endothermic. Cleidoic egg an internally fertilized egg that permitted the colonization of the land.