An outline of the anatomy common to all animals of the class Horotheria. Skeleton in yellow, nervous system in grey, circulatory system in dark blue, reproductive system in pink, digestive system in orange, respiratory system in light blue.
«- Skeleton (yellow): the bones are mostly calcium carbonate (rather than phosphate, as ours), with a smaller amount of structural polysaccharides. Overall, the skeleton is relatively light: not all the bones are directly connected to it, and it's kept together by tendons and ligaments. The most important bones are the skull, the thoracic shield protecting the brain (a central ring contains the cloaca), two spines connected by anular ribs or a "basket ribcage" and the pleural plates that protect the lung. - Nervous system (grey): the brain is located in a cavity of the thoracic shield, and it's connected to the sense organs in the head by a thick nerve cord. While the organs of sight, smell and taste are all found in the head, the main organs of hearing (not depicted) are elastic pads in the feet. - Reproductive system (pink): the gonad are also in the chest, and connected to the cloaca. Mating occurs through a chest-to-chest cloacal kiss; in some species, the male's cloaca extroverts in the female's one. - Circulatory system (dark blue): three small hearts are located along a dorsal aorta. The first one pumps blood in/out of the brain, the third one in/out from the lungs and the middle one in the rest of the body. - Digestive system (orange): the digestive tract is a tube covered by a web of blood vessels (not pictured); before reaching the pulmonary heart, the tube turns backward and becomes a rather large intestine, ending in the cloaca. - Respiratory system (light blue): air entres the body from two lateral spiracles, and flows into several chambers within the pneumatic tail. Air is then pumped through two tubes which meet near the pulmonary heart. The single tube then proceeds until the cloaca.»