Chapter 21: Preparations

''The dragon hydrocarbon organ system is the defining feature of the draconic clade; even in flightless, obligate aquatic, or the occasional limbless breed, if they possess the hydrocarbon organ system, they are defined as dragons. ''

''The organ system is estimated to have originally evolved during the Neogene Period between 18 and 24 MYA, based on genetic evidence from the draconic genome, although some estimates put its origin much earlier, during the Paleogene's Eocene Epoch, between 48 and 34 MYA. Originally an offshoot of an additional liver lobe among tunnel-dwelling reptiles, its original purpose appears to have been in protecting the proto-dragons from heavy-metal poisoning accumulated from the stones of their native environment. Later evolutionary adaptations shifted the liver lobe into a distinct organ of its own, capable of chemical synthesis of basic hydrocarbons in conjunction with symbiotic bacteria, hypothesized as a form of energy storage. Later mutations created the secondary organs in the hydrocarbon system that distill oxygen, and transport, store, mix and ignite the hydrocarbons for firebreathing. True flight in the draconic species only appeared after the evolution of the pressurized oxygen bladders adjacent to the respiratory and hydrocarbon systems; at rest, the dragon uptakes oxygen from the atmosphere and stores it under pressure in the bladder. This oxygen is then either used for fueling flight muscles or for igniting hydrocarbons for firebreathing.''

—An Introduction To Dragon Biology, 17th Edition, Oxford University Press, 1793

Foreshadowing
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Epigraph Tie-In

 * The epigraph introduces the organ system whose presence in an organism marks them as dragons. Injury to these organs can result in the dragon exploding, which is what happened to at least one of the hatchlings mentioned in the chapter.

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