Behold the spectacularly long-tongued glossophagine nectar bat, Anoura fistulata:
This length of tongue is unusual for the genus, and there is an explanation for how it can fit all of that into its mouth: it doesn’t. The base of the tongue has been carried back deep into the chest in a pocket of epithelium, and is actually rooted in the animal’s chest.
Across the glossophagine nectar bats, maximum tongue extension is tightly correlated with the length of their rostral components, such as the palate and mandible. Although the correlation holds for A. caudifer and A. geoffroyi, A. fistulata falls far outside the 95% confidence interval. Close examination of tongue morphology reveals the basis for this pattern. In other nectar bats, the base of the tongue coincides with the base of the oral cavity (the typical condition for mammals), but in A. fistulata the tongue passes back through the neck and into the thoracic cavity. This portion is surrounded by a sleeve of tissue, or glossal tube, which follows the ventral surface of the trachea back and positions the base of the tongue between the heart and the sternum.
Unsurprisingly, this adaptation co-evolved with the lengthening corolla of a tropical flower, Centropogon nigricans—observations suggest that this bat is the only pollinator of this particular flower.
I’m sure Gene Simmons would be jealous.
Muchhala N (2006) Nectar bat stows huge tongue in its rib cage. Nature 444:701-702.