Leptocephalic

Part of speech: adjective

Definitions

1. Having a skull that is notably narrow and elongated in shape relative to its width
2. Characterized by a long, slender form of the skull with proportionally reduced width
3. Possessing a skull with an elongated structure and relatively narrow dimensions from side to side

Etymology: "Leptocephalic" is built from two Greek elements: "leptos", meaning slender or thin, and "kephalē", meaning head, with the adjective-forming suffix "-ic" added at the end. Its literal sense is "thin-headed" or "having a narrow head," and it is a technical coinage in the vocabulary of anatomy and zoology rather than a word that passed down from antiquity. The term is applied to the larval stage of eels and certain related fishes, whose young are flat, transparent, and leaf-shaped, which is why the "thin-head" description was chosen to name them. Their clear, ribbon-like bodies made the larvae look so unlike adult eels that early observers struggled to identify them, and the name reflects that narrow, slender form.