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Greek
pteron‘wing’
daktylos‘finger’
combined
combined
English
pterodactyl
‘A name used for certain extinct flying reptiles.’
The story of pterodactyl
Pterodactyl comes from the scientific name Pterodactylus, made with Greek wing and finger components. The construction calls attention to the elongated finger associated with the wing, rather than simply saying flying lizard.
This view explains the components. They are pieces of one construction, not consecutive borrowing stages.