Definition of pinnule in English:

pinnule

noun

Botany
  • 1A secondary division of a pinnate leaf, especially of a fern.

    • ‘If the primary pinnae are divided, then the individual divisions are known as pinnules.’
    • ‘The most common elements are parallel-veined leaves that resemble cordaites but that could be isolated pinnules of a pinnate leaf.’
    • ‘Fertile fronds have clusters of elongate sporangia that partially replace pinnules.’
    • ‘Lepidopteris is a bipinnate frond whose pinnules resemble some species of Alethopteris.’
    • ‘They are commonly referred to as the Lip Ferns because the sori are borne at the margins of the pinnules and the leaf margins themselves are often reflexed to form false indusia that protect the sori.’
    1. 1.1Zoology A part or organ like a small wing or fin, especially a side branch on the arm of a crinoid.
      • ‘Fishelson and Nichols observed fish targeting organisms sheltering in the arms and pinnules of living crinoids.’
      • ‘It should have required less energy for the crinoid to regenerate the damaged pinnules than to regenerate a lost or damaged tegmen containing part of the gut tract.’
      • ‘Recent crinoids are passive suspension feeders on microscopic plant and animal plankton and organic detritus by means of the tubefeet of the water vascular system in their arms and pinnules.’
      • ‘The food is transferred down the arms to the mouth by tube feet located on the pinnules and arms.’
      • ‘Their relative inedibility and dense network of arms and pinnules makes crinoids attractive to commensals - organisms which benefit from close association with a host - and other small animals that wish to hide from predators.’

Origin

Late 16th century (denoting one of the sights of an astrolabe): from Latin pinnula ‘small wing’, diminutive of pinna.

Pronunciation

pinnule

/ˈpinˌyo͞ol//ˈpɪnˌjul/