Spinula

Spinula is a small spine-like projection on a surface, used across biology to denote minute outgrowths. The term derives from Latin spinula, meaning a small thorn. Spinulae can be found on pollen grains, spores, seeds, and other microscopic structures where they create surface ornamentation that can be taxonomically informative.

On animal cuticles and exoskeletons, spinulae may function in adhesion, protection, or sensory interfaces. In shells or integuments, such projections can influence interactions with water or other organisms, or contribute to camouflage and surface texture. Because spinulae are typically minute and require microscopy to observe, their identification demands careful preparation and imaging, and their interpretation can vary among taxa.

In scientific descriptions, spinulae are used as morphological characters to distinguish species, groups, or developmental stages, and they appear in studies across botany, zoology, paleontology, and microscopy. The concept is descriptive rather than taxonomic, serving to document surface features that may have functional or evolutionary significance.

See also: spinule, a related term for a similarly small spine-like projection.