Spination

Spination is the presence and arrangement of spine-like projections on an organism or its structures. It is a morphological feature used across biological disciplines to describe surface ornamentation and to aid in species identification, functional interpretation, and evolutionary study. Spination includes spines proper as well as small spinules and bladelike projections.

In plants, spines are commonly modified leaves, stipules, or parts of the shoot that form rigid, pointed structures. Spination patterns are described by orientation (central, marginal, radial), density (spines per square centimeter), length, and base width. Spines can deter herbivory, reduce water loss, or protect against intense solar radiation in arid habitats; cacti are a typical example.

In animals, spination refers to spinose projections on integuments, shells, or skeletal surfaces. Sea urchins and other echinoderms bear prominent spines that can be oriented and measured for ecological or taxonomic purposes. In arthropods and reptiles, various spinose elements may help in defense, camouflage, or sensory function. In paleontology, spination patterns on fossil bones or shells assist in separating related taxa.

Characterization relies on direct observation and microscopy, sometimes with scanning electron microscopy. Measurements include spine length, base diameter, angle of projection, and density per unit area. Spination can be genetically determined, but may also vary with age, nutrition, or environmental conditions.

Spination is distinguished from related terms such as spinose ornamentation, pubescence, bristles, or tuberculation, and is often used alongside other morphological descriptors in taxonomic keys.