quadrilobus

Quadrilobus is a descriptive term used in plant morphology to denote a leaf or leaf segment that displays four lobes arranged in a configuration that gives the overall outline a quadrilateral or four-lobed appearance. The term is not a formal taxonomic name and does not denote a distinct genus or species; rather, it serves as a descriptive feature in regional floras and field notes.

Etymology and usage history: Quadrilobus derives from the Latin quadri-, meaning four, and lobus, meaning lobe. It has appeared in limited botanical writings as a way to characterize leaf forms that do not fit simpler categories of lobed or entire leaves. Because its use is descriptive rather than taxonomic, quadrilobus is not standardized across textbooks and may vary in exact interpretation between authors.

Morphology and identification: A quadrilobus leaf typically shows four conspicuous lobes whose tips or sinuses define a roughly four-angled silhouette. Lobes may be equal or of varying size, and the boundaries between lobes can be shallow or deeply incised. In some notes, the four-lobed feature is most visible on the distal half of the leaf, while the base remains less distinctly lobed. The descriptor is most often attached to leaves with a central axis or petiole attachment that does not create a simple, unbranched outline.

Taxonomic status and reception: Quadrilobus is not a formal taxonomic category and is not universally applied. It is used primarily as a field descriptor to aid in the comparison of leaf shapes within and between species. In formal descriptions, it is usually accompanied by additional measurements and characteristics to avoid ambiguity.

See also: leaf shape terminology, lobed leaves, plant morphology.