Calyptocarpus is a small genus of flowering plants in the daisy family, Asteraceae (order Asterales), placed within tribe Heliantheae according to GBIF's backbone taxonomy. The genus name comes from the Greek kalypto ("covered" or "hidden") and karpos ("fruit"), an allusion to the fruit's form.
Species in the genus are low, sprawling perennial herbs with decumbent to prostrate stems reaching up to about 30 cm (12 in) long. Leaves are arranged oppositely along the stem and vary in shape, with toothed margins. Flower heads are borne singly in the leaf axils, each made up of three to eight light-yellow ray florets surrounding several yellow disc florets. The fruit is a flat cypsela topped with a pappus of two or more bristle-like awns, which likely aids in attachment and dispersal.
Wikipedia recognizes two to six species in the genus, distributed across the southern United States and Latin America, including C. biaristatus in Brazil, Paraguay, Uruguay, and Argentina; C. burchellii in southeastern Brazil; C. vialis in Texas, Louisiana, Central America, and Venezuela; and C. wendlandii in Central America and southern Mexico. The most widely known member, C. vialis, goes by common names such as straggler daisy, horseherb, hierba del caballo, lawnflower, and creeping Cinderella-weed, and has become naturalized well beyond its native range, including Taiwan, Australia, Hawaii, and other parts of the United States. Species counts and identities differ slightly between sources — GBIF's backbone taxonomy records only two descendant species under the genus, and a further species, C. brasiliensis, does not appear in the Wikipedia account at all — reflecting some ongoing uncertainty in the genus's circumscription.
Etymology
The genus name Calyptocarpus comes from the Greek kalypto ("covered" or "hidden") and karpos ("fruit"), referring to the character of its fruit.
Distribution
Species of Calyptocarpus occur in the Southern United States and Latin America. C. vialis is native to Texas, Louisiana, Central America, and Venezuela, and has naturalized in Taiwan, Australia, Hawaii, and other parts of the United States; C. wendlandii occurs in Central America and southern Mexico.
Taxonomy Notes
GBIF's backbone taxonomy places Calyptocarpus in family Asteraceae, order Asterales, within tribe Heliantheae, but records only two descendant species. Wikipedia instead lists four accepted species (C. biaristatus, C. burchellii, C. vialis, C. wendlandii), stating that two to six are recognized, and does not mention C. brasiliensis, which appears in the genus's species records — indicating some disagreement between sources on the genus's exact circumscription.
