Annual, prostrate herbs with dorsiventrally compressed, ascendingly branched stems. Leaves small, crenate-dentate or lobulate, asymmetric. Flowers tiny, disposited between the leaves or bracts, neither axillary nor opposed to them, tetramerous. Stamens: anthers broad, included in the corolla, on 4 short filaments attached to about the middle of the corolla tube. Ovary glandular villose, pyramidate; styles terminal, 2, united at base, with tiny stigmas at the apex. Fruit rostrate, dividing into two 2-seeded halves first, later halves again divided into single-seeded nutlets; ventral side of nutlets with a sharp angle, dorsal side with corky, vesicular mesocarp; endocarp thick with strong ridges and protuberances.
Coldenia was described by Linnaeus as monotypic with the single species C. procumbens. In later times, up to as many as 20 American species have been included, until Richardson demonstrated in 1976 that there are marked differences between them and the original Coldenia. For the American species, the generic name Tiquilia was available. Tiquilia species are perennial herbs or subshrubs with symmetric leaves and pentamerous flowers. The endocarp is thin, a mesocarp is entirely lacking.