3] genera, Androtrichum is diagnosed by the presence of elongated stamen filaments that are persistent and dispersed with the nutlets.
Among the clearly recognizable larger genera are Kyllinga, and Pycreus (together with monotypic Queenslandiella), which have laterally flattened nutlets.
The gynophore in Cypereae, formed by the development of the hypogynous stalk, is characterised by a lobed cup that envelops the basal part of the nutlet (Vrijdaghs et al.
The earliest fossil material comes from the Paleocene/Eocene of western Tennessee and includes a scaly cupule that enclosed three winged nutlets with similarities to Trigonobalanus, a modern relative of oaks, and assigned to the species Trigonobalanoidea americana (Crepet, 1989; Crepet & Nixon, 1989).
Animals may have removed the wings from nutlets and cached the nutlets in the soil for later use (just as modern rodents and jays do with some winged pine seeds; e.
In addition to having their nutlets buried, plants may have benefited from target dispersal, the disproportionate movement of propagules to favorable microhabitats for establishment (Grey & Naughton, 1971; Stapanian & Smith, 1986; Vander Wall, 1993), and long-distance dispersal (Clark, 1998).