Behnam Hamzeh׳ee - Research Institute of Forests and Rangelands, P. O. Box: ۱۳۱۸۵-۱۱۶, Tehran, Iran
Mostafa Assadi - Research Institute of Forests and Rangelands, P. O. Box: ۱۳۱۸۵-۱۱۶, Tehran, Iran

Piptatherum denaense is described as a new species from south west of Iran, Dena Mountain. It is close to P. laterale but differs from it by having glabrous lemma in lower half and toward the apex, narrower vegetative shoots and unbearded anthers. Piptatherum holciforme subsp. holciforme var. glabrum is not accepted as a distinct variety. Piptatherum sphacelatum formerly known as a synonym of P. molinioides is established as a separate species due to having distinct morphological characters as well as molecular differences based on literature. Thus, the number of taxa in the genus Piptatherum changes to ۹ species, ۲ subspecies and ۴ varieties in Iran. An identification key to Piptatherum taxa occuring in Iran is provided. The distribution map of P. denaense with P. laterale subsp. laterale and the illustration of the new species are included.

Piptatherum, Poaceae, new species, new synonym, reestablished species, Iran