Extinct terrestrial
vascular plants of the Devonian period. Stem of the order of several mm to several cm in diameter and several cm to a metre long, erect or arched, dichotomizing occasionally, furnished with true roots at the base. Vascular bundle
actinostele,
tracheids of primitive annular or helical type (so-called G-type). Leaves are unbranched thorn-shaped (i.e. with a wide base, tapering to a blunt point)
microphylls several mm long with a single prominent vascular thread, arranged spirally to randomly on the stem.
Sporangia borne singly on the upper leaf surface.
Drepanophycus has similarities to the genus
Halleophyton. It differs from a closely related genus of the same period,
Baragwanathia, in the position of the sporangia, and the arrangement and shape of the leaves; see
Drepanophycaceae for more details. It is more derived than the coexisting genus
Asteroxylon, which has
enations lacking vascules, in contrast to the true leaves of
Drepanophycus.
Drepanophycus spinaeformis was first discovered in
Scotland; fossils have since been recovered in
Russia (around
Lake Shunet in the republic of
Khakassia), in the
Yunnan province of the
People's Republic of China, and in
Egypt. They were among the earliest land plants, growing to approximately 80 cm in height. The species is notably differentiated from other plants in the
genus by its thicker stems. Foliage is described as firm and spiny, though recovered fossils rarely retain leaf detail. The
stomata of
D. spinaeformis look similar to that of
Lycopodium japonicum. They both consist of two large guard cells and pore, and are anomocytic. There were two small guard cells surrounded by two large similarly shaped subsidiary cells (paracytic) deriving from a pronounced elliptical cuticular ledge on the surface of the guard cells surrounding a thickened circumpolar area. Complex underground
rhizome systems of
Drepanophycus have been reported from Yunnan's
Xujiachong Formation (Early Devonian); these are the earliest rooted
paleosols in Asia, and predate the first trees with deep roots by 20 million years. ==References==