Drepanophycales is an order of extinct

lycophyte The lycophytes, when broadly circumscribed, are a group of vascular plants that include the clubmosses. They are sometimes placed in a division Lycopodiophyta or Lycophyta or in a subdivision Lycopodiophytina. They are one of the oldest lineag ...

plants of Late

Silurian The Silurian ( ) is a geologic period and system spanning 23.5 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the third and shortest period of t ...

to Late

Devonian The Devonian ( ) is a period (geology), geologic period and system (stratigraphy), system of the Paleozoic era (geology), era during the Phanerozoic eon (geology), eon, spanning 60.3 million years from the end of the preceding Silurian per ...

age (around ), found in North America, China, Russia, Europe, and Australia. Sometimes known as the Asteroxylales or Baragwanathiales.

Description

Extinct terrestrial

vascular plant Vascular plants (), also called tracheophytes (, ) or collectively tracheophyta (; ), are plants that have lignin, lignified tissues (the xylem) for conducting water and minerals throughout the plant. They also have a specialized non-lignified Ti ...

s of the

periods. Stem of the order of several mm to several cm in diameter and several cm to several metres long, erect or arched, dichotomizing occasionally, furnished with true roots at the base. Vascular bundle an exarch actinostele,

tracheid A tracheid is a long and tapered Lignin, lignified cell in the xylem of Tracheophyta, vascular plants. It is a type of conductive cell called a tracheary element. Angiosperms also use another type of conductive cell, called vessel elements, to t ...

s of primitive annular or helical type (so-called G-type). Stem clothed in either

microphyll In plant anatomy and evolution a microphyll (or lycophyll) is a type of plant leaf with one single, unbranched leaf vein. Plants with microphyll leaves occur early in the fossil record, and few such plants exist today. In the classical concept of ...

s (leaves with a single vascular thread or 'vein'), or with leaf-like enations (unvascularized projections) with a vascular trace into the base of each enation. Homosporous, with

sporangia A sporangium (from Late Latin, ; : sporangia) is an enclosure in which spores are formed. It can be composed of a unicellular organism, single cell or can be multicellular organism, multicellular. Virtually all plants, fungus, fungi, and many ot ...

borne singly and dehiscing by a single slit.

List of families

The following families have, at various times, been segregated within the Drepanophycales. However, Kenrick and Crane (1997) in their cladistic study place ''Asteroxylon'' in the clade Drepanophycaceae. Taylor, Taylor & Krings (2009) do not use the family at all, only the order Drepanophycales, and say that ''Asteroxylon'' is sometimes included in the Drepanophycales. The anatomical details for the genera in the included families are tabulated by Gensel (1992) * Drepanophycaceae Kräusel & Weyland **stem with

s ***genus '' Drepanophycus'' Göppert ****microphylls short, tapering rapidly from wide base (thorn-shaped) ****microphylls arranged spirally or randomly on stem ****sporangia borne on upper surface of microphylls ***genus '' Baragwanathia'' Lang & Cookson ****microphylls long, not tapering over most of length (strap-shaped) ****microphylls arranged spirally on stem ****sporangia borne axially (whether on microphylls or on stem is not known) **genus '' Sengelia'' Matsunaga & Tomescu * Asteroxylaceae Kidston & Lang **stem with unvascularized enations ***genus '' Asteroxylon'' Kidston & Lang A large unnamed drepanophylacean is also known from the Early Devonian Hunsrück Slate of Germany.

Notes

{{Taxonbar, from=Q147600 Devonian plants Silurian plants Silurian first appearances Late Devonian extinctions Prehistoric plant orders Lycophyte orders