Drepanophycales is an order of extinct

lycopsid Lycopodiopsida is a class of vascular plants known as lycopods, lycophytes or other terms including the component lyco-. Members of the class are also called clubmosses, firmosses, spikemosses and quillworts. They have dichotomously branching s ...

plants of Late

Silurian The Silurian ( ) is a geologic period and system spanning 24.6 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 shortest period of the Paleozo ...

to Late

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...

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 (), form a large group of land plants ( accepted known species) that have lignified tissues (the xylem) for conducting water and minerals throughout the plant. They al ...

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 lignified cell in the xylem of vascular plants. It is a type of conductive cell called a tracheary element. Angiosperms use another type of tracheary element, called vessel elements, to transport water through the ...

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, ) is an enclosure in which spores are formed. It can be composed of a single cell or can be multicellular. Virtually all plants, fungi, and many other lineages form sporangia at some point in their life cy ...

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) , tables 2 & 3. *

Drepanophycaceae Drepanophycaceae is a family of extinct lycophytes of Late Silurian to Late Devonian age (), found in North America, China, Russia, Europe, and Australia. Description The stems are several mm to several cm in diameter and several cm to severa ...

Kräusel & Weyland **stem with

s ***genus ''

Drepanophycus ''Drepanophycus'' is a genus of extinct plants of the division Lycopodiophyta of Early to Late Devonian age (around ), found in Eastern Canada and Northeast US, China, Russia, Egypt and various parts of Northern Europe and Britain. Description E ...

'' 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 ''Baragwanathia'' is a genus of extinct lycopsid plants of Late Silurian to Early Devonian age (), fossils of which have been found in Australia, Canada, China and Czechia. The name derives from William Baragwanath who discovered the first spec ...

'' 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) * Asteroxylaceae Kidston & Lang **stem with unvascularized enations ***genus ''

Asteroxylon ''Asteroxylon'' ("star-shaped xylem") is an extinct genus of vascular plants of the Division Lycopodiophyta known from anatomically preserved specimens described from the famous Early Devonian Rhynie chert and Windyfield chert in Aberdeenshire, S ...

'' Kidston & Lang

Notes

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