''Stockmansella'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of extinct plants of the Middle Devonian (

Eifelian The Eifelian is the first of two faunal stages in the Middle Devonian Epoch. It lasted from 393.3 ± 1.2 million years ago to 387.7 ± 0.8 million years ago. It was preceded by the Emsian Stage and followed by the Givetian Stage. North American ...

stage, around ), fossils of which have been found in north-west Germany. The sporophyte generation consists of prostrate dichotomizing stems (axes) up to 10 cm long and around 3mm wide, which at intervals produce narrower smooth upright stems. These bear

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 ...

(spore-forming organs) on short lateral branches (sporangiophores). The prostrate stems have bulges from which

rhizoid Rhizoids are protuberances that extend from the lower epidermal cells of bryophytes and algae. They are similar in structure and function to the root hairs of vascular land plants. Similar structures are formed by some fungi. Rhizoids may be un ...

s form. Both prostrate and upright stems have a central strand of conducting tissue which contains simple

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, so that ''Stockmansella'' is a

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 ...

. The genus was created by Fairon-Demaret for fossil forms previously assigned to ''

Taeniocrada ''Taeniocrada'' is a genus of extinct plants of Devonian age (). It is used as a Form taxon, form genus for fossil plants with leafless flattened stems which divided dichotomous branching, dichotomously and had prominent midribs regarded as con ...

'' but which differ in having single lateral sporangia. (She initially gave the genus the name ''Stockmansia'', but this had already been used for a genus of ferns.) The

form genus Form classification is the classification of organisms based on their morphology, which does not necessarily reflect their biological relationships. Form classification, generally restricted to palaeontology, reflects uncertainty; the goal of sc ...

''Sciadophyton'' is thought to be the

gametophyte A gametophyte () is one of the two alternating multicellular phases in the life cycles of plants and algae. It is a haploid multicellular organism that develops from a haploid spore that has one set of chromosomes. The gametophyte is the se ...

stage of several early land plants, including ''Stockmansella'', although as these forms have only been found as compressed fossils, their morphology is not entirely clear. In 2004, Crane et al. published a

cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...

for the

polysporangiophyte Polysporangiophytes, also called polysporangiates or formally Polysporangiophyta, are plants in which the spore-bearing generation (sporophyte) has branching stems (axes) that bear sporangia. The name literally means 'many sporangia plant'. The cl ...

s, in which ''Stockmansella'' is placed in the

Rhyniaceae The rhyniophytes are a group of extinct early vascular plants that are considered to be similar to the genus ''Rhynia'', found in the Early Devonian (around ). Sources vary in the name and Taxonomic rank#Ranks in botany, rank used for this group, ...

, sister to all other tracheophytes (vascular plants).

References

{{Taxonbar, from=Q7618128 Middle Devonian plants Prehistoric plant genera