''Stockmansella'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

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, ) 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 cyc ...

(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 u ...

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 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, so that ''Stockmansella'' is a

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 ...

. The genus was created by Fairon-Demaret for fossil forms previously assigned to '' Taeniocrada'' 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 ''Sciadophyton'' is thought to be the

gametophyte A gametophyte () is one of the two alternation of generations, alternating multicellular organism, multicellular phases in the life cycles of plants and algae. It is a haploid multicellular organism that develops from a haploid spore that has on ...

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 ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to ...

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 ...

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 rank used for this group, some treating it as the cla ...

, sister to all other tracheophytes (vascular plants).

References

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