Stockmansella

Stockmansella is a genus of extinct plants of the Middle Devonian (Eifelian stage, around 393 to 388 million years ago), 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 (spore-forming organs) on short lateral branches (sporangiophores). The prostrate stems have bulges from which rhizoids form. Both prostrate and upright stems have a central strand of conducting tissue which contains simple tracheids, so that Stockmansella is a vascular plant.[3]

Stockmansella
Temporal range: Middle Devonian
Stockmansella langii
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Subdivision: †Rhyniophytina
Class: †Rhyniopsida
Order: †Rhyniales
Family: †Rhyniaceae
Genus: †Stockmansella
Fairon-Dem. (1986)[1]
Species
  • S. langii (Stockmans) Fairon-Dem. (1986)[1]
  • S. remyi Schultka & Hass (1997)[2]

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 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.[3]

In 2004, Crane et al. published a cladogram for the polysporangiophytes, in which Stockmansella is placed in the Rhyniaceae, sister to all other tracheophytes (vascular plants).[4]

polysporangiophytes
 

† Horneophytopsida (Caia, Horneophyton, Tortilicaulis)

 
 
 

† Aglaophyton

 
tracheophytes
 

† Rhyniaceae (Huvenia, Rhynia, Stockmansella)

 
 
 

† basal groups (Aberlemnia caledonica [=Cooksonia caledonica], Cooksonia pertoni)

 
 

lycophytes and their stem groups

 
 

euphyllophytes

 
 
 
 
 

References
  1. Fairon-Demaret, M. (1986), "Stockmansella, a new name for Stockmansia", Taxon, 35: 334, doi:10.2307/1221284, JSTOR 1221284, cited in Taylor, Taylor & Krings 2009
  2. Schultka, Stephan & Hass, Hagen (1997), "Stockmansella remyi sp. nov. from the Eifelian: new aspects in the Rhyniaceae (sensu Hass et Remy, 1991)", Review of Palaeobotany and Palynology, 97 (3–4): 381–393, doi:10.1016/S0034-6667(96)00074-7
  3. Taylor, T.N.; Taylor, E.L. & Krings, M. (2009), Paleobotany : The Biology and Evolution of Fossil Plants (2nd ed.), Amsterdam; Boston: Academic Press, ISBN 978-0-12-373972-8, pp. 245–6, 248–9
  4. Crane, P.R.; Herendeen, P. & Friis, E.M. (2004), "Fossils and plant phylogeny", American Journal of Botany, 91 (10): 1683–99, doi:10.3732/ajb.91.10.1683, PMID 21652317, retrieved 2011-01-27
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