Stigmaria

Stigmaria; Temporal range: Carboniferous-Permian, 323.2–254.0 Ma PreꞒ Ꞓ O S D C P T J K Pg N Possible Devonian record
	Stigmaria, a fossil lycopsid rhizome.
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Lycophytes
Class:	Lycopodiopsida
Order:	†Lepidodendrales
Genus:	†Stigmaria; Brongn.

Stigmaria is a form taxon for common fossils found in Carboniferous rocks.^[1] They represent the underground rooting structures of arborescent lycophytes such as Sigillaria and Lepidodendron.

Description

These swamp forest trees grew to 50 meters and were anchored by an extensive network of branching underground structures with rootlets attached to them. Analysis of the morphology and anatomy of these stigmarian systems suggests they were shoot-like and so they are called rhizomes or rhizomorphs. The stigmarian rootlets were rhizomorph axes that typically had circular scars around the rhizomorphic apices, where the root hairs were attached. These rootlets were branched dichotomously, meaning that there were multiple orders of branching to comprise areas of the stigmarian system.^[2]

Since the stigmarian systems are shoot-like, these rootlets may be modified leaves, adapted to serve the function of roots. Since Stigmaria had a complex branching structure and root hairs, it is comparable to arborescent lycophyte roots of the distant living relative, the quillworts (genus Isoetes).^[2]

References

^ Rothwell, GW; Erwin, DM (1985). "The rhizophore apex of Paurodendron: implications for homologies among the rooting organs of Lycopsida". American Journal of Botany. 72: 86–98. doi:10.2307/2443571. JSTOR 2443571.
^ ^a ^b Hetherington, AJ; Berry, CM; Dolan, Liam (June 14, 2016). "Networks of highly branched stigmarian rootlets developed on the first giant trees" (PDF). PNAS. 113 (24): 6695–6700. doi:10.1073/pnas.1514427113. PMC 4914198. PMID 27226309. Retrieved 15 February 2017.

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[Rothwell-1] Rothwell, GW; Erwin, DM (1985). "The rhizophore apex of Paurodendron: implications for homologies among the rooting organs of Lycopsida". American Journal of Botany. 72: 86–98. doi:10.2307/2443571. JSTOR 2443571.

[Hetherington-2] Hetherington, AJ; Berry, CM; Dolan, Liam (June 14, 2016). "Networks of highly branched stigmarian rootlets developed on the first giant trees" (PDF). PNAS. 113 (24): 6695–6700. doi:10.1073/pnas.1514427113. PMC 4914198. PMID 27226309. Retrieved 15 February 2017.

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