Tracheophytes

Incertae sedis

Bitelaria dubjanski †

• Johnson 1992

• Early Devonian from New Brunswick, Canada; Middle Devonian outcrops in the Voronezh region of Russia.

• Characterized by thick-walled, dichotomously branched tubular axes and thick cuticles with possible lenticel-like eruptions

Eohostimella heathana †

• Schopf 1966

• Early Silurian (Llandovery)

• Possible vascular plant; compression fossils

• Branched dichotomously; may have exhibited small spines

• Chemistry of fossils similar to vascular plants, rather than algae

• Anatomy constitutes upright, cylindrical tubes with a thickened outer cortex, which may have contained traces of lignin or a similar compound,

• No tracheids or phloem have been found;

Hsüa †

• Early Devonian of the Xujiachong Formation, Yunnan, China

• Robust main axes (n) 7.0–(10.0)-13.0 mm in diameter, at least 12.8 cm long, creeping and dichotomous. Towards the apex they become upright. Primary xylem centrarch.

• Lateral branching systems erect, up to 10.0 cm long; "n" axis bears opposite or alternate laterals

• (n+1) at intervals of 3.0–(16.0)-32.0 mm the latter mostly inserted at right angles to the former.

• In these examples, many n+1 axes are parallel to the substrate and then turn up.

• Towards apex of n axis, n+1 axes are attached at smaller angles.

• Fertile n+1 axis dichotomizes equally 1–3 times in three dimensions and produces up to eight distal axes (n+4).

• Apices of a pair of distal axes curve in opposite directions and each terminates in a sporangium.

• Lateral axes decrease in diameter and length acropetally. n+1 axes are 1/4–1/3 of the width of n axis.

• Sparse and irregular minute spines clearly visible on lateral axes but indistinct on main one

• Terminal sporangia rounded to reniform in outline

• Sporangium dehisces into two equal valves along an indistinct convex marginal thickening.

• Spores laevigate with subtriangular amb. Trilete ray 1/2 of the radius.

H. robusta † (Li 1982)

H. deflexa † (Wang et al. 2003)

Jiangyounia gengi

• Edwards & Li 2018

• Lower Devonian

• Pseudomonopdial stems, smooth

• Sporangia are tangentially extended, oval, terminal sporangia

Margophyton goldschmidtii †

• Zakharova 1981

• Lower Devonian

• Originally Psilophyton goldschmidtii but now thought to be a possible zosterophyll with apices and attached root-like structures

Pinnatiramosus qianensis †

• Edwards et al. 2007

• Plant with a complex, extensive, pinnate branching system and pitted tracheids from marine Llandovery (lower Silurian) rocks in Guizhou Province, challenges long-held theories on the origin and early evolution of vascular plants in the Silurian and Devonian periods.

• This has led to the hypothesis that the fossils are not syngenetic with the entombing rock but represent the rooting systems of much younger plants, possibly of Permian age. Permian strata overly the Llandovery rocks unconformably in the succession.

• Leafless axes with less ordered branching occur closer to the boundary and may have had a similar source. Existing and new material of Pinnatiramosus has been subjected to detailed analyses in an attempt to resolve the problem. This has involved examination of the branching systems with respect to the surrounding matrix, comparative morphological descriptions of the systems, and anatomical investigations based on compression and permineralized fossils. The latter in particular indicate an endogenous origin of the lateral branches, typical of roots.

• Collectively such evidence is highly suggestive of roots of younger plants growing through lithified sediments—plants whose affinity and age remain to be determined but which show an amazing capacity to fill two-dimensional space efficiently, accompanied by an avoidance strategy that is also seen in recent angiosperms

Sennicaulis hippocrepiformis †

• Edwards 1981

• Early Devonian of Wales

• S. hippocrepiformis (Kenrick et al. 1991)

• Form genus for sterile axes, circular in cross-section. Xylem exhibits helical thickenings. Tracheid wall is 2-layered: a thin continuous microporiate layer covers a layer with spongy texture

• The concept of "S-type" tracheids is named after this plant (image at right)