Cooksonioids †

Amplectosporangium †

A. jiangyouense †

• Geng, 1992

• Emsian of  Sichuan Province, China

• Leafless plant, up to 7 cm with dichotomous axes and terminal fertile branches. 

• Short-stalked, oval-shaped sporangia are distributed in rows along the inner sides of the fertile branches.

• The linear arrangement of the sporangia in a cup-like fashion along the inner sides of the terminal fertile branches has been hypothesized to represent an early stage in the evolution of the seed coat or integument

A. unilaterale †

• Geng, 1992; Edwards & Li, 2018

• Plants with naked parallel-sided unbranched stems terminating in fertile complexes

• Stems with longitudinal lines, producing strap-shaped appearance which extends into the fertile complex

• Complex comprises at least two consecutive dichotomously branching axes

• Branching in daughters asynchronous, lateral sporangia borne on inside of each dichotomy

• Sporangia sessile, hemispherical in outline, margin marked by unthickened narrow border

• Sporangial bases contiguous or narrowly spaced

Hsüa †

• Li, 1982

• Early Devonian of China

H. deflexa †

• Wang, Hao & Wang, 2003

• The branching system comprises a robust creeping main axis and comparatively slender erect lateral axes inserted oppositely or alternately. 

• The lateral axes depart at right angles from the main axis. 

• Towards the apex, the main axis is perhaps erect with the lateral axes attached at smaller angles. 

• The lateral axes dichotomize equally one to three times in different planes and decrease in diameter and length acropetally. 

• They bear sparse and irregular tiny spines. 

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

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

• The xylem is possibly centrarch. 

• Based on the possibly centrarch xylem and terminal sporangium, this plant relates to the rhyniophytes, but based on the equal sporangial valves with marginal thickenings, it resembles the zosterophylls

H. robusta †

• Li & Cai, 1978; Li, 1982

• The axes are about an inch thick, with circinate, pseudo-monopodial side branches emerging from the sides. 

• The small side branches emerge immediately above a dichotomous branching point of the main axis. 

• The lateral branches are in a plane (planar). 

• In the center of the axes is a protostele with an elliptical cross-section. 

• The protoxylem was probably inside the xylem, maturing from the inside out.

• The tracheids have annular secondary wall thickening.

• Round- to kidney-shaped sporangia lie on dichotomous branches at the end of the lateral branches, and open with symmetrical valves.

• The trilete spores are 18 to 36 μm in size.

• The gametophyte is unknown.

Junggaria spinosa †

• Duo & Sun, 1983

• Upper Silurian (Přídolí)

• Isotomous or pseudomonopodially branching axes

• Sporangia are complex in shape

Sartilmania jabachensis †

• Kräusel & Weyland; Fairon-Demaret, 1986

• Emsian of Belgium

• Narrow leafless axes, from 0.75 mm to a maximum of 2 mm in diameter, marked with irregular longitudinal striations.

• Plant heavily and irregularly branched, with the lateral branches being arranged spirally. 

• Each lateral branch appears to have ended in a vertically-oriented sporangium, which caused a sharp upwards turn if the branch it terminated was near to the horizontal. 

• The sporangia were spatulate (spoon-shaped), most measuring 3.5–4 mm long by 2.5-3.5 mm wide, marked by the same longitudinal striations as were present on the stems. 

• The sporangia opened into two valves along their distal margins