Aneurophytales †

Ecology & Form

Stem

Morphology

• Three-dimensional branching systems

• Lateral axes were helical or decussate

• These plants were probably small shrubby or vine-like

Anatomy

• Ribbed or lobed protostele in center of stem displaying mesarch maturation

• Protoxylem surrounded by pycnoxylic wood formed from a cambium

• Cauline protoxylem was a central strand

Classification

Embryophytes

└Polysporangiophytes

└Tracheophytes

└Eutracheophytes

└Euphyllophytes

└Lignophytes

└Progymnosperms †

└Aneurophytales †

Diversity

Aneurophyton †

• Middle-Late Devonian of Europe, Russia, United States

• Aneurophyton is similar to Tetraxylopteris in overall form, but its branches are arranged helically rather than decussately.

• Dichotomous ultimate branches in Aneurophyton were photosynthetic but unwebbed, and sometimes interpreted as leaves

  • They were determinate in nature (Scheckler 1976)

• In the fertile axes, ultimate branches are replaced by dichotomies with multiple homosporous sporangia arising along the length of each fork of the branch.

• Sporangia appear to recurve toward the center of the dichotomy, but this may be an artifact of preservation.

• The main axis of Aneurophyton has a lobed protostele and produced a small amount of secondary xylem from meristematic regions between the lobes.

• Axes are relatively slender suggesting vine growth form, similar to aneuophytes found at Gilboa, NY

A. doui †

• Jiang et al. 2013

• At least four orders of axes and ultimate units (vegetative appendages/fertile organs)

• Spines, 0.5–1.5 mm long, occur sparsely on the surface of all orders of axes and ultimate units.

• First-order axes, up to 6 mm wide and at least 90 mm long, demonstrate only a slight distal taper.

• Second-order axes, up to 4 mm wide, diverge helically from the first-order axis in closely inserted pairs.

• From the second order, axes of subsequent orders are produced by bifurcation; third-order axes are 2.0–2.5 mm wide, and fourth-order axes are 1.5–2.0 mm wide.

• Vegetative appendages, 7.0–13.0 mm long as a whole, diverge from the third- or fourth-order axes in helical pairs, as a one to three times dichotomizing system

• of three-dimensionally-extended flattened branchlets.

• Fertile organs, 3.7–8.0 mm long as a whole and borne on the third or fourth-order axes, are up to three times opposite/subopposite pinnate systems.

• All three orders of fertile organ axes, in most cases recurved and rarely straight, bear sporangia or organ axes.

• Sporangia, oppositely, suboppositely, or alternately, are inserted distichously to the usually adaxial side of the fertile organ axes; they are short-stalked, elliptical, 0.8–1.3 mm wide, and 2.2–3.5 mm long, and they sometimes have longitudinal dehiscence or a twisting configuration.

A. germanicum †

• Krausel & Weyland 1941

A. olnense †