Archaeopteris hibernica

Overview

Archaeopteris hibernica is a Devonian plant encountered through fossil foliage bearing overlapping small leaflets. Examine the shape and margins of the leaflets arranged along the axis one by one.^[1]

Key facts

The Kilkenny frond specimen presented in a 1910 book is more than 80 cm long. It shows how small leaflets together make up a large frond.^[1]

Time and place

The original Irish specimen is recorded as having been found in Late Devonian rocks at Kilkenny in present-day Ireland. A specimen housed in Dublin was presented as the material for Fig.368.^[1]

The time range describes source context, not the complete duration of this species.

Size, form and skeleton

The leaflets are obovate, broader toward their tips, and overlap their neighbors. Their margins are smooth or very slightly divided, creating a dense outline along branch-like sections of the frond.^[1]

Habitat and reproduction

Seward described spindle-shaped sporangia arranged on reproductive portions of the frond that he treated separately. Comparing foliage and reproductive structures together was an important clue to understanding this plant at the time.^[1]

Fossil discovery

In 1852, Forbes introduced foliage found by Irish surveyors as Cyclopteris hibernica. Through Baily’s more detailed description and later clarification of names, it came to be known as Archaeopteris.^[1]

References

1. Fossil Plants, Volume II — Archaeopteris hibernica
2. Seward (1910) — Kilkenny leaf fossils and changes in their names
3. Falahatgar et al. (2018) — Devonian colonial corals found in Iran

Research questions

The 1910 book records how researchers’ interpretations of this plant’s reproductive structures changed. It illustrates how reexamining detailed structures can change our view of a plant even when its foliage looks fern-like.^[1]

Observation

In the illustration, examine the overlapping leaflets along a short section of the frond. Move your gaze from the widened tips to the smooth or slightly divided margins.^[1]