Organism · Vascular plants
Asteroxylon mackiei
Source time context (not species duration) · ≈ 407 Ma
Inferred life reconstruction
Asteroxylon mackiei
Overview
Asteroxylon mackiei is an early lycophyte with small leaves and complex underground structures. It is known from the terrestrial ecosystem of Rhynie around 400 million years ago. It reveals how upward-growing parts differed from those directed into the ground.[1]
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Key facts
Thirty-one consecutive rock sections brought a plant back into three dimensions. In 2021, researchers connected structures visible in each section to trace where branches were actually attached. Small marks on flat surfaces came together to reveal a three-dimensional plant body.[1]
Time and place
It comes from the Early Devonian Rhynie chert, around 407 million years ago. The locality is in present-day Scotland, UK. It is known for plants, animals, fungi, and microorganisms from a hot-spring ecosystem.[1]
The time range describes source context, not the complete duration of this species.
Size, form and skeleton
Leafy stems, axes producing rooting structures, and axes extending underground are distinguished. Inside the leafy stems is star-shaped branching xylem tissue. We can see where different organs connect within one plant.[1]
The reconstructed height of Asteroxylon presented in the 2021 study is approximately 30 cm. It was a small plant with both aboveground stems and axes extending underground.[9]
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Habitat and reproduction
Stems spreading close to the surface and downward-growing axes pointed in different directions. Researchers compared gravitational orientation and branch connections to interpret the parts growing into the ground. Anchoring structures belowground provide important clues to the lives of early land plants.[1]
Fossil discovery
In 2021, researchers used partially silica-filled voids in the rock as clues to orientation. They then traced branch connections through 31 consecutive sections to reconstruct part of a plant in three dimensions. Even small voids in rock can reveal the directions in which a plant grew upward and downward.[1]
References
- Hetherington et al. (2021) — Asteroxylon reconstructed from serial sections
- Taylor, Kerp & Hass (2005) — Gametophytes and life cycles of early land plants
- Hetherington et al. (2021) — Asteroxylon reconstructed from serial sections
- Study of sporophytes of Rhynie and Windyfield plants
- 2025–2026 study — Conducting tissues of Horneophyton
- International Commission on Stratigraphy (2024) — Geological time chart
- Ashworth(2025-12-18). A 400-million-year-old fossil is revealing how plants grew into giants. Natural History Museum.
- Hetherington et al. (2021) — Asteroxylon reconstructed from serial sections
- Hetherington et al. (2021) — An evidence-based 3D reconstruction of Asteroxylon mackiei, the most complex plant preserved from the Rhynie chert
Research questions
From what kind of body did modern roots arise? Asteroxylon’s rooting axes lacked root hairs and root caps. The researchers interpreted these axes as transitional forms leading toward modern roots, exploring how plant organs changed.[1]
Observation
Follow the slender, downward-pointing axes from the leafy stem. Continuing into the more finely branching underground parts reveals how three kinds of structures connect within one plant.[1]
Related organisms
Aglaophyton majusLand plantsSource time context (not species duration) · ≈ 400 MaEarly land plants of the Rhynie chert
Aglaophyton and Asteroxylon are Early Devonian plants known from the Rhynie chert of present-day Scotland. Examine forked stems and sporangia, small leaves and underground structures separately in each plant to explore an ancient terrestrial ecosystem.
Horneophyton lignieriLand plantsSource time context (not species duration) · ≈ 420–359 MaDifferent plant bodies at Rhynie
Horneophyton and Asteroxylon are known from the Rhynie chert of present-day Scotland. Comparing these two Early Devonian plants highlights the contrast between Horneophyton’s leafless stems and Asteroxylon’s small-leaved stems. Examine the structures anchoring their bodies below as well.