Land plant classification

A classification of land plants is given in Table 12.1. Informal groupings are used in this scheme. As an artificial classification it provides a working description of plant diversity rather than an explanation of the evolutionary relationships. Some of the groups are unnatural, for example "seed ferns" incorporates the seed plants that are not included in the other groups.

Land plants are separated into those with a vascular system and those without. There are three important groups of non-vascular plants, all of which are extant: the hornworts, liverworts, and mosses. Vascular plants are separated into seedless and seeded plants. Seedless vascular plants include three extinct groups, and three groups with living relatives: club mosses, ferns, and horsetails. Vascular seeded plants are divided into plants with naked seeds, the gymnosperms, and plants with seeds enclosed by a fruit, the angiosperms. The most important groups of gymnosperms are the conifers, cycads, and ginkgoes. Angiosperms are the flowering plants, the dominant living flora.

Table 12.1 Plant classification, based on common morphological characteristics and not common lineage. These are the most useful groupings for fossil plants.

Description

Example

Range

Non-vascular plants

Anthocerophytes (hornworts)

Hepatophytes (liverworts)

Bryophytes (mosses)

Similar to liverworts but sporangia are able grow continuously

Small plants with a flattened leaf-like body (thallus)

Filamentous mat with simple leaves and root-like structures (rhizoids)

Early Devonian-Recent

Late Devonian-Recent

Carboniferous-Recent

Vascular seedless plants

Rhyniophytes (Cooksonia)

Extinct plants with dichotomously branched, simple axes. Sporangia are terminal

Silurian-early Devonian

Lycophytes (club mosses)

Leafy plants with sporangia on the upper surface of leaves or at the leaf-stem intersect

Late Silurian-Recent

Zosterophylls (Sawdonia)

Extinct dichotomously branched plants, sometimes with spiny axes. Sporangia on the side of axes

Early-late Devonian

Progymnosperms (Archaeopteris)

Extinct fern-like plants with woody tissue

Mid-Upper Devonian

Description

Example

Range

Vascular seedless plants (cont'd)

Pteridophytes (ferns)

Sphenophytes (horsetails)

Large-leaved plants with sporangia on the lower surface

Plants with leaves and branches fused in whorls. Fertile branches have terminal cones

Mid-Devonian-Recent

Late Devonian-Recent

Vascular seeded plants: gymnosperms

Seed ferns Fern-like plants with spores on the leaves

Late Devonian-Jurassic

Conifers

Woody trees with needle or scale-like leaves. Seeds in cones

Early Carboniferous-Recent

Cycads

Bennettitales (Cycadeoidea)

Ginkgoales (ginkgoes)

Gnetales (gnetae)

Woody, stemmed plants with palm- or fern-like leaves and cones

Extinct plants that resemble cycads but have flower-like cones

Woody trees with fan-shaped leaves. Cones absent

Unusual group with cone clusters resembling flowers

Early Carboniferous-Recent

Triassic-late Cretaceous

Late Triassic-Recent

Late Triassic-Recent

Vascular seeded plants: angiosperms

Angiosperms Plants with flowers. Seeds enclosed

(flowering plants) within a fruit

Cretaceous-Recent

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Responses

  • hiwet
    Why are bryophytes and angiosperms excluded from plant fossil classification?
    2 months ago

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