Acritarchs are organic microfossils, known from approximately 1800 million years ago to the present. The classification is a catch all term used to refer to any organic microfossils that cannot be assigned to other groups. Their diversity reflects major ecological events such as the appearance of predation and the Cambrian explosion.
The zosterophylls are a group of extinct land plants that first appeared in the Silurian period. The taxon was first established by Banks in 1968 as the subdivision Zosterophyllophytina; they have since also been treated as the division Zosterophyllophyta or Zosterophyta and the class or plesion Zosterophyllopsida or Zosteropsida. They were among the first vascular plants in the fossil record, and had a world-wide distribution. They were probably stem-group lycophytes, forming a sister group to the ancestors of the living lycophytes. By the late Silurian a diverse assemblage of species existed, examples of which have been found fossilised in what is now Bathurst Island in Arctic Canada.
Cryptospores are microscopic fossilized spores produced by embryophytes. They first appear in the fossil record during the middle of the Ordovician period, as the oldest fossil evidence for the colonization of land by plants. A similar category is miospores, a term generally used for spores smaller than 200 μm. Both cryptospores and miospores are types of palynomorphs.
Prototaxites is an extinct genus of terrestrial fossil fungi dating from the Late Silurian until the Late Devonian periods. Prototaxites formed large trunk-like structures up to 1 metre (3 ft) wide, reaching 8 metres (26 ft) in length, made up of interwoven tubes around 50 micrometres (0.0020 in) in diameter, making it by far the largest land-dwelling organism of its time.
Tortilicaulis is a moss-like plant known from fossils recovered from southern Britain, spanning the Silurian-Devonian boundary. Originally recovered from the Downtonian of the Welsh borderlands, Tortilicaulis has since been recovered in the famous Ludlow Lane locality.
Nematothallus is a form genus comprising cuticle-like fossils. Some of its constituents likely represent red algae, whereas others resemble lichens.
Aglaophyton major was the sporophyte generation of a diplohaplontic, pre-vascular, axial, free-sporing land plant of the Lower Devonian. It had anatomical features intermediate between those of the bryophytes and vascular plants or tracheophytes.
Rhynia is a single-species genus of Devonian vascular plants. Rhynia gwynne-vaughanii was the sporophyte generation of a vascular, axial, free-sporing diplohaplontic embryophytic land plant of the Early Devonian that had anatomical features more advanced than those of the bryophytes. Rhynia gwynne-vaughanii was a member of a sister group to all other eutracheophytes, including modern vascular plants.
Pertica is a genus of extinct vascular plants of the Early to Middle Devonian. It has been placed in the "trimerophytes", a strongly paraphyletic group of early members of the lineage leading to modern ferns and seed plants.
Hostinella is a form genus, used for bare dichotomously branching stems (axes) which have not been found in association with spore-forming organs or sporangia and so cannot be assigned to a more precise genus or species. Specimens assigned to this genus have been found in Bathurst Island, Canada, in the Bertie Formation of Upper Silurian age, where the stems are approximately 1.2 mm in diameter; and in Lower Devonian Senni beds where the axes have a straited external appearance and contain xylem with tracheids.
Krithodeophyton is a genus of lower Devonian plant with branching axes. It is considered to be a barinophyte.
Salopella is a form genus for small fossil plants of Late Silurian to Early Devonian age. The diagnostic characters are naked axes branching isotomously, terminating in fusiform sporangia. The sporangia are unbranched, but in at least the type species the axes seem to branch just under the sporangia. It differs from the similar form genus Tortilicaulis in that the sporangia do not have spirally arranged cells, and from other similar form genera such as Cooksonia, Uskiella and Tarrantia in the shape of the sporangia.
Renalia is a genus of extinct vascular plants from the Early Devonian. It was first described in 1976 from compressed fossils in the Battery Point Formation. It is difficult to reconstruct the original form of the complete plant, but it appears to have consisted of leafless branching stems whose side branches had sporangia at their tips. It is regarded as an early relative of the lycophytes.
Eogaspesiea was a genus of Early Devonian rhyniophyte with a tangled mess of branching axes that reached 10 cm in length. These probably emanated from a rhizome. Its (probably) alete spores had thin walls.
Foozia was a genus of vascular Emsian land plant with a main axis and a number of branches that sub-divide at most once. Some of these bear oval to semicircular sporangia containing Dibolisporites echinaceus, whereas the sterile branches may represent an early foray into leaf-formation. The only known fossils herald from Belgium. It is currently unclassified.
Catenalis is a genus of extinct plants of the Early Devonian. Fossils were first found in the Posongchong Formation of eastern Yunnan, China. The leafless stems (axes) bore 10-12 elliptical spore-forming organs or sporangia on side branches. To release their spores, the sporangia split at the opposite end to their attachment to the stem. Its phylogenetic relationship to other land plants is considered uncertain at present.
Psilophytites is a form genus of extinct plants; it was created by Høeg for spiny stems (axes) which cannot be assigned to a more precise genus or species, usually because spore-forming organs or sporangia are not present.
Tortotubus is an early terrestrial fungus. Its growth trajectory can be ascertained from its fossils, which occur across the globe from the Ordovician to the Devonian. These fossils document foraging activities of slender, cell-wide exploratory hyphae; when these hit a source of food, they produced secondary branches that grew back down the original filament, covered themselves with an envelope, and served as pipes to shuttle nutrients to other parts of the organism. Today, mycelium with this growth pattern is observed in the mushroom-forming fungi.
The barinophytes are a group of extinct vascular plants (tracheophytes). Their relationship with other vascular plants is unclear. They have been treated as the separate class Barinophytopsida, the order Barinophytales of uncertain class and as a family or clade Barinophytaceae within the zosterophylls. They have also been considered to be possible lycopodiopsids.
Yeaia is an extinct genus of brown algae known from the Silurian and Devonian of southern hemisphere locations.
