Cycads are seed plants that typically have a stout and woody (ligneous) trunk with a crown of large, hard, stiff, evergreen and (usually) pinnate leaves. The species are dioecious, that is, individual plants of a species are either male or female. Cycads vary in size from having trunks only a few centimeters to several meters tall. They typically grow very slowly and live very long. Because of their superficial resemblance, they are sometimes mistaken for palms or ferns, but they are not closely related to either group.
Gnetophyta is a division of plants, grouped within the gymnosperms, that consists of some 70 species across the three relict genera: Gnetum, Welwitschia, and Ephedra. Fossilized pollen attributed to a close relative of Ephedra has been dated as far back as the Early Cretaceous. Though diverse in the Early Cretaceous, only three families, each containing a single genus, are still alive today. The primary difference between gnetophytes and other gymnosperms is the presence of vessel elements, a system of small tubes (xylem) that transport water within the plant, similar to those found in flowering plants. Because of this, gnetophytes were once thought to be the closest gymnosperm relatives to flowering plants, but more recent molecular studies have brought this hypothesis into question, with many recent phylogenies finding them to be nested within the conifers.
The gymnosperms are a group of seed-producing plants that includes conifers, cycads, Ginkgo, and gnetophytes, forming the clade Gymnospermae. The term gymnosperm comes from the composite word in Greek: γυμνόσπερμος, literally meaning 'naked seeds'. The name is based on the unenclosed condition of their seeds. The non-encased condition of their seeds contrasts with the seeds and ovules of flowering plants (angiosperms), which are enclosed within an ovary. Gymnosperm seeds develop either on the surface of scales or leaves, which are often modified to form cones, or on their own as in yew, Torreya, Ginkgo. Gymnosperm lifecycles involve alternation of generations. They have a dominant diploid sporophyte phase and a reduced haploid gametophyte phase which is dependent on the sporophytic phase. The term "gymnosperm" is often used in paleobotany to refer to all non-angiosperm seed plants. In that case, to specify the modern monophyletic group of gymnosperms, the term Acrogymnospermae is sometimes used.
A tracheid is a long and tapered lignified cell in the xylem of vascular plants. It is a type of conductive cell called a tracheary element. Angiosperms use another type of conductive cell, called vessel elements, to transport water through the xylem. The main functions of tracheid cells are to transport water and inorganic salts, and to provide structural support for trees. There are often pits on the cell walls of tracheids, which allows for water flow between cells. Tracheids are dead at functional maturity and do not have a protoplast. The wood (softwood) of gymnosperms such as pines and other conifers is mainly composed of tracheids. Tracheids are also the main conductive cells in the primary xylem of ferns.
Cycas is a genus of cycad, and the only genus in the family Cycadaceae. About 113 species are accepted, which are native to the Indo-Pacific, East Africa and Madagascar. Cycas circinalis, a species endemic to India, was the first cycad species to be described in western literature, and is the type species of the genus. The best-known Cycas species is Cycas revoluta.
Bennettitales is an extinct order of seed plants that first appeared in the Permian period and became extinct in most areas toward the end of the Cretaceous. Bennettitales were amongst the most common seed plants of the Mesozoic, and had morphologies including shrub and cycad-like forms. The foliage of bennettitaleans is superficially nearly indistinguishable from that of cycads, but they are distinguished from cycads by their more complex flower-like reproductive organs, at least some of which were likely pollinated by insects.
In the geologic timescale, the Valanginian is an age or stage of the Early or Lower Cretaceous. It spans between 139.8 ± 3.0 Ma and 132.6 ± 2.0 Ma. The Valanginian Stage succeeds the Berriasian Stage of the Lower Cretaceous and precedes the Hauterivian Stage of the Lower Cretaceous.
This article attempts to place key plant innovations in a geological context. It concerns itself only with novel adaptations and events that had a major ecological significance, not those that are of solely anthropological interest. The timeline displays a graphical representation of the adaptations; the text attempts to explain the nature and robustness of the evidence.
Schmeissneria is a genus of possible early angiosperms recorded from the Lower Jurassic of Europe and the Middle Jurassic of China, traditionally included in the Ginkgophyta.
The Cretaceous Terrestrial Revolution, also known as the Angiosperm Terrestrial Revolution (ATR) by authors who consider it to have lasted into the Palaeogene, describes the intense floral diversification of flowering plants (angiosperms) and the coevolution of pollinating insects, as well as the subsequent faunal radiation of frugivorous, nectarivorous and insectivorous avians, mammals, lissamphibians and squamate reptiles during the Middle to Late Cretaceous, from around 125 Mya to 80 Mya. Alternatively, according to Michael Benton, the ATR is proposed to have lasted from 100 Ma, when the first highly diverse angiosperm leaf floras are known, to 50 Ma, during the Early Eocene Climatic Optimum, by which point most crown lineages of angiosperms had evolved.
A spermatophyte, also known as a phanerogam or a phaenogam, is any plant that produces seeds, hence the alternative name seed plant. It is a category of embryophyte that includes most of the familiar land plants, including the flowering plants and the gymnosperms, but not ferns, mosses, or algae.
Xingxueanthus is an extinct genus of plants of dubious affinity which existed in China during the middle Jurassic period. It was first named by Xin Wang and Shijun Wang in 2010 and the type species is Xingxueanthus sinensis.
Solaranthus is an extinct genus of plants with contentious affinities which has been found fossilized in the Jiulongshan Formation of China. It dates to the middle Jurassic period. It was first named by Shaolin Zheng and Xin Wang in 2010 and the type species is Solaranthus daohugouensis.
This article records new taxa of plants that are scheduled to be described during the year 2018, as well as other significant discoveries and events related to paleobotany that occurred in the year 2018.
This article records new taxa of fossil plants that are scheduled to be described during the year 2019, as well as other significant discoveries and events related to paleobotany that are scheduled to occur in the year 2019.
This article records new taxa of fossil plants that are scheduled to be described during the year 2020, as well as other significant discoveries and events related to paleobotany that are scheduled to occur in the year 2020.
Pseudoctenis is a genus of fossil foliage attributable to the Cycadales. It is one of the most common genera of cycad fossil foliage in the Mesozoic.
Mesodescolea is a genus of fossil foliage with uncertain affinities from the Early Cretaceous of Argentina and Antarctica. It includes only one species, Mesodescolea plicata.
This paleobotany list records new fossil plant taxa that were to be described during the year 2023, as well as notes other significant paleobotany discoveries and events which occurred during 2023.
The fossil history of flowering plants records the development of flowers and other distinctive structures of the angiosperms, now the dominant group of plants on land. The history is controversial as flowering plants appear in great diversity in the Cretaceous, with scanty and debatable records before that, creating a puzzle for evolutionary biologists that Charles Darwin named an "abominable mystery".
