| Pentoxylales Temporal range: | |
|---|---|
Scientific classification  | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Spermatophytes |
| Order: | † Pentoxylales Pilger and Melchior, 1954 |
| Genera | |
| |
| Synonyms | |
Pentoxyleae Sahni, 1948 | |
Pentoxylales is an extinct order of seed plants known from the Jurassic and Early Cretaceous of East Gondwana.
The first specimens belonging to Pentoxylales were reported by Birbal Sahni in 1948 from Jurassic-Cretaceous strata of the Rajmahal Hills of northeastern India. Remains have subsequently been reported from New Zealand, Australia and Antarctica. [1] The oldest records of the group date to the Upper Jurassic, though there are unconfirmed Early Jurassic records. [2]
The stem of Pentoxylales, referred to by the morphogenus Pentoxylon , consists of 5 or 6 wedge shaped segments embedded within thin walled ground tissue. [1]
Leaves of Pentoxylales are of the strap shaped Taenopteris morphotype shared with other groups of seed plants, while leaves that preserve the cuticle are referred to the morphogenus Nipaniophyllum. The leaves are up to 20 centimetres long, and have a prominent midrib. [1]
The pollen organs of Pentoxylales, referred to the morphogenus Sahnia, consist of microsporophylls arranged in tight spirals around or on a cylindrical or dome-shaped receptacle. The base of the pollen organs are surrounded by bracts up to 6 mm long. The pollen is monosulcate and approximately 25 µm long. [1]
Seed bearing organs of Pentoxylales, dubbed Carnoconites , which have a central axis or peduncle, which branches into numerous structures that end with an ovule. The morphology has variously been described as infructescences, seed cones, seed-bearing fruits, or female flowers. The seeds are apparently sessile. [1]
The habit of Pentoxylales is uncertain. They have been suggested to have been small trees. [1] Their liana-like anatomy has also led to suggestions of a habit similar to that of brambles. [3]
The affinities of Pentoxylales remain obscure, phylogenetic analyses have proposed various affinities with other seed plants groups, including glossopterids and Bennettitales, but evidence for this is inconclusive, and they cannot be definitively linked with any other seed plant group. [1]
Ginkgoales are a gymnosperm order containing only one extant species: Ginkgo biloba, the ginkgo tree. It is monotypic, within the class Ginkgoopsida, which itself is monotypic within the division Ginkgophyta. The order includes five families, of which only Ginkgoaceae remains extant.
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 conduits 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.
The gymnosperms are a group of seed-producing plants that includes conifers, cycads, Ginkgo, and gnetophytes, forming the clade Gymnospermae, the living members of which are also known as Acrogymnospermae. 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 solitary 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.
Araucaria is a genus of evergreen coniferous trees in the family Araucariaceae. There are 20 extant species in New Caledonia, Norfolk Island, eastern Australia, New Guinea, East Argentina, South Brazil, Chile and Paraguay.
The South Polar region of the Cretaceous comprised the continent of East Gondwana–modern day Australia and Antarctica–a product of the break-up of Gondwana in the Cretaceous Period. The southern region, during this time, was much warmer than it is today, ranging from perhaps 4–8 °C (39–46 °F) in the latest Cretaceous Maastrichtian in what is now southeastern Australia. This prevented permanent ice sheets from developing and fostered polar forests, which were largely dominated by conifers, cycads, and ferns, and relied on a temperate climate and heavy rainfall. Major fossil-bearing geological formations that record this area are: the Santa Marta and Sobral Formations of Seymour Island off the Antarctic Peninsula; the Snow Hill Island, Lopez de Bertodano, and the Hidden Lake Formations on James Ross Island also off the Antarctic Peninsula; and the Eumeralla and Wonthaggi Formations in Australia.
Glossopteris [etymology: from Ancient Greek γλῶσσα + πτερίς ] is the largest and best-known genus of the extinct Permian order of seed ferns known as Glossopteridales. The genus Glossopteris refers only to leaves, within a framework of form genera used in paleobotany. Species of Glossopteris were the dominant trees of the middle- to high-latitude lowland vegetation across the supercontinent Gondwana during the Permian Period. Glossopteris fossils were critical in recognizing former connections between the various fragments of Gondwana: South America, Africa, India, Australia, New Zealand, and Antarctica.
Bennettitales is an extinct order of seed plants that first appeared in the Triassic period and became extinct in most areas toward the end of the Cretaceous. Bennettitales are among the most common Mesozoic seed plants, 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.
Williamsonia is a genus of plant belonging to Bennettitales, an extinct order of seed plants. Within the form classification system used in paleobotany, Williamsonia is used to refer to the female seed cones, which are associated with plants that also bore the male flower-like reproductive structure Weltrichia. Plants associated with this reproductive structure include the cycad-like Williamsonia sewardiana from the Early Cretaceous of India, as well as the woody shrub Kimuriella densifolia from the Late Jurassic of Japan.
Archaeamphora longicervia is a fossil plant species, the only member of the genus Archaeamphora. Fossil material assigned to this taxon originates from the Yixian Formation of northeastern China, dated to the Early Cretaceous.
This page provides a glossary of plant morphology. Botanists and other biologists who study plant morphology use a number of different terms to classify and identify plant organs and parts that can be observed using no more than a handheld magnifying lens. This page provides help in understanding the numerous other pages describing plants by their various taxa. The accompanying page—Plant morphology—provides an overview of the science of the external form of plants. There is also an alphabetical list: Glossary of botanical terms. In contrast, this page deals with botanical terms in a systematic manner, with some illustrations, and organized by plant anatomy and function in plant physiology.
Ginkgo is a genus of non-flowering seed plants. The scientific name is also used as the English name. The order to which it belongs, Ginkgoales, first appeared in the Permian, 270 million years ago, and is now the only living genus within the order. The rate of evolution within the genus has been slow, and almost all its species had become extinct by the end of the Pliocene. The sole surviving species, Ginkgo biloba is only found in the wild in China, but is cultivated around the world. The relationships between ginkgos and other groups of plants are not fully resolved.
This glossary of botanical terms is a list of definitions of terms and concepts relevant to botany and plants in general. Terms of plant morphology are included here as well as at the more specific Glossary of plant morphology and Glossary of leaf morphology. For other related terms, see Glossary of phytopathology and List of Latin and Greek words commonly used in systematic names.
The Caytoniales are an extinct order of seed plants known from fossils collected throughout the Mesozoic Era, around 252 to 66 million years ago. They are regarded as seed ferns because they are seed-bearing plants with fern-like leaves. Although at one time considered angiosperms because of their berry-like cupules, that hypothesis was later disproven. Nevertheless, some authorities consider them likely ancestors or close relatives of angiosperms. The origin of angiosperms remains unclear, and they cannot be linked with any known seed plants groups with certainty.
Sagenopteris is a genus of extinct seed ferns from the Triassic to late Early Cretaceous.
The Lyginopteridales were the archetypal pteridosperms: They were the first plant fossils to be described as pteridosperms and, thus, the group on which the concept of pteridosperms was first developed; they are the stratigraphically oldest-known pteridosperms, occurring first in late Devonian strata; and they have the most primitive features, most notably in the structure of their ovules. They probably evolved from a group of Late Devonian progymnosperms known as the Aneurophytales, which had large, compound frond-like leaves. The Lyginopteridales became the most abundant group of pteridosperms during Mississippian times, and included both trees and smaller plants. During early and most of middle Pennsylvanian times the Medullosales took over as the more important of the larger pteridosperms but the Lyginopteridales continued to flourish as climbing (lianescent) and scrambling plants. However, later in Middle Pennsylvanian times the Lyginopteridales went into serious decline, probably being out-competed by the Callistophytales that occupied similar ecological niches but had more sophisticated reproductive strategies. A few species continued into Late Pennsylvanian times, and in Cathaysia and east equatorial Gondwana they persisted into the Late Permian, but subsequently became extinct. Most evidence of the Lyginopteridales suggests that they grew in tropical latitudes of the time, in North America, Europe and China.
Dicroidium is an extinct genus of fork-leaved seed ferns that were widely distributed over Gondwana during the Triassic. Their fossils are known from South Africa, the Arabian Peninsula, Australia, New Zealand, South America, Madagascar, the Indian subcontinent and Antarctica. They were first discovered in Triassic sediments of Tasmania by Morris in 1845. Fossils from the Umm Irna Formation in Jordan and in Pakistan indicate that these plants already existed in Late Permian. Late surviving members of the genus are known from the Early Jurassic (Sinemurian) of East Antarctica. Within paleobotany, Dicroidium is a form genus used to refers to the leaves, associated with ovuluate organs classified as Umkomasia and pollen organs classified as Pteruchus, while Dicroidum is also used collectively to refer to the whole plant.
Umkomasia is a genus of seed bearing organs produced by corystosperm seed ferns, first based on fossils collected by Hamshaw Thomas from the Burnera Waterfall locality near the Umkomaas River of South Africa. He recognized on the basis of cuticular similarities that the same plant produced pollen organs Pteruchus and the leaves Dicroidium. Various other corystosperm seed bearing organs from the Jurassic and Cretaceous have been assigned to this genus, but recently have been given distinct genera, with Umkomasia being restricted to the Triassic.
Pteruchus is a form genus for pollen organs of the seed fern (Pteridospermatophyta family Umkomasiaceae. It was first described by Hamshaw Thomas from the Umkomaas locality of South Africa. It is associated with the seed bearing organs Umkomasia and Dicroidium leaves.
Corystospermaceae is a natural family of seed ferns (Pteridospermatophyta) also called Umkomasiaceae, and first based on fossils collected by Hamshaw Thomas from the Burnera Waterfall locality near the Umkomaas River of South Africa The leaves of Dicroidium were recognized by Alex Du Toit to unite all the countries of the Gondwana supercontinent during the Triassic: Africa, South America, India, and Australia. Subsequently, Dicroidium was found in the Triassic of Antarctica and New Zealand, and also the Permian Umm Irna Formation of Jordan. According to the form generic system of paleobotany, leaves are given separate generic names to ovulate and pollen organs, but the discovery of these reproductive organs in Africa by Thomas, and subsequently throughout Gondwana, strengthened Du Toit's concept of a continuous southern supercontinent. Corystospermaceae were also components of Jurassic and Cretaceous floras, declining in the Cretaceous presumably due to the rise of flowering plants, the last known representative of the group, Komlopteris cenozoicus, is known from the Eocene of Tasmania, at least 13 million years after the Cretaceous–Paleogene extinction event.
Podozamites is an extinct genus of fossil conifer leaves. In its broader sense, it has been used as a morphogenus to refer to any broad leaved multi-veined conifer leaves. Modern broad-leaved conifers with a similar form include kauri and Nageia, and some Podozamitessensu lato probaby belong to the same families.