Macroneuropteris Temporal range: | |
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Macroneuropteris scheuchzeri, specimen from Mazon Creek fossil beds in the collection at the Yale Peabody Museum of Natural History | |
Scientific classification | |
Kingdom: | Plantae |
Clade: | Tracheophytes |
Division: | † Pteridospermatophyta |
Order: | † Medullosales |
Family: | † Neurodontopteridaceae |
Genus: | † Macroneuropteris Cleal et al., 1990 |
Species | |
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Macroneuropteris is a genus of Carboniferous seed plants in the order Medullosales. The genus is best known for the species Macroneuropteris scheuchzeri, a medium-size tree that was common throughout the late Carboniferous Euramerica. Three similar species, M. macrophylla, M. britannica and M. subauriculata are also included in the genus.
The most abundant species of this genus, Macroneuropteris scheuchzeri, has had a long taxonomic history since it was first recognized in fossils found near Oxford, England by Edward Lhuyd in 1669. He referred to these leaves as Phyllites mineralis. It is illustrated and noted in Lhuyd's Lythophylacii Britannici Ichnographia, an early manuscript on English fossils published in 1699 with the financial help of Isaac Newton. [1] [2] The species was further described in the Herbarium Diluvianum written in 1723 by the botanist Johann Jakob Scheuchzer. [3] Nearly hundred years after Scheuchzer's death, the species was renamed Neuropteris scheuchzeri by professor Hoffmann in Christian Keferstein's 1826 atlas of German Geology, Deutschland, geognostisch-geologisch dargestellt. [4] In the 1800s, similar fossilized foliage was found in North America. The names Neuropteris cordata var. angustifolia, Neuropteris angustifolia, Neuropteris acutifolia, Neuropteris hirsuta, Neuropteris decipiens, and Odontopteris subcuneata were used for these but are now all considered to be forms of Macroneuropteris scheuchzeri. The genus was taxonomically refined in 1989 through epidermal research led by C. J. Cleal. Based on that work, the genus Neuropteris was divided into four genera, Neuropteris, Macroneuropteris, Neurocallipteris, and Laveineopteris. [5] [6] [7]
The genus Macroneuropteris is used in some cases as a leaf organ taxon to refer to just the foliage of these trees. And in other cases, it is used to refer to the entire tree. The genus is associated with the stems and trunks of the wood organ taxon Medullosa noei. Together these fossils describe parts of a medullosalean seed fern tree that was likely about 8–10 meters tall with an upright trunk with large compound frond-like leaves.
The foliage of the Macroneuropteris species consists of very large frond-like leaves that are bipartite (divided in two) near the base, forming two large bipinnately compound parts (see illustration). These compound fronds can be as large as several meters. [8]
In Macroneuropteris, each individual leaflet or pinnule of the compound frond were also notably large. In fact, the species M. scheuchzeri's pinnules were the largest of any seed plant of the Carboniferous Period. Individual pinnules are typically lanceolate with a round base. They have been found to be as long as 12 cm. These individual leaflets are often found fossilized by themselves separated from the frond. They have been inferred by some to be deciduous. In the famous Mazon Creek fossil beds of Illinois, these leaflets are one of the most commonly found plant fossils. The leaves have thick cuticles, sunken stomata, dense trichomes, and large hair-like structures. These foliar characteristics combined with the spiny stem structure where the leaflets drop, and the potential deciduous nature have led to many authors suggesting a xeromorphic tendency in the tree. Such adaptations may have allowed the genus to dominate the late Carboniferous landscape as other plants like Lepidodendrales steadily declined. [9] [10]
The presence of hair-like structures on the pinnules of Macroneuropteris has been noted since the mid 1800s. It has become an important taxonomic characteristic particularly for M. scheuchzeri, which has abundant epicuticular hair that can reach a maximum length of 1000 mm. It had been assumed that these were trichomes on the leaves and may have been used to help the plant conserve water. Recent molecular studies by Erwin L. Zodrow have discovered that although there are trichomes on the species of Macroneuropteris, the more noticeable dark 'hair-like' structures are likely not trichomes and may not be directly attached to the leaves. He suggests that these structures are material in the wax of the cuticle demonstrating a dynamic molecular Self-assembly. [11]
The hair-like structures of M. scheuchzeri (1) are not organically attached to the abaxial surface; (2) differ spectrochemically from the organic material of the lamina; (3) are composed, in contrast with the trichomes, of relatively long, unbranched aliphatic (polymythelinic) hydrocarbon chains [CH2]n, and (4) are acellular and black, unlike true trichomes of the species that are multicellular. Overall, the sum-total of these experimental results supports the postulate for dynamic molecular self-assembly. For this reason the term "extracuticular deposit" is proposed, reflecting the origin and emergent nature of such hair-like structures in the abaxial pinnule.
— Erwin L. Zodrow, "Molecular self-assembly: Hypothesized for 'hair' of Macroneuropteris scheuchzeri", International Journal of Coal Geology [12]
Reconstructions of the entire Macroneuropteris trees have been based on various separate fossil parts. As noted above, the stems and trunks are usually referred to as Medullosa noei. Early attempts to reconstruct the entire tree were somewhat limited by this fragmentary material. One well-known reconstruction was illustrated for Stewart and Theodore Delevoryas paper in 1956. The illustration has been the basis for many reconstructions of the Medullosa noei tree. [13]
However, a complete Macroneuropteris tree was found in growth position in Nova Scotia that differs from the idealized reconstruction. This fossil tree was extensively studied by Howard Falcon-Lang who found many characteristics that differed from the previous reconstructions.
The fossil tree has a sharply tapering trunk surrounded in its lower part by a large number of downward-recurved senescent petioles, which form a skirt. Petioles borne in an upright or horizontal position, interpreted as fronds that were still photosynthetically active when buried, are confined to the uppermost preserved part of the tree. Adapted to growth in rapidly aggrading coastal wetlands, the skirt of Macroneuropteris scheuchzeri probably acted to prop up the trunk while additionally trapping large mounds of mud around the base of the tree and stabilizing coastal wetlands. The tree had a sprawling habit and a maximum height of about 2 m. Similar, but smaller, trees found in adjacent beds probably represent juvenile specimens of the same species.
— Howard Falcon-Lang, "A Macroneuropteris scheuchzeri tree preserved in growth position", Atlantic Geology [14]
Seed and pollen organs have not yet been found directly attached to the foliage of Macroneuropteris. For that reason, a variety of fossilized reproductive parts could be possible matches. However, a lot of evidence points toward some type of trigonocarpus as the seed/ovlule and Codonotheca caduca as the male pollen organ.
In 1938, W. A. Bell studied the Sydney Coalfield in Nova Scotia, and suggested that the large fossilized seeds called Trigonocarpus noeggerati could be the ovules of Macroneuropteris scheuchzeri. [15] Erwin Zodrow in 2002 also noted that this ovule fossil was commonly in physical association with M. scheuchzeri foliage. [7] Specimens of Trigonocarpus can be quite large. The largest recorded was 10 cm and has been noted as the largest ovule produced by a non-angiosperm seed-plant. Some have noted that the large size of these seeds may have allowed them to float, like small coconuts, to be distributed in these coastal mangrove-like areas as well as inland wetland forests. [16] Their three-part symmetry gives them their name. A tube-like opening at the top brought pollen into the ovule. Pachytesta is a term that is also used for this type of seed/ovule. [17]
As early a 1903, the fossilized male pollen organs called Codonotheca caduca were speculated to be from plants bearing Macroneuropteris scheuchzeri foliage. [18] In 1907, E.H. Sellards further noted this connection. [19] In the late 1960s, both Laveine (1967) [20] and Darrah (1969) reinforced this association. [21] The pollen found in the fossilized Codonotheca caduca are monolete and exceptionally large (200–550 μm).
The large size of the monolete pollen of Macroneuropteris and other seed ferns suggests that they may not have been well adapted to wind dispersal. This raises speculation about the possibility of insect pollination. [22] One of those possibilities is Arthropleura , a very large millipede of the Carboniferous. Scott and Taylor (1983) studied seed-fern pollen on the plates of Arthropleura and thought they might have a role in pollination. [23] W. A. Shear and others have noted that this is very unlikely due to the size of Arthropleura. [24] Other insects of the Carboniferous however may have been pollinators. The cycads, a modern seed plant with some similar affinities to seed ferns, were previously thought to only be pollinated by wind. New studies have confirmed the role of Thrips and other beetles in their pollination. This form of pollination is now known to be present as far back as the Cretaceous. A similar relationship may have occurred between these seed ferns and some Carboniferous insects. [25]
Macroneuropteris scheuchzeri is a very recognizable species in the Late Carboniferous, and is found throughout what was known as Euramerica, a large supercontinent that included present-day North America, Europe, and northern Africa. M. macrophylla is found in many of the same locations. Because of their similarities, the two are easily misidentified. M. britannica and M. subauriculata are found mostly in Europe. In general, Macroneuropteris had a worldwide distribution over the tropical equatorial world of the late Carboniferous. [7]
The genus ranges from the Bashkirian stage of the Carboniferous to the early Asselian stage of the Permian. A range that is approximately 18 million years (approximately 298 to 316 million years ago). M. scheuchzeri became particularly common in the Moscovian stage. In two Moscovian-age (approximately 309 mya) fossil locations, Mazon Creek fossil beds in Illinois, U.S.A and Okmulgee in Oklahoma, U.S.A., Macroneuropteris is exceptionally abundant. Along with the leaves of Psaronius , it comprises nearly 60% of the flora in these fossil beds. [10] [26]
It is commonly found in the fossils above coal seams. It has been noted that the coal that formed during an evenly wet climate is dominated by lepidodendrales , and the layer above the coal formed during a transitional and more varied climate is dominated by Macroneuropteris and the tree fern Psaronius . The foliar adaptations described earlier in this article may have given Macroneuropteris an advantage during these transitional times.
As Lepidodendrons declined in the late carboniferous, Macroneuropteris continued to be common and even became a dominant element in these forests. An extinction event called the Carboniferous Rainforest Collapse occurred during the Kasimovian stage. This event decimated many of the Lepidodendrons . It also affected Macroneuropteris, however, the genus was able to recover quicker than other species after this event and became a dominant part of a new forest ecosystems alongside the tree fern Psaronius . [27]
Toward the end of the Carboniferous, the climate of Euramerica became increasingly dryer. Macroneuropteris disappeared from the fossil record for the most part. It was limited to isolated wet areas. It continued into the early Asselian stage of the Permian in these isolated locations. [10]
Ginkgoales are a gymnosperm order containing only one extant species: Ginkgo biloba, the ginkgo tree. The order has a long fossil record extending back to the Early Permian around 300 million years ago from fossils found worldwide. The order was a common component of Triassic flora before the super dominance of conifers.
Paleobotany, also spelled as palaeobotany, is the branch of botany dealing with the recovery and identification of plant remains from geological contexts, and their use for the biological reconstruction of past environments (paleogeography), and the evolutionary history of plants, with a bearing upon the evolution of life in general. A synonym is paleophytology. It is a component of paleontology and paleobiology. The prefix palaeo- or paleo- means "ancient, old", and is derived from the Greek adjective παλαιός, palaios. Paleobotany includes the study of terrestrial plant fossils, as well as the study of prehistoric marine photoautotrophs, such as photosynthetic algae, seaweeds or kelp. A closely related field is palynology, which is the study of fossilized and extant spores and pollen.
Archaeopteris is an extinct genus of progymnosperm tree with fern-like leaves. A useful index fossil, this tree is found in strata dating from the Upper Devonian to Lower Carboniferous, the oldest fossils being 385 million years old, and had global distribution.
Pteridospermatophyta, also called "pteridosperms" or "seed ferns" are a polyphyletic grouping of extinct seed-producing plants. The earliest fossil evidence for plants of this type are the lyginopterids of late Devonian age. They flourished particularly during the Carboniferous and Permian periods. Pteridosperms declined during the Mesozoic Era and had mostly disappeared by the end of the Cretaceous Period, though Komlopteris seem to have survived into Eocene times, based on fossil finds in Tasmania.
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.
The Mazon Creek fossil beds are a conservation lagerstätte found near Morris, in Grundy County, Illinois. The fossils are preserved in ironstone concretions, formed approximately 309 million years ago in the mid-Pennsylvanian epoch of the Carboniferous period. These concretions frequently preserve both hard and soft tissues of animal and plant materials, as well as many soft-bodied organisms that do not normally fossilize. The quality, quantity and diversity of fossils in the area, known since the mid-nineteenth century, make the Mazon Creek lagerstätte important to paleontologists attempting to reconstruct the paleoecology of the sites. The locality was declared a National Historic Landmark in 1997.
Dioon is a genus of cycads in the family Zamiaceae. It is native to Mexico and Central America. Their habitats include tropical forests, pine-oak forest, and dry hillsides, canyons and coastal dunes.
Coal forests were the vast swathes of freshwater swamp and riparian forests that covered much of the lands on Earth's tropical regions during the late Carboniferous (Pennsylvanian) and Permian periods. As plant matters from these wetland forests decayed, enormous deposits of peat accumulated, which later became buried and converted into coal over the subsequent geologic eras.
Psaronius is an extinct genus marattialean tree fern which grew to 10m in height, and is associated with leaves of the organ genus Pecopteris and other extinct tree ferns. Originally, Psaronius was a name for the petrified stems, but today the genus is used for the entire tree fern. Psaronius tree fern fossils are found from the Carboniferous through the Permian.
Pecopteris is a very common form genus of leaves. Most Pecopteris leaves and fronds are associated with the marattialean tree fern Psaronius. However, Pecopteris-type foliage also is borne on several filicalean ferns, and at least one seed fern. Pecopteris first appeared in the Devonian period, but flourished in the Carboniferous, especially the Pennsylvanian. Plants bearing these leaves became extinct in the Permian period, due to swamps disappearing and temperatures on Earth dropping.
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.
The Allegheny Group, often termed the Allegheny Formation, is a Pennsylvanian-age geological unit in the Appalachian Plateau. It is a major coal-bearing unit in the eastern United States, extending through western and central Pennsylvania, western Maryland and West Virginia, and southeastern Ohio. Fossils of fishes such as Bandringa are known from the Kittaning Formation, which is part of the Allegheny Group.
The Medullosales is an extinct order of pteridospermous seed plants characterised by large ovules with circular cross-section and a vascularised nucellus, complex pollen-organs, stems and rachides with a dissected stele, and frond-like leaves. Their nearest still-living relatives are the cycads.
The Lyginopteridales are an extinct group of seed plants known from the Paleozoic. 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.
Neuropteris is an extinct seed fern that existed in the Carboniferous period, known only from fossils.
Myriacantherpestes is an extinct genus of spiny millipedes from the Pennsylvanian subperiod of the Carboniferous period, known from fossils in Europe and North America.
Callistophytales is an extinct order of spermatophytes which lived from the Pennsylvanian to Permian periods. They were mainly scrambling and lianescent (vine-like) plants found in the wetland "coal swamps" of Euramerica and Cathaysia. Like many other early spermatophytes, they could be described as "seed ferns", combining ovule-based reproduction with pinnate leaves superficially similar to modern ferns.
The Callistophytaceae was a family of seed ferns (pteridosperms) from the Carboniferous and Permian periods. They first appeared in late Middle Pennsylvanian (Moscovian) times, 306.5–311.7 million years ago (Ma) in the tropical coal forests of Euramerica, and became an important component of Late Pennsylvanian vegetation of clastic soils and some peat soils. The best known callistophyte was documented from Late Pennsylvanian coal ball petrifactions in North America.
Emplectopteridaceae is an extinct family of pteridosperms known mainly from Permian floras of the Cathaysian Realm. They were mostly shrubby plants with a scrambling or upright habit, and favoured a range of habitats from arid to moist or even aquatic.
Asterotheca is a genus of seedless, spore-bearing, vascularized ferns dating from the Carboniferous of the Paleozoic to the Triassic of the Mesozoic.
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