Calamopityales
| Calamopityales | ||||||||||||
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| Lower carbon | ||||||||||||
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North America, Europe |
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| Scientific name | ||||||||||||
| Calamopityales | ||||||||||||
The Calamopityales are an order of the extinct plant group of the seed ferns . It consists of five genera.
features
The order is only known through wood fossils, seeds, pollen organs or leaves are unknown.
The wood is manoxylic, so it has plenty of parenchyma , especially in the bark. Outside there is sclerenchyme . Calamopitys comprise slender stems that range from protosteles with abundant parenchyma to eusteles. The xylem is mesarchic: the protoxylem is in the middle of the metaxylem, the maturation of the xylem occurs from the middle inwards and outwards. The leaf marks pull through several nodes before bending into a petiole. The secondary phloem , if present, consists of alternating bands of parenchyma and sieve cells .
Calamopitys americana is relatively common and a typical representative of the order. The trunk diameter is up to four centimeters, the length is unknown. In the center of the trunk there is a mixed marrow of parenchyma and tracheids , the parenchyma predominating in terms of quantity. It is triangular in cross section and consists of five Mesarchic xylem branches. Around this medulla is a broad zone of radially arranged secondary xylem with numerous multiseriate parenchymal rays . The rays are 1 to 12 cells wide and different heights. The cortex is parenchymatic and contains sclerenchymatic plates on the outside. The leaves were in 2/5 phyllotaxis on the stems. The leaf marks arise individually and branch out into four bundles in the base of the petiole. These bundles lack the secondary xylem. The other species of the genus, such as Calamopitys foersteri and Calamopitys saturnii, have different arrangements in the pith and different numbers of leaf traces.
Stenomyelon is widely regarded as the genus with the most primitive characteristics. Stenomyelon tuedianum from the sand-lime stone (Lower Carboniferous) of Great Britain has a protostele that is divided into three approximately equal parts by thin parenchymal plates . The tracheids of the metaxylem have multi-row court pits . The secondary xylem is similar to that of the other representatives of the order. The leaf stalks are in 2/5 phyllotaxis. There are multicellular surface structures on the stem surface. In the case of stenomyelon heterangioides , groups of parenchymal cells also interrupt the xylem of the protostele. Stenomyelon primaevum has a three-lobed protostele without parenchyma, the leaf traces divide several times into mostly eight bundles. In stenomyelon bifasciculare , the leaf marks arise from the ribs of the stele.
Diichnia kentuckiensis from the New Albany Shale has a pentagonal stele with mixed pith , the primary xylem is in the ends of the pentagon. Characteristic of the genus is the double leaf trace, which arises from two neighboring xylem lobes.
Galtieria , also from the New Albany Shale, has a three-ribbed protostele like stenomyelon . The secondary xylem around the protostele contains tracheids with elliptical pits and one- to two-cell rays that are up to 30 cells high. The secondary phloem is characterized by tangential bands of macrosklereids . In the bark of Galteria bostoniensis there are a large number of sclerotic nests, a hallmark of many seed ferns.
Bostonia perplexa , also from the New Albany Shale, is only known from one 3 cm long and 2.1 cm wide specimen, in which the outer trunk areas are missing.
Kalymma is a common genus and includes leaf stalks. The types are differentiated according to the distribution and shape of the vascular bundles, the degree of fusion of neighboring vascular bundles, and the presence or absence of secretion canals. The leaf forks near the base in two parts. Kalymma tuediana possibly belongs to the Stenomyelon tuedianum tribe , the petiole has a diameter of around one centimeter and usually contains nine vascular bundles (protoxylem outside).
The leaf genera Diplothmema and Sphenopteridium are discussed as belonging to Stenomyelon leaves, since they occur in the same layers as.
In the case of Chapelia, it is unclear whether it is a stem axis or a petiole. The cross-section shows a four-lobed protostele with a mesarchic xylem, which is surrounded by a manoxylic secondary xylem. The cortex contains secretory cells and groups of (likely) fibers.
distribution
The Calamopityales are only known from the Lower Carboniferous . There are only finds from North America and Europe.
Systematic position
The systematic position of the Calamopityales is uncertain due to the lack of reproductive organs. The known genera show important transition stages in the evolution of the Eustele. They correspond to a series that leads to the Eustele such as Lyginopteris : starting from the stenomyelon , the massive protostele dissolves through the insertion of parenchyma.
The Aneurophytales ( Progymnospermae ) are discussed as ancestors of the Calamopityales .
supporting documents
- Thomas N. Taylor, Edith L. Taylor: The Biology and Evolution of Fossil Plants . Prentice Hall, Englewood Cliffs 1993, pp. 487-492. ISBN 0-13-651589-4