Sigillaria

Sigillaria sp.

The Sigillariaceae are a family of mainly tree- growing, extinct Bärlapppflanzen that were part of the Carboniferous coal swamps. Known fossils of this family are known as signet trees strains of the genus Sigillaria.

Features

The characterizing features ( synapomorphies ) that distinguish the Sigillariaceae from the other families of the order are: the leaf traces arise from two protoxylem strands; the periderm contains bands of " resinous " cell assemblies; in the periderm, there are massive Parichnos strands; each sheet is supplied by two xylem strands forming a paired, the central beam; on the leaf adaxial there is one located in the middle of the pit; the ornaments of the microspores are spiny- conical. Characteristics that divides the family with each other members of the order are: the PTO shafts or coniferous side branches sit on the main stem; the periderm is " resinous "; the ratio of leaf cushion height to width is 1:1 or less on lateral branches; on the leaf there are paired abaxial mines.

Vegetative characteristics

The Sigillariaceae are treelike plants, branched little and only distally, and smaller than the related Lepidodendraceae. Most members remained high under 20 m, although individual specimens were about 30 m high. A characteristic feature of the leaf bases that are in outline hexagonal, rarely elliptic, and have led to the name " Seal tree". They are arranged spirally on the stem, but often seem to stand in vertical rows. The actual leaf scar is usually elliptical, in the middle sits the leaf - trace scar, which is flanked by two large Parichnos scars. The vascular bundles is V-shaped, sometimes split into two strands. About the Journal scar sits the stigma of the ligule.

The Sigillariaceae had leaves only at the ends of the stem axis, where they were tight. The leaves were long. The leaves are partially crossed by two laterally flattened vascular bundles. This feature distinguishes the leaf - genera Sigillariophyllum and Sigillariopsis by representatives of Lepidodendraceae while they were otherwise quite similar. There are two longitudinal furrows, which are occupied with conspicuous trichomes on the lower leaf surface. The stomata are arranged in rows, the companion cells are sunken. Cyperites is a form for the genus found isolated sheets of about 1 cm in width and Schmetterlingsförmigem or X - shaped cross section.

During compression fossils are very common from the Carboniferous, structurally preserved Stems are quite rare. The center of the tribe consists of parenchyma marrow, which is surrounded by a continuous band of primary xylem. In cross section, the outer edge of the exarch primary xylem appear wavy, wherein the leaf traces arise in the furrows. The tracheids of Metaxylems have Fimbrillen between the bars of the ladder-like beams. There is little secondary xylem formed, consisting of Leitertracheiden and narrow rays. The distribution of cortical tissue is similar to the related genus Diaphorodendron tangentially banded periderm often occurs. The periderm is concentric bands of find - probably - secretory cells. Radially through the periderm pull pairs of cylindrical or laterally flattened strands of Parichnos fabric. It is with the Parichnos scars of leaf bases in conjunction and possibly acted as a ventilation tissue.

Fossils in debarked state are summarized in the form genus Syringodendron. Its surface shows vertical rows of large, often double elliptical scars that resemble rabbit tracks. These are Parichnos strands in tangential section.

The underground organs of Sigillariaceae are substantially similar to the Stigmariae the other Lepidodendrales, but there are some anatomical differences. The marrow is relatively narrow compared to the diameter of the stele. It consists of an inner zone of pure parenchyma and an outer zone where parenchyma and tracheids occur together. The bark is relatively small and consists of two primary areas. The secondary growth of the bark by two concentric rings of meristem in the outer bark. The form genus Stigmariopsis includes underground organs that are assigned to the subgenus Subsigillaria. They differ from Stigmariae by their unequal branch, the smaller side branch points downward.

Reproductive organs

Sigillaria was heterosporous, ie produced spores of unequal size. The cones were monosporangiat however, so constituted only one of the two spore types. The cones were between the leaf bases.

Mazocarpon oedipternum the late Pennsylvanian of North America consists of pins with a diameter of 1.2 cm and a length of common 10 cm. The sporophylls are arranged in a flat screw or Pseudowirteln. The distal end of sporophyll is rather short. The Megasporangien are roughly triangular, they contain a central parenchymatous pad, which is surrounded by eight megaspores. The megaspores are large and trilet ( have a three-rayed scar ). From its proximal suture protrude Archegonia short necks.

The microspore- bearing cones, also placed in the genus Mazocarpon containing trilete spores of approximately 60 micrometers in diameter. Mazocarpon villosum from the late Pennsylvanian has a diameter of 2.2 cm.

For several species, the megagametophyte are known. They consist of prothallia fabric and rhizoids, archegonia are their is 65 microns in size with three layers of cervical cells.

In its reproduction, the Sigillariaceae were quite diverse with three ways of mega spore propagation:

• The spores developed rapidly and were discharged from the sporangium. Representative is Mazocarpon villosum.
• The sporophylls remaining to maturity on the pin, the mega spores are scattered when the sporangium breaks. Representative is about Mazocarpon oedipternum.
• The megaspores were spread with their sporophylls by the pins fell apart. Representatives are Mazocarpon pettycurense and Mazocarpon cashii.

Sigillariostrobus are compression fossils of cones of up to 30 cm in length. You are likely to be another form of conservation Mazocarpon.

System

The Sigillariaceae are the sister group to the group Lepidodendraceae Diaphorodendraceae.

For the systematic structure within the genus Sigillaria shape and arrangement of leaf bases were used. The following sub- genera and sections:

• Sigillaria subg. Eusigillaria has ribbed stem surfaces. In the section of the leaf Rhytidolepis base and the ribs are separated, the grooves between adjacent ribs are straight or almost straight.
• In the section Favularia leaf bases and ribs are close together, the grooves are zigzag.

• Section Leiodermaria has far apart standing vertical rows of leaf scars without lofty leaf pads.
• In the section Clathraria the leaf bases are close together.

Temporal and spatial distribution

The Sigillariaceae had their heyday in the late Pennsylvanian. They grew in swamp areas near that were slightly drier than the locations of the other tree-shaped Bärlapppflanzen.

Documents

• William A. DiMichele, Richard M. Bateman: The Rhizomorphic Lycopsids: A Case- Study in Paleobotanical Classification. Systematic Botany, 1996, Vol 21, pp. 535-552.
• Thomas N. Taylor, Edith L. Taylor, Michael Krings: Paleobotany. The Biology and Evolution of Fossil Plants. Second Edition, Academic Press 2009, ISBN 978-0-12-373972-8. Pp. 303-307.

• Extinct plant
• Bärlapppflanzen
• Lycopodiopsida