Evolution and relationships of the conifer seed cone telemachus: Evidence from the triassic of antarctica

The seed cone Telemachus is known from several Triassic localities in Gondwana. New specimens from two localities in Antarctica provide additional information about the type species, Telemachus elongatus, based on details of morphology and anatomy revealed by using a modified transfer technique on the compressed plants. Seed cones of T. elongatus are up to 6.0 cm long and characterized by conspicuous, elongate bracts. A second Antarctic species, described here as Telemachus antarcticus, is segregated, based on a shorter bract and differences in cone size. Newly recognized features of the genus include the shape, size, and disposition of the ovules; vascularization of the ovuliferous complex; and scale and bract histology. As a result of this new information, it is now possible to compare Telemachus with the permineralized Middle Triassic conifer seed cone Parasciadopitys from the Central Transantarctic Mountains. The similarities between the two genera make it possible to relate organs in different preservational modes and to develop a more complete concept for this widely distributed Gondwana conifer. Placing the Telemachus plant within a phylogenetic context makes it possible to evaluate the relationship with other so-called transitional conifers, an informal group that has been interpreted as intermediate between Paleozoic and modern conifers.Fil: Escapa, Ignacio Hernán. University of Kansas; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Decombeix, Anne-Laure. University of Kansas; Estados UnidosFil: Taylor, Edith L.. University of Kansas; Estados UnidosFil: Taylor, Thomas N.. University of Kansas; Estados Unido

Lonchiphyllum aplospermum gen. et sp. nov.: An Anatomically Preserved Glossopterid Megasporophyll from the Upper Permian of Skaar Ridge, Transantarctic Mountains, Antarctica

A new anatomically preserved megasporophyll, Lonchiphyllum aplospermum, is described from permineralized peat collected on Skaar Ridge in the central Transantarctic Mountains. This new genus contains vascular features similar to those of the leaf genus Glossopteris schopfii, which is the exclusive leaf genus in the specimens in which the sporophylls were found. The vasculature of the sporophyll consists of a central vascular region with bordered pitting and anastomosing lateral bundles with helical-scalariform thickenings. Ovules are attached oppositely to suboppositely to lateral veins on the adaxial surface of the sporophyll. There is an abundance of bisaccate pollen of the Protohaploxypinus type at the base of the ovules. The ovules of Lonchiphyllum are small (1.1 mm × 0.97 mm) and ovate and have an unornamented integument. Comparison with anatomically known ovules from Skaar Ridge, i.e., Plectilospermum elliotii, Choanostoma verruculosum, and Lakkosia kerasata and Homevaleia gouldii from the Bowen Basin of Australia, supports the classification of Lonchiphyllum as a glossopterid. The differences in the sarcotesta and sclerotesta of all the Skaar Ridge ovules may indicate specialization for pollination or dispersal

Secondary Growth in Vertebraria Roots from the Late Permian of Antarctica: A Change in Developmental Timing

This is the publisher's version, also available electronically from http://www.jstor.org/stable/10.1086/597784.Permineralized Vertebraria roots from the late Permian of the Central Transantarctic Mountains, Antarctica, are investigated to understand the unusual vascular anatomy of the genus. The specimens range from ∼1 mm to several centimeters in diameter and illustrate all the stages of secondary growth. Our observations confirm previous hypotheses on the development of these roots and suggest that their unique anatomy is the result of a change in developmental timing. Vertebraria is characterized by a vascular cambium that remains discontinuous through several growth seasons, leading to the formation of lacunae alternating in cross section with wedges of secondary vascular tissues. The bifacial nature of the cambium is confirmed by the presence of well‐developed secondary phloem composed of longitudinally elongated cells and uniseriate parenchymatous rays. In some of the largest specimens, a continuous vascular cylinder is formed by the differentiation of cambium from parenchymatous cells bordering the lacunae. The new specimens provide additional information on the secondary xylem anatomy and vascular connection to lateral roots

Epicormic Schoots in a Permian Gymnosperm from Antarctica

This is the publisher's version. Shared with permission, it is also available electronically from: http://dx.doi.org/10.1086/654849Two anatomically preserved gymnosperm trunks with clusters of epicormic shoots are described from the Late Permian of Antarctica. The best-preserved trunk is 14 cm long. It has a small circular parenchymatous pith and 9 cm of secondary xylem that contains at least 50 growth rings. The second specimen is slightly smaller (11 3 8 cm) and has 20 growth rings. Both specimens have pycnoxylic wood and produced more than 50 small shoots in a delimited zone on the surface of the trunk. Shoots have a wide parenchymatous pith that may be solid to septate with endarch primary xylem forming 8–10 sympodia and a small amount of secondary xylem similar to that of the parent trunk. The shoots branch and increase in number toward the outside of the trunk. Evidence based on anatomical comparisons and association at the site indicates that the specimens probably represent trunks of some glossopterid, the dominant group of seed ferns during the Permian in Gondwana. This is the first report of clusters of epicormic shoots in a Paleozoic gymnosperm. The ability to produce a large number of young shoots that were capable of developing into new branches indicates that these high-latitude trees possessed an architectural plasticity that allowed them to respond quickly to short- or longterm environmental stress

Dordrechtites Arcanus Sp. Nov., An Anatomically Preserved Gymnospermous Reproductive Structure From the Middle Triassic of Antarctica

This is the publisher's version of an article which is being shared with permission. The original version may be accessed at: http://dx.doi.org/10.1086/668792The genus Dordrechtites is an isolated ovulate structure previously described only from South Africa and Australia as impressions. The discovery of compressed and permineralized specimens of this taxon at the base of Mount Falla (uppermost Fremouw Formation) in the central Transantarctic Mountains extends the geographical and geological distribution of the genus and increases the known floral diversity of the Triassic of Antarctica. The first permineralized species, Dordrechtites arcanus, is described using standard acetate peel techniques and includes internal anatomy of an elongate arm that extends over the top of a central cupule containing two elongate, bilaterally symmetrical, orthotropous ovules. An arc-shaped collateral vascular bundle extends from the arm into the top of the cupule, branches, and then extends around the ovule to about halfway down to the micropylar end. The cupule is parenchymatous and includes transfusion tissue with cells that have pitted walls. The sclerotesta of the ovule is up to 200 mm thick, consisting of an outer layer with longitudinally oriented, thick-walled cells and an inner layer one cell thick of rectangular, thick-walled cells. The micropyle is flared at the attenuated tip of the pyramidal cupule. The four previously described species of Dordrechtites have uncertain affinities, and although the morphology and anatomy of this taxon is now known, the affinities within the gymnosperms are still uncertain

The First Permineralized Microsporophyll of the Glossopteridales: Eretmonia macloughlinii sp. nov.

This is the publisher's version, which has been made available with permission of the publisher. The original version may be found at the following link: http://dx.doi.org/10.1086/666667Eretmonia du Toit is a microsporophyll genus attributed to the Permian Glossopteridales. Microsporophylls are scale leaves (smaller leaves with morphology similar to that of Glossopteris leaves) that bear clusters of sporangia at the end of stalks attached to the petiole of the sporophyll. Late Permian permineralized specimens of Eretmonia from the central Transantarctic Mountains in Antarctica reveal the first anatomical information of the genus. Numerous veins run the length of the petiole and alternate with large canals/air spaces; the veins and canals are separated by increasing amounts of parenchyma. The ground tissue of the leaves is composed of isodiametric parenchyma of varying diameters. Beneath the epidermis is a hypodermis two to three layers thick. Pollen sac walls are a single layer thick with a tapered apex and bulbous base. The simplicity of the bisaccate pollen grains does not suggest a specialized form of pollination but rather that the glossopterids were wind pollinated

Macrofossil Evidence For Pleuromeialean Lycophytes From the Triassic of Antarctica

This is the publisher's version, which is also available electronically from: http://dx.doi.org/10.4202/app.2010.0022Triassic microfloras from Antarctica contain abundant lycophyte spores. However, macrofossils of this group of plants are missing, and thus the precise affinities of the spore producers remain unknown. Macrofossil remains of a pleuro− meialean lycophyte, including an incomplete strobilus, isolated sporophylls and sporangia, as well as abundant mega− spores, occur on a single rock sample from the central Transantarctic Mountains. Also occurring on the same surface is Mesenteriophyllum serratum, a strap−shaped leaf morphotype of uncertain affinity previously known only from the Kyrgyz Republic and the Taimyr Peninsula. The leaves display alternating transverse ridges and depressions that are sim− ilar to structures seen in compressed leaves of various isoetalean lycophytes. Leaf morphology and anatomy, together with the close association of the other lycophyte remains, suggest that M. serratum represents a pleuromeialean lycophyte leaf, which was part of the same plant that produced the sporophylls and sporangia. Sedimentological data indicate that this lycophyte inhabited a swampy, probably coal−forming overbank environment, which contrasts with the assumed xero− to halophytic habit of many other pleuromeialean lycophytes

The Possible Pollen Cone of the Late Triassic Conifer Heidiphyllum/Telemachus (Voltziales) From Antarctica

This is the publisher's version, which is being used with permission. The original article may be found at: http://dx.doi.org/10.1017/S0954102011000241Fossil leaves of the Voltziales, an ancestral group of conifers, rank among the most common plant fossils in the Triassic of Gondwana. Even though the foliage taxon Heidiphyllum has been known for more than 150 years, our knowledge of the reproductive organs of these conifers still remains very incomplete. Seed cones assigned to Telemachus have become increasingly well understood in recent decades, but the pollen cones belonging to these Mesozoic conifers are rare. In this contribution we describe the first compression material of a voltzialean pollen cone from Upper Triassic strata of the Transantarctic Mountains. The cone can be assigned to Switzianthus Anderson & Anderson, a genus that was previously assumed to belong to an enigmatic group of pteridosperms from the Triassic Molteno Formation of South Africa. The similarities of cuticle and pollen morphology, together with co-occurrence at all known localities, indicate that Switzianthus most probably represents the pollen organ of the ubiquitous Heidiphyllum/Telemachus plant

Structurally preserved fungi from Antarctica: diversity and interactions in late Palaeozoic and Mesozoic polar forest ecosystems

Chert and silicified wood from the Permian through Cretaceous of Antarctica contain abundant information on fungal diversity and plant-fungal interactions. The chert deposits represent a particularly interesting setting for the study of plant-fungal interactions because they preserve remains of distinctive high latitude forest ecosystems with polar light regimes that underwent a profound climate change from icehouse to greenhouse conditions. Moreover, some of the cherts and wood show the predominance of extinct groups of seed plants (e.g. Glossopteridales, Corystospermales). Over the past 30 years, documentation of fossil fungi from Antarctica has shifted from a by-product of plant descriptive studies to a focused research effort. This paper critically reviews the published record of fungi and fungal associations and interactions in the late Palaeozoic and Mesozoic cherts and silicified wood from Antarctica;certain fungal palynomorphs and fungal remains associated with adpression fossils and cuticles are also considered. Evidence of mutualistic (mycorrhizal), parasitic and saprotrophic fungi associated with plant roots, stems, leaves and reproductive organs is presented, together with fungi occurring within the peat matrix and animal-fungus interactions. Special attention is paid to the morphology of the fungi, their systematic position and features that can be used to infer fungal nutritional modes

Cycads from the Triassic of Antarctica: Permineralized Cycad Leaves

Permineralized cycad petioles and/or rachides with associated pinnae are described from two Triassic localities in the Queen Alexandria Range, central Transantarctic Mountains, Antarctica. Petiole‐rachides display an inverted‐omega‐shaped arrangement of vascular bundles typical of most genera of extant Cycadales and exarch primary xylem that link them to the modern order. Pinnae associated with the Antarctic petiole‐rachides are thin, with regularly spaced vascular bundles. They are similar to those of extant Zamia and most other genera of extant Cycadales, whose pinnae lack midribs. Other Mesozoic fossil cycads (e.g., Charmorgia, Lyssoxylon, Lioxylon) have endarch petiole vascular bundles that in some cases were previously considered more similar to those of Bennettitales than those of Cycadales. We suggest, however, that the endarch xylem of these taxa is typical of Cycadales because in extant cycads, the protoxylem changes from endarch to exarch within the base of the petiole. Evolution of cycad leaf form is reviewed based on evidence from the fossil record