Aspects of Gondwana paleobotany: gymnosperms of the Paleozoic—Mesozoic transition

ELSEVIER Review of Palaeobotany and Palynology 90 (1996) 287-302

PAlf&BOrANY

PALYNOLOGY

Aspects of Gondwana paleobotany: gymnosperms of the Paleozoic-Mesozoic transition

Sergio Archangelsky

Divisih Paleobothica, Museo Argentino de Ciencim Naturales “B. Rivadavia”, Av. A. Gallardo 470, (1405) Buenos Aires, Argentina

Received 9 October 1994; revised and accepted 1 December 1994

Abstract

During the late Paleozoic and early Mesozoic the Gondwana Supercontinent underwent dramatic geographic and climatic changes. Geologic and biologic factors concurrently played an important role modelhng the vegetation of that time. The gymnospermic component of plant assemblages shows significant variations in composition and in the distribution of different taxa. Analysis of the assemblages shows that some plant groups dominated the scenario, such as the pteridospenns, glossopterids, corystosperms and, to a lesser degree, cordaites and conifers. Ginkgophytes, hennettites or cycacls were less important in the Paleozoic but their numbers increased in the Triassic. Paleozoic assemblages were extensively dominated by glossopterids that hecame extinct in the earliest Mesozoic. Pteridosperms crossed the P-M barrier and hecame dominant during the Triassic, at a time when corystosperms evolved and radiated. Other groups hecame extinct in the Paleozoic, namely dicranophylls and corclaites. Conifers were represented by different families, restricted either to the Paleozoic or the Mesozoic. They were not conspicuous in the andysed assemblages. In some areas of Gondwana, taxa of the Euramerican alliance are present through a migrational mechanism that occurred during continental displacements which produced global climatic changes. Recent studies have shown that there are far more common elements between Euramerica and Gondwana than suspected up to now. These elements find their distribution especially in the western part of Gondwana (Africa-South America).

1. Introduction

For tbe purpose of this paper I shall consider three time segments, namely the Carboniferous, Permian and Triassic, in a broad context, in order to avoid biostratigrapbic discussion on boundaries. In this time frame the Gondwana Supercontinent was a paleogeographic unit, composed of a main block and isolated terranes that fused to the main body during the late Paleozoic (Fig. 1). Gondwana shifted translatitudinally at a variable speed during that time and reached sta- bility in the early Mesozoic. The southern pole occupied different positions while continents

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shifted. Africa was severely affected by the polar ice cap, especially during the Carboniferous and earliest Permian.

Gondwanan late Paleozoic-early Mesozoic seed plants are important components of two informal phytostratigraphic units called the Glossopteris and Dicroidium “floras”. These two genera (and other gymnospermous taxa that belong to the same groups) were widely distributed over the supercontinent during the Permian and Triassic. A Carboniferous pre-Glossopteris (sometimes called “Rhacopteris”) “flora” is also known in some regions of Gondwana.

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Fig. 1. Continent disposition during the transition between the Palemoic and Mesozoic (Late Permian, Kazanian) (after Scotese and McKerrow, 19%).

In order to present a picture of the Gondwana seed-plants in the very broad context of their development during the Paleozoic-Mesozoic transition, an important aspect has to be clarified. We must assume that the exploration and search for fossil plants in Gondwana is still in a very early stage. For instance, how much of the African territory has been conveniently explored? Contributions by several workers (e.g. Seward, Du Toit, Walton, Hamshaw Thomas, Lacey, Townrow, Plumstead, Anderson) relate only to a part of South Africa. Our paleobotanical knowledge is therefore biased because it can be reason- ably assumed that a large number of fossils still await discovery. If marginal territories, such as northern Africa, northern South America or the Himalayas, are included in the “big” Gondwana Supercontinent, then the vastness of this problem attains unsuspected dimensions.

2. Composition of plant assemblages

Comparison of plant assemblages found in different areas of Gondwana shows that their components were similar or indeed identical.

The earliest pre-Glossopterfi Carbonifeous floras include pteridophylls comparable to paleoequatorial taxa; they are mostly impressions of sterile fronds, such as Eusphenopteris (C&sari et al., 1988; Fig. Za), Diplothmema bodenbenderi (Kurt@ CCsari (Sessarego and CCsari, 1989), Nothorhacopteris argentinica (Kurt@ Archangelsky (Archangelsky, 1983), and i’?z$hyllopteris cuyana (Leguizamon and Vega, 1991; Fig. 2b). Nothorhacopteris is a widespread fossil in Gondwana, known in India, Australia, South Africa and South America. It seems to be restricted to Late Carboniferous strata and is a zone-fossil in some regions. Although there is undoubtedly morphological resemblance to fronds found in the paleoequatorial belt, the lack of fructtications or permineralizations ham- pers any speculations on phylogenetic relationships. However, specimens of Nothorhacopteris argentinica have been recently found in Argentina with attached fertile cupule-like bodies, strongly resembling paleoequatorial seed-ferns (Vega and Archangelsky, 1996.). A case of impression fossils with fertile bodies, either in close association or in organic attachment, is that of Diplothmema bodenbenderi (Kurtz) C&sari found in Late

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b

Fig. 2. (a) Eusphenopferis. Schematic reconstruction of frond ramiiication (RI-R,=five rachis cathegories) (after C%sari et al., 1988). (b) l’KphyNopteris cuyana Leguizam6n and Vega, x 0.35. Outline of pinnae at the medial portion of the frond (from Leguizam6n and Vega, 1991). (c) Obandotheca lamine~~~is Erwin, Pfefferkorn and Alleman. Reconstruction of the microsporangiate branch system, x 4 (after Erwin et al., 1994). (d) Oclloa cesariana Erwin, Pfefferkom and Alleman. Reconstruction of a seed, x 7 (after Erwin et al., 1994).

Carboniferous sediments of the Paganzo Basin in Argentina. It shows a single seed-like structure comparable to Genomosperma kihtonii Long pos- sibly connected to the frond. However, details of the morphology and organic connection are not clear (Fauque et al., 1989). From the Paracas peninsula in Peru, Erwin et al. ( 1994) described Oclloa, a pteridosperm ovulate fructification, resembling the northern Physostoma (Fig. 2d), associated to Obandotheca, a microsporangiate branch system similar to Zimmermannitheca (Fig. 2~). This non-cupulate female organ of basal Late Carboniferous age may either have been derived from cupulate ancestors (via reduction or cupule loss) or may have originated from a different evolutionary lineage retaining a primitive seed morphotype (without a cupule). Erwin et al.

concluded that Oclloa is the first positive evidence that hydrasperman reproduction may be found in both cupulate and acupulate ovules, in other words that the presence of a hydrasperman pollen cham- ber is not necessarily to be correlated with the presence of a cupule.

Some other cases of impressions with fructifications attached to vegetative leaves are also known. Fedekurtzia, a frond reported from some Gondwanic areas, has small spike-like structures attached to a rachis that also bears sterile pin&es. This fertile structure has several small sporangium- like bodies of a similar size. No spores were found. This Late Carboniferous fossil has some morphological features that suggest its relation to the Progymnospermopsida, such as type and disposition of sporangia and the helical insertion/bilateral

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disposition of pinnate leaves. It has been suggested that Fedekurtzia may be near the Archaeopteridales (Archangelsky, 198 1) . Another pinnate frond of a wide Gondwanic distribution, Botrychiopsis Kurtz (Rigby, 1989), has been found associated with male fructifications in Late Carboniferous strata of the Paganzo Basin in Argentina. Fructifications are pinnate with microsporophylls borne in clusters on ultimate branches. The sporophylls contain monocolpate grains (Artabe et al., 1987). A different type of a probable male fructification has been found in the Permian of South Africa associated to Botrychiopsis leaves (Anderson and Anderson, 1985). It consists of a central axis bearing spirally arranged microsporophylls with distal sporangia. No pollen was reported. The morphology of Botrychiopsis and the microsporangiate fiuctification suggest that it was a pteridosperm. For the moment it can be assumed that Botrychiopsis probably belonged to an ancestral stock from which Mesozoic plants, perhaps corystosperms, evolved.

Triassic floras of Gondwana were dominated by the Dicroidium plant, based on occurrences in India (Bose et al., 1990), Australia (Retallack, 1977), South Africa (Anderson and Anderson, 1983, 1989), South America (Petriella, 1981), and Antarctica (Pigg and Taylor, 1990). Several years ago it was suggested that a trunk with a liana-like anatomy known as Rhexoxylon, found in South Africa and South America, probably was the stem of Dicroidium (Archangelsky, 1968; Petriella, 198 1). However, Dicroidium-type fronds also occur in other areas of Gondwana where this kind of stem is unknown (Fig. 3a).

Recent data from Antarctica have shown that stems with a different (= not Rhexoxylon) structure may also be related to Dicroidium leaves (Meyer- Berthaud et al., 1993), namely Kykloxylon.

Kykloxylon/Dicroidium and Rhexoxylon/Dic- roidium are examples of plants that have similar frond types borne on trunks with a different anatomy. This may be explained by contrasting paleo- ecological conditions and different paleoclimatic settings. It has been suggested that the Rhexoxylon structure is characteristic of western Gondwana, i.e. South Africa and South America, while Kykloxylon and other wood types are found in

eastern Gondwana (Meyer-Berthaud et al., 1993). This hypothesis takes paleophytogeographic differentiation into consideration.

Corystosperms were a varied and rapidly evolv- ing group during the Triassic, as shown by the morphological changes of their organs. For instance, the variation in the shape of leaves is remarkable, a fact that has led to numerous generic names. Some authors tried to significantly reduce this number arguing that morphological variation of “pinnules” may occur in one leaf, as was for instance illustrated by Anderson and Anderson (1983) who suggested that leaves having Dicroidium, Xylopteris and Johnstonia pinnules in the same specimen represent anomalies or hybrids. There are now at least half a dozen leaf genera among the corystosperms. Little is known about male or female fructiflcations in this group since they are rather similar in all Gondwanic regions in which they occur. Female organs are pinnate rachises bearing inverted cupulate (?) ovules known as Umkomasia, while Pteruchus is the male pinnate organ with distal expanded heads bearing microsporophylls that contain bisaccate pollen grains. They look similar to the male organs associated to Botrychiopsis. Stachyopitys is another male fructification found in South Africa, that resembles Botrychiopsis (Anderson and Anderson, 1989). Other isolated male and female fructifications were found associated to Dicroidium fronds and related to the corystosperms. This is the case for Nidiostrobus (a pollen cone) and Nidia (an ovulate cone) from the Triassic of India (Bose and Srivastava, 1973). However, there are alter- native interpretations for these organs (Meyen, 1984).

Did corystosperms evolve from a Botrychiopsis- like plant? There is a stratigraphic continuity, since Botrychiopsis is known from Late Carboniferous and Permian sediments of Gondwana while corystosperms are found in Triassic strata of the same region. Some morphological frond characters and the few known fructiflcations are comparable. On the other hand, there are similarities between corystosperms and cycads in some anatomical features of bundle organization and arrangement in the pinnate frond petioles (Pigg and Taylor, 1990). This configuration is different from the

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Fig. 3. (a) Zuberia zuberi Frenguelli. Reconstruction of a frond. Approximately l/6 of the natural size (from Petriella, 1978). (b) @xiIopteris madagascarensis Carpentier. Schematic reconstruction of the frond, x l/2 (from Anderson and Anderson, 1989). (c) Scyrophylhun neuburgiunum Dobruskina. Reconstruction of the frond, x l/5 (from Zamuner and Artabe, 1990). (d,e) Dejerseya lunensis (Johnston) Anderson and Anderson. Two specimens that show shape variation, x l/2 (from Anderson and Anderson, 1989).

northern Paleozoic seed ferns (calamopityans, lygi- nopterids, Cullistophyton and medullosans). The Rhexoxylon anatomical structure has also been compared to some advanced medullosans (Archangelsky and Brett, 1961). The present paleobotanical information to clarify relationships among the northern pteridosperms and the late Paleozoic forms assigned to this group in Gondwana and the Mesozoic corystosperms is not sufhcient. Yet, it is useful as a first approach to an exciting phylogenetic possibility. The comparative study of frond architecture in these groups may

help to resolve this problem. It proved to be useful with Northern Hemisphere fronds (Laveine, 1993).

Cupulate Triassic organs recently found in Antarctica have been referred to a new form order, the Petriellales (Taylor et al., 1994), based on the permineralized multiovulate cupules produced singly on a short dichotomizing axis. Although associated with Dicroidium leaves, Petriellaea has different anatomical characters suggesting it was related to another leaf organ. This new finding confIrms the significance that seed ferns had in Gondwana during the Triassic.

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Peltasperms are abundant in the Triassic strata of Gondwana, though some species are also known in the Northern Hemisphere. Fronds referred to Lepidopteris (Fig. 3b) and Scytophyllum (Fig. 3c) are found in Europe and in Gondwana (Townrow, 1960; Dobruskina, 1969; Bose et al., 1990; Zamuner and Artabe, 1990). The female peltate fructification (Peltuspermum) and the male microsporangiate organ containing monocolpate pollen (Antevsia) occur mostly in South Africa (Anderson and Anderson, 1989). Recently, Poort and Kerp ( 1990) have broadened the definition of the genus Peltaspermum in order to include all assembled organs.

Gymnosperm fronds of uncertain afhnities are common in Gondwana. An example is Dejerseya Herbst (Fig. 3d,e), a remarkable leaf found in Australia and South Africa (Anderson and Anderson, 1989). This putative seed fern has entire to frond-shaped leaves. When pinnules develop they are markedly heterogeneous over the same pinna. This plant was probably undergoing morphological changes. This condition of “unstable morphology”, was common during the Triassic (see the Dicroidium, Xylopteris, Johnstonia case).

Glossoperids in the widest sense represent the typical component of Gondwana floras (Fig. 4). The extreme variety in the shape and structure of leaves, including impressions (Chandra and Surange, 1979), compressions (Pant and Singh, 1974) and permineralizations (Pigg, 1990) and the total paleogeographical coverage of the huge supercontinent co&m the power of adaptation these plants had during the Permian. There is no cotident record of a glossopterid leaf in pre- Permian strata (I am not considering the eventual Carboniferous ancestors from the paleoequatorial region, as Lesleyu; see Leary, 1993). During the Permian glossopterid leaves show two general tendencies: (1) the gangamopterid type of venation is more frequently encountered in the lower levels of the stratigraphic successions, and (2) the glossopterid venation is simple at the lower stratigraphic levels and becomes more complicated towards the Upper Permian. This type of leaf crossed the Paleozoic-Mesozoic boundary and is found in Triassic strata of Gondwana. Glossopteris (or other similar taxa) was also found in “northern” floras.

These Late Permian and Mesozoic records may correspond to coincident morphology (parallelism) rather than natural relationship.

The underground portion of this plant recorded in all Gondwanic regions was a root of a peculiar vertebrate structure (Vertebruria; Fig. 4a). It is assumed and figured in all reconstructions that leaves were borne on trees with branches (Gould and Delevoryas, 1977; Fig. 4a). Recently it was demonstrated that Glossopteris leaves are attached to stems (up to 12 mm in diameter) with a broad pith and picnoxylic wood of the Araucarioxylon type (Pigg and Taylor, 1993; Taylor, 1996&s issue). This, however, is not a definite proof of an arborescent habit for all glossoperids. Taking into consideration the vast area that these plants covered, the different climates and ecological conditions in which they lived, it is reasonable to consider that glossopterids represented a most variable spectrum in Gondwanan plant communities. Their habits may have been arborescent, as testified by a great variety of permineralized logs having an Araucarioxylon type of wood known in all Gondwana, especially during the Permian. But under bad ecological conditions (e.g. an extremely cold climate), their size may have been smaller and the underground organs large. In this regard, the study of different paleosols may give a good clue to define the type of rooting systems of trunks with araucarioid structures.

Permineralizations of glossopterid fertile organs have been found in Australia and Antarctica. Gould and Delevoryas (1977) have shown that the female structures are enrolled megasporophylls bearing ovoid sessile seeds (Fig. 4b). This organization was further confirmed by the finding in Antarctica of megasporophylls with erect seeds on one side (Taylor, 1987, 1996&s issue). Both, bilateral and radial symmetry occur in glossopterid seeds (Taylor and Taylor, 1993), an important fact to underscore because platyspermic seed impressions are common in Gondwana and they are usually referred to Cordaitales. Several ovulate glossopterid organs are known. Some are attached to the main leaf rachis while others are found isolated. There are uniovulate and pluriovulate types in single or compound structures confirming a great morphological variety similar to that found

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Fig. 4. (a) Reconstruction of a Gfossopterti plant to show the branching, trunk and rooting (Vertebraria) system. (b) Seed-bearing structure and a seed. (c) Pollen-bearing organ and pollen. (All from Gould and Delevoryas, 1977.)

in leaves. Impressions and compressions of these fructifications have been interpreted in different ways. At present it is d8icult to have a clear picture of the relations that these structures had. Male organs though not as common as the female strut tures are also varied in their morphology (Fig. 4c). They are usually composed of microsporangiate clusters and have bisaccate and striate pollen grains, or more rarely monocolpate (Pant and Nautiyal, 1960; Surange and Maheshwari, 1970).

Glossopterids have been related to different plant groups: angiosperms, cordaitales, pteridosperms, and conifers, among others. They possess characteristics that, if taken alone, may suggest a relationship with any of these groups. If taken together, they are certainly gymnosperms, perhaps related to pteridosperms but having characters of their own. Some authors have suggested a separate class (Archangelsky, 1970), the Glossop- teridopsida, at the same rank as the Pterido- spermopsida. Others are inclined to relate them to the seed ferns at the same rank as the Medullosales or Lyginopteridales (Taylor and Taylor, 1993). The angiospermous ancestry is a possibility that attracted several paleobotanists. Taylor and Taylor

(1992) demonstrated that glossoperids had seeds adaxially attached to megasporophylls and showed the megagametophyte development. They concluded that glossopterids had a gymnospermous reproductive biology, enhancing their classification among the seed ferns.

It seems that glossopterids survived until the Triassic and became extinct during this period. The evidence is provided by the finding of glossopterid and other similar leaves that may have belonged to the group, e.g. Yabeiella. However, no fructifications are known.

There are a few records of Cycadales (and putative Bennettitales) from Gondwana during the late Paleozoic. Leaves of Pseudoctenis and Pterophylhun are known from several Permian formations of India (Bose et al., 1990). Kashmiropteris is another leaf found in the Early Permian of India that in shape resembles living members of the cycads (Kapoor et al., 1992). However, fertile organs or permineralizations that belong to these two orders are not known from Gondwana. Other leaves found in the Permian of India were related to the Cycadales, i.e. Macro- taeniopteris, Rhabdotaenia and Pteronilssonia.

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Triassic permineralized cycadean trunks are known from South America (Archangelsky and Brett, 1963) and Antarctica (Smoot et al., 1985). The characteristic manoxylic stelar organization and stem anatomy leave no doubt about their botanical affinity. Putative cycadean leaves, such as Linguifolium, Pseudoctenis (Fig. 5b,c), Jeanjacquesia, Moltenia, Rhabdotaenia, Rewa- phyllum, Godpadia, etc., have been reported in the Triassic of most Gondwanic areas. Other leaves, such as Taeniopteris and Ptilophyllum, have also been reported for Gondwana (Anderson and Anderson, 1989). These leaves may show great morphological variation over the same specimen.

Ginkgophytes are known in Permian strata through impressions of leaves that resemble the extant Ginkgo foliage. Ginkgoites is one of such leaves known from Permian and Triassic sediments of Gondwana (Cuneo, 1987; Anderson and Anderson, 1985; Bajpai, 1991). The similarity between fossil and extant leaves is constant during the Mesozoic and Tertiary. It is a good example of morphological stasis, should these leaves prove to really represent Ginkgoales. The same applies to other Triassic leaves referred to this order, such as Baiera, Sphenobaiera (Fig. Sd,e), Ginkgophyllum and Ginkgophytopsis, that are widely distributed over all of Gondwana. Probably primitive Ginkgoales were important components of plant communities during the Paleozoic-Mesozoic transition.

Plants related to the Dicranophyllales, an order so far only known from the Northern Hemisphere, were found in Permian strata of South America. This order has two families, one of which, the Dicranophyllaceae, occurs with sterile and fertile organs (Archangelsky and Cuneo, 1990). Polyspermophyllum was a plant with long linear leaves that repeatedly dichotomized and had curved single ovules placed distally on leaves of identical shape as the sterile foliage (Fig. 5a). This foliage is known to occur in different paleofloristic

regions in late Paleozoic rocks and is usually referred to the genera Ginkgophyllum and Dicranophyllum. One hypothesis suggests that Polyspermophyllum was probably a descendant of an earlier group of primitive plants as the Archaeopteridales or the Callistophytales (Taylor and Taylor, 1993) of the Equatorial Belt. In this case Polyspermophyllum represents another possible link between floras of both realms. Probably, this ginkgophytic lineage persisted during the Triassic because abundant leaves of a similar con- struction occur widely (e.g. Sphenobaiera, Baiera).

The pinnate female organ Arberia is usually related to the glossopterids. However, it is also found associated to leaves of the Ginkgophyllum type in the Permian of South America and may be a member of the ginkgophytic line (Archangelsky and Cuneo, 1990). The fructification Arberia is also associated with leaves referred to CordaitesJNoeggerathiopsis. On this basis, it was suggested that perhaps this plant (Arberiafcordaites), was probably the precursor of the glossopterids (Maheshwari and Srivastava, 1992).

In Gondwana (and in other continents of that time) there are a number of sterile leaves that are included in a group of putative ginkgophytes, namely Psygmophyllum, Rhipidopsis, Gondwano- phyton, Saportaea, Chiropteris, etc.

Cordaites (al. Noeggerathiopsis) foliage included in the order Cordaitales, is widely distributed in Carboniferous and Permian plant assemblages throughout Gondwana. Sometimes it dominates these assemblages, suggesting that the group adapted to the varied paleoclimatic conditions that prevailed over this vast supercontinent. Cordaicarpus and Samaropsis seeds are commonly found in the same beds with Cordaites leaves or in seed-banks. The cuticle of the leaves is known (Pant and Verma, 1964) and it has been suggested that differences between both genera (Cordaites and Noeggerathiopsis) are minimal. No fertile

Fig. 5. (a) Polyspermophyllum sergii S. Archangelsky and aneo. Reconstruction of the distal branches bearing sterile and fertile leaves, x 3 (after Archangelsky and CXneo, 1990). (b) Psudoctenis harringtoniana Bonetti, and (c) Pseudoctenis jssa DuToit. Reconstruction of two pinnate leaves, x l/2 (from Anderson and Anderson, 1989). (d) Sphenobaiera stormbergensis (Seward) Frenguelli and (e) Sphenobaiera insecta Anderson and Anderson. Two leaves to show shape variation, x l/2 (from Anderson and Anderson, 1989).


II b

e

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organs have been found that could convincingly be related to the leaves, impeding a closer approach to the study of relationships with paleoequatorial or Angaran representatives of this order. Rigby (1984) described leaf scars of cordaitalean stems from the Permian of Australia finding differences with the scars described from branches found in Euramerican floras. Monosaccate pollen characteristic of this group also occurs in Gondwana, especially during the Late Carboniferous and Early Permian. A close microscopical study of the pollen reveals that most genera differ from those found in Euramerica. Thorough studies on Gondwanan monosaccate pollen are needed, especially with regard to its abundance in strata as old as the Early Carboniferous. There are no reliable records of Cordaitales in Triassic strata of Gondwana.

Present-day conifers found in the former components of Gondwana are related to their mid- late Mesozoic ancestors; this is the case for the Podocarpaceae and Araucariaceae. More- over, exctinct Mesozoic families such as the Cheirolepidiaceae were cosmopolitan and dominant in Gondwanan plant communities. Noteworthy is the usually poor representation of conifers in Paleozoic and early Mesozoic sediments. Perhaps the scarce data reflect our lack of knowledge on the characterization of this group, and especially its earliest representatives. We are probably faced with a sensu-strict0 or a sensu-lato definition, with regard to the conifer female organs that may be either compact cones bearing ovules and related structures (bracts, scales) or lax cones bearing megasporophylls of a varied organization. Gondwana early conifers may be focused with either of these detiitions.

Sterile shoots bearing small leaves in a helical disposition similar to the Euramerican Walchiaceae, occur in the latest Carboniferous of Gondwana (probably equivalent to the European Stephanian). The description of the cuticle of these leaves and the different branching system allowed Florin (1940a) to establish the genus Purunocludus. In Gondwana these twigs usually occur in Permian rocks. Female and male cones, organically attached to leafy twigs of the Paranocladus type, were found recently in Patagonia. They have a coniferous type of cone organization though with minor differences with European female structures.

The new family Ferugliocladaceae is characterized by female cones bearing compact, helically disposed orthotropous ovules and apparently free bracts on a central axis (Archangelsky and Ctineo, 1987; Fig. 6a). Male cones, also organically attached to the leafy twigs are small compact structures with helically disposed microsporophylls. Pollen is monosaccate of the Cuheniasaccites type. Other probable members of the Ferugliocladaceae have been reported for Late Carboniferous rocks of the Paganzo basin in South America. They consist of impressions of sterile twigs referable to Krauselcladus bearing attached compact cones (Arrondo et al., 1987).

The family Buriadiaceae (Pant, 1982) includes genera that have a wide Gondwanic distribution, namely Buriadia and Genoites. Pant and Nautiyal (1967) described fertile specimens of Buriudia from the Early Permian of India. The leaves are linear, simple or forked and the fertile part of the shoots bear laterally attached, solitary and stalked, inverted ovules (Fig. 6k). Pollen found inside the ovules is monocolpate. Genoites was referred to the same family. The South American specimens have heteromorphic helically arranged linear leaves that are distally dichotomous. Fertile parts are distal on shoots composed of shortly pedunculate orthotropous ovules placed axillary to normal leaves (Umeo, 1985). Whether this family belongs to the conifers depends on the definition of the group. In any case, the Buriadiaceae played an important role during the Permian in Gondwana.

The conifer genus Voltziopsis PotoniC is known from the Late Permian and Early Triassic of South Africa and Australia. Sterile foliage is of the Pagiophyllum type while attached compact female cones are similar in all the species that have been described. The cones are placed distally on branches; they bear long narrow forked bracts and cone scales expanding distally into five lobes. Each lobe bears an inverted ovule (Townrow, 1967a; Anderson and Anderson, 1989; Fig. 6b-d). This plant is placed in the family Voltziaceae which has Euramerican representatives.

Sterile twigs with coniferous leaves of the Pagiophyllum-type occur in the Permian of South Africa (Anderson and Anderson, 1985) and the Triassic of India and Antarctica (Bose et al., 1990). Searsoliu is another Permian conifer described for

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e

h

Fig. 6. (a) Ferugliocladus patagonim (Feruglio) S. Archangel&y and Ctieo. Reconstruction of seed-cones attached to leafy twigs, x 1 (after Archangel&y and Ctieo, 1987). (b-d) Voltziopsb woiganensis Townrow; (b) seed-cone, x 1; (c) bract-scale complex, x 5; (d) seed-cone attached to a leafy twig, x l/2 [reconstruction of Anderson and Anderson (1989) based on Townrow (1967a)

and Retallack (198011. (+g) Rissikia apiculata Townrow; (e) pollen cone, x 2; (f) bract-scales complex, x4; (g) leafy twig, x 2 [reconstruction of Anderson and Anderson (1989) based on Tow-mow (1967b)]. (h,i) Telemachus elongatus; (h) reconstruction of a seed-cone, x 1; (i) bract-scales complexes, x 1.5 (from Anderson and Anderson, 1989). (j) Heidiphylhun elongatum (Morris) Retallack. A leaf, x l/2 (from Anderson and Anderson, 1989). (k) Buriadia heterophylla (Fe&mantel) Seward and Sahni. A single inverted ovule attached to a leafy twig, enlarged (from Pant and Nautiyal, 1967).

298 S. ArchangelskyjReview of Palaeobotany and Palynology 90 (1996) 287-302

India (Pant and Bhatnagar, 1975) while Florin ( 1940b) described WaZkomiella from the Permian of Australia.

Little is known about the conifers during the Permian-Triassic transition. From Lower Triassic strata of Madagascar, South Africa and Australia, Townrow (1967b) described a plant referred to the Podocarpaceae, Rissikia (Fig. 6e-g). Its leaves are elongat+lanceolate, helically disposed. Male cones contain several microsporophylls with two abaxi- ally oriented pollen sacs that contain bisaccate striate pollen grains. Female cones have a variable number of bract-scale complexes. Each scale bears one or two inverted ovules (Fig. 6f).

Also from the Triassic of South Africa, New Zealand, Antarctica and South America, an association of long linear leaves (Heidiphyfhun; Fig. 6j) and seed cones (Telemachus) has been referred to the conifers (Retallack, 1981; Anderson and Anderson, 1989; Morel, 1991; Yao et al., 1993). Similar leaves are found in most areas of Gondwana and have received different names, namely Podozamites, Desmiophyllum, etc. Telemachus has helically arranged cone scales on a central axis. Bract and ovuliferous scales are partially fused. Scales are lobed and bear 2 or 3 reflexed ovules (Fig. 6h,i). It has been provision- ally placed in the Voltziaceae, a rather broad family that includes late Paleozoic and early Mesozoic taxa.

When we put together data on conifers, much information seems to be gained about the history of this group along the Permian-Triassic transition. Many characters can now be used to build a database adding paleogeographic distribu- tions and paleoclimatological settings. It is evident that during this time conifers were not as abundant as they were in the Jurassic. However, some families that are living in areas of the now dismembered Gondwana were already in existence, such as the podocarps. It is quite possible that some Permian conifers may have been the ancestors to Mesozoic or extant families, such as the Araucariaceae.

3. Paleofloristic relationships and plant dispersal

The probable relationships of Gondwanic plants with those found in other regions has been a

matter of discussion. In the past, when paleobotanists described Gondwanic materials, they had little hesitation to assign “northern” (mostly European) generic names, e.g. Lepidodendron, Calamites, Pecopteris, etc. However, with time, several of these names changed and new, endemic genera appeared. In some cases, paleogeographic separation was an argument to discard the use of extra-Gondwanic names.

Modem paleogeography accepts the existence of a huge Pangea during the late Paleozoic that was partly separated by the ocean Tethys into a northern or paleoequatorial continent and a south- em land, Gondwana. Several plants, determined at a specific level, are identical in areas located now in different hemispheres (e.g. India and Argentina). Some particular sectors of the Gondwana floristic assemblages have “exotic” components. These cases are mainly known in Central Africa and southern South America (Archangelsky, 1990) where “northern” (or“paleoequatorial”) taxa integrate assemblages in which typical Gondwana plants are also present. In other Gondwanic areas “alien” forms have been described, but in a small proportion and of a different nature suggesting affinities with other “northern” lands (Srivastava, 1992). The term “mixed” floras was coined for this type of assemblages.

The main Paleozoic “extra-Gondwanic” components are Sphenophyllum (fertile), Asterotheca, Alloiopteris (fertile), some species of Pecopteris, Sphenopteris (some fertile), Diplothmema, Eusphenopteris, and Annularia. Migration of these plants into Gondwana suggests that isosporous pteridophytes were fitted for long distance dispersal. This hypothesis involves a dynamic parame- ter, migration, that played a role in the dispersal and conquest of ecological niches modelling Neopaleozoic plant communities. In this regard, glaciation and continent shifting were factors that influenced plant distribution.

During the late Paleozoic, paleofloristic assemblages were poor near the pole position. At lower latitudes, vegetation diversified and in ecotonal areas a slow influx of subtropical taxa mixed with Gondwanic elements. Presently, the Gondwana territory is subdivided into two large regions,

S. ArchangelskylReview of Palaeobotany and Palynology 90 (19%) 287-302 299

Western Gondwana, where mixed floras occur, and Eastern Gondwana, where paleoequatorial taxa are rare or absent altogether. This simplistic proposal is merely a first step in the still long way to go toward understanding plant distribution during the late Paleozoic.

Triassic climate was milder and no glaciations are recorded, at least with the intensity demonstrated for the previous periods. Most Gondwanic areas have a record of taxa known in the Northern Hemisphere and it is not surprising to find Lepidopteris, Scytophyllum, Pleuromeia, Asterotheca, Osmundacaulis, etc. distributed over widely separated regions, namely Europe, Siberia and South America.

4. Conclusions

A large variety of seed plants inhabited Gondwana during the late Paleozoic and early Mesozoic. The huge supercontinent stretched from the southern pole to near the equator and the vegetation was distributed following a translatitu- dinal pattern. A direct connection with the paleoequatorial Euramerican continent allowed some plants of that area to migrate and establish in Gondwana.

As should be expected for such a large area, there are compositional differences between plant assemblages in Gondwana although many components were common to the whole supercontinent. During the Carboniferous a pre-Glossopteris assemblage occurs; it includes seed ferns, primitive gymnosperms, putative cordaites and the oldest conifers. The Permian is characterized by the domi- nance of Glossopteridales, the extinction of most Carboniferous genera and in some areas by the abundance of conifers. The oldest probable Ginkgoales and Cycadales were also components of late Paleozoic plant communities. The transition to the Mesozoic is marked by a change of vegetation. Few glossopterids have been recorded as relicts while two new gymnosperm groups emerge as dominants, namely the corystosperms and the peltasperms, also called “Mesozoic pteridosperms”. Conifers, cycads and Bennettitales are rare components of plant assemblages while

Ginkgoales diversify into a variety of leaf shapes that are widely distributed over all of Gondwana.

Glaciation played a role in the sometimes variable distribution of plant assemblages during the late Paleozoic. The more uniform distribution of similar or identical taxa over all of Gondwana was influenced by a milder climate during the Triassic.

The relative abundance of seed plant groups for Euramerica and Gondwana during the late Paleozoic and early Mesozoic in many aspects is similar. Knoll and Niklas (1987) presented a figure to show mean species richness and composition of subtropical to tropical, mesic floodplain compres- sion floras plotted as a function to age. Pteridosperms are dominant during most of the Carboniferous and Permian. Although they sharply decline during the Triassic, the Caytoniales (including peltasperms) are diversified and abundant during this period. In Gondwana, corystosperms were dominant extending the range of the Pteridosperms to the Triassic. Ginkgos, cycads, Bennettitales and conifers also diversified during the Triassic. Cordaites, although not conspicuous as a group, played a role during the Paleozoic- Mesozoic transition.

It is interesting to compare the conclusions on eventual relationships and taxa grouping by following different lines of thought. Here I have presented the findings and evaluated the Permian- Triassic Gondwana plants viewed from the tradi- tional angle of stratigraphic relationships. I have taken into account characters seen in fossils preserved in different ways combined with the factors time and space, i.e. chronology and paleogeography.

A different approach to this problem is the use of cladistic analysis to determine relationships among fossil plants. These analyses show that a strong radiation of seed plants occurred during the same time (Crane, 1988). Emphasis is placed on the “pteridosperms” a group with diverse relationships. Several plants from Gondwana may be part of this group and research in that direction will certainly bring a more coherent picture on a global scale. What is known as Cycadopsida closely resembles the grouping of Crane (1988) that includes Medullosa, Cycadales, Callistophyton, Peltaspermum, corystosperms, Caytonia and

300 S. ArchangelskyjReview of Palaeobotany and Palynoiogy 90 (1996) 287-302

glossopterids. Only the Bennettitales and Lyginopteridaceae have been separated from the Cycadopsida. This makes sense for many paleobotanists who never liked the grouping of Cycadales and Bennettitales into the informal unit “Cycadophyta”. Coniferales, Cordaitales and Ginkgo are also grouped into what used to be called the Coniferopsida.

Most orders that are components of these two groups occur during the Permian and Early Triassic of Gondwana and Eurasia. Medullosu and Callistophyton are the exceptions while Glossopteridales need a confirmation of their occurrence in Eurasia.

As a conclusion it can be assumed that the Paleozoic-Mesozoic transition witnessed substan- tial vegetational changes over the Gondwana Supercontinent. Different causes, i.e. climatic, paleogeographic, geologic and biologic, were responsible for a new scenario in which plants developed. The study of late Paleozoic-early Mesozoic floras of Gondwana confirms that changes at a global scale occurred modelling a new type of vegetation that persisted over 100 million years until the Cretaceous.

References

Anderson, J.M. and Anderson, H.M., 1983. Palaeoflora of South Africa, Molteno Formation (Triassic). I. Balkema, Rotterdam, 227 pp.

Anderson, J.M. and Anderson, H.M., 1985. Palaeotlora of Southern Africa. Prodromus of South African megatloras: Devonian to Lower Cretaceous. Balkema, Rotterdam, 423 pp.

Anderson, J.M. and Anderson, H.M., 1989. Palaeotlora of Southern Africa, Molteno Formation (Triassic). II. Gymnospenns (excluding Dicroidium). Balkema, Rotterdam, 576 pp.

Archangel&y, S., 1968. Studies on Triassic fossil plants from Argentina. IV. The leaf genus Dicroidium and its possible relation to Rhexoxylon stems. Palaeontology, 11: 500-512.

Archangel&y, S., 1970. Fundamentos de Paleobotanica. Publ. Mus. La Plata Ser. T&m. Did&t., 10: l-347.

Archangel&y, S., 1981. Fedekurtzia, a new Carboniferous frond from Gondwanaland and its fructitlcation. Am. J. Bot., 68(8): 1130-1138.

Archangelsky, S., 1983. Nothorhacopteris a new generic name for some monopinnate fronds of Gondwanaland (=

Rhacopteris ovata auct. and PseuaWucopteris Rigby 1973). Rev. Palaeobot. Palynol., 38(3/4): 151-172.

Archangelsky, S., 1990. Plant distribution in Gondwana during the Late Paleozoic. In: T.N. Taylor and E.L. Taylor (Editors), Antarctic Paleobiology. Its Role in the Reconstruction of Gondwana. Springer, New York, NY, pp. 102-l 17.

Archangelsky, S. and Brett, D.W., 1961. Studies on Triassic fossil plants from Argentina. I. Rhexoxylon from the Ischigualasto Formation. Philos. Trans. R. Sot. London B, 244: 1-19.

Archangelsky, S. and Brett, D.W., 1963. Studies on Triassic Fossil Plants from Argentina. II. Michelilloa waltonii nov. gen. et sp. from the Ischigualasto Formation. Ann. Bot., 27( 105): 147-154.

Archangel&y, S. and Cuneo, R., 1987. Ferugliocladaceae, a new conifer family from the Permian of Gondwana. Rev. Palaeobot. Palynol., 51: 3-30.

Archangel&y, S. and Cimeo, R., 1990. Polyspermophyllum, a new Permian gymnosperm from Argentina, with considera- tions about the Dicranophyllales. Rev. Palaeobot. Palynol., 63: 117-135.

Arrondo, O.G., Morel, E. and Gamma, D., 1987. Hallazgo de cones de coniferas en conezion organica con ramas en el Carbonifero superior tardio de la cuenca de Paganzo, Argentina. Actas IV Cong. Latinoam. Paleontol., 1, pp. 251-254.

Artabe, A., Archangel&y, S. and Arrondo, O.G., 1987. Sobre una fructilicacmn masculina asociada a frondes de Botrychiopsis de1 Carbonifero de Cienaga de1 Vallecito, provincia de San Juan, Argentina. Actas VII Simp. Argent. Paleobot. Palinol., pp. 21-24.

Bajpai, U., 1991. On Ginkgoites leaves from the Early Permian of Rajmahal Hills, Bihar, India. Ameghiniana 28(1/2): 145-148.

Bose, M.N. and Srivastava, SC., 1973. Some micro- and megastrobili from the Lower Triassic of Gopad River Valley, Nidpur. Geophytology, 3: 69-80.

Bose, M.N., Taylor, E.L. and Taylor, T.N., 1990. Gondwana floras of India and Antarctica- a survey and apprisal. In: T.N. Taylor and E.L. Taylor (Editors), Antarctic Paleobiology. Its Role in the Reconstruction of Gondwana. Springer, New York, NY, pp. 118-148.

Cesari, S.N., Arrondo, O.G. and van Amerom, H.W.J., 1988. Eusphenopteris Novikz a new component of the Gondwana floras. Meded. Rijks Geol. Dienst, 42: l-19.

Chandra, S. and Surange, K.R., 1979. Revision of the Indian species of Glossopteris. Birbal Sahni Inst. Palaeobot. Monogr., 2: 1-291.

Crane, P.R., 1988. Major clades and relationships in the “higher” Gymnosperms. In: C.B. Beck (Editor), Origin and Evolution of Gymnosperms. Columbia Univ. Press, New York, NY, pp. 218-297.

CXneo, R., 1985. Ejemplares f&tiles de Genoites patagonica Feruglio (Buriadiaceae, Coniferopsida ?) de1 Ptrmico de Chubut, Republica Argentina. Ameghiniana, 22(3/4): 269-279.


Cimeo, R., 1987. Sobre la presencia de probables Ginkgoales en el P&mico inferior de Chubut, Argentina. Actas VII Simp. Argent. Paleobot. Palinol., pp. 47-50.

Dobruskina, LA., 1969. The genus Scytophyllm (morphology, epidermal structure and systematic position). In: Pteridosperms of the late Paleozoic and Mesozoic. Trans. Acad. Sci. USSR, 190: 35- 58 (in Russian).

Erwin, D.M., Pfefferkom, H.W. and Aheman, V., 1994. Early seed plants in the Southern Hemisphere: I. Associated ovulate and microsporangiate organs from the Carboniferous of Peru. Rev. Palaeobot. Palynol., 80: 19-38.

Fauque, L., Limarino, C., Cesari, S. and Sabattini, N., 1989. El Carbonifero inferior fosillfero de1 area de1 Rio La Troya, sudoeste de la provincia de La Rioja. Ameghiniana, 26: 55-62.

Florin, R., 194Oa. Die Koniferen des Oberkarbons turd des Unteren Perms, 5. Palaeontographica B, 85: 243-363.

Florin, R., 194Ob. On Wakomia n. gen., a genus for upper Palaeozoic conifers from Gondwanaland. K. Sven. Vetenskapsakad. Handl., lS(5): l-23.

Gould, R.E. and Delevoryas, T., 1977. The biology of Glossopterb: Evidence from petrified seed-bearing and pollen- bearing organs. Alcheringa, 1: 387-399.

Kapoor, H.M., Bajpai, I-J. and Maheshwari, H.K., 1992. kidmiropterir meyenii Kapoor: a possible cycadalean leaf from the Early Permian Mamal Formation in the Kashmir Himalaya. Palaeobotanist, 39(2): 141-148.

Knoll, A.H. and Niklas, K.J., 1987. Adaptation, plant evolution, and the fossil record. Rev. Palaeobot. Palynol., 50( l/2): 127-149.

Laveine, J.P., 1993. Frond architecture, phyllotazy and general habit of some representatives of the genus Eusphenopteris Simson-Scharold, Carboniferous Pteridosperm. C.R. XII Cong. Int. Stratigr. G&01. Carbonifere/Permien, Buenos Aires 1991, 2, pp. 73-88.

Lear-y, R.L., 1993. Comparison of the early Pennsylvanian Euramerican fossil plant Lesleya with the Permian Glossopreris of South America. C.R. XII Cong. Int. Stratigr. G&l. Carbonifere/permien, Buenos Aires 1991, 2, pp. 107-116.

Leguizamon, R. and Vega, J.C., 1991 (1990). El genera l’kiphyllopteris (morfogertero de fro&s) en el Carbonifero de la Republica Argentina. Ameghiniana, 27(3/4): 305-309.

Maheshwari, H.K. and Srivastava, A.K., 1992. The glossopterid group of plants in an evolutionary perspective. Palaeobotanist, 41: 110-113.

Meyen, S.V., 1984. Basic features of gymnosperm systematics and phylogeny as evidenced by the fossil record. Bot. Rev., 50: l-11.

Meyer-Berthaud, B., Taylor, T.N. and Taylor, E.L., 1993. Petrifled stems bearing Dicrotdiwn leaves from the Triassic of Antarctica. Palaeontology, 36(2): 337-356.

Morel, E.M., 1991. Estudio paleofloristico y paleoambiental de la secuencia tri&sica en el area de Cacheuta (Provincia de Mendoza). Thesis. Fat. Cienc. Nat. Mus., La Plats, 368 pp. (unpubl.).

Pant, D.D., 1982. The Lower Gondwana gymnosperms and their relationships. Rev. Palaeobot. Palynol., 37( l/2): 55-70.

Pant, D.D. and Bhatnagar, S., 1975. A new kind of foliage shoot Searsolia oppositifolia gen. et sp. nov. from Lower Gondwanas of Raniganj Coalfield, India. Palaeontographica B, 152: 191-199.

Pant, D.D. and Nautiyal, D.D., 1960. Some seeds and sporangia of Glossoperis flora from Raniganj coalfield, India. Palaeontographica B, 121: 102-121.

Pant, D.D. and Nautiyal, D.D., 1967. On the structure of Buriadia heterophylla (Feistmantel) Seward et Sahni and its fructification. Trans. Philos. Sot. London, 252(B774): 27-48.

Pant, D.D. and Sir& K.B., 1974. On the stem and attachment of Glossopteris and Gangamopteris leaves. Part II. Structural features. Palaeontographica B, 147: 42-73.

Pant, D.D. and Verma, B.K., 1964. The cuticular structure of Noeggerathiopsis Feistmantel and Cordaites Unger. Palaeontographica B, 115: 21-44.

Petriella, B.T., 1978. La rewnstrucci6n de Dicroidium (Pteridospermopsida, Corystospermaceae). Obra Cent. Mus. La Plata, 5: 107-l 10.

Petriella, B.T., 1981. Sistem&ica y vinculaciones de las Corystospermaceae H. Thomas. Ameghiniana, 18: 221-234.

Pigg, K.B., 1990. Anatomically preserved Gfossopteris foliage from the central Transantarctic Mountains. Rev. Palaeobot. Palynol., 66: 105-127.

Pigg, K.B. and Taylor, T.N., 1990. Permineralized Glossopteris and Dicroidium from Antarctica. In: T.N. Taylor and E.L. Taylor (Editors), Antarctic Paleobiology. Its Role in the Reconstruction of Gondwana. Springer, New York, NY, pp. 164-172.

Pigg, K.B. and Taylor, T.N., 1993. Anatomically preserved Glossopteris stems with attached leaves from the central Transantarctic mountains, Antarctica. Am. J. Bot., 80(5): 500-516.

Poor?, R.J. and Kerp, J.H.F., 1990. Aspects of Permian palaeobotany and palynology. XI. On the recognition of true peltasperms in the Upper Permian of Western and Central Europe, and a reclassification of species formerly included in Peltaspetmum Harris. Rev. Palaeobot. Palynol., 63(3/4): 197-226.

Retallack, G., 1977. Reconstructing Triassic vegetation of eastern Australasia: a new approach for the biostratigraphy of Gondwanaland. Alcheringa, 1: 247-277.

Retallack, G., 1980. Late Carboniferous to Middle Triassic megafossil floras from the Sydney Basin. In: A guide to the Sydney Basin. Bull. Geol. SW. NSW, 26: 385-430.

Retallack, G.J., 1981. Middle Triassic megafossil plants from Long Gully, near Otematata, north Otago, New Zealand. J.R. Sot. NZ, 11(3): 167-200.

Rigby, J.F., 1984. Some aspects concerning Permian cordaitalean plants from Gondwanaland. Mem. III Cong. Latinoam. Paleontol., pp. 140-142.

Rigby, J.F., 1989. Bergiopteris and Botrychiopsis from the Late Palaeozoic of Gondwanaland. C.R. XI Cong. Int. Stratigr. Geol. Carbon&e, Beijing 1987, 3, pp. 143-148.

Scotese, C.R. and McKerrow, W.S., 1990. Revised world maps

302 S. Archangels&y/Review of Palaeobotany and Palynology 90 (1996) 287-302

and introduction. In: W.S. McKerrow and C.R. Scotese (Editors), Palaeozoic Palaeogeography and Biogeography. Geol. Sot. London Mem., 12: l-21.

Sessarego, H.L. and C&sari, S.N., 1989. An Early Carboniferous flora from Argentina. Biostratigraphic implications. Rev. Palaeobot. Palynol., 57: 247-264.

Smoot, E.L., Taylor, T.N. and Delevoryas, T., 1985. Structurally preserved plants from Antarctica: I. Antarcticycas gen. n., a Triassic cycad stem from the Beardmore Glaciar area. Am. J. Bot., 72: 1410-1423.

Srivastava, A.K., 1992. Alien elements in the Gondwana Flora of India. Palaeobotanist, 40: 147-156.

Surange, K.R. and Maheshwari, H.K., 1970. Some male and female fiuctitications of Glossopteridales from India. Palaeontographica B, 129: 178-192.

Taylor, E., 1987. Gfossopteris reproductive organs: an analysis of structure and morphology. Abstr. XIV Int. Bot. Cong., p, 286.

Taylor, E.L., 1996. Enigmatic gymnosperms? Structurally preserved Permian and Triassic seed ferns from Antarctic. Rev. Palaeobot. Palynol., 90: 303-318, this issue.

Taylor, E.L. and Taylor, T.N., 1992. Reproductive biology of the Permian Glossopteridales and their suggested relationship to flowering plants. Proc. Natl. Acad. Sci. USA, 89: 11,495-11,497.

Taylor, T.N. and Taylor, E.L., 1993. The Biology and Evolution of Fossil Plants. Prentice.-Hall, Englewood Cliffs, NJ, 982 pp.

Taylor, T.N., Del Fueyo, G.M. and Taylor, E.L., 1994. Permineralized seed fern cupules from the Triassic of Antarctica: implications for cupule and carpel evolution. Am. J. Bot., 81(6): 666-677.

Townrow, J.A., 1960. The Peltaspermaccae, a pteridosperm family of Permian and Triassic age. Palaeontology, 3(3): 333-361.

Townrow, J.A., 1967a. On Voltziopsis a southern conifer of Lower Triassic age. Proc. R. Sot. Tasmania, 101: 173-188.

Townrow, J.A., 1967b. On Rissikia and Mataia podocarpaeous conifers from the Lower Mesozoic of southern lands. Proc. R. Sot. Tasmania, 101: 173-188.

Vega, J.C. and Archangel&y, S., 1996. Austrocalyx jejenemis Vega and Archangel&y, gen et sp. nov., a cuplate rhacopter- oid pteridosperm from the Carboniferous of Argentina. Rev. Palaeobot. Palynol., 91: in press.

Yao, X., T.N. Taylor and Taylor, E.L., 1993. The Triassic seed cone Telemachus from Antarctica. Rev. Palaeobot. Palynol., 78: 269-276.

Zamuner, A.B. and Artabe, A.E., 1990. El genera Scytophylhun Bomemann 1856 (Familia Peltaspermaceae Thomas), un nuevo representante de la flora tri&sica de Argentina. Rev. Mus. La Plats 9, Paleontol., 54: 131-141.

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Aspects of Gondwana paleobotany: gymnosperms of the Paleozoic—Mesozoic transition

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