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Dicroidium crassinervis forma stelzerianwm. a-c. NMVF'198403. a. Leaf morphology, x 3. b. Internal leaf surface illustrating details of stomata. c. External surface of leaf showing stomatal aperture. Scale bars: b, c = 10 pm. range illustrated by Anderson &Anderson (1983) from square rhomboidal to falcate. Material examined: Over 100 slabs were collected in the field and examined in the laboratory. A representative range of morphological variation were assigned numbers NMVP198396-198402, all from locality PCM 19. Isolated leaves and cuticles were also examined from localities PCM 18, 32 (Fig. 2).
Source publication
Megafloral remains recovered from the Jetty Member and the upper part of the Flagstone Bench Formation, Amery Group include Dicroidium and Pagiophyllum. Dicroidium
zuberi and D.
crassinervis forma stelznerianum occur with Pteruchus
dubius and support a Mid to Late Triassic age. A new species of conifer, Pagiophyllum
papillatus, is recognized along...
Contexts in source publication
Context 1
... Fragments of pinnate fronds up to 30 mm long and 12 mm wide. Pinnules up to 8 mm long and up to 3 mm wide, rounded triangular to triangular, veins barely developed, one or two dichotomosing once or rarely twice, midrib absent (Fig. 4a). Pinnules amphistomatic, equal densities on upper and lower surfaces. Epidermal cells 45-12Op long and 2 U 8 p wide, slightly longer and more elongate over rachis, anticlinal walls straight, epidermal cells without ...
Context 2
... apparatus predominantly oriented longitudinally with respect to the pinnule axis comprising four rarely five subsidiary cells (Fig. 4b, c) (Fig. 5a, c). Epidermal cells elongated longitudinally, 80-140 pm long and 20-34 p wide, walls straight. Epidermal cells between pollen sacs with well developed trichomes at least 67 p long (Fig. 5g). Microsporangia numbering more than 100 per sporophyll, up to 2 mm long, and 500pm wide, oblanceolate in outline, dehiscence via a ...
Citations
... Cuticles from type A show some similarities to Pagiophyllum-like foliage, such as stomata distribution in more or less regular longitudinal rows. Pagiophyllum is a conifer foliage morphogenera for conifer vegetative organs covered by leaves that are at least twice as long as wide, known from Late Triassic to Upper Cretaceous (i.e., Kendall, 1948;Harris, 1979;Cantrill et al., 1995). Elongated leaves with stomata in rows on the adaxial and abaxial sides are documented, i.e., from Pagiophyllum kurri from Jurassic of Yorkshire (Harris, 1979). ...
Upper Triassic fossil plants are well documented from the Keuper of Europe. Carnian and Rhaetian floras are rich in a variety of plant taxa, whereas in comparison, the Norian is limited to a few localities with poorly preserved fossil plant communities showing low diversification. The Norian Grabowa Formation in Zawiercie-Marciszów, Upper Silesia, southern Poland, contains fossils of arborescent gymnosperms, including petrified conifer trunks. In this study, we present a fossil plant assemblage, containing fragmented plant parts in multiple forms of preservation, i.e., permineralised trunks and rooting structures, stems compressions, dispersed cuticles, and megaspores. Analysis of the macromorphological characters proved the presence of gymnosperms, including the arborescent conifer Agathoxylon cf . keuperianum , known already from this locality from fragments of charcoalified wood. Sphenophytes are represented by disarticulated stems of Equisetites sp ., and Neocalamites sp . The variation in plant fossils indicates the possibility of higher plant diversity. Analysis of cuticles, macerated from different plant-bearing lithologies, revealed a variety of conifer foliage, expressed as five cuticulae dispersae morphotypes (needle-leaf Elatocladus -type and scale-leaf Pagio - Brachyphyllum -like). Plant fossils at Zawiercie-Marciszów are preserved in calcareous mudstones and micritic limestone concretions, developed in a fluvial environment. The presence of sphenophyte stems ( Equisetites and Neocalamites ) indicates that local conditions were more humid and suitable for spore-producing plants, appearing in the mid-Norian tectonic-pluvial episode, recorded in the Grabowa Fm.
... The Leigh Creek species differs from Dicroidium trilobitum and from the various other forms of D. crassinerve (to which this leaf morphology has been referred) in having an extremely thin cuticle and in being mostly hypostomatic with only a few stomata on the upper leaf surface (Townrow 1966;Anderson & Anderson 1983;Cantrill et al. 1995;Bomfleur & Kerp 2010). These cuticle details, together with the typical crenate to dentate pinnule margin, may delimit a previously undescribed species, but owing to the sparse and incomplete material, we refrain from formally establishing a new taxon for these specimens. ...
... Corystosperms, especially as Dicroidium leaves, are abundantly preserved in the Middle and Late Triassic of Gondwana, and extensive collections of Gondwanan Triassic corystosperms have greatly expanded our understanding of these plants (e.g. Townrow 1962Townrow , 1965Archangelsky 1968;Holmes & Ash 1979;Playford et al. 1982;Retallack 1983Retallack , 1995Cantrill et al. 1995;Yao et al. 1995;Axsmith et al. 2000Axsmith et al. , 2007Klavins et al. 2002;Anderson & Anderson 2003;Holmes & Anderson 2005;Bomfleur & Kerp 2010;Pattemore 2016a, b;Anderson et al. 2019aAnderson et al. , b, 2020. However, a complete understanding of the structure and homology of their reproductive structures has been hindered by their preservation as compression or impression fossils. ...
... The concept that Umkomasia, Pteruchus and Dicroidium were produced by the same plants was recognized originally by Thomas (1933) and has been amply supported subsequently by evidence from many localities on four continents (Townrow 1965;Playford et al. 1982;Retallack 1983Retallack , 1995Pole & Raine 1994;Cantrill et al. 1995;Holmes & Anderson 2005;Anderson & Anderson 2003;Pattemore 2016a). The reconstruction is also supported by the similar secretory cavities that occur in tissues of the permineralized cupules of Umkomasia resinosa, the pollen organ of Pteruchus fremouwens (Yao et al. 1995) and leaves of Dicroidium fremouwensis (Pigg 1990) from the upper Middle or Late Triassic Fremouw Peak locality in the Central Transantarctic Mountains, Antarctica. ...
The group referred to informally as the corystosperms, described initially based on compression fossils from the Triassic of Gondwana, have long been considered critical extinct plants for understanding seed plant phylogeny, the evolution of seed plant reproductive structures and the relationships of angiosperms. Here we describe a new genus and species of corystosperm seed-bearing structure, Jarudia zhoui gen. et sp. nov., based on abundant silicified material collected from the newly discovered chert in the Early Cretaceous Huolinhe Formation of eastern Inner Mongolia, north-eastern China. Jarudia zhoui is a lax seed cone consisting of a flexible central axis bearing deciduous, helically arranged, lateral seed-bearing units. Individual seed-bearing units consist of an elongate bract partially fused to an unbranched cupule stalk that bears a single, reflexed cupule apically. Each cupule is formed by the strongly reflexed cupule stalk and one median and two lateral flaps. The cupule stalk supplied by two vascular bundles and three unvascularized flaps partially enclose two three-angled seeds. Jarudia zhoui bears a striking resemblance to Doylea tetrahedrasperma from the Early Cretaceous of Canada and similar plants from the Early Cretaceous of Mongolia. There are also strong similarities with ovulate structures of Umkomasia from the Triassic of Gondwana in the structure and anatomy of individual cupules, their axial nature, and the architecture of the entire seed-bearing structure that has two orders of branching. New information from Jarudia zhoui, together with information on other corystosperm ovulate organs from the Northern Hemisphere, significantly expands our understanding of this key group of extinct plants, suggests that the cupules of the Early Cretaceous and Triassic corystosperms are homologous, and raises critical questions about the definition and phylogenetic circumscription of the corystosperms, including how Early Cretaceous and Triassic corystosperms are related to each other and to other groups of seed plants, including angiosperms.
... The occurrence of the genus Pagiophyllum may indicate different environmental conditions; it is not only considered as an index for hot and arid environments (Cantrill, Drinnan, & Webb, 1995;Thévenard & Barbacka, 2000;Vakhrameev, 1991), but also is recorded in wet conditions (Barbacka, 2011;Popa & Van Konijnenburg-van Cittert, 2006 (Pocock & Jansonius, 1961;Vakhrameyev, 1982;Walker, 1967; Y. D. Wang et al., 2010). This suggests that under hot and semi-arid or arid climate conditions, abundant rainfall in the rainy seasons plays a significant role in the development of regional lakes or rivers, as well as the aforementioned flood events. ...
Terrestrial red beds are extensively developed in the Upper Jurassic of the Sichuan Basin, southern China, where few fossils have been documented. Recently, abundant silicified wood specimens were found in the central Sichuan Basin, but no plant foliage fossils have been recorded from the same strata. Here, we report the first leafy shoot fossils collected from the red beds of the Upper Jurassic Penglaizhen Formation in Shehong City, central Sichuan Basin. Based on careful comparisons with potential Mesozoic conifer fossils, they were assigned to Pagiophyllum, an extinct conifer taxon of the family Cheirolepidicaceae. The generic classification agreed with the palaeovegetation features of the Penglaizhen Formation which were represented by gymnosperms of Araucariaceae (Agathoxylon-type wood) and Cheirolepidiaceae (Brachyoxylon-type wood). The non-coexistence between the leafy shoot fossil and the petrified wood depicted a unique process of fossil preservation, which may be related to the palaeo-flood events in this area. The palaeoclimate background during the Late Jurassic of Shehong was suggested to be a hot and semi-arid or arid condition, supported by the Classopollis-dominated (75–90%) pollen assemblage from the Penglaizhen Formation. The fossil foliage was collected from lacustrine or fluvial sediments. This suggests that the rainy season is a key factor in the development of regional lakes or rivers and flood events, which offered a suitable local environment for plant growth and helped construct a more complex ecological system, allowing a variety of creatures to survive in the central Sichuan Basin area.
... The cuticles referred to Dicroidium zuberi illustrated by Anderson and Anderson (1983, p. 215) closely resemble those reported herein on the basis of stomatal complex, shape of the guard cells, and the buttressed cell walls. Cantrill et al. (1995) also referred isolated distal pinnules with amphistomatic cuticle from Antarctica to D. zuberi (Szajnocha) Archangelsky. Pattemore (2016) interpreted that these specimens may be ascribed to D. odontopteroides, although some pinnules illustrated by Cantrill et al. (1995, Figure 3(A-C)) are similar to the apical ones of the zuberi neotype. ...
... Cantrill et al. (1995) also referred isolated distal pinnules with amphistomatic cuticle from Antarctica to D. zuberi (Szajnocha) Archangelsky. Pattemore (2016) interpreted that these specimens may be ascribed to D. odontopteroides, although some pinnules illustrated by Cantrill et al. (1995, Figure 3(A-C)) are similar to the apical ones of the zuberi neotype. Moreover, the Antarctic cuticles are like these described herein, particularly by the shape of the guard cells. ...
The Carnian Ischigualasto Formation of Argentina is known worldwide by its great abundance of palaeovertebrates, including the oldest dinosaurs and a palaeoflora represented by Onslow-type palynofloras, permineralizations, and compressions of foliage. However, thin deposits composed exclusively by cuticles
are also preserved in this unit. This unusual type of preservation, where cuticles have accumulated as thousands of superimposed specimens without sediment between them, represents leaf litters of autochthonous
or parauchthonous origin. Leaf litters are preserved into periodically flooded abandoned fluvial channels, which received accumulations of leaves from the riparian vegetation that, combined with pyroclastic inputs, generated ideal diagenetic conditions for their fossilisation. The excellent preservation of the cuticles allows the description of fine epidermal and cuticular features. One of the most common species in the Ischigualasto Formation, Dicroidium (Zuberia) zuberi (Szajnocha) Archangelsky, is described using optical and scanning electronic microscopy. Cuticles are thick, amphistomatic, with stomata sunken and randomly distributed, and with papillae on epidermal and subsidiary cells. Comparisons with previous hypostomatic records of the species suggest phenotypic plasticity of this Umkomasiaceae species. Palynological assemblages
recovered from the same deposits indicate humid conditions under a seasonal climate. The vegetation flourished after a biotic turnover dated at 228.91 Ma by radiometric method.
... The contact between the Flagstone Bench Formation and underlying Bainmedart Coal Measures straddles the Permo-Triassic boundary, which is proved by the first regular occurrence of Lunatisporites pellucidus, and the first appearance of Aratrisporites and Lepidopteris species . The Flagstone Bench Formation contains a Late Triassic megaflora with Dicroidium zuberi, Dicroidium crassinervis forma stelznerianum (Webb and Fielding, 1993;Cantrill et al., 1995), and palynoflora assigned to the Late Triassic (Norian) Onslow Microflora by Foster et al. (1994). ...
Explanatory notes to the Geological map of Mac-Robertson Land, Princcess Elixabeth Land and Prydz Bay in scale 1 mln
... Dicroidium is well described from two localities in the Nymboida Coal Measures flora, Australia (Holmes & Anderson 2005a), where the associated bryophytes plus sphenophytes (Holmes 2000), ferns (Holmes 2001(Holmes , 2003 and gymnosperms (Holmes & Anderson 2005b, 2008, 2013a, Holmes et al. 2010 have also been documented. Further good collections of Dicroidium have been made and described from Antarctica (Boucher et al. 1993, Cantrill et al. 1995, Bomfleur & Kerp 2010, Escapa et al. 2011and Bomfleur et al. 2012 and to a varying extent from many other Gondwanan localities (Gnaedinger & Herbst 1998, Barboni et al. 2016, Pattemore 2016. ...
... From the McKelvey Member of the Flagstone Beach Formation (Upper Triassic) of the Prince Charles Mountains, Cantrill et al. (1995) described Dicroidium zuberi leaves with cuticles. Masses of these leaves from their locality (PCM 19) were associated with a Pteruchus sp. ...
Anderson, H.M., Barbacka, M., Bamford, M.K., Holmes, W.B.K. & Anderson, J.M., XX. 2019. Dicroidium (foliage) and affiliated wood; Part 3 of a reassessment of Gondwana Triassic plant genera and a reclassification of some previously attributed. Alcheringa XXX, X–X. ISSN 0311-5518
Dicroidium belonging to Umkomasiaceae (Corystospermaceae) in the polyphyletic pteridosperms (seed-ferns) is reassessed comprehensively worldwide and emended. All records are analysed and some attributed to the genus previously are reclassified. Dicroidium leaves are clearly affiliated with Umkomasia ‘megasporophylls’ and Pteruchus ‘microsporophylls’. The attachments of Dicroidium leaves to stems and associated wood genera are reviewed. Dicroidium is shown to be restricted to the Triassic of Gondwana, where it is by far the most prominent and diverse genus with 23 accepted species. It is well represented in collections from South America, Antarctica, India, Australia, New Zealand and southern Africa from where the Molteno Formation is the most comprehensively sampled stratigraphic unit, yielding numerous species from 75 assemblages. The problems of defining the limits of Dicroidium and its species are addressed. The records of leaf fragments from the Indian Nidpur Flora, Early Triassic, are questionably referable to Dicroidium, whereas the multiple forking leaves from the Cisuralian of India await description as a new peltasperm genus. The forked leaves from the (?)Lopingian of Jordan, previously classified as Dicroidium, are reassessed and placed in the new genus Jordaniopteris.
Heidi M. Anderson [hmsholmes@googlemail.com], Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg 20150, South Africa; Maria Barbacka [maria.barbacka@gmail.com], W. Szafer Institute of Botany, Polish Academy of Sciences, Lubicz 46, Kraków 31-512, Poland, Botanical Department, Hungarian Natural History Museumartmem H-1431, Budapest, Pf. 137, Hungary; Marion K. Bamford [marion.bamford@wits.ac.za], Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg 20150, South Africa; W. B. Keith Holmes [wbkholmes@hotmail.com], 46 Kurrajong Street, Dorrigo, NSW 2453, Australia, University of New England, Armidale, NSW 2351, Australia; John M. Anderson [jmanderson.gondwana@googlemail.com], Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg 20150, South Africa.
... Petriella (1980) interpreted P. barrealensis as a variety of P. dubius. The species name P. dubius has been used by others (e.g., Cantrill et al. 1995, Pattemore & Rigby 2005, Pattemore 2016a) and these are all reclassified herein (Table 1). ...
Anderson, H.M., Barbacka, M., Bamford, M.K., Holmes, W.B.K. & Anderson, J.M., XX. 2019. Pteruchus (microsporophyll): part 2 of a reassessment of Gondwana Triassic plant genera and a reclassification of some attributed previously. Alcheringa XXX, X–X. ISSN 0311-5518
The microsporophyll genus Pteruchus, belonging to the pteridosperms (seed ferns) in the family Umkomasiaceae (Corystospermaceae), is reassessed comprehensively worldwide and emended. All records are analysed, and some fertile structures previously attributed are reclassified. The Lower Jurassic record of Pteruchus from Germany is ascribed to a new genus as Muelkirchium septentrionalis. Pteruchus is shown to be restricted to the Triassic of Gondwana and is clearly affiliated with the megasporophyll genus Umkomasia and the vegetative leaf genus Dicroidium. It is well represented from Argentina, Antarctica, Australia and southern Africa; the Molteno Formation of southern Africa is by far the most comprehensively sampled, yielding three species and 425 specimens from 22 localities. Nomenclatural problems with the species of Pteruchus are addressed. A key to Pteruchus species is provided; geographic and stratigraphic distributions are tabulated.
Heidi M. Anderson [hmsholmes@googlemailcom], Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg 20150, South Africa; Maria Barbacka [mariabarbacka@gmailcom], W. Szafer Institute of Botany, Polish Academy of Sciences, Lubicz 46, 31-512 Kraków, Poland; Hungarian Natural History Museum, Botanical Department, H-1431 Budapest, Pf. 137, Hungary; Marion K. Bamford [marionbamford@witsacza], Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg 20150, South Africa; W.B. Keith Holmes* [wbkholmes@hotmailcom], 46 Kurrajong Street, Dorrigo, NSW 2453, Australia; John M. Anderson [jmandersongondwana@googlemailcom], Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg 20150, South Africa. *Also affiliated with: University of New England, Armidale, NSW 2351, Australia.
... The close association of Umkomasia, Pteruchus and Dicroidium has been confirmed by studies of corystosperm fossils from other parts of the Southern Hemisphere (e.g. Townrow 1965;Holmes 1982;Retallack 1983;Cantrill et al. 1995;Yao et al. 1995;Axsmith et al. 2000;Holmes & Anderson 2005;Pattemore 2016b) and these plants have been reconstructed as small to large woody shrubs and trees based on anatomy of the stems associated with Dicroidium leaves (Archangelsky 1968;Meyer-Berthaud et al. 1992, 1993Decombeix et al. 2014). Corystosperms are thought to have evolved in the palaeotropics during the Late Permian Abu Hamad et al. 2008, 2017, later becoming a very prominent element in Gondwanan terrestrial ecosystems during the Triassic (Anderson & Anderson 1983. ...
New discoveries of corystosperm seed-bearing structures from the Tevshiin Govi locality, Mongolia, which is of Early Cretaceous (Aptian–Albian) age, show that the individual seed-bearing units of Umkomasia mongolica were borne in a cone, as also documented for the very similar reproductive units of Doylea tetrahedrasperma. New material from the Tevshiin Govi locality also documents two additional species of Umkomasia–U. corniculata sp. nov. and U. trilobata sp. nov.–that most likely grew in a different environment to U. mongolica. The occurrence of three different Umkomasia species in the Early Cretaceous of Mongolia, together with other records from the Early Cretaceous of the Northern Hemisphere, indicate that previous concepts of corystosperms, based mainly on material from the Southern Hemisphere, need to be revised. The consistent reproductive architecture of the seed-bearing structures in all three corystosperm species, with a bract subtending a variously modified axis bearing ovules, is similar to the situation in Ginkgo and conifers. These underappreciated architectural commonalities among the reproductive structures of major groups of seed plants are likely significant for a deeper understanding of seed plant evolution and require further exploration. © 2019, © The Trustees of the Natural History Museum, London 2019. All rights reserved.
... In part, this may be a consequence of poor age constraints on many of the assemblages, such that any newly discovered macroflora having broad similarities to that of the Molteno Formation is automatically assigned to the Carnian. Exceptions to this are the macrofloras of the Cacheuta Formation in Argentina (Cuyo Basin: Frenguelli 1948, Morel et al. 2011, the Tiki Formation in India (Maheshwari et al. 1978, Srivastava andPal 1983;Pal 1984), and the Flagstone Bench Formation in East Antarctica (Cantrill et al. 1995;. It is possible that part of the well-studied Blackstone Formation of the Ipswich Basin, eastern Australia, also extends to the Norian based on palynostratigraphic data (de Jersey 1975;. ...
The Triassic was a time of diversification of the global floras following the mass-extinction event at the close of the Permian, with floras of low-diversity and somewhat uniform aspect in the Early Triassic developing into complex vegetation by the Late Triassic. The Earth experienced generally hothouse conditions with low equator-to-pole temperature gradients through the Late Triassic. This was also the time of peak amalgamation of the continents to form Pangea. Consequently, many plant families and genera were widely distributed in the Late Triassic. Nevertheless, two major floristic provinces are recognizable during this interval—one in the Southern Hemisphere (Gondwana) and another in the Northern Hemisphere (Laurussia); these being largely separated by the Tethys Ocean and a palaeotropical arid belt. Regional variations in topography, climate and light regime imposed further constraints on the distribution of plant groups in the Late Triassic such that two floristic sub-provinces are recognizable within Gondwana, and nine within Laurussia based on the plant macrofossil and dispersed spore-pollen records. In a broad sense, the Late Triassic saw the diversification of several plant groups that would become important components of younger Mesozoic floras (e.g., Bennettitales, Czekanowskiales, Gnetales and several modern fern and conifer families). The representation of these groups varied not only geographically, but waxed and waned through time in response to climatic pulses, such as the Carnian Pluvial Event. Significant turnovers are apparent in both macrofossil- and palyno-floras across the Triassic–Jurassic boundary, especially in the North Atlantic and Gondwanan regions. The geographic and temporal variations in the floras have necessitated the establishment of numerous regional palynozonation schemes that are tentatively correlated in this study. Major plant macrofossil assemblages of the Late Triassic world are also placed in a stratigraphic context for the first time. The Late Triassic floras also record the re-diversification of insect faunas based on a broad array of damage types preserved on leaves and wood. By the Late Triassic, all modern terrestrial arthropod functional feeding groups were established, and several very specialized feeding traits and egg-laying strategies had developed. Although age constraints on various fossil assemblages need to be improved, this study provides the first global overview of the temporal and geographic distributions of Late Triassic floras, and establishes a basis for future targeted research on Triassic phytogeography and phytostratigraphy.
