Fig 5 - uploaded by Rodrigo Neregato
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Vascularization and apexes of the bracts in Cheirostrobus pettycurensis. A, Tangential section probably close to the axis showing the main vascular bundles before division (arrows). Specimen SC 521. B, Proposed radial section reconstruction showing the sporangiophores, bracts, and approximate position of section X-X 0 . C, Proposed three-dimensional reconstruction of the vascular system showing the main vascular bundle and its daughter vascular bundles. Scale bars p 2 mm.
Contexts in source publication
Context 1
... it has not been possible to determine the precise course of the derived bundles passing through the mid to distal parts of the fertile appendages. The best information comes from tangential 814 sections through the cone that show small lacunae surrounding vascular bundles organized adjacent to each other, producing three derived bundles ( fig. 5A-5B). In generating this organization, both the bract bundle (b) and sporangiophore bundle (g) divide horizontally in a palmate fashion, as noted by Scott (1897b). The b bundle divides to produce two or three daughter bundles (b1, b2, b3) that each supply the bract and the heel of the bract (see below), while g bundles also divide to ...
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... b bundle divides to produce two or three daughter bundles (b1, b2, b3) that each supply the bract and the heel of the bract (see below), while g bundles also divide to produce two or three daughter bundles (g1, g2, g3) that each supply a single sporangiophore. The palmate divisions are demonstrated by the bundles dividing in tangential section ( fig. 5A), where bundles g1, g2, and g3 occur in groups of two or three after the first division, whereas the b bundles occur in groups of two or three after the second division ( fig. 5C, ...
Context 3
... or three daughter bundles (g1, g2, g3) that each supply a single sporangiophore. The palmate divisions are demonstrated by the bundles dividing in tangential section ( fig. 5A), where bundles g1, g2, and g3 occur in groups of two or three after the first division, whereas the b bundles occur in groups of two or three after the second division ( fig. 5C, ...
Context 4
... pedicels, and the bracts that appear in Scott's diagram. The radial organization of the cone is therefore much more similar to that presented here as figure 7 than to Scott's original reconstruction. The organization in transverse section is, however, remarkably accurate, although the divisions of the vascular bundles vary to show two zones ( fig. 5C, 5D). Moreover, the number of sporangia per sporangiophore shown in figure 7 accommodates our new interpretation. New specimens combined with nondestructive tomographic techniques (e.g., Spencer et al. 2013) will be required to fully reconstruct the strobilus in full ...
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... Retusotriletes has been assigned to the primitive plants, such as the psilophytes, rhyniophytes and zosterophylls (Azcuy, 1978;Traverse, 2007), representing an important genera during the Devonian (Traverse, 2007). Although, it was reported in situ in Cheirostrobus, a sphenophyte cone (Neregato and Hilton, 2019). ...
The results of this contribution represent the first attempt regarding palynological and paleobotanical records from the municipality of Alfredo Wagner, Santa Catarina State, southern Brazil. The fossils were recovered in the top of the Siderópolis Member, upper portion of the Rio Bonito Formation, Paraná Basin. The palynological assemblage revealed a well-preserved assemblage composed of 28 spores and 24 pollen, mainly dominated by ferns and gymnosperms, correlated with the Vittatina costabilis Zone. Eight taxa are first records for this unit (Granulatisporites varigranifer, Punctatisporites subvaricosus, Gondisporites serrulatus, Didecitriletes sp, Vitreisporites signatus, Alisporites ovatus, Pteruchipollenites indarraensis and Cycadopites cymbatus), and three of them for the basin (P. subvaricosus, Didecitriletes sp. and C. cymbatus). The paleobotanical assemblage is mainly represented by Glossopteris (seven species), ferns (Pecopteris and Sphenopteris) and seeds (Cornucarpus, Cordaicarpus and Samaropsis), corresponding to the Gondwanan “Glossopteris Flora”. Although Cheirophyllum and Cornucarpus would be typical and restricted to the underlying Phyllotheca-Gangamopteris Flora, their presence allows us to correlate the floristic deposits with the basal part of the Glossopteris-Brasilodendron Flora range. In addition, U–Pb zircon CA-TIMS datings obtained in nearby correlated sections allows the macro- and microfloras to be constrained to the latest Asselian age.
... These rocks outcrop in cliff sections at Pettycur and at Kingswood End to the west, as well as in the intervening Pettycur Caravan site (Rex and Scott 1987). The nearby Pettycur limestone flora has been described in numerous publications (Scott et al. 1984;Rex and Scott 1987;Neregato and Hilton 2019). Palynological dating of the Kinghorn Volcanic Formation has indicated that it belongs to the Raistrickia nigra-Triquitrites marginatus (NM) and Tripartites vetustus-Rotaspora fracta (VF) miospore zones (Brindley and Spinner 1989) of mid to late Asbian to early Brigantian regional substages of the Viséan stage (Monaghan and Pringle 2004), with absolute ages between 329 and 335 Ma (Monaghan and Pringle 2004;Monaghan and Browne 2010). ...
Premise of research. Mississippian (Lower Carboniferous) anatomically preserved ovules are pivotal to our present understanding of the Paleozoic primary seed plant radiation, but few are known from the late Viséan stratigraphic interval approximately 330 million years ago. Here, we document an exceptionally well-preserved mesoscopic charcoalified ovule from late Viséan limestones that is adapted for wind dispersal and for deterring
herbivory.
Methodology. We use synchrotron radiation X-ray tomographic microscopy (SRXTM) and low-vacuum scanning electron microscopy (LVSEM) to analyze histological features not identifiable through traditional methods.
Pivotal results. The ovule is small, 2 mm long and 1.25 mm in maximum diameter, and has a dense covering of spirally arranged, long, slender, hollow hairs with glandular apexes and a distal papilla. The nucellus is fused to the integument up to the nucellar apex, and above this, the integument comprises eight apical lobes, each with a single vascular bundle. The nucellar apex has a domed pollen chamber and large central column characteristic of hydrasperman-type (lagenostomalean) pteridosperms, but it lacks the distal salpinx seen in most hydrasperman ovules, leaving an exposed distal opening to the pollen chamber for pollination. Differences with existing taxa lead to the erection of Hirsutisperma rothwellii gen. et sp. nov.
Conclusions. The apical glands presumably functioned as granivory deterrents; coprolites (fossilized feces) from herbivorous arthropods are abundant in the fossiliferous horizon and at this stratigraphic interval. The small ovule size and its dense covering of hairs indicate Hirsutisperma was adapted for wind dispersal and was an r-selected species, producing large numbers of small offspring in unstable or changing environments. Taphonomic implications are discussed, including preservational biases for charcoalification. Hirsutisperma provides the first clear evidence for ecological niche partitioning in Mississippian hydrasperman-type ovules.
The Lower Devonian Klerf Formation is an exceptional Konservat-Lagerstätte, exposed at multiple sites in the Waxweiler region in the Eifel area, western Germany. It has been studied for its various fossils, mainly arthropods, fishes, plants, molluscs, brachiopods, and crinoids. At Waxweiler, the sediments are palaeoecologically interpreted as a prograding deltaic depositional system elongated from NW to SE in the Ardenno-Rhenish area. The Klerf Formation has, however, not been studied in full detail in terms of its microflora and microfauna. Our study of the sediments of the formation from two different quarries in the Waxweiler area yielded fairly diverse miospore assemblages dominated by abundant organic matter of varying degrees of coalification. The miospore assemblages are mainly composed of classical Lower Devonian taxa of the Old Red Continent (Laurussia). These belong, among others, to the genera Ambitisporites, Apiculiretusispora, and Retusotriletes. Biostratigraphically more important species recovered include Acinosporites lindlarensis, Apiculiretusispora brandtii, Cymbosporites asymetricus, Diatomozonotriletes franklinii, Emphanisporites annulatus, Verruciretusispora dubia and Verrucosisporites polygonalis. In addition, Emphanisporites foveolatus, which is known only from a limited area in the Ardenno-Rhenish region, is also identified, indicating an earliest Pragian to middle Emsian age for the composite section. These assemblages are found to be accompanied by reworked phytoplankton to a much lesser extent. Our results reveal a much larger palaeobotanical diversity from the Rhineland outcrops than previously known, indicating a well-developed Psilophyton-type vegetation with related plants. The results further suggest a likely presence of plants such as Leclercqia and Pertica.
The Rhynie chert (Aberdeenshire, Scotland, UK) plant Horneophyton lignieri is likely one of the most studied elements of Lower Devonian floras considering both macro and microremains. Intriguingly, while larger plant fragments are exceptionally fossilized, in situ spores are not necessarily well-preserved in the chert: they are dark brown and intensively torn overall. However, spore masses are often dominated by single spores, which can be taxonomically attributed. Mainly, Horneophyton spores have been described as belonging to Apiculiretusispora type and Emphanisporites cf. decoratus, this last one being currently accepted in general. Here, we document new Horneophyton spore morphologies, that are sometimes quite different. Such morphologies include, but are not restricted to, Ambitisporites, Dibolisporites or Retusotriletes. All these observed spore morphotypes belong to the same palaeobiological entity, as they have been found in the same parent plant. These findings show that the sporangia of a same plant species may deliver diverse taxa of coeval isolated spores. But most importantly, if these spores are found in sediments, they would most probably be identified as different dispersed miospore taxa. This highlights that caution is needed when comparing plant diversity with the dispersed spore fossil record. Moreover, we confirm the presence of Emphanisporites decoratus inside most of the sporangia of Horneophyton lignieri, and its high morphological variability. We further discuss the role of the different states of maturation and preservation, as well as taphonomy-induced features, on observed spore diversity.
