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Du, W., Wang, X.L., Komiya, T., Zhao, R. & Wang, Y., April 2016. Dendroid multicellular thallophytes preserved in a Neoproterozoic black phosphorite in southern China. Alcheringa 40, xxx–xxx. ISSN 0311-5518.A new form of dendroid multicellular thallophyte is documented in the Ediacaran Doushantuo phosphorite at Weng’an, Guizhou Province, southern China. The dendroid thallophytes have variable forms, possibly owing to heteromorphic variation. Many lateral branches extend from the upper portions of the main axes; the lateral branches bear terminal vegetative vesicles, reproductive vesicles, monosporangium-like discoidal vesicles and urn-shaped pseudoparenchymatous structures. The vegetative vesicles give rise to clavate pseudoparenchymatous structures, characterized by differentiation of the thallus medulla/cortex, which might represent an early stage of thallus development. An oogamous conceptacle arising from one carpogonial vesicle forms a highly specialized goblet-shaped conceptacle. The discovery of th...

An enigmatic thallophyte ( Litothallus ganovex gen. et sp. nov.) occurs in the form of compressions with cellular preservation and associated sheets of complete cells in non-marine Triassic deposits in the Transantarctic Mountains, Antarctica. A combination of microscopic techniques (i.e. bright field and epifluorescence microscopy, SEM) was used to document details of this organism. The thalli are flat and appear to be composed of one to several congruently superimposed cell sheets that together form a plectenchyma or pseudoparenchyma. This discovery represents the youngest record of sheets of fossil cells, which have heretofore exclusively been reported from the Proterozoic and Palaeozoic, and is one of the few examples of cell sheets that can be attributed to macroscopic remains with confidence. We interpret the thalloid organism from Antarctica as the remains of a crustose freshwater macroalga based on its occurrence in overbank deposits of a braided fluvial environment and its morphological similarity to thalli of extant freshwater representatives of the red algal order Hildenbrandiales.

Fourty-two high-rank syntaxa and seven associations of the thallophyte system of syntaxa are either described as new or validated in this paper. Among those, there are the following nine classes: Aspicilietea candidae , Caulerpetea racemosae, Desmococcetea olivacei , Entophysalidetea deustae, Gloeocapsetea sanguineae , Mesotaenietea berggrenii , Naviculetea gregariae , Porpidietea zeoroidis , Roccelletea phycopsis . Eleven orders and ten alliances as well as three associations are described or validated: the Aspicilietalia verruculosae (incl. Aspicilion mashiginensis and Teloschistion contortuplicati ) , the Caulerpetalia racemosae (incl. Caulerpion racemosae ) , the Desmococcetalia olivacei (incl. Desmococcion olivacei ) , the Dirinetalia massiliensis , the Fucetalia vesiculosi (incl. Ascophyllion nodosi ) , the Gloeocapsetalia sanguineae, the Lecideetalia confluescentis (incl. Lecideion confluescentis ) , the Mesotaenietalia berggrenii (incl. Mesotaenion berggrenii, Mesotaenietum berggrenii and Chloromonadetum nivalis ) , the Naviculetalia gregariae (incl. Oscillatorion limosae and Oscillatorietum limosae ) , the Porpidietalia zeoroidis (incl. Porpidion zeoroidis ) , and the Roccelletalia fuciformis (incl. Paralecanographion grumulosae ). Further, five orders, seven alliances and four associations, classified in known classes, were described as well. These include: the Bacidinetalia phacodis, the Agonimion octosporae and the Dendrographetalia decolorantis (all in the Arthonio radiatae-Lecidelletea elaeochromae ), the Staurothelion solventis (in the Aspicilietea lacustris ), the Pediastro duplicis-Scenedesmion quadricaudae and the Pediastro duplicis-Scenedesmetum quadricaudae (both in the Asterionelletea formosae ), the Peccanion coralloidis and the Peltuletalia euplocae (both in the Collematetea cristati ), the Laminarion hyperboreae, the Saccorhizo polyschidi-Laminarietum and the Alario esculenti-Himanthalietum elongatae (all in the Cystoseiretea crinitae ) , the Delesserietalia sanguinei, the Delesserion sanguinei and the Delesserietum sanguineae (all in the Lithophylletea soluti ), as well as the the Rinodino confragosae-Rusavskietalia elegantis and the Rhizocarpo geographici-Rusavskion elegantis (both in the Rhizocarpetea geographici ).

Based on the seemingly simple organization of extant thalloid organisms (e.g., thalloid liverworts, lichens and algae), it has historically been believed that primitive thallophyte communities had colonized the terrestrial realm long before the first appearance of vascular land plants in the Silurian.1,2 This hypothesis is continuously substantiated by an increasing number of reports of (crypto)spores, phytodebris and biogeochemical signals attributable to thalloid organisms that predate the earliest unequivocal axial land plant fossils by at least 40 million years.3–7 However, with the exception of marine calcified algae, the macrofossil record of thalloid organisms is meagre throughout Earth history. This is commonly explained by the general absence of sclerified stabilizing and conducting tissues in thalloid bodies that drastically reduces the fossilization potential. We recently published an account on an exceptionally well-preserved non-marine thalloid organism from the Triassic of the Transantarctic Mountains.8 This organism, Litothallus ganovex, occurs as compressions of rosette-like thalli (Fig. 1A) with associated cellular sheets (Fig. 1C and D). The exquisite preservation of the fossils enabled a detailed study of the peculiar anatomy of the organism. The thallus of L. ganovex consists of densely spaced, vertical cellular filaments that are laterally fused to form a sheet- or crust-like structure (Fig. 1B). Thalloid bodies containing such pseudotissues only occur in certain algae and lichens. It appears most likely that L. ganovex represents a freshwater macroalga based on its striking resemblance to certain extant freshwater representatives of the red algal order Hildenbrandiales. We speculated that L. ganovex may have been a widespread constituent of certain Triassic freshwater ecosystems that was simply overlooked by earlier workers because of its inconspicuous appearance; Litothallus superficially resembles a coaly film on a sediment bedding plane. Recently we had the opportunity to study the large collection of Mesozoic plant fossils from various localities in Antarctica housed at the Natural History Museum and Biodiversity Research Center of the University of Kansas, Lawrence, KS. It appeared that many slabs with Triassic plant fossils also contain abundant Litothallus specimens, which demonstrates that this organism was in fact more common than we had originally envisaged. In some of the slabs large accumulations of thalli may even form thin coaly layers in the sediment. Figure 1 The putative freshwater macroalga Litothallus ganovex (A–D) and other recently discovered enigmatic cuticular remains (E–I) from c. 225–195 million-year old sediments of the Transantarctic Mountains. (A) two thalli of L. ganovex ... We have also discovered other enigmatic organic remains of putative thalloid organisms in a similar mode of preservation. For example, bulk macerations of Early Jurassic (c. 195–200 million-year old) sediments from Section Peak in North Victoria Land, Antarctica, have yielded a particularly interesting fossil that consists of a dorsiventally organized cuticle with upper and lower surfaces still in physical association. Neither of the surfaces shows stomata or indications of vein courses. Instead, the upper surface (Fig. 1E) bears slit-like cavities that are lined with large hollow protrusions of the epidermal cells (Fig. 1F). Some of these protrusions possess an interior microrelief of helical ridges and furrows (Fig. 1G). The lower cuticle is comparatively thin and displays an orthogonal pattern of rectangular cells with intercalated roundish cells bearing peculiar tube-like, thick-rimmed pores of about 25 µm diameter (Fig. 1H and I). Remotely similar cuticle-like remains of unknown affinity have been reported from Silurian and Devonian deposits.9 Graham et al. have attempted to clarify the identity of these enigmatic Palaeozoic fossils by comparing them with experimentally degraded liverwort thalli.10 Extant liverworts were therefore subjected to a series of degradation treatments simulating the effects of decay and burial. These treatments produced isolated ventral cuticles with thick-rimmed tubular pores, which represent the remnants of broken-off rhizoids.10 While the purported similarity between the artificially degraded liverwort remains and the Silurian/Devonian cuticle-like fossils has later been questioned, it is interesting to note that some of the liverwort fragments illustrated by Graham et al. are almost identical to the Jurassic cuticle from Section Peak. At present we can only speculate about the biological affinities of the Section Peak fossil, but we suggest that it may represent a fragment of a thallose liverwort. In this context it is worth to draw attention to the extant liverwort genus Monoclea. In contrast to most other complex thallose liverworts, Monoclea thalli lack air pores and a clearly defined midrib.11 Rhizoids with diameters of 9 to 35 µm are scattered over the entire ventral surface.11 Moreover, Monoclea produces archegonia embedded between mucilage hairs in flask-shaped archegonial cavities on the dorsal side.11 Although highly speculative at present, the slit-like cavities of the Jurassic fossil may have had a similar function. We hope to obtain additional material from Section Peak that permits more detailed analyses and comparisons to further test our hypothesis regarding this highly remarkable Jurassic fossil. The current perception of thalloid organisms in the fossil record remains strongly biased for several reasons. Traditionally, intentional search for fossil thalloid organisms focuses almost exclusively on the Palaeozoic, and aims at resolving the earliest history of plant life on land. Reports on thalloid fossils from younger periods of Earth history are comparatively sporadic and often merely the result of incidental finds. Moreover, impression and compression fossils of thalloid organisms have often been misidentified (e.g., as fern aphlebiae, conifer twigs, arthropod cuticles or trace fossils), and consequently have been grouped together with superficially similar fossils that belong to entirely different organisms.12 The general scarcity of uncalcified thalloid organisms in the fossil record may therefore to a certain degree also be a result of these strong biases in collecting, identifying and ultimately in studying these often inconspicuous fossils. The search for fossil thalloid organisms, especially from post-Palaeozoic deposits, can greatly contribute to a more accurate reconstruction of the diversity and functioning of ecosystems through time. We hope that our recent discoveries of Litothallus and other wellpreserved, yet enigmatic thalloid fossils provide a stimulus for a reappraisal of this largely disregarded segment of life in the past.

Phycology or algology is the study of the algae. The word phycology is derived from the Greek word phykos , which means “seaweed.” The term algology , described in Webster's dictionary as the study of the algae, has fallen out of favor because it resembles the term algogenic which means “producing pain.” The algae are thallophytes (plants lacking roots, stems, and leaves) that have chlorophyll a as their primary photo synthetic pigment and lack a sterile covering of cells around the reproductive cells. This definition encompasses a number of plant forms that are not necessarily closely related, for example, the cyanobacteria which are closer in evolution to the bacteria than to the rest of the algae. Algae most commonly occur in water, be it fresh water, marine, or brackish. However, they can also be found in almost every other environment on earth, from the algae growing in the snow of some American mountains to algae living in lichen associations on bare rocks, to unicellular algae in desert soils, to algae living in hot springs. In most habitats they function as the primary producers in the food chain, producing organic material from sunlight, carbon dioxide, and water. Besides forming the basic food source for these food chains, they also form the oxygen necessary for the metabolism of the consumer organisms.

Organization of the paleontology collections at the New Brunswick Museum has uncovered the holotype of Thallites lichenoides (Matthew) Lundblad, a supposed Pennsylvanian bryophyte from New Brunswick. The specimen, one of the few reported Paleozoic bryophyte fossils from North America, is poorly preserved and needs to be re-evaluated in future reviews of Paleozoic bryophytes. The Pennsylvanian fossil, Thallites lichenoides (Matthew) Lundblad, has been included in reviews of Paleozoic bryophytes (Schuster 1966; Miller 1980; Krassilov Schuster 1984; Oostendorp 1987) and is listed among rare occurrences of Pennsylvanian thalloid plants in North America (DiMichele & Phillips 1976; Miller 1980). Matthew (1907) originally described the specimen as Rhizomorphia lichenoides, a possible Devonian lichen or fungus. He later considered the "Fern Ledges" fossil assemblage to be Silurian (Matthew 1910). Stopes (1914, p. 72) established the Pennsylvanian age of the fossil but, unable to examine the specimen, thought it "most unlikely that it is either a Thallophyte or a Lichen", suggesting it was more likely a fern aphlebia, an anomalous pinna on a frond rachis. Lundblad (1954) assigned Rhizomophia lichenoides to the form genus Thallites, used by Walton (1925) for plants exhibiting thalloid form, but of unknown affinity. Although Lundblad (1954) suggested it might be a xeromorphic hepatic related to Riccia, Schuster (1966) saw little merit in reaching this conclusion based on the nature of the material. Oostendorp (1987) followed Lundblad's classification, but did not record a location for the type specimen. It is unlikely that anyone in recent years has examined the holotype which has been warehoused in an uncatalogued part of the New Brunswick Museum collection. Matthew's holotype was discovered during recent organization of fossil collections. As with many of the compression fossils from the "Fern Ledges" locality, T. lichenoides is poorly preserved and may ultimately defy identification. THALLITES LICHENOIDES (Matthew) Lundblad, Svensk Botanisk Tidskrift 48: 406. 1954.

Single membrane bounded organelles characterized by a physical association with endoplasmic reticulum have been observed in a wide range of cell types and plant species including Gymnosperm, Angiosperm, Pteridophyte, and Thallophyte (algae and fungi) tissues. The morphological similarity between these organelles and animal microbodies suggests that they are cytological homologues. Plant microbodies were observed both with and without dense internal inclusions but unlike animal microbodies could not be shown to contain uricase. Plant microbody membranes are resistant to degenerative influences and remain associated with a small portion of endoplasmic reticulum even in isolated cell fractions.

Carbonate grains from the skeletal sands off the western Irish coast of Connemara (53°N latitude) are extensively bored by thallophytes, yet the borings, unlike those in warm-sea sediments, are not associated with cryptocrystalline carbonate (micrite). On the other hand, living Lithothamnium colonies and Lithothamnium fragments frequently have their cell cavities filled by high Mg-calcite micrite and, less commonly, parts of the algal skeleton may be micritized. In living colonies, the micrite is often confined to certain growth lamellae of the red alga. The presence of micrite as a void filler or as a replacement of preexisting carbonates is indicative of environments capable of precipitating metastable cements. The environments of precipitation may be depositional or post-depositional. All available evidence favors a biochemical precipitation mechanism in the micritization of the red algal skeletons, brought about essentially by the life activities of the organism. In the light of the present study, the significance of micritized grains within carbonate sediments is re-examined.