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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.

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.