Exceptionally preserved calcified sponge assemblagesin Upper Jurassic carbonates of the eastern Getic Carbonate Platform (Southern Carpathians, Romania)

A rich poriferan assemblage was identified within the easternmost part of the Getic Carbonate Platform of Romania (Grădiștei Gorges). The excellent preservation state of most poriferans here led to the discovery of a new species (Neuropora gigantea Pleș & Schlagintweit, n. sp.) and to the identification of previously unknown diagnostic features in some species (Sarsteinia babai Schlagintweit & Gawlick, 2006 emend., Neuropora lusitanica Termier, 1985, Sphaeractinia steinmanni Canavari, 1893). Calciagglutispongia yabei Reitner, 1992, Sarsteinia babai and Sphaeractinia steinmanni are reported for the first time from the Upper Jurassic carbonates of the Getic Carbonate Platform. The sedimentary input fluctuations and the nutrient competition had an important role in understanding the morphological adaptations of the analysed species. The existing palaeoecological and palaeoenvironmental conditions generated different distribution patterns towards the reef profile and also preferential adaptations to a specific Tethyan domain. As opposed to the poriferan assemblages from the northern Tethyan shelves, these organisms formed sponge-coral-microencruster boundstones at the margins and fore-reefal zones of isolated carbonate platforms within the intra-Tethyan realm. The importance of calcified sponges in reef-zonation is highlighted by the establishment of a general zonation model. Three zones can be distinguished: 1) Cladocoropsis-Milleporidium zone (back-reef area); 2) Bauneia-Chaetetopsis-Parastromatopora zone (central reef area); and 3) Sphaeractinia/Ellipsactinia-Neuropora zone for the fore-reef area. In the absence of a true reef framework these calcified sponges developed typical morphologies, environmental adaptations and partnerships with other biotic groups which strongly influenced the carbonate production throughout the intra-Tethyan domain.

Late Triassic thalamid sponges from Nevada

A study of Upper Triassic (Norian) thalamid sponges (“sphinctozoans”) from the Pilot Mountains, Garfield Hills, and East Range, Nevada, reveals an abundance of calcified sponges of the suborder Porata Seilacher. Two new species, Polycystocoelia silberlingi n. sp. and Neoguadalupia? norica n. sp., are added to our knowledge of five thalamid sponge taxa previously known from Nevada. All specimens have been neomorphically altered to calcite in a manner implying an original aragonite mineralogy.At the species level, the sponges show a restricted distribution. Nevadathalamia cylindrica (Seilacher) is a species also occurring in Sonora, Mexico, and previously known from the Yukon of Canada, but all other species are endemic to west-central and northwestern Nevada. At the generic level, similarities exist with species known from the Tethyan Realm, the Yukon, and south China. The genus Polycystocoelia has been known previously only from Hubei, China, and from the Yukon Territory, Canada. Neoguadalupia was previously known only from the Lower and Upper Permian of China. The occurrence of this genus in Nevada constitutes the first record of the genus outside of the Permian System of China.

Archaeocyath palaeoecology

A well preserved archaeocyath fauna occurs in the Forteau Formation in Southern Labrador, Canada. Following on from the confirmation that archaeocyatha are aspiculate calcified sponges, detailed ecological work is now being undertaken on this fauna, a representative of the first reefal ecosystem in the fossil record.One species, Metaldetes profundus, shows considerable variability in growth form, from open bowl-shaped forms in lagoonal settings, to a branching morphology in biohermal habitats. This species also appears to colonise a variety of substrate types and for this purpose often uses exothecal structures and holdfasts. M. profundus is also the dominant species numerically, comprising 80% of the fauna, except at the top of the bioherm horizon, where Archaeocyathus atlanticus becomes dominant. In contrast to previous studies' findings, bowl-shaped Metaldetes at the top of the bioherm horizon occupy the basal region of the bioherms, not the upper areas and provide a surface on which the bioherms can develop.The unique form of Retilamina amourensis endows it with the ability to stabilise substrates so facilitating the colonization of a substrate. It is more common at the base of bioherms, providing a surface on which other archaeocyaths can settle. The calcimicrobes Renalcis and Epiphyton also appear to have played a major role in the initiation of the bioherms, occurring as 3–5cm thick layers on erosion surfaces, within which small, juvenile, upright M. profundus sticks, <1cm in diameter, are found, surrounded and supported by the dense calcimicrobe aggregate.Digital 3-D analysis is being used to document the behaviour of the archaeocyaths, together with vertical and lateral zonation within the bioherms, especially with regard to the timing of calcimicrobe encrustation. Volumetric abundances of the archaeocyaths are also being calculated.There are small faunal composition changes over the area: Archaeosycon billingsi, a solitary stick-like form is more abundant in the west than in the east and Archaeocyathus atlanticus, another stick-like form occurs in dense clusters in lagoonal environments, elsewhere being solitary.

A synonymized nomenclature for calcified sponges

A synonymized nomenclature for calcified sponges (archaeocyaths, stromatoporoids, chaetetids, sphinctozoans and pharetronids) is here presented to enable comparison of suggested homologous structures.

A new Cambrian sphinctozoan sponge from North America, its relationship to archaeocyaths and the nature of early sphinctozoans

A new early Cambrian sponge of sphinctozoan organization named Polythalamia americana nov. gen. et sp. is described from Nevada and Alaska, U.S.A. P. americana nov. gen. et sp. shows little resemblance to other Cambrian reported sphinctozoans, but is similar to late Palaeozoic to early Mesozoic forms from Europe and Asia, e.g. Stylothalamia and Amblysiphonella. The polyphyletic origin of sphinctozoans based upon spicule criteria from younger examples is therefore corroborated by the varied morphology and clearly widespread palaeogeographic distribution of Cambrian forms, which were hitherto recognized only from Australia. P. americana nov. gen. et sp. possesses a relatively small, globular multi-chambered calcareous skeleton, with thin but densely perforate walls and a central retrosiphonate, perforate spongocoel. The skeleton is composed of an irregular microstructure of unknown, but probable calcitic, original mineralogy. There are no spicules or primary internal structures, but secondary vesicular filling tissue is present. The pore organization, however, it directly comparable to archaeocyaths, e.g. coscinocyathines, and this character is taken to be the only synapomorphy available for taxonomic and phylogenetic purposes. Indeed, P. americana nov. gen. et sp. is closely associated with a diverse archaeocyath assemblage and draws attention to morphological similarities between some archaeocyaths and sphinctozoans, thus questioning the criteria at present used to distinguish between these groups. Accordingly, a list of nomenclatural synonymies is given to aid comparison. Coscinocyathine archaeocyaths possess chambered juvenile stages and P. americana nov. gen. et sp. is suggested to represent an aspiculate lineage of sphinctozoan grade which may be derived from forms such as Clathricoscinus by neoteny. It appears that at least three clades of sphinctozoan-grade calcified sponges were present by end of early Cambrian time and their occurrence in association with island arcs of the palaeopacific rim is confirmed.