Bollettino SPI: Vol. 59 (3) 2020 - OPEN ACCESS!

Although medusoids (medusa-like fossils, putative medusae) are widely reported in the literature, there are only thirteen confirmed medusa-bearing deposits. These have a predictable and evolving distribution through time and across facies - including in coarse clastic sand flats where mouldic preservation predominates, restricted lagoonal facies where anoxia and hypersalinity fostered preservation, and offshore settings where rapid burial and early diagenetic mineralisation catalysed preservation. The medusan preservational window became progressively more restricted through the Phanerozoic. Preservation in sandy beach and sandflat facies is only known from the Cambrian, there are no open shelf medusa-bearing deposits after the Carboniferous, and the latest known lagoonal fossil medusae are from the lower Cenozoic. This restriction in occurrence through time is associated with changes in bioturbation, evolution of scavengers, occurrence of microbial mats, and possibly evolution of microbial communities. There is evidence of jellyfish blooms in five of the thirteen deposits, and medusan fossilisation may have been associated with anoxia caused by the partial decomposition of large masses of dead medusae.

The results of the study of a rugose coral collection from the southern part of the Donets Basin are presented herein. Some species that were only mentioned in previous Donets Basin faunal lists are described and illustrated. The genera Aulokoninckophyllum Sando, 1976 and Merlewoodia Pickett, 1967 are reported for the first time from the Donets Basin. The stratigraphic distribution of the studied species is analysed. The uneven distribution of corals in the Tournaisian of the Donets Basin is explained by a complex combination of regional paleogeographic conditions and global events. The studied stratigraphic levels with corals are compared with the coral zones and third-order sequences of the Belgian Namur-Dinant Basin.

Research in two quarries of the Borovichi area near the Uglovka town (northwestern Moscow Basin) has provided several rugose and tabulate corals that improve the knowledge on the palaeontology of that area. The Zarech’e quarry yielded rare specimens of Syringopora reticulata and Dibunophyllum bipartitum, as well as common specimens of Actinocyathus floriformis, A. borealis and A. crassiconus. The Uglovka quarry provided also Syringopora reticulata, Dibunophyllum bipartitum but different species of colonial rugosans: Actinocyathus sp., Lonsdaleia multiseptata and Schoenophyllum sp. The palaeogeographical distribution of the recorded species indicates a good communication of the Eastern European Basin with western and eastern Palaeotethys during the Serpukhovian. The presence of the genus Schoenophyllum suggests also connection with North America, probably along the northern coast of Laurussia.

An endosymbiotic relation between the solitary rugose corals ?Yuanophyllum and ?Dibunophyllum and a large soft-bodied worm-like organism is described from the Hezhou Formation (Serpukhovian), Lower Yangtze Platform, South China. The endosymbiont lived in a U-shaped tube, probably with a horizontally sideways bent base connecting the vertical shafts. A membranous epidermis and relicts of a probable cuticulo-muscular tube are preserved. The corals reacted with skeletal encasement of the infesting organism and irregular, in part dense growth of additional skeletal elements adjacent to it. This is the first description of such an endosymbiotic, parasitic or commensal relation of solitary rugose corals after the Frasnian-Famennian Boundary Event. Similarities between the Devonian association of pleurodictyoform tabulates and the ichnotaxon Hicetes are remarkable. Moreover, the association proves the extraordinarily rare persistence of bioclaustrations in corals after the Hangenberg Event at the Devonian-Carboniferous boundary during the Permo-Carboniferous period of arrested endosymbiont development.

The Bashkirian-lower Moscovian Valdeteja Formation crops out in the Cantabrian Zone (NW Spain). It is composed of pale grey limestone with a diverse fossil content, calcareous breccias and massive limestone composed of algal and microbial mounds accumulated in a high relief carbonate platform. Outstanding outcrops of that formation appear near the village of Truébano (León Province, North Spain) at the old coal mine “Mina Rosario.” The mine is a peculiarity in the formation as it shows interbedded siltstones and coal beds containing coal balls. The studied succession above the coal seam is lower Bashkirian and 20.2 m thick. Dark grey, massive to wellbedded limestones interbedded with thin marly beds are dominant in that interval. The main component of the limestones is the algospongia Donezella that is found in two different facies: packstone of resedimented Donezella, which appears in the lower beds of the section, and boundstone of Donezella, Girvanella and chaetetids, in the upper beds. Additional components are highly diverse including foraminifera, other calcified microbes, rhodophyta, sponges, echinoderms, arthropods, brachiopods, bryozoans and scarce corals and molluscs. Organic matter is abundant in the marly beds, but palynomorphs are poorly preserved. An interbedded layer of quartz sandstones lacking fossil content occurs in the upper part of the sequence. The depositional environment of the facies is part of a carbonate platform top near the fair-weather wave base, within subtidal zone, with development of “algal” mounds and sedimentation of debris from the same buildups. The composition and components distribution of both microfacies fit well with the mounds previously described in other outcrops of the Valdeteja Formation, with the exception of the participation of chaetetids as a main building component in some beds.

Studies of upper Palaeozoic corals from the Southern Alps (Karavanke Mountains in Slovenia and Carnic Alps along the Austrian/Italian border) started at the end of the 19th century. Since the mid-20th century, corals of the Karavanke Mountains have been studied in detail by several authors. Recently, several coral type localities and the coral groups occurring therein have been reinvestigated. This paper deals in particular with the study of Carinthiaphyllum Heritsch, 1936 and all previously known data have been revised within this study. Most specimens of Carinthiaphyllum originate from museum collections and from new findings in the Dovžanova Soteska area of northern Slovenia. Additional material is represented by newly found samples from the locality of Mt. Boč in eastern Slovenia. The stratigraphic position and age of the Carinthiaphyllum occurrences are determined by fusulinid and conodont assemblages. Two species, Carinthiaphyllum crasseseptatum Gräf & Ramovš, 1965 and C. ramovsi n. sp., are described herein. New morphological features, including root-like protrusions and connecting stereoplasmic tubes, have been found for the first time in gregaria growth mode. Therefore, these new observations provide evidence of a solitary gregaria growth mode: individuals are invariably separated with contact and reciprocal support only by root-like, sometimes channeled tubes occurring as outgrowths of the archaeothecal wall. An emended diagnosis of Carinthiaphyllum is proposed herein. The studied collection is housed in the Museum für Naturkunde (Leibniz-Institut) at the Humboldt University in Berlin.

Guadalupian (middle Permian) reef blocks of the Al Jil and Bai’d formations (Hawasina Nappes, Oman Mountains) contain rugose corals. Praewentzelella regulare, a fasciculate coral, is found in clusters, with more than 80% of the colonies in growth position. The good preservation of microstructure and minimal taphonomic alteration (e.g., lack of postdepositional tilt or transport of colonies) allow to discuss whether or not live-live interactions for space, particularly intraspecific competition, has been preserved. The evaluation is based on the distribution of coral colonies mapped in the field, three-dimensional reconstruction of coral growth using serial cuts of a block and microfacies evaluation of thin sections. A rarely observed phenomenon of intraspecific competition is described herein and the term “intra-clonal aggression” is proposed for interactions between sedentary organisms of the same species leading to the distortion of skeletal elements of one colony.

In colonial corals, the polyps are interconnected with a common tissue called coenosarc. Polyps and coenosarc secrete distinct skeletal structures: corallites and coenosteum, respectively. Ratio of corallite to coenosteum development may vary resulting in two extreme architectural patterns of coral colonies: corallite-dominated (e.g., cerioid) and coenosteum-dominated (e.g., aphroid) colonies. A large suite of examples of these patterns can be identified among extant and fossil corals, including Paleozoic rugosan corals. Herein we describe the new early Eocene colonial scleractinian coral genus Nancygyra that forms exceptional coenosteum-dominated colonies. The colonies were found in Ypresian limestones at Monte Postale (Lessini Mountains, Veneto, NE Italy), very close to the Pesciara di Bolca Fossil-Lagerstätte, where coralgal buildups have been recently recognised and described. The corallum is massive and consists of corallites of variable size (typically few millimeters in lesser calicular diameter) dispersed and protruding from a very extensive and dense dissepimental coenosteum. The coenosteum forms ca. 60-80% of the corallum volume and is made of vesicular convex dissepiments. The new coral is tentatively assigned to Euphylliidae (known in the fossil record since the Paleocene) whose modern representatives develop similar extensive coenosteum with sticking-out corallites (Galaxea) and form coralla with well-developed walls and thickened axial margins of septa (Euphyllia). Among stratigraphically older scleractinian corals, similar extent of dissepimental coenosteum development is shown by some Mesozoic amphiastreids and rhipidogyriids.

A diverse assemblage of bodily preserved sponges has been recovered from a lower Lutetian tuffite horizon in the Chiampo Valley, Lessini Mountains, Italy. The sponge assemblage is dominated by hexactinellids and lithistids. Using uniformitarian criteria, the composition of the assemblage suggests a water depth greater than 200 m. Sponges are often preserved in growth position including sponge clusters. Taphonomic processes facilitating sponge preservation include rapid burial of a living sponge community and early diagenetic calcification. Different modes of attachment suggest heterogeneous substrate conditions. The associated fauna, such as abundant pteropods in the matrix and in-situ preserved crinoids, confirms a rather deep-water environment. However, there are also common benthic elements of shallow-water origin. Although some of these elements show signs of transport, others, such as decapod crustaceans, do not. Moreover, trace fossils indicate high-energy environments. To reconcile these observations, we propose rapid, tectonically triggered sea-level changes.

In the Werlberg Member (Rupelian pro parte) of the Paisslberg Formation (Eastern Alps), an assemblage of colonial corals of eleven species pertaining to eleven genera and eleven families was identified: Stylocoenia carryensis, Acropora lavandulina, ?Colpophyllia sp., Dendrogyra intermedia, Caulastraea pseudoflabellum, Hydnophyllia costata, Pindosmilia cf. brunni, Actinacis rollei, Pavona profunda, Agathiphyllia gregaria, and Faksephyllia faxoensis. This is the first Oligocene coral assemblage reported from the Paisslberg Formation (Werlberg Member) of the Eastern Alps, consisting exclusively of colonial forms. The assemblage represents the northernmost fauna of reefal corals reported to date for Rupelian time. The Werlberg Member accumulated during marine transgression onto a truncated succession of older carbonate rocks. The corals grew as isolated colonies and in carpets in a protected shoreface setting punctuated by high-energy events. Coral growth forms comprise massive to sublamellar forms, and branched (dendroid, ramose) forms. The coral fauna is dominated by forms with medium- to large size corallites 4 to >10 mm in diameter. The assemblage consists of stress-resistant genera widespread in the Eocene to Miocene of central and southern Europe, Central America, and the Caribbean Islands. On the species level, closest correspondence is with faunas of southern Europe, especially with those of northern Italy (Lessini Shelf). On the genus-level, greatest affinities are with the lower Oligocene faunas of northern Italy (Lessini Shelf). Regarding similarities to other lower Oligocene faunas, seven genera have also been reported from Jamaica, Germany (Reit im Winkel), and Slovenia, and five genera were found in Greece. Ten (91%) of the described Austrian coral taxa from the Paisslberg Formation were found elsewhere in (sub)tropical reefal and peri-reefal settings. The caryophylliine coral Faksephyllia faxoensis, however, stands out as the only taxon which, in addition, has been reported from deep-water environments.

The lower Oligocene coral communities and reefs exposed in the Lessini Shelf of northern Italy may record one of the oldest well-developed barrier reef/lagoon systems of the Cenozoic. However, the rimmed-shelf interpretation has been repeatedly challenged in favour of a ramp model with scattered corals. Based upon a re-analysis of selected localities in the Lessini Shelf, we here provide support for the barrier reef model based on four key observations: 1) systematic changes of coral growth-forms from branching in the proximal areas to massive at the platform margin; 2) a progressive increase of the hydrodynamic energy from the proximal belt towards the more distal environments in the Berici Hills; 3) the occurrence of shallow-water, euphotic conditions throughout the whole depositional system; and 4) the presence of restricted circulation in the proximal environments during sea-level lowstands, with lack of coral colonies. These features, together with the evidence of coral frameworks located on the southeastern edge of the Lessini Shelf, substantiate the occurrence of a reef-rimmed margin. The reefal rim acted as an efficient barrier, with the formation of a landward, wide lagoon protected from the action of waves and currents.

The staghorn coral genus Acropora is the most diverse living genus of reef-building corals. From earliest records around the K-Pg event, the genus has a geo-history of strongly persistent morphological lineages, dating from 49 Mya to present and extending across the Eocene of England and Europe, Oligocene to early Miocene of Europe, Oligocene to present in the western Atlantic, and late Paleogene to present reef-bearing areas in the Indo-Pacific. Because of these records and the usually well-preserved Acropora fossils, it is regarded as an exemplar for studying modern diversity and distribution of reef corals and predicting their response to future climate change. Here we examine previously undocumented diversity of Acropora species groups present in Oligocene and Miocene (Suwannee Limestone and Tampa Member of the Arcadia Formation, respectively) deposits in Florida and southern Georgia, USA. We find evidence of both species-group lineages from the European region and novel, probably unique Atlantic lineages. Of 11 extant species-group lineages first present in the Eocene to Miocene of the European region, seven are present in this American material, including the cervicornis group, never recorded in the Indo-Pacific and now extant only in the western Atlantic. Two as yet undescribed species in the samples and the known species Acropora tampaensis Weisbord, 1973 could not be matched within the 19 species groups recognised in extant Acropora, and these may be lineages uniquely developed and lost in the Americas. The two species in the cervicornis species group, both now categorised as critically endangered, are the only surviving representatives of the family Acroporidae, which was previously represented by five genera in the western Atlantic. Acropora species from Florida and Georgia reefs clearly played a substantive role in the continuation and diversification of Acropora species groups during the Oligocene-Miocene in the western Atlantic and it is possible that this contributed to the success of the genus in the Indo-Pacific, as well as cervicornis group as a critical environmental feature of western Atlantic reefs.