Carboniferous biostratigraphy of rugose corals

Rugose corals are one of the major fossil groups in shallow-water environments. They played an important role in dividing and correlating Carboniferous strata during the last century, when regional biostratigraphic schemes were established and may be useful for long-distance correlation. Carboniferous rugose corals document two evolutionary events. One is the Tournaisian recovery event, with abundant occurrences of typical Carboniferous rugose corals such as columellate taxa and a significant diversification of large, dissepimented corals. The other is the changeover of rugose coral composition at the mid-Carboniferous boundary, which is represented by the disappearance of many large dissepimented taxa with complex axial structures and the appearance of typical Pennsylvanian taxa characterized by compound rugose taxa. The biostratigraphic scales for rugose corals show a finer temporal resolution in the Mississippian than in the Pennsylvanian, which was probably caused by the Late Paleozoic Ice Age that resulted in glacial-eustatic changes and a lack of continuous Pennsylvanian carbonate strata. The Pennsylvanian rugose corals are totally missing in the Cimmerian Continent. High-resolution biostratigraphy of rugose corals has so far only achieved in few regions for the Mississippian time scale. In most regions, more detailed taxonomic works and precise correlations between different fossil groups are needed.

Reef Fish Associations with Natural and Artificial Structures in the Florida Keys

Throughout the Caribbean, coral reefs are transitioning from rugose, coral-dominated communities to flat, soft coral-dominated habitats, triggering declines in biodiversity. To help mitigate these losses, artificial structures have been used to re-create substrate complexity and support reef inhabitants. This study used natural and artificial structures to investigate the factors influencing the use of habitat by reef fish. During 2018 and 2019, divers added artificial structures and monitored the fish assemblages associating with both the artificial structures and naturally occurring corals. Overall, there were more fish on natural structures than on artificial structures. While structure shape did not influence fish use, there was a non-significant trend for increased use of larger structures. Fish observations did not differ across a gradient of shallow, complex reefs to deeper, flatter reefs; however, analyses of feeding guilds revealed clearer patterns: herbivores and omnivores were positively associated with low rugosity reefs where macroalgal abundance was higher, whereas invertivores preferred more rugose reefs. These results suggest that as reefs lose structural complexity, fish communities may become dominated by herbivores and omnivores. It also appears that the addition of artificial structures of the type used here may not mitigate the effects of structure loss on reef fish assemblages.

Labechia carbonaria Smith 1932 in the Early Carboniferous of England; affinity, palaeogeographic position and implications for the geological history of stromatoporoid-type sponges

Stromatoporoid sponges were very abundant during the middle Palaeozoic Era and are thought to disappear at the end of the Devonian Period in the Hangenberg Crisis. However, there are records of organisms with stromatoporoid-type structure in Carboniferous strata, the subject of this study. The Viséan fossil Labechia carbonaria Smith 1932 has been discussed previously in literature and its affinity has not been confirmed. In this study, the type material of L. carbonaria collected from the middle part of the Frizington Limestone Formation (previously called Seventh Limestone), Holkerian Substage, stored in the Natural History Museum (London, UK) and British Geological Survey (Keyworth, UK) was re-examined. The Holkerian Substage, in which L. carbonaria was found, lies between ca 335–339 Ma, and the Frizington Limestone Formation ranges from topmost Arundian to upper Holkerian, so middle Frizington Limestone Formation is likely approximately 337 Ma. L. carbonaria comprises thick long pillars connected by thin curved cyst plates consistent with the structure of the stromatoporoid genus Labechia. However, a common opinion is that L. carbonaria fossils may be mistaken for fragments of rugose corals, but there are problems with assigning it to the Rugosa. In vertical section (VS) L. carbonaria could be mistaken for a transverse section (TS) of a Carboniferous rugose coral. However, in TS L. carbonaria shows the rounded cross sections of stromatoporoid pillars. If it was a coral, septal sheets of the VS of a coral should be seen. For a rugose affinity to still apply, a coral structure would have to be composed of free trabeculae, but these are not known after the middle of the Devonian Period; there are no corals of Early Carboniferous age with the structure of L. carbonaria. Another interpretation, that L. carbonaria is a chaetetid, is discounted because it lacks calicles and is very different in structure from chaetetids. We conclude that L. carbonaria is a stromatoporoid. Because the beginning of the Carboniferous Period was ca 359 Ma, stromatoporoids thus occur approximately 22 million years after their purported disappearance at the end-Devonian Hangenberg Crisis. L. carbonaria, together with other rare occurrences in Carboniferous strata of stromatoporoid-form sponges Newellia mira (Newell) in USA, and uncertain taxa Komia Korde and Palaeoaplysina Krottow that have been attributed to stromatoporoids by some authors, supports some published views that end-Devonian stromatoporoid extinction may not have been as final as is traditionally interpreted. Thus Mesozoic stromatoporoids may represent resurgence of sponge lineages that survived the late Palaeozoic, perhaps in uncalcified form. Palaeogeographically, during the Early Carboniferous, the UK was positioned in low latitudes and in a central location of global distribution of reefal buildups during the late Palaeozoic continental assembly towards Pangaea. Thus it is curious that L. carbonaria is found in only one place; future search may determine its true palaeographic distribution, with potential reconsideration of the extinction of stromatoporoids at the end of the Devonian Period.

Late Permian rugose corals from Gyanyima of Drhada, Tibet (Xizang), Southwest China

The rugose corals described in this study were collected from the Gyanyima section in the Ngari region of southwestern Tibet (Xizang) and are assigned to three genera and 11 species, including a new genus and seven new species: Waagenophyllum (Waagenophyllum) ngariense He, 1990; W. (W.) elegantulum He in Luo et al., 1989; W. (W.) minutum Zhao, 1981; W. (W.) tachtabulasicum Ilyina, 1997; W. (W.) gyanyimaense n. sp., W. (W.) intermedium n. sp., Waagenophyllum (Liangshanophyllum) clisicolumellum n. sp., Ipciphyllum naoticum n. sp., I. floricolumellum n. sp., I. zandaense n. sp., and Gyanyimaphyllum crassiseptatum n. gen. n. sp. Ontogeny and intraspecific variation are given special attention when describing and discussing these taxa. Coral reefs, with Waagenophyllum as the major skeletal reef builder, occur in several horizons in the uppermost part of the section. The accompanying foraminifers indicate the rugose coral fauna is a late Permian Changhsingian age. Therefore, this is possibly one of the latest Permian rugose coral reefs in the world known up to now.UUID: http://zoobank.org/b9e621cb-197d-4208-8267-14d62f382a1b