Die Korallenfauna des Korallenooliths (Oxfordium, Oberjura, NW-Deutschland): Zusammensetzung, Stratigraphie und regionale Verbreitung

The stratigraphie and regional distribution of Oxfordian scleractinian reef corals in the Korallenoolith Formation (NW German Malm Group) is described from the Süntel, Deister, Kleiner Deisler and Osterwald Mountains. In the study area four horizons with (par-) autochthonous corals are developed two of which can be traced region-wide (Untere Korallenbank Member andflorigemma-Bank Member / Obere Korallenbank Member). The coral fauna of the biostromes, forming the Untere Korallenbank Member, is impoverished and dominated by ubiquitous r-strategists. In contrast, the reefal bioconstruetions of theflorigemma-Bank Member show a high variability in their regional appearances, partly forming highly diverse coral associations. The highest diversity is developed in the patch reefs from the Obere Korallenbank Member of the Osterwald Mountains (about 40 species). Corals are an important part of the Korallenoolith fauna. Altogether, 20 species belonging to 15 genera have been identified which were formerly unknown from NW German Oxfordian successions.     

Morphology and sedimentology of (clustered) cold-water coral mounds at the south Rockall Trough margins,NE Atlantic Ocean

Cold-water coral mounds on both margins of the Rockall Trough (NE Atlantic Ocean) have a strongly different morphology. Single, isolated mounds occur on the SE margin and are mainly found on the upper slope between 900 and 650 m water depth, while large mound clusters are found on the SW margin in water depths between 600 and 1,000 m, in a narrow zone almost parallel to the slope. Sedimentation rates on the mounds are higher than on the surrounding seabed as a result of baffling of biogenic carbonate debris and siliciclastic particles by the coral framework covering the mounds. This is confirmed by ²¹⁰Pb measurements. The individual coral growth rate can be three times higher then the vertical growth rate of the coral cover (±10 mm year⁻¹) which in turn is more than an order of magnitude higher then the present-day overall mound growth rate (±0.25 mm year⁻¹). The presence of extensive hardgrounds and firmgrounds and the three-dimensional coral framework are considered to be responsible for the stability of the relatively steep slopes of the mounds. High current velocities in the intramound areas result in local non-sedimentation and erosion, as is shown by the presence of IRD (ice-rafted debris) lag deposits on the seabed and moats around some of the mounds. The morphology and sedimentology of cold-water coral-covered (mainly Lophelia pertusa and Madrepora oculata) mounds on the southern Rockall Trough margins (NE Atlantic Ocean) is discussed and a model describing the development of these mounds is presented.     

Ecophenotypic asymmetry in the middle Danian brachiopod Obliquorhynchia flustracea caused by adaptation to attachment on the coral Dendrophyllia candelabrum

The rhynchonellid brachiopod Obliquorhynchia flustracea from the middle Danian (Paleocene) cool‐water coral mounds of the Faxe Formation, Denmark, exhibits commissural asymmetry, a rare feature in articulate brachiopods. It has been much discussed whether the underlying reasons for this asymmetry were species specific caused by pedicle attachment in the limited space between the branches of the scleractinian Dendrophyllia candelabrum. The two species are always found together, and the brachiopod is essentially missing outside facies characterized by D. candelabrum. Based on morphological analyses and statistical tests, we suggest that ecophenotypic variation is the main reason for the variability in the external shell morphology and development of commissural asymmetry. Conditions such as sexual dimorphism and defects can be dismissed as a facilitating reason of phenotypic variation. This is a rare case where it is possible to directly link commissural asymmetry to mode of attachment on a specific host.     

河北唐山西域山晚寒武世长山组的树形笔石

本文对东秦岭南部湖北郧西地区早石炭世四射珊瑚进行了研究,系统描述了11科中的24属和39种,其中包含2新属和21新种。本区早石炭世四射珊瑚拟划分为4个组合带:范家坪组上部Palaeosmilia-Lithostrotion组合带,下部Yuanophyllum组合带。袁家沟组上部Shennongia majus组合带,下部Zaphrentoides组合带。范家坪组是新建的组名。文中也讨论了Cystophrentis的分布时限,及其与Shennongia的亲缘关系。此外,Neoclisiophyllum在本区与岩关期的Shennongia共生,出现的时间早于华南各地。     

悬浮物对造礁石珊瑚营养方式的影响及其适应性研究进展

营养方式是造礁石珊瑚获取能量与营养物质的基础,影响其生长与分布。近年来珊瑚礁区悬浮物含量与组分结构发生显著变化,其对造礁石珊瑚营养方式的诸多影响正成为当前研究热点。研究系统综述了珊瑚礁区悬浮物变化特征、悬浮物对造礁石珊瑚营养方式的影响及其适应性研究现状。发现近年来人类活动加剧与强降雨事件频发是驱动珊瑚礁,尤其是近岸珊瑚礁区悬浮物含量递增、组分改变与变频加剧的主因;悬浮物变化对造礁石珊瑚光合自养与异养营养的影响存在显著的种间差异,这主要与悬浮物消光效应、生物可利用性及造礁石珊瑚种类密切相关。虽然少数种类造礁石珊瑚具光合可塑性或异养可塑性,能在高含量悬浮物存在的弱光环境中较好生长。然而对绝大多数造礁石珊瑚而言,其营养方式适应性较差,无法在悬浮物影响下较好地获取生命活动所需的能量与营养物质,进而难以生存。总体来说,悬浮物被认为是近年来影响造礁石珊瑚生长与分布的重要环境因子之一,而关于造礁石珊瑚营养方式对悬浮物变化的响应及其适应机制,当前研究仍较薄弱,需要进一步加强相关研究。     

Cold‐water coral habitats on seamounts: do they have a specialist fauna?

Aim The large biogenic structures formed by colonial cold‐water scleractinian corals provide valuable habitat for marine invertebrates on seamounts and the continental slope of all world oceans. These patchily distributed long‐lived structures are easily damaged by several human activities, particularly bottom trawling for fish, and are potentially vulnerable to ocean acidification caused by climate change. Consequently, an important conservation question is whether these structures support a specialized invertebrate fauna restricted to these habitats. Here we investigate the relationship between structures formed by the coral Solenosmilia variabilis and its associated ophiuroid (brittlestar) fauna, one of the dominant components of deep‐sea ecosystems. Location Seafloor habitat around Southern Australia, New Zealand, and the Macquarie Ridge from 35 to 53° S and 117° E–176° W, 500–1500 m depth. Methods Data were derived from samples collected by numerous scientific expeditions to the study region. Because these samples were collected using a variety of gear and effort, a two‐step approach was used. First, the largest consistently collected data set (73 ophiuroid species from 59 samples) was assembled for multivariate analysis. ANOSIM was used to test for differences in ophiuroid community composition between Solenosmilia and non‐Solenosmilia habitat on seamounts and the continental slope, and SIMPER was used to identify species that characterized Solenosmilia habitat. Second, these results were validated against all known data to ensure that these characteristic species had not been found in non‐Solenosmilia habitat elsewhere. Results The ophiuroid assemblages from Solenosmilia habitat were distinct from those found on other habitats on the continental slope and offshore seamounts across the study region. Although a suite of ophiuroid species characterized Solenosmilia habitat, most have also been collected from dead coral or other rubble, suggesting a physical rather than biological association between the coral matrix and its associated invertebrate fauna. Main conclusions Despite the lack of an exclusive ophiuroid–coral relationship, cold‐water scleractinian coral remains the principal habitat for a number of ophiuroid species across southern Australia and New Zealand. The slow growth rate of the coral and the low dispersal potential of some associated species suggest that recovery of damaged cold‐water coral assemblages will be a long‐term process.     

Records and palaeoenvironmental conditions of Early Miocene scleractinian corals from the Fırat formation (Diyarbakır,Turkey)

Miocene scleractinian corals were documented for the first time in the Fırat Formation of Sarıca village, Eğil district of Diyarbakır, SE Turkey. The fauna consists of four hermatypic species belonging to three families: Diploastrea taurinensis (d’Achiardi, 1868), Tarbellastraea reussiana (Milne-Edwards and Haime, 1850), Echinopora gemmacea (Lamarck, 1816) and Montastraea pelouaensis (Chevalier, 1954). The morphospecies described here are typical of the early Miocene (Aquitanian-Burdigalian) and show that the Fırat Formation coral community was composed of shallow and subtropical reefs of Mediterranean Tethys palaeobiogeographical affinity. The examined species are reef components found in tropical and subtropical oceans, as are the majority of zooxanthellae. The species were upper photic zone related, had massive colonial growth morphology, and lived in a shallow tropical-subtropical marine palaeoenvironment at a depth of up to 50 m. They grew on hard ground, clean water, and normal salinity and required a minimum seawater temperature of 18 ̊C; however, they were most abundant at water temperatures ranging from 22 to 26 ̊C in high-moderate water energy. Consequently, this fossil assemblage will not only improve our knowledge of scleractinian coral diversity and morphological variation in SE Turkey but will also provide an important background for future studies of coral taxonomy, diversity and biogeography of the region.     

Franken Mound: facies and biocoenoses on a newly-discovered “carbonate mound” on the western Rockall Bank,NE Atlantic

Cold-water coral carbonate mounds are widespread along the Irish continental margin. Whereas the Porcupine Seabight and the Rockall Trough are relatively well studied with regard to mound topography, coral coverage, and benthic life diversity, the situation on the western Rockall Bank is rather unknown. Detailed facies and biocoenoses mapping based on video footage analyses was conducted on the newly-discovered Franken Mound. Facies were identified ranging between cliff-like to planar hardgrounds and soft sediments that are partly rippled. A variety of biocoenoses are associated with these facies comprising discrete live coral colonies, dense live and dead coral framework coverage, abundant to scattered coral debris, and a soft sediment faunal community, whereas the latter is three times less speciose as biocoenoses containing live framework-building corals. The facies and biocoenosis classes are supplemented by exposed dropstones, lost fishery nets, and rubbish. The distribution of the classes clearly indicates a close relationship with local current effects and current intensification. Due to the dominance of dead coral framework and the partially exposed internal sediment sequences on the mound flanks, it is assumed that Franken Mound is approaching the “mound retirement” mound growth state.     

Reef-Building Corals of Vietnam as a Part of the Indo-Pacific Reef Ecosystem

The paper analyzes both published and unpublished results of the investigations of Vietnamese reef-building corals and reefs performed in the last decades of the twentieth century. The state of the art in the study of reef-building scleractinian corals and reefs is presented. The scleractinian fauna of Vietnam is shown to match in species diversity (366 species of 70 genera) the tropical coral fauna of the Indonesian-Malacca fertile center, from which Indo-Pacific reef-building corals originated. The whole Vietnam coast from the Gulf of Tonkin to the Gulf of Siam is a biogeographically single whole and is a part of the Indo-Polynesian Province of the Indo-Pacific Area.     

滇东北昭通箐门的泥盆纪珊瑚(三)———晚泥盆世早期的四射珊瑚*

云南昭通市东北郊箐门出露了一条比较完整的泥盆纪浅海相地层剖面,下、中、上三个统均有出露,浅海底栖生物化石丰富,研究基础也相对较好,是研究滇东北地区泥盆纪地层的一条理想剖面。由于地层剖面比较长,沉积厚度比较大,此前笔者已经描述了早泥盆世和中泥盆世的四射珊瑚,本文继续描述该剖面的晚泥盆世的地层及其四射珊瑚,讨论它们的地层划分、珊瑚群对比与古生物地理。昭通箐门剖面的上泥盆统主要由白云质灰岩组成,与滇东其它地方的宰格组的岩性基本一致。过去由于宰格组的化石稀少,其地层时代难于确定,因此,昭通箐门宰格组底部珊瑚化石的发现具有重要意义。文中首次描述了箐门放羊冲剖面宰格组底部的四射珊瑚5属7种,包括Disphyllum catenatum,Hexagonaria davidsoni,H.magna,Sinodisphyllum simplex,S.variabile,Temnophyllum poshiense和Truncicarinulum temeniophylloides等,总体显示了晚泥盆世弗拉早期(early Frasnian)的特点。它除了与华南各省的珊瑚群有密切关系外,也与加拿大西部的分子有一定的联系。     

The distribution of scleractinian corals in the Bay of Biscay, NE Atlantic

Studies on the distribution of scleractinian corals in the Bay of Biscay were relatively numerous during the nineteenth and the first half of the twentieth century. Yet, recent reports are scattered, sometimes unpublished, and therefore knowledge about the current coral occurrence in the area is limited. This study aims at compiling the available historical and more recently collected information on the occurrence of scleractinian corals in the Bay of Biscay. Data from two recent cruises are included and compared with previous explored coral sites from as early as 1830 up to 1995. A database of 347 records including 34 described species of scleractinians highlights that the slope of the Bay of Biscay is an important habitat for scleractinians. This could be expected due to the high topographic relief providing the necessary hard substrate and accelerated bottom current flow that corals require. Further exploration of the occurrence and ecology of corals in the area is recommended to support the conservation of cold-water coral reefs along the European margin. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Competitive strategies of soft corals (Coelenterata: Octocorallia). II. Variable defensive responses and susceptibility to scleractinian corals

Interactions involving competition for space between several species of alcyonacean and scleractinian corals were assessed experimentally on Britomart Reef, central region of the Great Barrier Reef, Australia. Colonies of three soft coral species, Sarcophyton ehrenbergi Marenzeller, Nephthea brassica Kukenthal, and Capnella lacertiliensis Macfayden Forskal (Coelenterata:Alcyonacea) were relocated within stands of two scleractinian corals, Parités andrewsi Vaughan (= P. cylindrica Dana) and Pavona cactus Förskal (Coelenterata:Scleractinia). Undisturbed scleractinian and relocated alcyonacean controls were also monitored.Alcyonacean corals induced necrosis of tissue in scleractinian corals. Necrosis was significantly more pronounced when colonies were in contact but was also observed in the absence of contact, implicating the presence of active allelopathic agents. Scleractinian coral species varied in their susceptibility to the ill effects of alcyonaceans, with Pontes andrewsi being more susceptible than Pavona cactus. Of the soft corals, Nephthea caused the highest degree of mortality in the two scleractinian corals examined and Sarcophyton the least. Some soft corals appear to retain their toxins while others release them, implying a combination of anti-predatory and anti-competitor roles for the secondary metabolites. Scleractinian corals were often overgrown by soft corals.Both species of scleractinian corals were found to cause approximately equal amounts of tissue necrosis in alcyonaceans. These effects were more pronounced when colonies were in direct contact. The necrotic effects among alcyonacean corals were species-specific. Alcyonaceans also overgrew scleractinian corals and secreted a protective polysaccharide layer in areas proximal to scleractinians. Secretion of this layer was stimulated differentially by the two scleractinian species and also varied in frequency of occurrence among the alcyonaceans.High levels of tissue necrosis were observed in both groups of organisms within 3 wk of initiation of the experiment. Necrosis increased with time in the scleractinian corals and decreased in the alcyonaceans. The development of a protective polysaccharide layer in the alcyonaceans increased with time.     

新疆准噶尔盆地周边晚石炭世的珊瑚*

新疆北部准噶尔盆地周边石炭系广泛出露, 其中上石炭统发育海相火山—沉积序列, 包括西准噶尔地区的哈拉阿拉特组、阿腊德依克赛组, 东准噶尔地区的石钱滩组以及盆地南部的祁家沟组、奥尔吐组等。本文研究在上述各地层的灰岩层或夹层、碎屑岩中获得的四射珊瑚9属17种和床板珊瑚2属3种, 对石钱滩组中的3个新种进行了详细的系统古生物学描述。上述珊瑚化石的地质时代主要为巴什基尔期至莫斯科期。在珊瑚动物群的组成上, 哈拉阿拉特组中新发现Caninophyllum属分子, 结合盆地东、西部共同产出的床板珊瑚Cystodendropora 属分子, 说明整个准噶尔盆地周边的动物群面貌大致类似, 而西准噶尔地区的化石丰度、分异度显著低于盆地东部和东南部。综合前人资料, 目前在准噶尔盆地周边发现的珊瑚化石有约一半为地方性分子。本文认为研究区珊瑚化石的分布和组成特征与晚石炭世准噶尔洋走向封闭或半封闭的演化趋势密切相关。     

新疆准噶尔盆地周边晚石炭世的珊瑚*

新疆北部准噶尔盆地周边石炭系广泛出露, 其中上石炭统发育海相火山—沉积序列, 包括西准噶尔地区的哈拉阿拉特组、阿腊德依克赛组, 东准噶尔地区的石钱滩组以及盆地南部的祁家沟组、奥尔吐组等。本文研究在上述各地层的灰岩层或夹层、碎屑岩中获得的四射珊瑚9属17种和床板珊瑚2属3种, 对石钱滩组中的3个新种进行了详细的系统古生物学描述。上述珊瑚化石的地质时代主要为巴什基尔期至莫斯科期。在珊瑚动物群的组成上, 哈拉阿拉特组中新发现Caninophyllum属分子, 结合盆地东、西部共同产出的床板珊瑚Cystodendropora 属分子, 说明整个准噶尔盆地周边的动物群面貌大致类似, 而西准噶尔地区的化石丰度、分异度显著低于盆地东部和东南部。综合前人资料, 目前在准噶尔盆地周边发现的珊瑚化石有约一半为地方性分子。本文认为研究区珊瑚化石的分布和组成特征与晚石炭世准噶尔洋走向封闭或半封闭的演化趋势密切相关。     

Paleoecology of Middle Ordovician stromatoporoid mounds in Vermont

Fossiliferous mounds of carbonate mud are a distinctive facies in the middle Chazy Group (Crown Point Formation) at Isle La Motte, Lake Champlain. The mounds are surrounded by bedded calcarenite of spar-cemented pelmatozoan debris. Channels which cut into the mounds during mound growth are filled with the same calcarenite. The mud-free intermound rocks and the mound biota suggest agitated, normal marine shallow-water environments. The principal lime-secreting organisms within the mounds are stromatoporoids, calcareous algae, tabulate corals, sponges, and bryozoans. Each mound is dominated in terms of biomass by one of three groups: stromatoporoids, calcareous algae, and bryozoans. Most of the mound biota first appear at the base of the Crown Point Formation. In the lower Crown Point Formation the organisms increase in number and species. Both changes in the biota are related to periods of shallowing of the Chazy sea which are also reflected in the character of the carbonate sands.     

Cold-water coral reef frameworks,megafaunal communities and evidence for coral carbonate mounds on the Hatton Bank,north east Atlantic

Offshore banks and seamounts sustain diverse megafaunal communities, including framework reefs formed by cold-water corals. Few studies have quantified environmental effects on the alpha or beta diversity of these communities. We adopted an interdisciplinary approach that used historical geophysical data to identify topographic highs on Hatton Bank, which were surveyed visually. The resulting photographic data were used to examine relationships between megafaunal communities and macrohabitat, the latter defined into six categories (mud, sand, cobbles, coral rubble, coral framework, rock). The survey stations revealed considerable small-scale variability in macrohabitat from exposed Late Palaeocene lava flows to quiescent muddy habitats and coral-built carbonate mounds. The first reported evidence for coral carbonate mound development in UK waters is presented, which was most pronounced near present-day or former sites of topographic change, suggesting that local current acceleration favoured coral framework growth and mound initiation. Alpha diversity varied significantly across macrohabitats, but not between rock and coral rubble, or between smaller grain sized categories of cobbles, sand and mud. Community composition differed between most macrohabitats, and variation in beta diversity across Hatton Bank was largely explained by fine-scale substratum. Certain megafauna were clearly associated with particular macrohabitats, with stylasterid corals notably associated with cobble and rock habitats and coral habitats characterized by a diverse community of suspension-feeders. The visual surveys also produced novel images of deep-water megafauna including a new photographic record of the gorgonian coral Paragorgia arborea, a species not previously reported from Rockall Plateau. Further interdisciplinary studies are needed to interpret beta diversity across these and other environmental gradients on Hatton Bank. It is clear that efforts are also needed to improve our understanding of the genetic connectivity and biogeography of vulnerable deep-water ecosystems and to develop predictive models of their occurrence that can help inform future conservation measures. An erratum to this article can be found at     

Loss of Symbiodinium from bleached soft corals Sarcophyton ehrenbergi, Sinularia sp. and Xenia sp.

The deleterious effects of temperature-induced coral bleaching, a process by which corals lose their endosymbiotic algae (zooxanthellae; genus Symbiodinium) primarily at temperatures above mean yearly maximums, has not been well described for alcyonacean soft corals (Coelenterata, Octocorallia). The study of Symbiodinium cells lost from Sarcophyton ehrenbergi, Sinularia sp., and Xenia sp., which have not been compared in bleaching studies, indicate that the soft coral S. ehrenbergi released the greatest number of symbiont cells, however, it was less susceptible to heat stress surviving temperatures of 34 °C for >39 h. Sinularia sp. showed intermediate levels of bleaching tolerance to elevated temperatures, surviving prolonged exposures at 32 °C, but dying within 24 h at 34 °C. Xenia sp., however, was the most vulnerable to high heat stress maximally releasing Symbiodinium at temperatures ≤30 °C. This evidence indicates that Xenia sp. is even more susceptible to elevated temperatures than Acropora spp., previously reported to be the most vulnerable coral species to elevated temperature-induced bleaching.

Molecular analysis showed that the more resistant soft coral species (S. ehrenbergi) had the same type of Symbiodinium (clade C) as less resistant soft corals (Xenia sp.). In comparison to scleractinian corals collected from the same region that show similar bleaching resistance to high temperatures (e.g. Porities solida—more robust; Favites complanata—moderate resistance; Acropora hyacinthus—less robust), all scleractinian corals were symbiotic with Symbiodinium from clade C. A. hyacinthus, however, was found to possess multiple symbionts (clades B and C), and this represents a first report of Clade B in any Acropora species.     

Heterotrophy in Tropical Scleractinian Corals

The dual character of corals, that they are both auto- and heterotrophs, was recognized early in the twentieth Century. It is generally accepted that the symbiotic association between corals and their endosymbiotic algae (called zooxanthellae) is fundamental to the development of coral reefs in oligotrophic tropical oceans because zooxanthellae transfer the major part of their photosynthates to the coral host (autotrophic nutrition). However, numerous studies have confirmed that many species of corals are also active heterotrophs, ingesting organisms ranging from bacteria to mesozooplankton. Heterotrophy accounts for between 0 and 66% of the fixed carbon incorporated into coral skeletons and can meet from 15 to 35% of daily metabolic requirements in healthy corals and up to 100% in bleached corals. Apart from this carbon input, feeding is likely to be important to most scleractinian corals, since nitrogen, phosphorus, and other nutrients that cannot be supplied from photosynthesis by the coral's symbiotic algae must come from zooplankton capture, particulate matter or dissolved compounds. A recent study showed that during bleaching events some coral species, by increasing their feeding rates, are able to maintain and restore energy reserves.
This review assesses the importance and effects of heterotrophy in tropical scleractinian corals. We first provide background information on the different food sources (from dissolved organic matter to meso- and macrozooplankton). We then consider the nutritional inputs of feeding. Finally, we review feeding effects on the different physiological parameters of corals (tissue composition, photosynthesis and skeletal growth).     

A high‐stress shelly fauna associated with sponge mud‐mounds in the Coniacian Arnager Limestone of Bornholm,Denmark

The benthic macrofaunas of the Upper Cretaceous chalk of NW Europe show characteristically high species‐richnesses and commonly high densities. They are predominated by bivalves, brachiopods, polychaetes, echinoids, crinoids, asteroids, sponges and towards the end of the Cretaceous also by bryozoans. The mound‐bedded chalk of the Coniacian Arnager Limestone on the island of Bornholm in the Baltic Sea, Denmark, differs from this general picture. It was deposited on a small fault block adjacent to the main Bornholm block, which was emerged during much of the Mesozoic and thus occupied a much more proximal position than most other Upper Cretaceous chalks in NW Europe. The Arnager Limestone contains a unique, exceptionally rich and well‐preserved fauna of mainly hexactinellid, lyssacinosan sponges. The low mud‐mounds are interpreted as formed by baffling and trapping of fine sediment particles by the dense sponge thickets. In contrast, the associated shelly fauna is unusually sparse, of very low richness and extremely low density, except for inoceramid bivalves. It represents a strongly depauparated version of the shelly faunas of contemporaneous chalks in NW Europe. The rare specimens of non‐inoceramid shelly species are interpreted to represent occasional successful spatfalls of benthic species from the deeper‐water chalk farther offshore in the Baltic area. The sponge mud‐mounds of the Arnager Limestone show remarkable resemblances with modern sponge mounds recently discovered on the continental shelf of western Canada. They form an important link between the well‐known older Mesozoic sponge mud‐mounds or ‘reefs’ and the modern mounds and are among the youngest examples of Mesozoic sponge mounds.     

Contribution to the scleractinian corals of Hanifa Formation,Upper Jurassic,Jabal Al-Abakkayn,central Saudi Arabia

Eighteen scleractinian coral species belonging to 13 genera, 8 families and 4 suborders have been identified from the lower and upper parts of the Upper Jurassic (Oxfordian) Hanifa Formation at Jabal Al-Abakkayn, central Saudi Arabia. Actinastrea bernensis, A. crassoramosa, Coenastraea hyatti, Stylina kachensis, Cryptocoenia slovenica, C. wegeneri, Isastrea hemisphaerica, I. bernensis, Montlivaltia cornutiformis, M. frustriformis, Collignonastraea jumarensis, Ovalastrea michelini and Vallimeandropsis davidsoni are believed to be recorded for the first time from the Jurassic rocks of central Arabia. Most corals have massive hemispherical and globular forms, and few corals have dendroid and conical growth forms. They occur as small, isolated patches, about 0.5 m thick and about 10–30 m wide, in argillaceous reefal limestones. The identified corals show Africa, north America, northern, southern and western Europe, and southern or eastern Asia corals. The low diversity and abundance as well as the small size of colonies are attributed to inimical palaeoecological factors throughout the reefoids formation such as muddy substratum, water turbidity, high rate of sedimentation.