Solitary Rugosan Research Articles

SYMBIOSIS OF RUGOSE CORALS WITH THE CYSTOPORATE BRYOZOAN FISTULIPORA PRZHIDOLENSIS IN THE PRIDOLI (LATEST SILURIAN) OF SAAREMAA, ESTONIA

ABSTRACT In the Silurian, the most common hosts of endobiotic rugose corals were stromatoporoids followed by tabulate corals. Here we describe the relationship between rugose corals and a bryozoan. Solitary rugosans and the cystoporate bryozoan Fistulipora przhidolensis Kopajevich, 1990 formed a symbiotic association in the late Silurian (Pridoli) of Saaremaa, Estonia. The syn vivo nature of the association is indicated by complete intergrowth of both organisms and the perpendicular orientation of the rugosans to the bryozoan growth surface. There are one to seven endobiotic rugosans per bryozoan colony. This is the first detailed study of coral-bryozoan symbiosis from the Silurian; all previous reports describe Late Ordovician, Devonian, or Cenozoic material. The lack of malformations and decrease in the size of bryozoan zooids near the rugosans suggest there were no strong negative effects of the rugosans on the bryozoan. The rugosans likely benefited from their association with the bryozoan, which served as an anchor to stabilize them in hydrodynamically active waters, and the bryozoan may have benefited by protection against some types of predators. The associations described here were most likely mutualistic.

Epizoans immured in the heterocoral Oligophylloides maroccanus Weyer, 2017: a unique record from the Famennian (Upper Devonian) of Morocco

Exceptionally well-preserved proximal parts of colonies of the late Famennian heterocoral Oligophylloides maroccanus Weyer, 2017 with immured epizoans are described here from the Jebel Bou Ifarherioun ridge of the eastern Anti-Atlas, Morocco. This is the first evidence of unique syn vivo interactions between a heterocoral and numerous epizoans, that is the colonial tabulate corals Zemmourella? sp. and Aulopora? sp.; solitary rugose corals Czarnockia? sp. and Gorizdronia? sp.; and other juvenile, undeterminable solitary rugosans, crinoids, as well as microbial structures. Detailed analysis of sectioned specimens allowed mutual interactions to be traced during growth of the host and infesting encrusting taxa. The studied associations show that the epizoans must have settled on the proximal parts of Oligophylloides in places devoid of soft tissue. The encrusted proximal portions of the colonies show that soft tissue of the heterocoral could have retracted and expanded again, fouling and immuring dead epizoans. The process of bioimmuration is perfectly marked by thin layers of microbial encrustations developing on the epibiont skeletons prior to their overgrowth by the skeleton of the heterocoral. The studied encrustations seem to be widespread, but the association provided the epizoans with additional substrate for encrustation, as well as an elevated position above the seafloor, beneficial for access to nutrients. We suggest that the host bioimmured the encrusters after their death, because of noticeable microbial encrustations and veneers of sediment, a lack of malformations, relatively rapid growth and aggressive activity of epizoans.

Crouching shells, hidden sponges: Unusual Late Ordovician cavities containing sponges

Marine cavities harbouring cryptic organisms have been ubiquitous throughout the Phanerozoic. However, our knowledge of early cryptic communities is as yet insufficient, and how metazoans began to utilize such habitats remains unknown. In this study, we document demosponge remains within intraskeletal cavities embedded in the micritic succession of a shallow carbonate platform in the Upper Ordovician (Katian) Xiazhen Formation of South China. Molluscs (gastropods, bivalves, and nautiloids) and corals (the solitary rugosan Tryplasma and colonial agetolitids) within the succession commonly contain patches of “spicular” demosponge remains (11%; n=45/415), mainly occupying intraskeletal spaces with areas of 1–30mm2 in thin-section. Sponge occurrence varies according to sedimentary facies: within lime mudstone facies, sponges commonly occur both inside and outside intraskeletal cavities, suggesting that sponges would have inhabited and become preserved within any available space in this environment. In contrast, when other sessile organisms co-occur in wackestone to packstone facies, there are fewer sponge occurrences both inside and outside cavities, possibly due to competition in open habitats and/or their poorer preservation in such environments. Overall, this result suggests that sponges would have exploited cryptic habitats by normal expansion of the open-surface biota. In addition, compared with coeval reef and hardground crypts, the Xiazhen intraskeletal cryptic biota is monotonous in composition, suggesting “decoupled” occupation of cryptic habitats in different environments.

Stability strategies and hydrodynamic behavior of liberosessile solitary rugose corals (Ordovician; Red River–Stony Mountain Province, North America)

In the Late Ordovician Red River–Stony Mountain Province of North America, four closely related genera of solitary rugose corals are represented exclusively by liberosessile species: Salvadorea, Grewingkia, Deiracorallium, and Lobocorallium. These rugosans benefitted from innovative and in some cases unique strategies involving corallum form, which improved stability with respect to the substrate and currents, and took advantage of water flow during life. Trochoid form was a compromise for ensuring adequate stabilization of the corallum by sediment, while keeping the calice rim sufficiently elevated above the substrate. In life orientation with the convex cardinal side of the corallum facing down, triangulate and trilobate cross-sectional shapes offered resistance to lateral tipping or rotation. Depressed coralla resisted gravity-induced subsidence or tilting. With the convex side facing downcurrent, the streamlined shape of compressed and triangulate forms improved stability by reducing drag. Trilobate form may have had a drag-reducing “splitter plate” effect. Strategies for drag reduction were especially beneficial for corals inhabiting relatively high-energy environments, but the greatest significance may have been in reducing fatalities due to dislodgement during storms. The hydrodynamic behavior of coralla in life position, especially if leaning downcurrent, resulted in beneficial water flow. Vortices ascending from the substrate on the downcurrent side provided the polyp with water drawn from both the mainstream and the substrate surface. Such circulation facilitated feeding, enhanced the quantity and variety of food, and delivered other necessary substances. Wastes and gametes could be effectively expelled from the polyp and removed downcurrent without entrainment into the food-bearing flow. Functional analysis of the fascinating range of corallum forms in the Red River–Stony Mountain Province provides insight into paleobiology and paleoecology, which is applicable to many Paleozoic solitary rugosans.

Paleoecology of Framebuilders in Early Silurian Reefs (Brassfield Formation, Southwestern Ohio)

Abstract The framebuilding fauna of an Early Silurian (Aeronian, Llandoverian), Brassfield Formation reef from west-central Ohio is examined in detail. Brassfield reefs are among the very few Silurian reefs of the midcontinental United States that are not dolomitized. Species-level taxa identified in the framebuilding fauna include two favositid corals, two proporid corals, two halysitid corals, two colonial rugosan corals, and at least four stromatoporoids. Favositids, halysitids, crinoid holdfasts, and bryozoans are distributed fairly evenly across the reef; colonial rugosans and solitary rugosans are more abundant along the windward side of the reef; and stromatoporoids are more abundant on the leeward side. The Brassfield reef fauna resembles that from the Jupiter Formation (Aeronian), Anticosti Island, and the Manitoulin Formation (Aeronian), Manitoulin Island; however, there are differences in total diversity and composition. Paleogeographic positioning, local water depth, and access to open-ocean c...

Discussion of ‘Palaeocurrent direction and velocity in the Great/Main Limestone on the Alston and Askrigg blocks of northern England’: Proceedings , Vol.52, part 4, pp. 353–359, 1999

C. T. Scrutton writes: I read with interest R. A. Fairbairn’s excellent article on the determination of the current directions dominant during the deposition of the Great Limestone in Northern England. The corals that he mentions, which occur in abundance at certain levels within the limestone, could provide some additional information on the conditions prevailing at the time. The solitary rugosans, principally Dibunophyllum bipartitum , lived as straight to slightly curved coralla, more or less upright in the sediment and corresponding to type Evii and particularly Fvii coralla as illustrated in my recent paper (Scrutton 1998, fig. 14). Three factors would have determined their stability, the extent to which they sank down into the soft lime-mud substrate with increasing growth and weight, the consistency of that substrate, and the degree of sediment build-up around them. During life in an environment below fair-weather wave base, conditions were probably reasonably calm with only light current activity. Persistent stronger currents would have resulted in asymmetrical scour around the coral-sediment interface, producing more strongly horn-shaped coralla (Scrutton 1998, fig.14). However, very few specimens are now found in position of growth. Fairbairn (1999, p. 354) reported that many specimens are found prone and aligned on bedding planes, with their long axes at right angles to the prevailing current direction. This disorientation, as he notes, was most likely due to the effects of intermittent storms scouring the supporting sediment and inducing toppling, with subsequent current activity resulting in the alignment of the prone coralla. In addition, it ...

Coral diversity, ecology, and provincial structure during a time of crisis; the latest Ordovician to earliest Silurian Edgewood Province in Laurentia

The latest Ordovician to earliest Silurian Edgewood Province in the cratonic interior of Laurentia contained a post-extinction coral fauna. These corals inhabited a broad range of shallow-marine, carbonate environments. Diversity generally increased along a gradient from restricted, low-energy, relatively turbid conditions, to open, high-energy, low-turbidity conditions. Changes in diversity involved progressive addition or subtraction of stenotopic species within a single association dominated by opportunistic, ecologic generalists. Patterns and trends in diversity, abundance, and distribution reflected locally variable environmental parameters and an overall gradient from the continental interior toward the open ocean. Structural characteristics of the Edgewood Province differed from those of Late Ordovician pre-extinction and Early Silurian recovery faunas in the Laurentian cratonic interior. These included the low total diversity, the abundance and strong dominance of a single, solitary rugosan species, and the lack of distinct, specialized, recurring species-associations. The origin, overall structure, and fate of the province were determined by factors operating on a broad scale. Nutrient enrichment and related environmental destabilization in the Laurentian epeiric sea during the end-Richmondian regression were probably significant factors in extinctions among Late Ordovician perched faunas, including corals. This would have occurred as nutrients provided by runoff from expanding terrestrial areas became concentrated in the shrinking sea. During the Gamachian and early Rhuddanian, elevated nutrient levels and environmental instability within the small sea were likely instrumental in maintaining the structure of the Edgewood Province. By the late Rhuddanian, transgression had expanded the sea and reduced the effects of runoff sufficiently to permit the Silurian recovery of corals.

A Middle Devonian Temperate Water Limestone - Isotopes, Stromatoporoids and Shallow Water Facies: ABSTRACT

The Edgecliff Member of the Middle Devonian Onondaga Formation has long been of interest to exploration geologists because its pinnacle reefs and bioherms are potential natural gas reservoirs. Current evidence indicates that the Edgecliff was deposited in a shallow, temperate water environment suggesting that application of standard tropical carbonate models will be misleading. Three lines of evidence support the temperate water model for the Edgecliff. Carbon and oxygen isotopic analyses performed on 29 samples from the non-luminescent portions of 15 brachiopods with prismatic ultrastructure yield {delta}{sup 18}O values which are isotopically heavier than accepted values for Devonian sea-water, suggesting cool water conditions. The distribution of stromatoporoids (assumed warm water organisms) ranges from rare and small in the eastern part of New York State, to more common in Ontario, Canada. This trend in stromatoporoids appears to represent an increase in size and abundance as the distance from the paleo-equator decreases. Finally, previously unrecognized shallow water facies in the Edgecliff including thin, dolomitized and bioturbated carbonate muds, solitary rugosan biostromes and ridge-like fringing coral bioherms negate any possibility that the isotopic and paleobiologic data reflect deposition in deep, cooler waters as opposed to an overall temperate water environment.

The Silurian (Wenlockian) Reef Fauna of Southeastern Wisconsin

The Racine Formation of southeastern Wisconsin contains a diverse reef fauna of Silurian (Wenlockian) age. A collection of more than 10,000 specimens from this fauna includes 191 species and 38 guilds of reef constructors, binders, bafflers and dwellers. Constructors and binders include stromatoporoids, tabulates, rugosans and bryozoans; bafflers include branching tabulates and dendroid rugosans. Only locally do these groups form a skeletal framework, and for the most part, their remains are separated by reef matrix. Reef dwellers are represented by diverse guilds of brachiopods, gastropods, cephalopods, trilobites and echinoderms, and they also include receptaculitids, sponges, solitary rugosans, bryozoans and bivalves

Ordovician-Silurian mass extinction and recovery: coral faunas in the east-central United States

Three successive coral faunas that are involved in the Ordovician-Silurian mass extinction and recovery occur in latest Ordovician (Richmondian-Gamachian) to earliest Silurian (early Llandovery; Rhuddanian) strata of the east-central United States. The Richmondian fauna comprises typical cratonic North American Late Ordovician corals. In the Cincinnati Arch region, these belong to the Richmond Province and include massive stauriids (e.g., Favistina), sarcinulids (e.g., Foerstephyllum, Calapoecia), and common tetradiids. In the upper Mississippi Valley region, corals belong to the Red River-Stony Mountain Province and include the streptelasmatid Salvadorea. The disappearance of typical Ordovician-type coral faunas from the interior of eastern North America was related to habitat loss resulting from progradation of the Queenston delta and regression of the epeiric sea during a major glacio-eustatic drop in the late Richmondian.The succeeding fauna of Gamachian to early Rhuddanian age represents the Edgewood Province. The solitary rugosan Streptelasma is dominant; colonial rugosans are rare and are all fasciculate. The principal tabulates are Paleofavosites, Propora, and Halysites; sarcinulids are absent. Rare tetradiids (Rhabdotetradium) are among the youngest representatives worldwide of an important Ordovician order. The Edgewood fauna includes first occurrences of typical Silurian taxa: the earliest North American halysitine (Halysites), the oldest definite plasmoporid (Plasmopora), and the earliest known pycnostylid (Pycnostylus). The striking difference between Richmondian and Edgewood faunas in the east-central United States reflects, at least in part, a hiatus between Richmondian and Gamachian deposition. Corals were introduced to the Edgewood Province from the continental margin, or were derived from forms previously restricted to the continental margin. This occurred during minor transgressions from the south, as sea level fluctuated during a regressive phase corresponding to the Gamachian glacial maximum. Immigration was evidently related to shifts of suitable habitat areas during a time of depressed temperatures. Edgewood corals dispersed farther northward during the early phase of the major latest Gamachian to Early Llandovery transgression associated with deglaciation.Corals are uncommon in late Rhuddanian strata immediately above those containing the Edgewood fauna. This Silurian fauna includes the solitary rugosans Rhegmaphyllum, Dinophyllum, Dalmanophyllum, and Cyathactis?, which were not derived from Edgewood taxa. Colonial rugosans are absent. The tabulates belong to Paleofavosites, Propora, and Halysites, the dominant colonial genera in the Edgewood fauna. At least some of the species were likely derived from Edgewood forms; others may have been introduced from elsewhere, or perhaps were derived from species in other areas. A slight stratigraphic overlap of several Edgewood and Silurian species is known at one locality, but the faunal change is otherwise abrupt. The changeover from Edgewood to Silurian faunas took place as water depth and temperature were generally increasing during the Rhuddanian. However, corals of the Silurian fauna appear above intraformational channels in one area and above unconformities or formational boundaries elsewhere, suggesting that the change occurred during an intervening regressive event. It is inferred that as areas in the east-central United States became inhospitable, geographic ranges of Edgewood corals were reduced. Most species became extinct; some colonial corals apparently underwent rapid evolution, probably in small populations. The descendants dispersed and new immigrants arrived as suitable habitat areas expanded when the Early Llandovery transgression resumed. A few Edgewood colonial species survived for a short time, evidently in local refugia. Unlike the colonial corals, all solitary forms known from the Silurian assemblage were immigrants. Corals of the Silurian assemblage probably favored somewhat deeper water than those of the Edgewood Assemblage.

Paleoenvironmental reconstruction based on horn corals, with an example from the Late Ordovician of North America

Rugosan horn corals are a common constituent in many Ordovician and younger Paleozoic marine units. Analyses of coral curvature, orientation, condition of the coral surface, associated borings and epizoans, and features in the surrounding matrix can provide information on the nature and intensity of environmental energy, mode and rate of sedimentation, and changes in sediment consistency. This permits paleoenvironmental reconstruction on a local and regional scale. A thin unit of dolomitic limestone and dolostone at the top of the Elgin Member in the Maquoketa Formation (MaysvillianRichmondian) of southeastern Minnesota is unique among documented North American Late Ordovician strata bearing horn corals. A substantial proportion of individuals in these beds are preserved in situ and some of them are in life position. Deposition evidently occurred in relatively deep water above but near storm wave base, where the competence of currents generated during high-energy events was only moderate. These are considered to be the deepest-water solitary Rugosa known from Maysvillian-Richmondian epicontinental deposits of eastern and central North America. Within this region, horn corals in utits that are lateral equivalents of the Maquoketa were transported and generally reworked repeatedly in shallower-water environments where the competence of storm-generated currents was high. The results of this study support the hypothesis that water depth was an important factor controlling the distribution of Late Ordovician solitary rugosan species.

Symbiotic relationships between worms and solitary rugose corals in the Late Ordovician

Symbiotic relationships involving physical contact between worms and solitary rugosan polyps are recorded by the following structures in North American Late Ordovician corals: (1)Trypanitesborings enclosed within septal swellings in two specimens, (2) vermiform grooves and openings along the external wall of one corallum, and (3) a chamber containing a unique brown tube within one individual. These features are indicative, respectively, of commensal boring polychaete annelids that penetrated through coralla, commensal epizoic worms of unknown taxonomic affinity that attached to the side of a polyp, and a tubicolous worm (possibly a polychaete) that was likely a parasitic endozoan. Symbionts comparable to the latter two types are also known from two specimens of Devonian solitary rugose corals.Indirect evidence suggests that symbioses between solitary rugosans and the worms that producedTrypanitesborings as dwelling structures in the sides of coralla were relatively common. However, direct evidence that the hosts were alive has been found in only two corals. In both cases, worms bored through septa within the calices and came into contact with basal surfaces of the polyps, which secreted skeletal material that sealed off the intruders. The rarity of such structures suggests that the encounters were inadvertent. If boring worms favored upcurrent portions of objects in order to maximize feeding benefits and avoid sedimentation, their locations indicate that the concave sides of curved coralla faced toward prevailing currents when in life positions.“Opportunistic” worms are known to have attached to the sides of polyps only in rare instances when the hosts became temporarily exposed as a result of accidents or abnormalities. This indicates that coralla normally served to shield polyps from colonization by nonboring epizoans.Worms that apparently extended up through openings in basal surfaces of polyps likely obtained sustenance parasitically within the central cavities. They could have entered the hosts through their mouths, or via the calices when parts of the polyps detached from their coralla and contracted radially. The rarity of this type of relationship in solitary Rugosa suggests that the worms entered inadvertently.Symbioses involving physical contact between worms and polyps seem to have been rare throughout the history of solitary rugose corals. Both groups apparently tolerated such associations when they did occur, although the rugosans secreted structures in their coralla that served to isolate the symbionts. In doing so, they recorded the presence of worms not likely to be preserved as body fossils. The interpretation of such features provides information on the physiology and ethology of both organisms, on the history of symbiotic relationships, and on the diversity of soft-bodied organisms in ancient environments.

Solitary Rugose Corals of the Upper Ordovician Montoya Group, Southern New Mexico and Westernmost Texas

The Upper Ordovician (middle Edenian to upper Richmondian) Montoya Group of southern New Mexico and westernmost Texas comprises, in ascending order, the Second Value Dolomite, Aleman Formation, and Cutter Dolomite. Solitary rugose corals in the Second Value are Grewingkia robusta (Whiteaves, 1896), Bighornia sp. cf. B. patella (Wilson, 1926), Streptelasma divaricans (Nicholson, 1875), a new species of Neotryplasma, and Salvadorea? spp. A and B. Salvadorea kingae kingae Nelson, 1981, G. franklinensis n. sp., and G. crassa alemanensis n. subsp. occur in the Aleman. Taxa found in the Cutter are S. kingae cutterensis n. subsp., G. sp. cf. G. franklinensis, and B. sp. cf. B. patella.Grewingkia robusta is the most abundant species in the solitary rugosan assemblage that is present within the Second Value. This assemblage apparently inhabited comparatively deep-water environments. Most of the corals lived in relatively high-energy conditions, but epizoic forms favored low-energy niches. Salvadorea kingae is the most common taxon in the assemblage that characterizes the Aleman-Cutter. This is probably a comparatively shallow-water assemblage. The dominant taxon inhabited relatively low-energy environments, while less common species lived in higher energy conditions. If the distribution of solitary rugose corals in the area of Montoya deposition was related primarily to water depth, a paleobathymetric gradient from relatively deep in the west to predominantly shallow in the southeast existed through Second Value–Aleman time. During Cutter time, water was relatively deep in the southwest and northeast, and predominantly shallow in the southeast. If the degree of environmental restriction was the principal factor limiting the distribution of Montoya solitary Rugosa, open normal marine environments were predominant in the southeast and uncommon in the north and west.Montoya representatives of Grewingkia, Bighornia, and Salvadorea indicate that the area of deposition was situated within the Red River–Stony Mountain Solitary Coral Province, which occupied most of North America during Late Ordovician time. All species of these genera are typical “epicontinental” forms. Neotryplasma, the only “continental margin” taxon, reflects a cratonic margin paleoposition. The discovery of Streptelasma divaricans within Edenian-Maysvillian strata in the Montoya is consistent with an hypothesis that solitary Rugosa were introduced to the Richmond Solitary Coral Province of eastern North America during an early Richmondian transgression.Within the Red River–Stony Mountain Province, geographic speciation and dispersion seem to have been important factors in the evolution and diversification of Grewingkia robusta and related taxa, including G. haysii selkirkensis n. subsp. from the Selkirk Member of the Red River Formation in southern Manitoba. In Salvadorea, speciation events within the New Mexico–Texas area and Williston Basin were apparently rapid, and coincided with onsets of clastic deposition. Evolutionary change within this genus has not been recognized in the Hudson Bay Basin, where there were no clastic influxes.In the Aleman-Cutter sequence of the Montoya Group, recognition of specific intervals bearing solitary rugose corals may permit detailed biostratigraphic, and possibly chronostratigraphic, correlation. The change from a Grewingkia-dominated assemblage to a Salvadorea-dominated assemblage was not synchronous throughout the Red River–Stony Mountain Province, and the ranges of widely distributed species such as G. robusta and S. kingae cannot be considered isochronous from basin to basin. Within particular basins, endemic taxa having restricted stratigraphic ranges, such as G. crassa alemanensis, can be useful biostratigraphic markers. Streptelasma divaricans remains useful as a Richmondian index fossil in strata within the area occupied by the Richmond Province.