Paleoecology and biostratinomy of solitary rugose corals in the Stony Mountain Formation (Upper Ordovician), Stony Mountain, Manitoba

1982 ◽  
Vol 19 (8) ◽  
pp. 1582-1598 ◽  
Author(s):  
Robert J. Elias
Keyword(s):  
Relative Frequency ◽  
Substrate Surface ◽  
Outer Wall ◽  
Post Mortem ◽  
Upper Ordovician ◽  
Growth Axis ◽  
Coral Size ◽  
Rugose Corals ◽  
External Form

The four species of solitary Rugosa known from the Stony Mountain Formation at Stony Mountain in southern Manitoba belong to different genera, and differ from one another in external form. The distribution and abundance of taxa and their frequency with respect to one another were related to the degree of environmental restriction. The boundary between the Gunn Member and overlying Penitentiary Member corresponds to a marked increase in overall abundance and change in relative frequency. Helicelasma and Bighornia are dominant in the Gunn and lower Penitentiary, respectively. Deiracorallium and Lobocorallium decrease in frequency at the boundary.Larvae of these solitary Rugosa attached to the substrate with their cardinal side. Coralla of Helicelasma, Deiracorallium, and Lobocorallium were oriented in the sediment with the top of the convex cardinal side at or near the substrate surface and the upper part of the concave counter side exposed above it during life. Bighornia lay with the convex counter side in the sediment and the concave cardinal side at least partly exposed. Epizoic bryozoans generally became associated with live hosts, and were especially common on the exposed side of relatively large individuals. Microscopic boring algae infested the outer wall of most corals in the Gunn Member, usually while the hosts were alive. Responses of the polyp to stress and injury are indicated by redirection of the growth axis, constriction of the calice rim, and repair of broken calice rims. The attitudinal and directional orientations of solitary corals suggest that most and possibly all were transported after death. Differences in depositional orientation among the taxa are related to coral form. Currents were unidirectional from the present southeast during Gunn time, and either unidirectional from the southeast or northwest, or oscillating from both directions in early Penitentiary time. Abrasion of coral exteriors was primarily a post-mortem event associated with transportation. Trypanites borings were probably produced by one species of annelid after deposition of the corals. The degree of abrasion and frequency of annelid borings tended to increase with coral size and the duration of exposure before burial.

Polychaete palaeoecology in an early Late Ordovician marine astrobleme of Sweden

2010 ◽  
Vol 148 (2) ◽  
pp. 269-287 ◽  
Author(s):  
MATS E. ERIKSSON ◽  
ÅSA M. FRISK
Keyword(s):  
Shallow Water ◽  
High Frequency ◽  
Relative Frequency ◽  
Late Ordovician ◽  
Crater Floor ◽  
Drill Core ◽  
Upper Ordovician ◽  
Composition Characteristic ◽  
Post Impact ◽  
Early Late

AbstractThe post-impact Dalby Limestone (Kukruse; Upper Ordovician) of the Tvären crater, southeastern Sweden, has been analysed with regards to polychaetes, as represented by scolecodonts. A palaeoecological succession is observed in the Tvären-2 drill core sequence, as the vacant ecospace was successively filled by a range of benthonic, nektonic and planktonic organisms. Scolecodonts belong to the first non-planktonic groups to appear and constitute one of the most abundant fossil elements. The polychaete assemblage recorded has an overall composition characteristic of that of the Upper Ordovician of Baltoscandia. Oenonites, Vistulella, Mochtyella and the enigmatic ‘Xanioprion’ represent the most common genera, whereas Pteropelta, Protarabellites?, Atraktoprion and Xanioprion are considerably more rare. The assemblage differs from coeval ones particularly in its poorly represented ramphoprionid fauna and the relatively high frequency of ‘Xanioprion’. A taxonomic succession and changes in abundance and relative frequency of different taxa is observed from the deepest part of the crater and upwards towards more shallow water environments. The initial post-impact assemblage does not, however, necessarily represent a benthonic colonization of the crater floor. Instead it seems to be a taphocoenosis, as indicated by its taxonomic correspondence to the rim facies fauna recovered from Dalby Limestone erratics of the Ringsön island. The Tvären succession has yielded considerably richer scolecodont assemblages than hitherto recorded from the approximately coeval Lockne crater, possibly as a consequence of shallower water settings in the former area.

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

1985 ◽  
Vol 59 (S16) ◽  
pp. 1-58 ◽  
Author(s):  
Robert J. Elias
Keyword(s):  
New Mexico ◽  
North America ◽  
High Energy ◽  
Low Energy ◽  
Red River ◽  
Energy Conditions ◽  
Upper Ordovician ◽  
Rugose Corals ◽  
Solitary Coral ◽  
Mountain Province

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.

Borings in solitary rugose corals of the Selkirk Member, Red River Formation (late Middle or Upper Ordovician), southern Manitoba

1980 ◽  
Vol 17 (2) ◽  
pp. 272-277 ◽  
Author(s):  
Robert J. Elias
Keyword(s):  
Relative Abundance ◽  
Red River ◽  
Marine Environments ◽  
Upper Ordovician ◽  
Shallow Marine ◽  
Rugose Corals

Borings occur in solitary rugose corals from the Selkirk Member of the late Middle or Upper Ordovician Red River Formation in southern Manitoba. They are assigned to Dictyoporus garsonensis n. ichnosp., which was produced by algae, and Trypanites weisei Mägdefrau 1932, made by spionid polychaete annelids. Most, and possibly all, boring occurred while the host corals were alive and in life position. The location and relative abundance of borings support interpretations that unattached curved solitary corals lay with the convex cardinal side in the sediment and the concave counter side facing upward during life, whereas straight conical forms were oriented upright in the sediment. These ichnospecies suggest that host corals lived in very shallow marine environments.

Paleobiologic significance of fossulae in North American Late Ordovician solitary rugose corals

Paleobiology ◽  
1984 ◽  
Vol 10 (1) ◽  
pp. 102-114 ◽  
Author(s):  
Robert J. Elias
Keyword(s):  
North American ◽  
Genetic Factors ◽  
Outer Wall ◽  
Reproductive Activity ◽  
Late Ordovician ◽  
Water Circulation ◽  
Central Cavity ◽  
Foreign Objects ◽  
Rugose Corals

Three features that provide information on the paleobiologic significance of fossulae in North American Late Ordovician solitary rugose corals are (1) irregularities in shape and position of the outer wall, (2) discontiguous septal growth lamellae, and (3) foreign objects incorporated into interseptal chambers within the corallum. Outer wall irregularities indicate that portions of a polyp could detach from the calice and could contract and expand radially by a significant amount and for prolonged periods of time during ontogeny, especially in the vicinity of the alar and cardinal fossulae. Discontiguous lamellae indicate that the polyp could detach from septa and contract laterally, especially in the cardinal fossula. This began with the onset of maturity and probably reflects reproductive activity. Ostracodes are the most common foreign objects in these coralla and are usually situated within or near the cardinal and alar fossulae. In the most likely hypothesis accounting for their presence, a live ostracode entered the calice when one side of the polyp temporarily detached from the corallum and contracted radially. It became trapped upon expansion and reattachment of the soft parts. The polyp moved upward in its corallum by detachment and uplift of the aboral surface. In a less likely hypothesis, the ostracode was captured by the coral for food and came to rest on the floor of the central cavity. It was incorporated into an interseptal chamber when the polyp moved upward in its corallum by atrophy of the aboral surface and formation of a new base above the object. In either hypothesis, portions of the polyp in the cardinal and alar fossulae probably functioned throughout ontogeny for water circulation in the central cavity, and for the intake of food and/or ejection of undigested material through the mouth. Taxonomic, stratigraphic, and paleobiogeographic variability in frequencies of the three features may indicate differences in the necessity and/or ability of polyps to perform these functions involving the fossulae. This could be a reflection of environmental and/or genetic factors.

External morphology and paleobiology of Heliophyllum halli (Zoantharia, Rugosa), from the Middle Devonian Hamilton Group of New York State

2001 ◽  
Vol 75 (1) ◽  
pp. 24-33 ◽  
Author(s):  
James E. Sorauf
Keyword(s):  
New York ◽  
Middle Devonian ◽  
Early Recognition ◽  
New York State ◽  
Outer Wall ◽  
Polyp Size ◽  
Efficient System ◽  
York State ◽  
Rugose Corals ◽  
Hamilton Group

Heliophyllum halli contains highly variable, mostly solitary rugose corals. Specimens reported here come from shaly beds of the Middle Devonian Hamilton Group in New York State. Early recognition of morphotype variation led James Hall to establish numerous species in the H. halli group that were later interpreted by John Wells in terms of varying life history. Life on unstable and/or soft substrates was facilitated for these corals by talons, root-like structures that allowed larval settling and post-larval development on hard particles such as echinoderm or shell debris. Variation in subsequent growth history is reflected in corallum shape and change in diameter. Straight growth axes reflect partial burial accompanied by vertical growth, while growth axis curvature resulted from unequal settling into substrate or alternatively, life at the surface of substrate, with sharp bends (geniculations) reflecting major changes in growth orientation. Decrease in diameter resulted from environmental stress, with greatest effects on the peripheral portion of the calice. Other major reactions to increased burial rate (through sinking or increased sedimentation) are epithecal secretion to form an outer wall for isolation of itself from surrounding sediment or decrease in polyp size as shown by terminal shrinking of the corallum diameter, at times nearly to zero. Yonge's (1940) summary of observations on living coral polyps suggests that the living H. halli was nonzooxanthellate, with an efficient system of feeding that utilized its multitude of tentacles without the help of cilia, which thus were able to generate currents to promote efficient sediment cleansing. Sediment shedding would also have been aided by polypal distension (swelling) above a reflexed calical margin.

Late Ordovician solitary rugose corals of the St. Lawrence Lowland, Québec

1990 ◽  
Vol 64 (3) ◽  
pp. 340-352 ◽  
Author(s):  
Robert J. Elias ◽  
Danita S. Brandt ◽  
T. H. Clark
Keyword(s):  
Sedimentation Rate ◽  
Source Area ◽  
High Energy ◽  
Late Ordovician ◽  
Energy Conditions ◽  
Upper Ordovician ◽  
Delta Front ◽  
The North ◽  
Rugose Corals ◽  
Lowland Area

Two species of solitary rugose corals occur in Late Ordovician strata of the St. Lawrence Lowland. Grewingkia canadensis (Billings, 1862) appears in the upper part of the Nicolet River Formation (upper St. Hilaire Member) and is far more common in the overlying Pontgravé River Formation. A single specimen of Streptelasma divaricans (Nicholson, 1875) is known from the Pontgravé River. Their presence confirms that this area is situated within the Richmond Province and that the upper Nicolet River, as well as the Pontgravé River, is Richmondian in age. Solitary Rugosa were introduced to this biogeographic province during an early Richmondian transgression, marked in the upper Nicolet River Formation by a coarser clastic interval. That event permits correlation between the St. Lawrence Lowland in the eastern part of the Richmond Province and the North American type Upper Ordovician (Cincinnatian Series) of the Cincinnati Arch region in the western part of the province.A comparative morphologic, paleoecologic, and biostratinomic analysis of solitary corals indicates that normal, low-energy conditions were interrupted occasionally by high-energy events (probably storms) during deposition of the upper Nicolet River and Pontgravé River Formations. Water depth increased northwestward in the St. Lawrence Lowland area. Deposition of these siliciclastic prodelta to delta front sediments was generally continuous and the sedimentation rate was usually high because of rapid basin subsidence and comparatively close proximity to the Taconic Mountains. In the western part of the Richmond Province, farther from the source area, carbonate as well as clastic sediments accumulated, periods of nondeposition were more frequent, and the sedimentation rate was relatively low. Corals disappeared from the St. Lawrence Lowland area during the Richmondian, when delta top facies of the Bécancour River Formation succeeded the Pontgravé River Formation due to a glacio-eustatic regression and progradation of the Queenston Delta.

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