Species definition in heliolitine corals of the lower Douro Formation (Upper Silurian), Canadian Arctic

1989 ◽  
Vol 63 (6) ◽  
pp. 819-838 ◽  
Author(s):  
Owen A. Dixon
Keyword(s):  
Canadian Arctic ◽  
Morphological Plasticity ◽  
Distinct Species ◽  
Discrete Variation ◽  
Species Definition ◽  
Septal Development ◽  
Upper Silurian ◽  
Intercolony Variation ◽  
Lithistid Sponge ◽  
Sponge Reefs

Specimens representingHeliolites diligensBondarenko, 1966,H.aff.H. luxarboreusYang, 1978, andH. tchernysheviBondarenko, 1966, are common andHeliolitessp. andStelliporellasp. are rare in diverse coral assemblages associated with lithistid sponge reefs in deep shelf or ramp limestone facies of the Douro Formation.Heliolites diligens, a more widely adapted, possibly “opportunist” species, occurs abundantly in lower diversity stromatoporoid/coral assemblages from nonreefal, shallower shelf limestone facies. Detailed systematic study of approximately contemporaneous populations of these Ludlovian heliolitid species shows that all are morphologically variable; assessment of this variability qualitatively and quantitatively is critical to species definition and recognition.Heliolites diligensis the most variable, with wide intercolony variation in septal development, corallite wall configuration, and spacing of horizontal skeletal elements. This apparently represents morphological plasticity rather than differences that can be ascribed to distinct species. Conspecificity of the more extreme and dissimilar variants can be inferred from study of large assemblages of coeval specimens. The other species, with more narrowly defined, discrete variation fields, are more readily distinguished from each other.

Ludlow (Silurian) lithistid and hexactinellid sponges, Cape Phillips Formation, Canadian Arctic

1991 ◽  
Vol 28 (12) ◽  
pp. 2042-2061 ◽  
Author(s):  
Tim A. de Freitas
Keyword(s):  
Canadian Arctic ◽  
Evolutionary Trends ◽  
The Family ◽  
Cape Phillips Formation ◽  
Canal Systems ◽  
Structural Simplicity ◽  
Lithistid Sponge ◽  
Hexactinellid Sponges

Abundant hexactinellid and lithistid sponges occur in Ludlow (Silurian) platform slope strata of the Cape Phillips Formation, Canadian Arctic Islands. The following are new: in the Anthaspidellidae Miller, 1889, rhodesispongia simplex n.gen and sp., Climacospongia snowblindella n.sp., and Climacospongia undulata n.sp.; in the Sphaerocladina Schrammen, 1910, Caryospongia tuberosa n.sp.; in the Hexactinellida Schmidt, 1870 Malumispongium? cornwallisi n.sp., of the monospecific superfamily Malumispongium Rigby, 1967. Other previously described sponges recognized in the study assemblage include Hindia sphaeroidalis Duncan, 1879 and Caryospongia juglans Rauff, 1894. These occur in association with abundant Archaeoscyphia sp. in thin, laterally extensive lithistid sponge biostromes which throve on platform slope sediments during the Late Silurian. Based on the dominant dendroclone forms in the skeletons of these and other genera, Anthaspidellidae can be divided informally into two groups: (i) the polyclonids, possessing complex skeletons built of variable dendroclones types, including I-, X-, and Y-shape dendroclones, and accessory spicules, including rhizoclones, chiastoclones, and monactines; and (ii) the monoclonids, possessing simpler parenchymal canal systems and skeletons constructed mainly of I-shaped (amphiarborescent) dendroclones and lacking accessory spicules. The classification, based chiefly on skeletal architecture, suggests two main evolutionary trends in the family. The monoclonids generally maintained structural simplicity, inherited from the probable ancestral monactinellid, whereas the polyclonids evolved a varied and complex skeletal architecture that was more successful.

scholarly journals A Systematic Analysis of the Alpine Saxifrage Complex (Saxifragaceae) in the Canadian Arctic Islands Using Morphology and Chloroplast DNA Data

2004 ◽  
Vol 118 (3) ◽  
pp. 326 ◽  
Author(s):  
Caroline Healy ◽  
Lynn J. Gillespie
Keyword(s):  
Morphological Variability ◽  
Canadian Arctic ◽  
Principal Component ◽  
Distinct Species ◽  
Morphological Characters ◽  
Sympatric Species ◽  
Sensu Stricto ◽  
Morphological Data ◽  
Systematic Analysis ◽  
Site Analysis

The Saxifraga nivalis complex displays significant ecological, morphological and cytological variation. Most European studies suggest that the S. nivalis complex comprises two distinct species: Saxifraga nivalis sensu stricto and Saxifraga tenuis. However, the presence of intermediate morphotypes, inconsistencies in chromosomal counts and variability in morphological keys and descriptions have led to different taxonomic interpretations of the complex in North America. This study investigated the systematics of Canadian Arctic Island members of this complex from 157 specimens using 23 morphological characters. Principal component analysis of the morphological data revealed two adjacent clusters, corresponding to the two taxa and consistent with a close morphological similarity and the presence of hybrids. A preliminary restriction site analysis of five non-coding regions of the chloroplast genome, trnH-trnK, trnT-trnF, trnF-trnV, trnV-rbcL and rbcL-ORF106, was conducted using 21 restriction endonucleases. This analysis indicated a length difference between the trnT-trnF region of S. nivalis and that of S. tenuis, but no difference in restriction sites for any of the assayed regions. These results confirm that in the Canadian Arctic, the S. nivalis complex consists of two closely related, largely sympatric species, with notable morphological variability, and possible hybrids.

Heliolitine corals of the topmost Douro and overlying formations (Upper Silurian), Canadian Arctic islands

1998 ◽  
Vol 72 (6) ◽  
pp. 937-966 ◽  
Author(s):  
Owen A. Dixon
Keyword(s):  
New Species ◽  
Canadian Arctic ◽  
Unidentified Species ◽  
Upper Silurian ◽  
Somerset Island

Heliolitine corals occur in Upper Silurian strata of the topmost Douro, lower Barlow Inlet, and lower Somerset Island formations in the Boothia Uplift region. The fauna includesHeliolites(nine species),Propora(two species), the stelliporellid generaPodollites(three species) andStelliporella(one species), and the plasmoporidSquameolites(one species). Species present but not previously reported from the region includeHeliolites arcuatusBondarenko,Heliolites uksunayensisMironova,Stelliporella ilensisBondarenko,Podollites assitusnew species,Podollites parryinew species,Podollites plectilisnew species,Propora tubulata(Lonsdale) and an unidentified species ofPropora.All species occur in reef and reef-associated facies of open carbonate shelf and ramp settings. In restricted nonreefal carbonate shelf settings, diversity attenuates to a minimum, exemplified by numerically abundant monospecific assemblages ofHeliolites uksunayensis.Six of the 16 morphotaxonomic units recognized compare with species reported previously in Silurian faunas of Kazakhstan and Mongolia. Combinations of characters in the species attributed toPodollitessupport revision of the genus, possibly to includeDerivatolitesandTarbagatailites, in a group morphologically intermediate betweenStelliporellaandHeliolites.

Heliolitine corals of the upper Douro Formation (Upper Silurian), Canadian Arctic Islands

1996 ◽  
Vol 70 (5) ◽  
pp. 718-740 ◽  
Author(s):  
Owen A. Dixon
Keyword(s):  
New Species ◽  
Careful Study ◽  
Field Collection ◽  
Biometric Analysis ◽  
Equivalent Age ◽  
Unidentified Species ◽  
Septal Development ◽  
Reef Mounds ◽  
Somerset Island ◽  
Lithistid Sponge

Heliolitine corals are closely associated with lithistid sponge-dominated reef mounds in Ludlow carbonate ramp facies on Somerset Island. The corals occur abundantly in argillaceous, fossiliferous wackestone immediately flanking and capping the reef mounds, less commonly in calcilutite mudstone within the reef mounds, and with sharply decreasing abundance in nodular argillaceous wackestone to mudstone away from the reef mounds. Exhaustive field collection, and systematic study that included biometric analysis of collected assemblages, indicates that ten heliolitine species are present, including the new species Heliolites furyi, H. garnieri, and H. greineri, and two unidentified species, Heliolites sp. A, and Podollites? sp. The occurrence of H. subdecipiens Klaamann, 1984, H. tchernyshevi Bondarenko, 1966, H. cf. H. rariformis Tchi, 1976, Stelliporella cf. S. podolica Bondarenko, 1971, and Squameolites anomalus Tchi, 1976 indicates an affinity with Eurasian rather than North American faunas of equivalent age. Many new species have been ascribed to Stelliporella since the mid-1970s; most lack the diagnostic axial structures of the genus and are more appropriately regarded as belonging to Heliolites. Newly defined structures termed septal florets occur commonly in H. garnieri and very rarely in three other species of Heliolites. Effective taxonomic use of septal development requires very careful study because of the degree of intraspecific and intracolony variation in some species.

scholarly journals Skeletal variability of the coral Favia gravida (Verrill, 1868) from Brazil

2007 ◽  
Vol 7 (3) ◽  
pp. 245-251 ◽  
Author(s):  
Fernanda Duarte Amaral ◽  
Carla Alecrim Colaço Ramos
Keyword(s):  
Discriminant Analysis ◽  
Morphological Plasticity ◽  
Morphological Characters ◽  
Canonical Discriminant Analysis ◽  
The Other ◽  
Santa Cruz ◽  
Ecological Conditions ◽  
Terrigenous Sediments ◽  
Espirito Santo ◽  
Intercolony Variation

The skeletal variability of the coral Favia gravida, a species endemic to Brazil, was quantitatively described including populations from three locations: Tamandaré (state of Pernambuco), Abrolhos (state of Bahia), and Santa Cruz (state of Espírito Santo). Ten colonies were collected from each population and fourteen morphological characters were measured from ten corallites per colony. The results of univariate (among 14 skeletal characters, 7 showed p < 0.05) analysis provide evidence to suggest that F. gravida has considerable morphological plasticity, which may explain its ability to adapt to different ecological conditions. The species also displays polymorphism within and between colonies of each population. Intercolony variation within populations was relevant for most of the variables measured. Canonical discriminant analysis (r = 0.8648) showed that the population farthest offshore (Abrolhos) was distinct from the other two (Tamandaré and Santa Cruz), which have been affected by terrigenous sediments carried from the coast. Specimens from Santa Cruz displayed the highest degree of meandrinization.

scholarly journals Upper Ordovician – Upper Silurian conodont biostratigraphy, Devon Island and southern Ellesmere Island, Canadian Arctic Islands, with implications for regional stratigraphy, eustasy, and thermal maturation

2016 ◽  
Vol 53 (9) ◽  
pp. 931-949 ◽  
Author(s):  
Shunxin Zhang ◽  
Khusro Mirza ◽  
Christopher R. Barnes
Keyword(s):  
Canadian Arctic ◽  
Hydrocarbon Exploration ◽  
Upper Ordovician ◽  
Conodont Biostratigraphy ◽  
Thermal Maturation ◽  
Devon Island ◽  
The North ◽  
Cape Phillips Formation ◽  
Upper Silurian ◽  
Local Range

The conodont biostratigraphy for the Upper Ordovician – Upper Silurian carbonate shelf (Irene Bay and Allen Bay formations) and interfingering basinal (Cape Phillips Formation) facies is established for parts of Devon and Ellesmere islands, central Canadian Arctic Islands. Revisions to the interpreted regional stratigraphic relationships and correlations are based on the stratigraphic distribution of the 51 conodont species representing 32 genera, identified from over 5000 well-preserved conodonts recovered from 101 productive samples in nine stratigraphic sections. The six zones recognized are, in ascending order, Amorphognathus ordovicicus Local-Range Zone, Aspelundia fluegeli Interval Zone, Pterospathodus celloni Local-Range Zone, Pt. pennatus procerus Local-Range Zone, Kockelella patula Local-Range Zone, and K. variabilis variabilis – Ozarkodina confluens Concurrent-Range Zone. These provided a more precise dating of the members and formations and, in particular, the range of hiatuses within this stratigraphic succession. The pattern of regional stratigraphy, facies changes, and hiatuses is interpreted as primarily related to the effects of glacioeustasy associated with the terminal Ordovician glaciation and smaller Early Silurian glacial phases, the backstepping of the Silurian shelf margin, and the geodynamic effects of the collision with Laurentia by Baltica to the east and Pearya to the north. Conodont colour alteration index values (CAI 1–6.5) from the nine sections complement earlier graptolite reflectance data in providing regional thermal maturation data of value in hydrocarbon exploration assessments.

Atrypoidea species from the Canadian Arctic islands

1981 ◽  
Vol 18 (10) ◽  
pp. 1539-1561 ◽  
Author(s):  
Brian Jones
Keyword(s):  
New Species ◽  
Morphological Analysis ◽  
Canadian Arctic ◽  
Ellesmere Island ◽  
Evolutionary Trends ◽  
Arctic Canada ◽  
Separate Species ◽  
Devon Island ◽  
Upper Silurian ◽  
The Relationship

Species of Atrypoidea have the potential of being biostratigraphically useful for the Upper Silurian strata of Arctic Canada. Critical to any biostratigraphic scheme is the relationship between A. phoca (Salter, 1852) and A. scheii (Holtedahl, 1914) since there is disagreement as to whether these species are synonymous, or distinct and stratigraphically separate species. Detailed morphological analysis of topotype A. scheii from Goose Fiord, Ellesmere Island shows that it falls within the range of morphological variation displayed by topotype A. phoca from Cape Riley, Devon Island. Consequently, A. scheii is maintained as a synonym of A. phoca.Other new species that may prove to be biostratigraphically useful include Atrypoidea gigantus n.sp. from an unnamed formation at Goose Fiord and A. netserki n.sp. from member C of the Read Bay Formation on Beechey Island. Atrypoidea gigantus, the largest species of Atrypoidea so far reported from Arctic Canada, is closely related to Atrypoidea foxi (Jones, 1974). Atrypoidea netserki is morphologically closest to A. phoca.Although the Atrypoidea sequences in the Ludlovian and Pridolian strata of Arctic Canada are now better known it is still difficult to delineate exact evolutionary trends, possibly because the various species have a facies- as well as a time-controlled distribution.

Upper Silurian trilete spores and other microfossils from the Read Bay Formation, Cornwallis Island, Canadian Arctic

1978 ◽  
Vol 15 (8) ◽  
pp. 1292-1303 ◽  
Author(s):  
D. C. McGregor ◽  
G. M. Narbonne
Keyword(s):  
New Species ◽  
Marine Environment ◽  
Vascular Plants ◽  
Canadian Arctic ◽  
Type Section ◽  
Stratigraphic Framework ◽  
Near Shore ◽  
Upper Silurian ◽  
One New Species ◽  
Cornwallis Island

A diverse palynomorph assemblage of trilete spores, tetrads, acritarchs, chitinozoans, scolecodonts, and fragments of arthropods, ?hydrozoans, ?graptolites, and possibly nematophytalean and vascular plants occurs 20 m above the base of member B of the Read Bay Formation at the type section on eastern Cornwallis Island, District of Franklin. This assemblage, here described briefly, is late Ludlow according to faunas above and below. The palynomorphs, other fossils, and stratigraphic framework indicate that the shales of member B were deposited in a sheltered near-shore marine environment. One new species of trilete spores, Retusotriletes chartulatus McGregor, is erected.

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