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Search Results: 1 - 10 of 233195 matches for " Emig Christian C. "
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Tools for linguloid taxonomy: the genus Obolus (Brachiopoda) as an example
Emig Christian C.
Carnets de Géologie , 2002,
Abstract: This study points out some basic problems of linguloid systematics and proposes solutions for them. A taxonomic examination of the unique species of the genus Obolus found in the Upper Cambrian of Estonia and Russia, O. apollinis (= O. ruchini, O. transversus, O. rebrovi and Ungula convexa) is used as an example of a methodology employing all of the characters valid for distinguishing species of both extant and fossil Lingulidae. These characters are: - umbonal region; - body musculature; - septa or ridges; - main mantle canals - as established and figured by Emig (1982, 1983) and Biernat and Emig (1993). All of them have been determined to be taxonomically stable and have been studied and compared to take into account intraspecific variability; they should be used to describe or to redescribe any taxon of the superfamily Linguloidea. Characters of the shell and valves, such as shape, size, and dimensional ratios have no taxonomic value.
Fossil Phoronida and related ichnotaxa
Emig Christian C.
Carnets de Géologie , 2010,
Abstract: Various ichnotaxa found in hard substrates are interpreted as "phoronid" trace fossils. Their records are briefly reviewed. An interpretation of Diorygma found in the shells of brachiopods is not compatible with phoronid morphology and anatomy. Criteria for the discrimination of phoronid burrows and borings from those of similar organisms from others are difficult to establish even when the evidence and conclusions made therefrom are sound.
Schmidtites celatus (Obolida, Brachiopoda) from the "Obolus sands" (Upper Cambrian - Lower Ordovician) of Estonia
Emig Christian C.
Carnets de Géologie , 2006,
Abstract: Large collections of the brachiopod obolid Schmidtites celatus have been gathered from Upper Cambrian-Lower Ordovician strata in four northern Estonian localities. The morphological features and the taxonomic characters of the genus and of the single species representing it are re-described and illustrated. New diagnoses are proposed based on characters of the shell and morphological traits that permit Schmidtites celatus to be compared with and distinguished from the other obolid genera occurring in the same samples or areas, i.e. Ungula ingrica, Oepikites, and Obolus apollinis which now includes specimens formerly described as Ungula convexa. Schmidtites celatus differs from them mainly in the arrangement of its musculature.
On the history of the names Lingula, anatina, and on the confusion of the forms assigned them among the Brachiopoda
Emig Christian C.
Carnets de Géologie , 2008,
Abstract: The first descriptions of Lingula were made from then extant specimens by three famous French scientists: Bruguière, Cuvier, and Lamarck. The genus Lingula was created in 1791 (not 1797) by Bruguière and in 1801 Lamarck named the first species L. anatina, which was then studied by Cuvier (1802). In 1812 the first fossil lingulids were discovered in the Mesozoic and Palaeozoic strata of the U.K. and were referred to Lingula on the basis of similarity in the form of the shell. In the 1840's other linguliform brachiopods from the Palaeozoic were described. The similarity of the shell form of the extant Lingula and these fossils led Darwin in 1859 to create the description "living fossil" in his book "On the Origin of Species". Thereafter, this Darwinian concept became traditional in that Lingula was considered to lack morphological evolutionary changes. Although denounced as scientifically incorrect for more than two decades, the concept still remains in many books, publications and Web sites, perhaps a witness to palaeontological conservatism.
Proof that Lingula (Brachiopoda) is not a living-fossil, and emended diagnoses of the Family Lingulidae
Emig Christian C.
Carnets de Géologie , 2003,
Abstract: Lingula is often considered a "living-fossil" based on its supposed lengthy morphological conservatism owing to its absence of evolution, and its remarkable survival for more than 550 M.Y. This conclusion is based on the typical apparently unchanged "linguliform" shape of the shell. However the taxa of the family Lingulidae show morphological evolutionary changes despite the fact that the group appears panchronic among the Recent Brachiopoda. Consequently, traditional opinion that Lingula is a "living-fossil" should be rejected. Diagnoses of the Family Lingulidae and of its three genera are herewith emended.
Reply to L.E. Popov and L.E. Holmer (CG2003_A06_LEP-LEH): Obolid taxonomy
Emig Christian C.
Carnets de Géologie , 2003,
Abstract: Since early in the 19th Century the taxonomy of fossil obolids has been the subject of numerous controversies (Table 1), so the development of new criteria for their proper differentiation is mandatory. Based on the extant species of the family Lingulidae (Emig, 1982, 1983) and later applied to fossil taxa (Biernat and Emig, 1993), new morpho-anatomical characters were established and their variability analysed. As a consequence, several shell structures commonly used to discriminate between genera and species of both extant and fossil taxa were determined to have no phylogenetic status.
Nummulus brattenburgensis and Crania craniolaris (Brachiopoda, Craniidae)
Emig Christian C.
Carnets de Géologie , 2009,
Abstract: The Brattingsborg pennies are mentioned in medieval texts dating from the middle of the first millennium and many popular medieval legends refer to their occurrence on Iv Island in the Scania region (Sweden) as brattingsborgpenningar or in Latin as Nummulus brattenburgensis. Actually they are valves of the fossil brachiopod Crania craniolaris originally described by Linnaeus (1758) as Anomia craniolaris from the Upper Cretaceous. Later Retzius (1781) created the genus Crania based on these specimens from Iv Island and on another species he described under Crania (now Isocrania) egnabergensis from Ignaberga in the Scania region. The scientific history of those two species is reviewed along with that of Danocrania tuberculata (Nilsson, 1826), formerly figured as Craniolites brattenburgicus, from the Danian of Scania. Two legends about these "pennies" are included.
The Mediterranean deep-sea fauna: historical evolution, bathymetric variations and geographical changes
Emig Christian C.,Geistdoerfer Patrick
Carnets de Géologie , 2004,
Abstract: The deep-water fauna of the Mediterranean is characterized by an absence of distinctive characteristics and by a relative impoverishment. Both are a result of events after the Messinian salinity crisis (Late Miocene). The three main classes of phenomena involved in producing or recording these effects are analysed and discussed: - Historical: Sequential faunal changes during the Pliocene and thereafter in particular those during the Quaternary glaciations and still in progress. - Bathymetric: Changes in the vertical aspects of the Bathyal and Abyssal zones that took place under peculiar conditions, i.e. homothermy, a relative oligotrophy, the barrier of the Gibraltar sill, and water mass movement. The deeper the habitat of a species in the Mediterranean, the more extensive is its distribution elsewhere. - Geographical: There are strong affinities and relationships between Mediterranean and Atlantic faunas. Endemic species remain a biogeographical problem. Species always become smaller in size eastward where they occupy a progressively deeper habitat. Thus, the existing deep Mediterranean Sea appears to be younger than any other deep-sea constituent of the World Ocean.
Faune profonde en Mer Méditerranée : les échanges historiques, géographiques et bathymétriques
Emig Christian C.,Geistdoerfer Patrick
Carnets de Géologie , 2004,
Abstract: Le benthos profond méditerranéen est caractérisé par une absence d'originalité et une pauvreté dont les raisons sont à rechercher dans l'histoire récente de la faune. Trois types principaux d‘échanges ont été distingués : - les échanges historiques à travers les changements de faunes depuis le Pliocène et durant les glaciations du Quaternaire ; - les échanges bathymétriques au sein des étages Bathyal et Abyssal soumis à des conditions très particulières (homothermie, relative oligotrophie, barrière du seuil de Gibraltar, circulation des masses d'eaux) ; plus profonde est l’extension des espèces en Mer Méditerranée et plus large est leur distribution hors Méditerranée ; - les échanges géographiques avec des affinités étroites entre Mer Méditerranée et Océan Atlantique. Le cas des espèces endémiques reste un problème biogéographique. Les espèces ont toujours une distribution plus profonde en allant vers l'Est et leur taille devient plus petite. Ainsi, la Mer Méditerranée profonde actuelle appara t comme une mer beaucoup plus jeune qu'aucune autre partie de l'Océan mondial profond.
The Mediterranean deep-sea fauna: historical evolution, bathymetric variations and geographical changes
Christian Emig,Patrick Geistdoerfer
Quantitative Biology , 2005,
Abstract: The deep-water fauna of the Mediterranean is characterized by an absence of distinctive characteristics and by a relative impoverishment. Both are a result of events after the Messinian salinity crisis (Late Miocene). The three main classes of phenomena involved in producing or recording these effects are analysed and discussed: - Historical: Sequential faunal changes during the Pliocene and thereafter in particular those during the Quaternary glaciations and still in progress. - Bathymetric: Changes in the vertical aspects of the Bathyal and Abyssal zones that took place under peculiar conditions, i.e. homothermy, a relative oligotrophy, the barrier of the Gibraltar sill, and water mass movement. The deeper the habitat of a species in the Mediterranean, the more extensive is its distribution elsewhere. - Geographical: There are strong affinities and relationships between Mediterranean and Atlantic faunas. Endemic species remain a biogeographical problem. Species always become smaller in size eastward where they occupy a progressively deeper habitat. Thus, the existing deep Mediterranean Sea appears to be younger than any other deep-sea constituent of the World Ocean.
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