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Shimanskya
''Shimanskya'' is a late Carboniferous fossil tentatively interpreted as an early spirulid. This identification was based on: Doguzhaeva ''et al.'' also identify these features in living Spirula, and the fossil 'Spirulida' Naefia, '' Groenlandibelus'' and '' Adygeya''—though see these respective articles for discussion as to whether or not these extinct genera are themselves Spiruliids. Some authors are happy to accept this designation. But others have argued that none of the characters observed in ''Shimanskya'' is clearly diagnostic of the Spirulids. For example, a nacreous layer may have been lost more than once in cephalopod evolution. Others view the microstructural evidence as ambiguous. Interpreting ''Shimanskya'' as a spirulid creates a large gap in the fossil record of the lineage. Moreover, some molecular clock results predict that spirulids evolved much later than the Carboniferous, leading some to suggest that ''Shimanskya'' ought to be assigned to the col ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spirulid
Spirulida is an order of cephalopods comprising one extant species (''Spirula spirula'') and several extinct taxa. Fossil record * Oldest representative: Carboniferous, though contested: see ''Shimanskya'' * Oldest uncontested representative: Late Jurassic Classification *Order Spirulida **?Family †Shimanskyidae ''Shimanskya'' is a late Carboniferous fossil tentatively interpreted as an early spirulid. This identification was based on: Doguzhaeva ''et al.'' also identify these features in living Spirula, and the fossil 'Spirulida' Naefia, '' Groenl ... **Suborder †Groenlandibelina Khromov, 1990 ***Family † Groenlandibelidae ***Family † Adygeyidae **Suborder †Belopterina Engeser, 1998 ***Family † Belemnoseidae ***Family † Belopteridae **Suborder Spirulina Pompeckj, 1912 ***Family † Spirulirostridae ***Family † Spirulirostrinidae ***Family Spirulidae References Tree of Life: Spirulida [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carboniferous
The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carboniferous'' means "coal-bearing", from the Latin '' carbō'' ("coal") and '' ferō'' ("bear, carry"), and refers to the many coal beds formed globally during that time. The first of the modern 'system' names, it was coined by geologists William Conybeare and William Phillips in 1822, based on a study of the British rock succession. The Carboniferous is often treated in North America as two geological periods, the earlier Mississippian and the later Pennsylvanian. Terrestrial animal life was well established by the Carboniferous Period. Tetrapods (four limbed vertebrates), which had originated from lobe-finned fish during the preceding Devonian, became pentadactylous in and diversified during the Carboniferous, including early amphibian lin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Naefia
Groenlandibelidae is a family of coleoid cephalopods believed to belong to the spirulids. Morphologically, its taxa seem to have some belemnoid characteristics, suggesting a possible intermediate relationship. Genera ''Groenlandibelus '' Jeletzky, 1966 Monospecific, ''Groenlandibelus rosenkrantzi'' Jeletzky, 1966 (Birkelund, 1956). The fossil range is from Campanian to Maastrichtian Some material originally was ascribed to ''Belemnoteuthis'' before being allocated its own genus. ''Cyrtobelus'' Fuchs et al 2012 Some taxa now assigned to the ''Groenlandibelus'' are now assigned to ''Cyrtobelus''. Species: * ''Cyrtobelus birkelundae'' Fuchs et al. 2012 * ''C. hornbyense'' Fuchs et al. 2012 The fossil range is from Upper Campanian to upper Maastrichtian with localities in Vancouver Island (BC) and West Greenland Kitaa, originally Vestgrønland ("West Greenland"), is a former administrative division of Greenland. It was by far the most populated of the divisions, bein ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Groenlandibelus
Groenlandibelidae is a family of coleoid cephalopods believed to belong to the spirulids. Morphologically, its taxa seem to have some belemnoid characteristics, suggesting a possible intermediate relationship. Genera ''Groenlandibelus '' Jeletzky, 1966 Monospecific, ''Groenlandibelus rosenkrantzi'' Jeletzky, 1966 (Birkelund, 1956). The fossil range is from Campanian to Maastrichtian Some material originally was ascribed to ''Belemnoteuthis'' before being allocated its own genus. ''Cyrtobelus'' Fuchs et al 2012 Some taxa now assigned to the ''Groenlandibelus'' are now assigned to ''Cyrtobelus''. Species: * ''Cyrtobelus birkelundae'' Fuchs et al. 2012 * ''C. hornbyense'' Fuchs et al. 2012 The fossil range is from Upper Campanian to upper Maastrichtian with localities in Vancouver Island (BC) and West Greenland Kitaa, originally Vestgrønland ("West Greenland"), is a former administrative division of Greenland. It was by far the most populated of the divisions, being ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adygeya
''Adygeya'' is a genus of cephalopods assigned to the Spirulida Spirulida is an order of cephalopods comprising one extant species ('' Spirula spirula'') and several extinct taxa. Fossil record * Oldest representative: Carboniferous, though contested: see '' Shimanskya'' * Oldest uncontested representativ ....Doguzhaeva, L. A., Mapes, R. H., & Mutvei, H. (1999). A Late Carboniferous spirulid coleoid from the southern mid-continent (USA): shell wall ultrastructure and evolutionary implications. In F. Olóriz & F. J. Rodríguez-Tovar (Eds.), Advancing Research on Living and Fossil Cephalopods (pp. 47–57). New York: Kluwer Academic Publishers. References Coleoidea {{paleo-cephalopod-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molecular Clock
The molecular clock is a figurative term for a technique that uses the mutation rate of biomolecules to deduce the time in prehistory when two or more life forms diverged. The biomolecular data used for such calculations are usually nucleotide sequences for DNA, RNA, or amino acid sequences for proteins. The benchmarks for determining the mutation rate are often fossil or archaeological dates. The molecular clock was first tested in 1962 on the hemoglobin protein variants of various animals, and is commonly used in molecular evolution to estimate times of speciation or radiation. It is sometimes called a gene clock or an evolutionary clock. Early discovery and genetic equidistance The notion of the existence of a so-called "molecular clock" was first attributed to Émile Zuckerkandl and Linus Pauling who, in 1962, noticed that the number of amino acid differences in hemoglobin between different lineages changes roughly linearly with time, as estimated from fossil evi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stem Group
In phylogenetics, the crown group or crown assemblage is a collection of species composed of the living representatives of the collection, the most recent common ancestor of the collection, and all descendants of the most recent common ancestor. It is thus a way of defining a clade, a group consisting of a species and all its extant or extinct descendants. For example, Neornithes (birds) can be defined as a crown group, which includes the most recent common ancestor of all modern birds, and all of its extant or extinct descendants. The concept was developed by Willi Hennig, the formulator of phylogenetic systematics, as a way of classifying living organisms relative to their extinct relatives in his "Die Stammesgeschichte der Insekten", and the "crown" and "stem" group terminology was coined by R. P. S. Jefferies in 1979. Though formulated in the 1970s, the term was not commonly used until its reintroduction in 2000 by Graham Budd and Sören Jensen. Contents of the crown gr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coleoidea
Subclass Coleoidea, or Dibranchiata, is the grouping of cephalopods containing all the various taxa popularly thought of as "soft-bodied" or "shell-less" (i.e., octopuses, squid and cuttlefish). Unlike its extant sister group, Nautiloidea, whose members have a rigid outer shell for protection, the coleoids have at most an internal cuttlebone, gladius, or shell that is used for buoyancy or support. Some species have lost their cuttlebone altogether, while in some it has been replaced by a chitinous support structure. A unique trait of the group is the ability to edit their own RNA. The major divisions of Coleoidea are based upon the number of arms or tentacles and their structure. The extinct and most primitive form, the Belemnoidea, presumably had ten equally-sized arms in five pairs numbered dorsal to ventral as I, II, III, IV and V. More modern species either modified or lost a pair of arms. The superorder Decapodiformes has arm pair IV modified into long tentacles wit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
