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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 coleoid ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spirulid
Spirulida is an Order (biology), order of cephalopods comprising one extant taxon, extant species (''Spirula spirula'') and several extinction, extinct taxon, taxa. Fossil record * Oldest representative: Carboniferous, though contested: see ''Shimanskya'' * Oldest uncontested representative: Late Jurassic Classification Taxa marked with † are extinct. *Order Spirulida ***Family †Shimanskyidae **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 Spirula, Spirulidae References Tree of Life: Spirulida [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spirulida
Spirulida is an order of cephalopods comprising one extant species ('' Spirula spirula'') and several extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ... taxa. Fossil record * Oldest representative: Carboniferous, though contested: see '' Shimanskya'' * Oldest uncontested representative: Late Jurassic Classification Taxa marked with † are extinct. *Order Spirulida ***Family † Shimanskyidae **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 time scale, geologic period and System (stratigraphy), system of the Paleozoic era (geology), era that spans 60 million years, from the end of the Devonian Period Ma (million years ago) to the beginning of the Permian Period, Ma. It is the fifth and penultimate period of the Paleozoic era and the fifth period of the Phanerozoic eon (geology), eon. In North America, the Carboniferous is often treated as two separate geological periods, the earlier Mississippian (geology), Mississippian and the later Pennsylvanian (geology), Pennsylvanian. The name ''Carboniferous'' means "coal-bearing", from the Latin ("coal") and ("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 (geologist), William Conybeare and William Phillips (geologist), William Phillips in 1822, based on a study of the British rock succession. Carboniferous is the per ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Naefia
Groenlandibelidae is an extinct 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. ''Naefia'' Wetzel, 1930 The fossil range of ''Naefia'' is from Cenomanian The Cenomanian is, in the International Commission on Stratigraphy's (IC ... [...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 Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, ....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 Spirulida {{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. 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 evidence. They generalized this observation to assert that the rate of evolutionary change of any specified protein was approximately constant over time and over different lineages (known as the molecular clock hypothesis). The genetic equidistance phenomenon was first noted in 1963 by Emanuel Margoliash, who wrote: "It appears that the number ... [...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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cephalopod Genera
A cephalopod is any member of the molluscan class Cephalopoda (Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles (muscular hydrostats) modified from the primitive molluscan foot. Fishers sometimes call cephalopods "inkfish", referring to their common ability to squirt ink. The study of cephalopods is a branch of malacology known as teuthology. Cephalopods became dominant during the Ordovician period, represented by primitive nautiloids. The class now contains two, only distantly related, extant subclasses: Coleoidea, which includes octopuses, squid, and cuttlefish; and Nautiloidea, represented by ''Nautilus'' and ''Allonautilus''. In the Coleoidea, the molluscan shell has been internalized or is absent, whereas in the Nautiloidea, the external shell remains. About 800 living species of cephalopods have been identified. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carboniferous Cephalopods
The Carboniferous ( ) is a Geologic time scale, geologic period and System (stratigraphy), system of the Paleozoic era (geology), era that spans 60 million years, from the end of the Devonian Period Ma (million years ago) to the beginning of the Permian Period, Ma. It is the fifth and penultimate period of the Paleozoic era and the fifth period of the Phanerozoic eon (geology), eon. In North America, the Carboniferous is often treated as two separate geological periods, the earlier Mississippian (geology), Mississippian and the later Pennsylvanian (geology), Pennsylvanian. The name ''Carboniferous'' means "coal-bearing", from the Latin ("coal") and ("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 (geologist), William Conybeare and William Phillips (geologist), William Phillips in 1822, based on a study of the British rock succession. Carboniferous is the per ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
