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Stenothecidae
Stenothecidae is an extinct family of fossil univalved Cambrian molluscs which may be either gastropods or monoplacophorans. The name of this taxon should not be confused with that of the class Stenothecoida, a group of problematic Cambrian invertebrates that have a bivalved (dorsal and ventral) shell. Morphology The group comprises conical laterally compressed shells that may be smooth or ornamented with folds or ribs. The shells are broadly limpet-like, which led to their initial consideration as monoplacophoran molluscs. Taxonomy The taxonomic position of the group is unclear; it has been classified as a Yochelcionelloid or Helcionelloid. It is not obviously in the stem group of any modern molluscan class, and has been referred to the monoplacophora, although the monoplacophora are no longer considered to be a clade, and thus that classification means little more than "primitive mollusc". Genera The family Stenothecidae consists of two subfamilies and the fol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Yochelcionelloid
Yochelcionelloidea is an extinct superfamily of paleozoic molluscs of uncertain position (Gastropoda or Monoplacophora). The earliest yochelcionellids are known from the Middle Tommotian, but they are most diverse from the Botomian through the early Middle Cambrian.Pavel Yu. Parkhaev (2008). "The Early Cambrian Radiation of Mollusca.'" In: "''Phylogeny and evolution of the Mollusca.''" Edited by: Ponder WF, Lindberg DR. Berkeley: University of California Press: 33-69. 2005 taxonomy The taxonomy of the Gastropoda by Bouchet & Rocroi, 2005: Yochelcionelloidea * † Yochelcionellidae * † Stenothecidae * † Trenellidae 2006-2007 taxonomy According to the opinion of P. Yu. Parkhaev is in the class Helcionelloida, subclass Archaeobranchia Parkhaev, 2001, Order Helcionelliformes Golikov & Starobogatov, 1975:P. Yu. Parkhaev (2007) ''"The Cambrian ‘basement’ of gastropod evolution"''. In: Vickers-Rich, P. & Komarower, P. (eds.) ''"The Rise and Fall of the Ediacaran Biota"'', ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Yochelcionelloidea
Yochelcionelloidea is an extinct superfamily of paleozoic molluscs of uncertain position ( Gastropoda or Monoplacophora). The earliest yochelcionellids are known from the Middle Tommotian, but they are most diverse from the Botomian through the early Middle Cambrian.Pavel Yu. Parkhaev (2008). "The Early Cambrian Radiation of Mollusca.'" In: "''Phylogeny and evolution of the Mollusca.''" Edited by: Ponder WF, Lindberg DR. Berkeley: University of California Press: 33-69. 2005 taxonomy The taxonomy of the Gastropoda by Bouchet & Rocroi, 2005: Yochelcionelloidea * † Yochelcionellidae * † Stenothecidae * † Trenellidae 2006-2007 taxonomy According to the opinion of P. Yu. Parkhaev is in the class Helcionelloida, subclass Archaeobranchia Parkhaev, 2001, Order Helcionelliformes Golikov & Starobogatov, 1975:P. Yu. Parkhaev (2007) ''"The Cambrian ‘basement’ of gastropod evolution"''. In: Vickers-Rich, P. & Komarower, P. (eds.) ''"The Rise and Fall of the Ediacaran Biota"' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Helcionelloid
Helcionellid or Helcionelliformes is an order of small fossil shells that are universally interpreted as molluscs, though no sources spell out why this taxonomic interpretation is preferred. These animals are first found about in the late Nemakit-Daldynian age, which is the earliest part of the Cambrian period. A single species persisted to the Early Ordovician. These fossils are component of the small shelly fossils (SSF) assemblages. These are thought to be early molluscs with rather snail-like shells, although they lack any compelling molluscan synapomorphies and thus may not belong to the group. They have been alleged to represent ancestors of the modern conchiferans, a group that includes all the well-known modern classes – gastropods, cephalopods and bivalves. They have also been considered to represent direct ancestors to the cephalopods. Parkhaev (2006, 2007) considers these animals to be crown-group gastropods. Previous to the 2006 classification by Parkhaev, helci ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stenothecoida
Stenothecoida is a taxon of bivalved fossils from the Early to middle Cambrian period. They look a bit like brachiopods or bivalve molluscs. Affinity Their affinity is uncertain. They were considered by E. L. Yochelson 1968 to belong to Mollusca, whereas Runnegar and Pojeta (1974) suggested that they might be 'bivalved monoplacophorans'. This said, the morphology of the shell does not resemble the shell of any other class of molluscs; they also look a little like brachiopods It's not clear whether their two valves are each other's mirror images, as in bivalve molluscs, though they aren't identical to one another It's more likely that the valves each have a single plane of symmetry (as in brachiopods), suggesting a brachiopod affiliation. As with many other Cambrian taxa, it has been suggested that they arise through reduction of a ''Halkieria''-like ancestor. Mineralogy Thought to be low-Mg calcite.Kouchinsky, A. V. et al. Chronology of early Cambrian biomineralization. Ge ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amadeus William Grabau
Amadeus William Grabau (January 9, 1870 – March 20, 1946) was an American geologist who worked in China. Biography Grabau's grandfather, J.A.A. Grabau, led a group of dissident Lutheran immigrants from Germany to Buffalo, New York. His education began in his father's parochial school in his birthplace of Cedarburg, Wisconsin, and then the public high school there. After his father became head of the Martin Luther Seminary in 1885, he finished high school in Buffalo. He took classes in the evenings while apprenticed to a bookbinder. His interest in local fossils grew. In a correspondence course in mineralogy, he impressed geologist William Otis Crosby enough to hire him at the Boston Society of Natural History in 1890, and arrange his education at Boston Latin, MIT, and Harvard. He taught at MIT and Rensselaer Polytechnic Institute early in his career. In 1901 he became a professor at Columbia University in New York. He married Barnard student Mary Antin on October 5, 1901. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Watsonella (gastropod)
''Watsonella'' is a genus of 'mollusc' known from early (Terreneuvian) Cambrian strata. The genus is closely related to ''Anabarella'', with which it bears many morphological similarities, including a laminar internal shell microstructure said to connect it with the early bivalves ''Fordilla'' and ''Pojetaia''. Biostratigraphic significance Watsonella has been proposed as an index fossil of the Cambrian, defining a W. crosbyi zone. Notwithstanding the weakness of a first appearance datum as a definition for the base of a period, the species has been proposed as a marker for the base of the presently unratified second stage of the Terreneuvian (i.e. Cambrian Stage 2). However, the species has now been found late in the FOrtunian, drawing back its first occurrence. But that said its occurrence in Australia seems to begin rather near the base of Stage 2. Affinity Widely thought to be a mollusc, the connection between the two 'valves' of Watsonella recalls the configuration of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Type Genus
In biological taxonomy, the type genus is the genus which defines a biological family and the root of the family name. Zoological nomenclature According to the International Code of Zoological Nomenclature, "The name-bearing type of a nominal family-group taxon is a nominal genus called the 'type genus'; the family-group name is based upon that of the type genus." Any family-group name must have a type genus (and any genus-group name must have a type species, but any species-group name may, but need not, have one or more type specimens). The type genus for a family-group name is also the genus that provided the stem to which was added the ending -idae (for families). :Example: The family name Formicidae has as its type genus the genus ''Formica'' Linnaeus, 1758. Botanical nomenclature In botanical nomenclature, the phrase "type genus" is used, unofficially, as a term of convenience. In the '' ICN'' this phrase has no status. The code uses type specimens for ranks up to fam ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Russian Academy Of Sciences
The Russian Academy of Sciences (RAS; russian: Росси́йская акаде́мия нау́к (РАН) ''Rossíyskaya akadémiya naúk'') consists of the national academy of Russia; a network of scientific research institutes from across the Russian Federation; and additional scientific and social units such as libraries, publishing units, and hospitals. Peter the Great established the Academy (then the St. Petersburg Academy of Sciences) in 1724 with guidance from Gottfried Leibniz. From its establishment, the Academy benefitted from a slate of foreign scholars as professors; the Academy then gained its first clear set of goals from the 1747 Charter. The Academy functioned as a university and research center throughout the mid-18th century until the university was dissolved, leaving research as the main pillar of the institution. The rest of the 18th century continuing on through the 19th century consisted of many published academic works from Academy scholars and a few Ac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
