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Haplophrentis
''Haplophrentis'' is a genus of tiny shelled hyolithid which lived in the Cambrian Period. Its shell was long and conical, with the open end protected by an operculum, from which two fleshy arms called ''helens'' protruded at the sides. These arms served to elevate the opening of the shells above the sea floor, acting like stilts. Morphology Shell length of ''H. reesi'' reached up to while ''H. carinatus'' reached up to . Juveniles could of course be smaller. It is distinguished from ''Hyolithes'' by the presence of a longitudinal septum on the middle of the inner surface of the top of the shell. Its soft anatomy comprises 12(H. carinatus) to 16 (H. reesi) tentacles attached to a horseshoe-shaped lophophore. A pair of wide structures of uncertain function extend along the length of the conical shell. A larval shell is attached to the shell apex. Affinity The soft anatomy of ''Haplophrentis'' was key to establishing the hyoliths as members of the Lophophorata, the group ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Haplophrentis Burgess Shale
''Haplophrentis'' is a genus of tiny shelled hyolithid which lived in the Cambrian Period. Its shell was long and conical, with the open end protected by an operculum, from which two fleshy arms called ''helens'' protruded at the sides. These arms served to elevate the opening of the shells above the sea floor, acting like stilts. Morphology Shell length of ''H. reesi'' reached up to while ''H. carinatus'' reached up to . Juveniles could of course be smaller. It is distinguished from ''Hyolithes'' by the presence of a longitudinal septum on the middle of the inner surface of the top of the shell. Its soft anatomy comprises 12(H. carinatus) to 16 (H. reesi) tentacles attached to a horseshoe-shaped lophophore. A pair of wide structures of uncertain function extend along the length of the conical shell. A larval shell is attached to the shell apex. Affinity The soft anatomy of ''Haplophrentis'' was key to establishing the hyoliths as members of the Lophophorata, the group c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hyolithid
Hyoliths are animals with small conical shells, known as fossils from the Palaeozoic era. They are at least considered as lophotrochozoan, and possibly being lophophorates, a group which includes the brachiopods, while others consider them as being basal lophotrochozoans, or even molluscs. Morphology The shell of a hyolith is typically one to four centimeters in length, triangular or elliptical in cross section. Some species have rings or stripes. It comprises two parts: the main conical shell (previously referred to as a ‘conch’) and a cap-like operculum. Some also had two curved supports known as ''helens'' They are calcareous – probably aragonitic All of these structures grew by marginal accretion. Shell microstructure The orthothecid shell has an internal layer with a microstructure of transverse bundles, and an external layer comprising longitudinal bundles. Helens Some hyoliths had helens, long structures that taper as they coil gently in a logarithmic spira ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hyolithes
Hyoliths are animals with small conical shells, known as fossils from the Palaeozoic era. They are at least considered as lophotrochozoan, and possibly being lophophorates, a group which includes the brachiopods, while others consider them as being basal lophotrochozoans, or even molluscs. Morphology The shell of a hyolith is typically one to four centimeters in length, triangular or elliptical in cross section. Some species have rings or stripes. It comprises two parts: the main conical shell (previously referred to as a ‘conch’) and a cap-like operculum. Some also had two curved supports known as ''helens'' They are calcareous – probably aragonitic All of these structures grew by marginal accretion. Shell microstructure The orthothecid shell has an internal layer with a microstructure of transverse bundles, and an external layer comprising longitudinal bundles. Helens Some hyoliths had helens, long structures that taper as they coil gently in a logarithmic spira ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hyolitha
Hyoliths are animals with small conical shells, known as fossils from the Palaeozoic era. They are at least considered as lophotrochozoan, and possibly being lophophorates, a group which includes the brachiopods, while others consider them as being basal lophotrochozoans, or even molluscs. Morphology The shell of a hyolith is typically one to four centimeters in length, triangular or elliptical in cross section. Some species have rings or stripes. It comprises two parts: the main conical shell (previously referred to as a ‘conch’) and a cap-like operculum. Some also had two curved supports known as ''helens'' They are calcareous – probably aragonitic All of these structures grew by marginal accretion. Shell microstructure The orthothecid shell has an internal layer with a microstructure of transverse bundles, and an external layer comprising longitudinal bundles. Helens Some hyoliths had helens, long structures that taper as they coil gently in a logarithmic spira ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ottoia
''Ottoia'' is a stem-group archaeopriapulid worm known from Cambrian fossils. Although priapulid-like worms from various Cambrian deposits are often referred to ''Ottoia'' on spurious grounds, the only clear ''Ottoia'' macrofossils come from the Burgess Shale of British Columbia, which was deposited . Microfossils extend the record of ''Ottoia'' throughout the Western Canada Sedimentary Basin, from the mid- to late- Cambrian. A few fossil finds are also known from China. Morphology ''Ottoia'' specimens are on average 8 centimeters in length. Both length and width show variation with contraction; shorter specimens often being wider than longer ones. The characteristic proboscis of priapulids is present at the anterior, attached to the trunk of the animal, proceeded by the "bursa" at the posterior. The organism's body is bilaterally symmetrical, however, its anterior displays external radial symmetry. Like some other modern invertebrates, a cuticle restricts the size of and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cambrian
The Cambrian Period ( ; sometimes symbolized C with bar, Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million years ago (mya) to the beginning of the Ordovician Period mya. Its subdivisions, and its base, are somewhat in flux. The period was established as "Cambrian series" by Adam Sedgwick, who named it after Cambria, the Latin name for 'Cymru' (Wales), where Britain's Cambrian rocks are best exposed. Sedgwick identified the layer as part of his task, along with Roderick Murchison, to subdivide the large "Transition Series", although the two geologists disagreed for a while on the appropriate categorization. The Cambrian is unique in its unusually high proportion of sedimentary deposits, sites of exceptional preservation where "soft" parts of organisms are preserved as well as their more resistant shells. As a result, our understanding of the Ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Operculum (gastropod)
The operculum (; ) is a corneous or calcareous anatomical structure like a trapdoor that exists in many (but not all) groups of sea snails and freshwater snails, and also in a few groups of land snails; the structure is found in some marine and freshwater gastropods, and in a minority of terrestrial gastropods, including the families Helicinidae, Cyclophoridae, Aciculidae, Maizaniidae, Pomatiidae, etc. The operculum is attached to the upper surface of the foot and in its most complete state, it serves as a sort of "trapdoor" to close the aperture of the shell when the soft parts of the animal are retracted. The shape of the operculum varies greatly from one family of gastropods to another. It is fairly often circular, or more or less oval in shape. In species where the operculum fits snugly, its outline corresponds exactly to the shape of the aperture of the shell and it serves to seal the entrance of the shell. Many families have opercula that are reduced in size, and which a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lophophorata
The Lophophorata are a Lophotrochozoan clade consisting of the Brachiozoa and the Bryozoa. They have a lophophore. Molecular phylogenetic analyses suggest that lophophorates are protostomes, but on morphological grounds they have been assessed as deuterostomes. Fossil finds of a segmented worm named Wufengella ''Wufengella'' is a genus of extinct camenellan " tommotiid" that lived during the Early Cambrian ( Stage 3). Described in 2022, the only species ''Wufengella bengtsonii'' was discovered from the Maotianshan Shales of Chiungchussu (Qiongzhusi) F ... suggest that they evolved from a worm close to annelids. References {{Protostome-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lophotrochozoa
Lophotrochozoa (, "crest/wheel animals") is a clade of protostome animals within the Spiralia. The taxon was established as a monophyletic group based on molecular evidence. The clade includes animals like annelids, molluscs, bryozoans, brachiopods, and platyhelminthes. Groups Lophotrochozoa was defined in 1995 as the "last common ancestor of the three traditional lophophorate taxa (brachiopods, bryozoans, and phoronid worms), the mollusks and the annelids, and all of the descendants of that common ancestor". It is a cladistic definition (a node-based name), so the affiliation to Lophotrochozoa of spiralian groups not mentioned directly in the definition depends on the topology of the spiralian tree of life, and in some phylogenetic hypotheses, Lophotrochozoa may even be synonymous to Spiralia. Nemertea and Orthonectida (if not directly considered as part of Annelida) are probably lophotrochozoan phyla; Dicyemida, Gastrotricha, and Platyhelminthes may be lophotrochozoans ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mollusca
Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is estimated between 60,000 and 100,000 additional species. The proportion of undescribed species is very high. Many taxa remain poorly studied. Molluscs are the largest marine phylum, comprising about 23% of all the named marine organisms. Numerous molluscs also live in freshwater and terrestrial habitats. They are highly diverse, not just in size and anatomical structure, but also in behaviour and habitat. The phylum is typically divided into 7 or 8 taxonomic classes, of which two are entirely extinct. Cephalopod molluscs, such as squid, cuttlefish, and octopuses, are among the most neurologically advanced of all invertebrates—and either the giant squid or the colossal squid is the largest known invertebrate species. The gastropod ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phyllopod Bed
The Phyllopod bed, designated by USNM locality number 35k, is the most famous fossil-bearing member of the Burgess Shale fossil ''Lagerstätte''. It was quarried by Charles Walcott from 1911–1917 (and later named Walcott Quarry), and was the source of 95% of the fossils he collected during this time; tens of thousands of soft-bodied fossils representing over 150 genera have been recovered from the Phyllopod bed alone. Stratigraphy and location The phyllopod bed is a 2.31 m thick layer of the 7 m thick Greater Phyllopod Bed, found in the Walcott Quarry on Fossil Ridge, between Wapta Mountain and Mount Field, at an elevation of around , around north of the railway town of Field, British Columbia, in the Canadian Rocky Mountains. It is adjacent to Mount Burgess, where Walcott first discovered the Burgess Shale formation. Walcott divided the bed into twelve units based on the rock type and fossil content. Certain fossil beds provide reference levels and can b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Burgess Shale Fossils
The fossils of the Burgess Shale, like the Burgess Shale itself, formed around 505 million years ago in the Mid Cambrian period. They were discovered in Canada in 1886, and Charles Doolittle Walcott collected over 65,000 specimens in a series of field trips up to the alpine site from 1909 to 1924. After a period of neglect from the 1930s to the early 1960s, new excavations and re-examinations of Walcott's collection continue to reveal new species, and statistical analysis suggests that additional discoveries will continue for the foreseeable future. Stephen Jay Gould's book '' Wonderful Life'' describes the history of discovery up to the early 1980s, although his analysis of the implications for evolution has been contested. The fossil beds are in a series of shale layers, averaging and totalling about in thickness. These layers were deposited against the face of a high undersea limestone cliff. All these features were later raised up above current sea level during the cr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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