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Aptychus
An aptychus is a type of marine fossil. It is a hard anatomical structure, a sort of curved shelly plate, now understood to be part of the body of an ammonite. Paired aptychi have, on rare occasions, been found at or within the aperture of ammonite shells. The aptychus was usually composed of calcite, whereas the ammonite shell was aragonite. Aptychi can be found well-preserved as fossils, but usually quite separate from ammonite shells. This circumstance led to them being initially classified as valves of bivalves (clams), which they do somewhat resemble. Aptychi are found in rocks from the Devonian period through to those of the Cretaceous period. There are many forms of aptychus, varying in shape and in the sculpture of the inner and outer surfaces. However, because they are so rarely found in position within the ammonite shell, it is often unclear which kind of aptychus belonged to which species of ammonite. When only a single plate is present, as is sometimes the case, th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aptychi Examples Function
An aptychus is a type of marine fossil. It is a hard anatomical structure, a sort of curved shelly plate, now understood to be part of the body of an ammonite. Paired aptychi have, on rare occasions, been found at or within the aperture of ammonite shells. The aptychus was usually composed of calcite, whereas the ammonite shell was aragonite. Aptychi can be found well-preserved as fossils, but usually quite separate from ammonite shells. This circumstance led to them being initially classified as valves of bivalves (clams), which they do somewhat resemble. Aptychi are found in rocks from the Devonian period through to those of the Cretaceous period. There are many forms of aptychus, varying in shape and in the sculpture of the inner and outer surfaces. However, because they are so rarely found in position within the ammonite shell, it is often unclear which kind of aptychus belonged to which species of ammonite. When only a single plate is present, as is sometimes the case, th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ammonite
Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids (i.e., octopuses, squid and cuttlefish) than they are to shelled nautiloids such as the living ''Nautilus'' species. The earliest ammonites appeared during the Devonian, with the last species vanishing during the Cretaceous–Paleogene extinction event. Ammonites are excellent index fossils, and linking the rock layer in which a particular species or genus is found to specific geologic time periods is often possible. Their fossil shells usually take the form of planispirals, although some helically spiraled and nonspiraled forms (known as heteromorphs) have been found. The name "ammonite", from which the scientific term is derived, was inspired by the spiral shape of their fossilized shells, which somewhat resemble tightly coiled rams' horns. Pliny the Elder ( 79 AD near Pomp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trigonellites Latus
''Trigonellites'' is an extinct genus of basal ammonite, known from two or three species, discovered in outcrops of the Late Jurassic-aged Kimmeridge Clay Formation in Ely and Cumnor, England and possibly also an unnamed Early Triassic-aged rock formation in Bindlach, Germany. J. Prestwich. (1879). On the discovery of a species of ''Iguanodon'' in the Kimmeridge Clay near Oxford; and a notice of a very fossiliferous band of the Shotover Sands. ''Geological Magazine, new series, decade'' 2 6(5):193-195 It was originally classified as a bivalve,G. A. Goldfuss. (1863). Abbildungen und Beschreibungen der Petrefacten Deutschlands und der angrenzenden Länder. Divisio Quarta: Molluscorum acephalicorum reliquiae. Muschelthiere der Vorwelt. 1. Bivalvia. ''Petrefacta Germaniae'' 4(1):1-273 but it has since been classed as an ammonite species. Only two species once placed in the genus are still considered valid today: ''T. latus'' and ''T. curvirostris'', with one dubious species, ''T. simp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Laevaptychus
''Laevapetchyus'' is a genus of ammonites. In Europe, most representatives of the genus ''Laevaptychus'' occur by the end of the early Tithonian. ''Laevaptychus latus'' is common throughout the Upper Jurassic and is abundant in the Alpine-Mediterranean region. It is also recorded in southern Arabia, Tunisia, Somalia and the western North Atlantic. In Mexico, the first records of ''Aptychus latus'' (= ''Laevaptychus latus'') are provided from the Upper Jurassic of the La Caja Formation at Sierra de Catorce, San Luis Potosí and from the upper Kimmeridgian "Couche à ''Haploceras'' d. gr. ''Fialar''" of Sierra de Santa Rosa, Mazapil, Zacatecas , image_map = Zacatecas in Mexico (location map scheme).svg , map_caption = State of Zacatecas within Mexico , coordinates = , coor_pinpoint = , coordinates_footnotes = , subdivision_type .... References {{Taxonbar, from=Q28432804 Ammonitida genera ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Operculum (animal)
An operculum is an anatomical feature, a stiff structure resembling a lid or a small door that opens and closes, and thus controls contact between the outside world and an internal part of an animal. Examples include: * An operculum (gastropod), a single lid that (in its most complete form) closes the aperture of the shell when the animal is retracted, and thus protects the internal soft parts of the animal that are not completely covered by the shell. The operculum lies on the top rear part of the foot. When the foot is retracted, the operculum is rotated 180° and closes the shell. * An operculum (fish), a flap that covers the gills in bony fishes and chimaeras. * The cover that rapidly opens a cnida of a cnidarian such as a jellyfish or a sea anemone. The lid may be a single hinged flap or three hinged flaps arranged like slices of pie. * In insects, the operculum is the name for one or more lids covering the tympanal cavity. A subgenital operculum is exhibited in phasmoidea an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Perisphinctes
''Perisphinctes'' is an extinct genus of ammonite cephalopod. They lived during the Middle to Late Jurassic epochs and serve as an index fossil for that time period. The species ''P. boweni'' was named after the English chemist and geologist E. J. Bowen Edmund ("Ted") John Bowen Fellow of the Royal Society, FRS (29 April 1898 – 19 November 1980) was a British physical chemist. Life Born in Worcester, England, Worcester, England, E. J. Bowen attended the Royal Grammar School Worcester. He w ... (1898–1980). Distribution Shells of species belonging to this genus have been found in the Jurassic of Antarctica, Argentina, Chile, Cuba, Egypt, Ethiopia, France, Germany, Hungary, India, Iran, Italy, Japan, Madagascar, Poland, Portugal, Russia, Saudi Arabia, Spain, Switzerland, the United Kingdom and Yemen. Gallery File:Perisphinctes (Prosososphinctes) virguloides (Waagen).jpg, ''Perisphinctes virguloides'' File:Perisphinctes cf choffati.JPG, '' Perisphinctes choffati'' File: ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nautilus
The nautilus (, ) is a pelagic marine mollusc of the cephalopod family Nautilidae. The nautilus is the sole extant family of the superfamily Nautilaceae and of its smaller but near equal suborder, Nautilina. It comprises six living species in two genera, the type of which is the genus ''Nautilus''. Though it more specifically refers to species ''Nautilus pompilius'', the name chambered nautilus is also used for any of the Nautilidae. All are protected under CITES Appendix II. Depending on species, adult shell diameter is between 4 and 10 inches. Nautilidae, both extant and extinct, are characterized by involute or more or less convolute shells that are generally smooth, with compressed or depressed whorl sections, straight to sinuous sutures, and a tubular, generally central siphuncle.Kümmel, B. 1964. Nautiloidae-Nautilida, in the Treatise on Invertebrate Paleontology, Geological Society of America and Univ of Kansas Press, Teichert and Moore eds. Having survived relatively u ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mirror Image
A mirror image (in a plane mirror) is a reflected duplication of an object that appears almost identical, but is reversed in the direction perpendicular to the mirror surface. As an optical effect it results from reflection off from substances such as a mirror or water. It is also a concept in geometry and can be used as a conceptualization process for 3-D structures. In geometry and geometrical optics In two dimensions In geometry, the mirror image of an object or two-dimensional figure is the virtual image formed by reflection in a plane mirror; it is of the same size as the original object, yet different, unless the object or figure has reflection symmetry (also known as a P-symmetry). Two-dimensional mirror images can be seen in the reflections of mirrors or other reflecting surfaces, or on a printed surface seen inside-out. If we first look at an object that is effectively two-dimensional (such as the writing on a card) and then turn the card to face a mirror, the obj ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cephalopod Beak
All extant taxon, extant cephalopods have a two-part beak, or Rostrum (anatomy), rostrum, situated in the buccal mass and surrounded by the muscular Cephalopod limb, head appendages. The Dorsal (anatomy), dorsal (upper) mandible fits into the ventral (lower) mandible and together they function in a scissor-like fashion.Young, R.E., M. Vecchione & K.M. Mangold (1999)Cephalopoda Glossary Tree of Life Web Project. The beak may also be referred to as the mandibles or jaws.Tanabe, K., Y. Hikida & Y. Iba (2006). Two coleoid jaws from the Upper Cretaceous of Hokkaido, Japan. ''Journal of Paleontology'' 80(1): 138–145. Fossilised remains of beaks are known from a number of cephalopod groups, both extant and extinct, including squids, octopuses, belemnites, and vampyromorphs. aptychus, Aptychi – paired plate-like structures found in ammonites – may also have been jaw elements. Composition Composed primarily of chitin and cross-linked proteins, beaks are more-or-less indigestible a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cephalopod
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 ident ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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