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Baculites
''Baculites'' ("walking stick rock") is an extinct genus of cephalopods with a nearly straight shell, included in the heteromorph ammonites. The genus, which lived worldwide throughout most of the Late Cretaceous, and which briefly survived the K-Pg mass extinction event, was named by Lamarck in 1799. Life Shell anatomy The adult shell of ''Baculites'' is generally straight and may be either smooth or with sinuous striae or ribbing that typically slant dorso-ventrally forward. The aperture likewise slopes to the front and has a sinuous margin. The venter is narrowly rounded to acute while the dorsum is more broad. The juvenile shell, found at the apex, is coiled in one or two whorls and described as minute, about in diameter. Adult ''Baculites'' ranged in size from about (''Baculites larsoni'') up to in length. As with other ammonites, the shell consisted of a series of camerae, or chambers, that were connected to the animal by a narrow tube called a siphuncle by which ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Baculites
''Baculites'' ("walking stick rock") is an extinct genus of cephalopods with a nearly straight shell, included in the heteromorph ammonites. The genus, which lived worldwide throughout most of the Late Cretaceous, and which briefly survived the K-Pg mass extinction event, was named by Lamarck in 1799. Life Shell anatomy The adult shell of ''Baculites'' is generally straight and may be either smooth or with sinuous striae or ribbing that typically slant dorso-ventrally forward. The aperture likewise slopes to the front and has a sinuous margin. The venter is narrowly rounded to acute while the dorsum is more broad. The juvenile shell, found at the apex, is coiled in one or two whorls and described as minute, about in diameter. Adult ''Baculites'' ranged in size from about (''Baculites larsoni'') up to in length. As with other ammonites, the shell consisted of a series of camerae, or chambers, that were connected to the animal by a narrow tube called a siphuncle by which ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Baculites Grandis Shell
''Baculites'' ("walking stick rock") is an extinct genus of cephalopods with a nearly straight shell, included in the heteromorph ammonites. The genus, which lived worldwide throughout most of the Late Cretaceous, and which briefly survived the K-Pg mass extinction event, was named by Lamarck in 1799. Life Shell anatomy The adult shell of ''Baculites'' is generally straight and may be either smooth or with sinuous striae or ribbing that typically slant dorso-ventrally forward. The aperture likewise slopes to the front and has a sinuous margin. The venter is narrowly rounded to acute while the dorsum is more broad. The juvenile shell, found at the apex, is coiled in one or two whorls and described as minute, about in diameter. Adult ''Baculites'' ranged in size from about (''Baculites larsoni'') up to in length. As with other ammonites, the shell consisted of a series of camerae, or chambers, that were connected to the animal by a narrow tube called a siphuncle by which ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paleocene Ammonites
The term Paleocene ammonites describes families or genera of Ammonoidea that may have survived the Cretaceous–Paleogene extinction event, which occurred 66.043 million years ago. Although almost all evidence indicated that ammonites did not survive past the K–Pg boundary, there is some scattered evidence that some ammonites lived for a short period of time during the Paleocene epoch, although none survived the Danian (66-61 Ma); they were likely extinct within 500,000 years of the K-Pg extinction event, which correlates to roughly 65.5 Ma. The evidence for Paleocene ammonoids is rare and remains controversial. Implications There have been reliable reports of ammonite fossils from the early Paleocene. The most notable fossil finds of Paleocene ammonoids are '' Baculites vertebralis'' and '' Hoploscaphites constrictus'' in Denmark, the survivors joined by '' Eubaculites carinatus'' in the Netherlands. ''Discoscaphites'' and ''Eubaculites'' (potentially along with other ammonit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orthoceras
''Orthoceras'' ("straight horn") is a genus of extinct nautiloid cephalopod restricted to Middle Ordovician-aged marine limestones of the Baltic States and Sweden. This genus is sometimes called ''Orthoceratites''. Note it is sometimes misspelled as ''Orthocera'', ''Orthocerus'' or ''Orthoceros'' . ''Orthoceras'' was formerly thought to have had a worldwide distribution due to the genus' use as a wastebasket taxon for numerous species of conical-shelled nautiloids throughout the Paleozoic and Triassic. Since this work was carried out and re cataloging of the genus, ''Orthoceras'' sensu stricto refers to ''O. regulare'', of Ordovician-aged Baltic Sea limestones of Sweden and neighboring areas. These are slender, elongate shells with the middle of the body chamber transversely constricted, and a subcentral orthochoanitic siphuncle. The surface is ornamented by a network of fine lirae . Many other very similar species are included under the genus '' Michelinoceras''. History of ... [...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] |
Ammonoidea
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 nea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of the entire Phanerozoic. The name is derived from the Latin ''creta'', "chalk", which is abundant in the latter half of the period. It is usually abbreviated K, for its German translation ''Kreide''. The Cretaceous was a period with a relatively warm climate, resulting in high eustatic sea levels that created numerous shallow inland seas. These oceans and seas were populated with now- extinct marine reptiles, ammonites, and rudists, while dinosaurs continued to dominate on land. The world was ice free, and forests extended to the poles. During this time, new groups of mammals and birds appeared. During the Early Cretaceous, flowering plants appeared and began to rapidly diversify, becoming the dominant group of plants across the Earth b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cretaceous–Paleogene Extinction Event
The Cretaceous–Paleogene (K–Pg) extinction event (also known as the Cretaceous–Tertiary extinction) was a sudden mass extinction of three-quarters of the plant and animal species on Earth, approximately 66 million years ago. With the exception of some ectothermic species such as sea turtles and crocodilians, no tetrapods weighing more than survived. It marked the end of the Cretaceous Period, and with it the Mesozoic era, while heralding the beginning of the Cenozoic era, which continues to this day. In the geologic record, the K–Pg event is marked by a thin layer of sediment called the K–Pg boundary, which can be found throughout the world in marine and terrestrial rocks. The boundary clay shows unusually high levels of the metal iridium, which is more common in asteroids than in the Earth's crust. As originally proposed in 1980 by a team of scientists led by Luis Alvarez and his son Walter, it is now generally thought that the K–Pg extinction was cause ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gastropod
The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. There are many thousands of species of sea snails and slugs, as well as freshwater snails, freshwater limpets, and land snails and slugs. The class Gastropoda contains a vast total of named species, second only to the insects in overall number. The fossil history of this class goes back to the Late Cambrian. , 721 families of gastropods are known, of which 245 are extinct and appear only in the fossil record, while 476 are currently extant with or without a fossil record. Gastropoda (previously known as univalves and sometimes spelled "Gasteropoda") are a major part of the phylum Mollusca, and are the most highly diversified class in the phylum, with 65,000 to 80,000 living snail and slug species. The anatomy, behavior, feeding, and re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nacre
Nacre ( , ), also known as mother of pearl, is an organicinorganic composite material produced by some molluscs as an inner shell layer; it is also the material of which pearls are composed. It is strong, resilient, and iridescent. Nacre is found in some of the most ancient lineages of bivalves, gastropods, and cephalopods. However, the inner layer in the great majority of mollusc shells is porcellaneous, not nacreous, and this usually results in a non-iridescent shine, or more rarely in non-nacreous iridescence such as ''flame structure'' as is found in conch pearls. The outer layer of cultured pearls and the inside layer of pearl oyster and freshwater pearl mussel shells are made of nacre. Other mollusc families that have a nacreous inner shell layer include marine gastropods such as the Haliotidae, the Trochidae and the Turbinidae. Physical characteristics Structure and appearance Nacre is composed of hexagonal platelets of aragonite (a form of calcium carbonate) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
