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Belemnitella Bulbosa
''Belemnitella bulbosa'' is a species of belemnite from the Late Cretaceous of North America. It is known only from two localities - the Pierre Shale and Fox Hills Formations. ''B. bulbosa'' had a slender somewhat cylindrical rostrum (guard) with a slightly expanded front opening. Like other members of the genus '' Belemnitella'', it had a dorsal ridge on the rostrum. The phragmocone The phragmocone is the chambered portion of the shell of a cephalopod. It is divided by septa into camerae. In most nautiloids and ammonoids, the phragmocone is a long, straight, curved, or coiled structure, in which the camarae are linked by a ... is about the same size or slightly longer than the rostrum and has an oval cross-section. References Belemnites {{paleo-cephalopod-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Species
In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can reproduction, produce Fertility, fertile offspring, typically by sexual reproduction. Other ways of defining species include their karyotype, DNA sequence, morphology (biology), morphology, behaviour or ecological niche. In addition, paleontologists use the concept of the chronospecies since fossil reproduction cannot be examined. The most recent rigorous estimate for the total number of species of eukaryotes is between 8 and 8.7 million. However, only about 14% of these had been described by 2011. All species (except viruses) are given a binomial nomenclature, two-part name, a "binomial". The first part of a binomial is the genus to which the species belongs. The second part is called the specifi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Belemnite
Belemnitida (or the belemnite) is an extinct order of squid-like cephalopods that existed from the Late Triassic to Late Cretaceous. Unlike squid, belemnites had an internal skeleton that made up the cone. The parts are, from the arms-most to the tip: the tongue-shaped pro-ostracum, the conical phragmocone, and the pointy guard. The calcitic guard is the most common belemnite remain. Belemnites, in life, are thought to have had 10 hooked arms and a pair of fins on the guard. The chitinous hooks were usually no bigger than , though a belemnite could have had between 100 and 800 hooks in total, using them to stab and hold onto prey. Belemnites were an important food source for many Mesozoic marine creatures, both the adults and the planktonic juveniles, and likely played an important role in restructuring marine ecosystems after the Triassic–Jurassic extinction event. They may have laid between 100 and 1,000 eggs. Some species may have been adapted to speed and swam in the tu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Late Cretaceous
The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', the Latin word for the white limestone known as chalk. The chalk of northern France and the white cliffs of south-eastern England date from the Cretaceous Period. Climate During the Late Cretaceous, the climate was warmer than present, although throughout the period a cooling trend is evident. The tropics became restricted to equatorial regions and northern latitudes experienced markedly more seasonal climatic conditions. Geography Due to plate tectonics, the Americas were gradually moving westward, causing the Atlantic Ocean to expand. The Western Interior Seaway divided North America into eastern and western halves; Appalachia and Laramidia. India maintained a northward course towards Asia. In the Southern Hemisphere, Australia a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pierre Shale
The Pierre Shale is a geologic formation or series in the Upper Cretaceous which occurs east of the Rocky Mountains in the Great Plains, from Pembina Valley in Canada to New Mexico. The Pierre Shale was described by Meek and Hayden in 1862 in the Proceedings of the Academy of Sciences (Philadelphia). They described it as a dark-gray shale, fossiliferous, with veins and seams of gypsum, and concretions of iron oxide. The Pierre Shale is about 700 feet (210m) thick at the type locality. It overlies the Niobrara division and underlies the Fox Hills beds. It was named for an occurrence near Fort Pierre on the Missouri River in South Dakota. The Pierre Shale is of marine origin and was deposited in the Western Interior Seaway. It is correlative with other marine shales that occur farther west, such as the Bearpaw Shale, Mancos Shale and the Lewis Shale. It correlates with the Lea Park Formation in central Alberta. The Pierre is overlain by marginal marine deposits of the F ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fox Hills Formation
The Fox Hills Formation is a Cretaceous geologic formation in the northwestern Great Plains of North America. It is present from Alberta on the north to Colorado in the south. Fossil remains of dinosaurs, including tyrannosaurs, as well as large marine reptiles, such as mosasaurs, have been recovered from the formation. Lithology The Fox Hills Formation consists of marginal marine yellow to grey sandstone with shale interbeds. It was deposited as a regressive sequence of barrier islands during the retreat of the Western Interior Seaway in Late Cretaceous time. In its eastern extents, the formation is underlain by the marine Pierre Shale in the United States and by the equivalent Bearpaw Formation in Canada, while in western ranges in Montana and Wyoming it overlies the Lewis Shale. The Fox Hills is overlain by continental sediments of the Laramie Formation in Colorado and the Lance Formation in Wyoming, the later being the equivalent of the overlying Hell Creek Formation in Mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Belemnitella
''Belemnitella'' is a genus of belemnite from the Late Cretaceous of Europe and North America. ''Belemnitella'' was a squidlike animal, probably related to the ancestors of modern squids and cuttlefish. The shell was internal. The rostrum or guard is found the most often and possesses a distinctive slit at its ventral surface and a ridge on the dorsal surface. The phragmocone (internal shell) has a small protoconch at its tip, and fit into the cavity and the guard. It also had septa and a ventral siphuncle (tube filled with living tissues running through chambers) within the phragmocone, projecting forward as a beak-like blade. It had growth layers like tree rings, seen within the cavity of the organism and when the cone is sectioned. The cone was light-brown and glassy in appearance. It is distributed widely in North America. A specimen of a belemnoid had been found in Germany, clearly preserving 10 tentacles as carbon films, showing that belemnoids are similar to squids.''Nati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phragmocone
The phragmocone is the chambered portion of the shell of a cephalopod. It is divided by septa into camerae. In most nautiloids and ammonoids, the phragmocone is a long, straight, curved, or coiled structure, in which the camarae are linked by a siphuncle which determines buoyancy by means of gas exchange. Despite this benefit, such a large shell adds to the mass of the animal, and hence is disadvantageous in catching fast-moving prey. Some nautiloids, such as the Silurian Ascocerida, dropped the phragmocone upon maturity, presumably to increase speed and maneuverability. They thus became the early Paleozoic equivalent of coleoids. The early coleoids and belemnoids adopted a different approach: the phragmocone was retained but became internal and reduced. In general the shell in cephalopods tends to be vestigial or absent. Fossil record Being the only biomineralised part of most cephalopods, the phragmocone is typically the only part to enter the fossil record. It is somet ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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