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Demopolis Chalk
The Demopolis Chalk is a geological formation in North America, within the U.S. states of Alabama, Mississippi, and Tennessee. The chalk was formed by pelagic sediments deposited along the eastern edge of the Mississippi embayment during the middle Campanian stage of the Late Cretaceous.Carr, T.D., Williamson, T.E., & Schwimmer, D.R. 2005. A new genus and species of tyrannosauroid from the Late Cretaceous (middle Campanian) Demopolis Formation of Alabama. ''Journal of Vertebrate Paleontology'' 25(1): 119–143. It is a unit of the Selma Group and consists of the upper Bluffport Marl Member and a lower unnamed member. Dinosaur and mosasaur remains are among the fossils that have been recovered from the Demopolis Chalk.Weishampel, David B; et al. (2004). "Dinosaur distribution (Late Cretaceous, North America)." In: Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. Pp. 574-588. . Vertebrate paleofauna ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geological Formation
A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exposed in a geographical region (the stratigraphic column). It is the fundamental unit of lithostratigraphy, the study of strata or rock layers. A formation must be large enough that it can be mapped at the surface or traced in the subsurface. Formations are otherwise not defined by the thickness of their rock strata, which can vary widely. They are usually, but not universally, tabular in form. They may consist of a single lithology (rock type), or of alternating beds of two or more lithologies, or even a heterogeneous mixture of lithologies, so long as this distinguishes them from adjacent bodies of rock. The concept of a geologic formation goes back to the beginnings of modern scientific geology. The term was used by Abraham Gottlob Wer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stage (stratigraphy)
In chronostratigraphy, a stage is a succession of rock strata laid down in a single age on the geologic timescale, which usually represents millions of years of deposition. A given stage of rock and the corresponding age of time will by convention have the same name, and the same boundaries. Rock series are divided into stages, just as geological epochs are divided into ages. Stages can be divided into smaller stratigraphic units called chronozones. (See chart at right for full terminology hierarchy.) Stages may also be divided into substages or indeed grouped as superstages. The term faunal stage is sometimes used, referring to the fact that the same fauna (animals) are found throughout the layer (by definition). Definition Stages are primarily defined by a consistent set of fossils (biostratigraphy) or a consistent magnetic polarity (see paleomagnetism) in the rock. Usually one or more index fossils that are common, found worldwide, easily recognized, and limited to a sing ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sclerorhynchidae
Ganopristidae is an extinct family of cartilaginous fish from the Cretaceous belonging to the suborder Sclerorhynchoidei. While the name Sclerorhynchidae is often used for this family, it is a junior synonym of Ganopristidae. This family contains the genera ''Libanopristis ''Libanopristis'' is an extinct genus of ganopristid sclerorhynchoid that lived in Lebanon during the Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geolog ...'', '' Micropristis'', and '' Sclerorhynchus''. The type genus ''Ganopristis'' is considered to be a junior synonym of ''Sclerorhynchus''. References {{Taxonbar, from=Q108908110 Prehistoric cartilaginous fish families Rajiformes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ischyrhiza
''Ischyrhiza'' is an extinct genus of sclerorhynchoid ray from the Late Cretaceous and Early Paleogene. It had a large, toothed rostrum closely resembling that of a modern-day sawfish. Despite formerly being classified within a family of extinct sawfish-like rays known as Sclerorhynchidae, phylogenetic analyses indicate that ''Ischyrhiza, Schizorhiza'', and ''Onchopristis'' form a distinct clade that groups closer with the extant family Rajidae, which contains the true skates, possibly rendering the suborder Sclerorhynchoidei paraphyletic. Fossils of the genus have been found in Canada, the United States, the Aguja Formation of Mexico, the Bissekty Formation of Uzbekistan, the Tamayama Formation of Japan, the Dukamaje Formation of Niger, the El Molino Formation The El Molino Formation is a Maastrichtian geologic formation pertaining to the Puca Group of central Bolivia. The formation comprises fine-grained sandstones and sandy limestones with stromatolites deposited ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anacoracidae
Anacoracidae is a family of extinct mackerel sharks that lived during the Cretaceous. It includes four valid genera: '' Nanocorax'', '' Ptychocorax'', ''Scindocorax'', and ''Squalicorax''. Two previously-included genera, ''Galeocorax'' and ''Pseudocorax ''Pseudocorax'' is an extinct genus of mackerel sharks that lived during the Late Cretaceous. It contains six valid species that have been found in Europe, the Middle East, North Africa, and North America. It was formerly assigned to the family ...'', were reassigned to the family Pseudocoracidae. References Shark families Prehistoric cartilaginous fish families Taxa named by Henri Cappetta Cretaceous first appearances Cretaceous extinctions {{paleo-shark-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Squalicorax
''Squalicorax'', commonly known as the crow shark, is a genus of extinct lamniform shark known to have lived during the Cretaceous period. The genus had a global distribution in the Late Cretaceous epoch. Multiple species within this genus are considered to be wastebasket taxon due to morphological similarities in the teeth. Etymology The name ''Squalicorax'' is derived from the Latin ''squalus'' for shark and the Greek κόραξ, "''korax''" for raven. Description These sharks are of medium size, up to 5 m (usually around 2 m) in length. Their bodies were similar to the modern gray reef sharks, but the shape of the teeth is strikingly similar to that of a tiger shark. The teeth are numerous, relatively small, with a curved crown and serrated, up to 2.5 – 3 cm in height. Large numbers of fossil teeth have been found in Europe, North Africa, and North America. Squalicorax is one of three Cretaceous lamniformes to garner serrations along with ''Pseudocorax'' an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mitsukurinidae
Mitsukurinidae is a family of sharks with one living genus, ''Mitsukurina'', and four fossil genera: ''Anomotodon'', '' Protoscapanorhynchus'', ''Scapanorhynchus'', and '' Woellsteinia'', though some taxonomists consider ''Scapanorhynchus'' to be a synonym of ''Mitsukurina''. The only known living species is the goblin shark, ''Mitsukurina owstoni''. This family of sharks is named in honour of Kakichi Mitsukuri who brought the holotype of the only species in this family to David Starr Jordon to be scientifically described. The most distinctive characteristic of the goblin sharks is the long, trowel-shaped, beak-like snout, much longer than those of other sharks. Its long snout is covered with ampullae of Lorenzini that enable it to sense minute electric fields produced by nearby prey, which it can snatch up by rapidly extending its jaws. They also possess long, protrusible jaws. When the jaws are retracted, the shark resembles a grey nurse shark The sand tiger shark (''Car ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scapanorhynchus
''Scapanorhynchus'' (from el, σκάφιου , 'shovel' and el, ῥύγχος 'snout') is an extinct genus of shark that lived from the early Cretaceous until possibly the Miocene if ''S. subulatus'' is a mitsukurinid and not a sand shark.Capetta, H., Chondrichthyes II, Mesozoic and Cenozoic Elasmobranchii, vol. 3B of Handbook of Paleoichthyology, Stuttgart, New York: Gustav Fischer Verlag, 1987.Glickman, L. S., and A. O. Averianov. "Evolution of the Cretaceous Lamnoid sharks of the genus Eostriatolamia." PALEONTOLOGICAL JOURNAL C/C OF PALEONTOLOGICHESKII ZHURNAL 32 (1998): 376-384/ref> Their extreme similarities to the living goblin shark, ''Mitsukurina owstoni'', lead some experts to consider reclassifying it as ''Scapanorhynchus owstoni''. However, most shark specialists regard the goblin shark to be distinct enough from its prehistoric relatives to merit placement in its own genus. ''Scapanorhynchus'' had an elongated, albeit flattened snout and sharp awl Awl may ref ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Squalicorax2DB
''Squalicorax'', commonly known as the crow shark, is a genus of extinct lamniform shark known to have lived during the Cretaceous period. The genus had a global distribution in the Late Cretaceous epoch. Multiple species within this genus are considered to be wastebasket taxon due to morphological similarities in the teeth. Etymology The name ''Squalicorax'' is derived from the Latin ''squalus'' for shark and the Greek κόραξ, "''korax''" for raven. Description These sharks are of medium size, up to 5 m (usually around 2 m) in length. Their bodies were similar to the modern gray reef sharks, but the shape of the teeth is strikingly similar to that of a tiger shark. The teeth are numerous, relatively small, with a curved crown and serrated, up to 2.5 – 3 cm in height. Large numbers of fossil teeth have been found in Europe, North Africa, and North America. Squalicorax is one of three Cretaceous lamniformes to garner serrations along with ''Pseudocorax'' a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Otodontidae
Otodontidae is an extinct family of sharks belonging to the order Lamniformes. Its members have been described as megatoothed sharks. They lived from the Early Cretaceous to the Pliocene, and included genera such as ''Carcharocles'' and ''Otodus,'' including the giant megalodon. Recent studies of the newly described genus ''Megalolamna'' indicate that the members of the genus ''Carcharocles'' should be reclassified as members of the genus ''Otodus''. The genus ''Cretalamna ''Cretalamna'' is a genus of extinct otodontid shark that lived from the latest Early Cretaceous to Eocene epoch (about 103 to 46 million years ago). It is considered by many to be the ancestor of the largest sharks to have ever lived, ''Otodu ...'' which lived from the mid-Cretaceous-Paleogene is believed to be directly ancestral to ''Otodus,'' and thus to megalodon. References Shark families Albian first appearances Pliocene extinctions {{paleo-shark-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cretolamna
''Cretalamna'' is a genus of extinct otodontid shark that lived from the latest Early Cretaceous to Eocene epoch (about 103 to 46 million years ago). It is considered by many to be the ancestor of the largest sharks to have ever lived, '' Otodus angustidens'', '' Otodus chubutensis'', and '' Otodus megalodon''. Taxonomy Research History ''Cretalamna'' was first described by Swiss naturalist Louis Agassiz using five teeth previously identified as the common smooth-hound and collected by English paleontologist Gideon Mantell from the Southerham Grey Pit near Lewes, East Sussex. In his 1835 publication ''Rapport sur les poissons fossiles découverts en Angleterre'', he reidentified them as a new species of porbeagle shark under the taxon ''Lamna appendiculata''. In 1843, Agassiz published ''Recherches sur les poissons fossiles'', which reexamined Mantell's five teeth. Using them, eight additional teeth collected by Mantell, and twenty more teeth collected by various paleontolog ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cartilaginous Fish
Chondrichthyes (; ) is a class that contains the cartilaginous fishes that have skeletons primarily composed of cartilage. They can be contrasted with the Osteichthyes or ''bony fishes'', which have skeletons primarily composed of bone tissue. Chondrichthyes are jawed vertebrates with paired fins, paired nares, scales, and a heart with its chambers in series. Extant chondrichthyes range in size from the 10 cm (3.9 in) finless sleeper ray to the 10 m (32 ft) whale shark. The class is divided into two subclasses: Elasmobranchii (sharks, rays, skates, and sawfish) and Holocephali ( chimaeras, sometimes called ghost sharks, which are sometimes separated into their own class). Within the infraphylum Gnathostomata, cartilaginous fishes are distinct from all other jawed vertebrates. Anatomy Skeleton The skeleton is cartilaginous. The notochord is gradually replaced by a vertebral column during development, except in Holocephali, where the notochord stays intact. In some deepw ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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