Sirenites

	Sirenites ''Sirenites'' is a genus of ammonoid 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) ... cephalopods from the Upper Triassic included in the Ceratitida, and type for the trachyceratid subfamily Sirenitinae. ''Sirenites'' has a compressed shell with distinct furrow running along the outer rim. Sides of the whorls are flattened to convex and covered with sigmoidal ribs that split on tubercles near the outer shoulder. there are two rows of tubercles on whorl sides and one on the inner, or umbilicle, shoulder. Although ''Sirenites'' is a ceratitid ammonoid, it suture is ammonitic. References Arkell, et al., Mesozoic Ammonoidea, Treatise on Invertebrate Paleontology, Part L, Mollusca 4, Geological Society of America. 1957. Trachyceratidae Triassic ammonites Ceratitida genera Tr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
	Trachyceratidae The Trachyceratidae is an extinct family of ceratitid ammonoid cephalopods. The Trachyceratidae makes up part of the superfamily Trachyceratoidea along with such families as the Buchitidae, Distichitidae, Dronovitidae and Noridiscitidae. The Trachyceratoidea is also known by the junior synonym Trachycerataceae. Fossil record Fossils of ''Trachyceratidae'' are found in marine strata from the Devonian to the Triassic. Fossils are known from many localities in Afghanistan, Canada, China, Europe (Slovenia, Spain, Switzerland, Ukraine), India, Japan, the Russian Federation, Thailand, and the United States. Description Trachyceratid shells are more or less involute and highly ornamented. They have their whorl sides covered with flexuous ribs that are usually tuberculate. The venters generally have a median furrow bordered by rows of tubercles or continuous keels. Classification Trachyceratidae '' Boreotrachyceras'' Konstantinov 2012 '' Brotheotrachyceras'' Urlichs 1994 '' ... [...More Info...] [...Related Items...] OR:* [Wikipedia] [Google] [Baidu]
picture info	Triassic The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period of the Mesozoic Era. Both the start and end of the period are marked by major extinction events. The Triassic Period is subdivided into three epochs: Early Triassic, Middle Triassic and Late Triassic. The Triassic began in the wake of the Permian–Triassic extinction event, which left the Earth's biosphere impoverished; it was well into the middle of the Triassic before life recovered its former diversity. Three categories of organisms can be distinguished in the Triassic record: survivors from the extinction event, new groups that flourished briefly, and other new groups that went on to dominate the Mesozoic Era. Reptiles, especially archosaurs, were the chief terrestrial vertebrates during this time. A specialized subgroup of archo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
picture info	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]
picture info	Triassic Ammonites The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period of the Mesozoic Era. Both the start and end of the period are marked by major extinction events. The Triassic Period is subdivided into three epochs: Early Triassic, Middle Triassic and Late Triassic. The Triassic began in the wake of the Permian–Triassic extinction event, which left the Earth's biosphere impoverished; it was well into the middle of the Triassic before life recovered its former diversity. Three categories of organisms can be distinguished in the Triassic record: survivors from the extinction event, new groups that flourished briefly, and other new groups that went on to dominate the Mesozoic Era. Reptiles, especially archosaurs, were the chief terrestrial vertebrates during this time. A specialized subgroup of archosaurs ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
	Ceratitida Genera Ceratitida is an order that contains almost all ammonoid cephalopod genera from the Triassic as well as ancestral forms from the Upper Permian, the exception being the phylloceratids which gave rise to the great diversity of post Triassic ammonites. Ceratitids overwhelmingly produced planospirally coiled discoidal shells that may be evolute with inner whorls exposed or involute with only the outer whorl showing. In a few later forms the shell became subglobular, in others, trochoidal or uncoiled. Sutures are typically ceratitic, with smooth saddles and serrate or digitized lobes. In a few the sutures are goniatitic while in others they are ammonitic. Taxonomy * Ceratitida Ceratitoidea Choristoceratoidea Clydonitoidea Danubitoidea Dinaritoidea Lobitoidea Meekoceratoidea Megaphyllitoidea Nathorstitoidea Noritoidea Otoceratoidea Pinacoceratoidea Ptychitoidea Sageceratoidea Tropitoidea Xenodiscoidea Only eight superfamilies are shown i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]