Angarella

	Angarella ''Angarella'' is an early palaeozoic genus of problematic fossils, long held to belong to the molluscs based on supposed similarities in its musculature to that of hyolith Hyoliths are animals with small conical surface, conical animal shell, shells, known as fossils from the Palaeozoic era. They are at least considered as lophotrochozoan, and possibly being lophophorates, a group which includes the brachiopods, w ...s (now known to be brachiopod relativesMoysiuk, J., M. R. Smith, and J.-B. Caron. 2017: Hyoliths are Palaeozoic lophophorates. Nature 541:394–397.) and mobergellids, but now considered to represent a brachiopod based on its calcitic mineralogy and paired symmetrical valves. Its dorsal valve is low and conical, whereas its ventral is flat and follows the contours of the substrate, indicating a cementing habit. The dorsal valve bears a series of symmetrical muscle impressions, forming a ring concentric with the edge of the shell. The ventral valve has a pair ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
picture info	Molluscs Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant taxon, extant species of molluscs are recognized. The number of fossil species is estimated between 60,000 and 100,000 additional species. The proportion of undescribed species is very high. Many taxa remain poorly studied. Molluscs are the largest marine biology, marine phylum, comprising about 23% of all the named marine organisms. Numerous molluscs also live in freshwater mollusc, freshwater and Terrestrial molluscs, terrestrial habitats. They are highly diverse, not just in size and anatomical structure, but also in behaviour and habitat. The phylum is typically divided into 7 or 8 Taxonomy (biology), taxonomic class (biology), classes, of which two are entirely extinct. Cephalopod molluscs, such as squid, cuttlefish, and octopuses, are among the most neurobiology, neurologically advanced of all inve ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
picture info	Hyolith Hyoliths are animals with small conical surface, conical animal shell, shells, known as fossils from the Palaeozoic era. They are at least considered as lophotrochozoan, and possibly being lophophorates, a group which includes the brachiopods, while others consider them as being basal lophotrochozoans, or even Mollusca, molluscs. Morphology The shell of a hyolith is typically one to four centimeters in length, triangular or elliptical in cross section. Some species have rings or stripes. It comprises two parts: the main conical shell (previously referred to as a ‘conch’) and a cap-like Operculum (animal), operculum. Some also had two curved supports known as ''helens'' They are calcium carbonate, calcareous – probably aragonitic All of these structures grew by marginal accretion. Shell microstructure The orthothecid shell has an internal layer with a microstructure of transverse bundles, and an external layer comprising longitudinal bundles. Helens Some hyoliths ha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
	Mobergellid The Mobergellidae are a family of small shelly fossils from the lower Cambrian. The small shells vary widely in shape, but are all bilaterally symmetrical discs with paired muscle scars radiating from the centre of the internal surface. References Cambrian invertebrates Prehistoric animal families Cambrian first appearances Cambrian extinctions Animal families {{cambrian-animal-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
picture info	Brachiopod Brachiopods (), phylum Brachiopoda, are a phylum of trochozoan animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, while the front can be opened for feeding or closed for protection. Two major categories are traditionally recognized, articulate and inarticulate brachiopods. The word "articulate" is used to describe the tooth-and-groove structures of the valve-hinge which is present in the articulate group, and absent from the inarticulate group. This is the leading diagnostic skeletal feature, by which the two main groups can be readily distinguished as fossils. Articulate brachiopods have toothed hinges and simple, vertically-oriented opening and closing muscles. Conversely, inarticulate brachiopods have weak, untoothed hinges and a more complex system of vertical and oblique (diagonal) muscles used to keep the two valves aligned. In many brachiopods, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
	Dorsal Valve Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage * Dorsal consonant, a consonant articulated with the back of the tongue * Dorsal fin, the fin located on the back of a fish or aircraft * Dorsal transcription factor, a maternally synthesized transcription factor {{disambig de:Dorsale fr:Dorsale it:Dorsale ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]