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Amplectobelua Stephenensis
''Amplectobelua'' (meaning "embracing beast") is an extinct genus of late Early Cambrian Amplectobeluidae, amplectobeluid radiodont, a group of stem arthropods that mostly lived as free-swimming predators during the first half of the Paleozoic Era. Anatomy The body structures other than frontal appendages are only known from the type species ''Amplectobelua symbrachiata''. Like other radiodonts, ''Amplectobelua'' had a pair of jointed frontal appendages, a head covered by dorsal and lateral sclerites (the latter had been misinterpreted as huge eyes), a limbless body with dorsal gills (setal blades), and a series of flaps on both sides that extended along the length of its body. ''Amplectobelua'' had a specialized frontal appendage, in which it has a distinct 3-segmented shaft region and 12-segmented distal articulated region, and the spine on the fourth segment (first segment of distal articulated region) hooked forward to oppose the tip of the appendage, allowing it to gra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cambrian Stage 3
Cambrian Stage 3 is the still unnamed third stage of the Cambrian. It succeeds Cambrian Stage 2 and precedes Cambrian Stage 4, although neither its base nor top have been formally defined. The plan is for its lower boundary to correspond approximately to the first appearance of trilobites, about million years ago, though the globally asynchronous appearance of trilobites warrants the use of a separate, globally synchronous marker to define the base. The upper boundary and beginning of Cambrian Stage 4 is informally defined as the first appearance of the trilobite genera '' Olenellus'' or ''Redlichia'' around million years ago. Naming The International Commission on Stratigraphy has not officially named the 3rd stage of the Cambrian. The stage approximately corresponds to the "Atdabanian", which is used by geologists working in Siberia. Biostratigraphy The oldest trilobite known is '' Lemdadella'' which appears at the beginning of the '' Fallotaspis'' zone. The Cambrian radiat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |