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Lyecoceras
''Lyecoceras'' is a gender of slender endogastrically curved orthocerid Orthocerida is an order of extinct Orthoceratoid cephalopods also known as the Michelinocerida that lived from the Early Ordovician () possibly to the Late Triassic (). A fossil found in the Caucasus suggests they may even have survived until ...s, so determined by identification of the hyponomic sinus on the concave side. The siphuncle is dorsal of the center, toward the convex side of the shell. The surface has faint longitudinal striae and is encircled by weak annulations. ''Lyecoceras'' was first found in the Middle Silurian of Sweden, and since in the Silurian of Sochuan Provence, China. References * Walter C. Sweet, 1964. Nautiloidea - Orthocerida; Treatise on Invertebrate Paleontology, Part K. Geological Society of America Prehistoric nautiloid genera {{paleo-nautiloidea-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Silurian
The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozoic Era. As with other geologic periods, the rock beds that define the period's start and end are well identified, but the exact dates are uncertain by a few million years. The base of the Silurian is set at a series of major Ordovician–Silurian extinction events when up to 60% of marine genera were wiped out. One important event in this period was the initial establishment of terrestrial life in what is known as the Silurian-Devonian Terrestrial Revolution: vascular plants emerged from more primitive land plants, dikaryan fungi started expanding and diversifying along with glomeromycotan fungi, and three groups of arthropods (myriapods, arachnids and hexapods) became fully terrestrialized. A significant evolutionary milestone during ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
