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Gyraulus Sauerzopfi
''Gyraulus'' is a genus of small, mostly air-breathing, freshwater snails, aquatic pulmonate gastropod mollusks in the family Planorbidae, the ram's horn snails. The genus ''Gyraulus'' is known from the Early Cretaceous to the present. Fossils attributed to ''Gyraulus'' sp. have been found in the lakebottom sediments of the Yixian Formation in China, dating to 125 million years ago.Pan, H. and Zhu, X. (2007). "Early Cretaceous non-marine gastropods from the Xiazhuang Formation in North China." ''Cretaceous Research'', 28(2): 215-224. Description Shells of the species within this genus are small, and are mostly almost planispiral in their coiling. Distribution and habitat The distribution of this genus is Holarctic. These snail snails live on water plants in freshwater. Species The following species are recognised in the genus ''Gyraulus'': *'' Gyraulus acronicus'' *†'' Gyraulus aegaeus'' *†''Gyraulus albertanus'' *'' Gyraulus albidus'' *''Gyraulus albus'' *†'' Gyra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Early Cretaceous
The Early Cretaceous (geochronology, geochronological name) or the Lower Cretaceous (chronostratigraphy, chronostratigraphic name) is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 143.1 Megaannum#SI prefix multipliers, Ma to 100.5 Ma. Geology Proposals for the exact age of the Barremian–Aptian boundary ranged from 126 to 117 Ma until recently (as of 2019), but based on drillholes in Svalbard the defining Anoxic event#Cretaceous, early Aptian Oceanic Anoxic Event 1a (OAE1a) was dated to 123.1±0.3 Ma, limiting the possible range for the boundary to c. 122–121 Ma. There is a possible link between this anoxic event and a series of Early Cretaceous large igneous provinces (LIP). The Ontong Java Plateau, Ontong Java-Manihiki Plateau, Manihiki-Hikurangi Plateau, Hikurangi large igneous province, emplaced in the South Pacific at c. 120 Ma, is by far the largest LIP in Earth's history. The Onto ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
