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Gyraulus Gilberti
''Gyraulus'' is a genus of small, mostly air-breathing, freshwater snails, Aquatic animal, aquatic pulmonate gastropod mollusks in the family Planorbidae, the sheep, 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. The minute species ''Gyraulus crista'', although technically a pulmonate gastropod, does not use air for respiration, but instead has a mantle cavity which has much water. Distribution The distribution of this genus is Holarctic. Habitat These snail snails live on water plants in freshwater. Shell description Shell of the species within this genus are small, and are mostly almost planispiral in their coiling. Species Speci ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Early Cretaceous
The Early Cretaceous ( geochronological name) or the Lower Cretaceous (chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145 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 early Aptian Oceanic Anoxic Event 1a (OAE1a) was carbon isotope 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-Manihiki-Hikurangi large igneous province, emplaced in the South Pacific at c. 120 Ma, is by far the largest LIP in Earth's history. The Ontong Java Plateau today covers an area of 1,860,000 km2. In the Indian Ocean another LIP began to form at c. 120 Ma, the Kerguelen P ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |