Metasequoia
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Metasequoia Temporal range: 70.0–0 Ma Late Cretaceous to Recent |
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| Scientific classification | |
| Kingdom: | Plantae |
| Division: | Pinophyta |
| Class: | Pinopsida |
| Order: | Pinales |
| Family: | Cupressaceae |
| Subfamily: | Sequoioideae |
| Genus: |
Metasequoia Miki, 1941 |
| Species | |
Metasequoia (dawn redwood) is a fast-growing, deciduous tree, and the sole living species, Metasequoia glyptostroboides, is one of three species of conifers known as redwoods. It is native to Lichuan county in Hubei province, China. Although the least tall of the redwoods, it grows to at least 200 feet (60 meters) in height. Local villagers refer to the original tree from which most others derive as Shui-sa, or "water fir", which is part of a local shrine. Since that tree's rediscovery in 1944, the dawn redwood has become a popular ornamental.
Together with Sequoia sempervirens (coast redwood) and Sequoiadendron giganteum (giant sequoia) of California, Metasequoia is classified in the Cupressaceae subfamily Sequoioideae. Although M. glyptostroboides is the only living species in its genus, three fossil species are known, as well. Sequoioideae and several other genera have been transferred from the former Taxodiaceae family to Cupressaceae based on DNA analysis.
Metasequoia redwood fossils are known from many areas in the Northern Hemisphere; more than 20 fossil species have been named (some were even identified as the genus Sequoia), but are considered as just three species, M. foxii, M. milleri, and M. occidentalis. During the Paleocene and Eocene, extensive forests of Metasequoia occurred as far north as Strathcona Fiord on Ellesmere Island and sites on Axel Heiberg Island (northern Canada) at around 80° N latitude.Metasequoia was likely deciduous by this time. Given that the high latitudes in this period were warm and tropical, it is hypothesized that the deciduous habit evolved in response to the unusual light availability patterns, not to major seasonal variations in temperature. During three months in the summer, the sun would shine continuously, while three months of the winter would be complete darkness. It is also hypothesized that the change from evergreen to deciduous habit occurred before colonizing the high latitudes and was the reason Metasequoia was dominant in the north.
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