Cupressaceae
Fossil Record
Fossil Record
The Cupressaceae have the largest number of extant species of conifers. Both Cupressaceae and Taxodiaceae first appeared in the Mesozoic, which began two hundred forty five million years ago and lasted until sixty five million years ago. The first species of Cupressaceae appeared in the late Triassic (245-215 million years ago). Cupressaceae was widespread throughout the world and was found on all of the Gondwanan continents. The Cupressaceae genus experienced extensive diversification in the Cenozoic, especially in the Tertiary. After the Triassic, two subfamilies emerged: the Cuppressoideae in the northern hemisphere and the Callitroideae in the southern hemisphere. Taxodiaceae came into being in the mid Jurassic (215-150 million years ago). By the Cretaceous (150-65 million years ago), all modern species of Taxodiaceae had evolved. However, there are numerous fossil examples of Taxodiaceae, but relatively few extant species.
The oldest cone bearing fossil of the combined groups of Cupressaceae is Phyllostrobus Lorteti. This fossil is from the Kimmeridge of Orbagnoux. It is from the Jurassic era, which is rare because there are very few fossils from this period. Phyllostrobus Lorteti was identified by its abundance of leafy branches. It was also identified for its decussate arrangement and characteristic position of leaves.
Glyptostrobus is another typical example of a Cupressaceae genus fossil. This is one of the most frequently recorded conifers of Tertiary flora. The fossil remains are generally pieces of foliage shoots. The distribution of this species followed a rather typical pattern for a Cupressaceae and Taxodiaceae species. In the Tertiary, this plant ranged over the northern hemisphere. It remained in Europe, up until the Pliocene, which was in the mid-Cenozoic. However, in modern times, Glyptostrobus has been confined to China.
Cupressinostrobus is a species that is known from its very specific fossils. It first appeared in the upper Cretaceous in Massachusetts. The fossils are mainly of ovulate cones up to 3.5 centimeters long. The ovulate cones had bract-scale complexes arranged opposite to each other. There are 14 to 24 pairs of these complexes. Each bract-scale complex produces two seeds. This species is also know for its several wood types. These wood types were in the form genera of Widdringtonoxylon, Thujoxylon, and Libocedroxylon.
Another species with an extensive fossil record is Fokienia. There are remains of this species found from the Paleocene of Canada. The remains are in the form of both vegetative and reproductive parts. The fossil plant has branches on either side of a common stem. These branches have scale-like leaves. The reproductive parts are seed cones, which are only about six millimeters long. These seed cones are borne in opposite pairs. The cone is made up of eight to ten woody, peltate cone scales. It is interesting to note that the reproductive morphology of the fossil and extant plants is quite similar. However, the vegetative morphology is extremely different between the fossil and extant species. This could be due to two different courses of evolution. It is possible that the vegetative morphology was quite diverse in the past, yet only one form has survived due to some ecological condition. On the other hand, it is equally likely that the vegetative part of the plant evolved throughout the Tertiary, while the reproductive organs did not change much. Now, the extant species of Fokienia is endemic to southeast Asia.
Taxodium is one species, whose fossil record also displays the distribution of other Cupressaceae species. This species is more commonly known as the Bald Cypress. It appeared in the late Jurassic and existed throughout North America, Europe, Asia and Arctic regions. This genera was often found at the edges of freshwater lakes and lagoons, which were bordered by marshes. However, it is now restricted to only the southeastern United States. Here, it is found in swamps and other wet, marshy areas. It was common in the forests of Central Europe where it became available as materials which form Miocene brown coal.
The species of sequoias (except for Metasequoia ) is also interesting for its very specific and unique distribution. The sequoias (including Metasequoia ) were recorded from a few examples from the Jurassic. Yet, they became more prominent in the Cretaceous period. There are abundant remains of sequoias. These remains have been found in Alaska, Chile, Japan, Manchuria, and Europe. In contrast, sequoias are now restricted to a narrow strip of land in California and Oregon, which borders the Pacific Ocean. There are two extant species of sequoias left. These are Sequoiadendron giganteum and Sequoia sempervirens. The extant species are extremely similar to the fossil remains that have been found of Sequoias.
A very interesting Cupressaceae species is the Metasequoia. This plant is rather unique because it has the distinction of being the only species that was described from fossil remains, before living specimens of the species were found in modern times. This species appeared in the Jurassic, and became prominent in the Cretaceous. The fossil record of Metasequoia was in the form of mostly vegetative remains and cones. These remains were found in clays and lignite beds from the Pliocene. This species has deciduous, scattered leafy shoots that are in opposite pairs on branches. The needles are twisted and grow opposite from one another. The pollen and seed cone scales are decussately arranged, which means that they are arranged along the stem in pairs, with each pair at a right angle to the next pair. In 1944, T. Wang found specimens of Metasequoia in central China. This is the only place that this species is found growing naturally. However, evidence of this species has been found throughout North America during the Cretaceous and Tertiary eras.
Arthrotaxites is one plant that appeared in the Cretaceous of Montana and Canada. The species, Arthrotaxites berryi, is based on impressions and compressions. It is known that the plant has small, scale-like leaves, which are about two millimeters long. This species does share features with modern taxa. Many other Cretaceous Cupressaceae genera share their morphological features with modern taxa. This suggests that extensive radiation was taking place in the family during the early Cretaceous.
H. Solms-Laubach. 1891. Fossil Botany. Clarendon Press, Oxford.
T.N. & E.L. Taylor. 1993. The Biology and Evolution of Fossil Plants. Prentice Hall, New Jersey.
