Tempskya Temporal range: Cretaceous | |
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Tempskya fossil slab and reconstruction on display | |
Scientific classification | |
Kingdom: | Plantae |
Clade: | Tracheophytes |
Division: | Polypodiophyta |
Class: | Polypodiopsida |
Subclass: | Polypodiidae |
Order: | incertae sedis |
Family: | † Tempskyaceae Read et Brown ex L.C.A. Martínez |
Genus: | † Tempskya Corda 1845 [1] |
Tempskya is an extinct genus of tree fern that lived during the Cretaceous period. Fossils have been found across both the Northern and Southern hemispheres. [2] The growth habit of Tempskaya was unlike that of any living fern or any other living plant, consisting of multiple conjoined dichotomous branching stems enmeshed within roots that formed a "false trunk". [3]
The trunk of Tempskya was actually a large collection of stems surrounded by adventitious roots. [4] The false trunks can reach up to 6 metres (20 ft) in height and up to 50 centimetres (20 in) in diameter. [5] Small leaves grew from various points across the height of the trunk. This is in contrast to most tree ferns, where typically large leaves grow from the top of the trunk. [5] Thin leaves have been discovered for the first time on Tempskya wyomingense specimens; [1] the more commonly seen fossilized leaf bases show that they covered the upper part of the trunk. [4]
Examination of cross sections of various Tempskya specimens shows that those with the largest trunks have the smallest number of stems, and vice versa. [6] From this, a possible growth pattern of Tempskya has been suggested: at the sporeling stage, Tempskya would consist of a single stem, which would begin to branch off distally. A "mantle" of adventitious roots would then develop around the stems to support them. Later on, many of the stems would begin to decay, while the adventitious roots would still provide support and absorb water for the grown plant. [6] This growth pattern has also been hypothesized for Psaronius . [6]
Tempskya is thought to have grown in lowland environments close to water, like wetlands and riverbanks. [3]
The first fossils of Tempskya was originally described in 1824 as the Endogenites erosa by Stokes and Webb, who considered it to be a palm tree. The genus Tempskya was named by August Carl Joseph Corda in 1845, from specimens found in what is now the Czech Republic. [1] The four species originally described by Corda were, in order: Tempskya pulchra, Tempskya macrocaula, Tempskya microrrhiza, and Tempskya schimperi. [7]
Tempskya is the sole member of the family Tempskyaceae. [4] The family has been placed in the order "Filicales", [6] which is now split into a number of orders of leptosporangiate ferns. They have been suggested to members of Cyatheales, based on morphological similarities of the petiole and spores to some members of that order. [3]
Most taxonomists divide Tempskya species into two groups, those with a simple cortex with only a parenchymatous inner cortex without sclerenchyma, while other species have an inner cortex with either discontinuous or continuous layers of sclerenchyma. [5]
Tempskya finds were thought to be exclusive to the Northern Hemisphere until specimens were discovered in Argentina and Australia, in 2003 and 2005, respectively. Tempskya fossils have also been discovered in the Czech Republic ,2002 and Japan ,1986. [2] Tempskya were frequently found fluvial deposited in gravel pits in Germany. Its origin is not clear, in part they came certainly from Czech sites
The tree ferns are arborescent (tree-like) ferns that grow with a trunk elevating the fronds above ground level, making them trees. Many extant tree ferns are members of the order Cyatheales, to which belong the families Cyatheaceae, Dicksoniaceae, Metaxyaceae, and Cibotiaceae. It is estimated that Cyatheales originated in the early Jurassic, and is the third group of ferns known to have given rise to tree-like forms. The others are the extinct Tempskya of uncertain position, and Osmundales where the extinct Guaireaceae and some members of Osmundaceae also grew into trees. In addition there were the Psaroniaceae and Tietea in the Marattiales, which is the sister group to most living ferns including Cyatheales.
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