Tempskya is an extinctgenus 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 Tempskya 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]
Description
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 fossilizedleaf bases show that they covered the upper part of the trunk.[4]
Hypothesized growth pattern
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]
Ecology
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]
Species
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]
^ abcdTaylor, Thomas N.; Taylor, Edith L.; Krings, Michael (2009). "Ferns and Early Fernlike Plants". Paleobotany : the biology and evolution of fossil plants (2nd ed.). Amsterdam: Academic Press. pp. 457–459. ISBN978-0-12-373972-8. Retrieved 24 January 2012.
^Stephenson, Lloyd William (1936). "American Cretaceous Ferns of the Genus Tempskya". New Upper Cretaceous Ostreidae From the Gulf Region. Washington: United States Government Printing Office. p. 108. Retrieved 25 January 2012.
