Search the Community
Showing results for tags 'donetsk'.
-
To start I quote some brief information from the Wiki about pteridosperms. The term Pteridospermatophyta (or "seed ferns") refers to several distinct groups of extinct seed-bearing plants. The oldest fossil evidence of plants of this type is of late Devonian age, and they flourished particularly during the Carboniferous and Permian periods. Pteridosperms declined during the Mesozoic Era and had mostly disappeared by the end of the Cretaceous Period. Nowadays, four orders of Palaeozoic seed plants tend to be referred to as pteridosperms: Medullosales, Lyginopteridales, Callistophytales and Peltaspermales. I have the specimens for first two ones only. So, go ahead. First group Medullosales - Neuropteris, Alethopteris, Odontopteris, Reticulopteris, Cyclopteris. Most medullosaleans were small to medium sized trees. The largest were probably the trees with Alethopteris fronds - these fronds could be at least 7 metres long and the trees were perhaps up to 10 metres tall. Especially in Moscovian times, many medullosaleans were rather smaller trees with fronds only about 2 metres long, and apparently growing in dense, mutually supporting stands. During Kasimovian and Gzhelian times there were also non-arboreal forms with smaller fronds (e.g. Odontopteris) that were probably scrambling or possibly climbing plants. Neuropteris and Cyclopteris Alethopteris Odontopteris Reticulopteris Second group Lyginopteridales - includ Lyginopteris, Eusphenopteris, Diplothmema, Palmatopteris, Karinopteris, Mariopteris. In most cases the amount of secondary wood was limited suggesting they were stems of scrambling or climbing plants. The stele is surrounded by a zone of cortex, which in many genera contains bands of fibrous tissue. This fibrous tissue often results in distinctive markings on the surface of the stems even when preserved as adpressions and can help with their generic identification: Lyginopteris for instance shows a mesh-shaped patterning on the surface of the stems. Mariopteris
- 9 comments
-
- pteridosperm
- Donetsk
-
(and 1 more)
Tagged with: