Identifying Glossopterid Fossils Duneedoo NSW
Glossopterids are a group of Gymnosperms that characterised the Permian Age and are probably the most important plant group to have graced this planet. Not only are they the source of all our coal deposits but they are now considered to be possibly ancestral to Southern conifers, Cycadophytes and the flowering Plants (Angiosperms).
They grew as trees or woody shrubs, bearing a crown of leaves on thick trunks, in swampy conditions. Most were deciduous and their fossils are often found as layer upon layer of leaf impressions.
Glossopterid leaves: There is a range of forms with intermediaries between each, making identification difficult, but all forms have a characteristic crossconnection between veins resulting in a net pattern. Classification is made as follows: Glossopteris has a clearly defined midrib Gangamopteris has a median groove, but no midrib, and the same mesh pattern as Glossopteris Palaeovittaria has no midrib and few cross-connections between veins
Glossopterid Roots: are known as Vertebraria and look very much like an animals backbone. In cross-section they appear star shaped with rootlets radiating out from the central part.
Glossopterid Woody Tissue: is a gymnosperm wood type described as Araucarioxylon (the modern Araucaria being the Hoop and Norfolk Island Pines).
Glossopterid Reproductive Parts. There are two distinct types of female structures:
i) Megafructi - the fruits are massive, have many seeds and are borne on normal leaves. They are attached to the petiole (leaf stalk) or anywhere along the midrib, the fruits consist of a core with seeds attached and are protected by a cover-leaf. The seeds are of two types, either having a narrow wing or a large wing on one side. ii) Microfructi - seeds are attached to small modified leaves(scale leaves) and are 'also of the two types seen in the megafructi. The male reproductive parts are only known from cones and scales are called Squarnella and fertile scales called Eretmonia. They are often found in profusion with leaves. They vary in shape and form but all have characteristic striated sporangia called Arberiella. In Eretmonia there are two forking branchlets and the sporangia form dense clusters. Squamella form .catkins at the tip of small branches and the sporangia are borne on threads along the line where the scale joins the lower leaf part.