Hannah Stott
Article Summary
Due April 3rd
Evelyn Galvez
Seed Ferns Survived the End-Cretaceous Mass Extinction in Tasmania
Published by: Stephen McLoughlin, Raymond J. Carpenter, Gregory J. Jordan, and
Robert S. Hill.
The Mesozoic seed ferns include: Peltaspermales, Caytoniales,
Corystospermales, Bennettitales, Pentozylales and several other extinct
gymnosperms. Seed ferns are important because they constitute a great amount of
fauna and they are a very diverse species. They originally thought that the seed ferns
went extinct with the photosynthesis crisis and climate changes that were produced
after the Earth was hit by an asteroid at Chixculub, Mexico. They found leaf fossils in
Tasmania that dated back to the youngest seed fern remains ever found. This helped
them to show what they refer to as a “ghost lineage” that links the Tasmanian species
to the next younger fossils.
The materials and methods used for the research for this article were the fossil
site, the fossil preparation and very specific descriptions of the fossils themselves.
The fossil site was at the Macquiarie Harbor Formation located near Strahan,
Tasmania. The fossil preparation included ten incomplete compound leaves. The
description included very detailed descriptions of the compound leaf fossils.
They discuss in great detail the affinities of the leaf fossils so the reader can
understand how they found what they were looking for. They discuss how the fossils
can easily be distinguished from conifers, ginkgoaleans, gnetaleans and angiosperms
because of their pinnate architecture and lanceolate pinnules with divergent,
dichotomous, open venation. In other words, their pinnules have very different,
divided and open veins on the leaves. Even with the detailed examinations they had
of the fossils it was still difficult to tell them apart because they were missing pieces of
the fossils. The foliage characteristics of the new Tasmanian fossils conform to those
of the seed fern Komlopteris Barbacka. The most striking are the variably lobed
pinnules with evanescent midveins and softly branching secondary veins. They were
able to use the longitudinal furrow between the two veins to diagnose the new species.
Through careful study and tedious examinations of the leaf fossils, they were
able to prove that the seed ferns did in fact survive the end-Cretaceous extinction.
The gymnosperm diversity remained relatively stable in Australia through the
Cretaceous. However, the diversity did change somewhat and the abundance was
significantly reduced. With more research and determination, there may be a
possibility of finding yet another 'ghost lineage'. If they are able to discover another
“ghost lineage” then they may be able to discover other seeds that were able to
survive the mass extinction.