A wedge-shaped leaf – Ginkgophytopsis delvalii

In the collection of the former Munich paleobotanist Max Hirmer (1893–1981), which is now integrated into the holdings of the Bavarian State Collection of Palaeontology and Geology (BSPG), there are several impression fossils of large, inverted wedge-shaped leaves with fine venation from the Upper Carboniferous (c. 300 million years ago) of the Ruhr area in Germany. 

These leaves belong to the enigmatic Palaeophyllales, which include various inverted wedge-shaped foliage types that – in contrast to most Paleozoic foliage types – are not composed of pinnules and leaflets. From the Devonian, Carboniferous and Permian of Europe, Asia, and North America, a large number of such leaves – some only a few cm in size, others more than 40 cm long – have been described and given such nice-sounding generic names as Eddya, Enigmophyton, Platyphyllum, Psygmophyllum, Ginkgophyton or Ginkgophytopsis. To this day, little is known about the plants that produced these leaves. The leaves are almost always found detached, and in only one or two cases has it been possible to demonstrate what branches, stems, and/or reproductive organs belonged to them.

The specimens on display were originally described under the name Psygmophyllum delvalii, but later renamed Ginkgophytopsis delvalii. Ginkgophytopsis means “plant that looks like a ginkgo”. However, this does not mean that these leaves actually come from a ginkgo relative. Some have assumed that they are the fronds of small ferns or leaf-like outgrowths at the base of large fern fronds (so-called aphlebia), while others have classified them as seed ferns (pteridosperms). The cordaites, precursors of the conifers, have also been discussed as possible relatives, as they also produced large leaves. Finally, some have considered Ginkgophytopsis to be an early representative of the ginkgoes (Ginkgophyta), as the fossils resemble geologically younger fossil ginkgo leaves, as well as the leaves of today’s ginkgo tree (Ginkgo biloba).

Ginkgophytopsis delvalii leaves are generally rare as fossils. From the middle Westphalian A of the Ruhr area, however, several layers have become known which are almost completely covered with these leaves; such finds are referred to as local mass occurrences. The specimens on display come from a mass occurrence unearthed in 1932 in the coal mine ‘Constantin der Große’ in Bochum.