Caught between two mass extinctions: The rise and fall of Dicroidium

Chris Mays and Stephen McLoughlin (Sweden) In the aftermath of Earth’s greatest biotic crisis 251.9 million years ago – the end-Permian mass extinction – a group of plants arose that would come to dominate the flora of the Southern Hemisphere. Recovery of the vegetation from the end-Permian crisis was slow; but steadily, one group of seed plants, typified by the leaf fossil Dicroidium, began to diversify and fill the dominant canopy-plant niches left vacant by the demise of the Permian glossopterid forests (Fielding et al., 2019). Eventually, Dicroidium re-established a rich peat-forming vegetation across Gondwana through the Late Triassic, dominating the flora between 30°S and the South Pole (Kustatscher et al., 2018). Indeed, few fossil plant assemblages of this age can be found in Gondwana that do not contain this plant. The importance of Dicroidium is not just its role in showing biogeographic and tectonic linkages between southern lands or its value in determining the age of continental strata. Dicroidium and its associated plant groups were so successful that they were major contributors to the development of thick coal seams in the Late Triassic that are now mined to produce electricity. Although Dicroidium is generally envisaged as a plant of cool temperate climates, the very first fossils that might belong to this group are from the Permian-Triassic transition of Jordan, located near the palaeoequator (Blomenkemper et al., 2018). Nevertheless, the distribution of Dicroidium soon shifted to high southern latitudes in the Early Triassic and they overwhelmingly dominated the southern vegetation … Read More

To access this post, you must purchase Annual subscription, 12 Month Subscription or Monthly subscription.

Invertebrate fossils from the Lower Muschelkalk (Triassic, Anisian) of Winterswijk, The Netherlands

Henk Oosterink (The Netherlands) During the Muschelkalk part of the Ansian (240mya), the Central European area (Germany, Poland, Denmark, The Netherlands and north-eastern France) was covered by a shallow sea, referred to as the Muschelkalk Sea. While there were frequent regressions and transgressions (leading to both marine and terrestrial fossil being present in these regions), it is from this sea that the limestones from this quarry were deposited and in which most of the fossilised animals discussed in this article lived. The quarry in the Muschelkalk at Winterswijk, in the east of the Netherlands (Fig. 1), is especially well known for the skeletons, bones, footprints and tracks of Middle Triassic reptiles. I wrote about these in Issues 15 and 20 of Deposits. However, fossils of invertebrates, such as molluscs, brachiopods and arthropods can also be found. Included in the molluscs are bivalves, cephalopods and gastropods, and from the brachiopods, the Inarticulata are present. From the arthropods, there are Malacostraca, Merostomata and insects. Fig. 1. Lower Muschelkalk quarry near Winterswijk (Eastern Netherlands). Mollusca Bivalves Some strata contain a large number of moulds of bivalves. These are situated quite high in the profile and, if you find this level, it is important to split the rock along an irregular dark-grey line (Fig. 2). If you do this, you will find the moulds of the convex upper side of the separated shells on one slab, with the negative impression visible on the other. This makes clear that these are valves swept together by … Read More

To access this post, you must purchase Annual subscription, 12 Month Subscription or Monthly subscription.

Fossil insects from the Lower Cretaceous of southern England

Dr James E Jepson (UK) It was over 150 years ago that the first major work began on the fossil insects of the Lower Cretaceous of England. The pioneers were Victorian naturalists, including the Rev Osmond Fisher, John O Westwood and, in particular, the Rev Peter Bellinger Brodie. 1845 saw the publication of Brodie’s A History of the Fossil Insects in the Secondary Rocks of England, the earliest English language book on fossil insects and the first major study of the fossil insects of England. The Victorians collected and described many species from Wiltshire, Dorset and the Weald, and started the ball rolling for British palaeoentomology. The twentieth century saw little activity in British Cretaceous palaeoentomology. At this time, there was a shift towards the Palaeozoic insects from the Carboniferous, with Herbert Bolton leading the way – Bolton’s major work was published in a monograph on British Carboniferous insects in 1921–1922. A few descriptions were made on British Cretaceous insects in the early twentieth century, most notably Anton Handlirsch’s monograph of fossil insects (1906–1908) included some British Cretaceous insects; but there was no major studies completed. However, in the late twentieth century, interest in the Cretaceous insects of Britain was reawakened by Edmund A Jarzembowski, with his studies on Wealden insects and later the Purbeck insects with Robert A Coram. Into the twenty-first century, Jarzembowski and Coram have remained a driving force for the study of Lower Cretaceous insects of southern England and, through their work and their collaborations with … Read More

To access this post, you must purchase Annual subscription, 12 Month Subscription or Monthly subscription.