Tag: Jason A. Dunlop

Jason has been interested in arachnids since childhood — receiving a pet tarantula for his 16th birthday. He studied zoology in the Department of Pure and Applied Biology at the University of Leeds (1988–91), and followed this with a PhD in the Department of Earth Sciences at the University of Manchester (1991–94). This had the title “Palaeobiology of the trigonotarbid arachnids”, an extinct arachnid group, and was carried out under the supervision of Dr Paul Selden. He remained in Manchester for a further three years (1994–97) on a NERC postdoctoral research fellowship entitled “Origins and early radiation of the chelicerates”. Since 1997 he has been curator of arachnids, myriapods and stem-group arthropods at the Museum for Naturkunde in Berlin, Germany. His principal research interests remain the use of fossil arachnids for answering larger evolutionary questions, as well as the comparative morphology of living and extinct arachnids and their relatives. Together with co-workers, he has compiled a regularly updated list of all known fossil arachnids described in the literature. He is currently Secretary of the International Society of Arachnology, Vice-President of the European Society of Arachnology and a handling editor for papers on terrestrial arthropods submitted to the journal Palaeontology.

Contact Details:

Dr. Jason A. Dunlop, Museum für Naturkunde, Leibniz Institute for Research on Evolution and Biodiversity at the Humboldt University Berlin, 10115 Berlin, Germany.

Fossil Focus: Xiphosura

Fossil Focus
by Jason A. Dunlop*1 Introduction: The Xiphosura are commonly known as horseshoe crabs because the front part of their bodies is horseshoe-shaped. They have sometimes been called king crabs, although this name is also used for a group of large true crabs. Despite their various common names, xiphosurans are not crustaceans. Older studies assumed that they were some sort of crab, mostly because they have gills and live in the sea, but careful anatomical studies towards the end of the nineteenth century showed that they are actually more closely related to arachnids. The name Xiphosura means ‘sword tail’ and refers to another obvious feature of these animals: a long, pointed tail spine. Horseshoe crabs — especially earlier fossil ones — also look quite a lot like trilobites. This has led to

Fossil Focus: Arachnida

Fossil Focus
by Jason A. Dunlop*1 Introduction: Arachnida is one of the major arthropod groups. It includes spiders (Araneae), scorpions (Scorpiones), mites (Acari) and harvestmen (Opiliones), as well as a number of rarer and less familiar groups (Fig 1). The name Arachnida was introduced by the French zoologist Jean-Baptise Lamarck and is derived from Greek mythology: in one story, the maiden Arachne challenged the goddess Athene to a weaving contest, and was subsequently transformed into a spider — condemned to weave for evermore. There are about 100,000 living species of arachnids, with mites and spiders representing the most diverse and species-rich groups. Fossil arachnids are considerably rarer, with more than 1,700 described species (well over half of which are spiders) and a record that exten

Fossil Focus: Chasmataspidida

Fossil Focus
by Jason A. Dunlop*1 Introduction: Chasmataspidida (Fig 1) are rare, extinct arthropods known only from the early to mid Palaeozoic Era. They are probably closely related to either xiphosurans (horseshoe crabs; Fig 2) or eurypterids (sea scorpions; Fig 1); some chasmataspid fossils were originally misinterpreted as members of one of these two groups. They were first discovered in the 1950s, and were only recently recognized as a group distinct from horseshoe crabs. Chasmataspids are currently the oldest known examples of the Euchelicerata lineage —all Chelicerata except Pycnogonida (sea spiders) — and palaeontologists date the origins of these euchelicerates back to at least the late Cambrian Period. Morphology: Most chasmataspids are a few centimetres long. The body is divided int

Fossil Focus: Pycnogonida

Fossil Focus
by Jason A. Dunlop*1 Introduction: Pycnogonida, or sea spiders, are not true spiders at all. They are in fact a group of — probably rather primitive — marine arthropods, characterized by a small, slender body and in many cases by correspondingly long legs (Fig. 1). So unusual is their morphology that many of their internal-organ systems have been displaced into the legs. Because of their strange appearance, older studies occasionally referred to them as ‘nobody crabs’ (literally crabs without a body) — although it is important to stress that they are not crustaceans, any more than they are spiders. Pycnogonids are thought either to have evolved right at the very base of the arthropod tree — and thus not to be closely related to any particular group of arthropods — or to be related to ara

Fossil Focus: Chelicerata

Fossil Focus
by Jason A. Dunlop*1 Introduction: Chelicerata is one of the main divisions of the arthropods, and essentially consists of arachnids and their closest relatives. The name was coined in 1901 by the Berlin-based zoologist Richard Heymons (Fig. 1). It means the ‘claw-bearers’, in reference to the claw- or fang-shaped mouthparts that characterize the group. In addition to the arachnids, Chelicerata also includes the horseshoe crabs (Xiphosura), the extinct sea scorpions (Eurypterida) and little-known chasmatapaids (Chasmataspidida), and the sea spiders (Pycnogonida). The inclusion of sea spiders within this group is controversial, as we shall see below, and arachnids, horseshoe crabs, eurypterids and chasmataspids are sometimes grouped together as the Euchelicerata. The name Merostoma