Name: The Gilboa Formation
Location: New York State, USA
Age: Devonian - 380 Million Years Old
The fauna of Gilboa comprises of early arthropods,
including the oldest known spider Attercopus fimbriunguis,
parts of which were originally described as a trigonotarbid, possibly
of the genus Gelasinotarbus. Attercopus is placed
as sister-taxon to all living spiders, on the basis of characters
of the spinneret and the arrangement of the patellatibia
joint of the walking legs. A cladogram of the relationships of
all pulmonate arachnids and pictures of the fragmentory material
can be viewed in the paper by Shear et al. (1991). Palaeontology
34, part 2, 241-281.
A pulmonate arachnid Ecchosis pulchribothrium, related to Araneae and Amblypygi, has also been described from the Gilboa formation by the same authors.
Fossils from Gilboa include:
Chilopoda : centipedes. Chilopoda are arthropods whose bodies are made up of a chain of up to 177 flattened segments. Each segment has a single pair of legs, with the exception of the two most posterior segments and the first anterior segment directly behind the head.. The appendages of the first body segment have been modified to form large, poisonous fangs that are used to capture prey.
Mites : Acari are the most diverse and abundant of all arachnids, Many mites have complex symbiotic associations with the larger organisms on which they live and help to regulate microbial processes directly by feeding on detritus and microbes, and indirectly by predation on other microfauna.
Pseudoscorpions : Pseudoscorpions are tiny scorpion-like creatures with large pincerlike claws, but no long tail and stinger. Pseudoscorpions are between 1/16 to 1/8 inch (2 to 8 mm) long, flat-bodied arachnids with a short, usually oval abdomen consisiting of roughly 11 or 12 segmentes rounded posteriorly.
Scorpions : Scorpions
are venomous arthropods of the class Arachnida and are considered
relatives of the spiders, mites, ticks and harvestmen. As with
arachnids, scorpions have mouthparts called chelicerae, a pair
of large pincers, and four pairs of legs. The abdomen consists
of 12 distinct segments, with the last five forming the tail.
At the end of the abdomen is the telson, which bears a bulb-shaped
structure containing the venom glands and a sharp, curved aculeus
(sting) to deliver the venom.
Trigonotarbids : Trigonotarbids
are an extinct group of arachnid arthropods that resemble the
modern spider. Both have eight legs and a pair of pedipalps but
trigonotarbids lack the silk-producing spinnerets and also have
strongly segmented abdomen and don't exhibit the constriction
that spiders have between the abdomen and cephalothorax.
Arthropleurids : Arthropleurids
such as Eoarthropleura and probable archaeognathoan insects.
Gilboa is famous for its fossil gymnosperm forest. These trees are thought to belong to a group of plants called the progymnosperms, which were large ferns with a woody stem structure that preceded the evolvution of seed cone reproducing evergreen trees. They also lacked true roots with the base of the trunk resembling a fungus structure. It is hypothesised that the apex of the trees may have had fern structures in the form of large fronds instead of individual leaves, but there is no evidence of this in the fossils themselves. Unlike the gymnosperms however, they did not produce seeds, but rather released their spores as do ferns. Some progymnosperms were homosporous, producing two different kinds of spores.
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