Euthycarcinoid
Encyclopedia
Euthycarcinoida is a group of amphibious
Amphibious
Amphibious means able to use either land or water. In particular it may refer to:*Amphibious warfare, warfare carried out on both land and water*Amphibians, vertebrate animals of the Class Amphibia...

 freshwater arthropod
Arthropod
An arthropod is an invertebrate animal having an exoskeleton , a segmented body, and jointed appendages. Arthropods are members of the phylum Arthropoda , and include the insects, arachnids, crustaceans, and others...

s that until recently were only known from the Carboniferous
Carboniferous
The Carboniferous is a geologic period and system that extends from the end of the Devonian Period, about 359.2 ± 2.5 Mya , to the beginning of the Permian Period, about 299.0 ± 0.8 Mya . The name is derived from the Latin word for coal, carbo. Carboniferous means "coal-bearing"...

 onwards. A single Ordovician/Silurian individual was identified in the Tumblagooda sandstone
Tumblagooda sandstone
The Tumblagooda sandstone is a geological formation deposited during the Silurian or Ordovician periods, around four to five hundred million years ago, and is now exposed on the west coast of Australia, straddling the boundary of the Carnarvon and Perth basins...

 in 1993; a Devonian example was added from the Rhynie chert
Rhynie chert
The Rhynie chert is an Early Devonian sedimentary deposit exhibiting extraordinary fossil detail or completeness . It is exposed near the village of Rhynie, Aberdeenshire, Scotland; a second unit, the Windyfield chert, is located some 700 m away...

 in 2003, and most recently a specimen has been found from the Cambrian. The organisms may have produced some varieties of Protichnites
Protichnites
Protichnites is a genus of trace fossil consisting of the imprints made by the walking activity of arthropods. It is likely that more than one type of arthropod was responsible for these tracks. Euthycarcinoids, aglaspidids and eurypterids are possible contributors. Protichnites consists of two...

, the earliest arthropod trackways
Fossil trackway
A fossil trackway is a type of trace fossil, a trackway made by an organism. Many fossil trackways were made by dinosaurs, early tetrapods, and other quadrupeds and bipeds on land...

 on land.

By the latest phylogenies, the organisms represent stem-group myriapods.
The organisms appear to have become extinct in the Triassic mass extinction.
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