Schramidontus

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Schramidontus
Temporal range: Famennian, 358.9–372.2  Ma
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Schramidontus

Gueriau, Charbonnier & Clément, 2014
Type species
Schramidontus labensis
Gueriau, Charbonnier & Clément, 2014

Schramidontus is a genus of crustaceans from the Late Devonian period found in Strud, Belgium, closely related to Angustidontus and classified as part of the order Angustidontida. It is an important genus because of its position in the eumalacostracan family tree and the insight study of the genus may give of the origin of the Decapoda. The generic name derives from Frederick Schram, who helped the scientific community in the field of the Palaeozoic malacostracans and the suffix -idontus in relation to the similarities between Schramidontus and Angustidontus. The specific name is from Labas, a stream that flows near Strud quarry, where the genus was discovered. [1]

Contents

Description

Schramidontus had a subcylindrical smooth carapace and a triangular telson. It had two pairs of grasping maxillipeds, the second being twice as big as the first, that it could use to bring prey to the maxillae, maxillulae and its large mandibles. This feature was not present in its only close relative, Angustidontus, which probably used its maxillipeds to hit and hold its prey. In addition, Schramidontus had six pairs of pereiopods. The first five were subchelated, short and ending in a hooked dactylus, and the last pair was shorter and narrower with a small simple dactylus. [1]

Classification

Schramidontus is classified as part of the extinct family Angustidontidae together with the pelagic genus Angustidontus from Europe and North America. This family is the only family classified as part of the eucarid order Angustidontida. Angustidontids are diagnosed as eucarids that possess carapaces and stalked eyes with "scale-like exopods" on the second antennae, an elongated pleion and a tail fan. These features make the group distinct from most eumalacostracan crustaceans and they are classified as part of the Eucarida due to their carapace being fused to thoracic segments 1-7. [1]

The cladogram below is based on the relationships of the Eucarida assumed by Gueriau, Charbonnier and Clément (2014), [1] based on the gradual modification of the first thoracopods into the maxillipeds seen in the Decapoda.

Eucarida

Euphausiacea

Amphionidacea

Angustidontida

Angustidontus

Schramidontus

Decapoda

Paleoecology

The small quarry of Strud in which Schramidontus was found has no evidence of marine influence, but it suggests a continental environment. In these deposits fossil remains have been found of several animals such as tetrapods and a fauna of well-preserved freshwater crustaceans, including decapods, conchostracans, notostracans and anostracans. There is also evidence of fossil remains of plants such as early seed-plants. The Belgian angustidontids can be recognized as early continental eumalacostracans, probably freshwater. Schramidontus was found in a continental environment, and although this represents the first documentation of continental angustidontids, it differs from the marine environment in which Angustidontus is usually found. [1]

The first two pairs thoracopods are inserted laterally in the mouth. Several factors such as the size and articulation of the three endopodal articles suggest that these thoracopods were able to bring prey to the maxillae, maxillulae and its large mandibles. In addition, the spiny occlusal margins of their dactyli suggest that the genus was fed by filtration. Therefore, these thoracopods are considered to be maxillipeds. [1]

Related Research Articles

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Malacostraca Largest class of crustaceans

Malacostraca is the largest of the six classes of crustaceans, containing about 40,000 living species, divided among 16 orders. Its members, the malacostracans, display a great diversity of body forms and include crabs, lobsters, crayfish, shrimp, krill, woodlice, amphipods, mantis shrimp and many other, less familiar animals. They are abundant in all marine environments and have colonised freshwater and terrestrial habitats. They are segmented animals, united by a common body plan comprising 20 body segments, and divided into a head, thorax, and abdomen.

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Squat lobster

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Eucarida Superorder of crustaceans

Eucarida is a superorder of the Malacostraca, a class of the crustacean subphylum, comprising the decapods, krill, Amphionides and Angustidontida. They are characterised by having the carapace fused to all thoracic segments, and by the possession of stalked eyes.

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Cumacea Order of crustacean

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Arthropod mouthparts

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Cherax parvus is a species of crayfish in the family Parastacidae. It is only known from its type locality – the Upper Tully River catchment in the Cardwell Range of north-eastern Queensland – and is listed as data deficient on the IUCN Red List. It was discovered in a rainforest catchment in a highland of northeastern Queensland during a Queensland Museum expedition to the upper Tully River area in November 1992. It is one of the smallest species in the genus. No species of Cherax has been considered endemic to wet upland or highland areas before it was discovered; most previous records were from elevations less than 400 meters. It also has several morphological features unique to the genus, and does not appear closely related to any extant species, suggesting a long period of geographic isolation.

<i>Angustidontus</i> Extinct genus of crustaceans

Angustidontus is a genus of predatory pelagic crustaceans from the Late Devonian and Early Carboniferous periods, classified as part of the subclass Eumalacostraca. Fossils of the genus have been recovered in relative abundance from Canada, Germany, the Czech Republic, Poland, Belarus, Ukraine and large parts of the United States, including Oklahoma, Ohio, Indiana, Kentucky, Montana, Utah, Nevada.

<i>Scyllarides latus</i>

Scyllarides latus, the Mediterranean slipper lobster, is a species of slipper lobster found in the Mediterranean Sea and in the eastern Atlantic Ocean. It is edible and highly regarded as food, but is now rare over much of its range due to overfishing. Adults may grow to 1 foot (30 cm) long, are camouflaged, and have no claws. They are nocturnal, emerging from caves and other shelters during the night to feed on molluscs. As well as being eaten by humans, S. latus is also preyed upon by a variety of bony fish. Its closest relative is S. herklotsii, which occurs off the Atlantic coast of West Africa; other species of Scyllarides occur in the western Atlantic Ocean and the Indo-Pacific. The larvae and young animals are largely unknown.

<i>Neoglyphea</i> Genus of crustaceans

Neoglyphea inopinata is a species of glypheoid lobster, a group thought long extinct before Neoglyphea was discovered. It is a lobster-like animal, up to around 15 centimetres (5.9 in) in length, although without claws. It is only known from 17 specimens, caught at two sites – one at the entrance to Manila Bay in the Philippines, and one in the Timor Sea, north of Australia. Due to the small number of specimens available, little is known about the species, but it appears to live up to five years, with a short larval phase. A second species, previously included in Neoglyphea, is now placed in a separate genus, Laurentaeglyphea.

Hexapoda Subphylum of arthropods

The subphylum Hexapoda constitutes the most species of arthropods and includes the insects as well as three much smaller groups of wingless arthropods: Collembola, Protura, and Diplura. The Collembola are very abundant in terrestrial environments. Hexapods are named for their most distinctive feature: a consolidated thorax with three pairs of legs. Most other arthropods have more than three pairs of legs.

Alpheus tricolor is a crustacean belonging to the family of snapping shrimp. It was first isolated in Indonesia and Sri Lanka. It counts with a setose carapace, an acute rostrum, shallow adrostral furrows and a basicerite with a strong ventrolateral tooth. The lamella of its scaphocerite is not reduced, with an anterior margin that is concave. Its third maxilliped counts with an epipodial plate bearing thick setae, while its first chelipeds are found with their merus bearing a strong disto-mesial tooth; its third pereiopod has an armed ischium, with a simple and conical dactylus. Its telson is broad, distally tapering, with 2 pairs of dorsal spines. The species is named after its characteristic colour pattern, including white, red and orange.

<i>Alpheus fasqueli</i> Species of crustacean

Alpheus fasqueli is a crustacean belonging to the family of snapping shrimp. It was first isolated in Sri Lanka. It counts with a setose carapace, an acute and carinate rostrum, and unarmed orbital hoods. Its basicerite has a strong ventrolateral tooth. The lamella of its scaphocerite is not reduced. Its third maxilliped counts with an epipodial plate bearing thick setae, while its first chelipeds are found with their merus bearing a strong disto-mesial tooth; its third pereiopod has an armed ischium, with a simple and conical dactylus. Its telson is broad, distally tapering, with 2 pairs of dorsal spines. The species is named after Frédéric Fasquel, a photographer who contributed rare shrimp specimens for the Muséum national d'histoire naturelle.

Tokummia katalepsis is a fossil arthropod from the Burgess Shale as found in a quarry in Marble Canyon in Canada. It is an early member of Mandibulata. The fossil is 508 million years old. The animal has maxillipeds, mandibles, ring-shaped body segments, and subdivided basipods. At the front of the animal are mandibles with pincers. This is the oldest fossil with pincers. The speculation is that T. katalepsis grabbed soft bodied prey with the mandibles and them chopped them into pieces so that it could eat. It has more than 50 pairs of legs. The animal is about 10 cm long and has a two piece carapace on its back. It was a bottom feeder, being able to walk on the sea floor, and to occasionally swim. The animal legs have endites which are small spikes on the legs. It has one pair of antennae.

Angustidontidae Extinct family of crustaceans

Angustidontidae is an extinct family of eucarid crustaceans and the sole representatives of the order Angustidontida. They were predators ranging in size from about 4 to 9 centimetres in length and lived during the Late Devonian and Early Carboniferous periods.

References

  1. 1 2 3 4 5 6 Gueriau, Pierre; Charbonnier, Sylvain; Clément, Gaël (2014-09-01). "Angustidontid crustaceans from the Late Devonian of Strud (Namur Province, Belgium): Insights into the origin of Decapoda". Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen. 273. doi:10.1127/0077-7749/2014/0434.