''Schramidontus'' is a genus of crustaceans from the Late

Devonian The Devonian ( ) is a period (geology), geologic period and system (stratigraphy), system of the Paleozoic era (geology), era during the Phanerozoic eon (geology), eon, spanning 60.3 million years from the end of the preceding Silurian per ...

period found in Strud,

Belgium Belgium, officially the Kingdom of Belgium, is a country in Northwestern Europe. Situated in a coastal lowland region known as the Low Countries, it is bordered by the Netherlands to the north, Germany to the east, Luxembourg to the southeas ...

, closely related to '' Angustidontus'' and classified as part of the order

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

. It is an important genus because of its position in the

eumalacostraca Eumalacostraca is a subclass of crustaceans, containing almost all living malacostracans, or about 40,000 described species. The remaining subclasses are the Phyllocarida and possibly the Hoplocarida. Eumalacostracans have 19 segments (5 cephalic ...

n family tree and the insight study of the genus may give of the origin of the

Decapoda The Decapoda or decapods, from Ancient Greek δεκάς (''dekás''), meaning "ten", and πούς (''poús''), meaning "foot", is a large order of crustaceans within the class Malacostraca, and includes crabs, lobsters, crayfish, shrimp, a ...

. The generic name derives from

Frederick Schram Frederick Robert Schram (born August 11, 1943, in Chicago, Illinois) is an American palaeontologist and carcinologist. He received his B.S. in biology from Loyola University Chicago in 1965, and a Ph.D. on palaeozoology from the University of ...

, 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 Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

is from Labas, a stream that flows near Strud quarry, where the genus was discovered.

Description

''Schramidontus'' had a subcylindrical smooth

carapace A carapace is a dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tortoises, the unde ...

and a triangular

telson The telson () is the hindmost division of the body of an arthropod. Depending on the definition, the telson is either considered to be the final segment (biology), segment of the arthropod body, or an additional division that is not a true segm ...

. 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 In vertebrates, the maxilla (: maxillae ) is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The two maxillar ...

, maxillulae and its large

mandibles In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone i ...

. 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

pereiopod The anatomy of a decapod consists of 20 body segments grouped into two main body parts: the cephalothorax and the pleon (abdomen). Each segment – often called a somite – may possess one pair of appendages, although in various groups these m ...

s. The first five were subchelated, short and ending in a hooked

dactylus The dactylus is the tip region of the tentacular club of cephalopods and of the leg of some crustaceans (see arthropod leg). In cephalopods, the dactylus is narrow and often characterized by the asymmetrical placement of suckers (i.e., the vent ...

, and the last pair was shorter and narrower with a small simple dactylus.

Classification

''Schramidontus'' is classified as part of the extinct family

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

together with the pelagic genus '' Angustidontus'' from

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

and

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

. This family is the only family classified as part of the eucarid order

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

due to their

being fused to thoracic segments 1-7. The cladogram below is based on the relationships of the Eucarida assumed by Gueriau, Charbonnier and Clément (2014), based on the gradual modification of the first

thoracopod The arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments (called podomeres) are of Latin origin, and may be confused with terms for bones: ''coxa'' (meaning hip (a ...

s into the maxillipeds seen in the

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

tetrapod A tetrapod (; from Ancient Greek :wiktionary:τετρα-#Ancient Greek, τετρα- ''(tetra-)'' 'four' and :wiktionary:πούς#Ancient Greek, πούς ''(poús)'' 'foot') is any four-Limb (anatomy), limbed vertebrate animal of the clade Tetr ...

s and a fauna of well-preserved freshwater

crustacean Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquatic arthrop ...

s, including

decapods The Decapoda or decapods, from Ancient Greek δεκάς (''dekás''), meaning "ten", and πούς (''poús''), meaning "foot", is a large order (biology), order of crustaceans within the class Malacostraca, and includes crabs, lobsters, crayfis ...

conchostracan Clam shrimp are a group of bivalved branchiopod crustaceans that resemble the unrelated Bivalvia, bivalved molluscs. They are extant and also known from the fossil record, from at least the Devonian period and perhaps before. They were originally ...

s, notostracans and

anostracan Anostraca is one of the four orders of crustaceans in the class Branchiopoda; its members are referred to as fairy shrimp. They live in vernal pools and hypersaline lakes across the world, and they have even been found in deserts, ice-covered mou ...

s. 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. The first two pairs

s are inserted laterally in the mouth. Several factors such as the size and articulation of the three

endopod The arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments (called podomeres) are of Latin origin, and may be confused with terms for bones: ''coxa'' (meaning hip, : ...

al 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

maxilliped An appendage (or outgrowth) is an external body part or natural prolongation that protrudes from an organism's body such as an arm or a leg. Protrusions from single-celled bacteria and archaea are known as cell-surface appendages or surface app ...

References

{{Taxonbar, from=Q48971561 Prehistoric crustacean genera Prehistoric Malacostraca Devonian arthropods of Europe Devonian crustaceans Fossil taxa described in 2014 Fossils of Belgium