''Avitelmessus grapsoideus'' is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

species of

crab Crabs are decapod crustaceans of the infraorder Brachyura (meaning "short tailed" in Greek language, Greek), which typically have a very short projecting tail-like abdomen#Arthropoda, abdomen, usually hidden entirely under the Thorax (arthropo ...

from the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...

Peedee Formation The Peedee Formation is a Formation (geology), geologic formation in North Carolina, North and South Carolina. A marine deposit representing an inner Neritic zone, neritic environment, named for exposures along the Great Peedee River, it preserve ...

and

Ripley Formation The Ripley Formation is a geological formation in North America found in the U.S. states of Alabama, Georgia, Mississippi, Missouri, and Tennessee. The lithology is consistent throughout the layer. It consists mainly of glauconitic sandstone. It ...

of the United States.Rathbun, M. J. (1923). "Decapod Crustaceans from the Upper Cretaceous of North Carolina." ''North Carolina Geological Survey'', vol. 5., pp. 403-408. The type species is ''A. grapsoideus''.

Taxonomic history

''Avitelmessus'' was described in 1923 by Mary J. Rathbun, who assigned it to the family Atelecyclidae. Martin Glaessner reassigned it to the family Dakoticancridae in 1960.

Description

The

shell Shell may refer to: Architecture and design * Shell (structure), a thin structure ** Concrete shell, a thin shell of concrete, usually with no interior columns or exterior buttresses Science Biology * Seashell, a hard outer layer of a marine ani ...

of ''Avitelmessus'' was about in length and was nearly ovular in shape, with a "rounded outline". The upper surface was marked by "broad, shallow grooves" which formed two attached diamond-like shapes, with the larger one closer to the front. "Subsidiary" grooves came in contact with both sides of the larger diamond. The "fairly blunt" anterior edge of the

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 ...

possessed a small, central

rostrum Rostrum may refer to: * Any kind of a platform for a speaker: **dais **pulpit ** podium * Rostrum (anatomy), a beak, or anatomical structure resembling a beak, as in the mouthparts of many sucking insects * Rostrum (ship), a form of bow on naval ...

, with

orbits In celestial mechanics, an orbit (also known as orbital revolution) is the curved trajectory of an physical body, object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an satellite, artificia ...

on either side. The front legs were modified to become chelipeds, with pincers formed by an upper finger, which was movable, and a lower finger, which was stationary (an extension of the previous leg segment). All limbs were covered by "fine granules". At least one specimen with "color markings" (considered rare among fossil crabs) has been discovered. The colors are described as "a medium background, dark spots and blotches, and light lines".

Fossil sites

''Avitelmessus'' was originally described by Rathbun based on the

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

from the

of North Carolina, as well as specimens from the

of Mississippi. Later, she would also describe specimens from western Tennessee. ''Avitelmessus'' is also present on the

Atlantic coastal plain The Atlantic Ocean is the second largest of the world's five borders of the oceans, oceanic divisions, with an area of about . It covers approximately 17% of Earth#Surface, Earth's surface and about 24% of its water surface area. During the ...

and in the

Mississippi Embayment The Mississippi embayment is a physiographic feature in the south-central United States, part of the Mississippi Alluvial Plain. It is essentially a northward continuation of the fluvial sediments of the Mississippi River Delta to its conflu ...

. The "near restriction" of ''Avitelmessus'' to the Mississippi embayment (and that of other Dakoticancridae members to other specific areas) suggest " provincialism" among the family.

References

{{Taxonbar, from=Q4829002 Dromiacea Cretaceous arthropods of North America Late Cretaceous crustaceans Late Cretaceous animals of North America Fossil taxa described in 1923 Cretaceous North Carolina Cretaceous Mississippi Cretaceous Tennessee Fossils of North Carolina Fossils of Mississippi Fossils of Tennessee Maastrichtian genera