''Avitelmessus grapsoideus'' is an extinct species of crab that lived during the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger 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 ''creta'', ...

. It is the only species in the genus ''Avitelmessus'' and is known from finds in the southeastern United States.

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 ** Thin-shell structure Science Biology * Seashell, a hard o ...

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 possessed a small, central

rostrum Rostrum may refer to: * Any kind of a platform for a speaker: **dais **pulpit * 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 ships * Ros ...

, with

orbits In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such as a p ...

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 grapsoideus fossil, Tellus Science Museum

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

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of sever ...

from the

Peedee Formation The Peedee Formation is a geologic formation in North and South Carolina. A marine deposit, named for exposures along the Great Peedee River, it preserves belemnites and foraminifera fossils dating from the Late Cretaceous The Late Cretaceous ...

of North Carolina, as well as specimens from the

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. I ...

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

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

provincialism Parochialism is the state of mind, whereby one focuses on small sections of an issue rather than considering its wider context. More generally, it consists of being narrow in scope. In that respect, it is a synonym of " provincialism". It may, p ...

" 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