''Aciculopoda'' is an extinct

prawn Prawn is a common name for small aquatic crustaceans with an exoskeleton and ten legs (which is a member of the order decapoda), some of which can be eaten. The term "prawn"Mortenson, Philip B (2010''This is not a weasel: a close look at nature' ...

which existed in what is now Oklahoma approximately . It was described in 2010 on the basis of a single

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

from Oklahoma. The single species, ''Aciculopoda mapesi'', was named by Rodney Feldmann and Carrie Schweitzer in honour of Royal Mapes, a paleontologist who discovered the

type specimen In biology, a type is a particular specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to anchor or centralizes th ...

. It is only the third unambiguous fossil decapod from before the

Mesozoic The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Cretace ...

Discovery

The fossil was discovered in the Woodford Shale, exposed at the Ryan Quarry, in Pontotoc County, Oklahoma. The Woodford Shale is a dark-colored

siliceous Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is one ...

shale which

outcrop An outcrop or rocky outcrop is a visible exposure of bedrock or ancient superficial deposits on the surface of the Earth. Features Outcrops do not cover the majority of the Earth's land surface because in most places the bedrock or superficia ...

s to the north-east and the south-west of the Arbuckle Mountains in Oklahoma. It contains "

radiolarian The Radiolaria, also called Radiozoa, are protozoa of diameter 0.1–0.2 mm that produce intricate mineral skeletons, typically with a central capsule dividing the cell into the inner and outer portions of endoplasm and ectoplasm. The elab ...

s, conodonts,

sponge spicule Spicules are structural elements found in most sponges. The meshing of many spicules serves as the sponge's skeleton and thus it provides structural support and potentially defense against predators. Sponge spicules are made of calcium carbon ...

s, ammonoid and

nautiloid Nautiloids are a group of marine cephalopods (Mollusca) which originated in the Late Cambrian and are represented today by the living ''Nautilus'' and '' Allonautilus''. Fossil nautiloids are diverse and speciose, with over 2,500 recorded specie ...

cephalopods, inarticulate

brachiopod Brachiopods (), phylum Brachiopoda, are a phylum of trochozoan animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, w ...

s ..and small

phyllocarid Phyllocarida is a subclass of crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapoda, decapods, ostracoda, seed shrimp, branchiopoda, branchiopods, argulidae, fish lice, krill, remipe ...

arthropod Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and cuticle made of chiti ...

s", and spans the Devonian– Carboniferous boundary. The strata which produced ''Aciculopoda'' are thought on the basis of conodont

biostratigraphy Biostratigraphy is the branch of stratigraphy which focuses on correlating and assigning relative ages of rock strata by using the fossil assemblages contained within them.Hine, Robert. “Biostratigraphy.” ''Oxford Reference: Dictionary of B ...

to be from the

Famennian The Famennian is the latter of two faunal stages in the Late Devonian Epoch. The most recent estimate for its duration estimates that it lasted from around 371.1 million years ago to 359.3 million years ago. An earlier 2012 estimate, still used b ...

Description

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 ...

of ''Aciculopoda mapesi'' is housed at the

United States National Museum The Smithsonian Institution ( ), or simply the Smithsonian, is a group of museums and education and research centers, the largest such complex in the world, created by the U.S. government "for the increase and diffusion of knowledge". Founded ...

as lot USNM 540766. The animal is long, of which the anterior is the cephalothorax. The pleon (abdomen) is around long, along its curved dorsal margin, and about deep at its base. The cuticle is missing from the pleon, exposing the well-preserved muscles beneath.

Etymology

The genus name ''Aciculopoda'' is said to be derived from the

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

' ("needle") and "'" ("foot"), referring to the sharp spines on the pereiopods. ''Pes'' is however used for "foot" in classical and botanical Latin,.Lewis, C.T. & Short, C. (1879). ''A Latin dictionary founded on Andrews' edition of Freund's Latin dictionary.'' Oxford: Clarendon Press.Stearn, W.T. (1983). ''Botanical Latin. History, grammar, syntax, terminology and vocabulary.'' (3rd edition). Newton Abbot London: David Charles. while in ancient Greek, ''pous'' (πούς) is used.Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon. Revised and augmented throughout by Sir Henry Stuart Jones with the assistance of Roderick McKenzie.''Oxford: Clarendon Press. The specific epithet commemorates Royal Mapes, who discovered the specimen and has published widely on fossil crustaceans.

Interpretation

The only unambiguous decapod fossil older than ''Aciculopoda'' is '' Palaeopalaemon newberryi'', found in Devonian sediments in

Ohio Ohio () is a state in the Midwestern region of the United States. Of the fifty U.S. states, it is the 34th-largest by area, and with a population of nearly 11.8 million, is the seventh-most populous and tenth-most densely populated. The sta ...

. (The assignment of '' Imocaris'' to the Decapoda is the subject of some debate.) The fact that both ''Aciculopoda'' and ''Palaeopalaemon'' were discovered in the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...

led Feldmann & Schweitzer to suggest that their common ancestor, the

most recent common ancestor In biology and genetic genealogy, the most recent common ancestor (MRCA), also known as the last common ancestor (LCA) or concestor, of a set of organisms is the most recent individual from which all the organisms of the set are descended. The ...

of the Decapoda may also have originated in the ancient continent

Laurentia Laurentia or the North American Craton is a large continental craton that forms the ancient geological core of North America. Many times in its past, Laurentia has been a separate continent, as it is now in the form of North America, althoug ...

References

{{Taxonbar, from=Q4674029 Dendrobranchiata Devonian crustaceans Fossil taxa described in 2010 Pontotoc County, Oklahoma Monotypic crustacean genera