Aciculopoda
Encyclopedia
Aciculopoda is an extinct prawn
which existed in what is now Oklahoma
approximately . It was described in 2010 on the basis of a single fossil
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. It is only the third unambiguous fossil decapod
from before the Mesozoic
.
, Oklahoma
. The Woodford Shale is a dark-colored siliceous
shale
which outcrop
s to the north-east and the south-west of the Arbuckle Mountains
in Oklahoma. It contains "radiolarian
s, conodont
s, sponge spicule
s, ammonoid
and nautiloid
cephalopod
s, inarticulate brachiopod
s [...] and small phyllocarid
arthropod
s", and spans the Devonian
–Carboniferous
boundary. The strata
which produced Aciculopoda are thought on the basis of conodont biostratigraphy
to be from the Famennian
.
of Aciculopoda mapesi is housed at the United States National Museum as lot USNM 540766. The animal is 68.8 mm (2.7 in) long, of which the anterior 31 mm (1.2 in) is the cephalothorax
. The pleon (abdomen) is around 62 mm (2.4 in) long, along its curved dorsal margin, and about 9 mm (0.354330708661417 in) deep at its base. The cuticle
is missing from the pleon, exposing the well-preserved muscle
s beneath.
roots
("needle") and "" ("foot"), referring to the sharp spines
on the pereiopods. The specific epithet commemorates Royal Mapes, who discovered the specimen and has published widely on fossil crustaceans.
fossil older than Aciculopoda is Palaeopalaemon newberryi, found in Devonian sediments in Ohio
. (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
led Feldmann & Schweitzer to suggest that their common ancestor, the most recent common ancestor
of the Decapoda
may also have originated in the ancient continent Laurentia
.
Prawn
Prawns are decapod crustaceans of the sub-order Dendrobranchiata. There are 540 extant species, in seven families, and a fossil record extending back to the Devonian...
which existed in what is now Oklahoma
Oklahoma
Oklahoma is a state located in the South Central region of the United States of America. With an estimated 3,751,351 residents as of the 2010 census and a land area of 68,667 square miles , Oklahoma is the 28th most populous and 20th-largest state...
approximately . It was described in 2010 on the basis of a single fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
from Oklahoma
Oklahoma
Oklahoma is a state located in the South Central region of the United States of America. With an estimated 3,751,351 residents as of the 2010 census and a land area of 68,667 square miles , Oklahoma is the 28th most populous and 20th-largest state...
. 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. It is only the third unambiguous fossil decapod
Decapoda
The decapods or Decapoda are an order of crustaceans within the class Malacostraca, including many familiar groups, such as crayfish, crabs, lobsters, prawns and shrimp. Most decapods are scavengers. It is estimated that the order contains nearly 15,000 species in around 2,700 genera, with...
from before the Mesozoic
Mesozoic
The Mesozoic era is an interval of geological time from about 250 million years ago to about 65 million years ago. It is often referred to as the age of reptiles because reptiles, namely dinosaurs, were the dominant terrestrial and marine vertebrates of the time...
.
Discovery
The fossil was discovered in the Woodford Shale, exposed at the Ryan Quarry, in Pontotoc CountyPontotoc County, Oklahoma
Pontotoc County is a county located in the U.S. state of Oklahoma. As of 2000, the population was 35,143. Its county seat is Ada.-Geography:According to the U.S. Census Bureau, the county has a total area of 1,879 km²...
, Oklahoma
Oklahoma
Oklahoma is a state located in the South Central region of the United States of America. With an estimated 3,751,351 residents as of the 2010 census and a land area of 68,667 square miles , Oklahoma is the 28th most populous and 20th-largest state...
. The Woodford Shale is a dark-colored siliceous
Silicon dioxide
The chemical compound silicon dioxide, also known as silica , is an oxide of silicon with the chemical formula '. It has been known for its hardness since antiquity...
shale
Shale
Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments of other minerals, especially quartz and calcite. The ratio of clay to other minerals is variable. Shale is characterized by breaks along thin laminae or parallel layering...
which outcrop
Outcrop
An 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 superficial deposits are covered by a mantle of soil and vegetation and cannot be...
s to the north-east and the south-west of the Arbuckle Mountains
Arbuckle Mountains
The Arbuckle Mountains are an ancient mountain range in south-central Oklahoma in the United States. The granite rocks of the Arbuckles date back to the Proterozoic Era some 1.4 billion years ago which were overlain by sediments during the Paleozoic Era. The range reaches a height of 1,412 feet...
in Oklahoma. It contains "radiolarian
Radiolarian
Radiolarians are amoeboid protozoa that produce intricate mineral skeletons, typically with a central capsule dividing the cell into inner and outer portions, called endoplasm and ectoplasm. They are found as zooplankton throughout the ocean, and their skeletal remains cover large portions of the...
s, conodont
Conodont
Conodonts are extinct chordates resembling eels, classified in the class Conodonta. For many years, they were known only from tooth-like microfossils now called conodont elements, found in isolation. Knowledge about soft tissues remains relatively sparse to this day...
s, sponge spicule
Sponge spicule
Spicules are structural elements found in most sponges. They provide structural support and deter predators. Large spicules, visible to the naked eye are referred to as megascleres, while smaller, microscopic ones are termed microscleres.- Structure :...
s, ammonoid
Ammonite
Ammonite, as a zoological or paleontological term, refers to any member of the Ammonoidea an extinct subclass within the Molluscan class Cephalopoda which are more closely related to living coleoids Ammonite, as a zoological or paleontological term, refers to any member of the Ammonoidea an extinct...
and nautiloid
Nautiloid
Nautiloids are a large and diverse group of marine cephalopods belonging to the subclass Nautiloidea that began in the Late Cambrian and are represented today by the living Nautilus. Nautiloids flourished during the early Paleozoic era, where they constituted the main predatory animals, and...
cephalopod
Cephalopod
A cephalopod is any member of the molluscan class Cephalopoda . These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot...
s, inarticulate brachiopod
Brachiopod
Brachiopods are a phylum of marine animals that have hard "valves" on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, while the front can be opened for feeding or closed for protection...
s [...] and small phyllocarid
Phyllocarida
Phyllocarida is a subclass of crustaceans, comprising the extant order Leptostraca and the extinct orders Hymenostraca and Archaeostraca....
arthropod
Arthropod
An arthropod is an invertebrate animal having an exoskeleton , a segmented body, and jointed appendages. Arthropods are members of the phylum Arthropoda , and include the insects, arachnids, crustaceans, and others...
s", and spans the Devonian
Devonian
The Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, about 416.0 ± 2.8 Mya , to the beginning of the Carboniferous Period, about 359.2 ± 2.5 Mya...
–Carboniferous
Carboniferous
The Carboniferous is a geologic period and system that extends from the end of the Devonian Period, about 359.2 ± 2.5 Mya , to the beginning of the Permian Period, about 299.0 ± 0.8 Mya . The name is derived from the Latin word for coal, carbo. Carboniferous means "coal-bearing"...
boundary. The strata
Stratum
In geology and related fields, a stratum is a layer of sedimentary rock or soil with internally consistent characteristics that distinguish it from other layers...
which produced Aciculopoda are thought on the basis of conodont biostratigraphy
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. Usually the aim is correlation, demonstrating that a particular horizon in one geological section represents the same period...
to be from the Famennian
Famennian
The Famennian is one of two faunal stages in the Late Devonian epoch. It lasted from 374.5 ± 2.6 million years ago to 359.2 ± 2.5 million years ago. It was preceded by the Frasnian stage and followed by the Tournaisian stage and is named after Famenne, a natural region in southern Belgium.It was...
.
Description
The holotypeHolotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
of Aciculopoda mapesi is housed at the United States National Museum as lot USNM 540766. The animal is 68.8 mm (2.7 in) long, of which the anterior 31 mm (1.2 in) is the cephalothorax
Cephalothorax
The cephalothorax is a tagma of various arthropods, comprising the head and the thorax fused together, as distinct from the abdomen behind. The word cephalothorax is derived from the Greek words for head and thorax...
. The pleon (abdomen) is around 62 mm (2.4 in) long, along its curved dorsal margin, and about 9 mm (0.354330708661417 in) deep at its base. The cuticle
Arthropod cuticle
The cuticle forms the outer skeleton of arthropods, including insects.-Anatomy:The cuticle is made up of two layers; the epicuticle which is a thin and waxy water resistant outer layer and contains no chitin, and another layer under it called the procuticle...
is missing from the pleon, exposing the well-preserved muscle
Muscle
Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...
s beneath.
Etymology
The genus name Aciculopoda derives from the LatinLatin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
roots
Root (linguistics)
The root word is the primary lexical unit of a word, and of a word family , which carries the most significant aspects of semantic content and cannot be reduced into smaller constituents....
("needle") and "" ("foot"), referring to the sharp spines
Spine (zoology)
A spine is a hard, thorny or needle-like structure which occurs on various animals. Animals such as porcupines and sea urchins grow spines as a self-defense mechanism. Spines are often formed of keratin...
on the pereiopods. The specific epithet commemorates Royal Mapes, who discovered the specimen and has published widely on fossil crustaceans.
Interpretation
The only unambiguous decapodDecapoda
The decapods or Decapoda are an order of crustaceans within the class Malacostraca, including many familiar groups, such as crayfish, crabs, lobsters, prawns and shrimp. Most decapods are scavengers. It is estimated that the order contains nearly 15,000 species in around 2,700 genera, with...
fossil older than Aciculopoda is Palaeopalaemon newberryi, found in Devonian sediments in Ohio
Ohio
Ohio is a Midwestern state in the United States. The 34th largest state by area in the U.S.,it is the 7th‑most populous with over 11.5 million residents, containing several major American cities and seven metropolitan areas with populations of 500,000 or more.The state's capital is Columbus...
. (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
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
led Feldmann & Schweitzer to suggest that their common ancestor, the most recent common ancestor
Most recent common ancestor
In genetics, the most recent common ancestor of any set of organisms is the most recent individual from which all organisms in the group are directly descended...
of the Decapoda
Decapoda
The decapods or Decapoda are an order of crustaceans within the class Malacostraca, including many familiar groups, such as crayfish, crabs, lobsters, prawns and shrimp. Most decapods are scavengers. It is estimated that the order contains nearly 15,000 species in around 2,700 genera, with...
may also have originated in the ancient continent Laurentia
Laurentia
Laurentia is a large area of continental craton, which forms the ancient geological core of the North American continent...
.