Arthropleuridea
Encyclopedia
Arthropleuridea was a subclass of myriapod arthropod
s that flourished during the Carboniferous
period, having first arose during the Silurian
, and perishing due to climate change during the Early Permian
. Members are defined by diplosomy, paranotal tergal lobes separated from the axis by a suture, and by sclerotized
plates buttressing the leg insertions. Despite their unique features, recent phylogenetic
research suggests that Arthropleuridea may be included among millipede
s. The class contains three recognized orders, each with a single genus. Arthropleurids had about 30 pairs of legs, whose tracks have been found in the Joggins deposit in Nova Scotia, Canada.
Arthropleuridea is most famous for order Arthropleurida. With the genus Arthropleura
over 2 meters in length, arthropleurids are among the largest arthropod
s ever to have lived. The lack of large terrestrial vertebrate predators and the highly oxygen
ic atmosphere at that time probably enabled them to grow so large. Arthropleurids lived in the moist coal
swamps that were common at the time and may have burrow
ed in the undergrowth. They were either herbivore
s or detritivore
s. Besides their size, their most distinguishing features were their legs with eight segments (as many as 30 pairs) and extremely tough exoskeleton
s. There is no evidence of spiracle
s, so the animals must have used lung
s or gill
s for respiration
. Arthropleurids became extinct
as the climate became drier and the coal swamps dried out.
Tracks
from Arthropleura up to 50 cm wide have been found at Joggins, Nova Scotia
.
Most arthropleurids are thought to have been terrestrial, although, without any known respiratory structure, terrestriality is assumed only by analogy to modern arthropods. Early forms, however, including order Eoarthropleurida, appear to have been aquatic
. For this reason, some question Arthropleuridea's inclusion among millipedes because no modern aquatic myriapods
are known. Eoarthropleurida has been found from the Upper Silurian through the Upper Devonian
of Europe
and North America
.
Order Microdecemplicida was smaller in comparison to the other arthropleurids, with genus Microdecemplex just a few millimeters long. It is known from the Middle through Upper Devonian of New York
state.
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 that flourished during the 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"...
period, having first arose during the Silurian
Silurian
The Silurian is a geologic period and system that extends from the end of the Ordovician Period, about 443.7 ± 1.5 Mya , to the beginning of the Devonian Period, about 416.0 ± 2.8 Mya . As with other geologic periods, the rock beds that define the period's start and end are well identified, but the...
, and perishing due to climate change during the Early Permian
Permian
The PermianThe term "Permian" was introduced into geology in 1841 by Sir Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian...
. Members are defined by diplosomy, paranotal tergal lobes separated from the axis by a suture, and by sclerotized
Sclerosis (medicine)
In medicine, sclerosis refers to the stiffening of a structure, usually caused by a replacement of the normal organ-specific tissue with connective tissue.Types include:...
plates buttressing the leg insertions. Despite their unique features, recent phylogenetic
Phylogenetics
In biology, phylogenetics is the study of evolutionary relatedness among groups of organisms , which is discovered through molecular sequencing data and morphological data matrices...
research suggests that Arthropleuridea may be included among millipede
Millipede
Millipedes are arthropods that have two pairs of legs per segment . Each segment that has two pairs of legs is a result of two single segments fused together as one...
s. The class contains three recognized orders, each with a single genus. Arthropleurids had about 30 pairs of legs, whose tracks have been found in the Joggins deposit in Nova Scotia, Canada.
Arthropleuridea is most famous for order Arthropleurida. With the genus Arthropleura
Arthropleura
Arthropleura was a 0.3–2.6 metre long relative of centipedes and millipedes, native to the Upper Carboniferous of what is now northeastern North America and Scotland...
over 2 meters in length, arthropleurids are among the largest 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 ever to have lived. The lack of large terrestrial vertebrate predators and the highly oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
ic atmosphere at that time probably enabled them to grow so large. Arthropleurids lived in the moist coal
Coal
Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...
swamps that were common at the time and may have burrow
Burrow
A burrow is a hole or tunnel dug into the ground by an animal to create a space suitable for habitation, temporary refuge, or as a byproduct of locomotion. Burrows provide a form of shelter against predation and exposure to the elements, so the burrowing way of life is quite popular among the...
ed in the undergrowth. They were either herbivore
Herbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...
s or detritivore
Detritivore
Detritivores, also known as detritophages or detritus feeders or detritus eaters or saprophages, are heterotrophs that obtain nutrients by consuming detritus . By doing so, they contribute to decomposition and the nutrient cycles...
s. Besides their size, their most distinguishing features were their legs with eight segments (as many as 30 pairs) and extremely tough exoskeleton
Exoskeleton
An exoskeleton is the external skeleton that supports and protects an animal's body, in contrast to the internal skeleton of, for example, a human. In popular usage, some of the larger kinds of exoskeletons are known as "shells". Examples of exoskeleton animals include insects such as grasshoppers...
s. There is no evidence of spiracle
Spiracle
Spiracles are openings on the surface of some animals that usually lead to respiratory systems.-Vertebrates:The spiracle is a small hole behind each eye that opens to the mouth in some fishes. In the primitive jawless fish the first gill opening immediately behind the mouth is essentially similar...
s, so the animals must have used lung
Lung
The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...
s or gill
Gill
A gill is a respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water, afterward excreting carbon dioxide. The gills of some species such as hermit crabs have adapted to allow respiration on land provided they are kept moist...
s for respiration
Aquatic respiration
Aquatic respiration is the process whereby an aquatic animal obtains oxygen from water.-Fish:In most fish respiration takes place through gills. Lungfish, however, possess one or two lungs...
. Arthropleurids became extinct
Extinction
In biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...
as the climate became drier and the coal swamps dried out.
Tracks
Trace fossil
Trace fossils, also called ichnofossils , are geological records of biological activity. Trace fossils may be impressions made on the substrate by an organism: for example, burrows, borings , urolites , footprints and feeding marks, and root cavities...
from Arthropleura up to 50 cm wide have been found at Joggins, Nova Scotia
Joggins, Nova Scotia
Joggins is a Canadian rural community located in western Cumberland County, Nova Scotia. On July 7, 2008 a 15 km length of the coast constituting the Joggins Fossil Cliffs was officially inscribed on the World Heritage List.- History :...
.
Most arthropleurids are thought to have been terrestrial, although, without any known respiratory structure, terrestriality is assumed only by analogy to modern arthropods. Early forms, however, including order Eoarthropleurida, appear to have been aquatic
Aquatic animal
An aquatic animal is an animal, either vertebrate or invertebrate, which lives in water for most or all of its life. It may breathe air or extract its oxygen from that dissolved in water through specialised organs called gills, or directly through its skin. Natural environments and the animals that...
. For this reason, some question Arthropleuridea's inclusion among millipedes because no modern aquatic myriapods
Myriapoda
Myriapoda is a subphylum of arthropods containing millipedes, centipedes, and others. The group contains 13,000 species, all of which are terrestrial...
are known. Eoarthropleurida has been found from the Upper Silurian through the Upper 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...
of Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
and North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
.
Order Microdecemplicida was smaller in comparison to the other arthropleurids, with genus Microdecemplex just a few millimeters long. It is known from the Middle through Upper Devonian of New York
New York
New York is a state in the Northeastern region of the United States. It is the nation's third most populous state. New York is bordered by New Jersey and Pennsylvania to the south, and by Connecticut, Massachusetts and Vermont to the east...
state.