''Arthropleura'' () is a genus of extinct

millipede Millipedes are a group of arthropods that are characterised by having two pairs of jointed legs on most body segments; they are known scientifically as the class Diplopoda, the name derived from this feature. Each double-legged segment is a resu ...

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 that lived in what is now

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and th ...

and

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

around 345 to 290

million years ago The abbreviation Myr, "million years", is a unit of a quantity of (i.e. ) years, or 31.556926 teraseconds. Usage Myr (million years) is in common use in fields such as Earth science and cosmology. Myr is also used with Mya (million years ago ...

, from the

Viséan The Visean, Viséan or Visian is an age in the ICS geologic timescale or a stage in the stratigraphic column. It is the second stage of the Mississippian, the lower subsystem of the Carboniferous. The Visean lasted from to Ma. It follow ...

stage of the lower

Carboniferous Period The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carbonif ...

to the Sakmarian stage of the lower Permian Period. The species of the genus are the largest known land

invertebrate Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chorda ...

s of all time, and would have had few, if any, predators.

Morphology

File:20211224 Arthropleura armata anterior.png, Anterior morphology of ''A. armata'' File:20211225 Arthropleura leg associated structures.png, Leg and associated structures File:Millipede anterior anatomy.png, Modern millipede anatomy for comparison File:20211226 Largest Arthropleura.png, Size estimation of the largest specimen ''A. armata'' grew to be long. Tracks from ''Arthropleura'' up to wide have been found at

Joggins, Nova Scotia Joggins is a rural community located in western Cumberland County, Nova Scotia, Canada. On July 7, 2008 a 15-km length of the coast constituting the Joggins Fossil Cliffs was officially inscribed on the World Heritage List. In 2021 a fossil was reported, probably a shed

exoskeleton An exoskeleton (from Greek ''éxō'' "outer" and ''skeletós'' "skeleton") is an external skeleton that supports and protects an animal's body, in contrast to an internal skeleton ( endoskeleton) in for example, a human. In usage, some of the ...

(

exuviae In biology, exuviae are the remains of an exoskeleton and related structures that are left after ecdysozoans (including insects, crustaceans and arachnids) have moulted. The exuviae of an animal can be important to biologists as they can often b ...

) of an ''Arthropleura'' with an estimated width of , length of to and body mass of . ''Arthropleura'' was able to grow larger than modern arthropods, partly because of the greater

partial pressure In a mixture of gases, each constituent gas has a partial pressure which is the notional pressure of that constituent gas as if it alone occupied the entire volume of the original mixture at the same temperature. The total pressure of an ideal g ...

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements ...

Earth's atmosphere The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing fo ...

at that time and partly because of the lack of large terrestrial

vertebrate Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, with ...

predator Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill t ...

s. ''Arthropleura'' is characterized by a series of well-developed tergites (dorsal

) having three lobes like a

trilobite Trilobites (; meaning "three lobes") are extinct marine arthropods that form the class Trilobita. Trilobites form one of the earliest-known groups of arthropods. The first appearance of trilobites in the fossil record defines the base of the ...

, with dorsal surfaces covered by many tubercles. The head is almost unknown, as the anterior oval plate in front of the first trilobate tergite, which previous thought to be head shield, were considered to be a collum (first tergite of millipede trunk) by subsequent studies. Based on the discovery from other arthropleurids ('' Microdecemplex''), the head may have had non-filamentous antennae and trumpet-like organs. It is estimated that ''Arthropleura'' had a trilobate tergite number ranging from 28 to 32. The alignment between leg and tergite is not well understood, but at least it is believed to have been diplopodous in some degree: two pairs of legs per tergite, like modern millipede. Alongside the median

sternite The sternum (pl. "sterna") is the ventral portion of a segment of an arthropod thorax or abdomen. In insects, the sterna are usually single, large sclerites, and external. However, they can sometimes be divided in two or more, in which case th ...

, there were three pairs of ventral plates located around each leg pair, namely K-, B- and rosette plates, and either the B- or K-plates were thought to be respiratory organs. The body terminated with a trapezoidal

telson The telson () is the posterior-most division of the body of an arthropod. Depending on the definition, the telson is either considered to be the final segment of the arthropod body, or an additional division that is not a true segment on acco ...

Paleobiology

Fossil Footprints Arthropleura - geograph

All found fossils of ''Arthropleura'' are believed to be

(

molting In biology, moulting (British English), or molting (American English), also known as sloughing, shedding, or in many invertebrates, ecdysis, is the manner in which an animal routinely casts off a part of its body (often, but not always, an outer ...

shells) instead of carcasses. The good preservation of its thin exuviae, buttressing plates around the leg base, and evidence of 3 cm deep trackway fossils (namely the

ichnotaxon An ichnotaxon (plural ichnotaxa) is "a taxon based on the fossilized work of an organism", i.e. the non-human equivalent of an artifact. ''Ichnotaxa'' comes from the Greek ίχνος, ''ichnos'' meaning ''track'' and ταξις, ''taxis'' meaning ...

'' Diplichnites cuithensis'') altogether suggests that they had a sturdy

and roamed the land. ''Arthropleura'' was once thought to have lived mainly in coal forests. However, it probably lived a forest-independent life, as fossils of the trackway were found in more open areas and fossils were found even after the Carboniferous rainforest collapse. There is no solid evidence for the diet of ''Arthropleura'', as the fossils that were once considered coprolites, including lycopod fragments and

pteridophyte A pteridophyte is a vascular plant (with xylem and phloem) that disperses spores. Because pteridophytes produce neither flowers nor seeds, they are sometimes referred to as " cryptogams", meaning that their means of reproduction is hidden. Fer ...

spores In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, ...

, are later considered to be merely coexistence of plant fossils and exuvia remains. Nonetheless, the interpretation of a

herbivorous A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpar ...

diet is still accepted, and it is estimated that ''Arthropleura'' may have eaten not only spores but also sporophylls and

seeds A seed is an embryonic plant enclosed in a protective outer covering, along with a food reserve. The formation of the seed is a part of the process of reproduction in seed plants, the spermatophytes, including the gymnosperm and angiosperm ...

, based on its enormous size that possibly required lots of nutrition.

Extinction

Previously, the extinction of ''Arthropleura'' was attributed to the decrease of coal forest. However, many fossils have been discovered even after the Carboniferous rainforest collapse, and it is estimated that ''Arthropleura'' itself lived a forest-independent life. A more recent proposal is that the diversification of

tetrapods Tetrapods (; ) are four-limbed vertebrate animals constituting the superclass Tetrapoda (). It includes extant and extinct amphibians, sauropsids (reptiles, including dinosaurs and therefore birds) and synapsids ( pelycosaurs, extinct therapsi ...

and the desiccation of the

equator The equator is a circle of latitude, about in circumference, that divides Earth into the Northern and Southern hemispheres. It is an imaginary line located at 0 degrees latitude, halfway between the North and South poles. The term can also ...

caused it to become extinct.

References

External links

* {{Taxonbar, from=Q131789 Mississippian first appearances Carboniferous arthropods of Europe Carboniferous arthropods of North America Pennsylvanian extinctions Fossil taxa described in 1854 Carboniferous myriapods Carboniferous Scotland Fossils of Great Britain Fossils of Scotland Fossils of Canada

Morphology

Paleobiology

Extinction

See also

References

External links