''Microdictyon'' is an extinct armoured

worm Worms are many different distantly related bilateral animals that typically have a long cylindrical tube-like body, no limbs, and no eyes (though not always). Worms vary in size from microscopic to over in length for marine polychaete worm ...

-like animal coated with net-like scleritic plates, known from the Early

Cambrian The Cambrian Period ( ; sometimes symbolized Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million years ag ...

Maotianshan shale of Yunnan China and other parts of the world. ''Microdictyon'' is part of the ill-defined

taxon In biology, a taxon ( back-formation from '' taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular n ...

–

Lobopodia The lobopodians, members of the informal group Lobopodia (from the Greek, meaning "blunt feet"), or the formally erected phylum Lobopoda Cavalier-Smith (1998), are panarthropods with stubby legs called lobopods, a term which may also be used as ...

– that includes several other odd worm-like

animal Animals are multicellular, eukaryotic organisms in the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic material, Cellular respiration#Aerobic respiration, breathe oxygen, are Motilit ...

s that resembling worm with legs, such as ''

Hallucigenia ''Hallucigenia'' is a genus of Cambrian animal resembling worms, known from articulated fossils in Burgess Shale-type deposits in Canada and China, and from isolated spines around the world. The generic name reflects the type species' unusual ...

'', '' Onychodictyon'', ''

Cardiodictyon ''Cardiodictyon'' is a genus of lobopodian The lobopodians, members of the informal group Lobopodia (from the Greek language, Greek, meaning "blunt feet"), or the formally erected phylum Lobopoda Cavalier-Smith (1998), are panarthropods with ...

'', '' Luolishania'', and ''

Paucipodia ''Paucipodia inermis'' is a lobopod The lobopodians, members of the informal group Lobopodia (from the Greek, meaning "blunt feet"), or the formally erected phylum Lobopoda Cavalier-Smith (1998), are panarthropods with stubby legs called lobo ...

''. The isolated sclerites of ''Microdictyon'' are known from other Lower

deposits. ''Microdictyon'' sclerites appear to have

moulted 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 ...

; one sclerite seems to have been preserved during ecdysis.Figured in ''Microdictyon sinicum'' (Chen, Hou and Lu, 1989) is typical. The wormlike animal has ten pairs of

sclerite A sclerite ( Greek , ', meaning " hard") is a hardened body part. In various branches of biology the term is applied to various structures, but not as a rule to vertebrate anatomical features such as bones and teeth. Instead it refers most commonl ...

s (suggestions that these may be eyes or eye-like structures have no weight) on the sides, matched to a pair of

tentacle In zoology, a tentacle is a flexible, mobile, and elongated organ present in some species of animals, most of them invertebrates. In animal anatomy, tentacles usually occur in one or more pairs. Anatomically, the tentacles of animals work main ...

-like feet below. The head and posterior are tubular and featureless.

Species composition

Type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen( ...

. ''Microdictyon effusum'' Bengtson, Matthews et Missarzhevsky, 1981; Lower Cambrian, Atdabanian Stage,

Kazakhstan Kazakhstan, officially the Republic of Kazakhstan, is a transcontinental country located mainly in Central Asia and partly in Eastern Europe. It borders Russia Russia (, , ), or the Russian Federation, is a transcontinental coun ...

;

Atdabanian Cambrian Stage 3 is the still unnamed third stage of the Cambrian. It succeeds Cambrian Stage 2 and precedes Cambrian Stage 4, although neither its base nor top have been formally defined. The plan is for its lower boundary to correspond approxi ...

and Botomian Stages,

Russia Russia (, , ), or the Russian Federation, is a transcontinental country spanning Eastern Europe and Northern Asia. It is the largest country in the world, with its internationally recognised territory covering , and encompassing one-eigh ...

( Siberian Platform) and England; Lower Cambrian, Sweden. In addition to the type species, 13 species: *''M. anus'' Tong, 1989, Lower Cambrian, upper Meishucunian Stage (= Atdabanian Stage), China ( Shaanxi). *''M. chinense'' Hao et Shu, 1987, Lower Cambrian, Qiongzhusi Stage (= upper Atdabanian-lowermost Botomian Stages), China (Shaanxi); Atdabanian through Botomian stages, Siberian Platform. *''M. cuneum'' Wotte et Sundberg, 2017, Lower Cambrian, Montezuman Stage, 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 U.S. state, states, a Washington, D.C., federal district, five ma ...

. *''M. depressum'' Bengtson, 1990, Lower Cambrian, Atdabanian through Botomian Stages, South Australia. *''M. fuchengense'' Li et Zhu, 2001, Lower Cambrian, upper Meishucunian Stage (Atdabanian Stage), China (Shaanxi). *''M. jinshaense'' Zhang et Aldridge, 2007, Lower Cambrian, Qiongzhusi Stage (= upper Atdabanian Stage-lowermost Botomian), China(Shaanxi). *''M. montezumaensis'' Wotte et Sundberg, 2017, Lower Cambrian, Montezuman Stage, the United States. *''M. rhomboidale'' Bengtson, Matthews et Missarzhevsky, 1986, Lower Cambrian, upper parts of the Atdabanian Stage, Kazakhstan; Atdabanian Stage,

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tota ...

, the United States (''M. cf. rhomboidale''). *''M. robisoni'' Bengtson, Matthews et Missarzhevsky, 1986, Middle Cambrian, Amgan Stage, the United States; *''M. rozanovi'' Demidenko, 2006, Lower Cambrian,

Toyonian Cambrian Stage 4 is the still unnamed fourth stage of the Cambrian and the upper stage of Cambrian Series 2. It follows Cambrian Stage 3 and lies below the Wuliuan. The lower boundary has not been formally defined by the International Commissi ...

Stage, Siberian Platform. *''M. sinicum'' Chen, Hou et Lu, 1989, Lower Cambrian, upper Meishucunian Stage (= Atdabanian Stage) Stage, China (

Yunnan Yunnan , () is a landlocked province in the southwest of the People's Republic of China. The province spans approximately and has a population of 48.3 million (as of 2018). The capital of the province is Kunming. The province borders the ...

. *''M. sphaeroides'' Hinz, 1987, Lower Cambrian, Atdabanian Stage, Great Britain. *''M. tenuiporatum'' Bengtson, Matthews et Missarzhevsky, 1986, Lower Cambrian, Atdabanian Stage, Siberian Platform. A picture can be found at https://web.archive.org/web/20030730043530/http://paws.wcu.edu/dperlmutr/earlyfauna.html. ---- The name ''Microdictyon'' is also used for a genus of green

algae Algae ( , ; : alga ) are any of a large and diverse group of photosynthetic, eukaryotic organisms. The name is an informal term for a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from ...

References

{{taxonbar, from1=Q20818056 Prehistoric protostome genera Maotianshan shales fossils Burgess Shale animals Paleozoic life of New Brunswick Paleozoic life of Nova Scotia Cambrian genus extinctions