Microbrachiidae is an extinct

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

of tiny, advanced

antiarch Antiarchi ("opposite anus") is an order of heavily armored placoderms. The antiarchs form the second-most successful group of placoderms after the arthrodires in terms of numbers of species and range of environments. The order's name was coi ...

placoderms closely related to the bothriolepidids. Although most species are known from Late Emsian-aged strata of Early Devonian China, the

type Type may refer to: Science and technology Computing * Typing, producing text via a keyboard, typewriter, etc. * Data type, collection of values used for computations. * File type * TYPE (DOS command), a command to display contents of a file. * Ty ...

and youngest species, ''

Microbrachius ''Microbrachius'' is an extinct genus of tiny, advanced antiarch placoderms closely related to the bothriolepids. Complete articulated specimens show that the armored section of the body had an average length of 2-4 cm. Species of ''Microbrach ...

dicki'', is known from upper Givetian freshwater strata of

Scotland Scotland (, ) is a country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a border with England to the southeast and is otherwise surrounded by the Atlantic Ocean to the ...

and

Estonia Estonia, formally the Republic of Estonia, is a country by the Baltic Sea in Northern Europe. It is bordered to the north by the Gulf of Finland across from Finland, to the west by the sea across from Sweden, to the south by Latvia, a ...

. When ''Microbrachius'' was regarded as an Antiarch '' incertae sedis'', the other genera were thought to be very small bothriolepids.

Genera

''Hohsienolepis''

Fossils of this genus are found in the Xindu Formation portion of the Late Emsian-aged Chuandong Assembly, in Pingle,

Guangxi Guangxi (; ; Chinese postal romanization, alternately romanized as Kwanghsi; ; za, Gvangjsih, italics=yes), officially the Guangxi Zhuang Autonomous Region (GZAR), is an Autonomous regions of China, autonomous region of the People's Republic ...

Province, China. Compared to other microbrachiid genera, ''Hohsienolepis'' has a comparatively small head, and an elongated thorax. The armor plates are covered in rows of small tubercles, in a pattern similar to that of ''M. sinensis''.

''Microbrachium''

A genus of very small antiarchs, originally described from ''M. dicki'', of Upper Givetian strata of Scotland and Estonia, including the John O'Groats sandstone of

Caithness Caithness ( gd, Gallaibh ; sco, Caitnes; non, Katanes) is a historic county, registration county and lieutenancy area of Scotland. Caithness has a land boundary with the historic county of Sutherland to the west and is otherwise bounded by ...

, and the Eday beds of the

Orkney Islands Orkney (; sco, Orkney; on, Orkneyjar; nrn, Orknøjar), also known as the Orkney Islands, is an archipelago in the Northern Isles of Scotland, situated off the north coast of the island of Great Britain. Orkney is 10 miles (16 km) north ...

. The various species have proportionally big heads and short thoracic armors. The armor plates are decorated in small tubercles. During the 1980s, two more species were described from slightly older strata in

China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...

''Wudinolepis''

As the generic name suggests, ''Wudinolepis'' is found in the Wuding Formation, a Late Emsian-aged stratum in

Yunnan Yunnan , () is a landlocked Provinces of China, province in Southwest China, 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 ...

, China. It is even smaller than ''Microbrachium,'', with the length of its (thoracic) shield around 2 centimeters. ''Wudinolepis'' was once placed in its own family, "Wudinolepidae", though Denison (1978) placed it within Bothriolepidae, saying that nothing in the original description excluded it from the latter family. Later, when Microbrachiidae was erected, ''Wudinolepis'' was placed within it.

References

Placoderms of Asia Placoderms of Europe Antiarchi Fossils of China Placoderm families Early Devonian first appearances Middle Devonian extinctions {{placoderm-stub