''Maldybulakia'' is a genus of freshwater arthropod which lived during the

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...

period. ''Maldybulakia'' is known from three species, ''M. angusi'' and ''M. malcolmi'' from Australia, and ''M. mirabilis'' from Kazakhstan. Although it was originally described as a myriapod-like animal, it was later considered related to the xiphosurans, a group including modern horseshoe crabs.

Discovery and etymology

In 1992, the type species of ''Maldybulakia'' is described from the

Pragian The Pragian is one of three faunal stages in the Early Devonian Epoch. It lasted from 410.8 ± 2.8 million years ago to 407.6 ± 2.8 million years ago. It was preceded by the Lochkovian Stage and followed by the Emsian Stage. The most important La ...

to Emsian-aged Sheshen'karinskaya Formation (also known as the Sheshenkarinskoy Suite) in central Kazakhstan, with

scientific name In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...

''Lophodesmus mirabilis''. The genus name ''Lophodesmus'' came from the Greek ''lophos'' ("tubercle") and ''desmos'' ("bond"), and the species name ''mirabilis'' means "wonderful" in Latin. However, this genus name is already used for an extant genus of myriapod, and in 1998, the new genus name ''Maldybulakia'', named after Maldybulak Farm in the Bayanaul District, Pavlodar Region in Kazakhstan, was given to the animal. In addition, in 1998, two new species of ''Maldybulakia'' were described from two localities in the Devonian of New South Wales. ''M. angusi'' is described from the Lochkovian to earliest

-aged Sugarloaf Creek Formation, ''M. malcomi'' is from Saltwater Creek Forest Road, usually regarded as Middle Devonian in age though some fossil contents give estimation between the Givetian to the Frasnian. The two species were named after Australian musicians Malcolm and Angus Young.

Morphology

''Maldybulakia'' is a large-sized arthropod around , characterized with flat diplosegments like myriapods. ''M. malcomi'' had trunks up to , and had relatively minor serial variation on the pleurotergites. ''M. malcomi'' lacked long paratergal spines, posteromedian spines, and tuberculation. ''M. angusi'' had considerable serial variation on the pleurotergites. ''M. angusi'' is characterized with very long paratergal spines on the most bilobate trunk pleurotergites. Inferred width across spines up to approximately .

Paleoecology

All species of ''Maldybulakia'' are known from freshwater sediments. According to the only associated fossils, the abundant lycopod flora with ''M. malcolmi'' and the presence of spiracles suggests terrestrial habits for ''Maldybulakia''.

Classification

Due to lack of information on the cephalic structure,

appendage An appendage (or outgrowth) is an external body part, or natural prolongation, that protrudes from an organism's body. In arthropods, an appendage refers to any of the homologous body parts that may extend from a body segment, including anten ...

s, position of the gonopore and genital morphology, it is controversial where to place ''Maldybulakia'' within Arthropoda. In 1992, it was classified as Arthropoda '' incertae sedis'', as its characteristics did not permit its identification as a members of Kampecarida,

Euthycarcinoidea Euthycarcinoidea are an enigmatic group of extinct possibly amphibious arthropods that ranged from Cambrian to Triassic times. Fossils are known from Europe, North America, Argentina, Australia and Antarctica. Description The euthycarcinoid body ...

and Arthropleurida. In 1998, it was classified as a possible Dignatha in Myriapoda, rather than the alternatively proposed

Crustacea Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean gro ...

. However, after 2010s, ''Maldybulakia'' is commonly treated as an unspecified xiphosuran genus, due to morphological similarity with the

synziphosurine Synziphosurina is a paraphyletic group of chelicerate arthropods previously thought to be basal horseshoe crabs (Xiphosura). It was later identified as a grade composed of various basal euchelicerates, eventually excluded form the monophyletic Xi ...

'' Willwerathia''.Dunlop, J. A., Penney, D. & Jekel, D. 2020
A summary list of fossil spiders and their relatives
In World Spider Catalog. Natural History Museum Bern, online at http://wsc.nmbe.ch, version 20.5

References

{{Taxonbar, from=Q112895509 Xiphosura Devonian animals of Australia Fossils of Australia Devonian animals of Asia Fossils of Kazakhstan Fossil taxa described in 1998 Prehistoric arthropod genera