''Maldybulakia'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of freshwater

arthropod Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metam ...

which lived during Late

Silurian The Silurian ( ) is a geologic period and system spanning 23.5 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the third and shortest period of t ...

to Late

Devonian The Devonian ( ) is a period (geology), geologic period and system (stratigraphy), system of the Paleozoic era (geology), era during the Phanerozoic eon (geology), eon, spanning 60.3 million years from the end of the preceding Silurian per ...

. ''Maldybulakia'' is known from three

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

, ''M. angusi'' and ''M. malcolmi'' from Australia, ''M. mirabilis'' from

Kazakhstan Kazakhstan, officially the Republic of Kazakhstan, is a landlocked country primarily in Central Asia, with a European Kazakhstan, small portion in Eastern Europe. It borders Russia to the Kazakhstan–Russia border, north and west, China to th ...

, and ''M. saierensis'' from

China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...

. Its classification is uncertain, it was originally described as a

myriapod Myriapods () are the members of subphylum Myriapoda, containing arthropods such as millipedes and centipedes. The group contains about 13,000 species, all of them terrestrial. Although molecular evidence and similar fossils suggests a diversifi ...

-like animal, and later considered related to the

xiphosura Xiphosura (; , in reference to its sword-like telson) is an order of arthropods related to arachnids. They are more commonly known as horseshoe crabs (a name applied more specifically to the only extant family, Horseshoe crab, Limulidae). They fir ...

ns, or an artiopod.

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 ...

Emsian The Emsian is one of three faunal stages in the Early Devonian Epoch. It lasted from 410.62 ±1.95 million years ago to 393.47 ±0.99 million years ago. It was preceded by the Pragian Stage and followed by the Eifelian Stage. It is named after ...

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

scientific name In Taxonomy (biology), taxonomy, binomial nomenclature ("two-term naming system"), also called binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin gramm ...

''Lophodesmus mirabilis''. The genus name ''Lophodesmus'' came from the

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

''lophos'' ("tubercle") and ''desmos'' ("bond"), and the species name ''mirabilis'' means "wonderful" in

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

. 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 Pavlodar Region (; ) is a region of Kazakhstan. The population of the region was and The latest official estimate (as at the start of 2022) was 756,511. Its capital is the city of Pavlodar, which had a population of 360,014 at the start of 201 ...

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 New South Wales (commonly abbreviated as NSW) is a States and territories of Australia, state on the Eastern states of Australia, east coast of :Australia. It borders Queensland to the north, Victoria (state), Victoria to the south, and South ...

. ''M. angusi'' is described from the

Lochkovian The Lochkovian is one of three faunal stages in the Early Devonian Epoch. It lasted from 419.2 ± 3.2 million years ago to 410.8 ± 2.8 million years ago. It marked the beginning of the Devonian Period, and was followed by the Pragian Stage. It is ...

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 The Givetian is one of two faunal stages in the Middle Devonian Period. It lasted from million years ago to million years ago. It was preceded by the Eifelian Stage and followed by the Frasnian Stage. It is named after the town of Givet in ...

to the

Frasnian The Frasnian is one of two faunal stages in the Late Devonian Period. It lasted from million years ago to million years ago. It was preceded by the Givetian Stage and followed by the Famennian Stage. Major reef-building was under way during ...

. The two species were named after Australian musicians

Malcolm Malcolm, Malcom, Máel Coluim, or Maol Choluim may refer to: People * Malcolm (given name), includes a list of people and fictional characters * Malcom (footballer) (born 1997), Brazilian football forward * Clan Malcolm * Maol Choluim de Innerp ...

and

Angus Young Angus McKinnon Young (born 31 March 1955) is an Australian musician, best known as the co-founder, lead guitarist, songwriter, and the only continuous member of the hard rock band AC/DC. He is known for his energetic performances, schoolboy-u ...

. In 2023, new species ''M. saierensis'' is described from Pridoli-aged ‘Xiemisitai’ Formation in Saier Mountains, Hoboksar, western Junggar,

Xinjiang Xinjiang,; , SASM/GNC romanization, SASM/GNC: Chinese postal romanization, previously romanized as Sinkiang, officially the Xinjiang Uygur Autonomous Region (XUAR), is an Autonomous regions of China, autonomous region of the China, People' ...

, northwest China, and it is the earliest record of the genus.

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 . ''M. saierensis'' is characterized by having long paratergal spines on pleurotergites. Width of paratergal spines measures up to over .

Paleoecology

All species of ''Maldybulakia'' are known from freshwater sediments. According to the only associated fossils, the abundant

lycopod Lycopodiopsida is a class of vascular plants also known as lycopsids, lycopods, or lycophytes. Members of the class are also called clubmosses, firmosses, spikemosses and quillworts. They have dichotomously branching stems bearing simple leaves ...

flora with ''M. malcolmi'' and the presence of spiracles suggests

terrestrial Terrestrial refers to things related to land or the planet Earth, as opposed to extraterrestrial. Terrestrial may also refer to: * Terrestrial animal, an animal that lives on land opposed to living in water, or sometimes an animal that lives on o ...

habits for ''Maldybulakia''. ''M. saierensis'' from late Silurian is the oldest body fossil of a putative freshwater arthropod other than from

Laurussia Laurasia () was the more northern of two large landmasses that formed part of the Pangaea supercontinent from around (Million years ago, Mya), the other being Gondwana. It separated from Gondwana (beginning in the late Triassic period) during ...

Classification

Due to lack of information on the

cephalic A head is the part of an organism which usually includes the ears, brain, forehead, cheeks, chin, eyes, nose, and mouth, each of which aid in various sensory functions such as sight, hearing, smell, and taste. Some very simple animals may no ...

structure,

appendage An appendage (or outgrowth) is an external body part or natural prolongation that protrudes from an organism's body such as an arm or a leg. Protrusions from single-celled bacteria and archaea are known as cell-surface appendages or surface app ...

s, position of the

gonopore A gonopore, sometimes called a gonadopore, is a genital pore in many invertebrates. Hexapods, including insects, have a single common gonopore, except mayflies, which have a pair of gonopores. More specifically, in the unmodified female, it is ...

and genital morphology, it is controversial where to place ''Maldybulakia'' within Arthropoda. In 1992, it was classified as Arthropoda ''

incertae sedis or is a term used for a taxonomy (biology), taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertainty ...

'', 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 bod ...

and Arthropleurida. In 1998, it was classified as a possible Dignatha in

Myriapoda Myriapods () are the members of subphylum Myriapoda, containing arthropods such as millipedes and centipedes. The group contains about 13,000 species, all of them terrestrial. Although molecular evidence and similar fossils suggests a diversifi ...

, rather than the alternatively proposed

Crustacea Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquatic arthrop ...

. After 2010s, ''Maldybulakia'' is commonly treated as a

n, a group including modern

horseshoe crabs Horseshoe crabs are arthropods of the family Limulidae and the only surviving xiphosurans. Despite their name, they are not true crabs or even crustaceans; they are chelicerates, more closely related to arachnids like spiders, ticks, and scorpi ...

, due to morphological similarity with the synziphosurine '' 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 In 2020, morphology of ''Willwerathia'' is compared to

Cambrian The Cambrian ( ) is the first geological period of the Paleozoic Era, and the Phanerozoic Eon. The Cambrian lasted 51.95 million years from the end of the preceding Ediacaran period 538.8 Ma (million years ago) to the beginning of the Ordov ...

artiopod ''

Falcatamacaris ''Falcatamacaris'' is an extinct genus of Cambrian artiopodan arthropod, only known from the type species ''F. bellua'' described in 2014, from the Guzhangian (Cambrian Stage 3) aged Weeks Formation in Utah Utah is a landlocked state in ...

''. Since known fossils are incomplete, taxonomic positions is not discussed at description of ''M. saierensis''.

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