''Thanahita'' 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 extinct

lobopodia Lobopodians are members of the informal group Lobopodia (), or the formally erected phylum Lobopoda Cavalier-Smith (1998). They are panarthropods with stubby legs called lobopods, a term which may also be used as a common name of this group as ...

n and known from the middle

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 ...

Herefordshire Lagerstätte Coalbrookdale Formation, earlier known as Wenlock Shale or Wenlock Shale Formation and also referred to as Herefordshire Lagerstätte in palaeontology, is a fossil-rich deposit (''Konservat-Lagerstätte'') in Powys and Herefordshire at the Engla ...

at the

England–Wales border The England–Wales border, sometimes referred to as the Wales–England border or the Anglo-Welsh border, runs for from the Dee estuary, in the north, to the Severn estuary in the south, separating England and Wales. It has followed broadly ...

in UK. It is

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unisp ...

and contains one species, ''Thanahita distos.'' Discovered in 2018, it is estimated to have lived around 430 million years ago and is the first Silurian lobopodian known worldwide.

Discovery

''Thanahita'' was discovered in 2018 during a palaeontological expedition funded by the

Natural Environment Research Council The Natural Environment Research Council (NERC) is a British Research Councils UK, research council that supports research, training and knowledge transfer activities in the environmental sciences. History NERC began in 1965 when several envir ...

(NERC) and the

Leverhulme Trust The Leverhulme Trust () is a large national grant-making organisation in the United Kingdom. It was established in 1925 under the will of the 1st Viscount Leverhulme (1851–1925), with the instruction that its resources should be used to cover ...

. The team of researchers comprised Derek J. Siveter (

University of Oxford The University of Oxford is a collegiate university, collegiate research university in Oxford, England. There is evidence of teaching as early as 1096, making it the oldest university in the English-speaking world and the List of oldest un ...

), Derek E. G. Briggs (

Yale University Yale University is a Private university, private Ivy League research university in New Haven, Connecticut, United States. Founded in 1701, Yale is the List of Colonial Colleges, third-oldest institution of higher education in the United Stat ...

), David J. Siveter (

University of Leicester The University of Leicester ( ) is a public university, public research university based in Leicester, England. The main campus is south of the city centre, adjacent to Victoria Park, Leicester, Victoria Park. The university's predecessor, Univ ...

), Mark D. Sutton (

Imperial College London Imperial College London, also known as Imperial, is a Public university, public research university in London, England. Its history began with Prince Albert of Saxe-Coburg and Gotha, Prince Albert, husband of Queen Victoria, who envisioned a Al ...

) and David Legg (

University of Manchester The University of Manchester is a public university, public research university in Manchester, England. The main campus is south of Manchester city centre, Manchester City Centre on Wilmslow Road, Oxford Road. The University of Manchester is c ...

). The

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...

was discovered from the Herefordshire Lagerstätte, which has been known to be a rich source of fossils of diverse animals. The only fossil of ''Thanahita'' (designated OUMNH C.29699) was collected from the upper part of Wenlock Series of the Lagerstätte. The scientific genus name is derived from the Greek word, ''

Theia Theia (; , also rendered Thea or Thia), also called Euryphaessa (, "wide-shining"), is one of the twelve Titans, the children of the earth goddess Gaia and the sky god Uranus in Greek mythology. She is the Greek goddess of sight and vision, an ...

'', meaning goddess, and

Anahita Anahita is the Old Persian form of the name of an Iranian goddess and appears in complete and earlier form as ('), the Avestan name of an Indo-Iranian cosmological figure venerated as the divinity of "the Waters" ( Aban) and hence associat ...

, an ancient Indo-Iranian deity of ‘the Waters’ (in Persian); while the specific name comes from the Greek ''distolos'', meaning in pairs, plus ''acherdos'', meaning a hedge shrub, alluding to the bilateral tufted papillae on the trunk.

Morphology

''Thanahita'' is an animal with elongated worm-like body and at least 9 pairs of stumpy legs called

lobopods Lobopodians are members of the informal group Lobopodia (), or the formally erected phylum Lobopoda Cavalier-Smith (1998). They are panarthropods with stubby legs called lobopods, a term which may also be used as a common name of this group as w ...

. The only available fossil is not complete and the entire structure is not known. However, it is preserved in a three-dimenstional structure from which the remaining body parts could be nicely examined. The body has three main parts: the head, neck and trunk. The head appears to be oval shaped, but much of it is missing. With the missing head part, the entire body length is 3 cm and about 2 mm wide. The neck has at least 2 pairs 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 legs that are smaller than the legs at the trunk. There are 7 pairs of legs on the trunk. Each leg bears one or two claws; leg number 4 and 5 having two claws, while leg 6 to 9 have one claw each. All the legs are arranged with a space of about 0.8 mm in between. Semicircular papillae or

sclerites 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 commonly ...

are present on is back throughout most of its body length. These papillae are not uniformly present in each transverse line of the body, and are in pairs in some part but singly in the posterior region. The papillae bear tufts on their surfaces. The tufts are arranged in a grid, four columns wide, with about four rows of tufts per leg segment from the neck to the posterior end.

Taxonomy

''Thanahita'' possess some shared features (e.g. anterior pairs of slender legs; reduced tail) with ''

Cardiodictyon ''Cardiodictyon'' is a genus of lobopodian known from 518 millions years old Chengjiang Lagerstätte. 525 millions years old partial fossil is also reported. It has ~25 pairs of legs, each associated with a pair of dorsal plates. Each leg termi ...

'', ''

Carbotubulus ''Carbotubulus'' is a genus of Lobopodia, lobopodian known from the Carboniferous Carbondale Formation of the Mazon Creek fossil beds, Mazon Creek area in Illinois, US. A Monotypic taxon, monotypic genus, it contains one species ''Carbotubulus wal ...

,'' and ''

Hallucigenia ''Hallucigenia'' is a genus of lobopodian known from Cambrian aged 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 appearance and eccen ...

,'' which have been classified within a single

lobopodian Lobopodians are members of the informal group Lobopodia (), or the formally erected phylum Lobopoda Cavalier-Smith (1998). They are panarthropods with stubby legs called lobopods, a term which may also be used as a common name of this group as w ...

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Hallucigeniidae Hallucigeniidae is a family of extinct panarthropods belonging to the group Lobopodia that originated during the Cambrian explosion. It is based on the species '' Hallucigenia sparsa'', the fossil of which was discovered by Charles Doolittle Wa ...

. Thus, ''Thanahita'' also belongs to the same family, with ''Thanahita'' being a basal member or ''Hallucigenia'' as its closest relative. Since it is younger than other hallucigeniids, it is likely one of the last member of the family before the evolution of velvet worms (

onychophorans Onychophora (from , , "claws"; and , , "to carry"), commonly known as velvet worms (for their velvety texture and somewhat wormlike appearance) or more ambiguously as peripatus (after the first described genus, ''Peripatus''), is a phylum of el ...

), an extant

panarthropod Panarthropoda is a clade comprising the greatest diversity of animal groups. It contains the extant phyla Arthropoda (Euarthropoda), Tardigrada (water bears) and Onychophora (velvet worms), although the precise relationships among these remained ...

phylum which may or may not closely related to hallucigeniids.

References

{{Taxonbar, from=Q110517121 Fossil taxa described in 2018 Lobopodia Silurian United Kingdom Paleontology in the United Kingdom Silurian genus extinctions