''Anbarrhacus'' is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

millipede Millipedes are a group of arthropods that are characterised by having two pairs of jointed legs on most body segments; they are known scientifically as the class Diplopoda, the name derived from this feature. Each double-legged segment is a resu ...

in the

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

Platyrhacidae known from a fossil found in North America. There is one described species in the genus, ''Anbarrhacus adamantis'', which is one of three millipedes described from

Mexican amber Mexican amber, also known as Chiapas Amber is amber found in Mexico, created during the Early Miocene and middle Miocene epochs of the Cenozoic Era in southwestern North America. As with other ambers, a wide variety of taxa have been found as inc ...

History and classification

''Anbarrhacus adamantis'' was described from a solitary fossil, which is preserved as an

inclusion Inclusion or Include may refer to: Sociology * Social inclusion, aims to create an environment that supports equal opportunity for individuals and groups that form a society. ** Inclusion (disability rights), promotion of people with disabiliti ...

in a transparent chunk of Mexican amber. At the time of description, the amber specimen was housed in the fossil collection of the Instituto Nacional de Antropología e Historia in

San Cristóbal de las Casas San Cristóbal de las Casas (), also known by its native Tzotzil name, Jovel (), is a town and municipality located in the Central Highlands region of the Mexican state of Chiapas. It was the capital of the state until 1892, and is still cons ...

Simojovel Simojovel is one of the 119 municipalities of Chiapas, in southern Mexico. As of 2010, the municipality had a total population of 40,297, up from 31,615 as of 2005. It covers an area of 446.99 km2. The municipality had 145 localities, the ...

. The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of sever ...

fossil is composed of a very complete immature male recovered from the Guadalupe Victoria site. Mexican amber is recovered from fossil bearing rocks in the

region of Chiapas, Mexico. The amber dates from between 23 million years old at the oldest and 15 million years at the youngest. The Guadalupe Victoria site is an outcrop of amber bearing strata belonging to both the Mazantic Shale and

Balumtum Sandstone The Balumtun Sandstone is a geologic formation in Chiapas, Mexico. The formation is up to 760 metres thick, and consists of gray sandstone, that were deposited during the Upper Aquitanian stage of the Early Miocene. See also * List of fossilif ...

. The deposits preserve a transitional river or stream environments near the coast and preserves fossils of a mangrove forest ecosystem. The holotype was first studied by a team of researchers headed by Francisco Riquelme of the Universidad Autónoma del Estado de Morelos with their 2014

type description A species description is a formal description of a newly discovered species, usually in the form of a scientific paper. Its purpose is to give a clear description of a new species of organism and explain how it differs from species that have be ...

of the genus and species being published in the

natural sciences Natural science is one of the branches of science concerned with the description, understanding and prediction of natural phenomena, based on empirical evidence from observation and experimentation. Mechanisms such as peer review and repeatab ...

journal '' PLOS ONE''. The genus name is a derived from a combination of the Arabic voice word ''ánbar'' for "amber" and ''rhacus'', which is used frequently as a genus suffix in the family Platyrhacidae. The specific epithet ''adamantis'' was coined from the neo Latin word ''adamantus'' meaning diamond, a reference to the patterning on the tops of the collum and metatergites. ''A. adamantis'' is one of three millipede species described from Mexican amber, the others being ''

Maatidesmus paachtun ''Maatidesmus'' is an extinct genus of millipede in the family Chelodesmidae known from a fossil found in North America. There is one described species in the genus, ''Maatidesmus paachtun'', one of three millipedes described from Mexican amb ...

'' and ''

Parastemmiulus elektron ''Parastemmiulus'' is an extinct genus of millipede in the family Stemmiulidae known from a fossil found in Mexico. There is one described species in the genus, ''Parastemmiulus elektron''. The species is one of three millipedes described fr ...

'', while a number of other species have been described from the similarly aged

Dominican amber Dominican amber is amber from the Dominican Republic derived from resin of the extinct tree '' Hymenaea protera''. Dominican amber differentiates itself from Baltic amber by being nearly always transparent, and it has a higher number of fossil inc ...

Description

The ''A. adamantis'' male is mostly a creamy white in coloration with a yellowish tone to the labrum and areas of the legs. The sterna grade between yellowish and brown. The total body length is approximately and has a total of 17 body segments plus head. The head is a little wider than the next body segment, called the collum. The antennae have a total of seven

antennomeres Antennae ( antenna), sometimes referred to as "feelers", are paired appendages used for Sensory system, sensing in arthropods. Antennae are connected to the first one or two Segmentation (biology), segments of the arthropod head. They vary widel ...

that vary in length and form a club-shaped tip. The longest segment is antennomere 5 followed by antennomere 6, and the shortest are antennomeres 1 and 7. Both antennomeres 5 and 6 have long

seta In biology, setae (singular seta ; from the Latin word for " bristle") are any of a number of different bristle- or hair-like structures on living organisms. Animal setae Protostomes Annelid setae are stiff bristles present on the body. ...

e near their apical ends, and the antennae have four sensory cones preserved. The upper plates of the body segments after the collum are heavily lobed forming metatergites and paranota. The surface of the paranota, side lobes of the metatergites, have a granular texturing, and the metatergites have a distinct diamond shaped patterning in the texturing. The segments gradually get wider from the head to about two thirds of the way down the body after which the segments start to narrow progressively to segment 17. The male is mature enough to show developing bulb shaped

gonopod Gonopods are specialized appendages of various arthropods used in reproduction or egg-laying. In males, they facilitate the transfer of sperm from male to female during mating, and thus are a type of intromittent organ. In crustaceans and millipe ...

s on segment 7.

References

External links

* * {{Taxonbar, from=Q21682642 † Fossil taxa described in 2014 Millipedes of North America Miocene arthropods Mexican amber †Anbarrahacus Prehistoric myriapod genera