''Parastemmiulus'' is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

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 ...

millipede Millipedes (originating from the Latin , "thousand", and , "foot") 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 derive ...

in the

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 ...

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 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 in ...

, and the oldest Stemmiulidae fossil species as of 2013.

History and classification

''Parastemmiulus elektron'' was described from a solitary fossil, which is preserved as an

inclusion Inclusion or Include may refer to: Sociology * Social inclusion, action taken to support people of different backgrounds sharing life together. ** Inclusion (disability rights), promotion of people with disabilities sharing various aspects of lif ...

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 The Instituto Nacional de Antropología e Historia (INAH, ''National Institute of Anthropology and History'') is a Federal government of the United Mexican States, Mexican federal government bureau established in 1939 to guarantee the researc ...

in San Cristóbal de las Casas,

Simojovel Simojovel is a Municipalities of Chiapas, municipality in the List of states in Mexico, Mexican state 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 ...

. The

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

fossil is composed of a very complete adult female recovered from the La Guadalupe Quarry. Mexican amber is recovered from fossil bearing rocks in the

region of

Chiapas Chiapas, officially the Free and Sovereign State of Chiapas, is one of the states that make up the Political divisions of Mexico, 32 federal entities of Mexico. It comprises Municipalities of Chiapas, 124 municipalities and its capital and large ...

, Mexico. The amber dates from between 23 million years old at the oldest and 15 million years at the youngest. The La Guadalupe Quarry site is an outcrop of amber bearing strata belonging to the Mazantic shale. 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 The Universidad Autónoma del Estado de Morelos (Autonomous University of the State of Morelos, UAEM) is a university in Cuernavaca, Morelos, Mexico. It is the largest institution of higher education in Morelos, with facilities statewide. Histor ...

with their 2013

type description A species description is a formal scientific description of a newly encountered species, typically articulated through a scientific publication. Its purpose is to provide a clear description of a new species of organism and explain how it differ ...

of the genus and species being published in the

natural science Natural science or empirical 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 ...

s journal ''

Historical Biology ''Historical Biology'' is a peer-reviewed scientific journal of paleobiology. It was established in 1988, and is published by Taylor & Francis. The journal is edited by Mark T. Young. Abstracting and indexing The journal is abstracted and in ...

''. The genus name is a combination of the genus '' Stemmiulus'' and "para" meaning ''along side'', a reference to the similarities between the two genera. The

specific epithet 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 ...

''elektron'' is based from the Greek word meaning amber. ''Parastemmiulus elektron'' is one of three millipede species described from Mexican amber, the others being '' Anbarrhacus adamantis'' and '' Maatidesmus paachtun'', 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 in ...

. One possible Stemmulid fossil was described from Dominican amber, however it was not complete, and has been regarded as doubtful. ''P. elektron'' is the first Stemmulid genus described from a fossil.

Description

The ''P. elektron'' female is reddish-brown in overall coloration with the legs a brownish tone that trends to

hyaline A hyaline substance is one with a glassy appearance. The word is derived from , and . Histopathology Hyaline cartilage is named after its glassy appearance on fresh gross pathology. On light microscopy of H&E stained slides, the extracellula ...

. The body is composed of forty six segments and has a length of approximately . The ocellar field is shallow and triangular in shape with three

ocelli A simple eye or ocellus (sometimes called a pigment pit) is a form of eye or an optical arrangement which has a single lens without the sort of elaborate retina that occurs in most vertebrates. These eyes are called "simple" to distinguish the ...

, and is positioned just to the rear of the antennae. Two grooved possible sensory canals are present in the field, one connecting the rear and front ocelli, the other connecting the middle ocelli to the antenna socket. Present is a defined, pear-shaped Tömösváry organ located below the antenna socket and reaching the ocellar field. The antennae have a total of eight

antennomeres An antenna (plural: antennae) is one of a pair of appendages used for sensing in arthropods. Antennae are sometimes referred to as ''feelers''. Antennae are connected to the first one or two segments of the arthropod head. They vary widely in ...

that vary in length. The largest segment is antennomere 2, while the smallest is antennomere 7. The low ocelli numbers, differences in ocelli sizes, and varied antennomere lengths is a combination of characters only found in Stemmiulida. However, in contrast to ''P. elektron'' living species of the family do not have a Tömösváry organ.

References

External links

* {{Taxonbar, from1=Q21682645, from2=Q21682647 Millipedes †Parastemmiulus Prehistoric myriapod genera Fossil taxa described in 2013 Millipedes of North America Miocene arthropods Mexican amber Monotypic myriapod genera