''Mecistocephalus evansi'' is a

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), ...

of soil centipede 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 ...

Mecistocephalidae Mecistocephalidae is a monophyletic family of centipedes in the order Geophilomorpha. It is the only family in the suborder Placodesmata. Most species in this family live in tropical or subtropical regions, but some occur in temperate regions. T ...

. This

centipede Centipedes (from Neo-Latin , "hundred", and Latin , "foot") are predatory arthropods belonging to the class Chilopoda (Ancient Greek , ''kheilos'', "lip", and Neo-Latin suffix , "foot", describing the forcipules) of the subphylum Myriapoda, ...

is found in

Iraq Iraq, officially the Republic of Iraq, is a country in West Asia. It is bordered by Saudi Arabia to Iraq–Saudi Arabia border, the south, Turkey to Iraq–Turkey border, the north, Iran to Iran–Iraq border, the east, the Persian Gulf and ...

Israel Israel, officially the State of Israel, is a country in West Asia. It Borders of Israel, shares borders with Lebanon to the north, Syria to the north-east, Jordan to the east, Egypt to the south-west, and the Mediterranean Sea to the west. Isr ...

, and

Iran Iran, officially the Islamic Republic of Iran (IRI) and also known as Persia, is a country in West Asia. It borders Iraq to the west, Turkey, Azerbaijan, and Armenia to the northwest, the Caspian Sea to the north, Turkmenistan to the nort ...

. This species is notable for featuring 51 pairs of legs rather than the 49 leg pairs usually observed in the

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 ...

'' Mecistocephalus''.

Discovery, distribution, and habitats

This species was first described by the French

myriapodologist Myriapodology is the scientific study of myriapods which includes centipedes and millipedes. The field of myriapodology can also cover other myriapods such as pauropods and symphylans. Those who study myriapods are myriapodologists. Societies * ...

Henry W. Brolemann in 1922. He based the original description of this species on a single female specimen found in the

Maysan governorate Maysan Governorate () is a governorate in southeastern Iraq, bordering Iran. Its administrative centre is the city of Amarah, and it is composed of six districts. Before 1976, it was named Amara Province. Etymology This region was called ''Messè ...

(formerly Amara province) on the

Tigris The Tigris ( ; see #Etymology, below) is the eastern of the two great rivers that define Mesopotamia, the other being the Euphrates. The river flows south from the mountains of the Armenian Highlands through the Syrian Desert, Syrian and Arabia ...

river in Iraq. Since the discovery of the first specimen, this species has been found in other locations in Iraq, Iran, and Israel. Several specimens have been recorded in Israel, mostly from Mediterranean regions of the

Galilee Galilee (; ; ; ) is a region located in northern Israel and southern Lebanon consisting of two parts: the Upper Galilee (, ; , ) and the Lower Galilee (, ; , ). ''Galilee'' encompasses the area north of the Mount Carmel-Mount Gilboa ridge and ...

, at higher elevations with lower temperatures and more precipitation. The Israeli specimens include those found in

Mount Meron Mount Meron (, ''Har Meron'', renamed after ancient Meiron; , ''Jabal al-Jarmaq'') is a mountain in the Upper Galilee region of Israel. It has special significance in Jewish religious tradition and parts of it have been declared a nature reserv ...

and

Gush Halav Jish (, ), also known by its Hebrew name of Gush Halab (, ), or by its classical name of Gischala, is a local council in Upper Galilee, located on the northeastern slopes of Mount Meron, north of Safed, in Israel's Northern District. In , it h ...

as well as one found in

Be’er Sheva Beersheba ( / ; ), officially Be'er-Sheva, is the largest city in the Negev desert of southern Israel. Often referred to as the "Capital of the Negev", it is the centre of the fourth-most populous metropolitan area in Israel, the List of cities ...

in the

Negev The Negev ( ; ) or Naqab (), is a desert and semidesert region of southern Israel. The region's largest city and administrative capital is Beersheba (pop. ), in the north. At its southern end is the Gulf of Aqaba and the resort town, resort city ...

desert that may be the result of an anthropogenic transfer. This species has also been found in Gakal Cave in the Kohgiluyeh and Boyer-Ahmad province of Iran, indicating that ''M. evansi'' is a

troglophile Troglofauna are small cave-dwelling animals that have adapted to their dark surroundings. Troglofauna and stygofauna are the two types of subterranean fauna (based on life-history). Both are associated with subterranean environments – troglofa ...

, living in subterranean habitats as well as at the surface. Furthermore, specimens have been found in the

Basrah governorate Basra Governorate ( ), also called Basra Province, is a governorate in southern Iraq in the region of Arabian Peninsula, bordering Kuwait to the south and Iran to the east. The capital is the city of Basra, located in the Basrah district. Other ...

in Iraq, including specimens from the Al-Hartha and

Shatt Al-Arab The Shatt al-Arab () is a river about in length that is formed at the confluence of the Euphrates and Tigris rivers in the town of al-Qurnah in the Basra Governorate of southern Iraq. The southern end of the river constitutes the Iran– ...

districts. Specimens collected from the Basrah governorate include five males and six females found in 2022 on wet agricultural land, in the soil under palm trees, on the left bank of the

river and in the Al-Hartha district.

Description

This species has 51 pairs of legs and can reach 38 mm in length. The head is shaped like a rectangle and at least twice as long as wide. The dorsal cephalic plate nearly covers the

forcipules Forcipules are the modified, pincer-like, front legs of centipedes that are used to inject venom into prey. They are the only known examples of front legs acting as venom injectors. Nomenclature Forcipules go by a variety of names in both sci ...

. The forcipular coxosternite has no chitin-lines and is more than 1.2 times longer than wide. The first article of the forcipule has a distinct intermediate denticle as well as a distal denticle. The ultimate article of the forcipule lacks a distinct basal denticle. The body is uniform in width for the first four-fifths of its length, then tapers gradually from about the 40th segment to the last segment. The

sternites The sternum (: sterna) is the ventral portion of a segment of an arthropod thorax or abdomen. In insects, the sterna are usually single, large sclerites, and external. However, they can sometimes be divided in two or more, in which case the sub ...

on the anterior part of the trunk, from the second sternite to about the 23rd sternite, feature a distinct median groove that divides into two short branches at the anterior end. A shallow longitudinal impression replaces this groove on the sternites on the posterior part of the trunk. There are no clusters of pores on the ventral surface of the trunk. The posterior end of the last leg-bearing segment has a subtriangular ventral

sclerite A sclerite (Greek language, Greek , ', meaning "hardness, 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. Instea ...

with a distinctly rounded posterior margin. The

ultimate legs Ultimate legs are a pair of modified rear legs unique to centipedes. Although they do not aid in locomotion, ultimate legs are used for a variety of uses, and their morphology varies accordingly. Sexual dimorphism is frequently present. Usage ...

have no pretarsus. In adults, the ventral side of the basal element of each ultimate leg has more than twelve scattered pores. This species shares many traits with other centipedes in the genus ''Mecistocephalus''. For example, like other species in this genus, ''M. evansi'' features a head that is evidently longer than wide and a body that tapers towards the posterior end. Furthermore, the coxosternite of the first maxillae is divided. Unlike most other species of ''Mecistocephalus'', however, ''M. evansi'' features 51 leg pairs rather than the 49 pairs usually observed in this genus. Although some other species of ''Mecistocephalus'' also have 51 leg pairs, these species may be distinguished from ''M. evansi'' based on other traits. For example, like the species ''M. evansi'', the species '' M. erythroceps'' features not only 51 leg pairs but also a bifurcated median groove on the sternites. This bifurcation is faint in ''M. erythroceps'', however, and thus less distinct and more obscure than in ''M. evansi''.

References

{{Taxonbar, from1= Q6507966 evansi Arthropods of Asia Taxa named by Henry Wilfred Brolemann Animals described in 1922