Siphoniulus

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Siphoniulus
Temporal range: Cenomanian–Present
Two views of Siphoniulus alba head
Scientific classification
Kingdom:
Animalia
Phylum:
Arthropoda
Subphylum:
Myriapoda
Class:
Diplopoda
Order:
Siphoniulida

Cook
, 1895
Family:
Siphoniulidae

Pocock, 1894
Genus:
Siphoniulus

Pocock, 1894
Species

S. alba Pocock, 1894
S. neotropicus Hoffman, 1979
†S. muelleri
†S. preciosus

Siphoniulus is a poorly known

Helminthomorpha
("worm-like millipedes").

Description

Siphoniulids are small and eyeless.

gonopods (modified copulatory legs) consisting of the anterior limbs on the seventh segment, and which are partially recessed into the body. The telson (rear-most segment) possesses small bristle-like structures called spinnerets.[2]

Distribution

S. alba is only known from a single specimen collected in 1894 near

Maninjau on the Indonesian island of Sumatra. S. neotropicus was discovered near the Mayan ruins of Tikal in Guatemala, and is also known from the Mexican states of Chiapas and Veracruz.[2] The extinct species S. muelleri and S. preciosus are known from Late Cretaceous Burmese amber.[4]

History

Siphoniulus alba (and the family Siphoniulidae) was described in 1894 by

leaf litter from Mexico sorted by researchers at the Field Museum of Natural History revealed new specimens of S. neotropicus, allowing for complete anatomical descriptions and characterization of the gonopods.[2]

Classification

Simplified cladogram from Sierwald et al 2003[2]

Polyxenida

Chilognatha
The incorporation of Siphoniulida anatomy did not clearly resolve relationships of millipede orders.
Simplified cladogram from Sierwald & Bond 2007[6]

Polyxenida

Chilognatha
Combining morphological with molecular data improved resolution, and also supported a basal helminthomorph placement of Siphoniulida.

Siphoniulids have been classified in various, conflicting placements within the

Helminthomorpha ("worm-like" millipedes) since their initial description, and their relation to the rest of millipedes is still unresolved. When first described, the family Siphoniulidae was placed in the "Suborder" Colobognatha, a group that is now recognized as a larger grouping including the orders Platydesmida, Polyzoniida, and Siphonophorida.[5] The following year, the American entomologist Orator F. Cook considered Stemiulids as "suborder Siphoniuloidea", closely related to Julidans and Spirostreptidans (a grouping termed Diplochaeata). In 1979, Hoffman placed Siphoniulida (now considered an order) as Helminthomorph incertae sedis, meaning the placement within Helminthomorphs was undetermined, due to the absence of male specimens.[7][b] With only two known species, Siphoniulida is the smallest order of millipedes, followed by Siphonocryptida with three to six species.[8][9]

In more recent years, millipedes have been studied by

DNA sequence data from other groups, Siphoniulida again appeared as basal within Helminthomorpha.[6]

Notes

  1. ^ The holotype and only known specimen of S. alba was described as 11 mm, but the anterior part of it is now missing.[2]
  2. ^ Gonopod morphology is one of the primary diagnostic traits in millipedes.

References

  1. ^ Millipede phylogeny revisited in the light of the enigmatic order Siphoniulida
  2. ^
    doi:10.1046/j.1439-0469.2003.00202.x
    .
  3. ^
    doi:10.5962/bhl.part.82318
    .
  4. doi:10.1016/j.cretres.2017.01.009
    .
  5. ^ a b Pocock, R. I. (1894). "Chilopoda, Symphyla and Diplopoda from the Malay Archipelago". Zoologische Ergebnisse einer Reise in Niederländisch Ost-Indien. 3: 307–404..
  6. ^
    PMID 17163800
    .
  7. ^ Hoffman RL. (1979) Classification of the Diplopoda. Geneve: Mus. Hist. Nat. 237 pp.
  8. PMID 22615951
    .
  9. doi:10.11646/zootaxa.2681.1.6
    .
  10. doi:10.1111/j.1439-0469.1984.tb00559.x
    .

External links