Diatomyidae

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Diatomyidae
Temporal range: 32.5–0 
Ma
 Early Oligocene - Recent
Young male Laotian rock rat, Laonastes aenigmamus
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Rodentia
Suborder: Hystricomorpha
Superfamily:
Ctenodactyloidea
Family: Diatomyidae
Mein & Ginsburg, 1997
Type genus
Diatomys
Li, 1974
Genera

Laonastes

†Diatomys
†Fallomus
†Marymus
†Willmus
†Inopinatia
†? Pierremus

Synonyms

Laonastidae Jenkins et al. 2005

Diatomyidae is a family of hystricomorph rodents. It is represented by a single living species,

Laonastes aenigmamus, native to Laos in Southeast Asia. Fossil species are known from the Oligocene and Miocene
of Asia and eastern Europe.

"Lazarus effect"

Before Laonastes was discovered, the family Diatomyidae was known only from

Balochistan, Pakistan, to Middle/Late Miocene fossils (11 Mya) of Diatomys
.

Jenkins et al.[3] reported the discovery of a wholly unique new species of rodent, Laonastes aenigmamus, for which they created a new family, Laonastidae. They suggested it was a hystricognath rodent, but basal to all other hystricognaths. Dawson, et al,[4] re-evaluated the phylogenetic position of Laonastes based on morphology and included fossil taxa in their analysis. They determined Laonastes is actually sciurognathous and belongs to the Diatomyidae. They also described the Diatomyidae as a Lazarus taxon due to the 11-million-year gap between the most recent diatomyid in the fossil record and the existence of Laonastes today. The only other comparable length of time for a mammal Lazarus taxon is the monito del monte, which is part of a family (Microbiotheriidae), also most recently known from Miocene deposits. Mary Dawson described Laonastes as the "coelacanth of rodents".[5]

Characteristics

The Diatomyidae are similar to both the

springhare, gundis, and Hystricognathi). The single premolar
on both the upper and lower tooth rows is enlarged (unlike the reduced state in Ctenodactylidae). Most diatomyids have cheek teeth with four roots except for the first. In Laonastes, the lower molars have four roots, but upper cheek teeth have three roots including a U-shaped anterior root that may be derived from the merging of two roots.

Living diatomyids are only represented by the Laotian rock rat from the

Khammouan region of Laos. Fossil diatomyids have been recovered in Pakistan, India, Thailand, China, Japan, and Serbia.[6]

Relationship to other rodents

The uniqueness of the

molecular studies suggested Laonastes is a member of the rodent suborder Hystricognathi
. The morphological analysis suggested it is the most basal hystricognath. Fossil taxa were not included in the morphological analysis.

Analysis of

naked mole rat
. Another type of analysis on the cytochrome b sequence data produced the same result as morphology. Neither analysis, however, showed entirely robust statistical support for the position of Laonastes within the hystricognaths; altogether, it appeared to belong among the basal African radiation.

Dawson et al.[4] also refuted the notion that Laonastes is a hystricognath and instead argued that the mandible is sciurognathous. They evaluated Laonastes in comparison to several fossil rodents and determined it is closely related to the diatomyids, particularly Diatomys. Their results suggested the Diatomyidae are a sister group to the Ctenodactylidae, and this diatomyid/ctenodactylid clade (along with the Yuomyidae) is sister to the Hystricognathi.

Besides Laonastes, other diatomyids have also been placed in different families. Some

Ctenodactyloidea.[7] Marivaux et al.[10]
united the two into a single family (Diatomyidae), but also suggested this family might be related to the Pedetidae.

Dawson's fossil study

Tethys Sea.[12] Alternatively, the entire Ctenodactyloidea might be of African origin, or the lineage split took place on India as it joined the Asian mainland, with the gundis reaching Africa via the Mascarene Plateau's archipelagos and island continents.[13] Each hypothesis would unite the paleontological, anatomical, and molecular findings into a robust model. Which one is preferred depends on whether the Hystricomorpha were Laurasian or Gondwanan
in origin.

Species

References

  1. ^ Marivaux, L. & Welcomme, J.-L. 2003. New diatomyid and baluchimyine rodents from the Oligocene of Pakistan (Bugti Hills, Balochistan): Systematic and paleobiogeographic implications. Journal of Vertebrate Paleontology 23:420-434.
  2. ^ Flynn, L. J., L. L. Jacobs, and I. U. Cheema. 1986. Baluchimyinae, a new ctenodactyloid subfamily from the Miocene of Baluchistan. American Museum Novitates, 2841:1-58.
  3. ^
    doi:10.1017/S1477200005001775
  4. ^ a b c Dawson, M. R., L. Marivaux, C.-k. Li, K. C. Beard, and G. Métais. 2006. Laonastes and the "Lazarus effect" in Recent mammals. Science, 311:1456-1458.
  5. ^ "Back from the dead: Living fossil identified". NBC News. 9 March 2006.
  6. PMID 30956714
    .
  7. ^ a b Mein, P. and L. Ginsburg, L. 1985. Les rongeurs miocènes de Li (Thailande). Compte Rendus de l’Académie des Sciences, Paris, Série II, 301:1369-1374.
  8. ISBN 0-231-11013-8
  9. ^ Flynn, L. J. and M. E. Morgan. 2005. An Unusual Diatomyid Rodent from an Infrequently Sampled Late Miocene Interval in the Siwaliks of Pakistan, Palaeontologia Electronica Vol. 8, Issue 1; 17A:10p, [1][permanent dead link]
  10. ^ Marivaux, L., M. Vianey-Liaud, and J.-J. Jaeger. 2004. High-level phylogeny of early Tertiary rodents: dental evidence. Zoological Journal of the Linnean Society, 142:105-134.
  11. doi:10.1073/pnas.0701289104
    (HTML abstract)
  12. ^ Marivaux, L. J. L. Welcomme, M. Vianey-Liaud, and J.J. Jaeger. 2002. The role of Asia in the origin and diversification of hystricognathous rodents. Zoologica Scripta, 31:225-239.
  13. ^ Nanda, A.C. & Sahni, A. (1998). Ctenodactyloid rodent assemblage from Kargil Formation, Ladakh molasses group: Age and paleobiogeographic implications for the Indian subcontinent in the Oligo-Miocene. Geobios 31:533-544.
  14. S2CID 41698521
    .

External links
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