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Revision as of 05:56, 12 October 2018

Juramaia
Temporal range: Late Jurassic, 160.89–160.25 Ma
Restoration
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Subclass: Theria
Genus: Juramaia
Luo et al., 2011
Species
  • J. sinensis Luo et al., 2011 (type)

Juramaia is an extinct genus of very basal eutherian mammal from the Late Jurassic (Oxfordian stage) deposits of western Liaoning, China; it is a small shrew-like mammal of body length approximately 70–100 mm.[1][2] Juramaia is known from the holotype BMNH PM1343, an articulated and nearly complete skeleton including incomplete skull preserved with full dentition.

Discovery

It was collected in the Daxigou site, Jianchang, from the Tiaojishan Formation dated at about 160 million years ago.[3] It was first named by Zhe-Xi Luo, Chong-Xi Yuan, Qing-Jin Meng and Qiang Ji in 2011 and the type species is Juramaia sinensis.[4]

Evolution

The discovery of Juramaia provides new insight into the evolution of placental mammals by showing that their lineage diverged from that of the marsupials 35 million years earlier than previously thought.[4] Furthermore, its discovery fills gaps in the fossil record and helps to calibrate modern, DNA-based methods of dating the evolution.[5][6] Based on climbing adaptations found in the forelimb bones, it has been suggested that the basal stock of Eutheria was arboreal,[4] in a manner resembling that of modern rats.[7]

Classification

See also

References

  1. ^ Juramaia sinensis - 160-Million-Year-Old Fossil Pushes Back Mammal Evolution
  2. ^ Welsh, Jennifer (24 August 2011). "Skinny 'Shrew' Is Oldest True Mammal". LiveScience. Retrieved 5 December 2017.
  3. ^ Chu, Z.; He, H.; Ramezani, J.; Bowring, S.A.; Hu, D.; Zhang, L.; Zheng, S.; Wang, X.; Zhou, Z.; Deng, C.; Guo, J. (2016). "High-precision U-Pb geochronology of the Jurassic Yanliao Biota from Jianchang (western Liaoning Province, China): Age constraints on the rise of feathered dinosaurs and eutherian mammals". Geochemistry, Geophysics, Geosystems. 17: 3983–3992. doi:10.1002/2016GC006529.
  4. ^ a b c "A Jurassic eutherian mammal and divergence of marsupials and placentals" (PDF). Nature. 476: 442–445. 25 August 2011. doi:10.1038/nature10291. PMID 21866158. Archived from the original (PDF) on 10 November 2013. {{cite journal}}: Unknown parameter |authors= ignored (help); Unknown parameter |deadurl= ignored (|url-status= suggested) (help) Electronic supplementary material
  5. ^ "Fossil redefines mammal history" BBC News
  6. ^ Discovery of a 160-million-year-old fossil represents a new milestone in early mammal evolution
  7. ^ "Forelimb Kinematics of Rats Using XROMM, with Implications for Small Eutherians and Their Fossil Relatives". PLoS ONE. 11 (3): e0149377. 2 March 2016. doi:10.1371/journal.pone.0149377. PMC 4775064. PMID 26933950. {{cite journal}}: Unknown parameter |authors= ignored (help)CS1 maint: unflagged free DOI (link)