Juramaia

Juramaia Temporal range: ?Early Cretaceous PreꞒ Ꞓ O S D C P T J K Pg N
Restoration
Scientific 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 a therian mammal, possibly a very basal eutherian mammal, known from the Late Jurassic (Oxfordian stage) or Early Cretaceous deposits of western Liaoning, China.^[1] It is a small shrew-like mammal weighing around 15–17 grams (0.53–0.60 oz).^[2]

Discovery

Juramaia is known from the holotype BMNH PM1343, an articulated and nearly complete skeleton including incomplete skull preserved with full dentition.^[2] 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.^[2]

Classification

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.^[2] Furthermore, its discovery fills gaps in the fossil record and helps to calibrate modern, DNA-based methods of dating the evolution.^[4][5] Based on climbing adaptations found in the forelimb bones, it has been suggested that the basal stock of Eutheria was arboreal,^[2] in a manner resembling that of modern rats.^[6]

However, Sweetman et al. (2017) considered Juramaia as a stem therian instead,^[7] and the Late Jurassic dating has been questioned, with King et al. (2020) suggesting that Juramaia may originate from Early Cretaceous based on tip-dating analyses, which would make it contemporaneous to several other known eutherians.^[1]

See also

• Eomaia

References

External links

• 'Jurassic Mother' Found in China: Discovery News Archived 2012-08-18 at the Wayback Machine
• Juramaia sinensis - 160-Million-Year-Old Fossil Pushes Back Mammal Evolution
• Paleobiology Database: Juramaia sinensis

• v
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Eutheria

Kingdom: Animalia Phylum: Chordata Class: Mammalia Subclass: Theria
Synapsida see Synapsida Cynodontia see Cynodontia Mammalia see Mammalia Eutheria see below↓ Eutheria

Eutheria	†Acristatherium? †Ambolestes? †Bobolestes? †Cokotherium? †Durlstodon †Durlstotherium †Endotherium †Eomaia? †Hovurlestes †Hyotheridium? †Indoclemensia †Juramaia? †Montanalestes? †Murtoilestes? †Prokennalestes? †Sinodelphys? †Adapisoriculidae Adapisoriculus Afrodon Bustylus Deccanolestes? Garatherium Namibiodon Remiculus? Sahnitherium? Wyonycteris? †Asioryctitheria Asioryctes Bulaklestes Daulestes Kennalestes Sasayamamylos Uchkudukodon Ukhaatherium †Cimolestidae Acmeodon Alveugena Ambilestes Avunculus Bagalestes Batodon? Betonnia Chacopterygus Cimolestes Didelphodus Gelastops Ilerdoryctes Maelestes? Paleotomus Procerberus Protentomodon Puercolestes Scollardius †Didymoconidae Archaeoryctes Ardynictis Didymoconus Hunanictis Kennatherium Zeuctherium †Horolodectidae Ferrequitherium Horolodectes †Leptictida Gypsonictops Pseudorhyncocyonidae Diaphyodectes Leptictidium Phakodon Pseudorhyncocyon Leptictidae Amphigyion Blacktops Gallolestes Ictopidium Labes Lainodon Leptictis Leptonysson Megaleptictis Myrmecoboides Ongghonia Palaeictops Praolestes Prodiacodon Protictops Wania †Palaeoryctidae Aaptoryctes Aboletylestes Eoryctes Lainoryctes Naranius Nuryctes Ottoryctes Palaeoryctes Pararyctes Pinoryctes Tsaganius †Pantolesta Paroxyclaenidae Dulcidon Euhookeria Fratrodon Kiinkerishella Kopidodon Merialus Paraspaniella Paroxyclaenus Pugiodens Sororodon Spaniella Vulpavoides Pantolestidae Amaramnis Aphronorus Bessoecetor Bisonalveus Bogdia Bouffinomus Buxolestes Chadronia Coriphagus Cryptopithecus Dyspterna Galethylax Gobipithecus Kochictis Oboia Pagonomus Palaeosinopa Pantolestes Pentacodon Thelysia Todralestes †Taeniodonta Alveugena Onychodectes Schowalteria Conoryctidae Conoryctella Conoryctes Huerfanodon Stylinodontidae Chungchienia Ectoganus Psittacotherium Stylinodon Wortmania †Tillodontia Adapidium Azygonyx Basalina Benaius Dysnoetodon Esthonyx Franchaius Higotherium Interogale Kuanchuanius Lofochaius Megalesthonyx Meiostylodon Plesiesthonyx Plethorodon Simplodon Tillodon Trogosus Yuesthonyx †Zalambdalestidae Alymlestes Anchilestes Barunlestes Beleutinus Kulbeckia Zalambdalestes Zhangolestes Zofialestes †Zhelestidae Alostera? Aspanlestes Avitotherium Azilestes? Borisodon Eoungulatum Eozhelestes Gallolestes Kharmerungulatum Khuduklestes? Lainodon Mistralestes? Oxlestes? Paranyctoides? Parazhelestes Sheikhdzheilia Sorlestes Valentinella? Zhalmousia Zhelestes †Pantodonta see Pantodonta Placentalia Afrotheria Boreoeutheria Xenarthra