Ischyromyid rodents found from the Eocene of Erlian Basin in Nei Mongol

Dec 24, 2013
Fig.1 Occlusal view of the cheek teeth of Asiomys dawsoni. Credit: LI Qian

The ischyromyids are the most primitive rodents that have a Holarctic Paleogene distribution. Members of the family are predominant in Paleogene rodents of North America, but are relatively rare in both Asia and Europe. In a study published in the latest issue of Vertebrata PalAsiatica 51(4), Drs. LI Qian and MENG Jin, Institute of Vertebrate Paleontology and Paleoanthropology (IVPP), Chinese Academy of Sciences, reported some new findings of the Eocene ischyromyids from the Huheboerhe area in the Erlian Basin, Nei Mongol, China. These include Asiomys dawsoni from the basal strata of the Irdin Manha Formation and Ischyromyidae gen. et sp. indet. from the basal strata of the Arshanto Formation. The new materials include fragmentary mandibles and numerous cheek teeth, which provide new evidence for the mammal's dispersal between Asia and North America during the Middle Eocene.

Asiomys is similar to species of both paramyines and reithroparamyines in size. The mandible of Asiomys is similar to that of Paramys delicatus in many features. Dental characteristics of Asiomys are similar to those of paramyines, but quite different from those of reithroparamyines. Researchers tentatively assigned Asiomys to Paramyinae based on the fragmentary mandible and the cheek .

The teeth of Asiomys appear consistent with some evolutionary trends observed in Middle Eocene North America ischyromyids. However, Asiomys differs from other Middle Eocene Asian ischyromyids, such as Anatoparamys, Eosischyromys and Hulgana, in having a small hypocone and two metaconules on upper molars, a complete hypolophid on dp4 and a short hypolophid and a small hypocounulid on lower molars.

Fig.2 Mandible of Asiomys dawsoni. A−C, left mandibular fragment with m2; D−E, left mandibular with p4-m3. Credit: LI Qian

"Because Asiomys is more similar to the North American ischyromyids than to the Asian ones, it provides a new evidence for faunal exchanges between Asia and North America during the Middle Eocene", said first author Dr. LI Qian of the IVPP.

Ischyromyid rodents found from the Eocene of Erlian Basin in Nei Mongol
Fig.3 Occlusal view of the upper cheek teeth of Ischyromyidae gen. et sp. indet. Credit: LI Qian


Explore further: Polacanthine ankylosaur dinosaur first discovered in Asia

More information: Read the study: www.ivpp.cas.cn/cbw/gjzdwxb/xb… 1204403891676383.pdf

add to favorites email to friend print save as pdf

Related Stories

Polacanthine ankylosaur dinosaur first discovered in Asia

Dec 23, 2013

In a study published in the latest issue of Vertebrata PalAsiatica 51(4), Dr. YOU Hai-Lu, Institute of Vertebrate Paleontology and Paleoanthropology (IVPP), Chinese Academy of Sciences, and his collaborators from C ...

Recommended for you

Study sheds new light on the diet of extinct animals

8 hours ago

A study of tooth enamel in mammals living today in the equatorial forest of Gabon could ultimately shed light on the diet of long extinct animals, according to new research from the University of Bristol.

Ancient clay seals may shed light on biblical era

Dec 20, 2014

Impressions from ancient clay seals found at a small site in Israel east of Gaza are signs of government in an area thought to be entirely rural during the 10th century B.C., says Mississippi State University archaeologist ...

Digging up the 'Spanish Vikings'

Dec 19, 2014

The fearsome reputation of the Vikings has made them the subject of countless exhibitions, books and films - however, surprisingly little is known about their more southerly exploits in Spain.

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.