Two large rodents from the Middle Miocene of Chiang Muan, northern Thailand

Yuichiro Nishioka*, Hideo Nakaya, Kunihiro Suzuki, Benjavun Ratanasthien, Pratueng Jintasakul, Rattanaphorn Hanta, Yutaka Kunimatsu

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Two large rodents from the Middle Miocene (13.0–12.4 Ma) were discovered at the Chiang Muan Coal Mine, northern Thailand. One, a beaver (Anchitheriomys, Castoridae), has large cheek teeth with a high crown, the crown base wider buccolingually, basically six fossettes/sinuses, enamel foldings strongly complicated, and hypoflexus/flexid shallow dorsoventrally. Based on dental morphology, this form is more similar to Anchitheriomys suevicus from Europe than to Anchitheriomys tungurensis from northern China. The other species is considerably larger than Anchitheriomys, based on incisor measurements, and lacks longitudinal grooves or deep ridges on the enamel surface, which are diagnostic of Anchitheriomys. Furthermore, the inner enamel observed by scanning electron microscope has uniserial Hunter-Schreger bands, similar to castorids rather than hystricids. This species is indeterminate taxonomically, but differs from any rodents known from Asia. The distribution of Anchitheriomys was previously restricted between the latitudes 30°N and 50°N, but this occurrence in northern Thailand at low latitude (ca. 19°N) suggests that it had wider distribution on the Eurasian continent.

Original languageEnglish
Pages (from-to)151-158
Number of pages8
JournalHistorical Biology
Issue number1-2
Publication statusPublished - 2016 Feb 17
Externally publishedYes


  • beaver
  • Castoridae
  • Neogene
  • Rodentia
  • Southeast Asia

ASJC Scopus subject areas

  • General Agricultural and Biological Sciences


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