Indarctos

Discovery, history and taxonomy

Discoveries

A molar (designated to MNA 1839/km-83) discovered from the Karabulak formation in 1988 was tentatively assigned to Indarctos sp. In 2017 it was re examined and assigned to I. punjabensis. The tooth was found to belong to a young individual, which may be a male, and is the largest tooth known from the species. This might be due to sexual dimorphism since extant male bears are larger than the females.

Species

Indarctos is known from several species spread widely across Eurasia, North America, and North Africa, however, most of them are known from fragmentary remains which leaves us with insufficient knowledge of the anatomy, lifestyle, taxonomy and paleoecology of some species. These species are usually established based on poor remains, where the presence of sexual dimorphism, paleogeographical variation and individual variation is not taken into account, resulting in a number of species whose taxonomic validity is doubted.

The following are some species of this genus:

I. arctoides: This species had an omnivorous diet, and it was ancestral to the later I. punjabensis.

I. punjabiensis: This species is the geologically youngest and last species of Indarctos. It had a wide distribution 6.3–6.5 Ma during the Late Miocene, across Eurasia. It is known from the Karabulak formation of Kazakhstan, to China and the Dhon Pathan formation of Indo-Pakistan. It descended from the earlier I. arctoides, but unlike its ancestor, it was omnivorous and bigger in size. Based on the resemblance of its forelimbs to those of the modern brown bear, it possibly had similar locomotor adaptations. Evolutionary features such as this led to the migration of Indarctos-like bears into North America. At the end of the Late Miocene, Indarctos punjabiensis went extinct as the last species of its genus.

Description

I. arctoides was sexually dimorphic with males weighing 265 kg, while females weighed 137 kg.

Distribution

Some sites and specimen ages:

• Box T Site, Lipscomb County, Texas ~9.3—9.2 Ma.
• Rattlesnake site, Grant County, Oregon ~10.3—4.9 Ma.
• Withlacoochee River Site 4A, Marion County, Florida (Indarctos sp.) ~10.3—4.9 Ma.
• Lufeng, Yunnan, China (I. atticus) ~9—5.3 Ma.
• Yulafli (CY), Thrace, Turkey (I. arctoides) ~9.7—8.7 Ma.
• Batallones-3, Madrid Basin, Spain (I. arctoides) ~11.6—5.3 Ma.

Paleoecology

Enamel δ13C values from fossilised teeth of I. arctoides from Cerro de los Batallones in Spain show that it was an omnivore with a preference for carnivory over herbivory. Dental microwear reveals that I. anthracitis was a specialist that consumed invertebrate prey.

In Kazakhstan, the species I. punjabiensis is known from the Karabulak formation which dates to 6.3–6.5 Ma (Late Miocene). It coexisted with three mustelids (Martes sp., Promeles sp., Plesiogulo crassa Teilhard), three feliforms (Adcrocuta eximia, Hyaenictitherium hyaenoides orlovi, Amphimachairodus kurteni), four perissodactyls (Hipparion hippidiodus, H. elegans, Chilotherium sp., Sinotherium zaisanensis), and six artiodactyls (Cervavitus novorossiae, Procapreolus latifrons, Samotherium cf. irtyshense, Paleotragus (Yuorlovia) asiaticus, Tragoportax sp., Gazella dorcadoides). The climate that Indarctos punjabensis lived in was mild and arid. It was a habitat of wide, open steppes.

In the Late Miocene Litra Formation of Pakistan, I. cf. atticus inhabited an open environment characterised by monsoonal seasonality and the presence of C4 grasses.

References

References

1. (2003). "Shānxī bǎo dé yìndù xióngyīxīn zhǒng". [[Vertebrata PalAsiatica]].
2. (1959). "The Middle Pliocene Mammalian Fauna from Smiths Valley, Nevada". Journal of Paleontology.
3. "Late Miocene Indarctos (Carnivora: Ursidae) from Kalmakpai Locality in Kazakhstan".
4. Abella, Juan. "On the Socio-Sexual Behaviour of the Extinct Ursid Indarctos arctoides: An Approach Based on Its Baculum Size and Morphology". [[PLoS One]].
5. [https://www.academia.edu/387025/El_sistema_de_yacimientos_de_mamiferos_miocenos_del_Cerro_de_los_Batallones_Cuenca_de_Madrid_estado_actual_y_perspectivas Batallones-3 site]
6. Abella J, Valenciano A, Pérez-Ramos A, Montoya P, Morales J (2013) On the Socio-Sexual Behaviour of the Extinct Ursid ''Indarctos arctoides'': An Approach Based on Its Baculum Size and Morphology. PLoS ONE 8(9): e73711. doi:10.1371/journal.pone.0073711
7. (August 2016). "Feeding ecology and habitat preferences of top predators from two Miocene carnivore-rich assemblages". [[Paleobiology (journal).
8. (12 August 2025). "New characterisation of the Late Miocene insular bear Indarctos anthracitis". [[Journal of Mammalian Evolution]].
9. (3 August 2025). "New material of Late Miocene Indarctos (Carnivora, Mammalia) from the Koh-Sulaiman range, South Punjab, Pakistan". [[Historical Biology]].