Tuesday, December 19, 2017

[PaleoMammalogy • 2017] A Basal Ursine Bear (Protarctos abstrusus) from the Pliocene High Arctic reveals Eurasian Affinities and A Diet Rich in Fermentable Sugars


Reconstruction of the mid-Pliocene Protarctos abstrusus in the Beaver Pond site area during the late summer. An extinct beaver, Dipoides, is shown carrying a tree branch in water. Plants include blackcrowberry (Empetrum nigrum) with ripened berries along the path of the bear, dwarf birch (Betula nana) in foreground; sweet gale (Myrica gale) carried by the beaver, sedges in water margins, flowering buckbeans along the mounds behind the beaver, and larch trees in distant background.

 Art by Mauricio Antón based on research of this paper
 and with input on plant community from Alice Telka. 

Abstract
The skeletal remains of a small bear (Protarctos abstrusus) were collected at the Beaver Pond fossil site in the High Arctic (Ellesmere I., Nunavut). This mid-Pliocene deposit has also yielded 12 other mammals and the remains of a boreal-forest community. Phylogenetic analysis reveals this bear to be basal to modern bears. It appears to represent an immigration event from Asia, leaving no living North American descendants. The dentition shows only modest specialization for herbivory, consistent with its basal position within Ursinae. However, the appearance of dental caries suggest a diet high in fermentable-carbohydrates. Fossil plants remains, including diverse berries, suggests that, like modern northern black bears, P. abstrusus may have exploited a high-sugar diet in the fall to promote fat accumulation and facilitate hibernation. A tendency toward a sugar-rich diet appears to have arisen early in Ursinae, and may have played a role in allowing ursine lineages to occupy cold habitats.


Figure 2: Right (A) and left (B) lateral views of the skull of Protarctos abstrusus (CMN 54380), composite laser scans of five individual cranial fragments.

Reconstruction of the mid-Pliocene Protarctos abstrusus in the Beaver Pond site area during the late summer. An extinct beaver, Dipoides, is shown carrying a tree branch in water. Plants include blackcrowberry (Empetrum nigrum) with ripened berries along the path of the bear, dwarf birch (Betula nana) in foreground; sweet gale (Myrica gale) carried by the beaver, sedges in water margins, flowering buckbeans along the mounds behind the beaver, and larch trees in distant background.

 Art by Mauricio Antón based on research of this paper
and with input on plant community from Alice Telka.

Xiaoming Wang, Natalia Rybczynski, C. Richard Harington, Stuart C. White and Richard H. Tedford. 2017. A Basal Ursine Bear (Protarctos abstrusus) from the Pliocene High Arctic reveals Eurasian Affinities and A Diet Rich in Fermentable Sugars. Scientific Reports. 7, Article number: 17722. DOI: 10.1038/s41598-017-17657-8


Primitive fossil bear with a sweet tooth identified from Canada's High Arctic
 phy.so/432795810 via @physorg_com
Bears have had a sweet tooth for millions of years  cbc.ca/1.4451466

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