Succeeding the Eemian or the Last Interglacial, the Last Glacial period (115, 000 -11, 000 years ago) began. It is a well known fact, that during this time, cave bears (Ursus ex. gr spelaeus) were widespread in Eurasia. This lineage was closely related to recent brown and polar bears. Althought rivaling their extant relatives in terms of dimensions (and on average being heavier), cave bears were specialized herbivores. It can be deduced from numerous factors (isotope analysis, tooth microwear…). There is no doubt they would be a formidable adversary when confronted with our ancestors.
My reconstructions and size chart of several forms of cave bears present in Europe during the Last Glacial.
Cave bears (Ursus ex. gr spelaeus) were very diverse, with different forms living on different localities and having different prefences (altitude and perhaps also plant types..). In central and eastern Europe, Ursus ingressus was one of the largest forms, occupying habitats below the ranges of the smaller, high alpine subspecies such as Ursus spelaeus ladinicus and Ursus spelaeus eremus.
As it has been found, U. ingressus and U. s. eremus were living sympatrically for 15,000 years in Austria, with no apparent interbreeding. This is an evidence, that they must have niche partitioned and were quite different ecologically.
There were also a lot of different forms. For example, the classical Ursus spelaeus spelaeus was found in western Europe.
The brown bears (Ursusarctos) lived alongside cave bears, but were more carnivorous than they are today. This was to avoid competition.
Originally thought to be a wolverine-like animal, (Plesiogulo relative) then viewed as an amphicynodontine ursoid and the third time, we might got it entirely correct… Drassonax harpagops was one of the first definitive ursids (true bear).
Drassonax is a genus with just incomplete remains preserved, like upper maxillary teeth and lower jaws. The only known basal ursoids (ursoids include the Ursidae as well as forms already showing ursid traits but still not belonging to the family) with preserved whole skeletals (therefore giving us much more clues about their anatomy and biology) are Amphicynodon and Eoarctos. Based on dental characteristics, Drassonax appears to be a close relative of the former.
My reconstruction of Drassonaxharpagops, one of the early basal ursids. In life it would resemble a small agile predator like a marten rather than modern bears.
Here is a rough hypothetical sketch of how could the skull of Drassonax look like. The proportions are based off of close relatives such as Amphicynodon and Campylocynodon.
The first true caniforms very likely evolved in North America, as it’s indicated by the oldest and most primitive forms of both arctoids (bear and musteloid ancestors) and cynoids (canids) appearing there as early as in the middle Eocene, and in the case of the first ursoids, the genus Subparictis in the Late Eocene during the Chadronian land mammal age, approximately 38-33 million years ago.
They all started out as largely very active mesocarnivores of rather compact dimensions with adaptations for arboreal or scansorial lifestyle. Drassonax likely possesed great climbing and grasping abilities, also being able to rapidly accelerate. As with its close relative Amphicynodon, it is possible that also Drassonax could reverse its feet, perhaps even up to 180°. This would enable it to descend and ascend trees headfirst.
Perhaps one of the best still-living examples of these small carnivorans that we can compare to our extinct species, in terms of ecology is the enigmatic african palm civet (Nandinia binotata). As well as with others, they resemble the ancestral body plan of the earliest arctoids that all others subsequently evolved from.
Baskin, J. A., and R. H. Tedford. 1996. 24. Small arctoid and feliform carnivorans; pp. 486–497 in D. R. Prothero and R. J. Emry (eds.), The terrestrial Eocene-Oligocene transition in North America, Part II: Common vertebrates of the White River Chronofauna. Cambridge University Press, Cambridge.
