Category Archives: misc caniformia

Kolponomos: “Beach bear” or a stem-pinniped?

Arctoidea, misc caniformia, Pan-pinnipedia

The enigmatic and unique molluscivorous carnivoran Kolponomos, has been dubbed by the nickname  “the beach bear”. Mostly reconstructed as a true ursid, adapted to live in littoral enviroments, preying on hard-shelled seafood such as molluscs.

But was it really like that? The material of Kolponomos, is well, fragmentary… lacking significant postcranial bones. Althought it is quite likely that it was a littoral molluscivore – judging by the skull and dentition, its ancestry and life appearance remains a bit of a mystery. 

Speculative reconstruction of Kolponomos newportensis as a stem-pinniped.

The part of the body we need to focus on is the skull. None of the upper teeth are preserved, but the mandibular are. The large round-shaped teeth are worn out so much so, that the original unworn structure of the cusps (on mostly molars) is not known. This wearage is an evidence for a durophagous lifestyle in a similar manner to the extant sea otter (Enhydra lutris). However, the skull structure of the two is not so similar. Kolponomos had a very pronounced chin that worked like an anchor in aiding to dislodge the clams tightly stucked to the sea floor, by the upper portion of the skull. This is a different strategy, that is not seen in sea otters or in any mammal alive today. In foraging, Kolponomos enhanced mandibular stiffness over mechanical efficiency. The stiffness of the lower jaw is an ursid trait, unlike that of the sea otter which utilizes the mechanical efficiency.

The foraging strategy of Kolponomos, indicated by its skull morphology. Image source: Tseng ZJ, Grohe ́ C, Flynn JJ. 2016 A unique feeding strategy of the extinct marine mammal Kolponomos: convergence on sabretooths and sea otters.

As of now, the phylogenetic position of Kolponomos is uncertain. If it is indeed not a true ursid, it might be a member of the clade Amphicynodontidae. This group contains sort of “intermediate” forms between the terrestrial arctoids and pinnipeds, so called stem-pinnipeds. This does not mean that Kolponomos is ancestral to living seals, but that it represents an offshoot of the numerous stem-pinnipeds that went their own evolutionary path, leaving no descendants in the present day.

Only recently, new light has been shed on the origins of pinnipeds and their relationship to ursoids and musteloids. With a handful of transitional forms being recognized properly. But still, the phylogenetic position of amphicynodontids can vary based on the research. It might be that in future this family will no longer be in use, when all the taxa in it get a proper phylogenetic position (either a stem-pinniped, stem-ursid or a musteloid…)

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Lonchocyon qiui: New Obscure Hypercarnivorous Caniform

Arctoidea, misc caniformia

Quite recently, in 2023, a new species of a large carnivoran from the Late Eocene of Mongolia was described. The only material known of Lonchocyon qiui is sadly quite fragmentary, with only one hemimandible, c1 (canine), p4 (4th premolar) and m1 (carnassial) being present.

The skull and postcranium is based off of other hypercarnivorous arctoids, that show large resemblance in the morphology of the mandible and therefore, occupied similar ecological niche.

Based on the lower jaw alone, it becomes clear, that this species was a hypercarnivore. That is, it obtained more than 70% of its calories by meat, either hunted on its own or scavenged on. This is indicated by the robust canine, deep jaw, sectorial trigonid of m1 (that is, specialized for shearing) and strongly reduced premolars. But, as authors of the paper state, there are several hypercarnivorous arctoids that posses functional non-reduced p4 (opposed to our species).

One characteristic of Lonchocyon that could be considered “primitive” or unspecialized, is the retention of unreduced post-carnassial teeth (m2, m3) which usually do the crushing job in carnivorans. In other carnivoran hypercarnivores, these teeth tend to be strongly reduced.

Taking it all to consideration, L. qiui, could consume both flesh and hard objects like bone.

Here, a hypothetical skull is shown:

Right now, the question remains: Was Lonchocyon an amphicyonid or a true bear of the subfamily hemicyoninae? It’s not known yet. What is known however, is, that it represents an early offshoot of one of these groups, appearing quite early in their history (Late Eocene).

During the cenozoic, the suborder Caniformia has produced several lineages of carnivores, which cannot be compared to any living caniforms, hence, occupied a niche that either today remains vacant or is taken by a non-caniform. Such example would be the amphicyonids (bear-dogs) or the ursids (true bears) of the subfamily hemicyoninae. Contradictory to the name “bear-dog”, later, more specialized amphicyonids (amphicyoninae, thaumastocyoninae..) show a combination of skeletal traits and articulations rather resembling a mix between a bear and a big cat. Having a tendation to become hypercarnivorous, with the ability to deliver powerful, deep canine bite, combined with well developed pronation-supination movement, one would imagine these predators as solitary, ambush hunters and scavengers, much more like big cats and bears than any canid or hyaena. One representative of these robust carnivores is Ammitocyon:

Does this mean that this is exactly how we can imagine Lonchocyon to look like? Perhaps yes. Until more of its material is found and described it’s hard to tell with absolute certainty how exactly L. qiui was built.

This fascinating caniform remain to remind us of our humble knowledge of the history and evolution of the Caniformia clade, that in the past produced one of the most fearsome mammalian land predators that roamed the whole Afroeurasia and North America.

The reconstruction of Lonchocyon qiui.

Used Literature: