and the one from yesterday were prompted by a YouTube video on Bear-dogs (Fig. 1, click to play) featuring such bone-crushing dogs as Epicyon (Fig. 2) considered by bear-dog afficiandos as one of the largest, if not THE largest bear dog.
Turns out Epicyon is not the beardog with the largest skull.
Amphicyon takes the prize (if the scale bars are correct!), but, then again, look, it is no larger than the extant Siberian wolf (Canis lupus, Fig. 2). So why bring up superlatives and ‘bear-dog’ comparisons in PBS videos when Epicyon and Amphicyon are just wolfish genera of wolfish size?
Figure 2. Epicyon compared to Amphicyon,Ysengrinia and Canis lupus, the Siberian wolf. They are all about the same size. Another species of Ysengrinia (jawbone only) is placed upon Y. americana.
Another specimen attributed to Amphicyon,
(A. galushi, Hunt 2003; Fig. 3), nests not with dogs, but with hyaenas, if given the opportunity. That’s the value of the large reptile tree (LRT, 1278 taxa). It provides to every one of its taxa the opportunity to nest anywhere on a huge and growing tree. So, congratulations Amphicyon bear-dog lovers, we have a wastebasket genus here.
But wait… it gets worse.
Figure 3. Amphicyon galuschai nests closer to hyaenas, like Crocuta in the LRT. Drawing from Hunt 2003.
Yet another specimen attributed to Amphicyon
nests not with dogs, nor placentals, but with basal marsupial carnivores known as creodonts or arctocyonids (Fig. 4). We looked at that issue here a year ago. Funny that I chose the outlier to nest the genus. Over the last few days I discovered the convergence in several taxa attributed to this genus by testing other specimens attributed to this genus.
Figure 4. Amphicyon compared to basal marsupial carnivores (Creodonta) including a marsupial specimen mistakenly assigned to Amphicyon to scale. This purported Amphicyon nests with Arctocyon and Thylacinus, two dog-like opossum descendants.
Amphicyon longiramus (Lartet 1836, Blainville 1841; Mid-Miocene to Pliocene, 16–9mya; up to 2.5m; Fig. 3) is the wide ranging bone-crushing, ‘bear-dog’. This is a wastebasket taxon with some specimens (A. longiramus) related to dogs, others (A. galushi) related to hyaenas (maybe that’s where the bone-crushing aspect came in), while still others (lower right above) nesting between Arctyocyon and Thylacinus among the marsupials.
Figure x (added after initial publication). An early borophagine. Arachaeocyon and a larger later one, Borophagus, animated from Wang 1994. Now, those are bone-crushing molars! Note the relatively smaller auditory bulla in the larger genus. Neither have been added to the LRT.
also found felid (cat-like) traits in the skeleton of Amphicyon galuschai (Fig. 3), the specimen that nests with hyaenas here (Fig. 7). “The North American species of Amphicyon (A. galushai, A. frendens, A. ingens) most likely adopted ecological roles similar to the large living felids (in particular, the lion Panthera leo). Their robust skeleton with powerful forelimbs, massive clawed feet, heavily muscled jaws with large canines, and a composite crushing/shearing dentition suggest a mobile predator that most likely stalked and ambushed prey from cover, overpowering its victims through sheer size and strength.”
Figure 5. A large Canis lupus to scale with Amphicyon major.
Amphicyonidae was erected by Haeckel (1886) who thought the clade was more closely related to ursids (bears). Wikipedia reports, “there is increasing evidence that they may be basal caniforms.” Statements like this, even tentative statements like this, suffer from taxon exclusion, a problem that is minimized by the LRT based on its wide gamut of included taxa. Tomiya and Tsend (2016, Fig. 6) suffers distinctly from taxon exclusion.
Figure 6. Tomiya and Tseng 2016 suffers from taxon exclusion. None of the taxa discussed in the text is listed here, and vice versa, other than Miacis, which is ancestral to sea lions, not dogs nor bears nor beardogs in the LRT.
A subset of the LRT
(Fig. 7) brings relationships into clarity because such a wide gamut of taxa are tested and nested in full resolution. Not sure why this continues to be controversial and heretical when it resolves so many long-standing issues in full resolution and includes every option.
Figure 7. Subset of the LRT focusing on Carnivora, a basal placental mammal clade. Note cats and dogs in derived nodes.
One more in this series coming tomorrow
as we nest bears in the LRT, not with dogs, nor with raccoons.
Blainville HM 1841. Osteographie et description iconographique des Mammiferes récentes et fossiles (Carnivores) 1, 2 Paris.
Hunt RM 2003. Intercontinental Migration of Large Mammalian Carnivores: Earliest Occurrence of the Old World Beardog Amphicyon (Carnivora, Amphicyonidae) in North America. Bulletin of the American Museum of Natural History. 279: 77–115. doi:10.1206/0003-0090(2003)279<0077:c>2.0.co;2.
Lartet E 1836. Nomenclature des mammife`res et des coquilles qu’il a trouve´s dans un terrain d’eau douce pre`s de Simorre et de Sansan (Gers). Bulletin de la Société Géologique de France 7: 217–220.
Tomiya S and Tseng ZJ 2016. Whence the beardogs? Reappraisal of the Middle to Late Eocene ‘Miacis’ from Texas, USA, and the origin of Amphicyonidae (Mammalia, Carnivora). Royal Society Open Science. DOI: 10.1098/rsos.160518
Wang X-M and Tedford RH 2008. Dogs: Their Fossil Relatives and Evolutionary History. New York: Columbia University Press, p10-11, 29