The spectacled bear (Tremarctos) is not a ‘bear’ in the LRT

Summary of today’s post:
Convergence is rampant in the clade Carnivora, and elsewhere, too, as longtime readers already know only too well. Even so, the LRT (Fig. 3) lumps and splits them all.

Figure 1. Tremarctos ornatus, the spectacled bear of South America, nests with the South American bush dog (Fig. 2) in the LRT (figure 3).

Figure 1. Tremarctos ornatus, the spectacled bear of South America, nests with the South American bush dog (Fig. 2) in the LRT (figure 3).

Most mammal workers consider the spectacled bear,
South America’s only ‘bear’ (genus: Tremarctos ornatus; Fig. 1), a singular bear, genetically and phylogenetically distinct from all other bears. That’s why I added it to the LRT (Fig. 3), where no taxon stands alone.

Figure 2. The South American bush dog, Speothos, nests with the South American spectacled bear, Tremactos, in the LRT.

Figure 2. The South American bush dog, Speothos, nests with the South American spectacled bear, Tremactos, in the LRT.

Surprisingly,
or perhaps not surprisingly, given their geographic proximity, the South American spectacled bear, Tremarctos (Fig. 1), did not nest with the other bears, like Ursus and Arctodus (Fig.3). Instead it nested with the South American bush dog, Speothos (Fig. 2). One is big, the other not so big.

Figure 2. Tremarctos skull in 3 views.

Figure 2. Tremarctos skull in 3 views.

Both the spectacled bear and bush dog are primitive
to the clade of cats + dogs + hyaenas in the LRT (Fig. 3). So, if you’re counting, that makes three origins for carnivores we call ‘bears’. In that regard ‘bears’ are similar to ‘turtles‘ (2 origins),  ‘whales‘ (2 to 3 origins), ‘diapsids‘ (2 origins) and ‘synapsids‘ (2 origins).

Figure 3. Tremarctos nest with Speothos in this subset of the LRT.

Figure 3. Tremarctos nest with Speothos in this subset of the LRT.

Distinct from prior cladograms,
in the large reptile tree (LRT, 1734+ taxa; subset Fig. 3) the South American ‘bear’ (Tremarctos) nests with the South American bush dog (Spetheos). Both nest at the base of the dog + cat + hyaena clade, several nodes apart from extant bears, like Ursus, and the extinct short-face bear, Arctodus, which arises from the wolverine (Gulo).

Figure 2. Speothos, the South American bush dog, skeleton and in vivo.

Figure 2. Speothos, the South American bush dog, skeleton and in vivo.

Speothos veanticus 
(Lund 1842; up to 75cm in length) is the extant South American bush dog, traditionally considered a basal dog. Here Speothos nests at the base of cats + hyaenas + dogs. Miacis is a similar sister basal to sea lions, both derived from another short-legged carnivore, MustelaSpeothos was first identified as a fossil, then as a living taxon. Webbed toes allow this genus to swim more effectively.

Tremarctos ornatus
(Cuvier 1825) is the extant spectacled bear. Not related to other bears, here it nests with another South American member of Carnivora, Speothos, at the base of cats + dogs + hyaenas + aardwolves.

Figure 6. The South American bush dog, Speothos, nests with Tremarctos, at the base of the cat-dog-hyaena clade in the LRT.

Figure 6. The South American bush dog, Speothos, nests with Tremarctos, at the base of the cat-dog-hyaena clade in the LRT.

This may be a novel hypothesis of interrelationships.
If not please provide the prior citation so I can promote it here. Testing taxa that have never been tested together before is what the LRT does.


References
Cuvier F 1825.  In: Geoffroy Saint-Hilaire E.; Cuvier F. (eds.) Histoire naturelle des mammifères, avec des figures originales, coloriées, dessinées d’après des animaux vivans: publié sous l’autorité de l’administration du Muséum d’Histoire naturelle (50). A. Belin, Pari
Lund PW 1842. Fortsatte bernaerkninger over Brasiliens uddöde dirskabning. Lagoa Santa d. 27 de Marts 1840. Kongelige Danske Videnskabernes Selskab Afhandlinger 9:1-16.
wiki/Bush_dog
wiki/Spectacled_bear

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