Sabertooth Homotherium relatives in the LRT compared

Sabercat. Sabertooth tiger.
These are iconic tags for placental 1 taxa like Homotherium (Fig 1), Hoplophoneus (Fig 4) and Smilodon (Fig 3). So it comes with some dismay, concern and consternation that these taxa arise in the large reptile tree (LRT, 2340 taxa) not from cats, but from canids. This has been a steady recovery in the LRT for several years, despite attempts to bias scores the other way.

If it’s any comfort, I am likewise surprised and still not comfortable with the recovered cladogram topology. In the LRT cats and sabertooths are convergent in many respects that ALL prior workers and children everywhere consider homologs.

This reminds me of the day that giant paraceratheres left rhinos to join horses in the LRT. Nobody liked that. However, since then nobody has created and recovered another study for confirmation, refutation or modification.

I modify the LRT nearly every day as light is shed on various interrelationships. So I am not adverse to change, nor is there any ego, peer-group pressure or academic fear of shame involved. Of course, scores are always tinged with ‘the human factor’. That I can guarantee.

I am also adverse to “Pulling a Larry Martin“
= attaching great importance to a few to a dozen traits. Rather, the last common ancestor method is used by the LRT to determine interrelationships. And all tested taxa in this subset of the LRT influence cats, canids and sabertooth taxa.

The following images
(Figs 1–4) represent some of the taxa and data surrounding Homotherium (the basalmost sabertooth in the LRT) that I have to work with at present. The long rostrum = muzzle of Homotherium is noteworthy. The disappearance of newly useless premolar teeth following the enlargement of the saber teeth is an observed pattern. The lateral extension of the lower rim of the posterior dentary is seen in Speothos (the extant bush dog) and Homotherium should not be overlooked. A neck longer than the skull is a shared trait between canids and sabertooth.

Other taxa close to canids and sabertooths
include Proteles (the aardwolf) and Crocuta (the hyaena, Fig 2). Gulo, the wolverine, is something of wild card, currently closer to bears. So this clade is not adverse to changing diet, dentition, size, leg length, etc. whereas cats pretty much follow the same blueprint = Bauplan. Some are bigger. Others are smaller. That’s about it.

Whenever canine sabers develop
apparently there is no longer any need for the small anterior premolars found in ancestral taxa. But note in Borophagus (Fig 4) the canine is relatively small and premolar 1 is already absent.

While not sister taxa in the LRT,
the large bush dog, Borophagus has a profile and skull shape seen in the small sabertooth, Hoplophoneus (Fig 4), which lacks the large thumb claw seen in larger Homotherium.

I wish I could diagnose these interrelationships better.
Instead I will have to let these images sooth our anxieties and inspire grad students to figure this out with a similar taxon list.

I promise to let you know if anything changes
on this topic. There is a good case for the sabertooths are cats hypothesis, but the LRT says canids are closer at present.

Source: https://pterosaurheresies.wordpress.com/2026/10/09/sabertooth-homotherium-relatives-in-the-lrt-compared/