Marsupial sabertooth ancestors back to tiny Early Paleocene Pucadelphys

It’s the complete postfrontal bar
(orange) connected to the jugal that stands out in this clade of narrow-nosed, saber-toothed marsupials, here (Fig 1) shown to scale and enlarged for detail.

Sabertooth placentals don’t have this primate-like trait. Sabertooth marsupials do.

Figure 1. Marsupial sabertooth evolution. Pucadelphys, Hapalodecteis (1VPP V2385), Patagosmilus, Thylacosmilus, Barbourofelis. The latter is traditionally located closer to placental cats. Here a postfrontal is identified in all taxa. ” data-image-caption=”

Figure 1. Marsupial sabertooth evolution. Pucadelphys, Hapalodecteis (1VPP V2385), Patagosmilus, Thylacosmilus, Barbourofelis. The latter is traditionally located closer to placental cats. Here a postfrontal is identified in all taxa.

” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/05/patagosmilus-thylacosmilus588-3.jpg?w=74″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/05/patagosmilus-thylacosmilus588-3.jpg?w=253″ class=”size-full wp-image-86260″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/05/patagosmilus-thylacosmilus588-3.jpg” alt=”Figure 1. Marsupial sabertooth evolution. Pucadelphys, Hapalodecteis (1VPP V2385), Patagosmilus, Thylacosmilus, Barbourofelis. The latter is traditionally located closer to placental cats. Here a postfrontal is identified in all taxa.” width=”584″ height=”2360″ />

Figure 1. Marsupial sabertooth evolution. Pucadelphys, Hapalodecteis (1VPP V2385), Patagosmilus, Thylacosmilus, Barbourofelis. The latter is traditionally located closer to placental cats. Here a postfrontal is identified in all taxa.

Unlike most cat-like predators
these marsupials did not have much binocular vision. Their increasingly oversize canines and roots expanded the central area of the rostrum, pinching off the nasals (pink) between the maxillae (green).

Apparently there were no complaints or shortcomings back then as this lineage survived for tens of millions of years.

Figure 2. Pucadelphys and the IVPP V5235 specimen to scale. ” data-image-caption=”

Figure 2. Pucadelphys and the IVPP V5235 specimen to scale.

” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/05/pucadelphys-hapalodectes-v5235-588.jpg?w=136″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/05/pucadelphys-hapalodectes-v5235-588.jpg?w=466″ class=”size-full wp-image-86255″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/05/pucadelphys-hapalodectes-v5235-588.jpg” alt=”Figure 2. Pucadelphys and the IVPP V5235 specimen to scale. ” width=”584″ height=”1284″ />

Figure 2. Pucadelphys and the IVPP V5235 specimen to scale. Note the primate-like postorbital bar here constructed from the postfrontal.

Little Early Paleocene Pucadelphys also had saber teeth
(Fig 2) and other structures later elaborated in larger descendants. It lacked that slender postorbital postfrontal bar, as in most other marsupials.

According to Wikipedia – Barbourofelis,
“Barbourofelis is an extinct genus of large, predatory, feliform carnivoran mammals.”

By contrast, in the LRT, Barbourofelis is not a cat and not a member of the Carnivora. Instead it is a marsupial sharing more traits with Thylacosmilus (Fig 1).

“The skeletons of juvenile Barbourofelis have been found, and examination of their skeletons indicates that the cubs would reach near-adult size before their milk sabers would begin to erupt. This indicates that they were dependent on their mother or potential family group until well into their second year.”

Or, the sabers were secondary sexual traits, like deer antlers, or deer fangs.

I’d like to promote Randau et al 2013 for more on this hypothesis.

References
Gaillard C, MacPhee, RDE and Forasiepi AM 2023. Seeing through the eyes of the sabertooth Thylacosmilus atrox (Metatheria, Sparassodonta). Nature communications biology https://doi.org/10.1038/s42003-023-04624-5
Randau M, Carbone C, Turvey ST and Evans A 2013. Canine Evolution in Sabretoothed Carnivores: Natural Selection or Sexual Selection?, PLoS ONE, 8 (8) e72868. DOI: 10.1371/journal.pone.0072868.s001
Schultz CB, Schultz MR and Martin LD 1970. A New Tribe of Saber-toothed Cats (Barbourofelini) from the Pliocene of North America. Bulletin of the University of Nebraska State Museum. 9 (1).

scientificamerican.com/b/the-sexy-sabercat-how-the-sabertooth-got-its-teeth/

wiki/Thylacosmilus
wiki/Schowalteria
wiki/Barbourofelis
wiki/Barbourofelidae
wiki/Thylacosmilidae
wiki/Pucadelphys

The wide-set eyes of the marsupial sabertooth, Thylacosmilus

Barbourofelis enters the LRT as a sabertoothed marsupial, not a big cat

SVP 2021 abstracts – 21: Barbourofelis is ‘a unique cat’ because it’s not a cat