Hapalodectes hetangensis  (Ting and Li 1987; 4.5cm skull length; Paleocene, 55 mya; IVPP V 5235) This skull was originally considered a mesonychid, but here nests with the marsupial clade leading to sabertooth taxa with a shrinking premaxilla. Note the encircled orbits rotated anteriorly as in Thylacosmilus, convergent with primates.

Patagosmilus goini (Forasiepi and Carlini 2010) is a large sabertooth marsupial from the Middle Miocene of South America traditionally considered a sister to the more famous sabertooth from South America, Thylacosmilus. After testing Patagosmilus nests with Early Cretaceous Vincelestes.

Thylacosmilus atrox (Riggs 1933; Miocene, 40-3 mya; 1 m long) was a leopard-like predator, but plantigrade. Derived from a sister to Hapalodectes. The premaxillary teeth are absent here, perhaps lost during taphonomy. The canines are enlarged to curved fangs. Their roots extend above the orbits. The dentary has ventral processes that guide and protect them. The lower canines are round stubs. Tiny lower incisors appear between them. The coronoid process is small, indicating a wide, but weak bite.

Barbourofelis fricki (Schultz, Schultz and Martin 1970; Middle to Late Miocene, 13-7mya) was traditionally considered a placental member of the Carnivora and a big cat (= Feliformia). Here it nests with Thylacosmilus as a saber-toothed marsupial. The premaxilla has four procumbent tooth alveoli. The three large molars have shearing surfaces, as in big cats, not grinding surfaces. The premolars are tiny. The sabers are slender, as in Thylacosmilus. The orbit is enclosed, as in Thylacosmilus. The mandible (= dentary) must hyper extend in order to clear the sabers.

Forasiepi AM and Carlini AA 2010. A new thylacosmilid (Mammalia, Metatheria, Sparassodonta) from the Miocene of Patagonia. Zootaxa. 2552, ss. 55–68, 2010 (Ing.)

Riggs EC 1934. A new marsupial saber-tooth from the Pliocene of Argentina and its relationships to other South American predacious marsupials. Transactions of the

Schoch RM 1986. Systematics, functional morphology and macroevolution of the extinct mammalian order Taeniodonta. Bulletin of the Peabody Museum of Natural History, Yale University, New Haven. 307pp.

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).

Ting S and Li C 1987. The skull of Hapalodectes (?Acreodi, Mammalia), with notes on some Chinese Paleocene mesonychids. Vertebrata PalAsiatica. 25: 161–186.

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