- Caenolestinae, lower pm. 4 not developed into a sectorial tooth.
- Palaeothentinae, lower pm. 4 is developed into a sectorial tooth.
- Abderitinae, lower pm. 4 is developed into a sectorial tooth and striated.
Palaeothentinae Sinclair.
(= Epanorthidae Ameghino)
This group or subfamily was established to hold several genera of tiny marsupials with the dental formula
- ? 1 4 3
- ———;
- 4 1 2 3
the lower fourth premolar enlarged into a sectorial tooth; and the molars small and buno-lophodont. From the Deseado beds but one genus of this subdivision has been found, Palaeothentes, designated by Ameghino first Epanorthus then later Palaepanorthus, but as I can see no reason for distinguishing the Deseado species of the genus from those of the Santa Cruz, I have retained the name Palaeothentes.
The genera of this subfamily are distinguished as follows:
Lower Third Premolar
- Palaeothentes 2-rooted, fairly large, equals pm. 4 in height.
- Pilchenia 2-rooted, moderate size nearly equals pm. 4 in height.
- Callomenus 2-rooted, small size much lower than pm. 4.
- Decastris, 1-rooted, vestigal.