Mammalia - Panameriungulata - Proterotheriidae

The shape of the molars of Bounodus is similar to that of the Didolodontidae condylarths, a clade endemic to South America and apparently restricted to the Palaeogene. In fact, the majority of younger taxa once referred to this family on the basis of tooth characters are now considered to be litopterns when postcranial remains are known. This is the case of Megadolodus, to which the taxon described here is most closely related, and Neodolodus colombianus Hoffstetter & Soria, 1986, from the Miocene of Colombia. However, the latter was considered to be a junior synonym of Prothoatherium Ameghino, 1902 by Cifelli & Guerrero Diaz (1989: but see Soria 2001). Prothoatherium colombianus shares with Bounodus the absence of strongly lophate cheek teeth, but differs from it in the general shape and minor size of the molars, the broadly developed anterior cingulum on the lingual base of the protocone and the lingual sulcus that separates the protocone and hypocone. Another taxon, Salladolodus deuterotheroides Soria & Hoffstetter, 1983, from the Deseadan (Lower Oligocene) of Bolivia, known from a left M2-3 and considered to be a Didolodontidae (Soria & Hoffstetter 1983), differs from Bounodus in its somewhat smaller size, the peculiar absence of metaconule and the continuity between hypocone and posterior cingulum. Bounodus recalls particularly the large-sized Didolodontidae, such as Paulogervaisia mamma Ameghino, 1901, from the Casamayoran (probably Barrancan) of Patagonia. Although this taxon is known only from fragmentary remains it seems valid (Simpson 1948; Cifelli 1983a; Soria 2001) and not a synonym of Didolodus Ameghino, 1897 (contra McKenna & Bell 1997). Paulogervaisia Ameghino, 1901 (MACN 10719) differs from Bounodus in having M3 with a more rounded contour and smaller in size compared to M2; the more lingually placed hypocone and the separation of this cusp with respect to the protocone. The size inferred for Bounodus based on the inferred P4 suggests it had a greater degree of molarisation than did Didolodontidae. This is observed among the Proterotheriidae Megadolodinae. In this sense, Bounodus shares with Megadolodus molariformis the pres- ence of a bunodont dentition, hypocone in M3 and the very anterior position of the paraconule that tends to interrupt the trajectory of the anterior cingulid. However, it differs by having a rectangular contour of M1 with a more mesial antero-lingual root. In addition, the anterior border of the hypocone in M2 shows a lingual margin of enamel interpreted as the most posterior portion of the protocone; consequently, the hypocone would be more labial with respect to the protocone in Bounodus rather than posterior as in Megadolodus.

Full reference: A. A. Carlini, J. N. Gelfo, and R. Sánchez. 2006. A new Megadolodinae (Mammalia, Litopterna, Protherotheriidae) from the Urumaco Formation (Late Miocene) of Venezuela. Journal of Systematic Palaeontology 4(3):279-284

Parent taxon: Megadolodinae according to A. A. Carlini et al. 2006

Sister taxon: Megadolodus

Subtaxa: Bounodus enigmaticus

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Type: Bounodus enigmaticus

Ecology: scansorial herbivore

Distribution: found only at Urumaco (Miocene of Venezuela)

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Specimen images are retrieved through the ePANDDA API.