Basic Morphology

Indriids have reduced the number of premolars from the standard number of three to two (Table 1), and Daubentonia has a single, peglike upper premolar. The upper premolars vary among the families. In cheirogaleids the first two premolars are bladelike. Among the lemurids and cheirogaleids, P4 has a well-developed proto-cone, though it is not molariform except in Hapalemur (and Lepilemur; Tattersall, 1982). This tooth in L. catta is also broad and molarlike, although with some individual variation, for example the presence of accessory cusps (FC, personal observation). The two indriid premolars are not molariform. The lower anterior premolar is caniniform in all lemurs (Swindler, 2002; Tatersall, 1982). In Hapalemur, P4 is molariform and possesses two distinct basins (Tattersall, 1982).

The mammalian tribosphenic molar pattern has not been greatly modified in the primates as a whole. In the Malagasy lemurs, the lemurids retain the original pattern of three cusps (paracone, metacone, protocone) that surround the trigon basin in the first two maxillary molars (Figure 6). A lingual cingulum is variably present with an anterior protostyle. M3 is reduced but less so in Hapalemur

mesial lingual -►

Figure 6. Occlusal features from casts of upper second molars of (A) Eulemur rubriven-ter (RMNH d) and (B) Propithecus diadema edwardsi (RMNH b). Not to scale (photos by Ny Yamashita).

(Tattersall, 1982). The indriids developed a characteristic quadritubercular maxillary molar that extends to their subfossil members (Martin, 1990). A mesostyle is present on the first two molars. A fourth cusp, the hypocone, and its crests surround a second basin, the talon. The hypocone occludes with the trigonid basin (Figure 6). Other families either completely lack the hypocone or it is variably developed, as in the cheirogaleids (Martin, 1990) and EHapalemur (Tan, 2000). In Daubentonia, the molars are square in outline, though the cusps are not well-defined (Tattersall, 1982).

Generally, lemurids have a more varied molar morphology than indriids (Yamashita, 1998b). In the lower molars, the lemurids have lost the paraconid and lack a hypoconulid. The anterior basin, the trigonid, is tilted mesially and at an angle to the cervical plane of the talonid (Figure 7). The trigonid does not have an occluding cusp. L. catta has a lingual notch and a distinct entoconid on the M2 that are lacking in the other lemurids (except for EHapalemur) that interrupts the continuous crest on the postero-lingual aspect of the tooth. EHapalemur simus has crenulated enamel on both upper and lower molars (Schwartz and Tattersall, 1985).

Lepilemur also possesses a distinct entoconid and pronounced crests radiating obliquely anteriorly and posteriorly from the hypoconid (Schwartz and Tattersall, 1985). In the cheirogaleids, the molars are variable, with all except

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