Evidence for Dietary Niche Separation Based on Infraorbital Foramen Size Variation among Subfossil Lemurs

Abstract

The size of the infraorbital foramen (IOF) has been used in drawing both phylogenetic and ecological inferences regarding fossil taxa. Within the order Primates, frugivores have relatively larger IOFs than folivores or insectivores. This study uses relative IOF size in lemurs to test prior trophic inferences for subfossil lemurs and to explore the pattern of variation within and across lemur families. The IOFs of individuals belonging to 12 extinct lemur species were measured and compared to those of extant Malagasy strepsirhines. Observations matched expectations drawn from more traditional approaches (e.g. dental morphology and microwear, stable isotope analysis) remarkably well. We confirm that extinct lemurs belonging to the families Megaladapidae and Palaeopropithecidae were predominantly folivorous and that species belonging to the genus Pachylemur (Lemuridae) were frugivores. Very high values for relative IOF area in Archaeolemur support frugivory but are also consistent with omnivory, as certain omnivores use facial touch cues while feeding. These results provide additional evidence that the IOF can be used as an informative osteological feature in both phylogenetic and paleoecological interpretations of the fossil record.

Dental topography indicates ecological contraction of lemur communities

“…consume considerable foliage under certain circumstances (Sussman, 1977; Sauther, 1992; Pinkus et al, 2006; Simmen et al, 2006). Depending on the behavioral criterion applied or the field study consulted, these lemurids can be classified as folivorous or frugivorous (cf., Boyer, 2008; Muchlinski et al, 2011; Bunn et al, 2011; this paper). What is intriguing also is anatomical evidence that they may be poorly adapted for processing those resources upon which they most heavily rely.…”

“… Sources: 1 Burney et al, 1997; 2 Burney et al, 2004; 3 Crowley et al, 2011; 4 Godfrey et al, 1997; 5 Godfrey et al, 2004; 6 Godfrey et al, 2005; 7 Jungers et al, 2002; 8 Muchlinski et al, 2011; 9 Rafferty et al, 2002; 10 Ravosa, 1991; 11 Ravosa, 1992; 12 Ryan et al, 2008; 13 Scott et al, 2009; 14 Seligsohn and Szalay, 1974; 15 Tattersall, 1973; 16 Tattersall, 1982; 17 Vasey et al, in press. …”

“…Eulemur spp. and Lemur catta also resemble Hapalemur (and not Varecia or Pachylemur ) in having relatively small infraorbital foramina, a characteristic of folivorous species (Muchlinski et al, 2011).…”

Why all those spines? Anachronistic defences in the Didiereoideae against now extinct lemurs

“…21,22 However, because most of the lemur species included in our analyses are, or were, predominantly herbivorous, we do not believe our results are confounded by the effects of faunivory on nitrogen isotope values. [23][24][25][26][27][28][29][30][31][32] The two possible exceptions are Archaeolemur majori (whose diet likely included some animal matter) and Daubentonia robusta. Extant D. madagascariensis consumes more animal matter than any of the other lemurs included in our study 33 and it is likely that the extinct D. robusta, which lived in the southwest, would have had a similar diet.…”

“…Four of these (all except Archaeolemur) have a 0% CAM signal, as does subfossil Lepilemur. Of these four, the two Megaladapis species have dental topography much like Lepilemur, 23 as well as relatively small infraorbital foramina 29 and dental microwear 30,56 that suggest dominant foliage consumption.…”