Laurie R. Godfrey

Teeth, brains, and primate life histories

This paper explores the correlates of variation in dental development across the order Primates. We are particularly interested in how 1) dental precocity (percentage of total postcanine primary and secondary teeth that have erupted at selected absolute ages and life cycle stages) and 2) dental endowment at weaning (percentage of adult postcanine occlusal area that is present at weaning) are related to variation in body or brain size and diet in primates. We ask whether folivores have more accelerated dental schedules than do like-sized frugivores, and if so, to what extent this is part and parcel of a general pattern of acceleration of life histories in more folivorous taxa. What is the adaptive significance of variation in dental eruption schedules across the order Primates? We show that folivorous primate species tend to exhibit more rapid dental development (on an absolute scale) than comparably sized frugivores, and their dental development tends to be more advanced at weaning. Our data affirm an important role for brain (rather than body) size as a predictor of both absolute and relative dental development. Tests of alternative dietary hypotheses offer the strongest support for the foraging independence and food processing hypotheses.

Spatial and temporal arrival patterns of Madagascar's vertebrate fauna explained by distance, ocean currents, and ancestor type

How, when, and from where Madagascars vertebrates arrived on the island is poorly known, and a comprehensive explanation for the distribution of its organisms has yet to emerge. We begin to break that impasse by analyzing vertebrate arrival patterns implied by currently existing taxa. For each of 81 clades, we compiled arrival date, source, and ancestor type (obligate freshwater, terrestrial, facultative swimmer, or volant). We analyzed changes in arrival rates, with and without adjusting for clade extinction. Probability of successful transoceanic dispersal is negatively correlated with distance traveled and influenced by ocean currents and ancestor type. Obligate rafters show a decrease in probability of successful transoceanic dispersal from the Paleocene onward, reaching the lowest levels after the mid-Miocene. This finding is consistent with a paleoceanographic model [Ali JR, Huber M (2010) Nature 463:653–656] that predicts Early Cenozoic surface currents periodically conducive to rafting or swimming from Africa, followed by a reconfiguration to present-day flow 15–20 million years ago that significantly diminished the ability for transoceanic dispersal to Madagascar from the adjacent mainland.

GRADUAL, AUTOCATALYTIC AND PUNCTUATIONAL MODELS OF HOMINID BRAIN EVOLUTION - A CAUTIONARY TALE

The tempo and pattern of macroevolutionary change have bearing on current controversies concerning the processes of macroevolutionary change. In this paper we reexamine the evidence for increase in cranial capacity in light of traditional arguments and interpretations, paying special attention to methodological problems inherent in data transformations and manipulations. Despite a large volume of descriptive material published on the subject, there has been relatively little attention paid to testing competing hypotheses of processes of macroevolutionary change (punctuational, gradual, autocatalytic); the descriptions which have emerged often reflect unstated and, perhaps, unrealized a priori assumptions made by researchers. Log-log transformations of cranial capacity versus time are misleading and inappropriate. A uniform pattern of change in hominid cranial capacity is less obvious than generally assumed.

The Early Hominid Plant-Food Niche: Insights From an Analysis of Plant Exploitation by Homo, Pan, and Papio in Eastern and Southern Africa [and Comments and Reply]

African plant-food genera exploited by Homo, Pan, and Papio have been catalogued and analyzed to provide an estimation of the size and composition of the fundamental plant-food niche of the early hominids. Results to date include recognition of more than 100 widely distributed African plant genera which are the best known candidates for plant-food exploitation by the Plio/Pleistocene hominids of eastern and southern Africa. An analysis of staples reveals that fruits would be the most common type of plant part contributing to the early hominid plant-food diet. Six plant genera (four providing edible fruits) are the first genera to be identified as members of the most probable early-hominid fundamental plant-food niche. Potential interspecies competition for plant-food staples has also been estimated. It is highly significant and must be considered in models predicting the realized niche of these primates and the early hominids.

Ecomorphology and Behavior of Giant Extinct Lemurs from Madagascar

Inferring the behavior of extinct organisms is a formidable task, even under the best of circumstances (Rudwick, 1964; Stern and Susman, 1983; Kay, 1984; Thomason, 1995). Nevertheless, and in spite of inevitable complications and limitations, such inferences remain the ultimate goal of paleobiologists if we are to understand fossils as integrated organisms rather than isolated bones and atomized character states. In this chapter we attempt to breathe life back into the osteological remains of recently extinct (or “subfossil”) prosimian primates from the Quaternary of Madagascar. Subfossil lemurs provide many special opportunities to the optimistic functional morphologist, but they also present their own unusual set of complications and potential frustrations. Approximately one-third of Madagascar’s known primate species were driven to extinction in the late Holocene by the lethal interaction of aridification and human colonization (Burney, 1997; Dewar, 1997; Simons, 1997), including all taxa of large body size (> 9 kg). Two new extinct species from northern Madagascar (Babakotia radofilai and Mesopropithecus dolichobrachion) have been discovered and described in the last decade (Godfrey et al., 1990; Simons et al., 1995), and a third new species from the northwest will be diagnosed soon (Jungers et al., in prep.). Sixteen currently recognized subfossil species of Malagasy primates are represented in museum collections, most by numerous individuals, including a growing tally of specimens with associated craniodental and postcranial elements (e.g., MacPhee et al., 1984; Simons et al., 1992,Simons et al., 1995; Wunderlich et al., 1996). Table I summarizes the current taxonomy of the extinct lemurs. Aspects of morphology suggest that cheirogaleids are more closely related to galagos and lorises than to other Malagasy primates (Szalay and Katz, 1973; Cartmill, 1975; Schwartz and Tattersall, 1985; Yoder, 1992). Molecular results, as well as “total evidence” analyses that combine morphological and molecular data, argue instead that the Malagasy primates are probably monophyletic (Yoder, 1994,Yoder, 1996). Regardless of the placement of the cheirogaleids within strepsirrhines, the precise relationships among the various ancient clades of Malagasy primates remain somewhat fuzzy, even from a biomolecular perspective (Yoder, 1997; Yoderet al., 1999).

Dental microstructure and life history in subfossil Malagasy lemurs

When compared with their recently extinct relatives, living lemurs represent a mere fraction of a broad radiation that occupied unique niches in the recent past. Among living lemurs, indrids exhibit the fastest rates of dental development. This dental precocity is tightly correlated with rapid pace of postnatal dental eruption, early replacement of the deciduous teeth, high dental endowment at weaning, and relatively slow somatic growth. This pattern is in stark contrast to that seen in extant lemurids, where somatic development is highly accelerated and dental development is relatively slow. We report on the pace of dental development in one species of palaeopropithecid, the sister group to extant indrids. Like much smaller modern indrids, the chimpanzee-sized Palaeopropithecus ingens was dentally precocious at birth as evidenced by the advanced state of molar crown formation. This finding implies a pattern characteristic of Propithecus and other indrids—rapid dental development despite relatively prolonged gestation. Gestation length in this one species of subfossil lemur was likely greater than 9 months. Our results demonstrate that large body size in primates does not preclude exceedingly rapid dental development.

Past and Present Distributions of Lemurs in Madagascar

Holocene cave, marsh, and stream deposits on the island of Madagascar have yielded thousands of “subfossil” specimens that document recent megafaunal extinctions. Excavations conducted during the past 15 years of archaeological and paleontological sites in northern, northwestern and southwestern Madagascar have unearthed, in addition to new specimens of extinct lemurs and other megafauna, an abundance of bones of still-extant lemur species. These specimens, as well as specimens of extant lemurs from subfossil sites excavated in the early and mid-1900’s, prove that living lemur species once had much broader geographic ranges than they have today, and they help to explain the currently disjunct distributions of a number of species. This paper examines the pattern of distribution of extant primate species at subfossil sites, and compares recent to modern primate communities.

Adaptive Diversification of Malagasy Strepsirrhines

Abstract This overview of the positional behavior and evolutionary history of Malagasy strepsirrhines is based on the humeral and femoral morphology of extinct and extant forms. It argues against the hypothesis that vertical clinging and leaping was ancestral for Malagasy lemurs in general, and for indroids in particular. Special attention is given to the evolutionary history of the Indroidea, and a new interpretation of their relationships is offered. It appears that specialized forms of leaping, as well as specialized slow, quadrupedal climbing, evolved repeatedly within the Malagasy strepsirrhines (i.e., in both Indroidea and Lemuroidea) from a generalized quadrupedal ancestor that would have included a certain amount of leaping and bounding in its positional repertory, but also slow climbing and occasional hindlimb suspension.

New insights into old lemurs: The trophic adaptations of the Archaeolemuridae

Modern tools of paleoecological and ecomorphological research have enabled researchers to reconstruct the lifeways of extinct species more thoroughly than ever before. We apply a variety of tools in an attempt to reconstruct the diets of the extinct archaeolemurids of Madagascar. Our data include dental use wear (examined across species and across ontogenetic series of single species), enamel microstructure, enamel thickness, and δ13C. The data are complemented by field data on the environmental contexts in which the species lived and 14C determinations that demonstrate the surprisingly late survival of archaeolemurids. Several lines of evidence converge to suggest that all archaeolemurid species were hard-object processors, but with different diets and different methods of food processing. Past reconstructions of the diet of Hadropithecus as a specialized grass consumer fail under the scrutiny of multiple lines of evidence.

A glance to the past: subfossils, stable isotopes, seed dispersal, and lemur species loss in Southern Madagascar

The Spiny Thicket Ecoregion (STE) of Southern and southwestern Madagascar was recently home to numerous giant lemurs and other “megafauna,” including pygmy hippopotamuses, giant tortoises, elephant birds, and large euplerid carnivores. Following the arrival of humans more than 2,000 years ago, dramatic extinctions occurred. Only one‐third of the lemur species which earlier occupied the STE survive today; other taxa suffered even greater losses. We use stable isotope biogeochemistry to reconstruct past diets and habitat preferences of the recently extinct lemurs of the STE. We show that the extinct lemurs occupied a wide range of niches, often distinct from those filled by coeval non‐primates. Many of the now‐extinct lemurs regularly exploited habitats that were drier than the gallery forests in which the remaining lemurs of this ecoregion are most often protected and studied. Most fed predominantly on C3 plants and some were likely the main dispersers of the large seeds of native C3 trees; others included CAM and/or C4 plants in their diets. These new data suggest that the recent extinctions have likely had significant ecological ramifications for the communities and ecosystems of Southern and southwestern Madagascar. Am. J. Primatol. 73:25–37, 2011.