Early Primate Evolution

Primate origins stretch back to the Cretaceous, perhaps over 80 MYA (million years ago) (Martin, 1993, 2000 Tavare et al., 2002). The date is just a prediction, but one that happens to coincide, very roughly, with the appearance of a significant number of angiosperms in the fossil record. It is not very clear what early flowering plants looked like. However, evidence from exceptionally well-preserved sites suggest that early dicotyledonous angiosperms (dicots for short) were predominantly...

Record

As already noted above, the earliest known unequivocal fossil primates are of basal Eocene age (about 55 MYA), and the standard view is that primates originated no earlier than about 65 MYA, close to and probably above the K T-boundary, with their initial radiation following the extinction of the dinosaurs at the end of the Cretaceous. Although the molecular evidence, when calibrated with various fossil dates outside the primate tree, consistently indicates that the lineage leading to living...

Behaviors

In the early 1970s, Hiiemae and Kay analyzed jaw movements during chewing, tooth occlusal morphology and tooth wear in treeshrews, galagos, squirrel monkeys and spider monkeys (Hiiemae and Kay, 1972, 1973 Kay and Hiiemae, 1974). They concluded that primates share a similar pattern of jaw movement during chewing with a trend toward increased crushing and grinding in anthropoids.6 Hiiemae (1978) went on to argue that mammals, including primates, share a broadly similar pattern of jaw-muscle...

Eye Size and Shape

Figure 5 plots axial eye diameter against head and body length in extant primates and other mammals. Nocturnal primate eyes have larger axial diameters than most similarly sized nonprimate mammals. Tarsiers have longer eyes relative to body size than any other mammals. Axial diameter of the eye scales with negative allometry across all diurnal and nocturnal mammals, except Table 1. Reduced major axis (RMA) regression statistics Table 1. Reduced major axis (RMA) regression statistics AD axial...

Convergence Between Opossums And Primates Experimental Studies

In the previous section, we stressed the importance of testing the causal link between morphology and behavior. More than 25 years ago, Kay and Cartmill (1977) made a similar point, arguing for the need to understand the mechanical relationship between a trait and its function. Kay (1984) cautioned sequence on the right shows a short-tailed opossum losing its balance as it begins to move quadrupedally (A), rolling sideways (B, C), and ending upside-down (D). Despite being three times heavier,...

Selection For Precociality In Early Primates

An important related question is why the early primates were precocial. What are the selective contexts in which precociality seems to be favored in mammal evolution A key here appears to be some component or components of the arboreal environment. It has been noted previously that arboreal, gliding, and flying mammals generally have small litter sizes of relatively well-developed young (Luckett, 1980 Martin, 1969). Meier (1983) demonstrated that arboreality was correlated with longer...

Remarks On Scenarios Of The Acquisition Of Nails

In the initial formulation of the visual predation theory, Cartmill (1972, 1974a,b) explained the acquisition of the opposable hallux by the ancestral primate and the subsequent loss of claws in several groups of primates by the invasion of the fine branch milieu. It is usually now accepted that the possession of nails on the extremities is also a part of the primate morphotypic condition. Recent comparative and functional studies of arboreal primates and marsupials went further in the study of...

The Fossil Record

Before proceeding any further, it is necessary to draw a crucial distinction between the time of initial divergence of a given group, such as the primates, and the age of the last common ancestor of all known, diagnosable members of that group (Figure 1). In a phylogenetic tree, the initial time of origin of any given taxon is indicated by the point of divergence between that taxon and its most closely related sister taxon (node 1 in Figure 1). Initially, the taxon of interest might diverge...

Facial Torsion and the Evolution of the Primate Postorbital

Based on the galago strain-magnitude data, it appears that the primate postorbital bar is overbuilt to resist masticatory stresses. Thus, there is more than enough cortical bone to provide rigid lateral orbital margins. Perhaps once ossified (for whatever nonmasticatory function), the postorbital bar must Figure 4. Average directions of for the left postorbital bar during mastication on the working (L) and balancing (R) side (adapted from Ravosa et al., 2000b) (Table 2). The line A marks the...

Phylogenetic Implications Primate Origins And Adaptations

Plesiadapiformes have long been considered an archaic radiation of primates (Gidley, 1923 Gingerich, 1975, 1976 Russell, 1959 Simons, 1972 Simpson, 1935b,c Szalay, 1968, 1973, 1975 Szalay et al., 1975, 1987). In the last 30+ years, many researchers have questioned a plesiadapiform-euprimate link and have suggested removing plesiadapiforms from the primate order (Beard, 1989, 1990, 1993a,b Cartmill, 1972 Gingerich and Gunnell, 2005 Gunnell, 1989 Kay et al., 1990, 1992 Martin, 1972 Wible and...

Other Characters and Conclusion

Progress in the interpretation of paromomyid cranial characters engendered by the discovery of new and well-preserved specimens has been discussed earlier. The discovery of a tympanic ring and an annular bridge in Ignacius (Bloch and Silcox, 2001) lends considerable support to the link between Plesiadapis and Ignacius advocated by Kay et al. (1992). It is thus very likely that, like paro-momyids, plesiadapiforms (excluding microsyopids) are not closely related to dermopterans. However, the more...

Parallelism And Primitiveness

After parallelisms have been identified, a final critical point that must be addressed is to distinguish specializations from the primitive condition for a group. The close resemblance between food procurement in Daubentonia and Dactylopsila does not imply that ancestral primates or phalangeroids were specialists on wood-boring larvae, because these are convergent specializations generated well after the origins of primates and phalangeroids. The many ecomorph parallelisms suggested by this...

Ecological Correlates of Primate Metabolic Variation

Although primates do not significantly differ from other mammals in the scaling of body mass and metabolic rate, there is considerable variation within the order. Haplorhines, as a group, have a scaling relationship similar to other mammals. In contrast, strepsirrhines are hypometabolic and have a scaling relationship that markedly deviates from that of haplorhines and other mammals. Indeed, all strepsirrhine species have RMRs lower than those predicted for body mass based on the Kleiber...

Sample And Methods

We obtained information on body mass (kg) and RMR (kcal day) for 41 primate species, including 17 species of strepsirrhine and 24 species of haplorhine from published sources, from which we calculated a single unweighted average for each species (Table 1). All RMR values are expressed as kilocalories per day (kcal day) and were converted from other units when necessary. Data on brain mass (g) and body mass (kg) for 15 strepsirrhine species and 21 haplorhines were obtained from Bauchot and...

Acknowledgments On Mammals

We thank Matt Ravosa and Marian Dagosto for inviting us to participate in the Primate Origins Conference, and in this volume. This research was supported by a grant from NSF Physical Anthropology to C.F. Ross (SBR 9706676) and a grant from the L.S.B. Leakey Foundation to C.P. Heesy. Mark Coleman alerted us to important papers documenting the relationship between auditory and visual acuity, and read and provided comments on the manuscript. Allman, J., 1977, Evolution of the visual system in the...

Transitions Leading Up To The Archontan And Euprimate Locomotor Strategies And Substrate Preference

I will not belabor the platitude that the postcranial record of Mesozoic eutherian or other mammals is still relatively poor, and that such a state of affairs makes for very tentative conclusions regarding locomotor adaptations in the stems of various higher taxa within the Eutheria, Metatheria, and Theria the latter restricted here to the concept of monophyletically tri-bosphenic mammals . There is certainly overwhelming evidence that the extant Metatheria had a specifically arboreal ancestry,...

Jaw Muscle EMG and Jaw Morphology in Treeshrews and Primates

Belanger's treeshrews, greater galagos and ring-tailed lemurs are more similar to each other in jaw-muscle EMG activity patterns as compared to this anthropoid sample. Given this broad resemblance, we find it worthwhile to ask whether treeshrew jaw morphology is also more similar to strepsirrhines than anthropoids. If so, then we can extend the associations among jaw-muscle activity patterns, inferentially internal jaw forces, and jaw form observed in comparisons of the primate suborders to...

Evolution of Lysozymes in Colobine Monkeys

Lysozyme is a ubiquitous bacteriolytic enzyme found in virtually all animals. Its function is to cleave the P 14 glycosidic bonds between N-acetyl glu-cosamine and C-acetyl muramic acid in the cell walls of bacteria. As it is present in body fluids, such as saliva, serum, tears, etc., it is often the first line of defense against foreign bacteria. In foregut fermenters, which are animals whose anterior part of the stomach functions as a chamber for bacterial fermentation of ingested plant...

Critical Primate Adaptations

Neglecting the petrosal bulla and a few other pedantries of uncertain adaptive significance, there is widespread agreement that some of the most important shared primate attributes reflecting something about the adaptive context of primate origins include the following 1 grasping hands and feet with nails rather than claws, and locomotion utilizing diagonal footfall patterns, 2 notable development of functional stereoscopy through orbital convergence, 3 large brain relative to body size, and 4...

Likelihood Versus Bayesian Results

Given that Bayesian methods are relatively new in phylogenetics, it is reassuring that independent Bayesian runs with the full data set resulted in trees that are topologically identical to each other and to the maximum likelihood tree when analyses were performed under the GTR r I model of sequence evolution. Maximum likelihood bootstrap percentages were generally lower than Bayesian posterior probabilities. The observation that bootstrap support proportions are lower than Bayesian posterior...

Primate Superior Colliculus In Attention And Action

With the cortical projections to the superior colliculus, this account of primate brain specializations comes full circle. The SC, an ancient structure involved in the control of eye, head, and forelimb movements through its descending projections, is also the linchpin of the highly derived forebrain systems of primates involved in visuospatial attention and vision for action. As we have seen, the SC is in a critical position to influence a wide array of cortical areas by means of its ascending...

Dorsal Pulvinar And Related Cortical Networks

The largest component of the thalamus in anthropoid primates is called the pulvinar, a structure composed of several major divisions, usually termed the inferior, lateral, medial, and oral anterior pulvinar nuclei Gutierrez et al., 2000 . This terminology is generally not used in nonprimate mammals, although it is clear that at least some components of the primate pulvinar have homologues in other mammals. The anterior pulvinar of primates is related to the somatosensory system, and may be...

Eye Shape Measures

On the basis of the dioptric principles outlined in the Introduction, visually dependent nocturnal animals are predicted to have large pupils relative to focal length, and visually dependent diurnal animals are predicted to have small pupil diameters for their focal lengths. These dimensions cannot be measured accurately in preserved eyes and are known for only a small number of vertebrates e.g., Arrese, 2002 Hughes, 1977 Martin, 1999 . Here, we use the axial diameter of the eye as a surrogate...

Skull Characters and Conclusion

The study of paromomyid skulls underscores the difficulty of interpreting partial and distorted specimens. Studying a crushed skull of Phenacolemur jepseni showing parts of the middle ear, Szalay 1972 inferred the presence of a petrosal bulla, in agreement with his hypothesis of a petrosal bulla in Plesiadapis Szalay, 1969 . He also tentatively suggested that the base of a ridge on the promontorium continuous with a longitudinal septum could house a bony canal for a promontory artery Szalay,...

Derived Features Of The Mrca

There are a number of characteristics of the postcranium that are hypothesized to distinguish the MRCA of primates from other mammals even though most have been modified in some groups of primates , and most importantly from the most likely sister taxon of Primates, whether that be some member of the Plesiadapiformes, the Scandentia, or the Dermoptera. A partial list of these characters, their presumed mechanical implications and probable biological roles is given in Table 1. As noted by many...

Miniature Flower Specialists

Sussman 1991, 1995, 1999 suggested that the key ecological factor leading to the origin of primates was adaptation to the utilization of angiosperm products fruit and flowers at the tips of terminal branches. There is still some question as to whether one particular food item was crucial in the evolution of the earliest primates, or whether primate adaptations are better seen as related to a general exploitation of terminal branch resources. The presence in Australasia of several independent...

Likelihood and Bayesian Analyses with the Full Data

Rabbit Pika Cladogram

Figure 1 shows a maximum likelihood cladogram -ln likelihood 211,110.54 for the 16.4 kb data set under the GTR r I model of sequence evolution. Caniform Pangolin Flying fox Rousette fruit bat Rhinolophoid bat Phyllostomid microbat Free-tailed bat Hedgehog Shrew Mole Mouse Rat Hystricid Caviomorph Sciurid Rabbit Pika Flying lemur Tree shrew Strepsirrhine Human Sloth Anteater Armadillo Tenrec Golden mole s. e. elephant shrew l. e. elephant shrew Aardvark Sirenian Hyrax Elephant Opossum...

Taxonomy

The order Scandentia is represented by the single family Tupaiidae, which includes the subfamilies Ptilocercinae and Tupaiinae Table 1 . Ptilocercinae is represented only by Ptilocercus lowii, while Tupaiinae consists of Tupaia 14 species , Dendrogale 2 species , Urogale everetti, and Anathana ellioti see Table 1 Wilson, 1993 . Differences in postcranial morphology are often split down the subfamilial line, as Ptilocercus' postcranium is adapted for arboreal locomotion, while that of the...

Section I Supraordinal Relationships of Primates and Their Time of Origin

Despite new fossil discoveries, new sources of data, and new methods of analysis, several important issues concerning the origin and phylogeny of Primates remain unresolved. One currently controversial issue is the time of origin of the Order Primates. Both the analysis of molecular data Springer et al. and mathematical modeling Soligo et al. suggest a time of origin in the middle of the Cretaceous period 80-90 MYA , while the earliest fossil record of primates is only 55 MYA. The fossil record...

References

Bader, R, and Hall, J., 1960, Osteometric variation and function in bats, Evol. 14 8-17. Beard, K. C., 1990, Gliding behaviour and palaeoecology of the alleged primate family Paromomyidae Mammalia, Dermoptera . Nature 345 340-341. Beard, K. C., 1993, Phylogenetic systematics of the Primatomorpha, with special reference to Dermoptera, in F. Szalay, M. Novacek, and M. McKenna, eds., Mammal Phylogeny Placentals, Springer-Verlag, New York, pp. 129-150. Beard, K. C., Qi, T., Dawson, M. R., Wang, B.,...

Form

The Nocturnal Visual Predation Hypothesis NVPH argues that in the first modern primates, a shift to nocturnal visual predation on small invertebrates and vertebrates necessitated more anteriorly directed and medially approximated orbital apertures and eyeballs Figure 6A Cartmill, 1970, 1972, 1974, 1992 also Collins, 1921 . This increased orbital convergence in turn results in a larger binocular field for greater stereoscopic vision, as well as an exceptionally clear retinal image during...

Metabolic Variation in Strepsirrhines and Haplorhines

Metabolic rates in the strepsirrhines are significantly lower than those predicted by the Kleiber scaling relationship, averaging 38.6 4.7 below the norm Table 1 . The range of predicted values for strepsirrhines is from -1.52 to -69.22 below those predicted by the Kleiber scaling relationship, and 14 of the 17 strepsirrhine species are hypometabolic by criteria described above i.e., gt 20 below predicted by Kleiber scaling relationship . Euoticus elegan-tulus, Galago moholi, and Galago...

Primate Taxonomy Plesiadapiforms and Approaches to Primate Origins Silcox M T

Problems with Combining Cladistics and Linnean Taxonomy Phylogenetic Taxonomy's Solutions to the Problems Posed by Linnean Taxonomy Other Taxonomic Priorities Previous Definitions and Diagnoses of Primates The Phylogenetic Position of Plesiadapiformes Background A More Comprehensive Analysis Taxonomic Implications of the Current Analysis Primate Taxonomy and the Study of Euprimate Origins Conclusions Acknowledgments References

Nocturnal Visual Predation and the Evolution of Orbit Orientation and the Postorbital

The interspecific analyses indicate that the presence of a postorbital bar is correlated with greater orbital convergence in herpestids and pteropodids, and with increased orbital frontation in felids and herpestids. Therefore, moderate support is provided for the NVPH's prediction about orbital convergence, as well as our suggestion regarding the influence of orbital frontation. As both orbital parameters increase during euprimate origins Cartmill, 1970, 1972, 1974, 1992 Fleagle, 1999 Martin,...

Micromomyid Skeleton An Example from a Late Paleocene Limestone

We are in the process of preparing a block, originally 20 kg in mass, of fossil-iferous limestone from the last zone of the Clarkforkian land-mammal age Cf-3, locality SC-327 see Bloch and Boyer, 2001 for locality information . One amazing aspect of this rather large block is that all of the exposed skeletons, representing at least 11 individuals, are articulated 80-100 complete see Bloch and Boyer, 2001, Figure 5 . At least one of the individuals is a new genus and species of micromomyid...

Contributors

Bloch, Florida Museum of Natural History, University of Florida, Gainesville, FL 32611-7800 Douglas M. Boyer, Department of Anatomical Sciences, Stony Brook University, Stony Brook, NY 11794-8081 Matt Cartmill, Department of Biological Anthropology and Anatomy, Duke University Medical Center, Durham, NC 27710 Marian Dagosto, Department of Cell and Molecular Biology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611-3008, and Department of Zoology Mammals...

Introduction

Due to the wide range of morphological variability within and among major primate clades, the circumorbital region has long been the focus of functional and phylogenetic investigations. As is well known, all euprimates differ from their putative ancestors in having the more derived character state of a bony postorbital bar along the lateral orbital margins extending between the frontal and jugal bones Cartmill, 1970, 1972, 1974, 1992 Fleagle, 1999 Matthew J. Ravosa Department of Cell and...

Data Sets

Elpidophorus Teeth

The synthetic treatment of very large data sets by Simmons 1993 and Silcox 2001 is very interesting. Simmons searched for all possible morphological characters studied in the literature, established in 10 presumably mono-phyletic units Scandentia, Strepsirhini, Tarsiiformes, Anthropoidea, Galeopithecidae, Megachiroptera, Microchiroptera, Plesiadapidae, Paromomyidae, and Micromomyidae . The most striking result of her analysis is that, in partitioning the data set into six different subsets...

Treeshrew Feeding Ecology and Jaw MorphologyA Reasonable Early Primate Model

Treeshrews represent an enigmatic group of small mammals that have bewildered primatologists for over a century. This confusion persists in part because of our poor understanding of treeshrew ecology. Emmons 2000 has provided a much-needed field study of treeshrew behavioral ecology. Emmons 2000 emphasizes that the ecological diversity among treeshrew species makes it difficult to summarize the behavioral ecology of the order. Among treeshrews there are nocturnal and diurnal species, montane-...

Problems with Combining Cladistics and Linnean Taxonomy

The Linnean system of taxonomy is based on hierarchically internested sets of ranks. Common membership in a group indicated by a particular taxonomic name is shown by common usage of that name for the members of the group therefore, all mammals are included in Mammalia. Although this may seem trivial, the result is that the taxonomy communicates a hypothesis about common group membership and, in an evolutionary context, common descent. The result is that Linnean taxonomic names can and often do...

Returning To Tupaiidae

When Luckett's 1980a book on tree shrews was published, plesiadapiforms were considered by all the contributors primitive primates. This was a relatively broad, though not unanimous, consensus. It is very interesting to examine how the elimination of the Plesiadapiformes from primates affects our interpretation of certain characters. Surprisingly, this elimination renders a whole series of derived characters possible synapomorphies of tupaiids and primates. Figure 5 illustrates how the...

Primate Origins Role Of Autopod Evolution

Studies of primate skeletal remains from the Eocene epoch of North America and Europe have brought to light several derived features of the autopod that distinguish primates from their close relatives the plesiadapiforms, der-mopterans, and tree shrews. This discussion of derived autopod features is restricted to the digital rays and does not include a discussion of the carpus and tarsus, as the morphology of these bones in early primates has been dealt with elsewhere e.g., Dagosto, 1988 Gebo,...

Molecular Classification For The Living Orders Of Placental Mammals

The well-resolved molecular tree that we present provides a basis for classifying the living orders of placental mammals Table 5 . Following McKenna and Bell 1997 , we used mirorder, grandorder, superorder, magnorder, cohort, supercohort, and infralegion as successively more inclusive taxonomic ranks above the rank of order. Our classification includes clades that have been recognized in previous classifications, although in many cases these have not been recognized with formal Linnaean ranks....

Phylogenetic Influences on Strepsirrhine Hypometabolism Comparative Metabolic Data

From our previous analyses, it appears that proximate ecological factors do not provide a full explanation for strepsirrhine hypometabolism. Consequently, we next considered whether the distinctive metabolic pattern of strepsirrhines is a primitive trait that is shared with other closely related mammalian species. To evaluate this explanation, we considered metabolic data for selected nonprimate species Figure 3 . In the two studies of RMR in tree shrews that were conducted under standardized...

Methods

As described above, several possible neural mechanisms exist to correct for minor eye displacements. These mechanisms, when combined with voluntary and reflexive eye and head movements in a conscious subject, pose problems for measuring eye movements due to masticatory muscle contractions. We attempted to circumvent these difficulties by measuring eye movements in anesthetized subjects. The Institutional Animal Care and Use Committee at Stony Brook University approved animal procedures. The...

Ds Walking And Arboreal Locomotion

When the hindfoot strikes down in a typical DS gait, it lands just behind the forefoot on the same side Figure 3B, no. 6 which is why the unilateral bipod of support is so small Figure 3B, no. 7 . In a tree that hindlimb will be landing on the same support as the forefoot. The animal has already put weight on its forefoot on this support, and so it knows that the support is safe. If the next foot to descend namely, the diagonally opposite forefoot Figure 3B, no. 8 lands on an insecure support...

Peculiarities Of Primate Gaits

The order Primates in the strict sense Euprimates or primates of modern aspect is defined by a familiar suite of synapomorphies. Some of these may represent adaptively neutral contingencies for example, the formation of the auditory bulla by an outgrowth from the petrosal, rather than by a separate entotympanic bone . However, others appear to be telling us things about the basal adaptations of the order. Compared to primitive placental mammals, primates have a reduced sense of smell and an...

Plesiadapiforms as Claw Climbing Arborealists

Plesiadapiforms

Plesiadapiform taxa included in the families Carpolestidae, Micromomyidae, Paromomyidae, and Plesiadapidae are similar to each other in many postcranial Figure 2. A Composite drawing of micromomyid plesiadapiform skull and skeleton UM 41870 with numbers on bones corresponding to those of anatomical layout. Scale 1 cm. Figure 2. A Composite drawing of micromomyid plesiadapiform skull and skeleton UM 41870 with numbers on bones corresponding to those of anatomical layout. Scale 1 cm. Figure 2....

Important Tarsal Characters

A series of tupaiid tarsal characters were interpreted by Szalay and Drawhorn 1980 as derived as opposed to primitive archontan retentions astragalus with the groove for the tendon of M. flexor digitorum fibularis aligned parallel to the long axis and located upon a ventrally projecting medial body length of the astragalus relatively large in contrast to the squat bones in Paleogene archontans sulcus astragalus not approaching the trochlear groove for the tendon of M. flexor fibularis this may...

Carpolestidae

Placental Marsupial Phalanges

Insights into the behavior of the Carpolestidae are derived primarily from a single specimen of the Late Paleocene taxon, Carpolestes simpsoni Bloch and Gingerich, 1998 . The specimen is fairly complete Figure 3C and the dental associations are well documented Bloch and Boyer, 2001, 2002b . Carpolestes is unique among plesiadapiforms in having a foot that is better adapted for powerfully and precisely grasping small diameter supports, a UAJ that reflects even more freedom of motion, a humerus...

Orbital Convergence

Orbital Convergence

Primates have long been noted to have more convergent orbital apertures than most other mammals. Early explanations related convergence to arbore-ality Elliot Smith, 1924 Le Gros Clark, 1959 Wood Jones, 1916 . However, comparisons with other animals suggested to Cartmill 1970, 1972 that convergent orbits facilitated visual predation on insects in the fine branches of the shrub layer of tropical rainforests. Cartmill argued that Stereoptic integration of the two visual fields improves the...

Specializations Of The Visual System Overview

Ventral Dorsal Color Motion

Discussion of visual system evolution requires a very brief review of the anatomy of the visual system for more details, see especially Kaas and Huerta, 1988 Kaas et al., 1978 . Visual information reaches the brain by way of projections from the ganglion cells of the retina. Retinal ganglion cells are of several types, with different morphologies and physiological properties. Currently, three main classes of ganglion cells are distinguished, usually called M, P, and K cells in primates. This...

Reproductive Strategies and Primate Evolution

Precocial Mammal

Research has indicated that one primary input to the encephalization levels observed in primates and other mammals relates to reproductive and life history strategies. It is necessary to review our general understanding of these mammalian and primate reproductive strategies prior to assessing these associations with encephalization, however. Building directly on previous work by Adolf Portmann 1939, 1965 , Martin 1972, 1973, 1975a,b noted that mammalian reproductive strategies could be...

Preservational Bias In The Fossil Record

Continental Positions Middle Miocene

There are several reasons why the preservation rates calculated by Foote et al. 1999 are likely to be overestimated. These all relate to the problem of circularity when interpreting the completeness of the fossil record through analysis of the fossil record alone. First, methods for assessing the completeness of the fossil record based exclusively on the fossil record can only account for gaps that occur within known lineages. They are insensitive to the existence of larger gaps, both...

Dorsolateral Prefrontal Cortex

Primation And Charactrs Picture

By convention, neuroscientists recognize two broad divisions of primate frontal cortex, the motor zone, which consists of the primary motor area M1 and a variety of premotor areas, and the prefrontal zone, which comprises the remainder of the frontal cortex. The prefrontal zone can be divided into a medial region consisting mainly of anterior cingulate cortex , an orbital region, and a dorsolateral region. The dorsolateral prefrontal cortex DLPFC has long been a region of special interest to...

Fossils Methods and Primate Origins

In any attempt at deciphering primate origins within archontans, we should never forget the significance of 1 the divergence of skull form in paro-momyids, plesiadapids carpolestids and 2 a divergent, cross specialized, and continuous record of dentitions, which further eliminates plesiadapiforms from any ancestral role in primate origins. The primatomorph hypothesis is dentally impossible, and cranially very unlikely. The carpolestid hypothesis Bloch and Boyer, 2002 is as dentally impossible...

Orbit Size And Shape

Nodal Distance Eye

Small-bodied nocturnal primates have long been noted to have larger orbital apertures than small-bodied primates of the same skull length Kay and Cartmill, 1977 Heesy and Ross, 2001 Kay and Kirk, 2000 Walker, 1967 . These differences in orbital aperture dimensions may reflect several aspects of eye size and shape Kirk, 2004 Ross, 2000 . The dioptric principles underlying the relationship between eye shape and activity pattern are illustrated in Figure 3. Nocturnal animals live in scotopic, or...

Encephalization in Extinct Primates

Are the primates of the Paleogene the period of the Early Tertiary comprising Paleocene, Eocene, and Oligocene epochs also generally highly encephalized This question must be addressed in relative fashion as well. Almost all mammalian lineages with substantial fossil records show varying degrees of progressive increase in encephalization throughout the Tertiary Gould, 1975a Jerison, 1973 therefore, any determination of relative brain size in extinct early primates must of necessity be rooted in...

Functional Morphology of the Primate Masticatory Apparatus

What we know about how primates chew and the relationship between form and function of their masticatory apparatus comes from three seemingly disparate research agendas. The earliest and hence most enduring efforts have been made by scientists, dentists, and physicians focused on advancing applied dentistry and related medical fields e.g., Ahlgren, 1966 Bennett, 1908 Carlsoo, 1952 DuBrul, 1988 Gibbs et al., 1971 Lindblom, 1960 Linden, 1998 Moller, 1966 . A second group of researchers have...

Plesiadapiform Specializations A Diversity of Arboreal Behaviors

Despite the large amount of similarity between the four groups of plesiadapiforms considered here, each is also unique in its own way. In some cases, morphological differences are probably engendered by size extremes that change the nature of the arboreal milieu experienced by a given taxon. In other cases, these features truly represent specialized behaviors beyond clinging and claw climbing on large diameter vertical supports and the ability to grasp smaller supports with the hands and feet....

Major Clades of Placental Mammals

Our analyses extend studies with the Murphy et al. 2001b data set and provide robust support for four major clades of placental mammals Afrotheria, Xenarthra, Euarchontoglires, Laurasiatheria . We also find robust support for a Euarchontoglires Laurasiatheria clade i.e., Boreoeutheria Springer and de Jong, 2001 . Sequences for a 1.3 kb segment of the apolipoprotein B gene also recover these clades Amrine-Madsen et al., 2003 . In addition, Waddell et al. 2001 argued for these clades based on...

Summary

Encephalization Coefficient

These preceding discussions may be summarized through the development of a four-input framework, which accounts for the key elements and variance in relative brain size within the primates, and between primates as a whole and other mammalian groups. This framework is summarized schematically in Figure 10. First, there is the grade shift linked to strong precociality and small body size in early primate evolution Figure 10, arrow 1 . Second is the primate-wide phylogenetic trajectory, exceeding...

Interpretations of the Masticatory Apparatus in the First Primates

The topic of primate origins has a long history of discussion. We will not review this vast literature. Readers interested in such an appraisal should direct their attention to both earlier publications and recent reviews that consider the origin of primates in their appropriate historical context e.g., Cartmill, 1974 Cartmill, 1992 Jones, 1917 Kay and Cartmill, 1977 Le Gros Clark, 1959a,b Martin, 1993 McKenna, 1966 Smith, 1924 Sussman, 1991 Szalay, 1968 . Instead, we will review references to...

Overview Of Phalangeroid Phylogeny

Until recently all marsupials were usually classified in the indisputably mono-phyletic order Marsupialia, but scientific certainty being what it is to taxono-mists, this tidy order has now been cleaved into a controversial array of ordinal level classifications some of which utilize more than a half dozen orders Aplin and Archer, 1987 Archer, 1984 Ride, 1964 Szalay, 1993, 1994 . A currently popular ordinal designation for the particular marsupials under consideration in this paper is...

Scaling Principles And Subsequent Primate Evolution

I have argued above that early primates were unusual mammals in combining small body size and a highly precocial reproductive strategy, and that these factors were related to their evolution of large relative brain size. But this was merely the foundation or initial grade-shift on which further brain size evolution occurred. It is fundamental to our understanding of primate brain evolution to emphasize that this characteristic of the early primates was translated up and elaborated at the larger...

Primate Taxonomy And The Study Of Euprimate Origins

How does this debate over where to draw the primate-nonprimate boundary relate to the study of primate origins For most workers a key issue is the identification of those taxa that are important to elucidating the evolutionary relationships of unquestionable Primates i.e., Euprimates , independent of taxonomy. That is, we need to understand which forms have features that tell us something about the common ancestor of Euprimates, and which more primitive taxa might give us clues about the order...

The Eyes of Basal Primates

There is debate as to the precise ecological significance of the relatively high levels of orbital convergence seen in primates. Cartmill attributes it to selection for nocturnal visual predation Cartmill, 1992 , whereas others associate it with manual manipulation or visual detection of small objects, including fruits, insects, and small branches in a nocturnal rainforest environment Crompton, 1995 Rasmussen, 1990 Sussman, 1991, 1995 . Common to all these models is the relationship between...

Which Was The Most Important Primate Synapomorphy

Primates of modern aspect are characterized by several traits of the skull and postcranium, most notably increased encephalization, olfactory reduction, postorbital bars, larger and more convergent orbits, an opposable hallux, and nails instead of claws on the digits. When, where, how, and why a group of mammals with this distinctive morphology emerged continues to capture the interest of biologists. The past 15 years have witnessed the discovery of numerous well-preserved basal forms and...

Precociality Encephalization And Small Body Size In Early Primate Evolution

I previously have emphasized that an association between precociality and encephalization in mammals has special implications for early primate evolution Shea, 1987 . The summary in Table 3 reveals that small-bodied mammals are typically altricial, while moderate-to-large sized mammals are generally precocial. This is related to the fact that most small mammals are characterized by the live fast and die young strategy of rapid reproductive turnover and high mortality e.g., Promislow and Harvey,...

Phylogenetic Influences on Strepsirrhine Hypometabolism Implications for Subfossil Lemurs

The extant lemurs of Madagascar are diverse in species number, morphological adaptation, and ecology, but there is evidence that this diversity was much larger in the recent past Godfrey and Jungers, 2002 Mittermeier et al., 1994 Simons, 1997 . Known primarily from recent paleontological sites i.e., subfossils , there is evidence for at least 17 species representing at least five families of extinct lemurs Archaeolemuridae, Daubentoniidae, Lemuridae, Megaladapidae, and Palaeopropithecidae...

Problems Of Diagonal Sequence Walks

Diagonal Sequence Pictures

Most primates preferentially employ the DS footfall sequence in walking Hildebrand, 1967, 1985 Prost, 1965, 1969, 1970 Rollinson and Martin, 1981 Vilensky, 1989 Vilensky and Larson, 1989 . The primate preference for DS walks is problematic, because as many people have shown such gaits Figure 2. Continued B variation in the y-axis only walking gaits, duty factor 74 . The Y variable, here called diagonality, represents the percentage of time in the gait cycle by which each fore footfall lags...

Comparison of Treeshrew and Primate Electromyography WB Ratios

Compared to anthropoids, strepsirrhines with unfused symphyses tend to have higher average W B ratios for their jaw muscles during chewing Hylander et al., 2000, 2002 . The deep masseter clearly shows the most Figure 4. Plot of average peak jaw-muscle activities during chewing in treeshrews. On average, most treeshrew jaw muscles peak in two separate groups. The working-side anterior temporalis WAT , working-side posterior temporalis WPT , balancing-side superficial masseter BSM , and...

Taxonomic Implications of the Current Analysis

In light of these results the issue of whether or not to include plesiadapiforms becomes one entirely of taxonomic philosophy. If one wishes to emphasize adaptive cohesiveness there is no question that the euprimate clade is more adaptively cohesive than any grouping that includes plesiadapiforms. The common ancestor at the euprimate node can be reconstructed as possessing a long list of newly derived characters which, together, seem to be associated with improvements to the visual system...

Encephalization in Extant Primates

Mammals Primates Brain Body Plots

Are the living primates truly the most highly encephalized order among extant mammals This is partly a semantic issue, revolving around how one defines most highly encephalized. Stephan 1972 maintained that while high encephalization was obviously characteristic of Homo, it was just as clearly not uniformly true of the entire order. Martin 1973 , Radinsky 1970, 1975 , and others have also shown that primates are not unique in their high level of encephalization. There is considerable overlap...

Relative Brain Size In Primates

Primates Relative Brain Size

There are several key issues that underlie determinations of relative brain size in primate evolution. The first is allometric correction long recognized as necessary due to general patterns of negative allometry or progressive relative diminution of brain size compared to body size in mammals and other vertebrates. Some of the earliest studies of allometry dealt with ontogenetic, interspecific, and phylogenetic scaling of brain size see Gould, 1966 Huxley, 1932 for references . Any number of...

Substrate Use and Cheiridial Morphology A Functional Model

Walking quadrupedally on thin and flexible arboreal supports presents considerable mechanical challenges. While standing on top of a relatively thin cylindrical support, the tendency of the body of the animal is to pitch or roll Cartmill, 1985 . Pitching and rolling will have the tendency to move the body's center of mass away from the margins of the narrow substrate, toppling the animal from the support Figure 5.1 in Cartmill, 1985 . One way to counteract pitching and rolling effects on a thin...

Inferences from Primitive Mammals

A review of the patterns of social organization in those groups of placental mammals that are thought to be primitive and or related to primates also failed to support a harem system as the ancestral pattern for either primates or placental mammals. Very little is known about patterns of social organization in insectivores, but the majority of species exhibit a nonsocial lifestyle M ller and Thalmann, 2000 . Only few species live in social networks. These include the lesser moonrats...

Origin And Evolution Of Primate Social Organization

As it is impossible to investigate the social life of fossil prosimians but see Krishtalka et al., 1990 Plavcan et al., 2002 , a reconstruction of the ancestral condition of primate social organization has to be based on what is known of the biology of extant species. It is widely accepted that the cheirogaleids and the lorisiforms are likely to represent the first primates most closely CharlesDominique and Martin, 1970 Martin, 1972 . The social organization patterns of these primates will...

Discussion

Beginning a step with a protracted glenohumeral joint is but one aspect of the set of behavioral features distinguishing the form of primate quadrupedal locomotion from that of other mammals Larson, 1998, Larson et al., 2000 . Figure 8. Three dimensional plot of functions 1, 2, and 3 of five variable canonical discriminant analysis. Symbols as in Figures 5 and 7. While Smilodectes falls among rodents for functions 1 and 2, along function 3 it is more similar to some marsupials and primates....

Inferences from Strepsirrhine Primates

The hypothesis that ancestral primates lived in dispersed harem systems has recently been rejected on the basis of new data on cheirogaleid and lorisiform social organization M ller and Thalmann, 2000 . If it is assumed that cheirogaleids and lorisiforms approach the ancestral primate condition most closely and that the pattern of social organization that is found most frequently in those two groups is most likely to be representative of the first primates, the hypothesis of a dispersed harem...

Reconstruction of the Ancestral Pattern of Primate Social Organization

The promiscuous systems of the monotremes, didelphids, dasyurids, and insectivores, as well as the spatial monogamy of tree shrews and elephant shrews are very similar to the dispersed multimale multifemale system and the dispersed monogamy found in cheirogaleids and lorisiforms. The spatial aspects of social organization are in fact the same in promiscuous and dispersed polygynandrous systems on the one hand and in spatial and dispersed monogamy on the other hand. The difference is that in...

Models Of Primate Origins A Review

For most of the last century, some of the postcranial characteristics that distinguish primates from other mammals have been linked to arboreality. For example, Smith 1912 proposed that with the adoption of a more arboreal lifestyle, the hand of primates became more prehensile and sensitive, thus replacing the role of the mouth for food collection. In the same vein, Jones 1916 suggested that the retention of an arboreal mode of life from primitive mammals led to a functional differentiation of...

Morphometric Results

Details of the skeletal samples, measurements, and some of the statistical analyses have been reported previously in Lemelin 1996, 1999 . For the purpose of this chapter, the methods and some of the results of these analyses are summarized, in addition to new morphometric results. Five didelphid taxa Monodelphis domestica, Philander opossum, Didelphis virginiana, Marmosa robinsoni, and Caluromys philander and three cheirogaleid taxa Microcebus murinus, Cheirogaleus medius, and Cheirogaleus...

Plesiadapiform Dental Characters and Primate Origins

Many plesiadapiforms have enlarged anterior incisors and a degree of reduction of the posterior teeth, between I 1 and P 4. It seems clear that the increase of the anterior incisor results in a crowding of the following teeth, which leads in many advanced plesiadapiforms to a diastema between the large incisor and the remaining teeth, or to a series of tiny crowded teeth as in carpolestids. Such specializations have commonly been recognized as preventing any possible ancestral relationship...

Paromomyid Postcranials Gliding and Apatemyid Adaptations

Mammals Phalanges

The core of the primatomorph hypothesis developed by Beard 1990, 1991, 1993a,b was the interpretation of paromomyid phalanges and carpal characters as reflecting a gliding adaptation similar to the peculiar finger-gliding adaptation of living colugos dermopterans , and homologous with it. However, several papers since 1990 have raised doubts concerning this interpretation. Krause 1991 questioned the allocation of the isolated middle phalanges to the hand or foot of Phenacolemur however, Beard...

On Postcranial Characters and Archontan Phylogeny

It seems important to comment on the postcranial characters used by Beard 1993a in his phylogenetic analysis. The primatomorph node was considered the most robust, supported by eleven characters one dental and 10 postcranial. Some of these characters may now appear problematic in their definition and distribution. From the first three of them, the humeral ones, two are mentioned as examples. The lesser tuberosity is considered robust and medially protruding in primatomorphs by Beard 1993a ....