Marian Dagosto

Locomotor Adaptations as Reflected on the Humerus of Paleogene Primates

Examination of Paleogene distal humeri and a survey of homologous articulations in living primates allows some anatomical correlation with elbow mechanics and the occurrence of these during specific locomotor behaviors in living species. Claw climbing is postulated to be the ancestral primate locomotor mode from which the ancestral euprimate (strepsirhines and haplorhines) evolved a grasp leaping locomotor pattern. This pattern, which depends on a powerful grasp either during climbing or when landing after a jump, is still the most pervasive form of primate locomotion. Morphological evidence of Paleogene humeri suggest that vertical clinging and leaping behavior derived from grasp leaping at least six times independently.

Implications of postcranial evidence for the origin of euprimates

Abstract Lemuriforms, Tarsius , anthropoids, adapids, and omomyids share numerous derived postcranial features which support monophyly of the Euprimates and indicate that the archaic primate to euprimate transition was marked by a striking reorganization of the skeleton presumably related to a transformation in locomotor behavior. Analysis of the tarsus indicates that the ancestral euprimate differed from its plesiadapiform progenitor in features related to its increased ability to leap and climb using a grasp based on an opposable hallux. Adapids share derived pedal features with the extant lemuriforms, supporting the monophyly of the Strepsirhini. Omomyids, Tarsius , and anthropoids have the primitive condition of these traits.

Evolution of hallucial grasping in the primates

Abstract Homology of the adaptive solutions of grasping, like other attributes of the postcranial skeleton, have long been assumed for marsupials, early eutherians, and euprimates. Evidence is presented which contradicts this view. The origin of grasping is documented and discussed in the order Primates, the semiorder Euprimates, the suborders Strepsirhini and Haplorhini, and the semisuborder Anthropoidea. Grasping may have been primitive in the cohort Archonta, but the euprimate grasp appears to be related not only to climbing but to a saltatory, graspleaping, locomotor mode of the common ancestor. The origin of anthropoid modifications involves a reduced emphasis on the pedal grasp. The “prehallux” hypothesis for the explanation of the sesamoid in the entocuneiform-hallucial articulation of anthropoids cannot be corroborated by either topographical, developmental, or functional evidence.

PRIMATE ORIGINS: Adaptations and evolution

Supraordinal Relationships of Primates and Their Time of Origin.- A Molecular Classification for the Living Orders of Placental Mammals and the Phylogenetic Placement of Primates.- New Light on the Dates of Primate Origins and Divergence.- The Postcranial Morphology of Ptilocercus lowii (Scandentia, Tupaiidae) and its Implications for Primate Supraordinal Relationships.- Primate Origins: A Reappraisal of Historical Data Favoring Tupaiid Affinities.- Primate Taxonomy, Plesiadapiforms, and Approaches to Primate Origins.- Adaptations and Evolution of the Cranium.- Jaw-Muscle Function and the Origin of Primates.- Were Basal Primates Nocturnal? Evidence From Eye and Orbit Shape.- Oculomotor Stability and the Functions of the Postorbital Bar and Septum.- Primate Origins and the Function of the Circumorbital Region: Whats Load Got to Do with It?.- Adaptations and Evolution of the Postcranium.- Origins of Grasping and Locomotor Adaptations in Primates: Comparative and Experimental Approaches Using an Opossum Model.- Evolvability, Limb Morphology, and Primate Origins.- Primate Gaits and Primate Origins.- Morphological Correlates of Forelimb Protraction in Quadrupedal Primates.- Ancestral Locomotor Modes, Placental Mammals, and the Origin of Euprimates: Lessons From History.- The Postcranial Morphotype of Primates.- New Skeletons of Paleocene-Eocene Plesiadapiformes: A Diversity of Arboreal Positional Behaviors in Early Primates.- Adaptations and Evolution of the Brain, Behavior, Physiology, and Ecology.- Start Small and Live Slow: Encephalization, Body Size, and Life History Strategies in Primate Origins and Evolution.- Evolutionary Specializations of Primate Brain Systems.- New Views on the Origin of Primate Social Organization.- Primate Bioenergetics: An Evolutionary Perspective.- Episodic Molecular Evolution of Some Protein Hormones in Primates and Its Implications for Primate Adaptation.- Parallelisms Among Primates and Possums.- Perspectives on Primate Color Vision.

Estimating the body size of eocene primates: A comparison of results from dental and postcranial variables

Estimating body weights for fossil primates is an important step in reconstructing aspects of their behavior and ecology. To date, the body size of Eocene euprimates—the Adapidae and Omomyidae—has been estimated only from molar area. Studies on other primates and mammals demonstrate that body weights estimated from teeth are not always concordant with those estimated from postcranial variables. We derive estimates for Eocene primates based on tarsal bone variables to compare with previously published values derived from dental measures. Stepsirhine-wide, family-level, and subfamily-level models are developed and compared. We also compare the accuracy and precision of dental- and tarsal-based regression models for predicting weight in extant species. Tarsal bone and dental area measures prove to be equally robust in predicting body weight; however, highly disparate estimates are often obtained from different variables. Equations based on lower-level taxonomic groups perform better than more widely based models. However, all equations considered yield fairly large errors, which can affect interpretations of paleoecology. The choice of the more robust prediction is not straightforward.

The oldest known primate skeleton and early haplorhine evolution

Reconstructing the earliest phases of primate evolution has been impeded by gaps in the fossil record, so that disagreements persist regarding the palaeobiology and phylogenetic relationships of the earliest primates. Here we report the discovery of a nearly complete and partly articulated skeleton of a primitive haplorhine primate from the early Eocene of China, about 55 million years ago, the oldest fossil primate of this quality ever recovered. Coupled with detailed morphological examination using propagation phase contrast X-ray synchrotron microtomography, our phylogenetic analysis based on total available evidence indicates that this fossil is the most basal known member of the tarsiiform clade. In addition to providing further support for an early dichotomy between the strepsirrhine and haplorhine clades, this new primate further constrains the age of divergence between tarsiiforms and anthropoids. It also strengthens the hypothesis that the earliest primates were probably diurnal, arboreal and primarily insectivorous mammals the size of modern pygmy mouse lemurs.

Postcranium of Adapis parisiensis and Leptadapis magnus (Adapiformes, Primates)

The late Eocene European adapid Adapis parisiensis shares many postcranial features with the extant Lorisinae, suggesting that it was a nonleaping, slow-moving arboreal quadruped. The slightly older L

The oldest known anthropoid postcranial fossils and the early evolution of higher primates.

The middle Eocene primate family Eosimiidae, which is known from sites in central and eastern China and Myanmar, is central to efforts to reconstruct the origin and early evolution of anthropoid or ‘higher’ primates (monkeys, apes and humans). Previous knowledge of eosimiid anatomy has been restricted to the dentition and an isolated petrosal bone, and this limited anatomical information has led to conflicting interpretations of early anthropoid phylogeny. Here we describe foot bones of Eosimias from the same middle Eocene sites in China that yield abundant dental remains of this primate. Tarsals of Eosimias show derived anatomical traits that are otherwise restricted to living and fossil anthropoids. These new fossils substantiate the anthropoid status of Eosimias and clarify the phylogenetic position of anthropoids with respect to other major primate clades. Early anthropoids possessed a mosaic of primitive and derived traits in their postcranial skeletons, reflecting their derivation from haplorhine ancestors that retained many prosimian-like features.

Foot anatomy, climbing, and the origin of the Indriidae

Abstract Living indriids share a suite of derived osteological and myological features of the foot which are related to three of the most important components of their locomotor repertoire: climbing (primarily on vertical supports), vertical clinging, and leaping. However, the overall structure of the foot bones and musculature reflects the requirements for climbing more than any other behavior. All indriid subfamilies have postcranial morphologies and locomotor behaviors which are derived compared to the probable indriid-lemurid common ancestor. It seems most likely that the ancestral indriid was an “arboreal quadruped” (i.e. lemur-like), not a vertical clinger and leaper.

The distal tibia of primates with special reference to the omomyidae

The morphology of the distal tibia and its joint surfaces is described in the late Eocene European Necrolemur,the middle Eocene North American Hemiacodon,and an omomyid species from the lower part of the Bridger Formation of North America. Necrolemur,like Tarsius,exhibits tibiofibular fusion, although to a less advanced degree. The Bridger omomyids, however, show no evidence of fusion but are similar to galagos in the conformation of this joint. The distal tibia of euprimates is distinguished by several derived features. These correlate with derived features of the astragalus and are functionally related to the abduction of the foot that accompanies dorsiflexion in primates. Tarsius,omomyids, and anthropoids share a suite of features which distinguish them from strepsirhines; these maybe haplorhine synapomorphies, but the polarity of these features is difficult to determine. If they are synapomorphies, abduction accompanying dorsiflexion and movement at the inferior tibiofibular joint were restricted in ancestral haplorhines. In living primates such restriction is associated with small body size and saltatorial locomotion.