Locomotor Specializations Research Articles

Forelimb skeletal morphology and flight mode evolution in pelecaniform birds

The total length and mid-shaft diameters of wing elements of 50 species of pelecaniform birds were examined to investigate how forelimb skeletal morphology varies with body size and flight mode within this group. Pelecaniforms were assigned to flight mode categories based on primary habitual behaviors (soar, flap-glide, continuous flap). Allometric and discriminant function analyses were conducted on wing element variables in both historical (using independent contrasts) and ahistorical contexts. Results of this study indicate that when phylogenetic relationships are taken into account, only the length of the ulna scales with positive allometry, whereas all other variables exhibit isometry. These results differ from the ahistorical allometric analysis. Discriminant function analysis (DFA) significantly separated the flight mode groups (Wilk's lambda=0.002, p<0.00001), with only six individuals from two species (out of n=284) misclassified. Results of historical canonical variates analysis supported the ahistorical DFA and identified two carpometacarpal (CMC) variables as important for separating the flight mode groups: dorsoventral CMC diameter and total CMC length. The carpometacarpus is that portion of the forelimb skeleton that serves as the attachment point for the primary flight feathers, and thus, that portion of the airfoil surface that mediates detailed flight control. Its morphology, more than any other element, reflects differences in flight mode in pelecaniforms. Results of this study indicate that, in pelecaniforms, wing bones generally exhibit isometry (with the exception of the ulna) and do possess specific morphologies reflective of the demands associated with different types of aerial locomotor specialization.

Evolution of archosaurian body plans: skeletal adaptations of an air‐sac‐based breathing apparatus in birds and other archosaurs

AbstractLiving birds represent the only extant sauropsid group in which pulmonary air sacs pneumatize the postcranial skeleton. Notable in this regard is an extraordinary degree of variability, ranging from species that are completely apneumatic to those characterized by air within the entire postcranial skeleton. Although numerous factors (e.g., body size) have been linked with “relative” pneumaticity, comparative studies examining this system remain sparse. This project sought to (1) characterize whole‐body patterns of skeletal pneumaticity in distantly related neognath birds and (2) evaluate putative relationships among relative pneumaticity, body size and locomotor specializations. Pneumaticity profiles were established for 52 species representing 10 higher‐level groups. Although comparisons reveal relatively conserved patterns within most lower‐level clades, apparent size‐ and locomotor‐thresholds do impart predictable deviations from the clade norm. For example, the largest flying birds (vultures, pelicans) exhibit hyperpneumaticity (i.e., pneumaticity of distal limb segments) relative to smaller members of their respective clades. In contrast, skeletal pneumaticity has been independently lost in multiple lineages of diving specialists (e.g., penguins, auks). The application of pneumaticity profiling to extinct archosaurs reveals similar trends in body size evolution, particularly when examining patterns of pneumaticity in a size‐diverse assemblage of pterosaurs (flying “reptiles”). As a fundamental organizing system, skeletal pneumaticity may play a role in relaxing constraints on body size evolution by allowing volumetric increases without concomitant increases in body mass. Not only might this be critical for taxa (birds, pterosaurs) exploiting the energetically costly aerial environment, but could be beneficial for any large‐bodied terrestrial vertebrates such as the dinosaurs.J. Exp. Zool. 311A:629–646, 2009. © 2009 Wiley‐Liss, Inc.

Convergences in Scapula Morphology among Small Cursorial Mammals: An Osteological Correlate for Locomotory Specialization

Small cursorial mammals, such as lagomorphs, elephant shrews, and the more cursorial caviomorph rodents, share both the similar locomotor gait of rapid half-bounding and a similar scapula anatomy of a long, slender, caudally projecting metacromion process. This scapular morphology is also present in some notoungulates (extinct endemic South American ungulates), in rabbit-like taxa such as Propachyruchos. In the rabbit Oryctolagus this elongated metacromion process serves to increase the moment arm of the acromiotrapezius and levator scapulae ventralis muscles, which we propose may aid in scapula stabilization and resisting ground reaction forces during the landing phase onto a single forelimb in half-bounding. A long, slender metacromion process is thus an osteological correlate of locomotor specialization, that of rapid half-bounding in small to medium-sized mammals.

Functional significance of the uncinate processes in birds

The functional significance of the uncinate processes to the ventilatory mechanics of birds was examined by combining analytical modeling with morphological techniques. A geometric model was derived to determine the function of the uncinate processes and relate their action to morphological differences associated with locomotor specializations. The model demonstrates that uncinates act as levers, which improve the mechanical advantage for the forward rotation of the dorsal ribs and therefore lowering of the sternum during respiration. The length of these processes is functionally important; longer uncinate processes increasing the mechanical advantage of the Mm. appendicocostales muscle during inspiration. Morphological studies of four bird species showed that the uncinate process increased the mechanical advantage by factors of 2-4. Using canonical variate analysis and analysis of variance we then examined the variation in skeletal parameters in birds with different primary modes of locomotion (non-specialists, walking and diving). Birds clustered together in distinct groups, indicating that uncinate length is more similar in birds that have the same functional constraint, i.e. specialization to a locomotor mode. Uncinate processes are short in walking birds, long in diving species and of intermediate length in non-specialist birds. These results demonstrate that differences in the breathing mechanics of birds may be linked to the morphological adaptations of the ribs and rib cage associated with different modes of locomotion.

The Evolutionary and Developmental Basis of Parallel Reduction in Mammalian Zeugopod Elements

Understanding the mechanisms by which parallel evolution occurs has the potential to clarify the complex relationship between evolution and development. In this study, we examine the role of development in the repeated reduction of zeugopod elements during mammalian evolution, a functionally important phenomenon enabling locomotor specialization. By completing a morphometric study (incorporating both analyses of variation and phylogenetics) of mammalian limbs, we are able to demonstrate an evolutionary trend toward width reduction in posterior zeugopod elements of the forelimbs and hindlimbs, the ulna and fibula, respectively. We also examine the developmental basis of limb reduction in three test cases, the bat Carollia perspicillata ulna and fibula and the mouse Mus musculus fibula. The most common pattern of reduction, that of reduced element width, was achieved via the same developmental process in both bat and mouse limbs (i.e., by a slower growth rate relative to other skeletal elements), suggesting that the parallel reduction of the posterior zeugopod element within mammals could have occurred primarily by the repeated evolution of the same developmental mechanism. However, our findings also suggest that the developmental mechanisms behind the parallel evolution of other, more taxon-specific characteristics of limb reduction (i.e., element fusion) are not conserved.

Analyse morphologique et fonctionnelle du pelvis des primates Catarrhiniens : conséquences pour l'obstétrique

Morphological and functional analysis of the pelvis in Catarrhines: consequences for obstetrics. The study aimed at connecting obstetrical adaptations in Catarrhines with (1) locomotor specializations in the pelvic cavity, and (2) neonate encephalization. The material comprised 49 pelves, 18 skulls of adult females, and 9 neonate skulls. The neonate dimensions were placed in the pelvic inlet, midplane and outlet (mean pelvic shape obtained by Procrustes superimposition) and compared with adult dimensions. The results showed that non-human primates possess simple obstetrical mechanics that may present some difficulties, either because the fetus is proportionally large ( Hylobates), or because locomotor specializations reduce the pelvic dimensions ( Papio). Humans have complex obstetrical mechanics, resulting from bipedalism and parturition interactions. Encephalization did not play a determinant role in the evolution of human obstetrics. To cite this article: J. Bouhallier, C. Berge, C. R. Palevol 5 (2006) .

La bipédie des Oiseaux, facteur déterminant de leur réussite adaptative

The birds are flying animals but they are also basically bipeds. The theropod dinosaurs, precursors of the birds, were already cursorial bipeds. Because the body structure was modelled by aerodynamical constraints during the evolution, all birds, even those that do not fly anymore, share a typical avian body shape. The osteological differences between birds are more adjustments than deep disruptions. Nevertheless, the birds are very diversified in their way of life and habitat. Yet, the hind limbs of the birds are surprisingly efficient in many manners, such as taking off, landing, swimming and walking. The limb structures adaptability to the various tasks require different mechanical fitness or device such as shock absorber during landing, or thrusters during tacking off. Moreover, almost all birds can walk, even if they have another locomotor specialization, as swimming or flying. Depending on the specialization, the gait features of the walk and the kinematics pattern are slightly modified. The functional adaptability of their hind limb structure may be a key to the evolutive success of the birds.

CONSTRAINTS ON THE MORPHOLOGICAL EVOLUTION OF MARSUPIAL HOULDER GIRDLES

Throughout their evolutionary histories, marsupial mammals have been taxonomically and morphologically less diverse than their sister taxa the placentals. Because of this, it has been proposed that the evolution of marsupials has been constrained by the functional requirements of their mode of reproduction. Marsupials give birth after short gestation times to immature neonates that immediately crawl, under the power of their precociously developed shoulder girdles, to the teat where they attach and complete their early development. Using a novel approach incorporating adult and embryological morphological data, this study is the first to both: (1) statistically support adult patterns of morphological divergence consistent with the constraint hypothesis, and (2) identify ontogenetic patterns of morphological change that demonstrate that the constraint was responsible, at least in part, for their formation. As predicted by the marsupial constraint, the shoulder girdles of adult marsupials are less diverse than those of adult placentals, and adult marsupial scapulae are less morphologically diverse than adult marsupial pelves. Furthermore, marsupials that complete an extensive crawl to the teat are restricted to a common pattern of ontogenetic scapular shape change, strongly supporting the hypothesis that the morphological development of the marsupial scapula has been limited evolutionarily by its obligate role in the crawl to the teat. Because this study establishes that ontogenetic and evolutionary morphological change is correlated within mammalian scapulae, it is probable that the marsupial constraint also restricted the morphological divergence of the scapula over evolutionary time by limiting ontogenetic change in the scapula. These findings, coupled with the importance of the shoulder girdle in mammalian locomotor specialization, support the conclusion that the low morphological diversity of marsupial forms over evolutionary time could be directly due to the constraint on marsupial morphological evolution caused by the functional requirements of the crawl to the teat.

CONSTRAINTS ON THE MORPHOLOGICAL EVOLUTION OF MARSUPIAL SHOULDER GIRDLES

Throughout their evolutionary histories, marsupial mammals have been taxonomically and morphologically less diverse than their sister taxa the placentals. Because of this, it has been proposed that the evolution of marsupials has been constrained by the functional requirements of their mode of reproduction. Marsupials give birth after short gestation times to immature neonates that immediately crawl, under the power of their precociously developed shoulder girdles, to the teat where they attach and complete their early development. Using a novel approach incorporating adult and embryological morphological data, this study is the first to both: (1) statistically support adult patterns of morphological divergence consistent with the constraint hypothesis, and (2) identify ontogenetic patterns of morphological change that demonstrate that the constraint was responsible, at least in part, for their formation. As predicted by the marsupial constraint, the shoulder girdles of adult marsupials are less diverse than those of adult placentals, and adult marsupial scapulae are less morphologically diverse than adult marsupial pelves. Furthermore, marsupials that complete an extensive crawl to the teat are restricted to a common pattern of ontogenetic scapular shape change, strongly supporting the hypothesis that the morphological development of the marsupial scapula has been limited evolutionarily by its obligate role in the crawl to the teat. Because this study establishes that ontogenetic and evolutionary morphological change is correlated within mammalian scapulae, it is probable that the marsupial constraint also restricted the morphological divergence of the scapula over evolutionary time by limiting ontogenetic change in the scapula. These findings, coupled with the importance of the shoulder girdle in mammalian locomotor specialization, support the conclusion that the low morphological diversity of marsupial forms over evolutionary time could be directly due to the constraint on marsupial morphological evolution caused by the functional requirements of the crawl to the teat.

Evolutionary correlations between escape behaviour and performance ability in eight species of snow skinks (Niveoscincus: Lygosominae) from Tasmania

AbstractThree locomotor modes were examined (sprinting, jumping and climbing) in eight species of skinks: seven Niveoscincus spp. and Pseudemoia entrecasteauxii. These species formed four distinct ecological types: ground‐dwelling, arboreal, heath/rock dwelling, and saxicolous. Significant behavioural preferences for particular escape modes in the field were found, which reflected the performance capabilities at an animal in the laboratory. This study used both non‐phylogenetic and evolutionary based analyses to demonstrate that species occupying different microhabitats and using different escape tactics exhibit corresponding differences in performance abilities. Four Niveoscincus species are specialized in performance abilities and behavioural responses (N. greeni, N. ocellatus, N. pretiosus, N. orocryptus) by excelling in some performance abilities but having behavioural restrictions at attemping other locomotor modes. Only N. microlepidotus and N. orocryptus used escape tactics opportunistically; these species possess a suite of behavioural responses that may reflect the wide range of microhabitats they occupy. Ground‐dwelling species N. metallicus, N. coventryi and Pseudemoia entrecasteauxii performed poorly at all performance abilities and seemed to have biomechanical limitations, rather than behavioural restrictions, on locomotor mode. Thus, when making interspecific comparisons, the behaviour of an animal needs to be considered before appropriate performance measures are selected. Phylogenetic analyses demonstrate that escape tactics and performance abilities have co‐evolved in Niveoscincus, with an evolutionary trend towards behavioural and locomotor specialization.

Land-to-sea transition in early whales: evolution of Eocene Archaeoceti (Cetacea) in relation to skeletal proportions and locomotion of living semiaquatic mammals

Skeletal remains of Eocene Archaeoceti provide the only direct and unequivocal evidence of the evolutionary transition of whales from land to sea. Archaeocete skeletons complete enough to be informative about locomotion are rare (principally Rodhocetus and Dorudon), and these deserve to be studied in comparison to the full spectrum of semiaquatic mammals. A principal components analysis of 14 trunk and limb measurements for 50 species of living semiaquatic mammals reduces the observed variation to three informative axes. The first principal axis (PC-I) represents overall size (water mice and shrews have the lowest scores on this axis and the hippopotamus has the highest); the second axis (PC-II) represents a spectrum of aquatic adaptation (seals have the lowest scores and tapirs have the highest); and the third principal axis (PC-III) represents a spectrum ranging from hindlimb- to forelimb-dominated locomotion (sea otters have the lowest scores and the platypus the highest).Dorudon fits poorly into a morphospace defined solely by living semiaquatic mammals; thus a second 53-species set was analyzed, adding an anthracothere to represent an artiodactyl ancestral morphology and two species of archaeocetes to represent successive stages of early whale evolution. This addition has little effect on the first two principal axes but changes the third substantially. PC-III now represents a contrast of lumbus- (and presumably tail-) dominated versus hindlimb-dominated locomotion (Dorudon has the lowest score and Rodhocetus the highest, whereas the otter shrew has the lowest score among living mammals and the desman the highest). Mammals that are more aquatic have a shorter ilium and femur combined with longer manual and pedal phalanges, whereas the reverse is true for more terrestrial taxa. Lumbus- and tail-dominated swimmers tend to have a longer lumbus combined with shorter pedal elements, whereas the reverse is true for hindlimb-dominated swimmers. Trunk and limb proportions of early middle Eocene Rodhocetus are most similar to those of the living, highly aquatic, foot-powered desmans. Trunk and limb proportions of late middle Eocene Dorudon indicate that it was a lumbus-and-tail-powered swimmer specialized in the direction of modern whales. Thus it appears that the land-to-sea transition in whale evolution involved at least two distinct phases of locomotor specialization: (1) hindlimb domination for drag-based pelvic paddling in protocetids (Rodhocetus), with tail elongation for stability, followed by (2) lumbus domination for lift-based caudal undulation and oscillation in basilosaurids (Dorudon). Rates of evolution in both phases of this change of adaptive zone are about an order of magnitude higher than background rates for the timescale involved.

Substrate Size and Primate Forelimb Mechanics: Implications for Understanding the Evolution of Primate Locomotion

Did the anatomical and locomotor specializations of primates evolve in response to requirements of locomotion and foraging on thin branches? Laboratory studies of primates and other mammals provide data suggesting that as substrate size decreases primates will protract their arms to a greater degree, lower the center of gravity by increasing elbow flexion, and decrease forelimb substrate reaction forces. I tested these hypotheses by calculating maximum arm protraction, shoulder height, elbow flexion, and substrate reaction forces during stance phase in 5 species of Old World monkeys walking on a flat runway and raised poles of varying diameters. As substrate size decreased most subjects increased elbow flexion and lowered their shoulder height. Three of the 5 species lowered peak substrate reaction forces as substrate size decreased but, only 2 of the species increased arm protraction as substrate size decreased. These results reject the hypothesis that arm protraction is a function of branch size, but provide stronger support for the notion that branch size influences elbow flexion, shoulder height, and peak substrate reaction forces in some primates. The fact that biomechanical expectations are met in some (but not all) cases and some (but not all) species suggests that the topic is quite complex and requires further study. Nonetheless, preliminary data suggest that biomechanical accommodations to substrate size may have played a role in the early differentiation of primates from other mammals.

The Evolution of the Functional Role of Trunk Muscles During Locomotion in Adult Amphibians1

Synopsis. The axial musculature of all vertebrates consists of two principal masses, the epaxial and hypaxial muscles. The primitive function of both axial muscle masses is to generate lateral bending of the trunk during swimming, as is seen in most fishes. Within amphibians we see multiple functional and morphological elaborations of the axial musculature. These elaborations appear to be associated not only with movement into terrestrial habits (salamanders), but also with subsequent locomotor specializations of two of the three major extant amphibian clades (frogs and caecilians). Salamanders use both epaxial and hypaxial muscles to produce lateral bending during swimming and terrestrial, quadrupedal locomotion. However during terrestrial locomotion the hypaxial muscles are thought to perform an added function, resisting long-axis torsion of the trunk. Relative to salamanders, frogs have elaborate epaxial muscles, which function to both stabilize and extend the iliosacral and coccygeosacral joints. These actions are important in the effective use of the hindlimbs during terrestrial saltation and swimming. In contrast, caecilians have relatively elaborate hypaxial musculature that is linked to a helix of connective tissue embedded in the skin. The helix and associated hypaxial muscles form a hydrostatic skeleton around the viscera that is continuously used to maintain body posture and also contributes to forward force production during burrowing.

A new lorisid humerus from the early miocene of Uganda

An early Miocene (18–20 mya) distal humerus from Napak, Uganda, is the only element of the forelimb to be allocated to African Lorisinae. Its loris-like features distinguish it from other East African material that more closely resembles galagids. Tracing the evolution of the lorisoid body has been a difficult task due to the lack of good fossil material. Here, we add a single specimen to this poor record. This humerus helps to document the beginning of extant lorisid locomotor specialization and function.

Quadrupedalism in some Miocene catarrhines

The term quadrupedalism refers both to a locomotor mode involving the use of all four limbs to move on horizontal substrates and to a locomotor repertoire dominated by the locomotor mode of quadrupedalism. Among extant primates there are numerous types of quadrupedal repertoires and modes, only some of which have been well characterized in terms of their functional morphology. Most Miocene catarrhines are only known from fragmentary postcranial specimens, and do not closely resemble particular anthropoid taxa. Thus, their possible quadrupedalism can only be characterized in a fairly general way. Much of the postcranial skeleton is known for the hominoid Proconsul . Limb proportions and the detailed morphology of the trunk and limbs indicate a locomotor repertoire dominated by quadrupedalism. Proconsul's quadrupedal mode involved palmigrade hand placement, and fairly eclectic movement at the limb joints. Variations on this type of quadrupedal mode are likely for the hominoids Kenyapithecus, Dryopithecus, and Sivapithecus, although other components of the locomotor repertoire are likely to have been more strongly expressed in these genera. The primitive catarrhine Pliopithecus differs from Proconsul in having more gracile limbs and relatively longer forelimbs. These atelid-like features suggest a stronger representation of suspension and climbing in the locomotor repertoire. However, as in Proconsul, there are many features indicating the primacy of quadrupedalism. The primitive catarrhine Dendropithecus and its close relatives resemble Pliopithecus in many aspects of their locomotor morphology. The hominoid Oreopithecus differs from all the other Miocene taxa in having a Pongo -like locomotor repertoire dominated by climbing and suspension, but probably with a minor quadrupedal component. Oreopithecus apart, the known Miocene catarrhines are predominantly quadrupedal animals. This fact must be incorporated into any attempt to chart the emergence of the locomotor specializations of extant hominoids.

Locomotor patterns and costs as related to body size and form in teiid lizards

Stride parameters and gaits were examined in seven species of teiid lizards in an attempt to understand size‐dependent variation of locomotor patterns. Scaling of body dimensions to body mass revealed that axial measures conformed to geometric similarity, whereas the limb segments exhibited an allometry which was statistically significantly less than geometric similarity. Variations in the relationships between stride lengths, stride frequencies and duty factors (% of the stride that foot contacts ground) represented locomotor specializations and were not strictly size‐dependent among species. At body length equivalent velocities, stride length and stride frequency scaled to body mass0.40±0.06 and 0.09±0.03, respectively. Cost during locomotion at body length equivalent velocities could be estimated by the square of the product of stride length and stride frequency. Plotting the cost during locomotion for geometrically similar lizards against body mass yielded an estimate of the cost during locomotion that was proportional to mass0.62±0.11. An estimate of the mass‐specific cost during locomotion at body length‐equivalent velocities scales to mass−0.38±0.11. Because the limbs of these lizards exhibit an allometry less than geometric similarity, a correction of the estimate of the mass‐specific cost during locomotion could be obtained by factoring in the effect of increased locomotor costs associated with relatively shorter pelvic limbs in larger lizards. The allometrically corrected estimate of the mass‐specific cost during locomotion was proportional to mass−0.31. This estimated regression, which is the relatiue cost of transport for a single, morphologically conservative family of lizards, predicts a slope quite close to that derived from studies of oxygen requirements during locomotion in lizards of several families (slope= ‐0.28, John‐Alder, Garland &amp; Bennett, 1986) and in mammals (slope= ‐0.32, Taylor, Heglund &amp; Maloiy, 1982).

Editorial announcement

The term quadrupedalism refers both to a locomotor mode involving the use of all four limbs to move on horizontal substrates and to a locomotor repertoire dominated by the locomotor mode of quadrupedalism. Among extant primates there are numerous types of quadrupedal repertoires and modes, only some of which have been well characterized in terms of their functional morphology. Most Miocene catarrhines are only known from fragmentary postcranial specimens, and do not closely resemble particular anthropoid taxa. Thus, their possible quadrupedalism can only be characterized in a fairly general way. Much of the postcranial skeleton is known for the hominoid Proconsul . Limb proportions and the detailed morphology of the trunk and limbs indicate a locomotor repertoire dominated by quadrupedalism. Proconsul's quadrupedal mode involved palmigrade hand placement, and fairly eclectic movement at the limb joints. Variations on this type of quadrupedal mode are likely for the hominoids Kenyapithecus, Dryopithecus, and Sivapithecus, although other components of the locomotor repertoire are likely to have been more strongly expressed in these genera. The primitive catarrhine Pliopithecus differs from Proconsul in having more gracile limbs and relatively longer forelimbs. These atelid-like features suggest a stronger representation of suspension and climbing in the locomotor repertoire. However, as in Proconsul, there are many features indicating the primacy of quadrupedalism. The primitive catarrhine Dendropithecus and its close relatives resemble Pliopithecus in many aspects of their locomotor morphology. The hominoid Oreopithecus differs from all the other Miocene taxa in having a Pongo -like locomotor repertoire dominated by climbing and suspension, but probably with a minor quadrupedal component. Oreopithecus apart, the known Miocene catarrhines are predominantly quadrupedal animals. This fact must be incorporated into any attempt to chart the emergence of the locomotor specializations of extant hominoids.

New catarrhine phalanges from Rudabánya (Northeastern Hungary) and the problem of parallelism and convergence in hominoid postcranial morphology

Abstract Eight new manual and pedal phalangeal specimens from the Miocene catarrhine locality of Rudabanya are described. Four can be allocated to Anapithecus , a large pliopithecid, and four to Dryopithecus , a primitive hominid. The functional and comparative anatomy of the Anapithecus specimens supports previous work on the phalanges of this taxon. The four Dryopithecus specimens are the first to be described for this taxon. The functional anatomy of these specimens supports and enhances previous interpretations of Dryopithecus positional behavior based primarily on elbow morphology. Dryopithecus is seen as a relatively generalized suspensory arboreal quadruped with a powerful grasping pollex, lacking the specializations of individual living hominoid genera. It can be reasonably proposed as close to the primitive pattern of positional behavior for great apes and humans. Anapithecus was most like Alouatta without the prehensile tail, and with a fore- and hindlimb suspensory positional behavior lacking the specialized below-branch locomotor specializations of Ateles and hylobatids. Analysis of Miocene hominoid postcrania in general and phalanges in particular suggest that ecological constraints are of primary importance in determining broad patterns of morphology, though these can be distinguished from morphology based more directly on ancestry. In addition, patterns of similarity in phalangeal morphology can be explained by a combination of convergence and parallelism, the former distinguished from the latter by the degree to which common ancestry influences the outcomes of processes that contribute to morphological change.

Size- and locomotion-related aspects of hominid and anthropoid pelves: An osteometrical multivariate analysis

Two multivariate methods — the logarithmic principal component analysis (LPCA), and the logarithmic factorial analysis (LFA) — have been used tocompare the hip bone proportions of hominoids biometrically. The results have shown that size effects among apes and hominids interact to a centain extent with locomotor specializations, which are related to the attainment of more or less terrestrial behaviors. The pelvic morphology of great apes (Pongo, Pan, Gorilla) has retained numerous morphological traits — such as a gracile and elongated hip bone —, which were inherited from common adaptations to arboreal locomotion. In spite of these common traits, the African pongids (Pan, Gorilla) present two very different pelvic morphologies corresponding to two adaptative modes of terrestrial quadrupedalism. The hip bone of humans is proportionnally short and robust, most particularly at the level of its axial part. These characteristics, as well as the whole pelvic proportions, clearly indicate that gravitational forces exert a strong pressure on the pelvic walls during bipedalism. Among hominids, the transition from an australopithecine-like pelvic pattern to a human-like one corresponds to an increase of loading constraints on the hip jiont. This seems to indicate an evident change in locomotor behavior. Progression apparently became exclusively terrestrial with the genusHomo.

Taxeopody in the carpus and tarsus of Oligocene Pliohyracidae (Mammalia: Hyracoidea) and the phyletic position of hyraxes.

Recent hyracoids and elephants share a taxeopode arrangement of tarsal and carpal bones, a condition in which bones are aligned with minimal interlocking between adjacent elements. Taxeopody has often been interpreted as a synapomorphy reflecting a close phyletic link between Hyracoidea and Proboscidea, but recently it has been suggested [Fischer, M. S. (1986) Cour. Forschungsinst. Senckenberg 84, 1-132] that hyracoid taxeopody is an independent acquisition resulting from selection favoring increased midcarpal and midtarsal rotation and that Hyracoidea is actually allied with Perissodactyla. As a test of this hypothesis, isolated carpal and tarsal bones of primitive Oligocene hyracoids from the Fayum, Egypt, have been examined to determine whether these indicate a taxeopode or diplarthral carpus and tarsus. Four complete astragali from the Fayum, representing at least three taxa, show a single, slightly convex articular surface on the head for articulation with the navicular and lack a facet for the cuboid. Two complete magna representing two species have a single proximal facet for articulation with the lunar, and they lack a facet for the scaphoid. Thus, both the carpus and tarsus of Fayum hyracoids are taxeopode. Taxeopody in hyracoids cannot be attributed to selection for carpal and tarsal rotation in climbers because the Oligocene, Miocene, and Recent species show great diversity in body size and probably locomotor specializations, despite relative uniformity of structure in the carpus and tarsus. The shared taxeopody of hyracoids and proboscideans, along with other osteological characters and similarities in hemoglobin, eye lens proteins, and other molecules, all suggest that Hyracoidea belongs within Paenungulata.