Hindlimb Elements Research Articles

Precision and Consistency of the Taphonomic Signature of Predation by Crowned Hawk-Eagles (Stephanoaetus coronatus) in Kibale National Park, Uganda

Abstract Prey material, which was collected from beneath the nests of two pairs of crowned hawk-eagles (Stephanoaetus coronatus) in the Ngogo study area, Kibale National Park, Uganda, was analyzed to identify the taphonomic features diagnostic of eagle predation. Material from a recent three-year collection interval was compared to an earlier three-year collection subsample to determine signal consistency over time. The bulk of the assemblage is comprised of cercopithecoid monkey remains, reflecting the taxonomic composition of the Ngogo area. Taxonomic composition of the assemblage remains highly consistent over the collection period. Bone survivability and fragmentation profiles, as well as damage patterns, also were investigated. Crowned hawk-eagles inflict much less damage to prey skeletons than do mammalian carnivores. Crania, scapulae, and hindlimb elements are most likely to survive predation by crowned hawk-eagles and to be concentrated at nest sites, but these elements (especially crania) show ag...

SERIAL HOMOLOGY AND THE EVOLUTION OF MAMMALIAN LIMB COVARIATION STRUCTURE

The tetrapod forelimb and hindlimb are serially homologous structures that share a broad range of developmental pathways responsible for their patterning and outgrowth. Covariation between limbs, which can introduce constraints on the production of variation, is related to the duplication of these developmental factors. Despite this constraint, there is remarkable diversity in limb morphology, with a variety of functional relationships between and within forelimb and hindlimb elements. Here we assess a hierarchical model of limb covariation structure based on shared developmental factors. We also test whether selection for morphologically divergent forelimbs or hindlimbs is associated with reduced covariation between limbs. Our sample includes primates, murines, a carnivoran, and a chiropteran that exhibit varying degrees of forelimb and hindlimb specialization, limb size divergence, and/or phylogenetic relatedness. We analyze the pattern and significance of between-limb morphological covariation with linear distance data collected using standard morphometric techniques and analyzed by matrix correlations, eigenanalysis, and partial correlations. Results support a common limb covariation structure across these taxa and reduced covariation between limbs in nonquadruped species. This result indicates that diversity in limb morphology has evolved without signficant modifications to a common covariation structure but that the higher degree of functional limb divergence in bats and, to some extent, gibbons is associated with weaker integration between limbs. This result supports the hypothesis that limb divergence, particularly selection for increased functional specialization, involves the reduction of developmental factors common to both limbs, thereby reducing covariation.

The vertebrate fauna of the Upper Permian of Niger—III, morphology and ontogeny of the hindlimb of Moradisaurus grandis (Reptilia, Captorhinidae)

ABSTRACT We describe hindlimb elements of the large captorhinid Moradisaurus grandis (Reptilia: Captorhinidae) recently collected from the Upper Permian Moradi Formation of north-central Niger. This description is based primarily on an associated partial skeleton comprising a hemimandible, vertebral column, and partial left and nearly complete right hindlimb. Additionally, we report on a well-preserved, articulated, and essentially complete juvenile pes that provides important information on the ontogeny of the captorhinid tarsus. The hindlimb of Moradisaurus is stout and more massively built than in any other known captorhinid. The femur displays several features interpreted as adaptations to the demands of large body size, and the tibia and fibula have short, wide shafts and hypertrophied condyles and epicondyles. The astragalus is very derived, possessing two accessory ossifications and a relatively horizontal tibial articulation, indicating that the tibia was held more vertically than in other captorhinids. The calcaneum is co-ossified with distal tarsal five. The juvenile pes indicates that the captorhinid centrale arose from the fusion of two ossification centers, and that the captorhinid astragalus arose from the fusion of at least three ossification centers.

A new flightless gallinule (Aves: Rallidae: Gallinula) from the Oligo-Miocene of Riversleigh, northwestern Queensland, Australia

Flightlessness in birds occurs in a taxonomically diverse array of families, but is best exemplified in the rails (Rallidae). Most flightless species of rails live on islands, where the absence of native mammalian predators may make flight superfluous. Fossil rails from Oligo-Miocene sites at Riversleigh, northwestern Queensland, Australia, are considered to represent a single species of gallinule Gallinula, described here as new. Compared with four Quaternary species of Gallinula from Australasia (two volant, two non-volant), it shows similarities with the flightless species in the development of the fore- and hindlimb elements and in other characteristics of limb bone morphology associated with flightlessness. These indicate that the Riversleigh species was non-volant. Its relationships with the Quaternary species, including the flightless Gallinula mortierii, now restricted to Tasmania, but known from Plio-Pleistocene deposits in eastern mainland Australia, are considered.

Gender-Specific Reproductive Tissue in Ratites and Tyrannosaurus rex

Unambiguous indicators of gender in dinosaurs are usually lost during fossilization, along with other aspects of soft tissue anatomy. We report the presence of endosteally derived bone tissues lining the interior marrow cavities of portions of Tyrannosaurus rex (Museum of the Rockies specimen number 1125) hindlimb elements, and we hypothesize that these tissues are homologous to specialized avian tissues known as medullary bone. Because medullary bone is unique to female birds, its discovery in extinct dinosaurs solidifies the link between dinosaurs and birds, suggests similar reproductive strategies, and provides an objective means of gender differentiation in dinosaurs.

Intraspecific correlations among morphology, performance and habitat use within a green anole lizard (Anolis carolinensis) population

We examined habitat use, morphology, jumping and clinging ability for 403 juvenile, female and male green anole lizards, Anolis carolinensis, in a population in south-eastern Louisiana. We sought to answer three questions: (1) Do age/sex classes differ in habitat use, morphology and performance ability? (2) Do habitat use, morphology and performance correlate among all individuals across three age/sex classes (juveniles, females and males)? (3) Do juveniles compensate for their poor absolute performance capacities by being better performers on a relative scale? The three age/sex classes were found to differ significantly in size-adjusted morphology, habitat use and size-adjusted performance capacity. Juveniles tended to occupy perches which were closer together than those of adult males and females. The distal elements of the hindlimb (femur, tibia) were significantly longer in males than in females and juveniles, while females were more stocky than males and juveniles. The only significant overall ecomorphological relationship detected was between the lengths of the distal hindlimb elements and maximum jump acceleration. Our hypothesis that juveniles should be better performers (relative to size) compared to adults was disproved, as adult females were always the best performers relative to size. Our analysis of a mainland anole population presents a different view of population structure compared to similar studies involving Caribbean Anolis lizards, which show more ecological differentiation among age/sex classes, and also show that juveniles are relatively good performers.

A comparison of habitat use, morphology, clinging performance and escape behaviour among two divergent green anole lizard (Anolis carolinensis) populations

We measured available and actual habitat use, morphology, escape behaviour and clinging ability in a large sample(N = 242) of green anoles, Anolis carolinensis, in a habitat consisting primarily of segregated dense clumps of broadleaves, Aspidistra elatior (Tulane University campus, LA) to compare against similar data collected previously froma more typical habitat c. 30 km away, consisting of continuous strands of bushes and trees (Good Hope Field, St.Charles Parish, LA). At Tulane the anoles perched primarily on the broad, smooth leaves of broad leaves, whereasin Good Hope Field (GHF) they predominantly perched on branches and tree trunks. The two populations differedsignificantly in morphology. In Tulane, the anoles tended to have shorter distal hindlimb elements, longer forelimbelements, and were more ‘slender’ than those at GHF. A comparison of escape behaviour showed population and sexdifferences. In both populations, females had significantly longer approach distances (i.e. were more ‘wary’) thanmales. These distances were, in addition, significantly longer at GHF than at Tulane for both sexes; this may be dueto the potentially higher diversity and abundance of predators at GHF, although habituation to humans may alsoplay a role. Anoles at Tulane had significantly larger toepads and higher clinging abilities than those at GHF. Theenhanced clinging abilities of anoles at Tulane may have arisen due to their propensity to use smooth leaves as theirprimary substrate. Overall, our data reveal substantial ecological, behavioural, morphological, and functional dif-ferences among populations, some of which may be adaptive. © 2005 The Linnean Society of London, BiologicalJournal of the Linnean Society, 2005, 85, 223–234.

Soft-Tissue Vessels and Cellular Preservation in Tyrannosaurus rex

Soft tissues are preserved within hindlimb elements of Tyrannosaurus rex (Museum of the Rockies specimen 1125). Removal of the mineral phase reveals transparent, flexible, hollow blood vessels containing small round microstructures that can be expressed from the vessels into solution. Some regions of the demineralized bone matrix are highly fibrous, and the matrix possesses elasticity and resilience. Three populations of microstructures have cell-like morphology. Thus, some dinosaurian soft tissues may retain some of their original flexibility, elasticity, and resilience.

Reconsideration of skeletal development of Chelydra serpentina (Reptilia: Testudinata: Chelydridae): evidence for intraspecific variation

Patterns of formation and sequence of ossification of the entire skeleton are described for the snapping turtle Chelydra serpentina, based on new and previously published data. Differences in the sequences of ossification events are described and demonstrate considerable intraspecific variation in these developmental data. The chondrocranium of a late developmental-stage specimen is described and illustrated as baseline data for comparative studies. Patterns of formation and chondrification of forelimb and hind limb elements are generally consistent with those of previous studies; however, conspicuous differences in the patterns of ossification are observed among metapodial and phalangeal elements. In the cranium, patterns of ossification of dermal elements are generally more variable than are those of endochondral elements of the braincase, and as in previous studies, endochondral elements ossify after dermal elements. Documented intraspecific variation in sequence and timing of formation, chondrification, and ossification of skeletal elements should serve as a caveat for those conducting studies of phylogeny, heterochrony, and evolution with these data. Causes of natural and induced variation are discussed briefly.

Taphonomic aspects of crowned hawk-eagle predation on monkeys.

This study provides a taphonomic analysis of prey accumulations of crowned hawk-eagles (Stephanoaetus coronatus) from Ngogo, Kibale National Park, Uganda, collected over 37 months from below nests of two eagle pairs. Crowned hawk-eagles are powerful predators capable of killing animals much larger than themselves, and are significant predators of cercopithecoid monkeys in forest habitats throughout sub-Saharan Africa. At Ngogo, 81% of the individuals in the kill sample are monkeys. Redtail monkeys (Cercopithecus ascanius) are particularly well represented in the sample, making up 66% of monkeys identified to species. Despite an impressive killing apparatus, crowned hawk-eagles are fastidious eaters that inflict far less damage to bone than mammalian predators. Examination of skeletal material from the Ngogo kill sample reveals that crania, hindlimb elements, and scapulae survive predation better than do other bones. Crania of adults are typically complete and accompanied by mandibles, while crania of young individuals are usually dissociated from mandibles and lack basicrania and faces. Long bones are often whole or show minimal damage. Thin bones, such as crania and innominates, are marked by numerous nicks, punctures, and "can-opener" perforations. Scapular blades are heavily raked and shattered. Along with the strong preference for cercopithecoids, these distinct patterns of bone survival and damage indicate the feasibility of recognizing specific taphonomic signatures of large raptors in fossil assemblages. Berger and Clarke (1995) hypothesized that crowned hawk-eagles or similar large raptors were principally responsible for the accumulation of the late Pliocene fossil fauna from Taung, South Africa, including the type infant skull of Australopithecus africanus. The results of our study suggest that the faunal composition and type of damage to the hominid skull and other bone from Taung are consistent with the predatory activities of large raptors. More rigorous assessment of their hypothesis will require sorting the Taung fauna by locality and further detailed analysis of species composition and bone damage and survivability patterns.

A new specimen of an early crocodylomorph (cf. Sphenosuchus sp.) from the Upper Triassic Chinle Formation of Petrified Forest National Park, Arizona

ABSTRACT An associated skeleton of a crocodylomorph from the Painted Desert of Petrified Forest National Park is the second relatively complete specimen of a crocodylomorph described from the Upper Triassic Chinle Formation. The specimen lacks cranial and hind-limb elements commonly used for classification of crocodylomorphs, so character states of other features, notably armor, pelvic, tooth, and dentary morphology, are evaluated. Phylogenetic analysis of the Triassic/Jurassic non-crocodyliform crocodylomorphs (“sphenosuchians”) indicates that the new specimen is most similar to the Early Jurassic genus Sphenosuchus. Some of the features that ally the new specimen with Sphenosuchus may be artifacts of scaling, as the new specimen and the holotype of S. acutus are the two largest specimens of members of this group.

Allometric Growth of the Hind Limbs of Some Terrestrial Iguanid Lizards

Parameters of the allometric equation (y = bxa) were estimated for relative growth in the length of hind-limb elements vs. body length in five species of terrestrial iguanid lizards. Measurements of shank, thigh and snout-vent length were made on preserved samples, each representing a cross section of age classes from a restricted geographic locality. Both positive allometry ((x> 1) and negative allometry (c( < 1) were observed, the latter being more common. These results are consistent with Kramer's (1951) hypothesis that lizards should commonly show negative allometric growth of the hind limbs, which enhances the locomotor ability of vulnerable hatchlings. Dodson's (1975) hypothesis that positive allometry of hind limbs is correlated with an increase in home range size during ontogeny is not supported. We hypothesize that positive allometry in male scrub lizards represents a temporal patterning of investment in morphology in relation to a change in defensive behavior during ontogeny. Allometric growth in lizards may also be explicable in the context of maintaining similar biomechanical function with increasing size, or in terms of altering biomechanical function during ontogeny as in Laerm's (1974) habitat-shift model.

The Hindlimb Elements of the Maas (Aves, Dinornithidae): A Multivariate Assessment of Size and Shape

A multivariate morphometric analysis of size and shape was performed on the hindlimb skeletal elements of the extinct New Zealand moas (Dinornithidae). Investigations were undertaken of size‐shape patterns within species and among moas as a group using principal components analysis; between species investigations used canonical analysis. In addition, standard allometric curve‐fitting of six femur, seven tibiotarsus, and nine tarsometatarsus variables against body size was performed.Size was the major discriminator along the first principal component for all three bones in the intraspecific and whole‐group analyses. Shape was the important discriminator along the second component: in the whole‐group analysis of all three bones, separation was based on relative robustness of the shaft, whereas in the intraspecific analyses shaft robustness was only expressed in the analysis of the femur, there being little correspondence in the results between the intraspeci fic and whole‐group analyses of the tibiotarsus and tarsometatarsus. Size was the major discriminator along the first canonical axis for the between‐group investigations of the femur and tibiotarsus, but in the analysis of the tarsometatarsus shape influences were equally as important as those of size. The second canonical axis separated groups on the basis of shape differences in all three hindlimb elements.The genus Dinornis, which contains the largest species of moas, has evolved sizeshape patterns very different from those of other moas. The species of Dinornis did not follow size‐dependent allometric trends and evolved proportionately thinner legs than might be expected for their body size. All other moas exhibit allometric increase in all hindlimb variables except bone lengths. Dinornis may have evolved a cursorial mode of locomotion as an adaptation for certain intraspecific behavioral interactions.