Dental microwear and mechanisms in early hominids from Laetoli and Hadar

The dentition of early hominids from Laetoli and Hadar provide evidence of "incisal stripping" and a shear-grinding action for C/P3 complex through microscopic examination of wear facets on dental crowns. This masticatory pattern of dental wear resembles that of Papio papio and suggests behavioral analogies between early hominids and Papio.     

Laetoli toes andAustralopithecus afarensis

The probable misfit between feet, particularly toes II–V, of 3.0-million-year-oldAustralopithecus afarensis from Hadar, Ethiopia, and the 3.5-million-year-old hominid footprints at Site G, Laetoli, Tanzania, casts doubt thatA. Afarensis made the Laetoli trails. We suggest that another species ofAustralopithecus or an anonymous genus of the Hominidae, with remarkably humanoid feet, walked at Laetoli. It would be imprudent to declare thatHomo was present at Laetoli 3.5 million years ago (my) because there is no evidence of brain expansion, advanced tool manufacture, or other non-locomotor hallmarks of the human condition at Site G.     

Pliocene Animal Trackways at Laetoli: Research and Conservation Potential

Laetoli, a paleoanthropological site in Northern Tanzania, is perhaps best known for its famous fossil hominid footprints that were discovered by Mary Leakey and her co-workers in 1978. The site not only preserves the hominid footprints but also trackways, which provide a snapshot of Pliocene faunal communities from East Africa and their inferred environments. Unlike the hominid footprints at site G, which have received tremendous attention, the animal trackways, especially at Localities 7, 8 and 10 have been neglected and are fast disappearing. In this paper, we discuss animal tracks at a newly discovered exposure and provide preliminary data on the tracks at this exposure and other sites. We also discuss the importance of the animal trackways as ecological indicators, which we have investigated as part of ongoing research and conservation efforts initiated by the Tanzania Field School in Paleoanthropology and the Associated Colleges of the Midwest (ACM) Tanzania Semester Abroad programs.     

Versatility and specialization in labrid fishes: ecomorphological implications

Summary The term specialized has been used to describe species that possess unique functional attributes and/or a narrow, stereotyped range of attributes, but there are few comparative functional analyses of specialists and generalists. If species with functional morphological specializations are capable of functioning over a broad range, the link between morphology and ecology may be relaxed under certain environmental conditions. In this study, high-speed films of jaw movements during prey capture were compared statistically for three coexisting coral reef fish species in the family Labridae, one trophic specialist and two trophic generalists. The trophic specialist possessed a unique functional feature related to the movement of the hyoid in the floor of the mouth, while the trophic generalists were not observed to possess any functional specializations. All three species showed functional versatility in that they were able to adjust their prey capture mechanism in response to the evasive potential of the prey. The functional versatility of trophic specialists has implications for ecomorphological studies, since species characterized as possessing unique functional or morphological features may demonstrate marked flexibility in ecological variables such as diet or foraging behavior, decreasing the likelihood of identifying correlations between morphology and ecology.     

Walking on ashes: insect trace fossils from Laetoli indicate poor grass cover associated with early hominin environments

More than 4000 insect trace fossils collected in recent years from Pliocene deposits at Laetoli in northern Tanzania provide new insights on early hominin palaeoenvironments. These trace fossils include: Fictovichnus gobiensis, Coprinisphaera murguiai, C. kheprii, Coprinisphaera ispp., Quirogaichnus isp., Teisseirei linguatus isp. nov., Celliforma ritchiei isp. nov., C. spirifer, C. germanica, C. cfr. curvata, Celliforma ispp., Rosellichnus isp., Vondrichnus planoglobus, Laetolichnus kwekai igen. et isp. nov. and Krausichnidae indet. They reveal that at least one species of moth, three dung beetles and five other coleopterans, nine taxa of solitary bees, and an indeterminate number of taxa of termites inhabited the Lower Laetolil environments. The Upper Laetolil environments, which have yielded a rich diversity of vertebrate fossils, including the early hominin Australopithecus afarensis and its putative footprints, supported several taxa of termites, one dung beetle, five other coleopterans, and eleven taxa of bees. The Upper Ndolanya environments, which have yielded the hominin Paranthropus aethiopicus, record four taxa of dung beetles, four other coleopterans, and two taxa of bees. The record of larval mortality and lack of intruder activity, revealed by the absence of emergence and intruder traces, may be associated with the anoxic/hypoxic conditions caused by the instantaneous burial of soils under thick volcanic ashes. The record of the Celliforma Ichnofacies in the Upper Laetolil environments indicates the dominance of shrubland to woodland with limited grass cover. This is supported also by the absence of Coprinisphaera, which suggests a scarcity of fresh grasses and a low abundance of large mammal grazers.     

Should congruence between intra- and interspecific ecomorphological relationships be expected? A case study with the great tit,Parus major

We studied the relationship between leg morphology and posture while feeding in a population of great tits (Parus major) under controlled conditions to investigate to what extent morphology and ecology are linked at the individual level. From predictions generated at the interspecific level within the genus Parus (Moreno and Carrascal 1993), we tested whether intra- and interspecific ecomorphological relationships are consistent. Within our population, neither leg bone lengths nor leg muscle morphology were related to the feeding posture of individuals. However, differences in body weight were correlated with inter-individual differences in time spent hanging. These results demonstrate that the association between intra- and interspecific ecomorphological relationships is not uniform. We argue that, at the intraspecific level, body weight overrides the significance of other traits that have a functional meaning at the interspecific level (i.e. leg segment lengths, muscular morphology), due to isometric variation of morphological traits (muscular and skeletal) with body mass. Thus, the discrepancy between the ecomorphological associations at intra- and interspecific levels is the result of a problem of scale (morphological changes in evolutionary time and isometric variation of morphological traits with body mass in ecological time).     

Functional morphology of the feeding apparatus of ten species of Pacific butterflyfishes (Perciformes,Chaetodontidae): an ecomorphological approach

Synopsis The functional morphology of the feeding apparatus and the feeding ecology of an assemblage of ten species of butterflyfishes was investigated using a comparative ecomorphological approach. Behavioral observations in situ and in vivo, morphological measurements of fresh-killed specimens, scanning electron microscopy, and kinematic modeling were utilized. The fishes show varying degrees of morphological and behavioral specialization and generalization. The more specialized species group according to how they feed, rather than what they feed on. The feeding guild concept is therefore not very instructive in understanding the functional significance of the feeding apparatus. Many of the morphologically specialized butterflyfishes demonstrate evolutionary convergence in feeding morphology. Whereas the more morphologically specialized species do generally have more ecologically specialized diets, these data do not particularly support the ecomorphological hypothesis in that similar diets do not correspond to similar morphologies.     

The context of Stw 573, an early hominid skull and skeleton from Sterkfontein Member 2: taphonomy and paleoenvironment

The reconstructed taphonomic and paleoenvironmental contexts of a ca. 4 million-year-old partial hominid skeleton (Stw 573) from Sterkfontein Member 2 are described through presentation of the results of our analyses of the mammalian faunal assemblage associated stratigraphically with the hominid. The assemblage is dominated by cercopithecoids (Parapapio and Papio) and felids (Panthera pardus, P. leo, Felis caracal, and Felidae indet.), based on number of identified specimens, minimum number of elements and, minimum number of individuals. In addition, the assemblage is characterized by a number of partial skeletons and/or antimeric sets of bones across all taxonomic groups. There is scant indication of carnivore chewing in the assemblage. These observations, in addition to other taphonomic data, suggest that the remains of many animals recovered in Member 2 are from individuals that entered the cave on their own-whether accidentally by falling through avens connecting the cave to the ground surface above or by intentional entry-and were then unable to escape, rather than primarily through systematic collection by a biotic, bone-accumulating agent. The taphonomic conclusion that animals with climbing proclivities (i.e., primates and carnivores) are preferentially preserved over other taxa, ultimately because of those proclivities, urges caution in assessing the fidelity of the assemblage for reconstruction of the Member 2 paleoenvironment. With that caveat, we infer that the Member 2 paleoenvironment was typified by rolling, rock-littered and brush- and scrub-covered hills, indicated by the abundant F. caracal and cercopithecoid fossils recovered and the identified presence of the extinct Caprinae Makapania broomi. In addition, the valley bottom may have retained standing water year-round, perhaps supporting some tree cover--a setting suitable for the well-represented ambush predator P. pardus and suggested by the presence of Alcelaphini. Finally, the reconstructed taphonomic and paleoenvironmental settings of Sterkfontein Member 2 are compared to penecontemporaneous sites in South and East Africa.     

第四届东亚古环境国际会议在香港召开

第四届东亚古环境国际会议在香港召开１９９５年１月３日至７日,由亚洲研究中心主持的“第四届东亚古环境国际会议”在香港大学召开．参加大会的６０多名代表分别来自中国包括台湾、香港地区,澳大利亚、美、英、荷兰、奥地利、日本、捷克和印度．报告内容分为地质和古气...     

Alternative life histories of the genusLucania: 3. An ecomorphological explanation of altricial (L. parva) and precocial (L. goodei) species

Synopsis Important differences were observed in the early ontogenies ofLucania parva andLucania goodei. These differences can be explained in terms of the altricial-precocial model of speciation.Lucania parva can be recognized as an altricial form that produces many eggs with relatively little yolk investment, compared to the more precocialL. goodei. Many of the differences observed in embryo, larva and juvenile specimens appear to be related to these differences in gamete investment. Accelerated developmental rates in the precocial form suggest that paedomorphosis is an important proximate mechanism in the bifurcation of alternative life-history styles in this genus. Some morphological characteristics, such as vitelline circulation and body shape, may be transformations associated with the particular environmental conditions in which the animals must develop and survive. Our observations suggest that these two species in the genusLucania have followed different ontogenic trajectories in response to prevailing environmental conditions.     

Sperm quality and the morphology of cryopreserved testicular tissues recovered post-mortem from diverse wild species

This study compared the effects of slow and fast freezing of testicular tissue of wild animals collected at post-mortem on testicular structure and testicular sperm. The testes of seven animals that had died in captivity; three felids (jungle cat, lion and leopard), two cervids (rusa deer and fea’s muntjac) and two bovids (Sumatran serows) were cryopreserved using slow- and fast-freezing protocols. There were greater reductions in the integrity of the sperm membrane and DNA in tissues cryopreserved using slow freezing compared to fast freezing (membrane integrity reduced by 21.5 ± 12.4% vs. 13.0 ± 6.9%, P = 0.11 and DNA integrity reduced by 22.7 ± 16.3% vs. 6.6 ± 6.3%, P = 0.13). Histologically, there were similar degrees of detachment and shrinkage of the seminiferous tubules whereas, TUNEL assay revealed a tendency towards more apoptotic changes in the intra-tubular cells of tissues frozen using fast freezing compared to slow freezing (P = 0.09). In conclusion, fast freezing tended to cause less damage to testicular sperm but its protective effect on intra-tubular cells was likely compromised. This is the first report of gamete recovery in the wild and of the comparison in various wildlife species, between testicular tissues cryopreserved using different protocols.     

Terrestrial adaptations in the postcranial skeletons of guenons

Arboreal and semiterrestrial guenons show similar osteological features of the limbs across a wide range of species, environments, and geography, while the more terrestrially committed guenons exhibit greater morphological divergence. An ecomorphological comparison of two sympatric guenons living in Kibale Forest, Uganda, reveals an array of anatomical adaptations for terrestriality in the limbs of Cercopithecus lhoesti similar to those found in Erythrocebus patas. In contrast, Cercopithecus aethiops, although also frequent users of the terrestrial environment, generally exhibit fewer morphological adaptations characteristic of a terrestrial lifestyle. It appears that significant morphological modification for terrestriality has occurred twice within the diverse radiation of living guenons with C. aethiops perhaps representing a third group in the making. © 1994 Wiley-Liss, Inc.     

High ecomorphological diversity among Early Cretaceous frogs from a large subtropical wetland of Iberia

Anurans are extremely diverse amphibians with a unique Bauplan, whose origin, early ecomorphological diversification, and adaptive significance remain elusive. Their early fossil record is improving at an accelerated pace worldwide, but its contribution to these issues is still wanting. Here we explore ecomorphological diversity among Early Cretaceous (Barremian) frogs that inhabited a large subtropical wetland from Iberia by inferring locomotor abilities with a phylogenetic flexible discriminant analysis on data from limb proportions, which strongly correlate with locomotion. The results show a remarkable diversity among these frogs when compared with the extant diversity from this region and from tropical and subtropical wetland assemblages worldwide, encompassing miniature to medium-size jumpers and dedicated swimmers with more extreme proportions than extant ‘archeobatrachians,’ but also more generalized jumping and/or swimming forms. This agrees with the inferred wetland paleoenvironment and the hypothesis regarding early frogs as small poor jumpers or swimmers that evolved their peculiar Bauplan in aquatic environments.     

Ecological implications of the relative rarity of fossil hominins at Laetoli

Hominins are a very rare component of the large-mammal fauna at Laetoli. Although no equivalent data are available for Hadar, the much higher count and relative abundance of hominins suggests that they may have been more common at the latter site. The apparent relative rarity of hominins at Laetoli may have significant implications for understanding the ecology of Australopithecus afarensis. However, it is essential to first assess the extent to which taphonomic variables might have been a contributing factor. Using data from fossil ruminants, we show that the survivability of skeletal elements at Laetoli relates to the extent to which they can resist carnivore scavenging and their likelihood of being entirely buried by volcanic ashes and tuffaceous sediments. The rarity of hominins at Laetoli is probably due in part to the influence of these two taphonomic factors. However, these factors cannot account entirely for the difference in hominin relative abundance between these two sites, and ecological differences were probably a contributing factor. The highest population densities of chimpanzees today occur in forest and closed woodland, with reduced densities in open woodland. If similar levels of population-density variation characterized A. afarensis, the differences between Hadar and Laetoli may relate to the quality/optimality of the habitats. Hadar was, in general, much more densely wooded and mesic than Laetoli, with permanent and substantial bodies of water. In contrast, Laetoli was predominantly a woodland-shrubland-grassland mosaic supported only by ephemeral streams and ponds. The apparent greater relative abundance of hominins at Hadar compared with Laetoli suggests that, like chimpanzees, A. afarensis may have been more successful in more densely wooded habitats. Compared with Hadar, Laetoli probably represented a less optimal habitat for the foraging and dietary behavior of A. afarensis, and this is reflected in their inferred lower abundance, density, and biomass.     

Eco-morphological patterns of the sagitta of Antarctic fish

Morphology and morphometry of the sagittae otolith were studied in pelagic and mesopelagic fish. The shape, margins and rostrum of four groups of otoliths from several species were analyzed: group 1 (pelagic fish associated with the under ice cover N = 42), group 2 (pelagic fish associated with water offshore N = 9), group 3 (mesopelagic fish associated with extensive vertical migration N = 57) and group 4 (mesopelagic fish associated with short vertical migration N = 54). E (maximum width of the sagitta /maximum length of the sagitta %), R (rostrum length (RL)/maximum length of the sagitta %) and S (sulcus area (SS)/otolith area (OS) %) indexes were calculated for each species. Sagittae of pelagic groups (1 and 2) showed the smallest sagitta dimensions in relation to the total length of the fish, in this group the sagitta shape is variable. Sagittae of mesopelagic fish (groups 3 and 4) showed variable shape and edges. The shape in group 4 was polygonal and these species have more width than length. Statistical analysis showed significant differences in the E, R and S indexes. These results were compared with other 19 species, belonging to six families, taken from a publisher-edited literature. E, R and S-values could be used to characterize the sagittae of the Antarctic fish and could be considered as a useful tool for fish ecology studies.     

An ecomorphological study of the raptorial digital tendon locking mechanism

Extensive adaptive radiation in hindlimb design among raptors is well known. However, the degree of variation in the structure and expression of the digital tendon locking mechanism (TLM) and its adaptive significance have received little attention. This comparative morphological study of 12 raptor and three non-raptor species revealed a distinct raptorial design, characterized by a distally located TLM that is densely packed with locking elements of increased robustness and height. Although the Falconiformes and Strigiformes converged upon this pattern, unique design features were identified among the nocturnal birds of prey. Variation in TLM structure was often consistent with phylogeny, although interfamily similarities were revealed among a number of species with the same dietary habit. The evolutionary factors that may have led to the observed variation, as well as the biomechanical implications of varying designs, are discussed.     

The palaeoecology of the Upper Ndolanya Beds at Laetoli,Tanzania

The palaeoecology of the fauna from the Ndolanya Beds, Laetoli, Tanzania, has been analysed to reconstruct the environment of this 2.6 Ma site. Community profiles have been constructed in relation to three variables that carry ecological meaning: body weight, locomotor adaptations and feeding preferences. Comparing the similarities and differences in the structure of the fossil faunas with those of modern environments allows us to draw inferences about palaeoenvironmental conditions, and this is based on a comparative dataset of 15 modern environments (44 localities) covering a wide range of climatic and ecological conditions across Asia, Africa and Central America. In addition, 16 fossil sites in East and South Africa have been analysed in the same way, and both sets of comparative data have been used as the basis for comparison with an ecological diversity analysis of the fauna from the Upper Ndolanya Beds. The Ndolanya fauna is characterized by a predominance of medium to large sized terrestrial and herbivorous species.There is evidence of taphonomic bias that eliminated many of the smaller species. A comparison of multivariate analyses of 23 selected modern localities conducted both with and without the small species included, indicates that the loss of these species does not adversely influence the results of an ecological diversity analysis. The evidence suggests that at the time of the deposition of the Ndolanya Beds the Laetoli region was a semi-arid bushland. This is considerably drier and more open than is suggested for the earlier Laetolil Beds.     

The role of ecomorphological studies in the comparative biology of fishes

Synopsis The goal of an ecomorphological study is to understand the interactions between the morphology of organisms and their ecology. Both the morphology and the ecology presented by an organism are directly or indirectly under the influence of the environmental conditions that the organism experiences and its heritable composition. The development and interpretation of the central element of ecomorphological studies, the comparison between patterns of variation of morphological and ecological characters, depends heavily on the mechanistic framework provided by functional morphological and biomechanical studies. The cause-and-effect hypotheses derived from this comparison can be tested with performance trials. Ecomorphology forms an integral part of comparative biology, along with ecophysiology, behavioral ecology, and evolutionary ecology. Current issues in ecomorphological research that are addressed in this volume include application of a more functional approach to the choice of characters, integration of morphological, behavioral, and physiological information to address adaptation, and the expansion of spatial and temporal (ontogenetic and evolutionary) scales of ecomorphological questions. Future directions for Ecomorphology include broadening the knowledge base, further integration of information from other disciplines, examination of the role of environmental and genetic factors in producing and maintaining ecological and morphological diversity, and application of ecomorphological insights to questions of community structure.