Browsing by Author "Chinsamy, Anusuya"
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- ItemRestrictedChemometric analysis of EDXRF measurements from fossil bone(Wiley, 2011) Thomas, Daniel B; Chinsamy, AnusuyaBone chemistry is an important source of biological and environmental information. Elemental compositions of archaeological and fossil bone have granted insight into the diets of ancient humans and other animals, as well as informing about the burial conditions of bone. Chemical studies of ancient bone can be performed non-destructively with portable energy-dispersive Xray fluorescence (EDXRF) spectrometers, which is particularly advantageous for on-site analyses of museum specimens. Portable EDXRF instruments carry some analytical disadvantages, however, which may result in reduced precision or accuracy. Analytical shortfalls may be overcome by analysing inter-sample trends in EDXRF spectral data instead of reported concentration measurements. We investigated the utility of statistically treating handheld EDXRF spectra from fossil bone and teeth, specifically the normalisation and mean centering of spectral data before principal component analysis. Fossil bone and tooth specimens were sourced from two Pleistocene localities in the Western Cape of South Africa, Swartklip 1 and Elandsfontein Main. Samples from the two localities could be distinguished using principal component score values, and coefficient loadings allowed chemical interpretation of the score clusters. Swartklip 1 samples were associated with elevated concentrations of Ca, indicating an additional Ca-bearing mineral (i.e. calcite), whereas Elandsfontein Main samples were associated with elevated Fe and Sr concentrations. Fossil bone chemistry could be related to groundwater percolation through the sedimentary matrices of each locality. The methodology behind the case study presented here could readily be applied elsewhere and would be particularly useful to handheld EDXRF studies of museum specimens
- ItemOpen AccessEvidence of a therapsid scavenger in the Late Permian Karoo Basin, South Africa(2012) Fordyce, Nicholas; Smith, Roger; Chinsamy, AnusuyaDicynodonts are an extinct group of herbivorous non-mammalian therapsids (‘mammal-like’ reptiles) that are widely known from terrestrial Permo-Triassic strata throughout Pangaea. Dicynodont fossil remains are common within the Late Permian Beaufort Group of the Karoo Basin in South Africa. A large, partially articulated dicynodont skeleton recovered from the Tropidostoma Assemblage Zone is taphonomically important in having an unusual disarticulation pattern, bone surface punctures and a broken tooth of an unidentified carnivore associated with it. Here we report on the nature of the bone damage, and the identity of the carnivore that lost a canine tooth whilst scavenging the dicynodont carcass. The morphological characteristics of the serrations on the unidentified tooth were compared with those of contemporaneous carnivores, the gorgonopsians and therocephalians. Scanning electron microscopy analysis of a silicone cast of the unidentified tooth revealed distinctive 0.5-mm square-shaped serrations. Our comparative assessment of the tooth size, curvature, cross-sectional shape and morphology of the serrations revealed that the unidentified canine most closely matched Aelurognathus, a gorgonopsian known from the same assemblage zone.
- ItemOpen AccessGrowth and life habits of the Triassic cynodont Trirachodon, inferred from bone histology(2004) Botha, Jennifer; Chinsamy, AnusuyaGrowth pattern and lifestyle habits of the Triassic non−mammalian cynodont Trirachodon are deduced from bone histol−ogy and cross−sectional geometry. Several skeletal elements of Trirachodon were examined in order to document histological changes during ontogeny, as well as histovariability in the skeleton. The bone histology of all the elements consists of a moderately vascularized, periodically interrupted, fibro−lamellar bone tissue. This suggests that the overall growth of Trirachodon was probably rapid during the favourable season, but decreased or ceased during the unfavourable season. As the environment is thought to have been semi−arid with seasonal rainfall, it is possible that Trirachodon was sensitive to such environmental fluctuations. Some inter−elemental histovariability was noted where the number and prominence of growth rings varied. Limb bone cross−sectional geometry revealed a relatively thick bone wall and sup−ports earlier proposals that Trirachodon was fossorial.
- ItemOpen AccessGrowth Dynamics of Australia's Polar Dinosaurs(Public Library of Science, 2011) Woodward, Holly N; Rich, Thomas H; Chinsamy, Anusuya; Vickers-Rich, PatriciaAnalysis of bone microstructure in ornithopod and theropod dinosaurs from Victoria, Australia, documents ontogenetic changes, providing insight into the dinosaurs' successful habitation of Cretaceous Antarctic environments. Woven-fibered bone tissue in the smallest specimens indicates rapid growth rates during early ontogeny. Later ontogeny is marked by parallel-fibered tissue, suggesting reduced growth rates approaching skeletal maturity. Bone microstructure similarities between the ornithopods and theropods, including the presence of LAGs in each group, suggest there is no osteohistologic evidence supporting the hypothesis that polar theropods hibernated seasonally. Results instead suggest high-latitude dinosaurs had growth trajectories similar to their lower-latitude relatives and thus, rapid early ontogenetic growth and the cyclical suspensions of growth inherent in the theropod and ornithopod lineages enabled them to successfully exploit polar regions.
- ItemOpen AccessHistovariability and Palaeobiological Implications of the Bone Histology of the Dromornithid, Genyornis newtoni(2021-05-20) Chinsamy, Anusuya; Worthy, Trevor HThe bone microstructure of extinct animals provides a host of information about their biology. Although the giant flightless dromornithid, Genyornis newtoni, is reasonably well known from the Pleistocene of Australia (until its extinction about 50–40 Ka), aside from various aspects of its skeletal anatomy and taxonomy, not much is known about its biology. The current study investigated the histology of fifteen long bones of Genyornis (tibiotarsi, tarsometatarsi and femora) to deduce information about its growth dynamics and life history. Thin sections of the bones were prepared using standard methods, and the histology of the bones was studied under normal and polarised light microscopy. Our histological analyses showed that Genyornis took more than a single year to reach sexual maturity, and that it continued to deposit bone within the OCL for several years thereafter until skeletal maturity was attained. Thus, sexual maturity and skeletal maturity were asynchronous, with the former preceding the latter. Our results further indicated that Genyornis responded to prevailing environmental conditions, which suggests that it retained a plesiomorphic, flexible growth strategy. Additionally, our analyses of the three long bones showed that the tibiotarsus preserved the best record of growth for Genyornis.
- ItemOpen AccessNew Comparative Data on the Long Bone Microstructure of Large Extant and Extinct Flightless Birds(2022-04-15) Canoville, Aurore; Chinsamy, Anusuya; Angst, DelphineHere, we investigate whether bone microanatomy can be used to infer the locomotion mode (cursorial vs. graviportal) of large terrestrial birds. We also reexamine, or describe for the first time, the bone histology of several large extant and extinct flightless birds to (i) document the histovariability between skeletal elements of the hindlimb; (ii) improve our knowledge of the histological diversity of large flightless birds; (iii) and reassess previous hypotheses pertaining to the growth strategies of modern palaeognaths. Our results show that large extinct terrestrial birds, inferred as graviportal based on hindlimb proportions, also have thicker diaphyseal cortices and/or more bony trabeculae in the medullary region than cursorial birds. We also report for the first time the occurrence of growth marks (not associated with an outer circumferential layer-OCL) in the cortices of several extant ratites. These observations support earlier hypotheses that flexible growth patterns can be present in birds when selection pressures for rapid growth within a single year are absent. We also document the occurrence of an OCL in several skeletally mature ratites. Here, the high incidence of pathologies among the modern species is attributed to the fact that these individuals were probably long-lived zoo specimens.
- ItemOpen AccessPathologies in the Early Pliocene phocid seals from Langebaanweg South Africa(2011) Govender, Romala; Avery, Graham; Chinsamy, AnusuyaAbundant vertebrate fossils have been recorded from the Early Pliocene locality, Langebaanweg, South Africa. This study documents the pathologies evident in the 5 millionyear-old fossil phocid seal assemblage. Careful anatomical assessment of the remains revealed that 0.73% showed evidence of disease and/or trauma. The majority of the ailments were forms of osteoarthritis, although periodontitis and osteomyelitis were also evident. Some bones also showed healed fractures, suggesting that the individuals survived the traumatic event. Two cases of dental pathologies were also noted.