Cutmarks andpost-mortem striations in fossil human teeth

A sample of 24 teeth from 10 human fossils have been examined by Scanning Electron Microscope. Large striations attributable to feeding behavior (dental cutmarks) and/or topost-mortem damage have been found in five of the specimens (Broken Hill, Tabun I, Skhul 4, La Quina 5 and Malarnaud). At high magnification, it is possible to observe differences between the internal morphology of these structures andpost-mortem striations that were probably inadvertently made during the process of study and cleaning the fossil remains. Cutmarks can be related to the behavior of placing meat or other matter between the anterior teeth while cutting pieces of it with a stone tool. The presence of this type of scratching on the enamel surface of teeth might be indirectly used as indicative of meat consumption.     

Extraction of osteocalcin from fossil bones and teeth

Osteocalcin (also called 'bone Gla-protein') was detected in fossil bovid bones ranging from 12,000 years to 13 million years old and in rodent teeth 30 million years old. Both the antigenic activity and the protein-bound Gla-residues have remained intact. The protein is indistinguishable from recent bovine osteocalcin when analyzed by HPLC using ion exchange and size exclusion columns. If sufficient amounts can be extracted and an adequate purification procedure is established, this would be the first time that amino acid sequences in a protein from fossil bones may be determined. Such sequence data could offer a new approach to the phylogenetic study of extinct taxa.     

Two macaque fossil teeth from the Japanese Pleistocene

Two fossil teeth of the Pleistocene macaque of Japan are stated to be those ofMacaca cf.fuscata. One of them is a lower canine tooth found in the Shiriya mine in northern Japan. It has been thought that the fossil assemblage of the Shiriya mine is of the late Pleistocene. The canine concerned is not distinguishable from the lower right one of the living female Japanese monkey. The other is a lower molar taken from the Ando quarry in western Japan. The fossil assemblage from the Ando quarry or from sites neighbouring the quarry indicates that the age of the molar can be traced back to the middle Pleistocene. The molar concerned has a somewhat buccolingually depressed crown as compared with that of the living Japanese monkey (Macaca fuscata).     

Biology meets engineering: The structural mechanics of fossil and extant shark teeth

The majority of studies on the evolution and function of feeding in sharks have focused primarily on the movement of cranial components and muscle function, with little integration of tooth properties or function. As teeth are subjected to sometimes extreme loads during feeding, they undergo stress, strain, and potential failure. As attributes related to structural strength such as material properties and overall shape may be subjected to natural selection, both prey processing ability and structural parameters must be considered to understand the evolution of shark teeth. In this study, finite element analysis was used to visualize stress distributions of fossil and extant shark teeth during puncture, unidirectional draw (cutting), and holding. Under the loading and boundary conditions here, which are consistent with bite forces of large sharks, shark teeth are structurally strong. Teeth loaded in puncture have localized stress concentrations at the cusp apex that diminish rapidly away from the apex. When loaded in draw and holding, the majority of the teeth show stress concentrations consistent with well designed cantilever beams. Notches result in stress concentration during draw and may serve as a weak point; however they are functionally important for cutting prey during lateral head shaking behavior. As shark teeth are replaced regularly, it is proposed that the frequency of tooth replacement in sharks is driven by tooth wear, not tooth failure. As the tooth tip and cutting edges are worn, the surface areas of these features increase, decreasing the amount of stress produced by the tooth. While this wear will not affect the general structural strength of the tooth, tooth replacement may also serve to keep ahead of damage caused by fatigue that may lead to eventual tooth failure. J. Morphol., 2011. © 2010 Wiley‐Liss, Inc.     

清流狐狸洞人类牙齿化石记述

１９８９年在福建清流狐狸洞发现的五枚人类牙齿化石,全部出自晚更新世地层,伴生的动物群表明其地质时代为晚更新世晚期。这五枚晚期智人的牙齿在形态上无异于现代人．     

Color changes in modern and fossil teeth induced by synchrotron microtomography

Studies using synchrotron microtomography have shown that this radiographic imaging technique provides highly informative microanatomical data from modern and fossil bones and teeth without the need for physical sectioning. The method is considered to be nondestructive; however, researchers using the European Synchrotron Radiation Facility have reported that color changes sometimes occur in teeth during submicron scanning. Using the Advanced Light Source, we tested for color changes during micron‐level scanning and for postexposure effects of ultraviolet light. We exposed a 2.0‐mm wide strip (band) to synchrotron light in 32 specimens, using multiple energy levels and scan durations. The sample included modern and fossilized teeth and bone. After scanning, the specimens were exposed to fluorescent and direct ultraviolet light. All teeth showed color changes caused by exposure to synchrotron radiation. The resulting color bands varied in intensity but were present even at the lowest energy and shortest duration of exposure. Color bands faded during subsequent exposure to fluorescent and ultraviolet light, but even after extensive ultraviolet exposure, 67% (8/12) of UV‐exposed teeth retained some degree of induced color. We found that the hydroxyapatite crystals, rather than the organic component, are the targets of change, and that diagenesis appears to impact color retention. Color changes have significance beyond aesthetics. They are visible indicators of ionization (chemical change) and, therefore, of potential physical damage. It is important for researchers to recognize that synchrotron microtomography may damage specimens, but adopting suitable safeguards and procedures may moderate or eliminate this damage. Am J Phys Anthropol 149:172–180, 2012. © Wiley Periodicals, Inc.     

Paleoanthropological applications of amino acid racemization dating of fossil bones and teeth

The general principals of the amino acid racemization based dating technique are discussed. The results obtained at Olduvai Gorge (Tanzania) and Zhoukoudian (China) are presented as an illustration of the paleoanthropological application of racemization dating. Tooth enamel provides the best material for the racemization dating of Middle to Lower Pleistocene deposits, although in some cases bones also yield reliable ages. The racemization method provides a means of dating teeth and bones which are too old for radiocarbon dating. Only small samples are required and processing procedures are straightforward. The technique is particularly useful in paleoanthropological studies since hominid fossils can be directly dated.     

Hyolith-type microstructure in a mollusc-like fossil from the Early Cambrian of Yunnan, China

A phosphatized bilaterally symmetrical, spirally coiled conch from the Lower Cambrian phosphates of the Meishucunian Stage of eastern Yunnan, China, is composed of two well-preserved layers. The outer one is built of longitudinal mineralized fibres not strictly parallel to each other, but may anastomose or branch. The fibres form comarginal ribs with transversal grooves between them, corresponding to growth stages. In the ribs, the fibres are arranged closely and are steeply inclined towards the apex, while in the grooves the fibres are subparallel to the conch surface and more loosely packed. Small elliptic and triangular holes are situated within and between the fibres of the outer layer. The inner layer consists of transversal fibres running around the conch. They are almost parallel to each other but partly separated by narrow discontinuous slits. Despite overall morphological similarity of the conch to shells of some early Cambrian molluscs, the observed orthogonal configuration of longitudinally oriented fibrous structures of the outer layer and transversal fibres of the inner layer is found in orthothecid hyoliths, phosphatized microstuctures of which have been described from the Lower Cambrian of the Siberian Platform. The new material from the Yangtze Platform supports a conclusion of a distinctive type of microstructure available in hyoliths different from molluscan microstructures available from the Lower Cambrian.     

The colour of fossil feathers

Feathers are complex integumentary appendages of birds and some other theropod dinosaurs. They are frequently coloured and function in camouflage and display. Previous investigations have concluded that fossil feathers are preserved as carbonized traces composed of feather-degrading bacteria. Here, an investigation of a colour-banded feather from the Lower Cretaceous Crato Formation of Brazil revealed that the dark bands are preserved as elongate, oblate carbonaceous bodies 1-2mum long, whereas the light bands retain only relief traces on the rock matrix. Energy dispersive X-ray analysis showed that the dark bands preserve a substantial amount of carbon, whereas the light bands show no carbon residue. Comparison of these oblate fossil bodies with the structure of black feathers from a living bird indicates that they are the eumelanin-containing melanosomes. We conclude that most fossil feathers are preserved as melanosomes, and that the distribution of these structures in fossil feathers can preserve the colour pattern in the original feather. The discovery of preserved melanosomes opens up the possibility of interpreting the colour of extinct birds and other dinosaurs.     

Growth patterns of fossil vertebrates as deduced from bone microstructure: case studies from India

Bone microstructure is affected by ontogeny, phylogeny, biomechanics and environments. These aspects of life history of an extinct animal, especially its growth patterns, may be assessed as fossil bone generally maintains its histological integrity. Recent studies on the bone histology of fossil vertebrates from India encompass different types of temnospondyls and dicynodonts from different Permian and Triassic horizons. The examined taxa show that they had distinct bone histology and varied growth patterns. The Early Triassic trematosaurids had an overall fast growth, which contrasts with that of the Middle and Late Triassic temnospondyl taxa examined. The dicynodonts on the other hand, were characterized by an overall fast growth with periodic interruptions, variable growth rates dependent on ontogeny and indeterminate growth strategy. A comparative study encompassing several neotherapsid genera including the dicynodonts shows significant evolutionary trends towards determinate growth strategy and reduced developmental plasticity.     

The fossil pollen genus Classopollis

The generic name Classopollis Pflug, 1953, is considered as a valid usable name for Mesozoic spherical pollen characterized by a subequatorial circumpolar canal, a thickened equatorial band, a distal cryptopore, and a proximal tetrad scar. A study of Classopollis exine revealed the absence of nexine. Classopollis has a worldwide distribution in Upper Triassic-Turonian strata. Plants producing Classopollis have affinity with araucarian and/or gnetalean conifers. They occupied well-drained soils of upland slopes and lowlands near coastal areas, preferring the warm climate of transgressive seas.     

The original colours of fossil beetles

Structural colours, the most intense, reflective and pure colours in nature, are generated when light is scattered by complex nanostructures. Metallic structural colours are widespread among modern insects and can be preserved in their fossil counterparts, but it is unclear whether the colours have been altered during fossilization, and whether the absence of colours is always real. To resolve these issues, we investigated fossil beetles from five Cenozoic biotas. Metallic colours in these specimens are generated by an epicuticular multi-layer reflector; the fidelity of its preservation correlates with that of other key cuticular ultrastructures. Where these other ultrastructures are well preserved in non-metallic fossil specimens, we can infer that the original cuticle lacked a multi-layer reflector; its absence in the fossil is not a preservational artefact. Reconstructions of the original colours of the fossils based on the structure of the multi-layer reflector show that the preserved colours are offset systematically to longer wavelengths; this probably reflects alteration of the refractive index of the epicuticle during fossilization. These findings will allow the former presence, and original hue, of metallic structural colours to be identified in diverse fossil insects, thus providing critical evidence of the evolution of structural colour in this group.