Daniel Blair Thomas

Publications (17) View all

• Article: Evidence for a krill-rich diet from non-destructive analyses of penguin bone

  Daniel B. Thomas, R. Ewan Fordyce, Keith C. Gordon
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  ABSTRACT: Diet strongly influences the chemistry of vertebrate soft and hard tissues. Bird bone and eggshell mineral preserve reliable records of prey consumption, even beyond the life of the predator, and analyses of hard tissues have usefully reconstructed avian diet. Here, we assess the feasibility of a non-destructive method for distinguishing krill-poor from krill-rich diets in penguins. Krill (Euphausiaceae) are fluoride-rich, and penguins that consume krill produce fluoride-rich bones. The chemistry of bone mineral may be elucidated using Raman spectroscopy without recourse to specialised sample preparation. Published data from the diet of six penguin species were compared to a fluoride-informative spectral band (phosphate symmetric stretch, ν1-PO43−) in the Raman spectra of penguin humeri. Penguins that consume abundant krill (e.g. Adélie and emperor) have ν1-PO43−-band positions higher than 963 cm−1, whereas penguins that primarily eat teleost fish or cephalopods (e.g. Fiordland crested, Humboldt, little blue and yellow-eyed) have ν1-PO43−-band positions lower than 963 cm−1. A krill-rich diet can therefore be determined from the Raman spectra of penguin bones. Raman spectroscopy could be a useful supplement to existing diet analysis techniques.
  Journal of Avian Biology 03/2013; 44(2):203–207. · 2.28 Impact Factor
• Article: A history of shifting fortunes for African penguins

  Daniel B. Thomas, Daniel T. Ksepka
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  ABSTRACT: Africa is home today to only a single breeding species of penguin, Spheniscus demersus (black-footed penguin), which is endangered with extinction. Spheniscus demersus has been the only breeding species of penguin to share African coastlines with humans over the last 400 000 years. Interestingly, African penguin diversity was substantially higher before the evolution of archaic humans. The fossil record indicates that a diverse assemblage of penguin species inhabited the southern African coasts for much of the Neogene. Previous excavations have identified four distinct species in Early Pliocene coastal marine deposits. Here we extend this pattern of high diversity and report the oldest record of penguins from Africa. Seventeen penguin specimens were identified from the Saldanha Steel locality, revealing the presence of at least four distinct species in South Africa during the Miocene. The largest of these species reached the size of the extant Aptenodytes patagonicus (king penguin), whereas the smallest was approximately the size of the smallest extant penguin Eudyptula minor (little blue penguin). Recovery of Miocene penguin remains is in accordance with earlier predictions of multiple pre-Pliocene colonizations of Africa and supports a higher level of ecological diversity amongst African penguins in the past
  Zoological Journal of the Linnean Society 03/2013; · 2.43 Impact Factor
• Article: Vibrational spectroscopic analyses of unique yellow feather pigments (spheniscins) in penguins.

  Daniel B Thomas, Cushla M McGoverin, Kevin J McGraw, Helen F James, Odile Madden
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  ABSTRACT: Many animals extract, synthesize and refine chemicals for colour display, where a range of compounds and structures can produce a diverse colour palette. Feather colours, for example, span the visible spectrum and mostly result from pigments in five chemical classes (carotenoids, melanins, porphyrins, psittacofulvins and metal oxides). However, the pigment that generates the yellow colour of penguin feathers appears to represent a sixth, poorly characterized class of feather pigments. This pigment class, here termed 'spheniscin', is displayed by half of the living penguin genera; the larger and richer colour displays of the pigment are highly attractive. Using Raman and mid-infrared spectroscopies, we analysed yellow feathers from two penguin species (king penguin, Aptenodytes patagonicus; macaroni penguin, Eudyptes chrysolophus) to further characterize spheniscin pigments. The Raman spectrum of spheniscin is distinct from spectra of other feather pigments and exhibits 17 distinctive spectral bands between 300 and 1700 cm(-1). Spectral bands from the yellow pigment are assigned to aromatically bound carbon atoms, and to skeletal modes in an aromatic, heterocyclic ring. It has been suggested that the penguin pigment is a pterin compound; Raman spectra from yellow penguin feathers are broadly consistent with previously reported pterin spectra, although we have not matched it to any known compound. Raman spectroscopy can provide a rapid and non-destructive method for surveying the distribution of different classes of feather pigments in the avian family tree, and for correlating the chemistry of spheniscin with compounds analysed elsewhere. We suggest that the sixth class of feather pigments may have evolved in a stem-lineage penguin and endowed modern penguins with a costly plumage trait that appears to be chemically unique among birds.
  Journal of The Royal Society Interface 01/2013; 10(83):20121065. · 4.40 Impact Factor
• Article: Chemical investigation of mineralisation categories used to assess taphonomy

  Daniel B. Thomas, Anusuya Chinsamy, Nicholas J Conard, Andrew W Kandel
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  ABSTRACT: A recent case study from the Geelbek Dunes archaeological site in Western Cape Province, South Africa revealed that, counter to prevailing notions, long-term bone survivorship is not always linked to estimates of bone density. Porosity differences between modern cancellous and compact bones of different animals and skeletal parts provided density estimates for fossil bones. Taphonomic history was inferred from the physical condition and mineral burden of the fossil bones and represented by five “mineralisation categories”. Bones in mineralisation category one had the lowest secondary mineral burden, whereas samples with very high secondary mineral contents were considered category five. Here we examine the proposed link between mineralisation category and taphonomic history by analysing fossils with non-destructive, energy dispersive x-ray fluorescence spectroscopy. We hypothesised that higher mineralisation categories should be evident as higher concentrations of elements associated with secondary minerals. However, chemical measurements could not distinguish fossil bones in mineralisation category one from those in category three. Furthermore, bones in categories four and five could not be distinguished from one another. A control of modern bone specimens and fossils in mineralisation category two formed separate and distinct clusters of principal component score values. Spectra from the Geelbek Dunes specimens were subsequently used to predict mineralisation categories for fossils from a nearby archaeological locality named Anyskop Blowout. Based on the surface chemistry, Anyskop fossils clustered in two principal groups: low (mineralisation categories one, two and three) and high (mineralisation categories four and five). Energy dispersive x-ray fluorescence spectroscopy provided useful taphonomic information for fossils from both the Geelbek Dunes and Anyskop Blowout, although this surface-biased technique was not well correlated with the five mineralisation categories.
  Palaeogeography Palaeoclimatology Palaeoecology 11/2012; 361–362:104–110. · 2.39 Impact Factor
• Source

  Available from: Russell Frew

  Article: Author's personal copy Antarctic glaciation recorded in Early Miocene New Zealand foraminifera

  Kenichi Fukuda, Daniel B Thomas, Russell D Frew, R Ewan Fordyce
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  ABSTRACT: Keywords: foraminifera geochemistry Mg/Ca thermometer palaeoclimate palaeotemperature New Zealand sedimentary sequences are important repositories of southern temperate palaeoenvironmental data, as may be interpreted from biogenic chemical signals preserved in marine microfossils. Calibration cur-ves for Mg/Ca ratios versus water temperatures were established using modern benthic foraminifera, Notorotalia and Cibicides. Notorotalia is a long-ranged endemic benthic genus with a good record in shelf sed-iments, while Cibicides allows comparisons with similar studies elsewhere. The resulting correlations were T (°C) = ln(Mg/Ca [mmol/mol] / 1.64) × 10.89 for Cibicides spp., and T (°C) = ln(Mg/Ca [mmol/mol] / 0.44) × 5.71 for Notorotalia spp. Well-preserved Early Miocene Notorotalia and Cibicides were collected for paired Mg/Ca and δ 18 O analysis from a 3.6 m section of the Mount Harris Formation spanning an estimated 60 ka and dat-ing from about 17.7 Ma (Globoconella zealandica zone, roughly middle Burdigalian, Early Miocene) within the local Altonian Stage (15.9–18.7 Ma). Mg/Ca bottom-water palaeotemperature estimates from Cibicides and Notorotalia gave concordant results: 13.3 ± 1.0 °C for Notorotalia spinosa, 15.5 ± 3.0 °C for Cibicides spp. Esti-mates of oxygen isotopic composition for Altonian sea water (δ 18 O palaeo-sw) were − 0.4 ± 0.4‰, suggesting the presence of small ice sheets on Antarctica. The method used to generate such results has far reaching im-plications for reconstructing δ 18 O palaeo-sw , and should allow Antarctic ice volume history to be finely resolved from New Zealand sequences.
  Marine Micropaleontology 04/2012; 92-93:52-60. · 2.00 Impact Factor