Friday, October 24, 2014

Identification of an optimal sampling position for stable isotopic analysis of bone collagen of extinct moa (Aves: Emeidae)

TitleIdentification of an optimal sampling position for stable isotopic analysis of bone collagen of extinct moa (Aves: Emeidae)
Publication TypeJournal Article
Year of Publication2011
AuthorsHoldaway, RN, Hawke, DJ, Bunce, M, Allentoft, ME
JournalNotornis
Volume58
Issue1
Pagination1-7
Type of ArticleFull article
Keywordsbone collagen, carbon-13, Euryapteryx curtus, moa, nitrogen-15, Pachyornis elephantopus, stable isotopes
Abstract

Stable isotopic (δ13C; δ15N) analysis of bone collagen and other refractory biological materials is a mainstay of palaeoecological research, but comparability between individuals depends on homogeneity within the sample specimens. Long bones of extinct New Zealand moa display lines of arrested growth that reflect prolonged development over several years, leading to potential systematic inhomogeneity in stable isotopic enrichment within the bone. We tested whether the isotopic content within a Euryapteryx curtus tibiotarsus is homogeneous by measuring δ15N and δ13C values in 6 adjacent 1cm-diameter cortical bone cores arranged along the bone axis from each of the proximal and distal ends. We then measured isotopic ratios in 5 radial slices of a core from the mid-shaft of a Pachyornis elephantopus tibiotarsus to see if there was any depth (ontogenetic) effect at a single sampling point. The δ13C value increased with distance from the proximal bone end, but neither δ13C nor δ15N values in samples from the distal end of the bone were correlated with position. Within mid-shaft cortical bone, the δ13C value decreased with depth but δ15N values were constant. Sampling the entire depth of cortical bone from the caudal surface at the distal end of the tibiotarsus, if feasible, therefore provides a spatially homogenous material, free of maturation effects on stable isotopic composition. If for any reason that position cannot be sampled, the outer (radial) layer at the mid-shaft can be substituted.

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