Figure 4 in A new fossil species of Procellaria (Aves: Procellariiformes) from the Pliocene of New Zealand

Figure 4. Principal component analysis for the skeletal measurements of the three Procellaria species that are most similar in morphology to the new species: P. aequinoctialis, P. conspicillata and P. westlandica. (A) Biplot of the first and second principal component scores. (B) Projection of the principal component vectors (loadings) of the tested parameters onto the PC1-PC2 biplot. Colours represent the different species:P. aequinoctialis = green; P. conspicillata = blue; P. westlandica = yellow; P. altirostris sp. nov. = red.