Outline shape analysis of penguin humeri: a robust approach to taxonomic classification

Keywords: Extant Sphenisciformes, genus-level systematics, elliptical Fourier harmonics, multivariate ordination


Humeri have been useful bones in taxonomic determinations of extinct penguins. In the context of neontological taxonomic studies, however, their potential remains unsatisfactorily explored. Here, the variation of the overall closed-outline shape of 60 humeri, assignable to five genera of extant penguins, was investigated. A set of normalized outlines was quantified via elliptical Fourier analysis and subjected to linear discriminant analysis on principal component scores extracted from harmonic coefficients. These geometric representations proved to be a source of easily extractable genus-level taxonomic information. The constructed model provided meaningful discrimination between taxa: the first two linear discriminants captured almost 90% of between-group variance. A cross-validation method based on jackknifing yielded 93% correct identifications, and statistically significant differences between group centroids were also detected (multivariate analysis of variance, p < 0.05). Predictions of genus membership for the intentionally noisy test data (20 outlines) were accurate in 80% of cases.


Download data is not yet available.


Acosta Hospitaleche C., Degrange F.J., Tambussi C.P., Corrado N. & Rustán J.J. 2006. Evaluación de los caracteres del húmero de los pingüinos actuales y fósiles para su uso con fines sistemáticos. (Evaluating the characteristics of humeri of current and fossil penguins for systematic purposes.) Ornitologia Neotropical 17, 81–94.

Acosta Hospitaleche C. & Di Carlo U. 2010. The coracoids in functional and morphological studies of penguins (Aves, Spheniscidae) of the Eocene of Antarctica. Rivista Italiana di Paleontologia e Stratigrafia 116, 23–34, doi: 10.13130/2039-4942/5938.

Acosta Hospitaleche C., Griffin M., Asensio M., Cione A.L. & Tambussi C. 2013. Middle Cenozoic penguin remains from the Patagonian Cordillera. Andean Geology 42, 490–503, doi: 10.5027/andgeoV42n1-a0n.

Acosta Hospitaleche C., Jadwiszczak P., Clarke J.A. & Cenizo M. 2019. The fossil record of birds from the James Ross Basin, West Antarctica. Advances in Polar Science 30, 251–273, doi: 10.13679/j.advps.2019.0014.

Bonhomme V., Picq S., Gaucherel C. & Claude J. 2014. Momocs: outline analysis using R. Journal of Statistical Software 56, 1–24, doi: 10.18637/jss.v056.i13.

Chávez Hoffmeister M. 2014. Phylogenetic characters in the humerus and tarsometatarsus of penguins. Polish Polar Research 35, 469–496, doi: 10.2478/popore−2014−0025.

Dryden I.L. & Mardia K.V. 2016. Statistical shape analysis. Chichester: Wiley.

Gavryushkina A., Heath T.A., Ksepka D.T., Stadler T., Welch D. & Drummond A.J. 2017. Bayesian total evidence dating reveals the recent crown radiation of penguins. Systematic Biology 66, 57−73, doi: 10.1093/sysbio/syw060.

Giardina C.R. & Kuhl F.P. 1977. Accuracy of curve approximation by harmonically related vectors with elliptical loci. Computer Graphics and Image Processing 6, 277–285, doi: 10.1016/S0146-664X(77)80029-4.

Izenman A.J. 2013 Modern multivariate statistical techniques: regression, classification, and manifold learning. New York, NY: Springer, doi: 10.1007/978-0-387-78189-1_8.

Jadwiszczak P. 2010. New data on the appendicular skeleton and diversity of Eocene Antarctic penguins. In D. Nowakowski (ed.): Morphology and systematics of fossil vertebrates. Pp. 44−50. Wroclaw: DN Publishers.

Jadwiszczak P. 2012. Partial limb skeleton of a “giant penguin” Anthropornis from the Eocene of Antarctic Peninsula. Polish Polar Research 33, 259–274, doi: 10.2478/v10183-012-0017-0.

Jadwiszczak P. & Mörs T. 2019. First partial skeleton of Delphinornis larseni Wiman, 1905, a slender-footed penguin from the Eocene of Antarctic Peninsula. Palaeontologia Electronica 22.2.32A, 1−31, doi: 10.26879/933.

Kendall D.G. 1977. The diffusion of shape. Advances in Applied Probability 9, 428–430, doi: 10.2307/1426091.

Ksepka D.T. & Ando T. 2011. Penguins past, present, and future: trends in the evolution of the Sphenisciformes. In G. Dyke & G. Kaiser (eds.): Living dinosaurs: the evolutionary history of modern birds. Pp. 155–186. Chichester: Wiley.

Kuhl F. & Giardina C. 1982. Elliptic Fourier features of a closed contour. Computer Graphics and Image Processing 18, 236–258, doi: 10.1016/0146-664X(82)90034-X.

Livezey B.C. 1989. Morphometric patterns in recent and fossil penguins (Aves, Sphenisciformes). Journal of Zoology 219, 269–307, doi: 10.1111/j.1469-7998.1989.tb02582.x.

Louw G.J. 1992. Functional anatomy of the penguin flipper. Journal of the South African Veterinary Association 63, 113–120.

Mayr G., dePietri V.L., Love L., Mannering A.A., Bevitt J.J. & Scofield R.P. 2020. First complete wing of a stem group sphenisciform from the Paleocene of New Zealand sheds light on the evolution of the penguin flipper. Diversity 12, article no. 46, doi: 10.3390/d12020046.

Oksanen J., Guillaume Blanchet F., Friendly M., Kindt R., Legendre P., McGlinn D., Minchin P.R., O’Hara R.B., Simpson G.L., Solymos P., Stevens M.H.H., Szoecs E. & Wagner H. 2019. Vegan: community ecology package. R package version 2.5-6. Accessed on the internet at https://CRAN.R-project.org/package=vegan.

Quinn G.P. & Keough M.J. 2002. Experimental design and data analysis for biologists. Cambridge: Cambridge University Press.

Raikow R.J., Bicanovsky L. & Bledsoe A.H. 1988. Forelimb joint mobility and the evolution of wing-propelled diving in birds. Auk 105, 446–451, doi: 10.1093/auk/105.3.446.

R Core Team 2019. R: a language and environment for statistical computing. Vienna: R Foundation for Statistical Computing.

Schreiweis D.O. 1982. A comparative study of the appendicular musculature of penguins (Aves: Sphenisciformes). Smithsonian Contributions to Zoology 341, 1–46, doi: 10.5479/si.00810282.341.

Simpson G.G. 1946. Fossil penguins. Bulletin of the American Museum of Natural History 87, 1–99.

Simpson G.G. 1971. Review of fossil penguins from Seymour Island. Proceedings of the Royal Society of London B 178, 357–387, doi: 10.1098/rspb.1971.0070.

Shufeldt R.W. 1901. Osteology of the penguins. Journal of Anatomy and Physiology 35, 390–404, doi: https://doi.org/10.1086/277965.

Slack K.E., Jones C.M., Ando T., Harrison G.L., Fordyce R.E., Arnason U. & Penny D. 2006. Early penguin fossils, plus mitochondrial genomes, calibrate avian evolution. Molecular Biology and Evolution 23, 1144–1155, doi: 10.1093/molbev/msj124.

Stephan B. 1979. Vergleichende Osteologie der Penguine. (Comparative osteology of the penguin.) Mitteilungen aus dem Zoologischen Museum in Berlin 55, 3–98.

Storer R.W. 1960. Evolution in diving birds. Proceedings of XII International Ornithological Congress 2, 694–707.

Thomas D.B., Ksepka D.T., Holvast E.J., Tennyson A.J.D. & Scofield P. 2019. Re-evaluating New Zealand’s endemic Pliocene penguin genus. New Zealand Journal of Geology and Geophysics, doi: 10.1080/00288306.2019.1699583.

Walsh S.A., MacLeod N. & O’Neill M. 2008. Analysis of spheniscid humerus and tarsometatarsus morphological variability using DAISY automated image recognition. Oryctos 7, 129–136.

Williams T.D. 1995. The penguins. Oxford: Oxford University Press.

Zelditch M.L., Swiderski D.L., Sheets H.D. & Fink W.L. 2004. Geometric morphometrics for biologists. A primer. Burlington: Elsevier Academic Press.
How to Cite
Jadwiszczak P. (2020). Outline shape analysis of penguin humeri: a robust approach to taxonomic classification. Polar Research, 39. https://doi.org/10.33265/polar.v39.4370
Research Articles