Synsacra of the Eocene Antarctic penguins: new data on spinal maturation and an insight into their role in the control of walking

Open access


The synsacrum is an important element of the axial skeleton in birds, both volant and flightless. Little is known about the maturation of this complex bone in penguins. In this work, the supposedly ontogenetically youngest known synsacrum of early penguins was described. The analysis of this specimen, collected within the Eocene La Meseta Formation of Seymour (Marambio) Island, Antarctic Peninsula, revealed that this bird had attained at least the fledging stage of growth. Studies of three mature synsacra recovered from the same formation focused on the synsacral canals and, using indirect reasoning, their contents. These analyses revealed that the lumbosacral intumescence of the spinal cord and its extensions, the transverse canals, had been developed roughly like those in extant penguins (and also swifts and cormorants). The neural spine extensions (a non−nervous tissue) tracing the transverse grooves of the dorsal wall of the synsacral canal are currently considered as involved in the control of walking. The presented data suggest that such a sense organ gained its current penguin configuration by the late Eocene.

ACOSTA HOSPITALECHE C. and JADWISZCZAK P. 2011. Enigmatic morphological disparity in tarso− metatarsi of giant penguins from the Eocene of Antarctica. Polish Polar Research 32: 175-180.

BAUMEL J.J. and RAIKOW R.J. 1993. Arthrologia. In: J.J. Baumel (ed.) Handbook of avian anatomy: nomina anatomica avium. Nuttall Ornithological Club, Cambridge, MA: 133-187.

BAUMEL J.J. andWITMER L.M. 1993. Osteologia. In: J.J. Baumel (ed.) Handbook of avian anatomy: nomina anatomica avium. Nuttall Ornithological Club, Cambridge, MA: 45-132.

BREAZILE J.E. and KUENZEL W.J. 1993. Systema nervosum central. In: J.J. Baumel (ed.) Handbook of avian anatomy: nomina anatomica avium. Nuttall Ornithological Club, Cambridge, MA: 493-554.

BUTLER A.B. and HODOS W. 2005. Comparative vertebrate neuroanatomy: evolution and adapta− tion. Wiley, Hoboken, New Yersey: 744 pp.

CLARKE J.A.,KSEPKA D.T., STUCCHI M.,URBINA M.,GIANNINI N.,BERTELLI S.,NARVÁEZ Y. and BOYD C.A. 2007. Paleogene equatorial penguins challenge the proposed relationship between biogeography, diversity, and Cenozoic climate change. Proceedings of the National Academy of Sciences (PNAS) 104: 11545-11550.

DUBBELDAM J.L. 1993. Systema nervosum periphericum. In: J.J. Baumel (ed.) Handbook of avian anatomy: nomina anatomica avium. Nuttall Ornithological Club. Cambridge, MA: 555-584.

ELLIOT D.H. and TRAUTMAN T.A. 1982. Lower Tertiary strata on Seymour Island, Antarctic Penin− sula. In: C. Craddock (ed.) Antarctic Geoscience. The University of Wisconsin Press, Madison: 287-297.

GIFFIN E.B. 1990. Gross spinal anatomy and limb use in living and fossil reptiles. Paleobiology 16: 448-458.

JADWISZCZAK P. 2006. Eocene penguins of Seymour Island, Antarctica: Taxonomy. Polish Polar Research 27: 3-62.

JADWISZCZAK P. 2012. Partial limb skeleton of a “giant penguin” Anthropornis from the Eocene of Antarctic Peninsula. Polish Polar Research 33: 259-274.

JADWISZCZAK P. 2013. Taxonomic diversity of Eocene Antarctic penguins: a changing picture. In: M.J. Hambrey, P.F. Barker, P.J. Barrett, V. Bowman, B. Davies, J.L. Smellie and M. Tranter (eds) Antarctic Palaeoenvironments and Earth−Surface Processes. Geological Society, Special Publications (London) 381: 129-138.

JADWISZCZAK P. and ACOSTA HOSPITALECHE C. 2013. Distinguishing between two Antarctic spe− cies of Eocene Palaeeudyptes penguins: a statistical approach using tarsometatarsi. Polish Polar Research 34: 237-252.

JADWISZCZAK P. and CHAPMAN S.D. 2011. The earliest fossil record of a medium−sized penguin. Polish Polar Research 32: 269-277.

JADWISZCZAK P. and MÖRS T. 2011. Aspects of diversity in early Antarctic penguins. Acta Palaeontologica Polonica 56: 269-277.

JELGERSMA H.C. 1951. On the sinus lumbosacralis, spina bifida occulta, and status dysraphicus in birds. Zoologische Mededelingen 31: 95-110.

KAISER G. 2007. The inner bird: anatomy and evolution. University of British Columbia Press, Van− couver: 386 pp.

KSEPKA D.T., FORDYCE R.E., ANDO T. and JONES C.M. 2012. New fossil penguins (Aves, Sphenisciformes) from the Oligocene of New Zealand reveal the skeletal plan of stem penguins. Journal of Vertebrate Paleontology 32: 235-254.

MARENSSI S.A. 2006: Eustatically controlled sedimentation recorded by Eocene strata of the James Ross Basin, Antarctica. In: J.E. Francis, D. Pirrie and J.A. Crame (eds) Cretaceous-Tertiary High−Latitude Palaeoenvironments, James Ross Basin, Antarctica. Geological Society , Special Publications (London) 258: 125-133.

MYRCHA A., JADWISZCZAK P., TAMBUSSI C.P., NORIEGA J.I., GAŹDZICKI A., TATUR A. and DEL VALLE R.A. 2002. Taxonomic revision of Eocene Antarctic penguins based on tarsometatarsal morphology. Polish Polar Research 23: 5-46.

NECKER R. 1999. Specializations in the lumbosacral spinal cord of birds: morphological and behav− ioural evidence for a sense of equilibrium. European Journal of Morphology 37: 211-214.

NECKER R. 2005. The structure and development of avian lumbosacral specializations of the verte− bral canal and the spinal cord with special reference to a possible function as a sense organ of equilibrium. Anatomy and Embryology 210: 59-74.

NECKER R. 2006. Specializations in the lumbosacral vertebral canal and spinal cord of birds: evi− dence of a function as a sense organ which is involved in the control of walking. Journal of Com− parative Physiology A 192: 439-448.

PORĘBSKI S.J. 2000. Shelf−valley compound fill produced by fault subsidence and eustatic sea−level changes, Eocene La Meseta Formation, Seymour Island, Antarctica. Geology 28: 147-150.

PYCRAFT W.P. 1898. Contributions to the osteology of birds. Part II, Impennes. Proceedings of the Zoological Society of London: 958-989.

SLACK K.E., JONES C.M., ANDO T., HARRISON G.L., FORDYCE R.E., ARNASON U. and PENNY D. 2006. Early penguin fossils, plus mitochondrial genomes, calibrate avian evolution. Molecular Biology and Evolution 23: 1144-1155.

STEPHAN B. 1979. Vergleichende Osteologie der Pinguine. Mitteilungen aus dem Zoologischen Mu− seum Berlin 55 (Supplement Annalen für Ornithologie 3): 3-98.

TATUR A., KRAJEWSKI K.P. and DEL VALLE R.A. 2011. The facies and biota of the oldest exposed strata of the Eocene La Meseta Formation (Seymour Island, Antarctica). Geological Quarterly 55: 345-360.

WIMAN C. 1905. Über die alttertiären Vertebraten der Seymourinsel. Wissenschaftliche Ergebnisse der Schwedischen Südpolar−Expedition 1901-1903, 3: 1-37. Stockholm.

Polish Polar Research

The Journal of Committee on Polar Research of Polish Academy of Sciences

Journal Information

IMPACT FACTOR 2016: 0.636
5-year IMPACT FACTOR: 1.121

CiteScore 2016: 1.20

SCImago Journal Rank (SJR) 2015: 0.556
Source Normalized Impact per Paper (SNIP) 2015: 0.645


All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 119 119 17
PDF Downloads 34 34 6