The imagery on this page is the basis for a paper entitled Osteological description of an embryonic skeleton of the extinct elephant bird, Aepyornis (Palaeognathae: Ratitae), by A.M. Balanoff and T. Rowe (2007, Journal of Vertebrate Paleontology Memoir 9, 27(4 Supplement), 53 pp.). The abstract is as follows:
The embryonic skeleton of the most massive bird ever discovered, the extinct elephant bird Aepyornis, has remained until this time essentially unknown. This state is due, in large part, to the reluctance to open complete, unbroken eggs. However, the advent of high-resolution X-ray computed tomography (HRCT) provides a non-destructive means of looking inside such eggs to observe the contents that they conceal. This study uses HRCT technology to digitally extract an embryonic skeleton from a complete Aepyornis egg and subsequently to aid in the systematic description of this specimen. Skeletal elements digitally retrieved from the egg include portions of the braincase, palate, rostrum, vertebral column, and both the fore- and hindlimbs. Because this specimen is at a relatively early stage of ontogenetic development, the bones that were recovered reveal morphology that typically is obliterated in the adult due to the highly fused state of the skeleton, especially seen in the skull. The usefulness of this information, however, is limited unless a level of ontogenetic maturity can be assigned to the specimen. Therefore, we use an extant phylogenetic bracket in a novel analysis comparing the morphological developmental of living ratites and chickens with this specimen of Aepyornis to assess its level of ontogenetic maturity.
About the Species
This specimen, which now resides in Explorer’s Hall at the National Geographic Society in Washington D.C., is a completely intact egg containing a disarticulated embryonic skeleton of Aepyornis. The egg was collected in Madagascar in 1967 by Luis Marden, a photographer for National Geographic Magazine.
Sitting at the bottom of the egg is a loose accumulation of bones along with an unknown matrix (possibly travertine derived from the inside of the eggshell). A number of bones are easily identifiable from a three-dimensional rendering of the egg’s contents: the tarsometatarsus, tibiotarsus, premaxilla, both frontals, and at least one vertebra. In order to facilitate a more thorough osteological study, each individual bone was digitally isolated from the two-dimensional CT scan images. All of the isolated bones may be seen in the 'Additional Imagery' section of this page. Although well over half the bones from the embryonic skeleton are preserved inside the egg, many elements from the left side of the specimen are missing (including the entire left hindlimb). It is possible that the embryo was laying on its left side at the time of death or subsequently was knocked over allowing bacterial action to break down much of that side.
The isolated bones were printed on a three-dimensional rapid prototyper in the CT lab at The University of Texas at Austin to create physical models of the bones at 300% their actual size. Casts of the printouts were then affixed together to create a reconstruction of the skull belonging to the embryo. Accordingly, this study takes what was an inaccessible specimen and, through the use of CT, allows its reconstruction and study.
Funding for the scanning was provided by a National Science Foundation Digital Libraries Initiative grant to Dr. Timothy Rowe of The University of Texas at Austin.
About this Specimen
The National Geographic egg was scanned at the High-Resolution X-Ray Computed Tomography Facility at The University of Texas at Austin. Two scans were made of this specimen on 4 October 1999. The higher resolution dataset (1024 x 1024 pixel images) proceeds from the base of the eggshell up to just above the level in which bone is found for a total of 382 slices (see coronal slice-by-slice movie). The slices are 0.25 mm thick and have an interslice spacing of 0.22 mm. The reconstructed field of view is 218 mm yielding an interpixel value of 0.21 mm/pixel.
The second dataset consists of the entire egg scanned along its long axis from the base to the apex of the eggshell for a total of 177 slices (see 'Additional Imagery' page for this animation). These slices were gathered with less resolution and were reconstructed as 512 x 512 pixel images. The slice thickness is 2.0 mm, and the interslice spacing is 1.8 mm. The reconstructed field of view is 248 mm, for an interpixel value of 0.484 mm/pixel.
Amadon, D. 1947. An estimated weight of the largest known bird. Condor 49:159-164.
Anderson, J. S., R. L. Carroll, and T. B. Rowe. 2003. New information on Lethiscus stocki (Tetrapoda: Lepospondyli: Aistopoda) from high-resolution computed tomography and a phylogenetic analysis of Aistopoda. Canadian Journal of Earth Sciences 40:1071-1083.
Andrews, C. W. 1894. On some remains of Aepyornis in the British Museum (Nat. Hist.). Proceedings of the Zoological Society of London 1894:108-123.
Andrews, C. W. 1896. On the skull, sternum, and shoulder-girdle of Aepyornis. Ibis, Seventh Series, 2:376- 389.
Andrews, C. W. 1897. Note on a nearly complete skeleton of Aepyornis from Madagascar. Geological Magazine 4:241-250.
Astre, G. 1951. L’oeuf d’Aepyornis du muséum de Toulouse. Bulletin de la Société d’Histoire Naturelle de Toulouse 86:316-320.
Balanoff, A. M. 2003. Osteological description of an embryonic elephant bird (Ratitae: Aepyornis) using high-resolution X-ray computed tomography, with a discussion of growth in Aepyornis. M.S. thesis, The University of Texas, Austin, Texas, 175 pp.
Baumel, J. J., A. S. King, J. E. Breazile, H. E. Evans, and J. C. Vanden Berge (eds.). 1993. Handbook of Avian Anatomy: Nomina Anatomica Avium, Second Edition. Publication of the Nuttall Ornithological Club, number 23. Nuttall Ornithological Club, Cambridge, Massachusetts, 779 pp.
Baumel, J. J., and L. Witmer. 1993. Osteologia; pp. 45-132 in J. J. Baumel, A. S. King, J. E. Breazile, H. E. Evans, and J. C. Vanden Berge (eds.), Handbook of Avian Anatomy: Nomina Anatomica Avium, Second Edition. Publications of the Nuttall Ornithological Club, number 23. Nuttall Ornithological Club, Cambridge, Massachusetts.
Battistini, R. 1971. Conditions de gisements des sites littoraux de subfossiles et causes de la disparition de la faune des grands animaux dans le Sud-Ouest et l’Extrême Sud de Madagascar. Taloha 4:7-18.
Berger, R., K. Ducote, K. Robinson, and H. Walter. 1975. Radiocarbon date for the largest extinct bird. Nature 258:709.
Bianconi, M. J. J. 1870. Recherches sure les affinités naturelles de l’Aepyornis. Annales des Sciences Naturelles: Zoologie et Biologie Animale, Series 5, 12:3-5.
Bibi, F., A. B. Shabel, B. P. Kraatz, and T. A. Stidham. 2006. New fossil ratite (Aves: Palaeognathae) eggshell discoveries from the Late Miocene Baynunah Formation of the United Arab Emirates, Arabian peninsula. Palaeontologia Electronica 9(2A):1-13.
Bledsoe, A. H. 1988. A phylogenetic analysis of postcranial skeletal characters of the ratite birds. Annals of Carnegie Museum 57:73-90.
Brochu, C. A. 2003. Osteology of Tyrannosaurus rex: High-Resolution Computed Tomographic Analysis of the Skull. Society of Vertebrate Paleontology Memoir 7.
Burckhardt, R. 1893. Über Aepyornis. Palæontologische Abhandlungen 2:127-145.
Burney, D. A., H. F. James, F. V. Grady, J.-G. Rafamantanantsoa, Ramilisonina, H. T. Wright, J. B. Cowart. 1997. Environmental change, extinction and human activity: evidence from caves in NW Madagascar. Journal of Biogeography 24:755-767.
Carlson, W. D., T. Rowe, R. A. Ketcham and M. W. Colbert. 2003. Geological applications of high-resolution X-ray computed tomography in petrology, meteoritics, and palaeontology; pp. 7-22 in F. Mees, R. Swennen, M. Van Geet, and P. Jacobs (eds.), Applications of X-ray Computed Tomography in the Geosciences. Geological Society of London Special Publications 215.
Clack, J. A., P. E. Ahlberg, S. M. Finney, P. Dominguez Alonso, J. Robinson, and R. A. Ketcham. 2003. A uniquely specialized ear in a very early tetrapod. Nature 425:65-69.
Clark, J. M., M. A. Norell, and T. Rowe. 2002. Cranial anatomy of Citipati osmolskae (Theropoda, Oviratorosauria), and a reinterpretation of the holotype of Oviraptor philoceratops. American Museum Novitates 3364:1-24.
Clark, J. M., J. Welman, J. A. Gauthier, and J. M. Parrish. 1993. The laterosphenoid bone of early archosauriforms. Journal of Vertebrate Paleontology 13:48-57.
Clarke, J. A. 2004. Morphology, phylogenetic taxonomy, and systematics of Ichthyornis and Apatornis (Avialae, Ornithurae). Bulletin of the American Museum of Natural History 286:1-179.
Clarke, J. A., C. P. Tambussi, J. I. Noriega, G. M. Erickson, and R. A. Ketcham. 2005. Definitive fossil evidence for the extant avian radiation in the Cretaceous. Nature 433:305-308.
Colbert, M. W. 1999. Patterns of evolution and variation in the Tapiroidea (Mammalia: Perissodactyla). Ph.d. Dissertation, The University of Texas, Austin, Texas, 464 pp.
Cooper, A., C. Lalueza-Fox, S. Anderson, A. Rambaut, J. Austin, and R. Ward. 2000. Complete mitochondrial genome sequences of two extinct moas clarify ratite evolution. Nature 409:704-707.
Cracraft, J. 1968. The lacrimal-ectethmoid complex in birds: a single character analysis. American Midland Naturalist 80:316-359.
Cracraft, J. 1974. Phylogeny and evolution of the ratite birds. Ibis 116:494-521.
Decary, R. 1937. La légende du Rokh et l’Aepyornis. Bulletin de l’Academie Malgache, Nouvelle Série, 20:107-113.
Dingus, L., and T. Rowe. 1998. The Mistaken Extinction: Dinosaur Evolution and the Origin of Birds. W. H. Freeman & Co., New York, New York, 322 pp.
Erickson, G. M., P. J. Makovicky, P. J. Currie, M. A. Norell, S. A. Yerby, and C. A. Brochu. 2004. Giganitism and comparative life-history parameters of tyrannosaurid dinosaurs. Nature 430:772-775.
Erickson, G. M., K. C. Rogers, and S. A. Yerby. 2001. Dinosaurian growth patterns and rapid avian growth rates. Nature 412:429-433.
Erickson, G. M. and T. A. Tumanova. 2000. Growth curve of Psittacosaurus mongoliensis Osborn (Ceratopsia: Psittacosauridae) inferred from long bone histology. Zoological Journal of the Linnean Society 130:51-56.
Fuller, E. 1987. Extinct Birds. Facts on File, New York, 256 pp.
Fürbringer, M. 1888. Untersuchungen zur Morphologie und Systematik der Vögel. Verlag von TJ van Holkema, Amsterdam, The Netherlands, 1751 pp.
Gaffney, E. S., H. Tong, and P. A. Meylan. 2002. Galianemys, a new side-necked turtle (Pelomedusoides: Bothremydidae) from the late Cretaceous of Morocco. American Museum Novitates 3379:1-20.
Gauthier, J. 1986. Saurischian monophyly and the origin of birds. Memoirs of the California Academy of Sciences 8:1-55.
Gefen, E., and A. Ar. 2001. Morphological description of the developing ostrich embryo: a tool for embryonic age estimation. Israel Journal of Zoology 47:87-97.
Geoffroy St.-Hilaire, I. 1851. Des ossements et des oeufs trouvés à Madagascar, dans des alluvions modernes, et provenant d’un Oiseau gigantesque. Comptes Rendus Hebdomadaires des Séances de l’Académie des Sciences 32:101-107.
Gill, B. J. 2000. Morphometrics of moa eggshell fragments (Aves: Dinornithiformes) from Late Holocene dune-sands of the Karikari Peninsula, New Zealand. Journal of the Royal Society of New Zealand 30:131- 145.
Grandidier, A. 1868. Observation of the egg-beds of Aepyornis. Ibis, Fifth Series, 4:65-68.
Hoyt, D. F., D. Vleck, and C. M. Vleck. 1978. Metabolism of avian embryos: ontogeny and temperature effects in the ostrich. Condor 80:265-271.
Huxley, T. H. 1867. On the classification of birds; and on the taxonomic value of the modifications of certain of the cranial bones observable in that class. Proceedings of the Zoological Society of London 1867:415-472.
Kearney, M., J. A. Maisano, and T. Rowe. 2005. Cranial anatomy of the worm lizard Rhineura hatcherii (Squamata, Amphisbaenia) based on high-resolution X-ray computed tomography. Journal of Morphology 264:1-33.
Ketcham, R. A., and W. D. Carlson. 2001. Acquisition, optimization, and interpretation of X-ray computed tomographic imagery: applications to the geosciences. Computers and Geosciences 27:381-400.
Last, J. T. 1894. On the bones of the Aepyornis, and on the localities and conditions in which they are found. Proceedings of the Zoological Society of London 1894:123-129.
Lee, K., J. Feinstein, and J. Cracraft. 1997. The phylogeny of ratite birds: resolving conflicts between molecular and morphological data sets; pp. 173-211 in D. P. Mindell (ed.), Avian Molecular Evolution and Systematics. Academic Press, San Diego, California.
Long, J. 2002. The Dinosaur Dealers. Allen & Unwin, Crows Nest NSW, Australia.
Long, J., P. Vickers-Rich, K. Hirsch, E. Bray and C. Tuniz. 1998. The Cervantes egg: an early Malagasy tourist to Australia. Records of the Western Australian Museum 19:39-46.
Lowe, P. R. 1930. On the relationships of the Aepyornithes to other Struthiones as revealed by a study of the pelvis of Mullerornis. Ibis, Twelfth Series, 6:470-488.
Mahé, J., and M. Sourdat. 1972. Sur l’extinction des vertebras subfossiles et l’aridification du climat dans le sud-ouest de Madagascar. Bulletin de la Société Géologique de France 14:295-309.
Maisey, J. G. 2001. A primitive chondrichthyan braincase from the early Devonian of South Africa. Journal of Vertebrate Paleontology 21:807-810.
Makovicky, P., M. A. Norell, J. M. Clark, and T. Rowe. 2003. Osteology and relationships of Byronosaurus jaffei (Theropoda: Troodontidae). American Museum Novitates 3402:1-32.
Marshall, C. L. 2000. Embryonic growth patterns in ostrich and other ratite skeletons. PhD. Dissertation, Yale University, New Haven, Connecticut, 203 pp.
Mayr, G., and J. Clarke. 2003. The deep divergences of neornithine birds: a phylogenetic analysis of morphological characters. Cladistics 19:527-553.
McDowell, S. 1948. The bony palate of birds. Part I. The Palaeognathae. Auk 65:520-549.
Milne-Edwards, A., and A. Grandidier. 1869. Nouvelles observations sur les caractères zoologiques et les affinités naturelles de l’Aepyornis de Madagascar. Annales des Sciences Naturelles: Zoologie et Biologie Animale, Series 7, 1:85-114.
Milne-Edwards, A., and A. Grandidier. 1894. Observations sur les Aepyornis de Madagascar. Comptes Rendus Hebdomadaires des Séances de l’Académie des Sciences 118:122-127.
Mivart, G. 1877. On the axial skeleton of the Struthionidae. Transactions of the Zoological Society of London 10:1-52.
Monnier, L. 1913. Paléontologie de Madagascar. VII. Les Aepyornis. Annales de Paléontologie 8:125-172.
Needham, J. 1931. Chemical Embryology. Cambridge University Press, Cambridge, United Kingdom, 2021 pp.
Parker, T. J. 1891. Observations on the anatomy and development of Apteryx. Philosophical Transactions of the Royal Society of London, B, 182:25-134.
Parker, W. K. 1866. On the structure and development of the skull in the ostrich tribe. Philosophical Transactions of the Royal Society of London 156:113-183.
Pycraft, W. P. 1900. On the morphology and phylogeny of the Palaeognathae (Ratitae and Crypturi) and Neognathae (Carinatae). Transactions of the Zoological Society of London 15:149-290.
Rahn, H., and A. Ar. 1974. The avian egg: incubation time, water loss and nest humidity. Condor 76:147-152.
Reisz, R. R, D. Scott, H.-D. Sues, D. C. Evans, and M. A. Raath. 2005. Embryos of an Early Jurassic prosauropod dinosaur and their evolutionary significance. Science 309:761-764.
Rowe, T. 1997. Comparative rates of development in Monodelphis and Didelphis. Science 275: 684.
Rowe, T., W. Carlson, and W. Bottorff. 1995. Thrinaxodon: Digital Atlas of the Skull. CD-ROM, 2nd Edition. University of Texas Press, Austin, Texas.
Rowe, T., J. Kappelman, W. D. Carlson, R. A. Ketcham, and C. Denison. 1997. High-resolution computed tomography: a breakthrough technology for earth scientists. Geotimes 42:23-27.
Rowe, T., C. A. Brochu, K. Kishi, J. W. Merck, Jr., and M. W. Colbert (eds.). 1999. Alligator: Digital Atlas of the Skull. Society of Vertebrate Paleontology Memoir 6.
Rowley, G. D. 1867. On the egg of Aepyornis, the colossal bird of Madagascar. Proceedings of the Zoological Society of London 1867:892-895.
Sauer, E. G. F., and E. M. Sauer. 1966. The behavior and ecology of the South African ostrich. Living Bird 5:45-75.
Schoch, R. R. 2003. Early larval ontogeny of the Permo-Carboniferous temnospondyl Sclerocephalus. Palaeontology 46:1066-1072.
Schoch, R. R. 2004. Skeleton formation in the Branchiosauridae: a case study in comparing ontogenetic trajectories. Journal of Vertebrate Paleontology 24:309-319.
Starck, D. 1956. Die endokraniale Morphologie der Ratiten besonders der Apterygidae und Dinornithidae. Gegenbaurs Morphologisches Jahrbuch 96:14-72.
Tattersall, I. 1987. Itampolo: two subfossil sites in Madagascar. Journal of Vertebrate Paleontology 7:342- 343.
Tooher, J.1998. Jamie and the elephant egg. Australian Property Law 6:117-143.
Turvey, S. T., O. R. Green, and R. N. Holdaway. 2005. Cortical growth marks reveal extended juvenile development in New Zealand moa. Nature 435:940-943.
Turvey, S. T., and R. N. Holdaway. 2005. Postnatal ontogeny, population structure, and extinction of the giant moa Dinornis. Journal of Morphology 265:70-86.
Tykoski, R. S., T. B. Rowe, R. A. Ketcham, and M. W. Colbert. 2002. Calsoyasuchus valliceps, a new crocodyliform from the Early Jurassic Kayenta Formation of Arizona. Journal of Vertebrate Paleontology 22:593-611.
Webb, M. 1957. The ontogeny of the cranial bones, cranial peripheral and cranial parasympathetic nerves, together with a study of the visceral muscles of Struthio. Acta Zoologica 38:81-203.
Wetmore, A. 1960. A classification for the birds of the world. Smithsonian Miscellaneous Collections 139:1- 37.
Wetmore, A. 1967. Re-creating Madagascar’s giant extinct bird. National Geographic Magazine 132:488-493.
Wheatley, P. V. 2004. A calcium isotope growth series of the domestic chicken (Gallus gallus). M. S. thesis, The University of Texas, Austin, Texas, 54 pp.
Wiedersheim, R. 1907. Einführung in die Vergleichende Anatomie der Wirbeltiere. Verlag von Gustav Fischer, Jena, Germany, 471 pp.
Wiman, C. 1935. Über Aepyornithes. Nova Acta Regiae Societatis Scientiarum Upsaliensis, Series IV, 9:1-57.
Wiman, C. 1937a. Etude sur le segment terminal de l’aile des Aepyornis et des Mullerornis. Bulletin de l’Academie Malgache, Nouvelle Série, 20:101-105.
Wiman, C. 1937b. On supernumerary metapodials in Aepyornis, the moas, and some other birds. Proceedings of the Zoological Society of London, B, 107:245-256.
Wiman, C., and T. Edinger. 1940. Sur les cranes et les encéphales d’Aepyornis et de Mullerornis. Bulletin de l’Academie Malgache, Nouvelle Série, 23:1-47.
Witmer, L. 1990. The craniofacial air sac system of Mesozoic birds (Aves). Zoological Journal of the Linnean Society 100:327-378.
Witmer, L. 1995. The extant phylogenetic bracket and the importance of reconstructing soft tissues in fossils; pp. 19-33 in J. J. Thomason (ed.), Functional Morphology in Vertebrate Paleontology. Cambridge University Press, Cambridge, United Kingdom.
Witmer, L. M. 1997. The evolution of the antorbital cavity of archosaurs: a study in soft-tissue reconstruction in the fossil record with an analysis of the function of pneumaticity. Society of Vertebrate Paleontology Memoir 3.
Worth, B. 1940. Egg volumes and incubation periods. Auk 57:44-60.