A Cretaceous terrestrial snake with robust hindlimbs and a sacrum

Article metrics


It has commonly been thought that snakes underwent progressive loss of their limbs by gradual diminution of their use1. However, recent developmental and palaeontological discoveries suggest a more complex scenario of limb reduction, still poorly documented in the fossil record2,3,4,5. Here we report a fossil snake with a sacrum supporting a pelvic girdle and robust, functional legs outside the ribcage. The new fossil, from the Upper Cretaceous period of Patagonia, fills an important gap in the evolutionary progression towards limblessness because other known fossil snakes with developed hindlimbs, the marine Haasiophis, Pachyrhachis and Eupodophis, lack a sacral region. Phylogenetic analysis shows that the new fossil is the most primitive (basal) snake known and that all other limbed fossil snakes are closer to the more advanced macrostomatan snakes, a group including boas, pythons and colubroids. The new fossil retains several features associated with a subterranean or surface dwelling life that are also present in primitive extant snake lineages, supporting the hypothesis of a terrestrial rather than marine origin of snakes.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Najash rionegrina.
Figure 2: Sacral region of the holotype of Najash rionegrina (MPCA 390–398).
Figure 3: Phylogenetic relationships of snakes showing the basal position of Najash rionegrina.


  1. 1

    Underwood, G. Simplification and regeneration in the course of evolution of Squamate reptiles. Coll. Int. Cent. Natl Rech. Sci. 266, 341–352 (1977)

  2. 2

    Cohn, M. J. & Tickle, C. Developmental basis of limblessness and axial patterning in snakes. Nature 399, 474–479 (1999)

  3. 3

    Caldwell, M. W. & Lee, M. S. Y. A snake with legs from the marine Cretaceous of the Middle East. Nature 386, 705–709 (1997)

  4. 4

    Tchernov, E., Rieppel, O., Zaher, H., Polcyn, M. J. & Jacobs, L. L. A fossil snake with limbs. Science 287, 2010–2012 (2000)

  5. 5

    Rage, J. C. & Escuillié, F. Un nouveau serpent bipède du Cénomanien (Crétacé). Implications phylétiques. C. R. Acad. Sci. Paris Earth Sci. 330, 513–520 (2000)

  6. 6

    Lee, M. S. Y., Bell, G. L. & Caldwell, M. W. The origin of snake feeding. Nature 400, 655–659 (1999)

  7. 7

    Lee, M. S. Y. & Scanlon, J. D. Snake phylogeny based on osteology, soft anatomy and ecology. Biol. Rev. 77, 333–401 (2004)

  8. 8

    Zaher, H. The phylogenetic position of Pachyrhachis within snakes (Squamata, Lepidosauria). J. Vertebr. Paleontol. 18, 1–3 (1998)

  9. 9

    Rieppel, O. & Zaher, H. The intramandibular joint in squamates, and the phylogenetic relationships of the fossil snake Pachyrhachis problematicus Haas. Fieldiana Geol. 43, 1–69 (2000)

  10. 10

    Zaher, H. & Rieppel, O. The phylogenetic relationships of Pachyrhachis problematicus, and the evolution of limblessness in snakes (Lepidosauria, Squamata). C. R. Acad. Sci. Paris Earth Sci. 329, 831–837 (1999)

  11. 11

    Apesteguía, S. & Novas, F. E. Large Cretaceous sphenodontian from Patagonia provides insight into lepidosaur evolution in Gondwana. Nature 425, 609–612 (2003)

  12. 12

    Makovicky, P. J., Apesteguía, S. & Agnolín, F. L. The earliest dromaeosaurid theropod from South America. Nature 437, 1007–1011 (2005)

  13. 13

    Corbella, H., Novas, F. E., Apesteguía, S. & Leanza, H. A. First fission-track age for the dinosaur-bearing Neuquén Group (Upper Cretaceous), Neuquén basin, Argentina. Rev. Mus. Argentino Cienc. Nat. n.s. 6, 227–232 (2004)

  14. 14

    Zaher, H. & Rieppel, O. On the phylogenetic relationships of the Cretaceous snakes with legs, with special reference to Pachyrhachis problematicus (Squamata, Serpentes). J. Vertebr. Paleontol. 22, 104–109 (2002)

  15. 15

    Rieppel, O., Kluge, A. G. & Zaher, H. Testing the phylogenetic relationships of the Pleistocene snake Wonambi naracoortensis Smith. J. Vertebr. Paleontol. 22, 812–829 (2002)

  16. 16

    Scanlon, J. D. Cranial morphology of the Plio-Pleistocene giant madtsoiid snake Wonambi naracoortensis. Acta Palaeontol. 50, 139–180 (2005)

  17. 17

    Polcyn, M. J., Jacobs, L. L. & Haber, A. A morphological model and CT assessment of the skull of Pachyrhachis problematicus (Squamata, Serpentes), a 98 million year old snake with legs from the Middle East. Palaeontol. Electr. 8, 1–24 (2005)

  18. 18

    Rieppel, O. & Head, J. J. New specimens of the fossil snake genus Eupodophis Rage & Escuillié, from Cenomanian (Late Cretaceous) of Lebanon. Mem. Soc. Ital. Sci. Nat. Mus. Civ. Stor. Nat. Milano 32, 1–26 (2004)

  19. 19

    Caldwell, M. W. & Albino, A. Exceptionally preserved skeletons of the Cretaceous snake Dinilysia patagonica Woodward, 1901. J. Vertebr. Paleontol. 22, 861–866 (2002)

  20. 20

    Swofford, D. L. PAUP*. Phylogenetic Analysis Using Parsimony (*and Other Methods). Version 4 (Sinauer, Sunderland, Massachusetts, 2003)

Download references


We thank O. Rieppel, H. W. Greene, J. C. Rage, F. Novas and A. Scanferla for discussion and review of earlier drafts; M. Reguero, S. Bargo, J. Bonaparte and A. Kramarz for access to material; P. Gallina for finding the holotype; A. Scanferla, A. B. Carvalho and M. Isasi for preparation of the specimens; and L. Lobo for the illustrations. This research was supported by the Jurassic Foundation (to S.A.) and the Fundação de Amparo à Pesquisa do Estado de São Paulo BIOTA/FAPESP (to H.Z.). The Agencia Cultura of Río Negro Province provided the exploration permits. Author Contributions S.A. was Chief Investigator and Head of the excavation campaigns in La Buitrera. H.Z. is responsible for the elaboration of the data matrix and phylogenetic analysis.

Author information

Correspondence to Sebastián Apesteguía or Hussam Zaher.

Ethics declarations

Competing interests

Reprints and permissions information is available at npg.nature.com/reprintsandpermissions. The authors declare no competing financial interests.

Supplementary information

Supplementary Data

This file includes a list of characters, the data matrix in Nexus format, and a list of apomorphies for the strict consensus of two equally parsimonious trees resulting from the phylogenetic analysis. (PDF 267 kb)

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Apesteguía, S., Zaher, H. A Cretaceous terrestrial snake with robust hindlimbs and a sacrum. Nature 440, 1037–1040 (2006) doi:10.1038/nature04413

Download citation

Further reading


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.