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Christian Sidor, Ph.D.

Curator, Vertebrate Paleontology
Associate Director of Research & Collections


(206) 221-4181

Christian Sidor's Web Site

Dr. Sidor


Origin of Mammals
The synapsid lineage includes modern mammals and all of their extinct relatives. This lineage is remarkably ancient, dating minimally to the Middle Pennsylvanian (~300 Ma). The earliest synapsids (such as the familiar sailback, Dimetrodon) were reptilian in overall cast (e.g., ectothermic physiology, simple teeth, sprawling posture, etc.), but within 100 million years nearly all of the anatomical features that characterize mammals were in place. In what sequence were these mammalian features evolved? What was the rate at which these characters were acquired? Were these features evolved once or independently in multiple groups? The bulk of my research has been devoted to gathering detailed anatomical and phylogenetic data to address these questions in a quantitative framework.

Tetrapod Evolution during the Permian and Triassic
The largest mass extinction in Earth history occurred at the end of the Permian, roughly 251 Ma. Although the cause of this catastrophe has been difficult to pin down, its effects on terrestrial ecosystems are clearly seen in the fossil record. To date, most of the data on extinction and survivorship for this critical interval come from the Karoo Basin of South Africa. However, this restricted geographic and sedimentary area constrains the degree to which broader statements can be made about global patterns of tetrapod evolution. For this reason, I have been actively involved in fieldwork that expands the geographic coverage of Permian and Triassic localities. Recent exploration in Antarctica, Laos, and Niger have produced fossils that change the way paleontologists view Pangean faunas.


2005-2008 Assistant Professor of Biology and Curator of Vertebrate Paleontology, University of Washington

2001-2004 Assistant Professor of Anatomy, New York College of Osteopathic Medicine, Old Westbury, NY

2001 Postdoctoral Fellow, National Museum of Natural History, Smithsonian Institution, Washington, DC

2000 Ph.D., Department of Organismal Biology and Anatomy, University of Chicago, Chicago, IL

1996 M.S., Department of Organismal Biology and Anatomy, University of Chicago, Chicago, IL

1994 B.S. (with Honors in Biology), Trinity College, Hartford, CT


Angielczyk, K.D., C.A. Sidor, S.J. Nesbitt, R.M.H. Smith, and L.A. Tsuji. 2009. Taxonomic revision and new observations on the postcranial skeleton, biogeography, and biostratigraphy of the dicynodont genusDicynodontoides, the subjective senior synonym of Kingoria (Therapsida, Anomodontia). Journal of Vertebrate Paleontology 29.

Weide, D.M., C.A. Sidor, K.D. Angielczyk, and R.M.H. Smith. 2009. A new record of Procynosuchus delaharpeae(Therapsida: Cynodontia) from the Upper Permian Usili Formation, Tanzania. Palaeontologia Africana 44.

Maddin, H.C., C.A. Sidor, and R.R. Reisz. 2008. Cranial anatomy of Ennatosaurus tecton (Synapsida: Caseidae) from the Middle Permian of Russia and the evolutionary relationships of Caseidae. Journal of Vertebrate Paleontology 28: 160-180.

Sidor, C.A., M.F. Miller, and J.L. Isbell. 2008. Tetrapod burrows from the Triassic of Antarctica. Journal of Vertebrate Paleontology 28: 277-284.

Sidor, C.A., R.J. Damiani, and W.R. Hammer. 2008. A new Triassic temnospondyl from Antarctica and a review of Fremouw Formation biostratigraphy. Journal of Vertebrate Paleontology 28: 656-663.

Smiley, T.M., C.A. Sidor, O. Ide, A. Maga. 2008. The vertebrate fauna of the Upper Permian of Niger. VI. First evidence of a gorgonopsian therapsid. Journal of Vertebrate Paleontology 28: 543-547.

Sidor, C.A., J.-S. Steyer, and R. Damiani. 2007. Parotosuchus (Temnospondyli: Mastodonsauridae) from the Triassic of Antarctica. Journal of Vertebrate Paleontology 27: 232-235.

Sidor, C.A., and R.M.H. Smith. 2007. A second burnetiamorph from the Upper Permian Teekloof Formation of South Africa and its associated fauna. Journal of Vertebrate Paleontology 27: 420-430.

Sidor, C.A., and P.J. Hancox. Elliotherium kersteni, a new tritheledontid from the lower Elliot Formation (Upper Triassic) of South Africa. Journal of Paleontology 80: 333-342.(PDF)

F.R. O’Keefe, C.A. Sidor, H.C.E. Larsson, A. Maga, O. Ide. Evolution and homology of the astragalus in early amniotes: new fossils, new perspectives. Journal of Morphology 267: 415-425. (PDF)

Rubidge, B.S., C.A. Sidor, and S.P. Modesto. A new burnetiamorph (Therapsida: Biarmosuchia) from the Middle Permian of South Africa. Journal of Paleontology 80: 740-749. (PDF)

Steyer, J.-S., R. Damiani, C.A. Sidor, F.R. O’Keefe, H.C.E. Larsson, A. Maga, O. Ide. The vertebrate fauna of the Upper Permian of Niger. IV. Nigerpeton ricqlesi (Temnospondyli: Cochleosauridae), and the edopoid colonization of Gondwana. Journal of Vertebrate Paleontology 26: 18-28. (PDF)

Damiani, R., C.A. Sidor, J.-S. Steyer, R.M.H. Smith, F.R. O’Keefe, H.C.E. Larsson, A. Maga, O. Ide. The vertebrate fauna of the Upper Permian of Niger—V, The primitive temnospondyl Saharastega moradiensisi. Journal of Vertebrate Paleontology 26: 559-572. (PDF)

Smith, R.M.H., B.S. Rubidge, and C.A. Sidor. A new burnetiid (Therapsida: Biarmosuchia) from the Upper Permian of South Africa and its biogeographic implications. for Journal of Vertebrate Paleontology 26: 331-343. (PDF)

Sidor, C.A., F. R. O'Keefe, R. Damiani, J.-S. Steyer, R.M.H. Smith, H.C.E. Larsson, P.C. Sereno, O. Ide, A. Maga. 2005. Permian tetrapods from the Sahara show climate-controlled endemism in Pangaea. Nature 434: 886-889. (PDF)

O'Keefe, F.R., C.A. Sidor, H.C.E. Larsson, A. Maga, O. Ide. 2005. The vertebrate fauna of the Upper Permian of Niger-III, Morphology and ontogeny of the hindlimb of Moradisaurus grandis (Reptilia, Captorhinidae). Journal of Vertebrate Paleontology 25: 309-319. (PDF)

Socha, J..J., and C.A. Sidor. 2005. Chrysopelea ornataC. paradisi (flying snakes). Behavior. Herpetological Review 36: 190-191. (PDF)

Sidor, C.A. and R.M.H. Smith. 2004. A new galesaurid (Therapsida: Cynodontia) from the Lower Triassic of South Africa. Palaeontology 46: 535-556. (PDF)

Sidor, C.A., J.A. Hopson, and A. Keyser. 2004. A new burnetiamorph therapsid from the Teekloof Formation, Permian, of South Africa. Journal of Vertebrate Paleontology 24: 938-950. (PDF)

Sidor, C.A.. 2003. The naris and palate of Lycaenodon longicepsi (Therapsida: Biarmosuchia), with comments on their early evolution in the Therapsida. Journal of Paleontology 77: 153-160. (PDF)

Sidor, C.A.., D.C. Blackburn, and B. Gado. 2003. The vertebrate fauna of the Upper Permian of Niger- II. Preliminary description of a new pareiasaur. Palaeontologia Africana 39: 42-52. (PDF)

Sidor, C.A. 2003. Evolutionary trends and the origin of the mammalian lower jaw. Paleobiology 29: 605-640. (PDF)

Sidor, C.A. and J. Welman. 2003. A second specimen of Lemurosaurusi (Therapsida: Burnetiamorpha). Journal of Vertebrate Paleontology 23: 631-642. (PDF)

Sereno, P.C., C.A. Sidor, H.C.E. Larsson, and B. Gado. 2003. A new notosuchian crocodyliform from the Early Cretaceous of Niger. Journal of Vertebrate Paleontology 23: 477-482. (PDF)

Rubidge, B.S., and C.A. Sidor. 2002. On the cranial morphology of the basal therapsids Burnetia and Proburnetia(Therapsida: Burnetiidae). Journal of Vertebrate Paleontology 22: 257-267. (PDF)

Kammerer, C.F., and C.A. Sidor. 2002. Replacement names for the therapsid genera Criocephalus Broom, 1928 andOlivieria Brink, 1965. Palaeontologia Africana 38: 71-72.

Sidor, C.A. 2001. Simplification as a trend in synapsid cranial evolution. Evolution 55:1419-1442. (PDF)

Rubidge, B.S., and C.A. Sidor. 2001. Evolutionary patterns among Permo-Triassic therapsids. Annual Review of Ecology and Systematics 32: 449-480. (PDF)

Modesto, S., C. A. Sidor, B. S. Rubidge, and J. Welman. 2001. A second varanopseid skull from the Upper Permian of South Africa: implications for Late Permian 'pelycosaur' evolution. Lethaia 34:249-259. (PDF)

Sereno, P.C., H.C.E. Larsson, C.A. Sidor, and B. Gado. 2001. The giant crocodyliform Sarcosuchus from the Cretaceous of Africa. Science 294: 1516-1519. (PDF)

Sidor, C.A. 2000. Evolutionary trends and relationships within the Synapsida. Ph. D. Dissertation, University of Chicago, 370 pp.

Wagner, P. J., and C. A. Sidor. 2000. Age rank / clade rank metrics-sampling, taxonomy, and the meaning of "stratigraphic consistency." Systematic Biology 49:463-479.

Carrano, M.T., and C.A. Sidor. 1999. Theropod hind limb disparity revisited: comments on Gatesy and Middleton (1997). Journal of Vertebrate Paleontology 19: 602-605.

Larsson, H.C.E., and C.A. Sidor. 1999. Unusual crocodyliform teeth from the Kem Kem (Late Cretaceous: Cenomanian) of southeastern Morocco. Journal of Vertebrate Paleontology

Rubidge, B. S., S. P. Modesto, C. A. Sidor, and J. Welman. 1999. Eunotosaurus from the Ecca-Beaufort contact in the Northern Cape: Implications for Karoo Basin development. South African Journal of Science 95:553-555.

Sereno, P.C., A.L. Beck, D.B. Dutheil, H.C.E. Larsson, G.H. Lyon, B. Moussa, R.W. Sadleir, C.A. Sidor, D.J. Varricchio, G.P. Wilson, J.A. Wilson. 1999. Cretaceous sauropods from the Sahara and the uneven rate of skeletal evolution among dinosaurs. Science 286: 1342-1347.

Sidor, C.A., and J.A. Hopson. Ghost lineages and "mammalness": assessing the temporal pattern of character acquisition in the Synapsida. Paleobiology 24: 254-273.

Sereno, P.C., A.L. Beck, D.B. Dutheil, B. Gado, H.C.E. Larsson, G.H. Lyon, J.D. Marcot, O.W.M. Rauhut, R.W. Sadleir,C.A. Sidor, D.J. Varricchio, G.P. Wilson, J.A. Wilson. 1999. A long-snouted predatory dinosaur from Africa and the evolution of spinosaurids. Science 282: 1298-1302.

Sidor, C.A., and D.G. Blackburn. 1999. Effects of testosterone administration on mass and protein content of the forelimb muscles in male leopard frogs, Rana pipiens Journal of Experimental Zoology 280: 28-37.

Sereno, P.C., D.B. Dutheil, M. Iarochene, H.C.E. Larsson, G.H. Lyon, P.M. Magwene, C.A. Sidor, D.J. Varricchio, and J.A. Wilson. 1996. Predatory dinosaurs from the Sahara and Late Cretaceous faunal differentiation. Science 272: 986-991.

Blackburn, D.G., R.S. Darrell, K.T. Lonergan, R.P. Mancini, and C.A. Sidor. 1995. Test of a model system: differential androgen sensitivity of sexually dimorphic forelimb muscles of leopard frogs. Amphibia-Reptilia 16: 351-356.