After Emry & Storer, 1981, Joeckel & Stavas, 1996, McKenna & Bell, 1997 and Norris, 2000
<==o †Protoceratidae Marsh, 1891 |--o †Leptotragulus [Leptotragulinae] | |-- †L. ?clarki | `-- †L. medius `--+--o †“Leptoreodontinae” [Leptotragulinae, in part] | |--o †Leptoreodon [Camelomeryx, Hesperomeryx, Merycodesmus] | | |-- †L. major | | |-- †L. pusillus | | |-- †L. edwardsi | | `-- †L. leptolophus | |-- †Toromeryx | |-- †Heteromeryx dispar | `?- †Poabromylus kayi `--+--o †Protoceratinae Marsh, 1891 | |--o †Pseudoprotoceras Cook, 1934 | | |-- †P. longinaris Cook, 1934 | | |-- †P. semicinctus (Cope, 1889) | | `-- †P. taylori Emry & Storer, 1981 | |-- †Protoceras celer | `-- †Paratoceras `--o †Synthetoceratinae |--o †Synthetoceratini | |-- †Lambdoceras | |-- †Prosynthetoceras texanus | `-- †Synthetoceras tricornatus `--o †Kyptoceratini |-- †Syndyoceras cooki `-- †Kyptoceras amatorum
Reference(s):
- Carroll, R. L., 1988: Vertebrate paleontology and evolution.
–W. H. Freeman and company, New York, 1988, 698. - Carroll, R. L., 1988: Appendix. 594-648.
in Carroll, R. L., 1988: Vertebrate paleontology and evolution.
–W. H. Freeman and company, New York, 1988, 698. - Emry, R. J. & Storer, J. E. 1981: The hornless protoceratid Pseudoprotoceras (Artiodactyla: Tylopoda) in the Early Oligocene of Saskatchewan and Wyoming.
–Journal of Vertebrate Paleontology: vol. 1, #1, pp. 101-110. - Joeckel, R. M. & Stavas, J. M., 1996: Basicranial anatomy of Syndyoceras cooki (Artiodactyla, Protoceratidae) and the need for a reappraisal of tylopod relationships.
–Journal of Vertebrate Paleontology: Vol. 16, #2, pp. 320-327 - McKenna, M. C. & Bell, S. K., (eds.) 1997: Classification of mammals – above the species level.
–Columbia University Press, New York, 1997, xii-631 - Norris, C. A., 2000: The cranium of Leptotragulus, a hornless protoceratid (Artiodactyla:
Protoceratidae) from the Middle Eocene of North America.
–Journal of Vertebrate Paleontology: Vol. 20, #2, pp. 341-348