<==o Steatornithidae (rasvalinnut) [paraphyletic??] |--o †Preficinae | |-- †Prefica nivea Olson, 1987 | `--o †Paraprefica | |-- †P. kelleri | `-- †P. major `--o †Steatornithinae (nykyrasvakehrääjät; modern oilbirds) `--o Steatornis (rasvakehrääjät) |?- †S. sp. `-- S. caripensis (rasvakehrääjä; oilbird)
Feduccia, A., 1996: The origin and evolution of birds.
–Yale University Press, New Haven and London, 1996, xii-420
Lokki, J., Jännes, H. & Nikander, P. J., 1992: Otavan lintutieto.
–Kustannusosakeyhtiö Otava, Helsinki, Finland, 1992, pp. 1-440
Translated from: Perrins, C. M. (ed.), 1990: The Illustrated encyclopaedia of birds.
–Headline Book Publishing Plc., London, England, 1990
Olson, S. L., 1985: The fossil record of birds. 79-239.
in Farner, D., King, J. & Parkes, K. (eds.), 1985: Avian Biology. vol VIII.
–Academic Press, New York. 1985.