||Farmer CG. Parental Care: The Key to Understanding Endothermy and Other Convergent Features in Birds and Mammals. Am Nat. 2000 Mar 155(3):326-334. DOI: 10.1086/303323 p.328 left column 2nd paragraphPubMed ID10718729
||Shine, R. 1991. Influence of incubation requirements on the evolution of viviparity. Pages 361–369 in D. C. Deeming and M. W. J. Ferguson, eds. Egg incubation: its effects on embryonic development in birds and reptiles. Cambridge University Press, Cambridge.
||P.328 left column 2nd paragraph: "In some lizards, snakes, and ants, adults provide heat to developing embryos by basking in the sun and then returning to the nest to transfer the warmth from their bodies to their young (Shine 1988 Hölldobler and Wilson 1990). Some lizards and ants also regulate developmental temperature by transferring their eggs to different depths of the nest (Shine 1988 Hölldobler and Wilson 1990). Furthermore, in lizards and snakes natural selection for females that can behaviorally control incubation temperature has been an important selective factor in the evolution of viviparity (retainment of embryos internally: Guillette et al. 1980 Guillette 1982 Shine 1985, 1989). Apparently there is strong selection for this trait, as viviparity has evolved independently approximately 100 times within squamate reptiles (lizards and snakes primary source)."