. Advances in the study of mammalian behavior. Mammals. Structure, Development, and Function 131 1000 500 100 50 .05. Body weight or volume (kgs or litre) Fig. 8. Brain-body relations in various groups to illustrate the reptilian base from which mammalian encephalization was derived. Symbols are: open circle, Archaeopteryx; closed circles, dinosaurs; triangles, pterosaurs. (From Hopson, 1977; copyright Annual Reviews, Inc.). living reptiles. Mammals evolved from that grade of encephaliza- tion. The data are portrayed in Fig. 8. The earliest mammal with a known endocast is Tnconodon mor- dax (&
. Advances in the study of mammalian behavior. Mammals. Structure, Development, and Function 131 1000 500 100 50 .05. Body weight or volume (kgs or litre) Fig. 8. Brain-body relations in various groups to illustrate the reptilian base from which mammalian encephalization was derived. Symbols are: open circle, Archaeopteryx; closed circles, dinosaurs; triangles, pterosaurs. (From Hopson, 1977; copyright Annual Reviews, Inc.). living reptiles. Mammals evolved from that grade of encephaliza- tion. The data are portrayed in Fig. 8. The earliest mammal with a known endocast is Tnconodon mor- dax ("T" in Fig. 10) an Upper Jurassic species of about 150 million years ago. Its EQ^ was (Jerison, 1973)—an approximate value, of course, but accurate enough to indicate that it was significantly more encephalized than its reptilian ancestors (typical EQ^ for rep- tiles relative to the mammalian average was and is about ). The story of the early mammals is important enough to be graphed with all of the archaic mammalian species. Tnconodon (T) was evidently at about the same grade of encephalization as the living Virginia opossum {Didelphis virginiana) (D; EQ_ = .25 or so) and significantly above fossil and living reptiles as shown in Fig. 9. The other archaic mammals labeled in Fig. 9 are early Tertiary species that lived between 40 and 60 million years ago. The Mesozoic grade of encephalization in mammals persisted for at least 100 million Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Eisenberg, John Frederick; Kleiman, Devra G; American Society of Mammalogists. [Shippensburg, Pa?] : American Society of Mammalogists
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Keywords: ., bookcentury1900, bookcollectionbiodiversity, booksubjectmammals
