Pallotta continues his series of scientifically oriented alphabets (The Jet Alphabet Book, 1999, etc.), with this skillfully illustrated volume focused on mammal skulls as the underlying structure. Each page shows one animal skull, with a paragraph of often humorous, always interesting text that offers information about skull anatomy, similarities and differences between mammals, and scientific “detective work.” The mammal names are left for the reader to guess from clues in the text and illustrations, with some animals quite easy to guess, and others requiring much more effort from the organ encased in the human skull. Masiello’s (The Flag We Love, 2000, etc.) striking paintings show each skull in a related environment (a fox skull in a henhouse, for example), with appropriate flora and fauna clues (ants crawling on an anteater skull, a bamboo stalk in the jaw of the panda bear’s skull). On most pages there is another challenge for junior science detectives: skillfully hidden within the illustrations are one or more heads of the presidents (famous human skulls of a sort). Both the presidential names and the mammal names are included on an answer page, but it’s left up to each reader’s brainpower to match the names with the appropriate illustrations. This answer page, which also includes some nonmammal skulls, is oddly placed near the end of the alphabet rather than at the end of the volume. Touches of offbeat humor are found throughout, showing that for those who use their heads, science can be both educational and fun. (Picture book/nonfiction. 4-9)