EEB267H1 Lecture 21: The Mammalia: Lectures 21 and 22
29 May 2017
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Much better at hearing with 3 inner ear bones function to transmit sound waves b/c sound is transmitted much more effectively in a solid than in a liquid. Synapomorphy for mammalia is not 3 inner ear bones, it"s the addition of the incus and the malleus. We don"t use them b/c we don"t know when mammary glands appeared beast still have mammary glands. Eeb267 page 3 they have a cloaca internal fertilization (bird"s beaks are covered with keratin) underside of bill--only mammal capable of detecting electrical fields. Not lethal, it briefly incapacitates a rival long-beaked ones which have spines on their tongues internal fertilization. They have a small non-functional spur and a small number of electrosensory cells compared to to the thousands that the duck- billed platypus has. Reproductive behaviour: a female in estrus starts walking--for days-- and leaves a pheromone trail. A line of males form an echidna train behind her.
