Nature's experiment in dental diversity among Lake Malawi cichlids. (a) Cynotilapia afra (CA) has a crescent-shaped jaw with two rows of widely spaced unicuspid teeth. (b) Metriaclima zebra (MZ) exhibits an intermediate jaw shape with five to six rows of teeth; a first row of bicuspid teeth is followed by several lingual rows of tricuspids. (c) Labeotropheus fuelleborni (LF) has a square-shaped jaw, lined with 10 or more rows of tightly packed tricuspid teeth. The arrow marks a replacement tooth in LF. Jaws were prepared with alizarin red, which stains the bone matrix and dentine. Scale bars in the lower jaw images are 500 μm. Lower jaw images are dorsal view.