The characteristics of modern lizard teeth have often been overlooked as an aid to classification. In order to identify isolated teeth or rows of teeth on the jaws of Quaternary lizard fossils, we observed many modern lizard skulls with complete tooth rows, and thereby discovered that there are different patterns of tooth arrangement which are a significant aid to classification and also valuable in distinguishing lizard tooth fragments or isolated teeth. Our observations suggest that lizard teeth can be divided into three major types: 1) Homodont, pleurodont with single-cusp. This kind of teeth is usually slender and closely spaced. Teeth number 20-30 or more. The smaller-sized lizards, such as Gekkos gecko, G. Japonicus, Eumeces chinensis (Fig.1:A,a), E. xanthi, Leiolopisma tsinlingensis (Fig.1:B,b), L.reevesii, Lygosoma indicum, Platyurus platyurus and Hemidactylus frenatus, have this kind of arrangement. 2) Heterodont, subacrodont or pleurodont, with single-conical cusp teeth at the anterior of the tooth row and with flat-conical bicuspid teeth posteriorly. There are about 18-19 check teeth. Eremias argus (Fig.1:C, c), E.multiocellata and E. brenchltyi have this kind of arrangement. 3) Heterodont, with single-conical cusp teeth in the anterior part of the tooth row and with tricuspid, subacrodont teeth posteriorly. There are vertical grooves between the teeth on the external side of the lower jaw. The fourth tooth in most species is canine-like. There are 16 or less check teeth. The larger-sized lizards, such as Phrynocephalus przewalski, P. frontalis (Fig.1:D,d), Japalura splendida, J. flaviceos(Fig.1:E,e), Calotes versicolor and Leioleps belliana etc. possess this kind of arrangement. Evolutionary trends in lizard teeth are briefly discussed .
