The term kinesis, when used as a reference to the skulls of tetrapods, is defined either as 

 the movement of the upper jaw accompanied by specific elements of (or the entire) dermatocran i urn, 

 or as movement of the olfactory region of the neurocranium with respect to the rear part of the 

 axial skull (i.e., of the brain case formed of cartilage-replacement bonesl This phenomenon was 

 first described by Nitzsch in 1822, according to Bradley ( 1 9^3) » w h° discovered that the lizard 

 skull was capable of movement in the f ronto-parietal suture and in the articulation of the parietal 

 bone with the occipital. Bradley studied the chewing musculature and accompanying movements in the 

 skull of lizards. He formulated the first hypothesis of the functional significance of the movement 

 of the upper jaw in relation to the axial skull (see below) and made the first attempt to correlate 

 these movements with the functions of specific muscles. The term "cranial kinesis" was introduced 

 by Versluys (1910) for a construction of the skull in which such movements would be possible, as 

 well as the movements of the lower jaw. Versluys (l910, 1912, 1922, 1927) made a more thorough 

 analysis of tetrapod cranial kinesis. He pointed out the prevalence of kinesis among most of the 

 tetrapod groups, recent and extinct; classified various forms of kinesis, and proposed a theory of 

 cranial kinesis, according to which the tetrapod skull was primitively kinetic; kinesis was 

 inherited by the ancient tetrapods from fish-like ancestors and secondarily lost in several lines 

 of tetrapod evolu t i on . ^ From Versluys comes one of the most widely accepted hypotheses to date on 

 the functional significance of cranial kinesis. Later contributions to the study of kinesis were 

 made by Lakjer (l9 2 7), Marinelli (1928, 1936), de Jong and Brongersma (1927), Hofer (i960) and 

 various other authors. Kinesis in crossopteryg ian fishes was shown by Romer ( 1 937 P er Frazzetta 

 1962) and in some stegocephal ians ( Pf annenst iel, 193 2 > according to Frazzetta, 1962). An 

 exceptional amount of work on kinesis was devoted to the more specialized and unusual forms of 

 birds and snakes. Comparatively little attention was given to kinesis in the more primitive 

 forms of cranial kinesis (in lizards). A valuable contribution to the study of cranial kinesis 

 in lizards was the work of Frazzetta (1962). Frazzetta by using motion pictures, demonstrated the 

 connection between the movement of the upper jaw and the seizing and consumption of prey, and made 

 the first b iomechan ical analysis of the work of the jaw muscles, 



- p. 1399 - 



responsible for movement of the upper jaw. Frazzetta presented a new hypothesis on the functional 

 significance of cranial kinesis (see below). However, Frazzetta, in his analysis of cranial 

 kinesis, focused his attention on one form ( Varanus ), giving less attention to the features of 

 cranial kinesis of other forms studied by him. The type of cranial kinesis exhibited by Varanus , 

 as our work has shown, cannot be considered as either the most primitive or the most widespread 

 among lizards. For a clear presentation of the evolution of skull kinesis and its functional 

 significance, a comparison of kinesis in various skulls beginning with the more primitive forms, 

 i s necessary. 



MATERIALS AND METHODS 



We have 

 macleay i . I qu 

 ret icula tus ( 

 Eumeces schne 

 f Varan i dae) , 

 ( Gekkon i dae) , 

 from the mate 

 of Moscow Uni 

 lections. We 

 preparat i ons 

 freshly k i lie 

 of 1 i zards wa 

 aq i 1 i s were t 

 ANSSSR, N.N 

 wish to expre 

 zoology, Mosc 

 the opportuni 

 Zoolog ical In 

 Zoological Mu 



studied skull structur 

 ana sp . ( Iguanidae), A_ 

 Agamidae), Lacerta med 

 i der i * t Ma b u y a aurata . 

 Tera tosc i ncus sc i ncus * 



Oph i saurus apodus * ( A 

 rial of the Zoological 

 vers i t y, the Cha ir of 



studied the details 

 of skulls of 11 specie 

 d species of Varanidae 

 s studied. Motion pic 

 aken by an aide [assis 

 Kalandadze, to whom th 

 ss our sincere thanks 

 ow University) for dis 

 ty to work with museum 

 st itute ANSSSR, I . S. 

 seum, Moscow Uni vers it 



e i n Sphenodon p_ 



ama caucas ica *. 



.a*, L_. aq i 1 i s *. 



Trachysaurus ru 

 , Gecko gecko *, 

 nguidae), Tup i na 



Institute of th 

 Vertebrate Zoolo 

 f cran ial k i nes i 

 s of lizards 2 (w 



In add i t i on, 

 tures of the eat 

 tant , or proba t i 

 e author is very 

 to B. S. Mateev 

 cussion of our 



materials, the 

 Darevsk i i , and 

 y, D. N. Hofmann 



uncta tus and the fol 

 A. lehmann i 1 ^. sa 

 E rem ias arquta . E. 

 qosus (Scincidae), 

 Platydactylus quttat 

 mb i s sp . ( T e i i da e ) , 

 e Akademiia Nauk USS 

 gy of Moscow Un i vers 

 s in the alcoholic 

 i th sk in removed) a 

 the jaw musculature 

 ing of prey by Aqama 

 onerj at the Paleont 

 indebted for his he 

 r,d F. Ya. Dzerzhins 

 esults and for crit 

 head of the herpetol 

 ead of the evolution 



lowing lizards: Cyclur 

 qu i nolenta *. Phrynoceph 

 gramm ica (Lacertidae), 

 aranus qr i seus *. V. n i 1 

 us . Gymnodactylus casp i 

 Zonurus cordylus * (Zonu 

 R, the Zoological Museu 

 ity and from our own co 

 wet) connective tissue 

 d also in the skulls of 

 of nine other species 



ceucas ica and Lacerta 

 olog ical I nst itute of t 

 lp in the work. We als 

 kyj (chair of vertebrat 

 cal remarks, and for gi 

 ogy division of the 



ry morphology division 



*An alternate hypothesis of the antiquity of the akinetic skull and independence of development 

 of kinesis in various lines of vertebrate evolution was developed by Edgeworth (1935)- 

 Edgeworth's views do not survive serious criticism and have not received general acceptance. 

 The names of these [llj lizards are designated by an asterisk in the list given above. 



