MORPHOLOGY OF THE VERTEBRATE SKULL 30 
fastened both to the angular, which gave rise to the tympanic 
bone, and to the retroarticular process of the articular, which 
gave rise to the manubrium of the malleus. With the reduction 
of the ‘reptilian’ tympanic membrane the hyoid became sepa- 
rated from the extracolumella (as it does in many lizards) and 
migrated to a new insertion point on the periotic (but by what 
path is not clear). 
Such an hypothesis or series of hypotheses seems to embody 
the best available evidence concerning the origin of the manu- 
brium, the origin of the tympanic bone and the fate of the extra- 
columella. While this matter is still unfortunately in the specu- 
lative stage, the evidence tending to show that the tympanic 
bone has been derived either from the supraangular (van Kampen 
05) or preferably from the angular (Gaupp ’11, pp. 100, 461) 
seems of far greater value than the evidence cited by Gadow® 
to show that the tympanic bone has been derived from the rep- 
tilian quadrate. 
ORIGIN OF MAMMALS 
From the foregoing pages it will be evident that the most 
prominent neontologists have looked almost exclusively to Lacerta, 
Sphenodon, Echidna, Lepus and other recent forms for answers — 
to the intricate problems of skull morphology. Gaupp, in his 
luminous address (710) before the Eighth International Zoologi- 
cal Congress, explicitly defends this procedure on the ground 
that only the recent types afford us an insight into the highly 
important morphology of the chondrocranium. From various 
reasons contemporary neontologists have shown a disinclination 
to extend their morphological studies and conclusions to the 
extinct types. Although the skull morphology of Cynognathus 
has been known in its essential facts for many years, it is only 
recently that Gaupp has discussed the Theriodont lower jaw, 
which he now recognizes as a fulfilment of his neontological 
prophecies. 
‘For a criticism of Gadow’s view, see Gregory, The orders of mammals, pp. 
128-125. 
