P MORPHOLOGY OF THE VERTEBRATE SKULL af 
(fig. 25) the dentition according to Broom (’11, p. 916) indicates 
“an articulation for the lower jaw which permits of some degree 
of antero-posterior movement.” Does not this antero-posterior 
movement imply a functionally streptostylic quadrate? 
The second point raised by Gaupp to exclude the Theriodontia 
from mammalian ancestry is the 
wide separation of the quadrate from the true auditory region, through 
a long lateral parotic process (of the quadrate) as in Rhynchocephalia 
and lizards, whereas in mammals the movable incus (quadrate) lies 
close to the auditory capsule and the parotic process is reduced to the 
low facialis ridge (of the incus), beneath which runs the facial nerve. 
But because the Cynognathus quadrate retains certain pr mitive 
reptilian characters, exhibited also by the quadrate of Rhyncho- 
cephalia and lizards, is that a good reason for excluding the 
Theriodonts from the ancestry of the mammalia? Why not then 
exclude all reptiles that possess a quadrate, that is to say, all 
reptiles whatsoever? It is of course entirely consistent with the 
“Theriodont theory’ that the lower Theriodonts, i. e., the Thero- 
cephalians, should have a large and typically reptilian quadrate, 
while the higher Theriodonts, e. g., Gomphognathus of the Cyno- 
dontia, have a reduced quadrate with a reduced parotic process.!° 
‘What other “high and one-sided specializations” are there, 
common to all Theriodonts (i.e., Therocephalia + Cynodontia) 
and not simply generic, which would exclude Theriodontia in 
their ordinal characters from being the morphological archetypes 
of the Mammalia? Are they excluded because they retain such 
primitive reptilian characters as a pineal foramen (lost in Sesamo- 
don) separate prefrontals, postorbitals, ‘reptilian’ pterygoid and 
the full complement of upper and lower jaw bones? Are they 
excluded because some of them, in combination with certain 
generic specializations, such as the grinding dentition and en- 
larged squamosals of Gomphognathus, have also acquired many 
characteristically mammalian characters? What could be more 
mammalian except the mammals themselves, than Gompho- 
gnathus, in the details of its palate, pterygoids, vomer, alisphe- 
10 Cf. figure 11, Broom, 1911. The long parotic process of the ‘alisphenoid’ is 
entirely separate, according to Broom, from the parotic process of the quadrate. 
[But see Postscript below. ] 
