No. 406.] DINOSAUR-AVIAN STEM. 783 
VERTEBRAL FORMUL& OF Binps.! 
4 oa | 
Li one -d o " ~ 
5 $23 tao d mM g so g 
zo |34 ixi SF. tri | ud 
z BP e bes 55s|ls5sb5s| Be 
= 2 Seias eon vogs 3t 
£g |B38|$82| 2449/2543) $52 
as ACE Ee! 5 $938 d $ e E ^ 
EE AE a e ae 4 
ti (22° FEsigks (eobsl es | 3 
Er Eg|sÉRO|sOR8|S3O0B8| Sa E 
O c a = -= a | o 
Archeopteryx2? . . | 10, t1 -= — |Itori2 21? 5,6 |200r21 
BPO 6, n2 | 54 -I 4-26 | 
Promens ....5 20, 2I 2—4 I 7-11 27-32 uns E O oe 
SHAO 5 2,3 5 7,8 27, 28 — | — 
Hesperornis? .. Ir — — — 23 14 12 
Anser cinereus. ..| 18 2 4 6 24 — o — 
Cygnus olor... | 23 2 4 5 6,7 29; 30 v poem 
Most Passeres . . “| 14 2 5 7,8 21, 22 | — | — 
From this table can be drawn the general conclusion, posi- 
tive or favorable to the common dinosaur-avian stem theory, 
that primitive birds had numerous cervicals, few dorsals, and 
numerous caudals. 
Pubis of Birds. — An important negative contribution to this 
problem is that upon the pubis by Mehnert (88), who shows 
that the pubis of birds in the earliest stages of development is 
directed forwards, like that of dinosaurs and other reptiles, and 
is secondarily shifted backwards, parallel with the ischium ; that 
the processus ileopectineus, rising mainly from the ilium, is a 
secondary structure, exclusively characteristic of birds, which 
has no homology with the falsely called prepubis of dinosaurs; 
thus the various comparisons of the bird and dinosaur pelvis 
by Huxley and others lose one of their strongest supports. 
The primitive (or embryonic) bird pelvis, however, is triradiate 
and resembles that of the primitive carnivorous dinosaurs. The 
secondary, or adaptive, bird pelvis is totally different from that 
of any dinosaur. This militates against the theory of the deri- 
vation of birds from any specialized dinosaurs, such as the 
Iguanodontia or Megalosauria, but not against the theory of a 
common dinosaur-avian stem. 
! Mainly from Newton, '93-'96, p. 849. 
2 Fürbringer, '88. 8 Marsh, '80. 
