32 
is one pair of pleurocoels, again as in the other cervicals. The 
parapophyses, though present, do not project laterally, and the 
diapophyses are reduced to small pyramidal tubercles. The neural 
spine possesses the hatchet-like shape typical of many reptilian 
axes; the epipophyses are very prominent, and a distinct hyposphene 
is present. 
According to Madsen (1976: 32), in Allosaurus the distance from 
the prezygapophyses to the postzygapophyses, relative to the width, 
is greater in the anterior cervicals, subequal in the mid-cervicals, and 
less in the posterior cervicals. In Baryonyx, the exact opposite 
obtains (see Table 1, p. 30). 
Madsen also noted (loc. cit.) that in Allosaurus the epipophyses 
are long in the anterior part of the series but decrease progressively 
backwards to only a small ridge in Ce9. The same applies to 
Sinraptor (Currie & Zhao 1993: 2056). InBaryonyx the epipophyses 
are well-developed throughout the series; the longest of all are in 
Ce8, but those (though still well-developed) are less robust than the 
epipophyses of the more anterior vertebrae. 
DORSAL REGION (Figs 22-26). The material available contains all 
or part of at least twelve dorsal vertebrae: seven preserved fairly 
complete, three centra lacking a neural arch (but one with a 
prezygapophysis and diapophysis) and two neural arches lacking a 
centrum. Like the cervicals, they were not found in articulation and 
have been ordered on their various morphological trends. If we 
assume that the total dorsal count was the usual theropod number, 
fourteen (making twenty-three presacrals altogether), then the verte- 
brae preserved seem to be: D1, D2, D3, D4 (centrum, left 
prezygapophysis and diapophysis only), DS, D6, D7 (neural arch 
diameter only), D8 (centrum only), [D9 missing entirely], D10 
(neural arch only), D11, [D12 missing entirely], D13 (centrum 
only), D14. Additionally, there are other vertebral fragments that we 
cannot assign to any particular vertebra. 
The lengths of the centra (see Table 1) are best measured ventrally, 
rim to rim. Even so, distortion and damage make it difficult to 
measure accurately, and some values (denoted with an ‘e’) are 
nothing more than reasonable estimates based on the information 
available. The first eight centra, except for D2 and the missing D7, 
are of a remarkably constant length, all being in the range 88-93 
mm. They are a little longer than the anterior cervicals (73-81 mm), 
about the same as the mid-cervical Ce6 (95 mm), and appreciably 
shorter than the posterior cervical Ce8 (120 mm). D2, however, is 
anomalous in that it too is significantly longer (108 mm). The last 
four dorsal centra, except for the missing D12, are also longer (105— 
110 mm). 
The lengths of the neural arches, measured from the anterior tip of 
the prezygapophysis to the posterior tip of the postzygapophysis, are 
likewise variable. They vary too in respect of the proportion of each 
to the length of the corresponding centrum. In the cervical vertebrae 
the neural arches are much longer than the centra so that the 
zygapophyses, anterior and posterior, project far beyond their cen- 
tra; in the most anterior dorsals, by contrast, they are scarcely any 
longer at all. However, from about D5 backwards they gradually 
increase in length until in the last dorsal (D14) they are 67% longer 
than the centra. It is interesting to speculate as to the functional 
significance of these great differences. 
Nevertheless, certain general characteristics of the dorsal verte- 
brae may be discerned. The diameters of the centra are, in general, 
more constant than the lengths referred to above, but they do display 
a few individual variations, summarized as follows: 
Anterior face, transverse diameters 80-88 mm, varying irregularly, 
except for D1 75 mm (e) (estimate), D2 103 mm, D14 104 mm 
(e); vertical diameters, 65-81 mm, increasing steadily from D3 to 
A.J. CHARIG AND A.C. MILNER 
Fig. 20 Baryonyx walkeri, holotype, BMNH R9951; cervical vertebrae it) 
(from top downwards) anterior, left lateral, and posterior views. A, axis; 
B, Ce3. x 0.25. 
D11, except for [D1 80 mm, D2 85 mm], D13 96 mm, D14 9@_— 
mm. | 
Posterior face, transverse diameters, 88-102 mm, varying irregu 
larly, except for D8 70 mm, D14 114 mm; vertical diameters) 
77-88 mm, varying irregularly, except for D13 98 mm (e), D149 
mm (e). | 
