The gular plates are oval. The medial margin is straight to slightly
curved, the lateral margin curved crescentically, the posterior end is
blunt, and the anterior end somewhat rounded. Ornamentation varies
greatly; some bones show only a few tubercles, whereas others exhibit an
almost concentric pattern of closely spaced striae. Typically there are
some tubercles in the anterior quarter or third of the total length;
these pass into longitudinally oriented striae in the posterior section.
A few have only randomly oriented, widely-spaced striae. The internal
surface is smooth.
The coronoid (K. U. no. 11428) is a triangular bone, with the apex
pointing dorsally. The lateral surface is smooth; no teeth were
observed. Moy-Thomas (1937:292, 293) mentions several tooth-bearing
coronoids in _Rhabdoderma_, but as yet these have not been seen in
_Synaptotylus_.
_Axial skeleton_
Only three specimens (K. U. nos. 786F, 787F, 11450) show parts of the
vertebral column, but isolated neural and haemal arches are numerous.
All are of the coelacanth type, having Y-shaped neural and haemal
arches, without centra. A total count of 38 was obtained, but this was
incomplete; the actual number was probably near 50. Counts of 10 and 16
haemal arches were obtained in two of the specimens. Total height of
neural arches ranges from 7.5 to 12.0 mm., and of haemal arches, from
9.0 to 12.0 mm. The shorter arches are anterior and the height increases
gradually to a maximum in the caudal region. Height of the spines varies
from 4.0 to 9.0 mm., or from twice the height of the arch in the
anterior to three times the height in the caudal region. Total width of
the base, measured in isolated specimens because lateral views in other
specimens prevented measuring width, ranges from 0.7 to 4.2 mm. The
short, broad arches having short spines occur at the anterior end of the
spinal column; the narrower arches having tall spines occur toward the
caudal end. Broken neural and haemal arches show a thin covering of bone
with a central, calcite-filled cavity, which in life may have been
filled with cartilage (Stensioe, 1932:58, fig. 20).
No ossified ribs have been observed, either isolated or in place.
For further description of the axial skeleton, see Hibbard (1933).
[Illustration: FIG. 6. _Synaptotylus newelli_ (Hibbard). Paired fin
girdles. A, pectoral girdle, lateral view, based on K. U. no. 11433, x
3.5. B, pelvic girdle basal plate, medial (?) view, based on K. U. no.
788, x 8. Anterior is toward the left.]
_Girdles and paired fins_
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