Post-natal Development in the Linear and Tric Morphometrics of the ...

Post-natal Development of the Camelidae Skull 233
Fig.1. Measurments of the camel skull (dorsal view): inion (I), nasion
(N), prosthion (P), zygion (Z), skull length (1), cranial length (2)
viscerocranial length (3), maximum width of neurocranium (4) and
maximum zygomatic width (5).
100/cranial length), facial index (maximum zygomatic width
100/viscerocranial length), cranial volume and skull weight.
The measurement of the cranial volume was commenced by
plugging the foramina opening into the cranial cavity with
fresh Plasticine.The cavity was then filled with fine-quality rice
seeds to the level of the distal border of the foramen magnum.
When the cranial cavity was filled with rice seeds via the
foramen magnum, the space immediately cranial to the
tentorium cerebelli osseum was also filled.The contents were
emptied and measured in a measuring cylinder calibrated in
millilitres.
Linear and angular dimensions of the cranial base (Fig 3)
The cranial base, as traditionally defined in growth studies of
the mammalian skull, consists (in the median plane) of a
segment, termed the basicranial axis, stretching from the
pituitary region to the ventral (anterior) margin of the foramen
magnum, an anterior extension from the pituitary region to the
junction of the frontal and nasal bones, and a posterior
extension from the ventral to the dorsal margin of the foramen
magnum (Moore, 1981).
Fig.2. Measurments of the camel skull (lateral view): inion (I),
prosthion (p), nasion (N), skull length (1), viscerocranial length (2) and
cranial length (3).
Fig.3. Sagittal sections of the skull of camel to show linear and
angular dimensions of cranial base.E ¼ endobasion; N ¼ nasion; O ¼
opisthion; PP ¼ pituitarty point.The anterior and posterior basicranial
angles are shown by dashed lines.
Statistical analysis
Changes in the craniometric measurements within and between
age groups were statistically evaluated by the least-squares
analysis of variance using the GLM procedures of the
statistical analysis system (SAS, 1996).
Results
The craniometric measurements and the cranial volume
increased significantly with age.The results recorded in Table
1 reveal that the skull, cranial and viscerocranial lengths,
neurocranium and the maximum zygomatic widths, increased
significantly with age.Although the skull and facial indices
increased, the cranial index insignificantly decreased in value
with age.
The results of the correlation analyses of the features
examined in the immature and mature animals are recorded in
Table 2.
There was a strongly positive correlation among the skull,
viscerocranial lengths, cranial and the maximum zygomatic
width in the immature and mature animals.
The maximum width of the neurocranium showed a strong
significant positive correlation with all of the measurements in
both the immature and mature groups of camels.
The skull and facial indices in the immature and mature
camels were found to have a positive correlation with the
maximum zygomatic width and the skull, cranial and viscerocranial
lengths in the immature and mature animals.The
cranial index was found to have a negative correlation with all
of the craniometric measurements with the exception of the
viscerocranial length, which was insignificantly positive.
However, a similar comparison in the immature and mature
groups of camels showed that the cranial index had a weak
negative significant correlation with the cranial length.
A positive correlation between the facial index and the
maximum width of the neurocranium was found in the
immature and mature camels.
The correlation between the skull and facial indices in both
groups was positive and strong.The correlation between the
cranial and facial indices was weakly significant in the
immature and mature camels.