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International Journal of Marine Science 2014, Vol.4, No.33
http://ijms.biopublisher.ca
4
region, immediately at the back of the skull, ensures
articulation with it and is composed of three vertebrae
that present relatively important variations of their
parameters. The first vertebra is a small vertebra with
fine neural spine. There are no anterior zygapophyses
in the first vertebra as this vertebra supports the skull;
instead, it has two facets for the skull to rest on. In V2
& V3, the anterior and the posterior zygapophyses are
overlapped to greater degree. The development of the
lateral parapophysis decreased posteriorly. Parapophyses
of V1-V3 are more dorsally located relative to those
of the abdominal vertebrae.
Secondly, the middle region appears to be made up of
two morphological entities: the anterior middle region
(V6-V10) and the posterior middle region (V11-V18).
Here the length of the trunk vertebrae increases and
continue in their increase until the 19
th
vertebra. The
trend of the width of the vertebrae showed was the
same shown by that of the vertebral length until the
19
th
vertebra, and then shows steady decrease until the
23
st
vertebra.
Middle region vertebrae have well developed anterior
and poeterior zygapophyses. In addition, these
vertebrae have ribs that extend ventrally toward
viscera. At V10, the lateral bony ridge that separates
the dorsal and ventral portions of each vertebra is
present.
Thirdly, the ural region includes vertebrae V18-V23. It
corresponds to the caudal peduncle and is characterized by
a fall of the four vertebral measurements studied.
The profiles corresponding to the four parameters
measured on all the vertebrae were the same in all the
specimens studied, indicating a similar trend. The
morphometric analysis shows that the vertebral axis of
the common ponyfish,
L. equulus
has complex
division. Five regions can be characterized along the
vertebral axis according to the changes of the four
parameters measured from one vertebra to another.
The vertebral profile given by the variation of the
vertebral length along the axis shows one maximum at
V19 (34.7) and two minima at V23 (18.54). There is a
great increase between V4 & V19 then the value drops
down between V19 & V21.
The variation in the vertebral height showed the
following profile: The lowest height value is observed
at V1 & V23 while the maximum value is observed at
V3. There is an increase between V1 & V3 followed
by steady decrease at V4 then the values showed
slight variation until V18 after that it drops
dramatically between V19 & V23.
There are two minima at V1 and V23 and one
maximum at V3 showed by the profile of the vertebral
width. In this profile, there is a dramatic increase in
the value between V1 & V3 then it decreases between
V4 & V5. An observed fluctuation in the values is
observed between V6 & V10 followed by a slight
increase between V11 & V19 then the values showed
a decrease between V20 & V23.
In the profile of the central width of the vertebrae,
there are two minima at V1 and V23 and one
maximum at V13. There is a slight increase between
V1 & V3followed by slight variation between V4 &
V9. The values showed gradual increase combined
with slight variation between V10 & V15 then a slight
decrease is evident between V16 & V20. The value at
V20-V22 looks very similar, but it drops dramatically
between V21 & V23.
The total number of vertebrae of
L. equulus
is 23.Out
of this number; there are 10 vertebrae as abdominal
vertebrae and 13 as caudal vertebrae. The vertebral
aspect ratios for the abdominal and caudal regions are
7.48 and 7.31 respectively.
3 Discussion
The vertebral column of
L. equulus
is composed from
five regions. This is evident through the biometric
study of four vertebral dimensions: 1) anterior
postcranial; 2) posterior postcranial region; 3) anterior
middle region; 4) posterior middle region and 5) ural
region. The 3
rd
and 4
th
regions are characterized by
variation in vertebral parameters; in regions 1, 2 &5,
these variations are characterized by a slight increased
or decreased cline of the four parameters.
The post-cranial region, immediately at the back of
the head, insures the articulation with the skull. The
first three vertebrae V1-V3 are morphologically
similar resulting into specific parameters of vertebral
length, height, width and vertebral central width. For
L. equulus
, the first vertebra plays as anterior ventral
concavity which is articulated with the basioccipital.
This first post-cranial vertebra is designed to articulate