Download HONR219D Due 3/08/16 Homework V More Vertebrate Anatomy

HONR219D
Due 3/08/16
Homework V
More Vertebrate Anatomy!
This week’s assignment builds on homework IV by examining the vertebrate
skeleton in greater detail. We start with the vertebral column. Here are the major
features of the vertebra of a land vertebrate. Major features:
• The vertebra consists of two major regions: a neural arch that forms the lateral
walls and roof of the neural canal through which the spinal cord passes, and a
centrum (plural centra) – an ossification of the notochord. In most land
vertebrates, these arise as separate elements in the embryo, but fuse before
adulthood.
• Adjacent neural arches articulate with one another through paired
zygapophyses. Centra articulate at their anterior and posterior surfaces. Ribs
articulate at special surfaces that may involve both the neural arch and centrum.
1. The figure below shows a dorsal vertebra of a salamander in dorsal (left), ventral
(center), and lateral (right) view. In each view, label the following:
• Neural arch
• Centrum
• Zygapophyses
• Ribs (in the salamander, these are fused to the rib articulations.)
• For each view, draw an arrow indicating the anterior direction.
In may fossil vertebrates (and a few living ones) the centra and neural arches remain
separate throughout life. To make it more interesting, vertebrates have experimented
with many evolutionary pathways toward the ossification of the notochord. The figure
above shows the ancestral pattern for air-breathing vertebrates, who had two separate
kinds of notochord ossifications:
• Intercentrum (plural intercentra) are tangerine-segment-shaped elements that
ossify on the ventral midline of the notochord and, in some creatures, become
quite large.
• Pleurocentrum (plural pleurocentra) are paired plate-shaped elements that
ossify on either side of the dorsal surface of the notochord. In some creatures,
these become large enough to fuse on the midline.
The items below show a short series of dorsal vertebrae in lateral view. In each, identify:
• neural arch
• intercentrum
• pleurocentrum
• notochord (only if visible)
Careful, ribs are shown in some illustrations but not in others.
2.
3.
4.
5. One of the samples in questions 2 – 4 is of
a purely aquatic, water-breathing vertebrate.
Which one is it?
What evidence led you to this conclusion?
Now on to skulls. In most vertebrates these can seem frustratingly complex, so you must
learn to break them down into their most basic components, which are shown in the
schematic below. These are usually covered by bones of the skull roof, so those are
omitted here. There are three regions:
• The neurocranum or braincase is a three-dimensional midline structure that
houses the brain and special sense capsules (otic and nasal capsules and eyes.)
• The mandibular arch or jaws. These consist of two sets of paired elements that
articulate posteriorly at the jaw joint:
• Palatoquadrates or upper jaws on top
• Meckel’s cartilages or lower jaws below
• The hyoid arch that sits behind the jaws and connects them to the
neurocranium. It mirrors the mandibular arch by having upper and lower elements
that meet in a joint:
• Hyomandibula above, that articulates to the neurocranium and supports
the jaw joint
• Ceratohyal below, that forms the skeleton of the floor of the mouth and
tongue (if there is one.)
Items 6 and 7 are illustrations of actual vertebrate skulls. In each, identify:
• neurocranium
• hyomandibula
• palatoquadrate
• ceratohyal
• Meckel’s cartilage
6. Squalus acanthias the
spiny dogfish (a shark)
7. Eusthenopteron foordi a
fossil bony fish. (Shown
without its bony skull
roof.)
We can’t ignore the bones of the skull roof forever. They each have names. In
HONR291D we only ask you to learn the names of a few of them, however. Here they
are shown in Amia calva, the bowfin – a ray-finned fish.
• The opercular
series covers the gill
chamber.
• Three toothbearing bones of the
mouth. In the upper
jaw:
• Premaxilla in
front
• Maxilla behind
In the lower jaw:
• Dentary
Note: In the course of evolution, many animals have lost the teeth from these elements,
while retaining the bones.
Identify the premaxilla, maxilla, dentary, and opercular series in the following items:
8.
9.
10.