Salamanders have the most generalized tetrapod body form
with four limbs and a tail. Their locomotion is probably very
similar to that employed by the primitive tetrapods.
While walking, salamanders combine a lateral bending of the
body with leg movements. All salamanders have long tails and
all but a few have robust and well functional limbs
(two aquatic families having reduced limbs).
Salamander skulls are reduced by the loss of many bony
elements and by the presence of numerous cartilaginous parts.
Bony elements that are never found in salamanders include:
postorbital, jugal, quadratojugal, postfrontal, postparietal,
supratemporal, supraoccipital, basioccipital and ectopterygoid.
In general, the skull of salamanders is much less compact than
that of caecilians and more robust than that of anurans.
The temporal fossae are open, the orbits large, with a
generally poorly roofed nasal region. The cranial structure of
salamanders is highly variable depending on the aquatic or
terrestrial lifestyle of the adults, but salamanders always have
an incomplete maxillary arch and a poorly developed
neurocranium (Fig. 1, see figures from the overheads).
Ribs are present, but are very reduced as in the other two
amphibian lineages. Because salamanders do not have a
rib cage, their respiration is regulated by a buccopharyngeal
pump that forces air from the mouth to the lungs. This pumping
system is formed by elements of the hyobranchial apparatus.
Because the adaptation that allows some salamanders to
protrude their tongue also relies on the hyobranchius apparatus,
only lungless salamanders (i.e., Plethodontids) have
well-protruding tongues (Fig.2).
Many salamander groups display paedomorphosis (= neoteny).
Paedomorphic forms are recognized by the retention of larval
traits during adulthood: larval tooth and bone patterns
(e.g., maxillae absent), no eyelids, retention of a functional
lateral-line system and external gills, etc.