Protocetus are believed to have had a streamlined, whale-like body around long, but was probably primitive in some respects. Many protocetids (like
Maiacetus,
Rodhocetus) possessed well developed
innominates and hind limbs, often attached to the backbone with a
sacrum.
Protocetus are known to have had at least one sacral vertebrate, and likely possessed hind limbs and webbed toes. Despite previous proposals to the contrary, the current general consensus is that
Protocetus and other protocetids lacked tail flukes. The head of
Protocetus measured about 0.6 meters long. The jaws were long and lined with sharp
teeth. While it did not have a true
blowhole, the nostrils were placed further back on the head than in most land mammals. Unlike the more primitive
Pakicetus, the structure of the ears suggests that
Protocetus was able to hear properly underwater, although it is unlikely that it could
echolocate. Similarly, it retained sufficient olfactory apparatus to have a good
sense of smell, although it probably relied more on its eyesight to find prey.
Skull Recent high-resolution
CT scans of the
holotype skull of
Protocetus atavus (SMNS-P-11084) have provided the first detailed reconstruction of its
endocranial anatomy, offering significant insights into the evolution of sensory systems in early
cetaceans. The study revealed that
Protocetus had a relatively high
encephalization quotient (EQ) compared to other
middle Eocene cetaceans such as
Rodhocetus and
Remingtonocetus, suggesting an earlier onset of
brain enlargement than previously assumed in
whale evolution. Notably, the
olfactory bulbs and tracts were well-developed, comprising up to 3.8% of the
endocast volume, a value comparable to that of some
terrestrial mammals. The anatomy of the
nasal cavity, including the dorsal nasal meatus and vomeronasal groove, further supports the interpretation that
Protocetus retained functional airborne
olfaction. These findings challenge the long-held view that olfactory capabilities regressed early in cetacean evolution and suggest that the reduction of olfactory structures may have occurred later, potentially only after the emergence of fully aquatic forms like
basilosaurids. == See also ==