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Remingtonocetidae

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Remingtonocetidae is a diverse family of early aquatic mammals. These animals belong to the order Cetacea. This is the same group that includes modern whales and dolphins. Remingtonocetids were important members of the Archaeoceti, which is a group of ancient whales. They lived during the Eocene epoch. These mammals were unique because they could both walk on land and swim in the water. They likely lived in habitats near the shore.

Kutchicetus minimus
Kutchicetus minimus

The physical structure of a remingtonocetid was very specialized for its environment. They possessed long and narrow skulls. Their external nare openings, or nostrils, were located on the front of the skull. Their frontal shields were narrow and their orbits, which are the eye sockets, were small. The mouth featured a convex palate. The mandibular symphysis, where the two halves of the lower jaw meet, was incompletely fused. Their teeth were also quite distinct. The anterior teeth were flattened mediolaterally. This shape made their teeth appear similar to those of a shark.

Kutchicetus minimus
Kutchicetus minimus

Scientists use the skeleton to understand how these animals moved. The postcranial skeleton, or the body parts behind the head, provides many clues. For example, the cervical vertebrae, or neck bones, were relatively long. The sacrum, which is the part of the spine connected to the hips, was composed of four vertebrae. At least three of these were fused together. The acetabular notch was narrow or closed. On the femoral head, the fovea was absent. Because of their long, low bodies and short limbs, they looked more like mammalian crocodiles than other early whales like Ambulocetus.

Kutchicetus minimus
Kutchicetus minimus

We can imagine how a remingtonocetid moved through the water. Some researchers suggest they swam like the South American giant otter. An otter uses a long, flat tail to swim through its environment. The single specimen of Kutchicetus we know of had a long and muscular back and tail. This supports the idea of a powerful swimming motion. While they could walk on land, they were likely very comfortable in the water. Their diet varied among different types. For instance, the genus Dalanistes had a marine diet consisting of things from the sea.

Kutchicetus minimus
Kutchicetus minimus

The family is named after the paleocetologist Remington Kellogg. The name Remingtonocetidae is derived from the type genus, Remingtonocetus. This genus was named in his honor. Scientists have worked hard to classify these animals in the tree of life. Some researchers assigned them to the Odontoceti, which are the toothed whales. Others placed them in the Remingtonocetoidea or the Archaeoceti. Different scientists, including many researchers across various studies, have helped define their place within the Cetacea.

Kutchicetus minimus
Kutchicetus minimus

There are several different genera within the Remingtonocetidae family. These include the type genus, Remingtonocetus, and Andrewsiphius. The genus Attockicetus is recognized as the oldest genus in the group. Other known genera are Dalanistes, Kutchicetus, and Rayanistes. Most of what we know about their heads comes from cranial fossils. These are fossils of the skull. However, dental remains, or teeth, are quite rare to find. Most of our knowledge of their body shape comes from just one specimen of Kutchicetus.

Kutchicetus minimus
Kutchicetus minimus

Our understanding of where these animals lived has changed over time. For a long time, scientists thought they were endemic to the northern coastline of the ancient Tethys Ocean. This area is located in what is now Pakistan and India. However, the discovery of Rayanistes in Egypt showed they had a broader distribution. This means they lived in more places than we first thought. There is even a single tooth from the Castle Hayne Limestone in North Carolina, USA. If this tooth belongs to a remingtonocetid, it suggests they lived as far west as eastern North America. This would mean they traveled across the Atlantic Ocean.

Kutchicetus minimus
Kutchicetus minimus
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