Mystacodon selenensis

Overview

Mystacodon selenensis is an early toothed mysticete. It is known from Late Eocene seas of Peru. The presence of teeth in an ancient relative of baleen whales is intriguing.^[1][2]

Key facts

The species name selenensis derives from Selene, the goddess of the moon. Its discovery locality, Playa Media Luna, means Half Moon Beach. The name of this small whale thus contains its discovery setting on the present-day Peruvian coast.^[1][2]

Time and place

It is known from Late Eocene strata approximately 36.4 million years old. The material comes from the Pisco Basin in present-day Peru. South American coastal strata enable research into the marine life of early mysticetes.^[1][2]

The time range describes source context, not the complete duration of this species.

Size, form and skeleton

The snout and palate are described as relatively broad and flat. The skull and lower jaw bear teeth, and vertebrae, part of the forelimbs, and the left pelvis are also known. Several regions together reveal the body of an early mysticete.^[1][2]

Mystacodon is estimated to have been approximately 3.75–4 m long. Researchers reconstructed overall size by applying several proportional equations to skull length and width.^[3]

Habitat and reproduction

Microfossils and sediments associated with the specimen were interpreted as indicating a quiet outer-shelf marine environment. A 2019 study proposed that prey selection and capture may have been varied before specialized filter feeding. Its broad snout and teeth are studied alongside its marine setting.^[1][2]

Fossil discovery

A 2017 study introduced specimen MUSM1917 as a new early mysticete. The partial skeleton of one individual from Half Moon Beach is held in the natural history museum in Lima, Peru. A detailed comparison of its skull, teeth, and postcranial bones followed in 2019.^[1][2]

References

1. Lambert et al.2017 — Mystacodon, an early mysticete from Peru
2. 2019 study — The body and classification of Mystacodon
3. Lambert et al. (2017) — Mystacodon, an Eocene early mysticete from Peru
4. Lambert et al.2019 — A four-legged whale from Peru

Research questions

How did a toothed relative of baleen whales feed? Researchers compare its broad, flat snout, teeth, and palate with other ancient whales. This is important for investigating changes leading toward the feeding apparatus of living baleen whales.^[1][2]

Observation

Move your gaze from the head and teeth to the flippers, then imagine the pelvis farther back in the body. Comparison with living baleen whales reveals features that changed through a long evolutionary history.^[1][2]