Aetiocetus

Aetiocetus is a genus of extinct basal mysticete, or baleen whale that lived 33.9 to 23.03 million years ago, in the Oligocene in the North Pacific ocean, around Japan, Mexico, and Oregon. It was first described by Douglas Emlong in 1966 and currently contains known four species, A. cotylalveus, A. polydentatus, A. tomitai, and A. weltoni. These whales are remarkable for their retention of teeth and presence of nutrient foramina, indicating that they possessed baleen. Thus, Aetiocetus represents the transition from teeth to baleen in Oligocene mysticetes. Baleen is a highly derived character, or synapomorphy, of mysticetes, and is a keratinous structure that grows from the palate, or roof of the mouth, of the whale. The presence of baleen is inferred from the fossil record in the skull of Aetiocetus. Aetiocetus is known from both sides of the Pacific Ocean: it was first documented in Oregon, United States, but it is also known from Japan and Mexico. The genus is currently constrained to the Northern hemisphere and has little value in biostratigraphic studies of the Oligocene due to its limited occurrences across the Pacific.

Aetiocetus

Owen Allen · CC BY 2.0 · via Wikipedia/Commons. May be a photograph of a specimen, or an artist’s reconstruction — an interpretation of a skeleton, since colour and soft tissue are almost never preserved.

On record

Recorded, not inferred
Sits inside
AetiocetidaePBDB
Diet
carnivore, suspension feederPBDB, for Mysticeti
Life habit
aquaticPBDB, for Mysticeti
Motility
actively mobilePBDB, for Cetacea
Environment
marinePBDB, for Mysticeti

Time the record covers

At most 4.3 million years on record.

Every occurrence read is dated to somewhere between 27.3 Mya and 23.04 Mya, and nothing in the dating separates them, so that window is what the record shows rather than a span.

Oligocene — about 10 of 10 occurrencesOligoceneMiocene — about 0 of 10 occurrences27–27 Mya — about 0.1 occurrences27–27 Mya — about 0.4 occurrences27–27 Mya — about 0.4 occurrences27–27 Mya — about 0.4 occurrences27–27 Mya — about 0.4 occurrences27–26 Mya — about 0.4 occurrences26–26 Mya — about 0.4 occurrences26–26 Mya — about 0.4 occurrences26–26 Mya — about 0.4 occurrences26–26 Mya — about 0.4 occurrences26–26 Mya — about 0.4 occurrences26–25 Mya — about 0.4 occurrences25–25 Mya — about 0.4 occurrences25–25 Mya — about 0.4 occurrences25–25 Mya — about 0.4 occurrences25–25 Mya — about 0.4 occurrences25–24 Mya — about 0.4 occurrences24–24 Mya — about 0.4 occurrences24–24 Mya — about 0.4 occurrences24–24 Mya — about 0.4 occurrences24–24 Mya — about 0.4 occurrences24–24 Mya — about 0.4 occurrences24–23 Mya — about 0.4 occurrences23–23 Mya — about 0.4 occurrences23–23 Mya — about 0.4 occurrences23–23 Mya — about 0.1 occurrences27.8 Mya22.5 Mya

10 occurrences of Aetiocetus on record, most of them in the Oligocene. Bar height is expected occurrences, not a count: each fossil is spread across the span it is dated to, so a tall narrow bar means tight dating and a low wide one means loose.

When

10 occurrences

These are dates about fossils, not the animal: the record can only begin after it arose and end before it died out, so either end may reach further. Shares are expected occurrences: a fossil dated to a span is counted partly in each period it straddles. More on what this infers.

Found in

5 formations

El Cien — 24.38°N, 110.75°WEl Cien — 24.44°N, 110.70°WYaquina — 44.51°N, 124.08°WScotts Mills — 45.02°N, 122.60°WMorawan — 43.30°N, 143.77°EYamaga — 33.86°N, 130.89°E

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The named rock units Aetiocetus has been recovered from, largest first. Drawn where the rock is now, not where it formed. 1 occurrence has no formation on record, which is common for older literature.

Aetiocetus and its relatives

Oligocene

Where Aetiocetus and its relatives were recorded in the Oligocene.

Found in the same rock

30 taxa

The Paleobiology Database records 5 sites for Aetiocetus, and this reads all of them. The number is how many of those sites it was catalogued from too. The 24 sharing the most are listed.

This is not a list of everything alive at the time. It is only what has come out of the same ground as this animal and been written down.

Entered from

8 references

Each of the 10 occurrences read was entered from one of these publications, ordered by how many each accounts for. This is not a search for papers mentioning the name. Entries link to doi.org where the Paleobiology Database holds an identifier, and to its own record where it does not. Relayed as the Paleobiology Database holds them, not checked against what they resolve to.

Media and terms

Media content1

Picture of Aetiocetus

Credit
Owen Allen
Licence
CC BY 2.0
Commercial use
the licence allows it

No 3D scan of Aetiocetus was found in Sketchfab.

Smithsonian Open Access and MorphoSource were not reached for this taxon, so this list is what the others held rather than everything there is.

The description on this site

Licence
CC BY-SA 4.0

This is what the site found, which is not the same as what exists.

Keep going

What may have been alongside itAetiocetidae through timeFormations of the OligoceneThe world it lived on

Occurrence data from the Paleobiology Database, CC BY 4.0. Emlong 1966