While academic whale workers continue to seek without success
toothless mysticete ancestors in the Archaeoceti (e.g. Bisconti M 2012 and links below) the LRT recovered a Miocene (11-7mya) mysticete, Miocaperea pulchra, with fossil baleen AND vestigial, but desmostylian-like, molars (Figs 1, 2). Bisconti 2012 overlooked the teeth and called Miocaperea, “A fossil pygmy right whale with exquisitely preserved baleen.”
Baleen is made of keratin, like hair and fingernails, so preservation is rare.
Figure 1. Miocaperea is a Miocene mysticete with vestigial molars. Its a giant desmostylian. Compare to Desmostylus to scale at lower right.
Miocaperea pulchra
(Bisconti 2012; late Miocene, 7–8 Ma; 40cm skull length) was considered a Miocene ancestor of Caperea (Figs 3, 4). The post-crania in Miocapera is not known, so it could have had legs or flippers, or some sort of transitional structure.
Figure 2. Miocaperea baleen from the Miocene.
Bisconti did not mention teeth
or desmostylians in his text. Instead he listed the toothed whales, Aetiocetius, Zygorhiza, Dorudon, Georgiacetus and Protocetus as outgroup taxa along with Mammalodon, a taxon nesting between hippos and desmostylians in the LRT.
So taxon exclusion was an issue and a handicap for Bisconti back in 2012. The traditional clade Cetacea was invalidated here in 2016, so Bisconti was following tradition.
Here is a report on the fossil chin of an Australian mysticete
“at least 10 million years older”, (19mya, Early Miocene, Rule et al 2023) shown on the video below.
You might find an online NatGeo article titled,
“Prehistoric toothless whale among oldest” at 36 million years ago. This was about Mystacodon, a toothed odontocete ancestor, perhaps with legs. This claim was debunked earlier, links below.
You also might find an online SDSU article titled,
“Ancient baleen whales had a mouthful. Ancient CD scanes of a 25 million year-old fossil skull show the Aetiocetus weltoni had both teeth and baleen, unlike modern whales.” What they found is ‘neurovascular evidence’ in a toothed whale for which they report, “Fossils reveal that the earliest mysticetes possessed an adult dentition.”
This, again, is incorrect and an ongoing myth based on taxon exclusion.
Peredo, Pyenson and Uhen 2022 also debunked this hypothesis,
and they reported, “the oldest direct evidence of fossil baleen is ~ 27 million years younger than the oldest stem mysticetes” citing Esperante et al 2008. Note: they said ‘oldest’ and ‘younger’, which is a confusing way to state an earliest age for baleen.
Strangely, the authors did not cite Bisconti 2012 (Fig 2) from ten years earlier.
Oversight? Or feud?
Esperante et al 2008 reported,
“This paper documents the exceptional occurrence of thirty seven fossil whale specimens with preserved baleen in the Neogene Pisco Formation during a transect survey in a limited area west of the Ica River Valley near the town of Ocucaje in southern Peru.”
The Pisco Formation runs 15 to 2 mya.
No more specific age estimates were given. Compare to the age estimate for late Miocene Australian Miocaperea at 11-7 mya. Sperm whales were later reported in the Pisco Formation by Benites-Palomino et al 2022, so this was a popular spot for a wide variety.
Figure 3. From Esperante et al 2008, one of 37 whale specimens in Peru with detached baleen structures.
Esperante et al 2008 also wrote,
“Taxonomic identification was not emphasized, although three specimens are cetotheriid-like, and most other whales are balaenopterid-like. The baleen strips were found detached (Fig 3). Esperante et al explained, “This attachment breaks down quickly after death of the individual. This would explain why very few specimens of whale fossils in general have been found with baleen preserved.”
Figure 4. Extant Caperea skull. Here the molars are missing, leaving only alveoli (tooth hole) remnants. See figure 5 for a closeup.
Figure 5. Closeup of the palate of Caperea. Arrows indicate toothless alveoli.
It’s great that so many workers seek
to find the origin of baleen in the mysticete lineage. Add taxa to find this out for yourself. Don’t omit pertinent taxa just because your professor said it would be okay.
Refeences
Benites-Palomino A et al 2022. Sperm whales (Physeteroidea) from the Pisco Formation, Peru, and their trophic role as fat sources for Late Miocene sharks. Proceedings of the Royal Society B online
Bisconti M 2012. Comparative osteology and phylogenetic relationships of Miocaperea pulchra, the first fossil pygmy right whale genus and species (Cetacea, Mysticeti, Neobalaenidae). Zoological Journal of the Linnean Society 166(4) 876—911.
Bisconti M and Carnevale G 2022. Skeletal transformations and the origin of baleen whales (Mammalia, Cetacea, Mysticeti): A study on evolutionary patterns. In: Evolution of Crown Cetacea. A special issue of Diversity ISSN 1424-2818.
Esperante R, Brand L, Nick KE, Poma O and Urbina M 2008. Exceptional occurrence of fossil baleen in shallow marine sediments of the Neogene Pisco Formation, Southern Peru. Palaeogeogr. Palaeoclimatol. Palaeoecol. 257, 344–360. https://doi.org/10.1016/j.palaeo.2007.11.001
Peredo CM, Pyenson ND and Uhen MD 2022. Lateral palatal foramina do not indicate baleen in fossil whales. Nature Scientific Reports 12:11448
Peters D unpublished 2018. The triple origin of whales. ResearchGate.net pdf
Rule JP et al (5 co-authors) 2023. Giant baleen whales emerged from a cold southern cradle. Proceedings of the Royal Society B 290: 20232177 https://doi.org/10.1098/rspb.2023.2177
wiki/Miocaperea
nature.com/articles/nature.2017.21966
https://museumsvictoria.com.au/article/rewriting-whale-evolution/
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