A new paper by Peredo et al. 2018
describes a new early Oligocene mysticete: “Maiabalaena had neither teeth nor baleen—it represents a surprising intermediate stage between modern filter-feeding whales and their toothed ancestors.”
The new taxon is:
Maiabalaena nesbittae (Peredo, Pyenson, Marshall and Uhen 2018; USNM 314627).
Peredo et al. remind us:
“The functional transition from teeth to baleen in mysticetes has remained enigmatic because baleen decays rapidly and leaves osteological correlates with unclear homology.”
Actually that’s not the problem.
Peredo et al. and other whale workers continue to follow the invalid hypothesis of a monophyletic Cetacea. They believe in false precept of a ‘toothed mysticete’. They refuse to include desmostylians, hippos, mesonychids, tenrecs, and other pertinent taxa in their phylogenetic analyses. Adding these taxa recovers two origins for living whales from distinct quadrupedal semi-aquatic taxa in the large reptile tree (LRT, 1354 taxa). Desmostylians already lack most of their teeth (Fig. 4) and that explains tooth loss in mysticetes.
Peredo et al. report, “The oldest direct evidence for fossil baleen is 25 million years younger than the oldest stem mysticetes (36 Ma). Previous hypotheses for the origin of baleen are inconsistent with the morphology and phylogenetic position of Maiabalaena. The absence of both teeth and baleen in Maiabalaena is consistent with recent evidence that the evolutionary loss of teeth and origin of baleen are decoupled evolutionary transformations, each with a separate morphological and genetic basis. Understanding these macroevolutionary patterns in baleen whales is akin to other macroevolutionary transformations in tetrapods such as scales to feathers in birds.”
Except that scales don’t evolve into feathers in birds.
And these authors will never understand the macroevolutionary patterns in baleen whales without adding pertinent taxa (listed above) that are currently routinely omitted.
With more LRT taxa, the other explanation for baleen loss is:
baleen was lost in derived mysticetes like Maiabalaena… that is, if Maiabalaena actually lacked baleen, which I doubt without much evidence other than the enormous gape in the mouth of Maiabalaena (Fig.1).
In the LRT
Maiabalaena is closely related to Yamatocetus (Fig. 2), both unrelated to toothed whales. Taxon exclusion renders the Peredo et al. study basically useless.
Presented once again,
here (Fig. 4) are a few mysticete ancestors. Cetotheres, with their giant flat heads, are derived myisticetes, not basal forms.
PhD candidate Carlos Peredo appeared on NPR’s Science Friday podcast
here. I commented Feb. 2, 2019 below that YouTube video, repeated below:
“Maiabalaena, is a highly derived flat-headed baleen whale that has lost its baleen according to a phylogenetic analysis that includes more taxa. The actual ancestors of baleen whales were desmostylians, hippos, mesonychids and oreodonts, not related to Pakicetus. Toothed whales evolved separately from Pakicetus, which was a large aquatic tenrec, which are small mammals alive today on the island of Madagascar. Tenrecs hunt in packs (pods) and some use echolocation helped by their asymmetric skulls.”
Peredo et al., 2018. Tooth Loss Precedes the Origin of Baleen in Whales. Current Biology (2018), https://doi.org/10.1016/j.cub.2018.10.047