Two types of blow holes evolved in ‘cetaceans’

From the Roston and Roth 2021 abstract:
“Anatomical and functional differences between the two cetacean sub-orders, echolocating whales (odontocetes) and baleen whales (mysticetes), suggest that NP reorientation may be the result of convergent or parallel evolution rather than homology. Our findings add evidence suggesting that NP reorientation evolved twice within Cetacea and lay a foundation for future syntheses of data from fossils and other species.”

You heard it here first in 2016:
‘Whales’ are diphyletic with separate ancestries for odontocetes and mysticetes among terrestrial taxa (Figs. 1, 2). A more recent post about whales (with comments) can be found here.

Phys.org/news (link below) wrote:
The two major types of cetaceans appear to have evolved their characteristic blowholes through different anatomical transformations, according to a study being presented at the American Association for Anatomy annual meeting during the Experimental Biology (EB) 2021 meeting, held virtually April 27-30.

“The main difference we observed is in how the nostrils reach this position during prenatal development—there does not seem to be one way to do it,” said Rachel Roston, Ph.D., a postdoctoral fellow at the University of Washington and the study’s lead author. “The dolphin species and other toothed whales showed backwards bending of the skull, whereas the fin whale and other baleen whales showed changes in the occipital bone at the back of the skull.”

“Researchers have previously studied other differences in the nasal passages of the two types of cetaceans; for instance, toothed whales have a single nostril whereas baleen whales have two. By focusing on the part of the skull that connects the nasal passage and the rest of the body, the new study examines previously unexplored territory at the intersection of nasal passage orientation and head-body alignment.”

Simply add pertinent taxa to your favorite cladogram
that includes mysticetes and odontocetes and you will recover a diphyletic cetacea, too!

Figure 4. Subset of the LRT focusing on the odontocetes and their ancestors.
Figure 1. Subset of the LRT focusing on the odontocetes and their ancestors.
Figure 3. The oreodont-mesonychid-hippo-desmoystlian-mysticete clade subset of the LRT
Figure 2. The oreodont-mesonychid-hippo-desmoystlian-mysticete clade subset of the LRT

References
Roston RA and Roth VL 2019. Cetacean Skull Telescoping Brings Evolution of Cranial Sutures into Focus. The Anatomical Record. https://doi.org/10.1002/ar.24079
Roston R. and Roth VL 2021. (R4523) Bauplan of a Blowhole: Testing a Developmental Model for Nasal Passage Reorientation in Echolocating Whales (Odontoceti) and a Baleen Whale (Mysticeti). https://www.eventscribe.net/2021/EB2021/index.asp?posterTarget=375645
Roston RA and Roth VL 2020. Different developmental transformations underly blowhole orientation in a toothed whale (Odontoceti: Stenella attenuata) and a baleen whale (Mysticeti: Balaenoptera physalus). The FASEB JournalVolume 34, Issue S1 First published: 18 April 2020

Publicity
phys.org/news/2021-04-nose-evolve-blowhole.htm

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