SVP abstracts 18: Palatal foramina and the origin of baleen in mysticetes

Peredo and Pyenson 2020 discuss
the origin of baleen in mysticetes by looking at palatal foramina.

“Baleen whales (mysticetes) filter-feed using specialized keratinous plates, called baleen, to sieve large quantities of prey laden water. Baleen represents a wholly novel integumentary structure, with no apparent homologous structure in any living animal. The origins of baleen, and filter-feeding in whales, have been the topic of much debate. In particular, the lack of osteological correlates for baleen makes it unclear which (if any) stem mysticetes first had keratinous structures for filter feeding.”

The origin of baleen in whales is found in traditionally overlooked nearly toothless desmostylians like Desmostylus (Fig. 2) and Behemotops (Fig. 3), taxa nesting basal to mysticetes in the large reptile tree (LRT, 1751+ taxa; subset Fig. 1).

Figure 3. The oreodont-mesonychid-hippo-desmoystlian-mysticete clade subset of the LRT

Figure 1. The oreodont-mesonychid-hippo-desmoystlian-mysticete clade subset of the LRT

“One potential osteological correlate are palatal foramina and sulci: structures in the roof of the mouth that may vascularize the baleen plates.”

Peredo and Pyenson are “Pulling a Larry Martin” by looking for a few ‘key’ traits rather than running a phylogenetic analysis of all traits without excluding pertinent taxa, such as Desmostylus and Behemotops.

“Palatal foramina are present and well developed in extant and fossil crown mysticetes and are preserved in some stem mysticetes as well. Here, we report the presence of numerous and well-developed palatal foramina in non-filter-feeding cetaceans, including crown and stem odontocetes and in stem cetaceans (so-called archaeocetes).”

Peredo and Pyenson are excluding pertinent taxa.

“Additionally, we observe the presence of palatal foramina in 61 observed species of terrestrial artiodactyls.”

Peredo and Pyenson are excluding pertinent taxa. No artiodactyls are basal to any whales in the LRT. Hippos are not artiodactyls in the LRT. Toothed whales arise from tenrecs and anagalids.

Figure 1. Taxa in the lineage of right whales include Desmostylus, Caperea and Eubalaena. The tiny bit of jugal posterior to the orbit (in cyan) is found in all baleen whales tested so far. The frontals over the eyes are just roofing the eyeballs in Desmostylus, much wider in Caperea and much, much longer in Eubalaena.

Figure 2. Taxa in the lineage of right whales include Desmostylus, Caperea and Eubalaena. The tiny bit of jugal posterior to the orbit (in cyan) is found in all baleen whales tested so far. The frontals over the eyes are just roofing the eyeballs in Desmostylus, much wider in Caperea and much, much longer in Eubalaena.

The Peredo and Pyenson abstract continues:
“CT scanning demonstrates consistent internal morphology across all observed palatal foramina, suggesting that the palatal foramina observed in extant mysticetes are homologous to those of terrestrial artiodactyls.”

This sounds like cherry-picking taxa. Perhaps palatal foramina are typical of non-arboreal mammals? What do tenrec and desmostylian foramina look like?

Figure 1. Rorqual evolution from desmostylians, Neoparadoxia, the RBCM specimen of Behemotops, Miocaperea, Eschrichtius and Cetotherium, not to scale.

Figure 3. Rorqual evolution from desmostylians, Neoparadoxia, the RBCM specimen of Behemotops, Miocaperea, Eschrichtius and Cetotherium, not to scale.

The Peredo and Pyenson abstract continues:
“The presence of palatal foramina in non-filter-feeding whales (odontocetes and archaeocetes) and in terrestrial artiodactyls suggest that the structures are more probably associated with an elaborate gingiva or other oral tissue and are alone not reliable osteological correlates for the presence of baleen in fossils.”

Next time, just add pertinent taxa and run the analysis… then see what turns up. The origin of baleen in whales was answered here in 2016. ResearchGate.net has an unpublished paper to read on the triple origin of whales here.


References
Peredo CM and Pyenson N 2020. Palatal foramina in stem whales and terrestrial artiodactyls obfuscate their potential for inferring baleen in stem mysticetes. SVP abstracts 2020.

wiki/Baleen_whale

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.