Llanocetus: not a ‘baleen whale with teeth and gums’

Hailed in the popular press
(see below) as a ‘baleen whale with teeth and gums’, Llanocetus denticrenatus (Mitchell 1989; Fordyce and Marx 2018; 8m in estimated length; 34 mya), nests in the large reptile tree (LRT, 1320 taxa) with archaeocete (toothed) whales, not with mysticetes (baleen whales).

Fordyce and Marx described Llanocetus
from a virtually complete skull (Fig. 1) as “the second oldest mysticete known.” Their phylogenetic analysis nested Llanocetus with Mystacodon, which they describe as “the oldest mysticete,” but earlier the LRT nested it with archaeocete toothed whales, too.

Figure 1. Llanocetus, hailed as a baleen whale with teeth and gums, is just a large archaeocete.

Figure 1. Llanocetus, hailed as a baleen whale with teeth and gums, is just a large archaeocete.

According to Fordyce and Marx, “The broad rostrum has widely spaced teeth marked with dental abrasion and attrition, suggesting biting and occlusal shearing.” Such traits are unexpected in a filter-feeder.

Figure 1. (above) Zygorhiza kochi from George Mason University website, likely captured from Kellogg 1936.

Figure 2. (above) Zygorhiza kochi from George Mason University website, likely captured from Kellogg 1936. To make the jaws fit and teeth occlude the mandible had to be reduced and the cranium had to tilted down posteriorly.

Fordyce and Marx attempt to force-fit their new taxon into the Mysticeti
when they report, “As in extant mysticetes, the palate bears many sulci, commonly interpreted as osteological correlates of baleen. Unexpectedly, these sulci converge on the upper alveoli, suggesting a peri-dental blood supply to well-developed gums, rather than to inter-alveolar racks of baleen. We interpret Llanocetus as a raptorial or suction feeder, revealing that whales evolved gigantism well before the emergence of filter feeding.”

No mention of desmostylians here…

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. It is worthwhile noting the similarities shown between Cetotherium and Ilanocetus. Such convergences are the source of Fordyce and Marx’s hypotheses.

Fordyce and Marx conclude in their abstract,
“This scenario differs strikingly from that proposed for odontocetes, whose defining adaptation-echolocation-was present even in their earliest representatives.” 

Unfortunately,
the authorse have no idea that those ‘earliest representatives’ of odontocetes are represented today by tenrecs that also echo-locate and travel in pods, as we learned earlier here.

Once again,
taxon exclusion is to blame for the earlier mistakes. Fordyce and Marx refuse to test desmostylians in their analyses, similar to pterosaur workers who refuse to test tritosaur lepidosaurs, and turtle workers who refuse to test small horned pareiasaurs. That’s why the wide gamut taxon list of the LRT comes in so handy. You don’t have to guess or force-fit any taxa… just let the software and the taxon list do your work for you.

No wonder whale workers are not letting
my papers on whale, turtle and pterosaur origins be published. 

References
Fordyce RE and Marx FG 2018. Gigantism precedes filter feeding in baleen whale evolution. Current Biology 28(10):1670–1676.

wiki/Llanocetus

https://www.techtimes.com/articles/227549/20180512/34-million-year-old-skull-from-antarctica-reveals-baleen-whales-had-teeth-and-gums.htm

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