Short one today.
You might remember over a year ago a presentation on the evolution of mammal molars from simple to complex and back to simple again in toothed whales (Odontoceti, Fig. 1).
On the same note,
here’s a presentation of three skulls, Pachygenelus (pre-mammal cynodont), Megazostrodon (last common ancestor of all mammals in the large reptile tree (LRT, 1698+ taxa), and Maiacetus, a toothed pre-whale with limbs (Fig. 2).
Just concentrate on the teeth today,
and note how the simple cones (Fig. 3) of basal therapsids, then the canine led simple triangles of basal cynodonts (Fig. 2) then multicusped teeth of basal mammals (Fig. 2), slowly reversed over time to become, once again, triangles, then simple cones in odontocete whales (Fig. 4).
As long-time readers know, baleen whales had their own evolution
as mysticetes arose from mesonychids, hippos, anthracobunids and desmostylians in turn, according to results recovered from the large reptile tree, which minimizes taxon exclusion by testing a wide gamut of nearly 1700 taxa.
Still waiting for a competing analysis
that tests a similar gamut of taxa. Emails to whale experts have not earned replies.