Overlooked convergence: sharks and whales have a gelatinous snout

Short one today.
The pictures tell the story.

Everyone knows
the snout of the sperm whale is shaped by large sacs of spongy gelatinous material, the spermaceti organ and the melon (Fig. 1).

Figure 1. Sperm whale head diagram showing  the spermaceti organ and the junk (melon) sitting atop the elongate rostrum, as in sharks, more or less.  See figure 2.

Figure 1. Sperm whale head diagram showing the spermaceti organ and the junk (melon) sitting atop the elongate rostrum, as in sharks, more or less. See figure 2.

Shark skulls are not shaped like hydrodynamic bullets.
like the skulls of sturgeons, paddlefish and bony fish. Rather, shark skulls (Fig. 2), like sperm whale skulls, have gelatins that fill the voids and support their bullet-shaped snouts.  Since I didn’t see anything like this when I ‘googled’ it, I thought to add it to mix.

Figure 2. Skull of the dogfish shark, Squalus, superimposed on a graphic of the invivo shark. Yellow areas added to show the extent of the gelatinous material that fills the empty spaces above and below the cartilaginous rostrum (nasal homolog).

Figure 2. Skull of the dogfish shark, Squalus, superimposed on a graphic of the invivo shark. Yellow areas added to show the extent of the gelatinous material that fills the empty spaces above and below the cartilaginous rostrum (nasal homolog).

Yesterday’s post on shark skull cartilage
and the bony homologs one can clearly see by coloring the elements (the now common DGS method) invited a reader’s comments that what I’m doing ‘is the death of science.’ As longtime readers know, I follow the evidence and point out flaws in traditional hypotheses, including instances of taxon omission. That this is necessary points not to the death of science, but to the willingness of someone to test untested hypotheses and taxon lists.

I welcome evidence to the contrary.
I make changes constantly. I follow the evidence, not the textbooks and not the professors, unless the evidence supports them.

Thank you
for your interest in this ongoing online experiment of a life-long learner and heretic.

 

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