Neoparadoxia swimming animation

The origin of the Mysticeti
Earlier we nested baleen whales with desmostylians like Neoparadoxia (Fig. 1; Barnes 2013). 

Figure 1. GIF animation of the Neoparadoxia (original image from Barnes 2013). It seems illogical that the tiny tail of a desmostylian like this would ever become the giant tail of a mysticete, while the giant hind limbs disappear into the torso, but phylogenetic analysis recovers just such a scenario. Many long-jawed desmostylians are known from cranial material only and these are likely to be those that had large tails and smaller hind limbs.

Figure 1. GIF animation of the Neoparadoxia (original image from Barnes 2013). It seems unlikely that the tiny tail of a desmostylian like this would ever become the giant tail of a mysticete, while the giant hind limbs disappear into the torso, but phylogenetic analysis recovers just such a scenario. Many long-jawed desmostylians are known from cranial material only and these are likely to be those that had large tails and smaller hind limbs.

Recovered by phylogenetic analysis
The large reptile tree (LRT 1040 taxa) nests desmostylians as proximal outgroups to the mysticetes. Mysticeti, like the gray whale Eschrichtius robustus (Fig. 2)have a large robust tail and no visible hind limbs. That’s just the opposite of what you find in what little we know of known desmostylians (Fig. 1). Noteworthy: we don’t know the tail length in several of the long-jawed desmostylians, the ones most like mysticetes. This is when you have to put away traditional biases and let the cladogram truly be your guide.

Figure 6. Eschrichtius-robustus, the gray whale is the most basal mysticete tested in the LRT with a skull similar to Desmotylus and Beheomotops.

Figure 2. Eschrichtius-robustus, the gray whale is the most basal mysticete tested in the LRT with a skull similar to Desmotylus and Beheomotops. The sacrals here are orange and the robust tail follows to the right. 

In similar fashion
pterosaur workers have been looking in vain for a long manus reptile as the proximal ancestor to the Pterosauria, overlooking taxa with small forelimbs like Cosesaurus, Sharovipteryx and LongisquamaAll this time, they did not realize the elongation of the forelimb elements to various degrees was the LAST transformation that occurred in the known outgroups to the Pterosauria (Peters 2002). You, too, will make discoveries like this when you put away traditional biases, expand your taxon list and let the cladogram be your guide.

As you might remember
the origin of the Odontoceti (toothed whales) started with swimming tenrecs like Leptictidium (Fig. 3) and its close relative Pakicetus, both with a very long tail and large feet.

Figure 1. Leptictidium is known as a hopper. Here it nests with whales. Combine the two and when Lepticitidium jumps in the water, it continues hopping. That long, long tail is homologous to the long, long tail in Zeuglodon.

Figure 1. Leptictidium is known as a hopper. Here it nests with whales. Combine the two and when Lepticitidium jumps in the water, it continues hopping. That long, long tail is homologous to the long, long tail in Zeuglodon.

References
Barnes LG 2013. A new genus and species of Late Miocene Paleoparadoxiid (Mammalia, Desmostylia) from California. Contributions in Science 521:51-114.
Peters D 2002. A New Model for the Evolution of the Pterosaur Wing – with a twist. – Historical Biology 15: 277–301.

Advertisements

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 )

Twitter picture

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

Facebook photo

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

Google+ photo

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

Connecting to %s