Figure 1. Paleoparadoxia. Note the gap left by the diastema between the anterior and posterior teeth. With the phylogenetic placement of desmostylians at the base of the Mysticeti, can this gap be where baleen (light blue) originated? Good question.. The loss of teeth and the elaboration of the baleen in transitional desmostylian taxa takes us to the toothless, baleen endowed whales.
It’s only a guess…
but given the odd and large gap between the upper and lower jaws of Paleoparadoxia (Fig. 1), together with the loss of all teeth between the anterior and posterior ones, that gap might have been filled with the genesis of baleen in this sister to the Mysticeti whales. Note the canine (orange) is here aligned with the maxilla, essentially out of service. The anterior teeth make ideal scoops. The posterior teeth are flat grinders. The jaws are broader than tall, providing a wide space for a larger tongue. The naris is dorsally placed, enabling Paleoparadoxia to remain submerged.