Desmostylus and Caperea

Desmostylus hesperus (Marsh 1888; Oligocene) was the first desmostylian discovered and is known from several distinct species. One has a relatively larger skull and smaller limbs with a smaller hind limb and thus is transitional to right whales like Caperea (below) and Eubalaena. That specimen also has smaller anterior teeth and narrower jaw tips. Like all mysticetes, the mandible is wider than the rostrum (arrows). The original drawing misinterpreted the nasals and missed the premaxilla/frontal connection. A complete skeleton is shown below to scale with sister taxa.

Caperea marginata (pygmy right whale; extant; Bisconti 2012, Fordyce and Marx 2013) looks like a small blue whale, but has long, inclned ribs, only one lumbar vertbra, and a short tail. The mandible is deep and concave ventrally. Like Eubalaena the lacrimal is deeper than the maxilla. Note the tiny forelimb. The manus has a few extra bones that, when put back together, create a digit 1. Phalanges lost in basal therapsids reappear in this taxon with a netonous tiny manus.

Cope ED 1872. Descriptions of some new Vertebrata from the Bridger Group of the Eocene. Proceedings of the American Philosophical Society 12:460-465

Domning DP, Ray, CE and McKenna, MC 1986. Two new Oligocene desmostylians and a discussion of Tethytherian systematics. Smithsonian Contributions to Paleobiology. 59. pp. 1–56.

Fordyce RE and Marx FG 2013. The pygmy right whale Caperea marginata: the last of the cetotheres. Proceedings of the Royal Society B: Biological Sciences 280(1753):1–6.

Marsh OC 1888. Notice of a new fossil sirenian, from California. American Journal of Science 25(8):94–96.

Reinhart RH 1959. A review of the Sirenia and Desmostylia. University of California Publications in Geological Sciences 36(1):1–146.

Santos G, Parham J and Beatty B 2016. New data on the ontogeny and senescence of Desmostylus (Desmostylia, Mammalia). Journal of Vertebrate Paleontology. doi: 10.1080/02724634.2016.1078344

Tsai C-Hi and Fordyce RE 2015. Ancestor–descendant relationships in evolution: origin of the extant pygmy right whale, Caperea marginata. Biol Lett. 2015 Jan; 11(1): 20140875.

wiki/Caperea
wiki/Desmostylus

Mammalia

Ornithorhynchus and kin

Marsupials - Metatheria

Eomaia and kin

Placentalia 2

Tupaia and kin

Placentalia 1

Primates – Chiroptera

Notharctus and kin

Carnivora

Nandinia and kin