When you create a heresy
by breaking with decades of tradition, it’s always a good idea to test your hypothesis of interrelationships by adding pertinent taxa.
A few days ago Paraceratherium, a derived and gigantic indricothere, was nested in the large reptile tree (LRT, Fig. 1) with Equus, the extant horse. Tradition dictated that it should have nested with Ceratotherium, the extant white rhino – IF Paraceratherium was indeed a giant hornless rhino. But it wasn’t then and it isn’t now, based on current data. (One must always be willing to accept better data that busts up your favorite discoveries).
Juxia (Chow and Chiu, 1964), a horse-sized indricothere with more premaxillary teeth and Mesohippus (Marsh 1875) a primitive three-toed horse, are added to the LRT (subset Fig. 1) to test the prior nesting. Mesohippus is known from a dozen species. Juxia is known form a nearly complete skeleton and a less-complete referred specimen. It is one of the smaller and more primitive indricotheres.\
Everyone knows indricotheres are supposed to be
giant hornless rhinos. But in the LRT they continue to nest with horses. The Bootstrap numbers (Fig. 1) are strongly supportive. And its pretty obvious when you get them together (Fig. 2). Both Juxia and Paraceratherium (Figs. 1, 4) look like giant three-toed horses, because that’s what they are. Not sure why this was never noticed before. Let me know if you know of any prior literature on this hypothesis of relationships.
Chow M and Chiu C-S 1964. An Eocene giant rhinoceros. Vertebrata Palasiatica, 1964 (8): 264–268.
Marsh OC 1875. Notice of new Tertiary mammals, IV. American Journal of Science 9(51):239-250.