More taxa for the ‘Paraceratherium=giant horse’ hypothesis

Figure 1. Adding a basal horse, Mesohippus, and a basal indricothere, Juxia, to the large reptile tree keeps indricotheres in the horse clade.

Figure 1. Adding a basal horse, Mesohippus, and a basal indricothere, Juxia, to the large reptile tree keeps indricotheres in the horse clade.

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).

Today
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.\

Figure 2. A selection of horse and indricothere skulls to scale. No other taxa are more closely related to these than each is to each other.

Figure 2. A selection of horse and indricothere skulls to scale. No other taxa are more closely related to these than each is to each other.

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.

Figure 3. In the LRT Mesohippus nests basal to horses and indricotheres.

Figure 3. In the LRT Mesohippus nests basal to horses and indricotheres (see figure 4).

Figure 1. Equus and Paraceratherium nest together on the LRT.

Figure 4. Equus and Paraceratherium nest together on the LRT.

References
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.

wiki/Paraceratherium
wiki/Juxia
wiki/Mesohippus

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6 thoughts on “More taxa for the ‘Paraceratherium=giant horse’ hypothesis

  1. Maybe, oh I don’t know, add some more fossil rhinos, tapirs, horses, extinct lineages like Chalicothers and basal Perissodactyla? You get weird results and never, ever do you question those results. That’s BAD science. You just take those results at face value and think that you the lone ranger of science have uncovered a vast conspiracy.

    • Alright, I see you actually do have Chalicothers represented. My comment still stands with regards to diversity of fossil taxa. Especially fossil rhino taxa. How can you rule out the possibility that horse are just more plesiomorphic than extent rhinos?

    • I always, always question my results. Evidently you do not know what goes on here in St. Louis even after all the evidence I present and all the changes I’ve made. I also question the results of other workers, which you don’t appear to appreciate. You know it’s okay to do that. It’s okay to confirm and refute results. You don’t want to me known as a guy who does not accept hard data. Questioning and testing is okay. If a paradigm is not true, one can establish a new paradigm. Acceptance sometimes takes a century. Just look at the history of Archaeopteryx.

  2. Chris, like a pilot flying at night or in a cloud, I trust my instruments. That’s good Science. If you trust your gut, tradition, what someone tells you… that’s bad Science, contra your opinion. And by the way, opinions are also bad Science. Good news is: Science is repeatable. Do your own analysis and let me know the results. And on the face of it, doesn’t the indricothere actually LOOK more like a horse than a rhino in nearly every aspect? That’s what the LRT also recovers, only it does so trait by trait.

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