Eurygenium: another wombat close to Toxodon

This was a odd-looking cover taxon
in the Journal of Vertebrate Paleontology back in 1997 (Fig. 1).

Figure 1. Eurygenium is a smaller, less robust, longer legged version of Toxodon.

Figure 1. Eurygenium is a smaller, less robust, longer legged version of Toxodon. The original reconstruction appears to be trying to feed itself with its right hand, but this appears to be unlikely based on phylogenetic bracketing and that antebrachium does not appear to be able to pronate.

Eurygenium latirostris (Ameghino 1894. E. pacegnum Shokey 1997; late Oligocene, 25 mya; 76 cm in length) was described by Shockey as close to the origins of Toxodontidae. That is confirmed here in the large reptile tree (LRT (1028 taxa), but no prior authors nested these taxa with wombats and marsupials as they do here. Most authors considered both taxa notoungulates, a taxon that has been dispersed and essentially invalidated here in the LRT.

Figure 1. Toxodon was a notoungulate placental. Now it's a wombat marsupial.

Figure 2. Toxodon WAS a notoungulate placental. Now it’s a wombat marsupial. Now, just imagine tiny little toxodons or maybe just one tiny little toxodon in the marsupium of this beast. Wombats wear their pouches backwards, by the way. So if the baby wants to look outside the pouch, it sees a short thick tail wagging back and forth. Quite a sight, I’m sure, for baby and all outside observers.

Eurygenium is also close to Pyrotherium, and is from the same beds.

By the way…
Wombats wear their pouches backwards, so if the baby wants to look outside the pouch, it sees a short thick tail wagging back and forth. Quite a sight, I’m sure, for baby and all outside observers.

References
Shockey BJ 1997. Two new notoungulates (Family Notohippidae) from the Sall Beds of Bolivia (Deseadan: late Oligocene) : systematics and functional morphology. Journal of Vertebrate Paleontology 17(3):584-599.

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2 thoughts on “Eurygenium: another wombat close to Toxodon

  1. I haven’t checked but my guess would be that a backwards-facing pouch would be the primitive condition, as it facilitates entry as the tiny near-foetal offspring emerges from the reproductive tract. Forward-looking pouches would then be a later adaptation associated with upright posture. Does that make sense, agree with the record?

    • Good question! That made me go back to the soft tissue data. Didelphis is primitive with a ventral pouch like a bomb bay. Upright kangaroos open the pouch dorsally, like a bag. Digging wombats keep dirt out of the pouch by facing it backwards. Images can be found online by keywords: ‘wombat pouch’, ‘didelphis pouch’.

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