“Wednesday” Wonders: Embolotherium

23 07 2009

Good tidings and well-wishes!

Within the realm of paleontology, there is often a disconnect between how well-known an animal or group is to the public and how scientifically or historically significant it is. For instance, one would be hard-pressed to find an individual who has never heard of the infamous Velociraptor, even some eight years since the release of the latest “Jurassic Park” film. Yet, while its relatives Sinornithosaurus and Deinonychus have yielded massive contributions to the field of avian evolution and the study of dinosaurian body temperature respectively, very few people aware of their existence could avoid being classified as ‘nerds’ in today’s society. While the discovery of Deinonychus in the 1960s helped give birth to the dinosaur renaissance, Velociraptor created little excitement after it was unearthed in the 1930s; all the latter had to do was star in a blockbuster action film to become a media sweetheart.

But as with nearly every situation, there are exceptions. The recent success of the “Ice Age” film saga and the highly-anticipated BBC docu-drama “Walking With Prehistoric Beasts” has given the weird and wonderful brontotheres a bit of recognition in the public eye (though I’m not for a moment suggesting that the average pedestrian would know what a Megacerops or Rhinotitan is, although this would have made for an amusing Jaywalking installment on “The Tonight Show”). For your viewing pleasure, I’ve added a link below which contains all of the Embolotherium scenes from a recent episode of the popular BBC sci-fi/drama “Primeval”:

This pseudo-celebrity status comes after nearly a century of fame surrounding these “thunder beasts” after Henry Fairfield Osborn utilized the brontotheriidae (along with the equidae) to illustrate the idea of orthogenesis. For an illustration of this and some excellent brontothere info, do go here.  

In Osborn’s 1929 paper entitled “Embolotherium, gen. nov., of the Ulan Gochu, Mongolia.” (available here), he briefly touches on the subject:

“The levels of all the Embolotherium and other “titanothere”[(brontothere)]remains have been carefully recorded and the vertical succession and evolution of the species will doubtless become evident and clear when the entire collection can be examined.” 

Before I proceed with my traditional discussion of the group containing the genera in question, I feel obligated to point out that an immense, 475-page revision of the Brontotheriidae has been composed by Matthew Mihlbachler and posted here. I must also confess that, due to the constraints of my current computer, I’m unable to download the blasted thing at this time. When I return to New Mexico in two weeks (I’m currently visiting my family in upstate New York), I’ll attempt to open the monstrous file and will update this post accordingly.

The Brontotheriidae are a family of perissodactyls known entirely from Eocene deposits of North America, Asia (especially the inner and outer Mongolia region), and parts of Eastern Europe (to a much lesser extent). In the abstract of Mihlbachler’s aforementioned paper, he writes:

“Characters shared by all brontotheriids include an anteroposteriorly (“from front to back”) abbreviated face and an elongate postorbital (“behind the eyes”) cranium. Dentally, brontotheriids share bunoselenodont upper molars with a W-shaped ectoloph, isolated lingual cusps, and with paraconules, metaconules, and transverse molar crests that are either vestigial or absent.”

However, the most eye-catching brontotheriid character is unquestionably their “nasal rams”. Traditional reconstructions, such as the one below, have depicted these appendages as thin, horn-like structures.

An out-dated Embolotherium reconstruction.

An Embolotherium reconstruction with an out-dated depiction of the creature's ram. However, the artist did manage to hit the metaphorical nail right on the head when drawing the beast's toes, as nearly all brontotheriids sport four on each forelimb and three on each hindlimb.

However, fellow paleo-blogger Zach Miller of “When Pigs Fly Returns” points out:

“Fun fact: all those restorations you see of many brontotheres (including Embolotherium) with a giant horn sticking out of the nose is wrong–the nasal “ram” has a deep channel on the anteroventral surface (“the bottom side of the front”) for the nasal septum. This means the nasal cavity extended to the peak of the ram. These were big-nosed animals!”

Zachs excellent reconstruction of an E. grangeri skull properly fleshed out.

Zach's excellent reconstruction of an E. grangeri skull properly fleshed out.

Because these ‘rams’ housed the nasal cavities of their owners, they were rather brittle and thus, may not have been utilized for the purposes of combat as many have assumed. However, a great deal of brontothere skeletons have sported fractured ribs and cranial injuries, which suggests that these beasts nevertheless fought rather frequently. Also, some species likely exhibited sexual dimorphism in the shape and size of their rams, meaning that males may have sized each other’s up before engaging in a confrontation over mates and territory. An alternate (but compatible) explaination maintains that the ram was utilized as a ‘resonating chamber’ with which to produce deep, long-range sounds, similar to what has been reconstructed in the famous hadrosaurid Parasaurolophus.

Embolotherium hails from Mongolia and is (rather predictably) the name-giving genus of the Embolotheriinae subfamily which, according to Mihlbachler’s 2004 paper, “A new brontothere (Brontotheriidae, Perissodactyla, Mammalia) from the Eocene of the Ily Basin of Kazakstan and a phylogeny of Asian ‘horned’ brontotheres.” (available here),

“include[s] Aktautitan, Metatitan, “Metatitan” progressus, Protembolotherium, and Embolotherium, with Brachydiastematherium as a provisional member. Titanodectes, a somewhat dubious taxon, represented by partial mandibles, may also belong to the Embolotheriinae.”

(Note that all members of the Brontotheriidae are also contained by the Brontotheriinae subfamily with the exception of Pakotitanops, Mulkrajanops, Eotitanops, and Palaeosyops. According to Mihlbachler’s 2008 abstract, the group “is supported by numerous molar apomorphies suggesting increased functional emphasis on shearing on the outer wall of enamel of the upper molars.”)

Osborn originally believed that the distinct ram of Embolotherium was “a novel structure, formed by an enlarged and uplifted nasal process, and was not homologous to the paired frontonasal horns of other brontotheres.” (Mihlbachler 26-27). Having found a fairly similar structure within the rams of all these previously-listed genera, Mihlbachler has phylogenetically united them. He also notes:

“the battering rams of two Embolotherium species are structurally contradictory;  one species seems to possess an enlarged and raised nasal process (E. grangeri), whereas a series of transitional forms [(Aktautitan, Metatitan, “Metatitan” progressus, and Protoembolotherium)] clearly indicates that the ram of Embolotherium andrewsi is actually homologous to the frontonasal horns of other brontotheres….That the ram of Embolotherium grangeri superficially resembles the nasal processes rather than the frontonasal horns of older brontotheres appears to have been a secondarily derived autapomorphic modification.”

From top to bottom: Embolotherium andrewsi, E. grangeri, and "E. louksii" (which is no longer considered to be a valid species).

From top to bottom: Embolotherium andrewsi, E. grangeri, and "E. louksii" (the latter of which is no longer considered to be a valid species).

The study of brontotheriids has a promising future, and hopefully our knowledge of these fascinating animals will expand with further research.

May the fossil record continue to enchant us all!

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9 responses

23 07 2009
Brian Beatty

I’m sorry I missed this earlier, I have been consumed with work recently and missed a bunch of blogs…
Matt Mihlbachler is a colleague of mine here at NYCOM, and is also my best friend. I am sure he’d be glad to send you a paper copy of his monograph if you think you’ll end up using it. AMNH publications come with 200 free copies for authors, and for a book that big, 200 copies takes up a lot of space in one’s office. So, even though he doesn’t want to hand them out carelessly, if you’re planning to do any work on perissodactyls, I bet he’d be happy to share.
Brian

24 07 2009
tanystropheus

Thanks for the heads-up, Brian! I do find perissodactyls rather interesting, especially considering the fact that they’re frequently upstaged by artiodactyls in paleo (which is understandable, given the greater diversity and cetacean linkage of the latter group). At this point however, all I know is that I want to work with mammals and therefore, I’m not entirely sure if I’m ever going to do any ‘work’ on perissodactyls in particular per se. Still, it certainly seems like a viable option at this point.

Between you, Dr. Solounias, and Dr. Mihlbachler, it seems like NYCOM really covers all (or at least most) of the bases when it comes to mammalian paleo!

24 07 2009
Zach Miller

Wonderful post, brother! I’m glad you found use for my illustration. I really dig brontotheres, personally, and Embolotherium in particular. Yay for ram-nosed rhinos! 🙂

24 07 2009
tanystropheus

Thanks for letting me use your picture, Zach! It’s the only one I’ve come across which contains a fleshed-out ram.

26 07 2009
Michael Ogden Erickson

These are sme pretty cool beasts, quite worthy of being Wednesday Wonders.

26 07 2009
tanystropheus

They certainly are quite cool, aren’t they?

13 08 2009
Wednesday Wonders: Erpetosuchus « The Theatrical Tanystropheus

[…] their beloved period has been unjustly neglected in recent months by my humble blog in favor of perissodactyls and eurypterids among other things. To remedy this situation, I’ve decided to post a bit of […]

21 03 2010
Weekly Spotlight: Tylocephalonyx « The Theatrical Tanystropheus

[…] its produced a menagerie of oddities throughout the course of the past 55 million years, including the deliciously-bizarre brontotheres and the largest land mammal known to have walked the surface of our planet. But perhaps the most […]

22 11 2010
Muhammad Farooqi

great. thanks-man.
regards

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