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Are Torosaurus and Triceratops one and the same?

The views expressed are those of the author and are not necessarily those of Scientific American.


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A rare horned dinosaur known as Torosaurus may not be a distinct species, after all, according to a presentation given Friday at the annual meeting of the Society of Vertebrate Paleontology in Bristol, England.

Researchers have long recognized similarities between Torosaurus and Triceratops, the main dtriceratops skeletonistinctions being that Torosaurus is larger and has an expanded frill at the rear of the skull. But John Scannella, a doctoral student at Montana University, and his advisor, John R. Horner, have found that specimens attributed to the two species actually form a developmental continuum rather than falling into discrete groups. A Triceratops skeleton on display at the American Museum of Natural History in New York City, for example, exhibits a number of skull traits reminiscent of Torosaurus, including thin parietal bones and elongated squamosal bones. In addition, microscope examinations of thin slices of bone from Triceratops and Torosaurus specimens reveal that individuals attributed to Torosaurus are more mature than any of the ones assigned to Triceratops. Scannella and Horner therefore believe that the fossils that have been categorized as Torosaurus are just Triceratops individuals that reached mature adulthood before they died.

Scientists have wondered how two such similar groups could have shared the landscape—both ranged from Colorado to Saskatchewan at the end of the Cretaceous period. If Scanella and Horner are right, the answer is simply that the animals are one and the same species.

But the finding raises the question of why fossil hunters have recovered so few of the mature “Torosaurus” specimens—fewer than a dozen, compared to the many dozens of younger Triceratops. “If Torosaurus is Triceratops, then we’re finding a lot of animals that had a lot of growing up to do,” Scannella comments. Insights may come once researchers determine a more precise age at death for the individuals.

The finding provides more evidence that dinosaur diversity was declining before the animals became extinct, which, Scannella says, supports the idea that something other than an asteroid impact extinguished them.

 

Photo of Triceratops skeleton at the American Museum of Natural History by mrkathika via Flickr





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  1. 1. galaxy_man 2:29 pm 09/28/2009

    Makes perfect sense to me. The mesozoic era isn’t exactly known for its peaceful times.

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  2. 2. krabcat 3:00 pm 09/28/2009

    How many 15 year old wolves do you see wandering around or,since triceratops was an herbivore, really old gazelle or other creatures reaching advanced age? when animals get older they can’t defend against attacks as well, despite the occasional report of an old lady beating up a mugger on the street. seems pretty strait forward to me

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  3. 3. Chuck Darwin 5:40 pm 09/28/2009

    Dr. Scannella vastly overstates the significance of this finding. Folding two species into one is hardly persuasive evidence of declining dinosaur diversity across the North American plains, much less worldwide. Frankly this calls into question his objectivity in reaching his conclusion. His findings should be evaluated with an extra measure of healthy skepticism.

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  4. 4. 诗人 10:40 pm 09/28/2009

    very good

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  5. 5. 诗人 10:42 pm 09/28/2009

    support

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  6. 6. Michiel Pillet 2:17 pm 09/30/2009

    "Dr. Scannella" is a doctoral student, Chuck. John just stated that this new study means that, relative to what was previously thought, there’s one less species. This means there are less species (without discussing any taphonomical bias), and thus the number of species is declining. Seems like a reasonable statement to me.

    Also, some of the greatest ideas in science come forth from speculation. John collected the evidence (you would be astonished if you knew how many data points he has), and formed a hypothesis to explain that evidence. To call his objectivity into question because of what he speculates in a media article seems a bit silly, wouldn’t you agree? Lamarckism has been disproved as well, but still Lamarck helped building the foundation for Darwin’s work. Scientists can make mistakes.

    It looks to me (and it’s perfectly normal!) that you’re having problems accepting the existence of a new and radical hypothesis, like creationists in Darwin’s time had problems grasping the concept of evolution.

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  7. 7. Chuck Darwin 8:48 pm 10/20/2009

    No, I’m having trouble accepting the claim that folding two species into one amounts to significant evidence for declining dinosaur diversity. My comment has nothing to do with whatever other data Scanella may have collected, it has to do with making grandiose claims for the significance of this single data point.

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  8. 8. Michiel Pillet 10:39 pm 10/20/2009

    It is significant

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  9. 9. Michiel Pillet 10:41 pm 10/20/2009

    Wrong button, sorry. I was saying, it is significant when you combine it with all the other recent research identifying genera as synonyms to others, for example Pachycephalosaurus and Dracorex. You can see a pattern emerging there.

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  10. 10. Dino Hunter 10:36 pm 10/29/2009

    They based thier research on AMNH 5116. As far as I know that specimen is a composite and is missing the frill altogether. That would make thier research moot. Also there is a 10 foot Triceratops skull at BYU and that one is Triceratops.

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  11. 11. notsogood 6:48 am 01/4/2010

    Dinosaurs are so unique and interesting and undiscovered and concealing, and I wonder how is it so they extincted…
    wouldn’t it be neat if they stayed?:)

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  12. 12. notsogood 6:51 am 01/4/2010

    You know I might not know a lot as a
    <a href="http://www.resumesplanet.com">resume writer</a>, but what really fascinates me is how veil this dinosaur world is and yet how intriguing:)

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  13. 13. Zontor 12:12 pm 08/1/2010

    I disagree Scannella over estimates the significance of his findings. The decline in diversity has been an ongoing debate to counter Alvarez’s claim that an asteroid impact was the sole cause of the end of the age of dinosaurs. The impact theory has always seemed implausible to me given its inability to explain why so many terrestrial species survived. I side with those who contend it was another nail but not the primary nail. I accept dinosaurs had run their course.

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  16. 16. Tommy_Lambert 5:49 am 09/16/2013

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