Jump to content
Sign in to follow this  
Troodon

Did Triceratops horridus & T. prorsus just Evolve?

Recommended Posts

Troodon

Reading technical papers (pdf) is like going to the dentist you would rather not do it but you may get something out of it and I'll try one every once and a while. :blink:  

 

Here is an interesting one that discusses the two Triceratops described in the Hell Creek Formation Triceratops horridus and Triceratops prorsus.   The main authors of this paper are pretty well recognized Ceratopsian experts.  

 

The two species are basically identical and the only known differences are variations in cranial features like the length of the postorbital and nasal horns.   This paper suggest that the long held hypothesis that the differences are just sexual or ontogenetic variations is not valid and is primarily an evolutionary transformation.

 

In the attached figure they placed all known skulls stratigraphically across the entire Hell Creek Formation and found that T. horridus "features" were found only in the lower Hell Creek (L3) while the upper Hell Creek (U3)contained "features" of T. prorsus.   The middle Hell Creek (M3) was a transitional zone.  

 

Screenshot_20161018-051803.jpg

 

This transformation occurred in a relatively short period of time 1-2 million years and it's difficult to argue against sound evidence.   The paper again supports the need to have good information on where your specimen comes from.   To get a proper species identification it may not only be necessary to know the formation but specific locality. 

 

Paper 

pnas.201313334.pdf

 

FYI ...R. Boessenecker (aka Boesse)  was acknowledged in this paper

 

Next we need to settle the debate around Triceratops and Torosaurus 

.

 

Share this post


Link to post
Share on other sites
tmaier

Well, I'd like to be the first to declare the M3 form to be a new species, and give it the name Triceratops maierii.

:)

Share this post


Link to post
Share on other sites
ashcraft

I have always considered these to be differences caused by random genetic drift in species that have diverged from each other relatively close in time.  You see similar differences in moose species, white tailed and mule deer, and even between tigers and lions.  Different groups become isolated from each other, either by a physical barrier, or the niche they exploit, and random chance causes change in the genotypic frequency.  Throw in selection pressure and time, and you generate species that are now markedly different from each other, such as the different species of bears.

 

Brent Ashcraft

Share this post


Link to post
Share on other sites
Canadawest

We have a dozen species of chickadees migrating through our yard this time of year.  

4 hours ago, ashcraft said:

I have always considered these to be differences caused by random genetic drift in species that have diverged from each other relatively close in time.  You see similar differences in moose species, white tailed and mule deer, and even between tigers and lions.  Different groups become isolated from each other, either by a physical barrier, or the niche they exploit, and random chance causes change in the genotypic frequency.  Throw in selection pressure and time, and you generate species that are now markedly different from each other, such as the different species of bears.

 

Brent Ashcraft

 

True

 

The best way to study past ecosystems is to be familiar with the dynamics of the Nature around us. 

 

We have a dozen species of warblers migrating through our yard. They would all appear more or less anatomically identical even if a complete skeleton was studied...let alone a couple of isolated bones.  Variations within random individuals of the same species might be greater than between species.

 

What's important in science is definition of terms. In studying Upper Paleozoic corals there was an agreed upon criteria among researchers as  what constituted a new genus and a new species. It was morphological and never claimed to be biological. The issue with a lot of dinosaur taxonomy is that new genera and species of dinosaurs are published based on only one or a few  set of diverse criteria...  geologic age, teeth, size, geography, etc.  It became a mishmash.  Then to top it off researchers begin 'to care'.  We never really had any emotional stake in coral  'a' losing its species status and lumped in with another.  In contrast...dinos obtain some sacred  status and researchers can get agenda driven ( the antithesis of science) to 'prove' some point.  

 

 

Share this post


Link to post
Share on other sites
ashcraft

Its not just dinos...sharks are nuts.

 

I am a lumper myself.  If two organisms can interbreed, and produce viable off-spring, I argue that they are the same species.

 

Brent Ashcraft

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

Sign in to follow this  

  • Recently Browsing   0 members

    No registered users viewing this page.

×