Sunday, September 23, 2012

Are Crocodilians one thing?

A couple of months ago, I wrote a blog post about someone misrepresenting phylogenetic charts.
It is difficult to see, but the red line to the far left represents what used to be referred to as "Crocodilians".  The third red line from the top left represents "birds".  Now, I mainly took issue with the following statement.  
According to the chart, everything changed incredibly fast for 30 million years, then many didn’t change for the next 150 million years! Truth be told, it’s actually much worse than that. The fossil record actually contains things that are dated back to 400 million years and they are exactly the same as what we see today! Call me skeptical, but I find it hard to believe that an animal can stay exactly the same for long long of a time period...

...What these charts actually show is that one thing, stayed one thing and never changed into anything else! What we see in the world today and what we read in the Bible is consistent and true.

The fossil record confirms that one thing, stayed one thing, and never changed from, or into, anything else. Consider these quotes from non-creationists that support our conclusion.

In my original post, I pointed out that this is not what the chart says at all.  These red lines represent large amounts of diversity.
If you were to zoom in on that infraorder you would find that evolutionists think they changed for the next 150 million years producing new genera and species. For example, lions are a species. Their genus includes tigers, leopards, and jaguars. Their family includes other cats like pumas and house cats. Their sub-order, Feliformia, includes also hyenas, mongooses, meerkats, etc... Their order, Carnivora, includes bears, seals, dogs, etc... It is misleading to say that the order of Crocodilians did not change when an order or infraorder contains a lot of diversity. Just look at "W" which represents the suborder Ceratopsians. They were both bipedal and quadrupeds.

Well, I found a blog post by palaeozoologist Darren Naish explaining the taxonomy of what used to be called "Crocodilians".

Firstly – a minor point on nomenclature. This sort of thing has to be discussed whenever crocodilians are. The group of archosaurs conventionally called crocodilians, and frequently termed Crocodilia in the textbooks (that is, living crocodiles, alligators, gharials and all their crocodile-like, alligator-like and gharial-like fossil relatives) is now most typically termed Crocodyliformes. That is, ‘crocodilians’ of tradition are now crocodyliforms (note that the last ‘e’ gets dropped when you convert a ‘-formes’ name to its vernacular version). Within Crocodyliformes, the crown-group (that is, the group that contains the living species and all descendants of their most recent common ancestor) is termed Crocodylia. So, Crocodylia is a clade within Crocodyliformes (Clark in Benton & Clark 1988, Norell et al. 1994, Salisbury & Willis 1996, Brochu 2003).

Crocodyliformes is part of a more inclusive group that also includes the crocodyliform-like sphenosuchians, and this larger clade is termed Crocodylomorpha. In turn, Crocodylomorpha is part of a major archosaur group informally termed the crocodile-branch or crocodile-group archosaurs, the best technical name for which is (unfortunately) Pseudosuchia (how I hate the fact that this name might win out over Crurotarsi, if certain phylogenetic definitions are followed).

Massively simplified cladogram of crocodilians and their relatives, with numerous lineages not shown. The affinities between "rauisuchians", aetosaurs and crocodylomorphs are shown here as being unresolved, but some studies find aetosaurs to be closer to crocodylomorphs than are other croc-group archosaurs. Other studies find at least some "rauisuchians" to be closer to crocodylomorphs than are other croc-group archosaurs. Within Crocodylomorpha, some studies find thalattosuchians to be further away from Crocodylia than is Notosuchia.
In view of the confusion that ensues whenever an attempt is made to explain the use and meaning of these names (I’ve had to do it several times), I believe that we should stick with what we have: the archosaurs that we imagine as ‘crocodilians’ are now crocodyliforms, and the crocodyliform crown-clade is Crocodylia. However, some workers aren’t happy with this and have argued that we should use Crocodylia in place of Crocodyliformes (Martin & Benton 2008). I can’t see that this does anything useful bar complicate an already confusing situation and I think that we should ignore this proposal. When talking to technical audiences, I tend to use crocodyliform, but I don’t see anything wrong with ‘crocodilian’ being used as a vernacular term for the clades Crocodyliformes or Crocodylomorpha. [1]

In my last post, I made a comment about therizinosaurs.
They belong to “m” on your chart, the clades “Carnosaurs and Coelurosaurs”. Therizionosaurs, are in the clade, Coelurosaurs, and all posses sloth like giant claws. How can “m” which represents two parallel clades teach that “one thing stayed one thing”? Also, how is anything becoming a Therizinosaur not becoming a new thing?
I would like to echo that comment here.  The red line marked "Crocodilians" includes thalattosuchians.  How can anyone consider a group that includes these aquatic reptiles and alligators as "one thing stayed one thing"?   Clearly this chart does not teach that "everything changed incredibly fast for 30 million years, then many didn't change for the next 150 million years".  Thalattosuchians are thought to have evolved in the early Jurrasic.  

Whatever you believe about the Theory of Evolution, it is unwise to misrepresent information.  

No comments:

Post a Comment