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Re: Terrestriality is a bias



... and so is Arboreality.

What needs to be done is to stop Pigeon hole nature into arboreality,
but nature will prove us wrong.
There has been a recent study on island endemic lizards (I didn?
t copy the article but I know the series that it was in. I wish I had copied
it.) showed that terrestrial and arboreal lizards of the same genus (?, or
was it species?) did not show any skeletal differences. If it was found in a
quarry it would have been interpreted as being terrestrial. Komodo monitors
will climb trees until it reaches a length of 6 feet. They also show
arboreality in their skeletons. Bears climb, a certain goat can climb trees,
dogs, squirrels, etc, but their skeletons don?t show this. What about the
pelycosaurs _Varanosaurus_ and _Aerosaurus_? They are about the size of a
small Komodo monitor, could they climb trees?

These are anecdotes. They do nothing to show that certain theropods were/were not arboreal. All this suggests is that certain rare behaviors in bears, goats, etc., are not necessarily predictable from a quick and cursory observation of their skeletons alone. But would you argue that bears are arboreal because they can, in certain exceptional instances, climb into trees?

Could pelycosaurs climb trees? Well, maybe, but how often would they be there and for what advantage? Furthermore, even though Komodo dragons may climb up trees and other foliage, would you argue they were arboreal? What does the joint and limb structure of a Komodo dragon look like, and how does that skeleton allow occasional arboreality? Have these characteristics been noted in pelycosaurs? Are the enivornments the pelycosaurs lived in and the Komodo dragon lives in similar? Since pelycosaurs are synapsids, is it fair to compare them with a large diapsid lepidosaur? Just because some pelycosaurs are the size of a small Komodo dragon or varanid lizard does little to show possible tree-climbing behavior.

With theropods there is a terrestrial bias, and placing a
theropod in a tree gets laughed at. I?ll admit that I was one who laughed at
the idea.

This again has little to do with whether an animal could be shown, through empirical evidence, to be arboreal.

Greg Paul had put on _Ornitholestes_ in a tree and I thought yea
right. But maybe he?s right. I?ll have to look at it more closely. What
about dromaeosaurids? Could they have climbed trees? This is something I?m
working on and a few others.


Would like to see the work -- could be interesting.

Will that be accepted? Probably not. A
_Deinonychus_ is bigger than a Komodo monitor but would have been lighter.

How are you determining the mass of a living Deinonychus? Even if it was lighter, how does that show us that it was regularly an arboreal animal, spending much of its time in the trees?

Why must theropods be put through a more rigorous testing than other
animals?  Terrestrial bias is why.

Forget about bias. Rather, examine your own bias toward arboreal theropods. What is compelling you to decide they are arboreal? If the majority of paleontologists are being led blindly toward terrestrial theropods, then, dammit, show us what you have. Do you have something interesting we should know about the joint structure? Have there been studies examining theropod remains and their taphonomy and sedimentology that suggests they are dying in forested areas? If you are not correct, what evidence would suggest this? If the majority hypothesis on terrestrial theropods is incorrect, how would you go about empirically showing it? Are you presenting something at SVP or elsewhere where we may be able to see you present this info? I seriously want to know and understand how a theropod could be arboreal and how the problem could be approached. Show us what you got.

            There are some animals that arboreality is not questioned.
_Kuehneosaurus, Icarosaurus, Coelurosauravus_ with there long ribs are
believed to have been gliders so it had to climb trees to have something to
glide from. No big tests needed.

But here's where you could start! Are folks just blindly excepting arboreality in this case? Why? Could the ribs be used for something else? Man, the questions here are interesting and endless!

There is a preconceived notion on what an early bird would look
like. 

What is that notion?

But when one is found in the Late Triassic it is considered to be a
composite because it doesn?t fit that preconceived notion.

Or, the people who have looked at it disagree with Chatterjee because it is not clear what he has. Chatterjee is making a very thought-provoking and fascinating conclusion about bird evolution. Therefore, we need very good, clear evidence of this is many paleontologists are to be convinced that Chatterjee's hypothesis holds water.

I?ve talked to
Sanker and the person who excavated _Protavis_. I believe them that it is
just one genus in the block. I bet even if a totally intact, articulated
specimen, it will still be thought of as a composite animal.

Now this is no fair and not true, Tracy. Many people would interested in seeing a totally intact Protoavis animal because of what it would mean.

The opposite is true for _Rahonavis_. It is a long tailed bird
that is older than Archaeopteryx. Some believe that this is a composite
animal. With the bird_Vorona_ and a theropod. There are three reasons why
this is wrong. 1). The _Vorona_ is two big for _Rahonavis_ arms. 2). There
is a sauropod skeleton in between the two and most importantly _Vorona_ is
from a lower bedding plain. There were long tailed birds in the Mesozoic,
but since they do not fit the idea of a bird, then it is considered to be a
composite. Just because the animal doesn?t fit a preconceived notion doesn?t
mean it is a composite. Trees are a niche that was filled and it should be
considered.

Trees are niche and that niche was probably filled, but was it filled with theropods? Again, back to the empirical evidence I'm afraid.

            What about burrowing animals? We know _Thrinaxodon_ and
_Cistecephalus_ were burrowers because they were found in burrows. Bakker
says Drinker was found in a burrow, but does anyone believe him? Not many,
because he?s Bakker.

I just think his evidence for dinosaurs in burrows may be a bit sketchy. It's a clever idea, but what functional evidence do we have from Drinker that it is burrowing? Does Drinker live in burrows made by other animals? Could a large tortoise or other animal make burrows that other dinosaurs used? Could this Drinker have fallen into a burrow in death? Could it have been carried there by other dinosaurs eating it? Could it be a sink hole and not a burrow? etc. Don't confuse human politics with genuine scientific doubt about these ideas. Yes, some folks will dismiss Bakker outright, but the problem is not with Bakker himself but rather with the implications of what he or others may propose. These things need to be better thought out and researched. Maybe some dinosaurs did live in burrows. What we need is a way to go about testing that hypothesis.

There are some things that Bakker says that I disagree
with, but this I think he may be right. Also _Protoceratops_ is now
considered by a few to have been a burrower. Just because Bakker says it
doesn?t mean that we should just dismiss it.

Okay, but WHY do people feel Protoceratops may have been a burrower. It's a start -- it's an hypothesis. Where do we go from there to test it? Does Protoceratops have large elbows to attach huge triceps mucles to help it dig? Could it's head shield push aside sand well? Could an animal like Protoceratops dig a solid burrow in sand? Again, WHY not WHO said it.

             So there were niches during the Mesozoic that was filled, in
trees and in the ground, that needs to be thought about and not forgotten.
Just because an animal doesn?t fit a preconceived notion, it doesn?t mean
that it is a composite. We need to have a more open mind for what animals
could have done.

And we need a more open mind about how to test these things. And ask yourself, "Am I being fair in my appraisal of this fossil animal as an arboreal creature? How could I be wrong? How would I test for this?" It is all too easy to commit ad-homnium (attack your opponent and not the merit of his/her ideas). We should all be less concerned with WHO said it than what the evidence is for a particular scenario. I want to know WHY, not WHO.

Matt Bonnan

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