I need to dig out my book and find the quote when I get home. I am pretty sure he was not addressing a creationist argument but what he called a “common misconception”.
Is skeletal anatomy the only identifier used in classification now? 
It is when all that’s left of the organism is, you know, a fossilized skeleton.
But… Whe… I…
Damn. :smack:
This is apparentlythe opinion of Jeffery Schwartz and John Grehan. It’s certainly a minority opinion.
To address the specific points you raised above:
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We don’t have any dinosaur DNA for analysis. Some collagen apparently has been found, and seems to be similar to that of chickens, but that is still a bit controversial. But genetics is at best a very small part of the evidence for the dinosaur/bird relationship, compared to skeletal features.
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Feathers are a derived character shared between at least some dinosaurs (mostly, possibly exclusively, theropods) and birds, and as such is evidence of a relationship between them and birds. But there are skeletal features that would demonstrate that relationship even if we had no feathered dinosaur remains; in fact, the relationship was proposed before any feathered dinos were found. It’s irrelevant whether or not other dinosaurs had feathers (although some may have had them); as long as birds are descended from one kind of dinosaur, cladistically speaking they are dinosaurs.
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We don’t know whether or not dinosaurs had copulatory organs. They probably did, since almost all present day reptiles (in the traditional sense, that is, turtles, crocodilians, lizards, and snakes) have them; the exception is the tuatara. However, some birds, including ostriches and ducks, do have copulatory organs. Even if we knew whether dinosaurs had copulatory organs, their presence or absence wouldn’t indicate much about their relationship to birds.
I hadn’t seen that, thanks. Based on what I know of the evidence, seems pretty unlikely to me.
I’ll say.
I think this is the part that’s tripping me up. Since all (?) tetrapods are descended fro a single common ancestor- some sort of lobe-finned fish- why aren’t we all fish?
We are, cladistically speaking. See Lemur’s first post in the thread. However, in this case, it’s better to consider “fish” to have no taxonomic meaning at all, and just recognize it as a loose term referring to a variety of water-living vertebrates. “Fish” includes members of three different Classes (Agnatha, Chondreichthyes, and Osteichthyes); tetrapods belong to the same clade as (some) Osteichthyes.
And of course, cladistically speaking, humans are monkeys.
Apes and Old World Monkeys share a common ancestor, and that common ancestor shared a common ancestor with the New World Monkeys.
That does not automatically mean that the A/OWM+NWM common ancestor was more similar to its “monkey” descendants than to its “ape” ones. In fact, it is thought at least by some that the NWM and A/OWM lines diverged from one of the earliest apes (i.e. apes are more “primitive” than monkeys).
In other words, apes may not be monkeys, but monkeys might be apes!
The correct term is “sea monkeys”.
That’s really not what it seems like nowadays - seems every second discovery in China/Mongolia adds to the list of feathered dinosaurs.
Jurassic Park would have been a lot less scary if the “raptors” looked like Big Bird. Or more scary, I’m not quite sure.
I could very well be true that the common ancestor of old world anthropoids and new world anthropoids more closely resembled modern apes than it resembled modern monkeys.
But that wouldn’t mean that monkeys are a particular kind of ape. Apes are a branch of the cladistic tree. They form a coherent group…all apes are more closely related to each other than any ape is related to any non-ape.
Then we find there are these creatures we call “monkeys”. And we find that some of these monkeys (Old world monkeys) are more closely related to the ape clade than they are to other kinds of monkeys (New world monkeys).
There are a couple ways we can reconcile this with traditional animal group names. One is to declare that apes, NWM and OWM are all monkeys. Another is to declare that NWM are monkeys, but apes and OWM aren’t, but that would be odd since the first creatures to be called “monkeys” were of course OWM. Another would be to declare that NWM aren’t monkeys, but something else, and apes aren’t monkeys but something else, and only OWM are monkeys. The trouble there is that everyone who sees a spider monkey is going to call it a monkey, and the idea of another 100 years of pedants insisting that spider monkeys aren’t “really” monkeys moves me to tears.
Since everyday people have no problem with the idea that apes are monkeys, and routinely call apes monkeys, and since cladistics proves that apes are a particular branch of old-world monkeys, in this case the folk taxonomy is correct and the pedants turn out to be wrong. So the next course of action is to educate the pedants and tell them to stop correcting people when they call apes monkeys, and only correct them if they call lemurs monkeys.
Personally, I’m all for considering the monkeys to be a clade with apes as a subclade, since it enables me to truthfully say that I’m a monkey’s uncle. Three monkeys’ uncle, in fact.
The common (or formerly common) misconception would be that humans are descended from modern monkeys. When people say things like ‘evolution can’t be right - it’s disgusting to suggest that we’re descended from monkeys,’ you can be pretty certain they’re not even aware of the existence (theoretical existence, at least) of a tail-less protomonkey.
What is the basis for the notion that Old World and New World monkeys couldn’t have had a common ancestor? Granted the platyrrhine/catarrhine split suggests the absence of any close relationship, and the Wikipedia article on “monkey” begins by defining the animals in terms of what they are not:
It goes on to say that they do not form a clade. But in that case, what is believed to be the ancestry of each group of monkeys? In spite of the difference in noses, Old and New World monkeys seem to share a number of structural traits in which hominids are collectively different. IIRC all monkeys lack the five-cusp molars, and in general body structure and locomotion they are more like your dog than like you, or any chimpanzee. They walk on all fours and prop themselves up with their forequarters when sitting, like a dog or cat. They tend to be deeper from spine to sternum than they are broad across. Apes, on the other hand, even the ones that don’t wear clothes and walk upright, are built to be at least semi-erect both internally and externally. We share the relatively shallow but broad chest. IMO chimps and gorillas look their most humanlike when sitting at their ease, showing their complete comfort and contentment leaning back like a human relaxing on a couch, or simply holding their torsos upright as we do when sitting cross legged on a floor.
In general I agree with the notion of cladistics because it more accurately reflects evolutionary relationships as we currently understand them. But cladistics also seems to assert th.at we are reptiles, or fish, which seems rather extreme. Is there a way that cladistics can express the assertion that Group A is descended from a type belonging to Group B, without suggesting that an A is a B?
Hence the phrase “well, fuck a duck”.
Old World and New World monkeys do have a common ancestor. I’m not sure where you got the idea they do not.
They don’t form a clade with each other, separate from that of apes. They, together with apes, are part of the same clade with respect to prosimians.
In cladistics, it’s important to distinguish characteristics that are shared because they are inherited from a common ancestor (such as an opposable thumb, quadrupedal stance, four-cusp molars) and those that are independently derived in a particular lineage. If the ancestral form of NW monkeys and apes/OW monkeys had four-cusped molars, and apes later evolved five-cusped molars, the fact that NW and OW monkeys share four-cusp molars does not indicate that they are more closely related to each other than either is to apes.
The problem only really arises because we are using English words to discuss scientific categories. This is a very crude way to indicate these relationships. Cladistics only expresses that Group A is descended from Group B; Group A is Group A. It’s when we use English words, that already have a mental connotation, that confusion arises.
Birds of course are not reptiles in the common sense of the word. However, if one is speaking cladistically, the word “reptile” has no taxonomic meaning, since crocodiles are much more closely related to birds than they are to turtles. So if we refer to birds as reptiles in a discussion like this, it is to communicate that they are a member of the clade Reptilia, rather than to indicate that they are reptiles in the conventional sense.
This is science at its finest! The stigma is gone; we no longer have to be ashamed of descent from monkeys – our kind of monkeys wore regal little crowns!