So an iguana and snapping turtle are the same thing because they belong to the same clade? The OP is not asking about the relationship between humans and an entire clade, but one specific species to another.
All of your seventh cousins are equally related to you even if one of them looks a lot like his great-great-grandfather. His great-great-grandfather was more closely related to you, but he’s dead. And what you decided makes this cousin more like his great-great-grandfather will be arbitrary. He may have the same look to his nose, eyes, and jaw, but have a different blood type, different height, and an extra finger on each hand.
Time goes forward. Changes happen with time. None of your seventh cousins are closer to being their ancestors (and therefore, more related to you) than any of the others in any way that’s meaningful to measure.
That said, if you look at not seventh cousins but all cousins your age (modern cousins), you’ll be comparing some fifth or sixth cousins with seventh or eighth cousins. The fifth cousins are more closely related (even if they look nothing like great^X grandpa). That’s easy to pick out with modern records, but harder to do with fossils.
Effectively, yes. As was mentioned upthread, whatever traits we share with an iguana are going to be shared between us and a snapping turtle, as well, on account of us all being amniotes. There won’t be any definitive traits which could place either a snapping turtle or an iguana closer to us than the other is.
Just to expand (although it’s already been said) you are insisting on changing the definition of “related to.” In both taxonomy and genealogy, the degree of relationship is determined with reference to the most recent common ancestor. The degree of genetic similarity is just that - the degree of genetic similarity - not relationship.
With reference to humans, yes. With reference to other reptiles, no.
And we have answered the question. Humans are equally related to all species of reptiles. That’s the answer, even if you don’t want to accept it.
Do we have a good idea of what the most recent common ancestor of reptiles and mammals even looked like?
Is he the particular human or the particular reptile?
This is like asking which of my father’s brother’s children is more closely related to me.
Therapsids. the picture makes them look like an unfriendly cross between a cat and a monitor lizard.
Therapsids aren’t basal amniotes, they are basal synapsids. Reptiles and mammals had already split apart by then, and therapsids are firmly on the mammal side, even though they aren’t true mammals.
Therapsids are basal to all mammals, but from what I can gather the reptiles had split off well before the Therapsids developed. I don’t know if there are any good fossil indications of what the common ancestor of Therapsida and reptiles looked like.
Therapsids were full-on synapsids. The common ancestor would actually have looked more lizardy, like Casineria.
This wikipedia article could be helpful: Amniote - Wikipedia.
The common ancestor of synapsids (the grab-bag of mammals and mammal-like critters) and reptiles probobly looked like a pretty standard lizardy critter. If you saw one in a zoo and the the label said “lizard”, you wouldn’t raise an eyebrow. You’d have to really dissect the thing to determine exactly why it isn’t a lizard, just like, say, a tuatara isn’t a lizard, it just looks like a lizard.
Pretty much like a lizard. The earliest amniote known was Hylonomus. The earliest member of the lineage that led to the mammals, the synapsids, was Archaeothyris. I haven’t found any illustrations of the earliest members of the Sauropsida, the clade that led to Reptilia, but I’m sure they weren’t much different externally.
Without further qualification, yes. It’s like asking which of two editions of a book is more closely related to the author’s original manuscript–one where there are ten spelling mistakes in various words, or one where two pages have been swapped. But as long as you identify each possible type of error and assign some arbitrary weight to them, there’s no reason you can’t just count them up to quantify the similarity of any two texts. Yes, it’s arbitrary, but it’s internally consistent, and may well allow one to draw meaningful inferences about the real world. This process, known as edit distance, is used all the time in computer science and related fields (such as mine, computational linguistics), and I would be very surprised if it has not already been applied to genetic sequences in bioinformatics. Wikipedia has an article on distance matrices in phylogeny which seems to be relevant, though as I’m no geneticist I can’t say for sure.
sleestak
Genetically, all life on earth is related, and although we do not have the information, their is a genetic relationship that is established with each generation. Genealogy uses this to determine the relationship of cousins, people who share a common ancestor. You are not as closely related to all of humanity as you are to your first cousin. Now taxonomic systems differ, and certainly some are no better at determining genetic relationships than your bathroom scale can define your height, but that does mean that all people are the same height.
The answer is that you don’t know, and are attempting cover that up with a silly semantic argument. I’ve already explained several times that there is a definitine genetic relationship between any two animals that ever lived.
You can’t give an exact answer because of the lack of evidence as I’ve said several times. But cladistics are actually a means of making the qualitative comparisons and explaining the distance between species or specific animals. But apparently the experts in cladistics here don’t want to share that information.
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True. Generation time can make some difference to branching rate, and is sometimes taken into account in trying to estimate the time since clades have diverged.
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Except occasionally when realizing how the flaw in their argument.
No, this is asking if a brother’s children are more closely related to a person than his brother’s grandchildren. Unless there’s a Chinatown situtation going on, this person is more closely related to his brother’s children than his brother’s grandchildren.
And genetically there is an definitie path between any two animals which does not require interpretation. We just don’t have all the intermediate manuscripts in this case, but there are ways to make reasonable guesses, or at least state the truth, that the answer is unknown.
Surprisingly, a Bing image search for “casineria” is NSFW!
You’ll have to give us a URL. I’m only getting SFW stuff.