It doesn’t work that way. Birds and alligators are more closely related to each other than either are to turtles. But turtles and alligators are both reptiles and birds are not. For that matter, humans and lobe-finned fish are more closely reltated to each other than either are to ray-finned fish. That doesn’t make lobe-finned fish humans, nor does it make humans fish.
Monkeys are monkeys, apes are apes and apes are not monkeys. Nor are monkeys apes.
Now, if you want to call apes Catarrhini, that would be correct. 
To expand on this, smaller animals live “faster” than larger ones. The heart rate of mammals scales according to the formula h.r. (min[sup]-1[/sup]) = 241 M[sub]b[/sub][sup]-0.25[/sup], where M[sub]b[/sub] is the body mass in kilograms. Thus, shrews have heart rates of up to 1000 beats / minute, while elephants have a much lower ~30 beats / minute. Smaller animals also have higher metabolisms than larger ones, and the scaling factor is the same (metabolic rate is proportional to M[sub]b[/sub][sup]-0.25[/sup]). The metabolic time is the inverse of the metabolic rate; thus, metabolic time scales by M[sub]b[/sub][sup]0.25[/sup].
The metabolic time is essentially the animal’s lifespan; not surprisingly, we learn that smaller animals live fast and die “young”. The result of metabolic rate and heart rate being scaled to the same factor (-0.25) is that there tends to be a (roughly) constant number of heartbeats per lifetime, regardless of size. Of course, this is all speaking in generalities, and this relationship breaks down completely with respect to humans (who, based on body size alone, should live only about 20 years or so). I’m not sure where our closest relatives fall within the scale, either. They could be living as long as one would expect from their body size, or they could be anomalous like us - I have no data regarding this.
And, of course, this does not explain why the relationship between body size and lifespan exists, only explaining that it does exist.
That depends on who you ask 
If you ask a Linnaean taxonomist, then sure, s/he will answer that birds are in Class Aves, and alligators and turtles are in Class Reptilia, and never the twain shall meet (aside from the small detail that birds evolved from dinosaurs, of course) - one must be placed in one Class or the other, thus one can only be one or the other.
To a cladist, however, taxonomic groupings are nested, and one does not stop being a member of a group simply because one is nested further down. Thus, birds, having descended from dinosaurs, remain dinosaurs. Dinosaurs, being descended from earlier reptilian ancestors, remain reptiles. Thus, birds remain reptiles as well. Similarly, humans remain sarcopterygians (making “fish” paraphyletic…), just as much as we remain tetrapods and synapsids and therapsids and cynodonts and so on.
I have often wondered if this general rule regarding size and lifespan was affected in any way by the number of cell divisions an individual mammal, say, undergoes in its lifetime.
Let me try to explain. If you consider, say, a shrew and a blue whale, both originally started when an egg and sperm met and the resulting cell starts to divide. First you have two cells, then four, then eight etc. Given that the size of most types of eukaryotic cells doesn’t vary much across species (I think, although I could be wrong here) the whale must undergo many more cell divisions to get up to its adult size. We also know that most non cancerous cells are programmed to only divide so many times…the inability of normal cells to continue dividing indefinitely is one of the causes of “old age” (senescence).
So are the whale’s cells programmed to divide many times more than the shrew’s cells, or does the shrew’s high metabolism mean higher turnover and shorter lifespans for its cells?
I understand how clads work. But to say that birds are reptiles is meaningless until you create a new word for non-avian reptiles. One can just as easily say humans are reptiles or that humans are fish. Now, if we commonly used the Latin names for these clads instead of the common names, yes it might make sense to call apes Catarrhini and just dispense with the term monkey altogether.
There is a difference between being in a clad with monkeys and being monkeys. I’m not sure if there is a term used to lump Catarrhini and Platyrrhini together. Let’s say it’s “CataPlaty”. Unless you are willing to to say that CataPlaty = monkey, then you can’t say apes are monkeys. Any reasonable definition of “CataPlaty” would be “monkeys and apes”, or “new world monkeys, old world monkeys, and apes”.
I wonder if heat loss is a signifcant factor, as well. Mammals tend to maintain a constant body temperature, of course, but small mammals will lose heat more quickly because of their higher ratio of surface area to volume. Thus, they need to “burn faster” to maintain a constant temperature. This results in higher metabolism.
Since metabolic rate is essentially the rate of oxygen consumption, we also find that when scaled to body mass, the rate of oxygen consumption scales the same as heart rates: M[sub]b[/sub][sup]-0.25[/sup] (that is, the rate of oxygen consumption per kilogram scales the same). So, smaller mammals, while not consuming more oxygen than their larger brethren, consume oxygen at a much higher rate per kilogram.
So, when you are small, you lose heat quickly, thus must utilize more oxygen per unit weight than a larger mammal. This leads to a necessarily higher metabolism, and a need for the heart to beat faster in order to keep all those cells supplied with oxygen at the required rate to maintain body temperature at the required level. The higher heart rate results in a lower metabolic time (i.e., lifespan). Conversely, large mammals lose heat more slowly (having a lower surface area - to - volume ratio), so have a reduced oxygen consumption rate per unit weight, so do not require rapid heartbeats, so have a greater metabolic time; they live longer by virtue of being larger.
All of the above is speculation on my part, since physiology is by no means my area of expertise (to the extent that I even have one…).
Not really. There is little you can say about non-avian reptiles that does not equally apply to the avian ones - that’s why they’re nested in the first place. If you want to discuss the uniting features of lizards and turtles and snakes and dinosaurs and crocodiles, you pretty much have to include birds because they possess those traits as well. If you want to discuss specific groups of reptiles, while excluding birds, you can certanly do that: you can talk of crocodilians or lacertilians or testudines with nary a mention of aves. But if you want to talk about all of them, well, avians have the
goods just as much as a member of any of the other groups.
Same deal with apes and monkeys (if you can consider the ancestral Anthropoidea species to be a taxonomicaly-sound monkey - a big if, which I am not claiming to agree with): if you want to talk about what all monkeys (old and new world) have in common, you pretty much have to include the great apes as well, because old and new world monkeys do not share a common ancestor that isn’t also shared with humans and gorillas and chimps and such.
“Monkeys”, in the common vernacular, excludes apes, so the group is paraphyletic (again, if…). If, however, we restrict the definition of “monkey” to be “a member of clade Platyrrhini”, then we can make a distinction between the two, and talk about monkeys and apes separately all we like.
The group that contains both Catarrhini and Platyrrhini does indeed have a name: Anthropodea. As for the second sentence, that is the point, but, as I mentioned above, it is predicated on a big “if” statement: IF the ancestral Anthropoidean was what can be considered a monkey, THEN all its descendants are, by (cladistic) definition, monkeys. So, mkl12 was technically correct in his post (he did say, “By that definition…”). However, we cannot readily say (or, at least, I cannot readily say) that that ancestral anthropodean was a monkey, therefore it is not correct to say under the current scheme that apes are monkeys. He was technically correct, but not practically correct
I meant “third”.
Except, of course, everything that differentiates them in the first place.
Like being cold vs warm blooded to name one obvious difference.
Unless you happen to be a parrot ( or at least certain species of parrot ). They’re running very close to the human record ( Churchill’s Charlie, lately in the news, is reputedly 104 and I’ve heard of a Sulfur-Crested Cockatoo that hit 110 - that might be apocryphal, though ). Number three I believe is the Fin Whale, which at least has the good grace to fit into your thesis ;).
Ah, but there you’re talking about synapomorphies - shared, derived characters. Those are what make birds birds, rather than what makes other reptiles reptiles by virtue of those traits not being present. Reptiles are not characterized by lacking feathers, for example. That’s a feature that diagnoses birds (though maybe not so much anymore), and allows them to be placed in a subset of reptiles in the first place.
You picked on the one instance where I failed to maintain consistency! The formulas I presented are valid only for mammals. Birds are weird, so I wouldn’t be surprised if, for example, parrots outlived ostriches (do they?). I know miscellaneous reptiles (non-avian e.g., turtles and crocodiles) can live a very long time (longer than an mammal of equivalent size), but I don’t know how they scale with size; I would guess they do scale, just with a different exponent.
I don’t follow what you are saying. I actually didn’t mention feathers specifically for the reason you state-- you don’t define a group by what it’s not. I mentioned cold bloodedness, which is a characteristic shared by reptiles like alligators and turtles, but not by birds. If you’re saying that warm bloodedness is derived from cold bloodedness and thus cold bloodedness is not a valid shared characteristic of reptiles but not birds, then what you are essentially saying is that warm bloodedness is cold bloodedness. Which begins to sound a lot like “apes are monkeys”.
Actually I believe they’re fairly close, with maybe a bit of an edge to certain long-lived parrots. What I’m curious about though, is why are they so weird? I mean ectotherms like giant tortoises ( who I believe hold the vertebrate age record ) don’t bother me - obviously they’re operating under a different set of contraints. But birds are endotherms - so what are the physiological differences that set them apart from mammals in terms of aging?
Portuguese (and I think Spanish as well) does not have a word for ape . We call monkeys and apes macaco .
Do you mean that these languages are contrary to scientific convention? Since when does science command a language?
Portuguese speaking scientists call apes macacos antropóides , but the majority of the population of Portuguese speaking countries does not even know this calling.
This is an extremely interesting question, but there is little information. Birds live far longer than mammals of an equivalent body weight - for example, hummingbirds in captivity can live more than 10 years, vs only a matter of months for a shrews, which are similar in weight. Gulls live much longer than cats, even though cats are much heavier. And so on.
This study found that there is a relationship between genome size and lifespan within birds, but the significance of this is obscure.
One answer would be that we are using English for this conversation and there is no reason to absorb the linguistic ambiguities of other languages into English. But even English isn’t pure on this. Macaques living on Gibralter are referred to as “barbary apes” even though this is technically incorrect. Maybe that derives from the Spanish word, per your postulation.
But it seems that Portuguese would be even more confusing, since there is a type of monkey called a “macaque”. How do you differentiate between macaques and other types of monkeys in coloquial Portuguese?
But the real answer is as you guessed-- the scientific convention is to differnetiate between apes and monkeys. And unless it is overly cumbersome to do so, common usage should follow suite. So that if someone says: “Some monkeys have been observed to recognize themselves in the mirror”, that would be an untrue statement. Only apes (of the primates) have been shown to do this.
I’m saying “cold-bloodedness” is not a trait which can be used to diagnose reptiles of any sort because a) not all reptiles possess that trait, and b) other animals besides reptiles possess that trait: amphibians, fish (the comon definition thereof), bugs, etc. Thus, “cold-bloodedness” by itself is insufficient to unite all reptiles sans birds, and establish them as a valid group. Indeed, my point is that there is no valid character which serves to distinguish all non-avian reptiles, because any such “primitive” reptilian characters are also shared by birds - again, that’s why cladists place them within Reptilia in the first place. You can talk about birds without discussing reptiles, but you can’t really talk about all reptiles separately from birds. You can talk about individual, or even several, distinct groups of reptiles (again, e.g., turtles, snakes, iguanas, etc.), but any traits which are shared by all of them are also shared by birds.
OK. Sorry it took so long to sink in.
But that does leave me wondering about scales. Can we say that all reptiles (and only reptiles) have scales? Or are there some reptiles w/o scales or some non-reptiles w/ scales? Or are the various scales of reptiles as different from each other as feathers and hair are from “scales”?
Birds have scales, of course, on their legs - one of the characters that unites them to “reptiles.”
Among the amphibians, scales (though small ones) are present the legless caecilians, as well as some fossil forms.
And of course most teleost fish have scales, though I’m not sure if they are homologous with reptile scales.
I don’t argue against the proper use of scientific convention in English. I argue against your post where you seem to say that languages that have no word for “ape” are unscientific.
The denomination “macaque” as a kind of monkey originated in Portuguese and passed into English trough French (Spanish for monkey is mono ).
In Portuguese the macaques are called macacas de Gibraltar . So, the generic name in Portuguese turned to a specific one in other languages. The same has occurred with “cobra”, wich means “snake” in Portuguese. A kind of Asian and African snakes where called by the portuguese cobra capelo (snake with a hood), because their necks inflate, taking the appearance of a hood. Other languages have dropped the “capelo” part and called this snakes simply “cobra”.