Why Are Rodentia And Lagomorpha Classified As Separate Orders?

[WhyWhyWhy2727]

Yeah, yeah. I know, rabbits have an extra pair of gnawing incisors, but that just doesn't seem significant enough to warrant reclassification as a separate order, especially when you take into account the fact that a guinea pig and a rabbit are 1000x more similar than a bear and a seal, but a bear and a seal are still in the same order, carnivora, despite a huge number of morphological differences, far more vast in scope and extent than merely having an extra pair of teeth. It just seems completely absurd to me. Could it be that DNA analysis has proved that the last common ancestor of the rabbit and the guinea big lived longer ago than the last common ancestor of bears and seals? How much time separates lagomorpha and rodentia, compared to say, felidae and canidae?

[Peter Pedant]

yeah hey a zoo-otobly quezzie !

I wonder if a taxonomist will step forward - problem is that if you browse a few threads it will become obvious that the average AB poster thinks a taxonomist is a Inland Revenue man ! and not a biologist ( joke but still true)

What makes an order - well up to uni we just had to learn the stuff and not why. along with comments like - oh it is a super-order now, it has changed

I was shocked to learn that nowadays - you cant take Zoo A level. ( no check box for my A level pass in 1968 ).

I can tell you that at the time they were invented - orders were NOT dependent on DNA, so the splitting was judged on the fossil record.

I can tell you this - a rodent's tail is scaly and so it is nearer some orders which it was initially thought to be not to be related to. I dont think there is anyone here who can tell you the effect of cladistics has had on zoological classification (- unless it is you)

this isnt a veiled question:
is cladistics a disease that zoology will be seen to have recovered from? (thx to Gotlob Frege)*

You probably know more about this than we do .....

* https://hsm.stackexchange.com/questions/6038/did-poincar%C3%A9-say-that-set-theory-is-a-disease

[beso]

One must always be careful assuming similarity in morphology means a close genetic relationship. Similarities can and do come about from adaptation to similar niches.

Remember the amount of time separating two lineages isn't the critical factor. Biology has gone through numerous "explosions" where diversification happens very rapidly while some lines have little change in aeons.

Similar but independent mutations to the same genes may even be involved in disparate lineages. Divergences are timed by the rate of random mutations in the genetic material that has no apparent purpose as yet.