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The evolution of vivparity in squamates.

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Posted by: salliva2000 at Mon Jan 7 08:22:15 2008  [ Report Abuse ] [ Email Message ] [ Show All Posts by salliva2000 ]  
   

(orig. from venomdoc.com)

Iīm doing a rapport about "oviparity to viviparity" among squamates. Iīve been reading a lot of articles, especially works from Richard Shine.

I need some sort of focus to handle after, instead of getting a muddy and confusing rapport, and there is a question, wich I almost are certain on already has been answered in several articles, that Iīve been reading...but I wanna be sure.

According to Richard Shine the evolution among squamates, seems (and has always been in history time?) that the evolution from oviparity to viviparity (and ovovivivparity, that must be the "middle-link" in between oviparity and viviparity) has only been going in that one direction...In other words that the evolution is starting from oviparity to viviparity and only in few cases has it been evolving reverse again (think, it is among some few vipers with more...?)

Is this right?...If so, then I can base my rapport and work on analyzing, wich factors thatīs forcing this form of reproduction, such things as prolonged uterine retention in climates with hetereogenous temperatures, plus many other mechanisms that are forcing theese hypoteses about the development from oviparity to viviparity, in time.

I canīt figure if this is right or still just a bunch of hypoteses in a chaos of who support this and who donīt...

Is the evolution primarily among squamates going in that one direction from oviparity to viviparity or? I really need answers thatīs supported by researches, practical projects and so on, and not opinions on what people "have an idea on", if you know what I mean....

Maybe I havenīt been reading enough and maybe I even didnīt understand it, so please donīt blame Richard Shine if it is so, allright.

Thanks, and thanks for this fantastic site!
_________________
Danny Morck, Denmark


   

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