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Natural Science Forum / Biology / Paleontology / April 2006Prehistoric legged snake fossil discovered,article link
http://news.yahoo.com/s/ap/20060420/ap_on_sc/fossil_snake;_ylt=AjNtkmAXxZqyq_trC DlIaYUPLBIF;_ylu=X3oDMTA5aHJvMDdwBHNlYwN5bmNhdA-- This snake with legs was a Cretaceous marine animal. The traces of hind limbs are rudimentary. The article appeared in 2003 in "Notebooks on Geology" of which I am an associate editor: http://paleopolis.rediris.es/cg/CG2003_A01_JCR-FE/index_uk.html Evolution to the limbless state could have developed both on land and in the sea, couldn't it? If not, why not? > http://news.yahoo.com/s/ap/20060420/ap_on_sc/fossil_snake;_ylt=AjNtkmAXxZqyq_trC DlIaYUPLBIF;_ylu=X3oDMTA5aHJvMDdwBHNlYwN5bmNhdA-- > This snake with legs was a Cretaceous marine animal. The traces of hind > limbs are rudimentary. The article appeared in 2003 in "Notebooks on > Geology" of which I am an associate editor: Dear Editor 'traces' implies a vestige of something that was once more than what it is now. But 'rudimentary' implies a beginning, as if the subject were something primitive, that was on the way toward greater complexity. Can both terms be appropriate here? > http://paleopolis.rediris.es/cg/CG2003_A01_JCR-FE/index_uk.html > Evolution to the limbless state could have developed both on land and > in the sea, couldn't it? > If not, why not? It's hard to say something couldn't happen in evolution, especially when that something is a matter of loss. In what conditions would loss of limbs be most likely--land or water? I would guess water, where there's no terra firm for limbs to work with, and where a long slender animal might swim well without limbs. I'd imagine snakes evolved a long time ago, since there are no transitional species around, other than those with useless small vestiges of limbs. Snakes could invade the land just by swimming onto it, but walking onto the water is not so easy. Cliff > It's hard to say something couldn't happen in evolution, especially > when [quoted text clipped - 4 lines] > might > swim well without limbs. Maybe. No (other?) group of aquatic tetrapods have lost their legs completely (tho cetaceans have lost the hind legs), AFAIK, but the fossorial caecilians have. I don't know if the aquaticness, fossoriality, or otherwise of the aïstopods, a group of snake-like stem tetrapods, is known. > I'd imagine snakes evolved a long time ago Sometime during the later Creataceous, it would appear. Dear Cliff: You are right. The use of "rudimentary" to describe the condition of limbs that were in the process of being lost is clearly wrong. I should have wriitten 'vestigial' as you point out, or perhaps, and also incorrectly but less so, tabid. A land lizard that loses its limbs through evolutionary processes is not inconceivable if its prey were exclusively or mainly burrowers. Dear Cliff: You are right. The use of "rudimentary" to describe the condition of limbs that were in the process of being lost is clearly wrong. I should have wriitten 'vestigial' as you point out, or perhaps, and also incorrectly but less so, tabid. A land lizard that loses its limbs through evolutionary processes is not inconceivable if its prey were exclusively or mainly burrowers. > Dear Cliff: > You are right. The use of "rudimentary" to describe the condition of > limbs that were in the process of being lost is clearly wrong. No, it's not wrong. very imperfectly developed or represented only by a vestige <the rudimentary tail of a hyrax> > I > should have wriitten 'vestigial' as you point out, or perhaps, and > also incorrectly but less so, tabid. > A land lizard that loses its limbs through evolutionary processes is > not inconceivable if its prey were exclusively or mainly burrowers. No. 'Rudimentary' has nothing to do with coming or going....it has to do with 'basic'. "Of a primitive kind the equipment of these past empire-builders was rudimentary." http://www.m-w.com/dictionary/rudimentary I agree that 'rudimentary' isn't necessarily wrong. But if one happens to have a definite belief as to whether the rudiment is something new coming in or something old going out, the language should reflect that. 'Rudimentary' and 'primitive' and 'basic' are all often ambiguous in this sense, unlike 'vestigial' for old, and 'incipient' for new structures. Cliff > This snake with legs was a Cretaceous marine animal. The traces of hind > limbs are rudimentary. The article appeared in 2003 in "Notebooks on [quoted text clipped - 3 lines] > in the sea, couldn't it? > If not, why not? Could have however snakes have short tails and long bodies. Going limbless in the sea you tend to get a long tail and a short body though they normally retain at least a couple of flippers. Grass crawlers have long tails. Burrowers on the other hand have long bodies and short tails and snakes are known to have undergone eye degeneration and redevelopment. >> http://news.yahoo.com/s/ap/20060420/ap_on_sc/fossil_snake;_ylt=AjNtkmAXxZqyq_trC DlIaYUPLBIF;_ylu=X3oDMTA5aHJvMDdwBHNlYwN5bmNhdA-- > This snake with legs was a Cretaceous marine animal... No! This NEW snake (_Najash rionegrina_ Apesteguia and Zaher, 2006) was terrestrial. Many recent snakes have remnants of the pelvis and some have a femur which may bear an external claw, but ALL of the Cretaceous snakes (where the pelvic region happens to be visibly preserved) have tibia and fibula, and some have tarsal bones and phalanges. Vestigial, rudimentary, whatever... but more interesting that we have numerous intermediate stages in the fossil record, from complete footed limb to complete loss. Najash is Turonian in age, but most of the other limbed snakes (marine) are Cenomanian, a few million years older. Terrestrial and apparently burrowing snakes (Coniophis from Utah) are also known in the Cenomanian, as are terrestrial madtsoiids (the group to which Najash belongs based on its diagnostic features, although Apesteguia and Zaher fail to mention this fact). The hype is unnecessary and false: it's not the oldest, most primitive, first or most complete of anything! By press standards, there's not really any news here, but (for a small number of people) any early or primitive snake fossil is very interesting and exciting for real scientific reasons. |
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