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Re: parthenogenetically derived reptile offspring

It may also have been an inherited characteristic from the beginning of the origin of life. The missing link here (excuse the pun) is recognizing that many, many primitive (poor term) organisms exhibit parthogenesis. If parthenogensis is an independently created (on the tree) characteristic that was/is replicated numerous times across (parallel evolution) widely diverse and unrelated species, the discussion may be weighted heavily in favor of it being a very early ability indeed. This does seems to be a trait which is shared by many "simple" organisms (excuse the term please) AND is even exhibited in more further derived (more distantly related??) forms. This is highly suggestive of an origin (in the code) much earlier in life's lineage. This may simply show the selective pressure that recreates the genetic expression of the ability at "will". Knowing the tree's branching exact point may not be the issue because it may be a trunk thing. Recognizing that many many simple forms exhibit this trait is highly suggestive how far back it originated in the tree life. This is useful by creating the inference that once it is in the code, it can be expressed at the first need given the right circumstances. Many very simple forms use this kind of reproduction and obviously several highly derived forms are capable of expressing the old genes. My overly belated point is, once a trait is in the common shared genetic code, the ability exists in all species from the original lineage whether it is ever expressed or not.

(self censored discussion of human parthogenesis 2000 years ago)

There is every reason to suspect that some dinos had the ability though it will be pretty hard to prove since as any kind of shotgun gene sequencing (do a google on that term!) isn't going to happen on material that old. The statistical probability of successful virgin egg drop in dinos over the millions (and millions) of generations of thousands (and thousands) of different forms is huge. Taking into account the sheer diversity in the lineage, the absolutely huge number of individuals/forms involved and the propensity of somewhat related species having the characteristic also has some bearing on the discussion. The amount of time involved during the reign of the dinosaurs alone is staggering. Talk about opportunity for evolution to experiment. (and it did!)

Vertebrates certainly show a wide variety of abilities for sex- determination mechanisms. In crocs, temperature is the determining factor, some fish can morph mid-stream (no pun there!) from female to male or vice-versa. The fact that many forms have "done it" via parthogenesis is highly suggestive that other related forms have or have had the ability. One certainly should not dismiss the possibility. Absence of evidence is not evidence of absence especially in a world where two headed fossils are just being found. Uniformitarianism is alive and well.

It all may boil down to that Christmas turkey (no wait, ..... turkeys have been parthogenetic too). Modern avian theropods...... Goes to show that turkeys are so ugly that the only way some of them can reproduce..... Too much caffeine!

Happy Holidays all on the DML...

Frank (Rooster) Bliss MS Biostratigraphy Weston, Wyoming www.wyomingdinosaurs.com

On Dec 23, 2006, at 6:01 AM, David Marjanovic wrote:

Concerning parthogenesis and dinosaurs, the case of the turkey would be more relevant. There is a domestic breed of turkey ( I could look up the name somewhere but I'm too lazy to do it right now) for which parthogenesis is a very normal or even the default way of conception.

Really? I've heard of a case, but (as in the Komodo monitor) all offspring of parthenogenesis in birds are automatically male and can't repeat the trick.

I don't know how this has come to be; but nevertheless, it shows the capacity for parthogenesis exists in the dinosaurian line.

We don't know where in that branch of the tree it evolved...