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Re: Sex


External fertilization of eggs in dinosaurs probably did not occur because there are no known amniotes (reptiles, birds, mammals) that have external fertilization.  External fertilization usually occurs in anamniotes (amphibians, fish) because there is water for the sperm of the male to swim in.

If you or anyone on this list has ever seen elephant mating, the penis of the elephant is like a mobile probicis that can be manuvered into position during the course of copulation.  The reason for this is because even though elephants will copulate on top of one another, there is a great distance between the male and female genitalia.

In many reptiles, there is an internal hemipenis which again can be manuvered -- because the penis is bifurcated (has two halves), this affords the reptile with a hemipenis better chances of copulation with a female.

In some camels, the female lays on the ground sideways and the male mounts her sideways.

In some birds, sperm transfer from the male to the female merely requires a moment's contact.

Therefore, even though stegosaurs had plates and spikes which may have prevented mating in the standard mammalian way, soft tissue modifications to genitalia and/or different positions may have afforded copulation in these dinosaurs.

External fertilization, while an interesting idea, is probably outside the realm of probability for dinosaur copulation and fertilization because it is not found (so far as I know) in living amniotes.

Matt Bonnan

----Original Message Follows----
From: "Gavin Rymill"
Reply-To: "Gavin Rymill"
Subject: Sex
Date: Sun, 25 Feb 2001 00:49:15 -0000
For those of you who have seen Big Al, you will have heard their little in-joke which is relevant to my point -
Two Stegosaurs approach each other to mate and the narrator notes that they are about to attempt what is "a very complex task" for them. But whoops! Before they can get down to business, Big Al arrives on the scenes and frightens them off, thus preventing us seeing something quite amazing.
How the hell did Stegosaurs mate??
I would love to hear anyone's theory.
But it occurrs to me that if we have so much of a problem finding a comfortable position which would allow physical coupling, then what's to say that they didn't do what other animals do today - Perhaps the female layed the unfertilised eggs on the ground and then the male fertilized them externally.
Has this been considered before? Is there any reason why it should be discounted??
If it was the case for Stegs, then why not other dinosaurs whose sex lives seem to have been anything less than enjoyable, such as Diplodocus?
Thoughts please.
www.gavinrymill.com ICQ: 33916140 / AOLIM: ExtinctGav

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    • Re: Sex
      • From: "Gavin Rymill" <gavin@gavinrymill.com>