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MATING DINOSAURS ETC



Aren't we all having a wonderful time. I'm resisting the temptation to reply to
messages about New Zealand fauna, so let's see if I can keep this one on track:
dinosaur mating.

First off: some of you have assumed that extinct dinosaurs were 'cloacal
kissers', as are most extant birds. Applying the EPB (Extant Phylogenetic
Bracket), we find that crocodiles on one hand, and basal birds on the other,
both have a penis in the male. It is therefore safest to assume that non-bird
dinosaurs had a penis too, and loss of it in derived birds is an advanced
character unique to that group. Loss of the penis ('bobbitisation') in advanced
birds (the Neoaves of Sibley et al.) may be a weight reduction adaptation. A
more recent argument is that penis reduction and loss was selected for by
females, apparently as penis loss promotes sperm competition between males - the
arrangement female birds maintain by mating with multiple partners.

Proximal chevrons on dinosaur tails probably anchored penis muscles, as they do
in crocs, and according to some reports purported male skeletons possess larger
promixal chevrons that purported females. It would be interesting indeed to see
if such a relationship is statistically viable - AFAIK it's based on examination
of only a few _Tyrannosaurus rex_ specimens. 

Those of you who are thinking of restoring mating dinosaurs are therefore well
within your rights to depict male dinosaurs with large erectile genitals. Look
at the organs of crocodiles and non-neoavian birds (e.g. ducks, ratites - I've
seen many a duck penis and the occasional ostrich one) for inspiration. Though
there are several well known restorations of mating dinosaurs (e.g. Giovanni
Caselli's mating camptosaurs in Halstead's _The Evolution and Ecology of the
Dinosaurs_; mating diplodocids in Rothschild and Tanke's palaeopathology paper),
it's unfortunate that dinosaur penises are never depicted. Presumably, in the
largest animals, they would have been impressive organs: a giant sauropod of 30
m or more may sport a 4 m whopper. Artists please note that all dinosaur
genitals exit from behind the ischium just under the tail - not from before the
pubis, nor between the pubis and ischium.

Finally, for now, Dann Pigdon wrote that..

> Dogs, foxes, probably most canines, mate back-to-back, a position that
> is ultimately extremely painful for the male since a certain
> sensitive organ has to rotate through 180 degrees. 

This is not correct. Canids mate in the conventional mammalian manner (I
hesitate to say dogg... maybe I'd better not). At the point of ejaculation the
glans swells to such a size that the male is unable to withdraw, and the animals
are locked together for a while. At this point they often panic, and the male
climbs off and tries to pull away. It is at this stage that the two may be
pulling in opposite directions - eventually the penis returns to normal size and
the two can part. This adaptation may have evolved to give the sperm the maximum
amount of travel time before there is the risk of invasion from a competing
male.

For those of you that may be wondering, porcupines mate in the conventional
mammalian manner too, despite claims to the contrary (and I've read plenty!).

As for how prickly stegosaur managed it, well... where is Neil when you need
him?;-)

The countdown continues: 15

"His brain only lasted this long because he never uses it"

DARREN NAISH