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Internal Testes (in afrotherians)



Jaime,
Just to clarify. Elephants, sirenians, hyraxes, and desmostylians are only a subclade of afrotherians (called Uranotheria). Are internal testes also found in other afrotherians (tubulidentates, macroscelidids, tenrecs, golden mole, etc.)?
-------Ken
*******************************************************
Jaime wrote:
This said, the condition in afrotherian mammals
(elephants, sirenians, hyraxes, and fossil
desmostylians) of internal testes is a key feature,
and may be further explained by this means but not, I
believe, tested. This was suggested as further
comparison in the paper, and when the library as ACofI
opens again, I can check. However, it requires the
animals be endothermic, and possibly homeothermic, to
support the counter-current system in this fashion.
Could be wrong.

  Core temp in small endothermic dinosaurs will be
lower than larger animals based on mass estimates
versus surface area (Henderson, 1999). They will not
require this, but larger endotherms will, and this
might suggest that hyraxes evolved from larger
afrotheres. However, larger dinosaurs, such as
sauropods exceeding a couple of tons, or the largest
theropods, could have lower mean temps than their
smaller kin (Farlow, 1986, etc.) and internal testes
would not need to be counter-current or external to
operate well, unless afrotheres operate by a different
structure or system.

  Birds, as I understand it, may not need a
counter-current, but could use heat-exchange through
the air sacs instead. I don't know, but if any
ornithologists out there know, please.... This could
be derived through descent, as both basal reptiles and
crocs have internal genitalia, so....

=====
Jaime "James" A. Headden

  Dinosaurs are horrible, terrible creatures! Even the
  fluffy ones, the snuggle-up-at-night-with ones
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