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Jim Willemin
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 Posted: Sun May 27, 2007 10:21 am Post subject: Speaking of whales... |
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Does anyone know if cetaceans have a sense of smell? How about any sense
that detects chemical gradients in seawater, similar to how smell detects
chemical gradients in air? It seems to me that whales don't spend a lot of
time sniffing the air... |
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John Wilkins
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| Posted: Mon May 28, 2007 7:26 am Post subject: Re: Speaking of whales... |
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Robert Carnegie <rja.carnegie@excite.com> wrote:
"massively awful"?
--
John S. Wilkins, Postdoctoral Research Fellow, Biohumanities Project
University of Queensland - Blog: scienceblogs.com/evolvingthoughts
"He used... sarcasm. He knew all the tricks, dramatic irony, metaphor,
bathos, puns, parody, litotes and... satire. He was vicious." |
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Ken Shackleton
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| Posted: Mon May 28, 2007 8:15 am Post subject: Re: Speaking of whales... |
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On May 27, 5:33 am, rich...@cbrp.co.uk wrote:
| Quote: |
On May 27, 11:21 am, Jim Willemin <jim***willemin@hot***mail.com
wrote:
Does anyone know if cetaceans have a sense of smell? How about any sense
that detects chemical gradients in seawater, similar to how smell detects
chemical gradients in air? It seems to me that whales don't spend a lot of
time sniffing the air...
Whales may not have, but plesiosaurs did.
Their internal and external nares are offset, and the external nares
is shaped so that the flow of water over the snout draws water from
inside the mouth, though a large cavity in the front part of the
skull, and out just in front of the eyes.
At close quarters, and unlike whales, they had good binocular vision
to home in on the prey.
RF
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I have a question....is it known whether plesiosaurs laid eggs on land
or gave birth to live young at sea? |
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Guest
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| Posted: Mon May 28, 2007 11:00 am Post subject: Re: Speaking of whales... |
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On May 28, 4:15 am, Ken Shackleton <ken.shackle...@shaw.ca> wrote:
| Quote: |
On May 27, 5:33 am, rich...@cbrp.co.uk wrote:
On May 27, 11:21 am, Jim Willemin <jim***willemin@hot***mail.com
wrote:
Does anyone know if cetaceans have a sense of smell? How about any sense
that detects chemical gradients in seawater, similar to how smell detects
chemical gradients in air? It seems to me that whales don't spend a lot of
time sniffing the air...
Whales may not have, but plesiosaurs did.
Their internal and external nares are offset, and the external nares
is shaped so that the flow of water over the snout draws water from
inside the mouth, though a large cavity in the front part of the
skull, and out just in front of the eyes.
At close quarters, and unlike whales, they had good binocular vision
to home in on the prey.
RF
I have a question....is it known whether plesiosaurs laid eggs on land
or gave birth to live young at sea?
|
That almost certainly gave birth to live young. Specimens of
Keichosaurus, a small Triassic sauropterygian and close to the
evolutionary lineage which led to plesiosaurs, have been found with
embryos in the body cavity more or less where they would be expected
in a viviparous animal. There is a plesiosaur specimen associated
with what is probably embryonic material, but I have only seen a few
photos of it, and there is no scientific publication to date.
In many ways this is a bit of puzzle. We know that Ichthyosaurs, which
are found in the same deposits as plesiosaurs, gave birth to live
young because we have a number of specimens containing embryos. Other
than one unconfirmed specimen, there is no similar evidence for
plesiosaurs, which seems unlikely if their birthing strategy was the
same. It is also the case that we have very few juvenile, or simply
very small plesiosaurs, again unlike the case with ichthyosaurs in
which we find indivduals of widely different size from the same taxon.
A possible scenario is that whereas ichthyosaurs gave birth in the
open sea, plesiosaurs gave birth in sheltered nurseries, and only set
out into open water when they were well-grown. The evidence for this
is rather tenuous. I described a fauna of plesiosaurs and ichthyosaurs
from a site on the Jurassic/Cretaceous boundary in North Lincolnshire
which included very small specimens including a very small juvenile
limb bone. The palaeogeography of the site shows that it was a sandy
lagoon, probably in the estuary of a large river system. This is very
different from the facies in which we usually find plesiosaur remains.
RF |
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nmp
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| Posted: Mon May 28, 2007 11:00 am Post subject: Re: Speaking of whales... |
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Op Sun, 27 May 2007 20:15:50 -0700, schreef Ken Shackleton:
| Quote: |
I have a question....is it known whether plesiosaurs laid eggs on land
or gave birth to live young at sea?
|
Hmmm, interesting. I found this:
<http://www.oceansofkansas.com/plesiosaur.html>
Where it says:
"There is still some controversy about whether or not they laid eggs, but
evidence found in South Dakota and Kansas seems to point toward
plesiosaurs giving live birth like ichthyosaurs and mosasaurs. It is
hard to imagine a forty-foot plesiosaur struggling up on a beach to lay
eggs like a sea turtle. Besides having limbs that were unsuitable for
travel on land, there are several good physiological reasons (such as
over-heating, and not being able to breathe) why egg laying would
probably have not been possible in plesiosaurs.." |
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Ken Shackleton
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| Posted: Tue May 29, 2007 7:32 am Post subject: Re: Speaking of whales... |
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On May 28, 3:38 am, rich...@cbrp.co.uk wrote:
| Quote: |
On May 28, 4:15 am, Ken Shackleton <ken.shackle...@shaw.ca> wrote:
On May 27, 5:33 am, rich...@cbrp.co.uk wrote:
On May 27, 11:21 am, Jim Willemin <jim***willemin@hot***mail.com
wrote:
Does anyone know if cetaceans have a sense of smell? How about any sense
that detects chemical gradients in seawater, similar to how smell detects
chemical gradients in air? It seems to me that whales don't spend a lot of
time sniffing the air...
Whales may not have, but plesiosaurs did.
Their internal and external nares are offset, and the external nares
is shaped so that the flow of water over the snout draws water from
inside the mouth, though a large cavity in the front part of the
skull, and out just in front of the eyes.
At close quarters, and unlike whales, they had good binocular vision
to home in on the prey.
RF
I have a question....is it known whether plesiosaurs laid eggs on land
or gave birth to live young at sea?
That almost certainly gave birth to live young. Specimens of
Keichosaurus, a small Triassic sauropterygian and close to the
evolutionary lineage which led to plesiosaurs, have been found with
embryos in the body cavity more or less where they would be expected
in a viviparous animal. There is a plesiosaur specimen associated
with what is probably embryonic material, but I have only seen a few
photos of it, and there is no scientific publication to date.
In many ways this is a bit of puzzle. We know that Ichthyosaurs, which
are found in the same deposits as plesiosaurs, gave birth to live
young because we have a number of specimens containing embryos. Other
than one unconfirmed specimen, there is no similar evidence for
plesiosaurs, which seems unlikely if their birthing strategy was the
same. It is also the case that we have very few juvenile, or simply
very small plesiosaurs, again unlike the case with ichthyosaurs in
which we find indivduals of widely different size from the same taxon.
A possible scenario is that whereas ichthyosaurs gave birth in the
open sea, plesiosaurs gave birth in sheltered nurseries, and only set
out into open water when they were well-grown. The evidence for this
is rather tenuous. I described a fauna of plesiosaurs and ichthyosaurs
from a site on the Jurassic/Cretaceous boundary in North Lincolnshire
which included very small specimens including a very small juvenile
limb bone. The palaeogeography of the site shows that it was a sandy
lagoon, probably in the estuary of a large river system. This is very
different from the facies in which we usually find plesiosaur remains.
RF
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Thanks...very informative. |
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