Re: Hey, What Bouncy Music!
erich orser said:
Nice link; if in fact those are cephalopod eggs (look kinda like cuttlefish eggs to me), I wonder what variety?
If those are cephalopod eggs then they are certainly nautiloid. None of the other cephalopod groups had evolved at that early date, not even the most primitive ammonoids. However, precisely what form of nautiloid is impossible to say as they were quite a diverse bunch of animals back in the Ordovician. Mastigograptus
appears to date from the Middle-Upper Ordovician, something like 470-443m.
I found the original reference to these if anyone fancies tracking it down (one might have to travel to Poland though!):
Kozlowski, R (1965) Oeufs fossiles des cephalopodes? Acta Palaeontologica Polonica 10: 3-9.
I'd be surprised if they were cephalopod eggs as according to Regis Chirat in his 2001 paper Anomalies of embryonic shell growth in post-Triassic Nautilida
no fossilised nautiloid eggs have ever been discovered. Unless Chirat missed these in his paper which looks extremely comprehensive, one can only assume they have been reinterpreted.
Denis Bates and Adam Urbanek The ultrastructure, development, and systematic position of the graptolite genus Mastigograptus 2002
In the above reference, a recent very detailed revision of Mastigograptus
(and far, far too complicated for me) there is a brief mention of the eggs but it does not add much about the eggs themselves. Graptolites, long extinct, were bizarre colonial invertebrates that consisted of branches and tubes containing individual animals linked to a single invidual which was often anchored via a disc to the sea bed or rocks, though other forms were probably planktonic floaters. Some looked like leaves, others disks, and still others like sticks or miniature fan corals (though they were probably Hemichordates and very distantly related to the vertebrates).
As for Mastiogograptus
, that appears to be a peculiar form of early sessile graptolite attached to the sea floor and appears to be somewhat problematic amongst those who study these things.