sorby69's picture

P1060402

Observed: 10th April 2011 By: sorby69
P1060402
Description:

My sons and I dug a couple of small holes in our field near Offa's Dyke and within 20 minutes of starting my eldest son Ben found this rock (pictured). It is about 15cm long by 11cm across and 2.5cm thick. The other side is smooth with no visible fossils. We would love to know more about it please.

Identifications
Species interactions

No interactions present.

Comments

anonymous spotter's picture

A good starting point -

If the identification is correct, is a general article at:
http://en.wikipedia.org/wiki/Priapulida

sorby69's picture

Thanks Roger - though I'm

Thanks Roger - though I'm even less certain it's Priapulida now!

Mike Kendall's picture

How do we know its a priapulid?

When there are so many species (including annelids, crustaceans, sipunculans) apart from Priapula that create this sort of burrow, which characteristics identify it to this particular phylum?

Mike Kendall

sorby69's picture

Hi Mike - I'm not sure

Hi Mike - I'm not sure they're priapulid - hence my 'confidence' rating. I'd have gone for a lower confidence rating if there was one ;-)

Can you advise me what characteristics I should be looking for please?

Thanks for taking the time to reply.

Rob

p.s. I should state my level of competence & understanding in these matters - zero! :-) I'm looking forward to learning and hope you'll forgive my general ignorance :-)

Mike Kendall's picture

I don't know....thats why I asked

My main interest is annelids and I can think of many worm species in the modern ocean that would leave such traces behind the as they burrow through muddy sediments. Annelids are the most common element of the burrowing fauna in contemporary shallow oceans worldwide. On the other hand, priapulids are usually quite rare.

Hence my question; what makes these burrows so different that thay are labelled priapulid rather than the currently more common taxon when neither (with rare exceptions)leaves a macroscopic trace of the body itself, just an infilled tube? The only relaible method of separating burrows of the two taxa I know of is by the feeding marks around the burrow opening but I doubt these are well preserved in the geological record.

I guess that if you are a non specialist you picked up the ID from a geological text...but I still don't understand how that author reached the ID and would love to be educated. The reason for the interest is that for the rapid biological survey of the intertidal I have spent some time compiling field guides to tracks and traces. I was worried I'd missed out somewhere.

Strange folks geologists

Mike Kendall

sorby69's picture

I've tried to retrace my

I've tried to retrace my 'research' steps which led me to arrive at the suggested identification but am drawing a blank. Perhaps I should remove the identification and change it to something more general. Mike - from the the photo, are you able to say what it is (however general/abstract) so that I can classify it accurately please?

Thanks
Rob

Mike Kendall's picture

Probably the safest bet is .....

Worm burrows; I nearly wrote tubes, but these look like temporary structures rather than a permanently inhabited tube which normally has a rather more definite shape. Your specimen has the sort of structure we find if we put resin into a ragworm burrow.

The length and continuous nature of the burrow suggests its probably not a crustacean, unless the burrows are quite wide, >5 or 6 mm. In current warm waters there are a whole raft of burrowing shrimps whose ancestors have left behind substantial fossil records.

Mike Kendall

sorby69's picture

Thank you Mike - I've added

Thank you Mike - I've added the identity 'Worm Burrows'. I'll try and upload some better photos in case there are any features that might narrow down its identity further.
Thanks again,
Rob