Re: Australian trackways

["P.L.Manning" <P.L.Manning@sheffield.ac.uk>]

I must say that I have only heard that the tracks are from the 
Silurian, but am waiting further information.

 //  I've heard that they're the oldest
//terrestrial trackways yet found,but also attributed to Eurypterids.I
//find this a little hard to believe.Eurypterids aren't known to be
//amphibious,are they?

Yes . Research which I have carried out on the Respiratory system of 
eurypterids (See Manning and Dunlop, 1995, Palaeontology, Nex issue) 
does indicate that the Gill tracts (Kiemenplatten) of eurypterids 
could function as an accessory lung, similar to the highly 
vascularised areas of the branchial chambers of land crabs (such as 
pseudothelpusa). The true gills of euypterids, housed in the 'gill 
pouch', between the blattfusse and true sternite, have only just been 
discovered (Manning and Dunlop, 1995), leaving the Kiemenplatten 
available for aerial respiration, albeit only short excursions onto 
land. Subaerial tracks for eurypterids were also described by Hanken 
and Stormer (1975), showing an in-phase lurching gait, which left an 
impression of the metastoma, coxa and gnathobases. The biggest 
problem of terrestrialization for eurypterids was their size. There 
are certain biomechanical restraints of having a cuticular 
exoskeleton, meaning that only the smaller (less than 50 cm long) may 
have had a chance of 'crawling' onto land.


 //And this "three foot long centipede",any species
//names yet?

I would hazzard a guess that these beasties belong to the 
Arthropleurida ????

//   Further,are there any North American Ordovician Eurypterids? I always
//associated them with the Silurian!//

The only Ordovician eurypterids that I have had a chance to play with 
were from the Soom Shale, Table Mountain Formation, South Africa. The 
eurypterids resembled a Eurypterus-type body plan. Interestingly 
they also exhibited respiratory organs, however the preservation 
allowed little in the way of interpretation of these structures, 
other than the fact that they were there !!!!

I must return to tracking dinosaurs befor my supervisors catch me 
discussing.
Best Wishes to all
Phillip L. Manning
Dinosaur Track Research Unit
University of Sheffield
UK