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Bison
Wormy wrote:
Look like neuropteris to me...theres a few cracking spots inland around Durham city where you can find whole fronds.


Sadly I've yet to locate any of these spots. As a youngster I remember playing on the spoil heaps around Stanley and finding spectacular plant fossils. Those specimens, like the pit heaps (landscaped now) are long gone. Sigh...
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Bison
Found today on the Durham Coast. Just a few bits of leaf litter (Neuropteris?), but a close look shows some tiny spirals which I suspect to be microconchids. Nothing spectacular, but interesting that the leaves had been lying in water long enough to be colonized by another organism?IMG_9363-1.jpg 
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acutipuerilis

That is nice. I've seen microconchids on some plant material, but normally more obviously robust things. This just goes to show how long these leaves stayed around without decaying...
http://oldasthehills.proboards.com/index.cgi (For when you can't get enough trilobites, sponges, and squidgy blobs...)
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Asterixx
Hi,

microconchids are apparently quite frequently found on the leaves of ferns and related plants. See for example this 1966 paper about a seed fern from the permian of Texas:

http://pubs.usgs.gov/pp/0523e/report.pdf

The relevant pages are 11 - 13 and include a wide ranging discussion.

Interestingly, the author suggests that the microconchids might be freshwater - not marine - and that they settled and grew on the living plant.

A very nice little find - thanks for posting !

Brian
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Wormy
Look like neuropteris to me...theres a few cracking spots inland around Durham city where you can find whole fronds.
I aint got time to bleed!
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acutipuerilis

Asterixx wrote:
Hi,

microconchids are apparently quite frequently found on the leaves of ferns and related plants. See for example this 1966 paper about a seed fern from the permian of Texas:

http://pubs.usgs.gov/pp/0523e/report.pdf

The relevant pages are 11 - 13 and include a wide ranging discussion.

Interestingly, the author suggests that the microconchids might be freshwater - not marine - and that they settled and grew on the living plant.

A very nice little find - thanks for posting !

Brian

That would explain it... but the earliest spirorboid microconchids are certainly marine, since we've got them on nautiloids in the Llanfawr Lagerstatte. It's not many groups that adapted to both, and if microconchids managed it then it practically rules out some phyla on physiological grounds. Interesting...

http://oldasthehills.proboards.com/index.cgi (For when you can't get enough trilobites, sponges, and squidgy blobs...)
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Asterixx
How about a compromise - an estuarine / brackish environment ?!  A few living ferns are quite tolerant of salt.

Brian
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Asterixx
Hi,,

I just came across this:
http://www.sciencedirect.com/science/article/pii/S001669951200068X

Invasion of freshwater and variable marginal marine habitats by microconchid tubeworms ƒ¢¢â€š¬¢â‚¬Å“ an evolutionary perspective

Abstract:

Microconchids are an extinct group of Spirorbis-like
tentaculitoid tubeworms that dwelled in a variety of aquatic
environments, ranging from normal marine, through brackish and
hypersaline, to freshwater. An analysis of published microconchid
occurrences focusing on their ecology and palaeoenvironmental
distribution through geological time is conducted in order to establish
the timing of microconchid colonization of freshwater and marginal
marine habitats. Microconchids originated during the Late Ordovician in
shallow shelf, normal marine environments where they thrived until their
extinction at the end of the Middle Jurassic (latest Bathonian).
Microconchid colonization of marginal marine brackish habitats seems to
have started already by the Early Silurian (Wenlock). The freshwater
habitats were invaded by microconchids in the Early Devonian, nearly
simultaneously in several regions (Germany, Spitsbergen, USA). Since
shallow marginal marine and freshwater habitats are more unstable,
especially in terms of temperature and salinity fluctuations, as well as
prone to desiccation, than normal marine, shelf environments, the
drivers of the colonization of these habitats by microconchids are
currently incompletely understood. We hypothesize that by colonizing
such environments, microconchids gained access to abundant food
resources in the form of suspended organic matter delivered from the
land by rivers and streams. These, combined with their biology, enabled
microconchids to reproduce fast and in large numbers. Microconchids are
considered to have gone extinct by the end of the Middle Jurassic (Late
Bathonian). Their youngest occurrence in freshwater environments is
known from the Late Triassic and it is currently not known whether
microconchids continued to occupy such habitats later on in the
Jurassic. All the Middle Jurassic records of microconchids come from
marine settings. Thus, more focused research on Jurassic brackish and
freshwater deposits worldwide is needed to check whether they may have
thrived in such environments at some locations, until their hypothesized
extinction.


.... altogether, these minispirally things turn out to be rather interesting !

Brian


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