Protoconch

[Hajar]

That's very interesting Steve. So, the temperature control on embryo size is seen within a given species?

Thanks for that link Kevin, but unfortunately the link on the page (now here: http://www.naturkundemuseum-berlin.d...er&id=4&lang=1 ) goes to a different, 2005, paper.

[Architeuthoceras]

Do you think that we are talking eggs that are individually released into the water column, eggs (many) enclosed within some other structure (e.g. gelatinous egg mass) released into the water column that floats freely, or eggs that are individually (or collectively) attached to the substratum.

That question needs a lot more study Steve. This old thread mentions a lot of very young (? Embryonic) ammonoids mixed in with microgastropods and adult ammonoids. Several questions need to be answered; were these gathered together by hydrodynamic transport or were they in some kind of buried “gelatinous mass”, did all the ammonoids (and gastropods) lay their eggs at the same time and in the same place?

This thread mentions a small “clump” of small (? embryonic) ammonoids, an egg mass or coprolite?

And this thread mentions questionable cephalopod eggs attached to graptolites. (a link to the Kozlowski paper here)

Still, more questions than answers.

Sorry about the broken link Hajar

[hallucigenia]

OK, excellent -- further fuel for my consistent irritation with people using size to make species-level taxonomic distinctions! Grr.

Kevin, that is a truly amazing pile of protoconchs in that first thread. I'm inclined to think that whatever burial mechanism led to that kind of assemblage is also involved in Hajar's specimen in this thread -- I mean, I'd expect tiny ammonites to be eaten by other animals rather than being able to fall to the seafloor mostly-intact and in a consistent location! Clearly it's some kind of seafloor lag deposit, but intuitively it isn't obvious that you'd get all that many (tiny, presumably tasty) planktonic ceph larvae actually making it to the seafloor in the first place. Interesting! What is the matrix? -- it looks like sandstone in the photo?

[Architeuthoceras]

The matrix of the fossil bearing bed is calcarenite (shell fragments mostly, little or no quartz). Another bed, a few meters higher in the section, has the same fossils (without the small gastropods and ammonitellas) is a shell lag made up of broken bivalve shells in a siltstone matrix. both of these beds are in a soft fissile shale. The lower bed occurs sporadically over a very large area (a few hundred square kilometers) so there were probably a great number of small ammonoids in the area.

[Hajar]

Kevin, what do you know about the record of palaeo-oxygenation in your succession? Any evidence for mass kills associated with algal blooms (as discussed for the Oxford Clay by Wilby et al. 2008. Preserving the unpreservable: a lost world rediscovered at Christian Malford, UK. Geology Today, 24, 95-98)? Have you published on that ammonite bed?

This looks relevant: http://www.jstor.org/pss/3515210 It talks about a combination of biological (group spawning and mass mortality) and physical phenomena.

I enjoyed watching these baby cuttlefish: http://www.youtube.com/watch?v=TJhP0rzAiRo

I don’t see these accumulations of tiny protoconchs as lags (i.e. accumulations of larger/denser clasts with the smaller/less dense clasts winnowed out). (Here's a paper I should read: http://www3.interscience.wiley.com/j...TRY=1&SRETRY=0). Given their low densities and small grainsizes I would expect them to suspend easily under even weakly turbulent conditions, so they would better represent fallout from suspension. There is no preferred orientation of the tiny orthocones seen in the Hatch Formation specimen.

[Architeuthoceras]

A few papers on (very) similar fossils, mostly pertaining to the ontogeny of ammonoid shells.

Landman, Neil H., 1994, Exceptionally well-preserved ammonites from the Upper Cretaceous (Turonian-Santonian) of North America : implications for ammonite early ontogeny. American Museum novitates ; no. 3086

Landman, Neil H., 1987, Ontogeny of Upper Cretaceous (Turonian-Santonian) scaphitid ammonites from the Western Interior of North America : systematics, developmental patterns, and life history. Bulletin of the AMNH ; v. 185, article 2

Landman, Neil H., 1985, Preserved ammonitellas of Scaphites (Ammonoidea, Ancyloceratina). American Museum novitates ; no. 2815

Get a copy here (the 1987 paper is 25M)

[Hajar]

I've been corrected on the "clymeniid" with exposed protoconch above - it's a Manticoceras from the Frasnian (thank you Christian).

[Architeuthoceras]

(Here's a paper I should read: http://www3.interscience.wiley.com/j...1&SRETRY=0)

Hajar, have you got a ref for this link? I can't seem to get it to work

[Hajar]

nor does it work for me now (error message about cookies). I was browsing for recent papers on suspension criteria and biostratinomy and it was one of these.

[Hajar]

Another one of these Early Devonian (Emsian) goniatites from Morocco; Sellanarcestes, 14 mm from Bou Tchafine.

[DWhatley]

Hajar,
You get the coolest stuff, I always look forward to what you come up with even though I know nothing about the topic. By chance are you a museum curator?

[Hajar]

Thank you for that! No, this is just a hobby sparked by picking up that Paleogene coleoid earlier in the year. I’ve been finding these other specimens on ebay (amazing what shows up there).

[Hajar]

I just cleaned up the Sellanarcestes and took some more photos. Much more clearly seen now. The third photo is a stack of several images focussed at different depths (using CombineZP).

[Architeuthoceras]

You prep'd that well Hajar! The photos are great.

[Damien]

I had just a question ( photographic question ^^) , what kind of camera and lens can did you use to provide such pictures ?

[Hajar]

Thanks Kevin! My daughter loaned me a sewing needle, which now just passes through that first whorl perforation.

Greetings Damien. Nothing special (I’m no expert). It’s a Sony alpha350 (so a decent high resolution), with the standard 18-70mm lens, mounted on a tripod and brought up close to the eyepiece of a microscope (Euromex). I set focus to infinity, do the focussing with the microscope and use a remote shutter release to take the photo. Combine ZP (http://www.hadleyweb.pwp.blueyonder.co.uk/CZP/News.htm) is great for stacking a set of images focussed at different depths. I use it a lot for taking pictures of inclusions in amber (e.g. http://rusmithsgallery.fotopic.net/p55873010.html ; http://rusmithsgallery.fotopic.net/p55353431.html ).

[OB]

Hajar, you are an asset

[DWhatley]

... who always has cool stuff for the neophite to enjoy!

Now, to just get him interested in the living relatives ...

[Hajar]

Funny you should say that! Just yesterday I went into a shop (with my two young accomplices) to look at the gear for setting up a marine aquarium. After Christmas I think. We've seen some interesting cuttlefish (decorated with tubercles) in our local sea, but no octopus yet.

[DWhatley]

Ah, so you are not in the US I had a feeling you were getting hooked when you found the coconut octo.