[Non-Ceph] Bits 'n Pieces

[Hajar]

That’s very interesting. There’s a field workshop on this subject (“Recovery of ecosystems after the Permian-Triassic mass extinction”) here in Muscat later this month: http://www.igcp572.segs.uwa.edu.au/node/246

I came across these monster (see lense cap for scale) megalodont bivalves from later in the Triassic the day before yesterday (I was looking for prehistoric rock art near the town of Al Hamra).

 

[Architeuthoceras]

A lot of work being done at outcrops of the Permian-Triassic Transition right now. I dont think our rocks preserve the boundary exactly, but the fossils will tell when we finish our study.

Those bivalves may be part of the Lazarus Taxa (I will have to check), forms found in the Permian and later Triassic, with a gap in the fossil record, much like our gastropods with only a micro-fauna found (usually ) in the Early Triassic. A few micro bivalves were found to connect the Lazarus Gap in a few forms of Triassic bivalves.

 

[Hajar]

"Ammonoids make flash recovery": Flash Recovery Of Ammonoids After Most Massive Extinction Of All Time

 

[Hajar]

Two talks I heard yesterday were relevant to giant bivalves and "Lazarus" stories.

Yukio Isozaki talked about gigantism occurring during times of warm tropical seas and ending during cooling phases (e.g. end-Guadalupian). He mentioned that gigantism in bivalves has occurred several times: Siluro-Devonian (Megalodont 1), Permian (Alatoconchidae), Triassic-Early Jurassic (Megalodont 2) and Jurassic-Cretaceous (rudists). He also showed a monster modern giant clam.

Michael Hautman described a Late Griesbachian (Early Triassic) fauna of 16 species of small molluscs (biggest adult bivalve was 15 mm), including Early Triassic Lazarus taxa. He thinks that "lazarus" taxa have been simply overlooked due to their miniaturisation in the Early Triassic.

 

[Architeuthoceras]

Those sound like some good talks, wish I could have heard them.

Perhaps they have been overlooked because of miniaturization, or perhaps there is just a collection bias (they just haven't been found yet), and perhaps there were sanctuaries around the globe where some of these forms survived in a large size (again, just not found yet).

 

[DWhatley]

Could you enlighten the ignorant? The only Lazarus I am familiar with is the long lived and reappearing character in Heinlein's works who was a member of a family that was extemely long lived but hid the fact by "dieing/disappearing" and then reappearing somewhere else so that his age was not obvious.

 

[Architeuthoceras]

Lazarus taxa are named after that Lazarus D. They are forms that are quite common before a mass extinction and then usually re-appear in rocks a few million years after the extinction event, leaving a gap in the fossil record. Lazarus gaps can sometimes be filled by looking in "Lilliput effect" faunas (very small forms, usually found in rocks that were deposited during and/or right after a mass extinction event). New fossils and fossiliferous rocks are always being found, so these Lazarus gaps and Lilliput effect faunas can sometimes be confirmed or refuted.

 

[DWhatley]

Thanks Kevin, glad I was on the right track and not off in left field somewhere as I try to follow along a little.

 

[Architeuthoceras]

Gullivers and Lilliputians. The M in DIME is about 2.5mm wide. Most Early Triassic gastropods studied before we found the "Giants", were these itty bitty ones.

 

[~Flighty~]

Very interesting stuff! I took my kids out fossil hunting near Austin, Texas a while ago and wish I had a little more information to give them about the shells they were finding. I had a hard time even finding out when exactly that part of Texas was ocean. Pretty sad when a quick google search turns up more references to a magical flood a few thousand years ago as a source of all that limestone. My son wrote a little blog post with some pictures at the bottom of this page Teach Reason
~Cindy~

 

[Architeuthoceras]

to TONMO Cindy. Nice gastropods and bivalve fossils you've found, keep looking, there should be some ammonites around there.

 

[DWhatley]

What a terrific use for a blog. Go Dad!

 

[~Flighty~]

Mom

 

[DWhatley]

Ah, you are the one HOLDING the camera (MY JOB as well) !

 

[Terri]

This months National Geographic has a great article on whale evolution! ngm.nationalgeographic.com/2010/whale-evolution/mueller-text