Archive for June 17th, 2016

Final day at The Natural History Museum … and one more Jurassic snuff-box

June 17th, 2016

1 Chandler snuff-box cutLondon, England — My last day in London was spent working on GSA abstracts and examining one last ferruginous oncoid (“snuff-box”) from the Jurassic (Bajocian) of southern England. Bob Chandler donated to the cause a large discoidal snuff-box. We cut it (cross-section through the center shown above) and revealed its intricate internal structure.

2 Chandler snuff-box nucleusThe typical limestone nucleus is smaller than I expected, but it still shows typical features such as bioerosion.

3 Snuff-box horn 061716This specimen has beautifully-developed “horns” around the periphery. They are made of laminae not connected to the central cortex. Paul Taylor suggested that they form when the snuff-box is no long being moved about. Nice specimen. Cassidy Jester (’17) will have much to figure out in her Independent Study focused on these objects.

I’ve had a great and productive time on this expedition to England. Thank you again to my amigos Tim Palmer and Paul Taylor, as well as John Whicher, Bob Chandler and Consuelo Sendino. Science marches on.

Addendum: This is the way I like my Tube stations — empty! Take me home, District Line to Paddington. Saturday, June 18, 5:08 a.m.

Fulham Broadway tube station at 0508

Wooster’s Fossils of the Week: Symbiotic interactions in the Silurian of Baltica

June 17th, 2016

EcclimadictyonThis week’s fossils are from work Olev Vinn (University of Tartu, Estonia) and I did last summer that is soon to appear in the journal Lethaia. (An early electronic version of the manuscript has been available since November.) After numerous smaller studies describing symbiotic relationships recorded in Silurian fossils in the paleocontinent Baltica, we wrote a summary paper under Olev’s leadership. All the images are take by Olev and in the paper itself. I love this kind of study because it is about fossils as living, interacting organisms, not just static sets of characteristics.

For example, the top image is of the stromatoporoid Ecclimadictyon astrolaxum (a kind of hard sponge) with embedded rugosan corals (Palaeophyllum, with arrows) from the Jaagarahu Formation (Sheinwoodian) exposed at Abula cliff, Saaremaa Island, Estonia. The stromatoporoid and corals were growing together, each having their particular needs met and maybe even enhanced by the other.
syringoporidThe network of holes in this stromatoporoid from the Paadla Formation (Ludfordian) of Katri cliff, Saaremaa, represent the corallites of a syringoporid coral. Again, the coral and sponge formed an intergrown association.
ChaetosalpinxThis is a thin-section view of what was likely a soft-bodied worm (represented by Chaetosalpinx sibiriensis, noted by a white arrow) embedded in the tabulate coral Paleofavosites cf. collatatus from the Muksha Subformation (Homerian), Bagovitsa A, Podolia, Ukraine. Again, the worm was embedded in the living tissues of the host.

We found 13 such symbiotic associations in the Silurian of Baltica. Most of these interactions involved large skeletal organisms like stromatoporoids and corals, which provided stable hosts for smaller sessile filter-feeders and micro-predators. This work is part of a larger study looking at evolutionary trends in symbiotic associations during the Paleozoic.

References:

Tapanila, L. 2005. Palaeoecology and diversity of endosymbionts in Palaeozoic marine invertebrates: trace fossil evidence. Lethaia 38: 89–99.

Vinn, O. and Wilson, M.A. 2016. Symbiotic interactions in the Silurian of Baltica. Lethaia 49: 413–420.

Vinn, O., Wilson, M.A. and Motus, M.-A. 2014. Symbiotic endobiont biofacies in the Silurian of Baltica. Palaeogeography, Palaeoclimatology, Palaeoecology 404: 24–29.