6 Jan 2015

Ammonite counterpart as cirri-pied-a-terre (repost from 2010).

This ammonite counterpart has made a rather splendid home for a colony of barnacles. What I love about this is the continuity; about 190 million years ago a 10 cm wide ammonite died and was fossilized in the mud of a warm, shallow Jurassic sea. What happened to the remains I don't know, I hope they are in an appreciative fossil collector's drawer, but the counterpart, the impression left by the ammonite's aragonite shell became home to a thriving community of barnacles, the creatures that Charles Darwin studied in enormous depth between 1846 and 1854.

This eight-year intellectual bodyswerve came at the height of Darwin's interest in 'the species question'; Darwin first privately wrote about natural selection in 1842*, his joint paper (written with Alfred Russel Wallace) was read to the Linnaean Society in 1858 and The Origin of Species was published in 1859. Some have suggested that Darwin's interest in this uncharismatic group of creatures was displacement activity (that he was scared to continue his evolutionary work), others that Darwin knew very well what he was doing, becoming intimately acquainted with a little-researched animal and using what he observed to support his burgeoning ideas about evolution by natural selection.

This apparently peaceful, sessile scene, with a dead ammonite's cast, a couple of hundred barnacles, seven limpets and a stray periwinkle is really one of fierce competition to survive.


Captain Shagrat said...

Great colours in this pic, haven't found any fossils myself on Runswick bay today but have a couple from previous excursions to Sandsend. Just had a quick look at Port Mulgrave those slippery steps gave us quite a turn.

Peter McGrath said...

Capt Shagrat may our paths have crossed on the beach today? Runswick beach has been pretty barren of late: we need a bit of rain and a few rockfalls. I'll post a pic of yesterday's fossil haul later. I have found a local sweet spot.

Captain Shagrat said...

I don't think our paths crossed as we were the only ones on the beach, plus I didn't spot 'The Snig' either ;-). Really nice clean beach apart from the strewn fireworks, I think some kids prob had a beach party the night b4.

Captain Shagrat said...

Damn I did mean to say 'The Smig'. Doh