As we walked along the beach between Sandsend and Whitby on Friday morning, I spotted this ammonite fossil embedded in the boulder clay cliff. The closely spaced ribs are almost straight, so that it reminded me of a section of reinforced hosepipe.
Dactylioceras was a slow swimming ammonite from the Early Jurassic. This looks like a fragment of the shell of Dactylioceras tenuicostatum, a common fossil found in the Whitby Mudstone Formation at locations such as Port Mulgrave.
The hollow chamber inside the shell has been filled with calcite crystals.
Hildoceras
Hildoceras, also from the Early Jurassic has sickle-shaped ribs and a groove along the triple-keeled groove along the outer edge of the shell.
Hildoceras features on the title page of my book Yorkshire Rock, a journey through time, which was published 25 years ago by the British Geological Survey (see link below).
There’s a folktale that they’re the fossilised remains of serpents, driven from the cliff top at Whitby by Abbess St Hilda.
Link
Yorkshire Rock, a journey through time at my website Willow Island Editions
Thanks Richard. Nice sketches and interesting little piece. I grew up in Whitby so fossil hunting was one of the things we used to do. I didn’t really know anything at the time but you can’t help but be intrigued at that age by all these petrified animals. The ammonite interior is no doubt Calcium Carbonate (CACO3) which is the crystallised calcium shell. As we know crystals e.g. diamonds, can be created articially these days by applying pressure and heat. See here:
https://www.instituteofmaking.org.uk/materials-library/material/calcite-crystal