Brittle Star

What do the legs point to? 

These two brittle stars came from the ‘Starfish Bed’ between Eype and Seatown. The more complete one (top left) has three legs pointing or trailing in one direction. This suggests that there was a current flowing across the sea floor when these animals were buried.  You can see that the other specimen has three legs trailing in the opposite direction – but both brittlestars are broadly aligned to a current which, in this case, would have been running from bottom left to top right. Perhaps therefore, it’s a matter of chance as to how many legs end up pointing into, or away from, the current.

It has been speculated that a storm, or even a tsunami, smothered a whole community of brittle stars in a single event, capturing a moment in time about 180 million years ago.

There are also exceptions to the rule and some brittle stars are preserved with little alignment of the legs. Occasionally they have four legs trailing and one pointing in the opposite direction. Brittle stars today can move across the sea bed with their legs arranged in that way.

The starfish bed is typical of many features in geology that can offer different, and sometimes even contradictory, evidence. This makes it a challenge for geologists to understand and interpret past environments.

Find out more about brittle stars on the echinoderms page.



Common name

Brittle Star

Scientific name

Palaeocoma egertoni

Type

Echinoderms > Starfish


Strata

Starfish Bed

Time period

Lower Jurassic

Age

180 million years

Where found

Seatown, Eype

Found by

Dave Halvkin

Museum

Bridport Museum

Accession number

BRPMG 10802