The star of Skinningrove

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A sandstone block from Skinningrove beach, bearing a specimen of the early Jurassic starfish (asteroid), Tropidaster pectinatus Forbes, 1850.

Our BEACH (Bold Earth/Art Cleveland Heritage) project is funded by the UK Science Festivals Network, with the aim of connecting Earth science researchers, artists, and local people to explore the rocks and fossils of Redcar & Cleveland, creatively.

We did pretty well at our Skinningrove event on Halloween, not least because one of the young people on our morning fossil hunt found an exceptionally rare fossil – a Jurassic starfish!

As I’ve written elsewhere, asteroids are amazing creatures, very infrequently fossilized. After a starfish dies, its body falls apart pretty quickly, and all its tiny bones (ossicles) disperse as seafloor particles. It needs to be buried rapidly to be preserved intact.

Tropidaster pectinatus, the combed keel-star

In the Early Jurassic rocks of the Yorkshire Coast, such as at Skinningrove, fossils of ophiuroids (brittle stars), such as Palaeocoma milleri, are found moderately often. Fossil starfish are not.

Indeed, despite having named three species of fossil starfish, I wasn’t sure what species this one was, although my mitigation is that the ancient asteroids I studied lived more than 200 million years before the Jurassic period even began.

Thankfully, my online fossil friends and some Google Scholar-searching enabled me to conclude that the Skinningrove star was Tropidaster pectinatus, or the combed keel-star.

Having been named by Edward Forbes in 1850, T. pectinatus was redescribed by palaeontologist Dan Blake in the 1990s. Dan interpreted it as a selective predator, somewhat closely related to the present-day Solasteridae, or sun-stars. The specimens from Dan’s paper were all from Gloucestershire.

More recently, Ben Thuy and colleagues recorded some echinoderms from the Early Jurassic of France, where a remarkable 70% of the asteroids were T. pectinatus. The only other starfish they identified was Plumaster (a species of which, shown below, is also known from the Yorkshire Coast), but apparently this is normal for the muddy Early Jurassic seas of western Europe:

“The complete dominance of Tropidaster and Plumaster in relatively shallow water clay facies of Pliensbachian age across western Europe (UK, France, Germany, Switzerland) is remarkable.”
(Thuy et al., 2011)

The holotype of Plumaster ophiuroides Wright, 1863, from the Pliensbachian (Lower Jurassic) of Robin Hood’s Bay or Skinningrove (photograph from Gale, 2011).

I find this very intriguing: this suggests there are only two types of Early Jurassic starfish that lived on Cleveland’s muddy seabeds – a five-rayed form (Tropidaster) and a multi-rayed form (Plumaster) – and both have been found as fossils in Skinningrove.

Where, then, does the multi-rayed ‘Solastermurchisoni fit in? The species was discovered in Robin Hood’s Bay, and named by William Crawford Williamson in 1836. J. F. Blake described a specimen from Huntcliff, near Saltburn, in 1887. Rather more recent discussions suggest Murchison’s sun-star is not uncommon in Pliensbachian strata at Saltburn, and probably belongs to Brachisolaster, but nobody has published this formally.

It’s all a bit mysterious. Clearly an asteroid-loving palaeontologist needs to do some taxonomic research, but don’t hold your breath for that to happen. Do, however, keep your eyes peeled next time you’re out on Skinningrove beach: you might find yourself seeing stars.

Earth scientist in York, fossilist across Yorkshire. Co-director of the Yorkshire Fossil Festival and palaeontologist for hire. Can be found twittering, facebooking, and instagramming as @fossiliam.