Ammonite Fossil

In 1829 John Phillips published his Illustrations of the Geology of Yorkshire; Part 1 The Yorkshire Coast, one of the earliest ‘local’ geological books in the world. 

Phillips was the nephew of William Smith, and in 1826 had been appointed first keeper of the Yorkshire Philosophical Society’s new museum in York, while his uncle had taken up residence in Scarborough where the Rotunda Museum was designed under his guidance.

In his book Phillips not only gave an account of the geology of our coast, but also illustrated many of its fossils, a significant number of which were named by him as new species. Some of the fossils were collected by Phillips, while others came from the cabinets of local collectors, especially the Scarborough-based William Bean and John Williamson. In 1829 Williamson became the first curator of the Rotunda Museum and by the time Phillips published a second edition of his work in 1835 Williamson had transferred his collection to the museum. 

One of his specimens was an ammonite collected at Ayton from limestones of Late Jurassic age which Phillips illustrated and named as a new species, Ammonites williamsoni, in honour of the collector. Almost 200 years later it’s still preserved in the collections of Scarborough Museums where it forms part of a small but scientifically very important collection of type and figured fossils: a type specimen being one on which a species name is based and is the ultimate reference specimen with which other material is compared. (The type specimen of man, Homo sapiens, is Carl Linnaeus, the 18th century Swedish naturalist who devised the system for naming genera and species). 

Phillips’ illustrations were rather sketchy and it is sometimes difficult to be certain whether a specimen recorded as the original of one of his figures has been correctly identified. But although his original figure of Ammonites williamsoni was drawn at an unusual angle, he faithfully showed a small breakage in the last whorl which is visible in our specimen, as our photograph shows. 

When Phillips published his work, almost all ammonite species were placed in a single ‘genus’, Ammonites. But as more and more species were described palaeontologists began to group them into more genera, and several thousand ammonite genera and sub-genera are now recognised. The type specimen of Ammonites williamsoni was refigured photographically by W.J. Arkell in 1945 as Peltoceras (Peltoceratoides) williamsoni, and that name is still used.