Hildoceras bifrons is extinct: End of Early Jurassic, approximately 175 million years ago.

Hildoceras bifrons is a common ammonoid fossil in the Alum Shales of northern England. It can be found in sea cliff exposures of the middle layers of the Whitby Mudstone Formation.

Shale and mudstone cliffs are susceptible to erosion and can therefore be threatened by coastal defence work.

Fossil collecting should only be carried out with the permission of the land owner.

Great care should be taken when fossil collecting. You should make sure you:

  • check tide times
  • are aware of the danger of rock falls
  • go as part of an organised group if possible
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Nekton is a free-swimming animals

Evolute and involute are geometrical terms relating to the shape of a curve

Lappets are spoon shaped extensions from the margin of the aperture

Arcuate is curved

Striae are fine lines of ornament

Ventro-lateral keels are ridges (keels) located on the sides of the venter

Tricarinate and bisulcate are two grooves separating the has three ridges (keels)of the venter.  

Venter is  the shell edge around the circumference