Squalus minor is an extinct member of the dogfish shark family and its teeth have the characteristic low, sideways pointing appearance seen in Squalus.

At first glance they can look rather unlike a conventional shark tooth because the point does not rise vertically from the middle. Instead, the crown appears to have been pushed over towards one side.

A good Squalus minor tooth should therefore have:

a low broad crown + sideways pointing main point + rounded heel behind it + completely smooth edges + broad central projection extending down the front of the root.

Look at the central projection

One of the easiest features to check is the front of the tooth.

In the centre of the crown is a prominent V-shaped or rounded projection that extends down across the root.

On a complete S. minor tooth this can reach below the bottom edge of the root.

This feature is characteristic of Squalus teeth and is especially useful when dealing with very small specimens where the shape of the main point may be difficult to see.

Look at the rounded heel

Behind the main point is a high, smoothly rounded heel.

It should not look like a separate sharp side point. Instead, the cutting edge drops from the main point into a small notch and then rises slightly into a broad rounded area.

The combination of a slightly curved main point and high rounded heel was one of the features used by Leriche to characterise S. minor.

Check for serrations

The cutting edges of Squalus minor should normally be smooth.

This is useful when separating it from some similar fossil dogfish teeth.

Squalus minor vs Squalus orpiensis

These two Palaeogene dogfish sharks can occur in deposits of similar age and their teeth can look quite similar.

Squalus minor generally has:

• smooth cutting edges
• a comparatively compact crown
• a rounded rear heel
• a smooth base to the crown

Squalus orpiensis generally has:

• a longer and more stretched-out tooth
• cutting edges that can show fine serrations
• fine wrinkles or crenulations along the inner base of the crown
• larger openings in parts of the root

These differences are useful, particularly when complete teeth from the same deposit can be compared.

Squalus smithi

The name Squalus smithi appears in older literature.

Modern work considers S. smithi to be a younger synonym of Squalus minor because the main distinction originally used between them was tooth size, and size alone is not considered reliable enough to separate the two species.

Species identification needs some caution

There is an important limitation with Squalus minor.

The teeth of living species of Squalus can be extremely difficult to distinguish from one another, even when complete sets of teeth are available. Fossil species are normally known only from isolated teeth.

Researchers have therefore cautioned that fossils currently grouped under the name Squalus minor may not necessarily represent a single biological species.

For the identification database, a well preserved tooth from an appropriate Palaeocene or Eocene deposit showing the classic S. minor morphology can reasonably be identified as Squalus minor.

If the crown is badly worn, the root is missing, or the important features cannot be seen clearly, Squalus sp. or Squalus cf. minor would be safer.

Quick recognition

Look for:

tiny tooth + wider than tall + strongly sideways pointing cusp + rounded heel + smooth cutting edges + central V-shaped projection over the root.