Abdounia beaugei

Abdounia beaugei

Arambourg, 1935

Common Name: Requiem shark

Fossil Group: Sharks & Rays
Order: Carcharhiniformes
Family: Carcharinidae
Genus: Abdounia

Summary

Abdounia beaugei is a small fossil carcharhiniform shark known principally from isolated teeth. The most useful identification feature is the combination of a relatively slender, pointed central cusp with small lateral cusplets. Tooth shape changes markedly along the jaw: anterior teeth are taller and more upright, whereas teeth farther towards the side of the jaw become broader and increasingly inclined. Modern descriptions particularly emphasise the development of two pairs of lateral cusplets in lateral teeth, with the outer pair smaller than the inner pair; this is one of the most useful distinctions from Abdounia minutissima.

The crown of A. beaugei is generally smooth or only weakly ornamented, the cutting edges are smooth rather than serrated, and the root is divided into two lobes by a central nutritive groove. Importantly, a pronounced labial crown overhang should not be regarded as characteristic of A. beaugei: detailed descriptions report the crown passing into the root without a strong overhang.

For British material, A. beaugei is securely documented from the Ypresian London Clay Formation, including a museum specimen from the Sheppey Member at Cliff Reach, Burnham-on-Crouch, Essex. Casier’s major monograph on the London Clay also forms part of the established literature for the species.

Geological Age & Range Notes

Late Palaeocene–Middle Eocene, securely recorded from the Thanetian, Ypresian and Lutetian; some published assignments extend younger, but later Eocene records require caution because material formerly referred to A. beaugei has sometimes been reassigned to other Abdounia species

Fossil Material

Tooth

Known Localities

Diagnostic Features

  • The teeth are small, usually only a few millimetres across.
  • The centre of the tooth has a tall, narrow and sharply pointed main point.
  • Teeth from the front of the mouth are generally upright and fairly symmetrical.
  • Teeth from farther around the side of the mouth become broader and more uneven, with the main point leaning towards one side.
  • On either side of the main point are much smaller pointed side teeth, known as cusplets.
  • Teeth from near the front of the mouth usually have one small side point on each side of the main point.
  • Well developed teeth from the side of the mouth usually have two small side points on each side. The inner pair is noticeably larger than the outer pair.
  • The tiny outer pair can be very small and easily broken off, so damaged teeth may appear to have only one pair.
  • The side points are usually triangular and sharply pointed, with the larger pair sitting quite close to the main point.
  • The surface of the tooth is generally smooth or only very lightly lined near the bottom of the crown. Strong grooves or heavy decoration would be unusual.
  • All of the cutting edges are smooth and have no serrations.
  • The root spreads out into two separate lobes, one extending beneath each side of the crown.
  • Looking at the inside of the root, there is normally a groove running down the middle between the two root lobes.
  • The crown flows fairly smoothly into the root and normally does not form a large projecting shelf or lip over the front of it.

Identification Notes

Abdounia beaugei is best recognised by the combination of a slender pointed main tooth surrounded by several much smaller side points.

For a collector, one of the best specimens for identification is a complete tooth from the side of the jaw.

A typical lateral tooth should show:

one tall pointed central cusp + two smaller points on each side + a mostly smooth crown + smooth cutting edges + a two-lobed root.

The small outer pair of side points is particularly important. A complete lateral A. beaugei will normally have two points on each side of the main cusp, with the outer pair noticeably smaller than the inner pair.

However, these outer points are tiny and fragile. They are often worn down or broken away during fossilisation or collecting. Always look closely at the edge of the tooth before deciding that a second pair was never present.

Teeth can look very different

The shape of A. beaugei teeth changes depending on where they originally sat in the shark’s mouth.

Teeth near the front are generally:

taller and narrower
more upright
more symmetrical
usually equipped with one obvious pair of side points

Teeth farther around the side of the mouth become:

broader
more uneven in shape
increasingly leaning towards one side
more likely to show two pairs of side points

Because of this, two teeth belonging to the same species can initially look surprisingly different.

Worn or broken teeth

Damaged specimens should be treated cautiously.

If the outer side points are missing, a lateral A. beaugei may look like another species of Abdounia. Look closely for:

  • a small broken surface where another point may originally have been
  • an unusually flat or abrupt edge
  • differences between the two sides of the tooth

If too much of the tooth is missing to see the arrangement of the side points clearly, it is safer to record it as Abdounia sp. or Abdounia cf. beaugei rather than forcing a species identification.

Quick identification

A strong Abdounia beaugei candidate should have:

a small tooth + slender central point + small triangular side points + usually two pairs on lateral teeth + smooth cutting edges + a mostly smooth crown + a divided two-lobed root.

The two pairs of side points on a complete lateral tooth are one of the most useful features for separating A. beaugei from similar Abdounia species.