Deltoidonautilus sowerbyi

Deltoidonautilus sowerbyi

(J. de C. Sowerby, 1843)

Common name Nautilus
Fossil group Molluscs
Order Nautilida
Family Hercoglossidae
Genus Deltoidonautilus
Taxonomic status Accepted
Geological age Ypresian

Representative Specimens

Selected reference specimens illustrating this species from different geological units and fossil sites.

Identification Examples

Choose a fossil site to view photographed reference specimens.

Summary

Deltoidonautilus sowerbyi was a streamlined chambered cephalopod that swam in the London Clay sea. Its tightly coiled shell acted as a buoyancy device, while the living animal occupied the final body chamber and used jet propulsion to move and manoeuvre through the water.

Like other nautiloids it was probably an opportunistic predator and scavenger, taking crustaceans, other small marine animals and carrion. Its comparatively narrow outer shell profile distinguishes it from the broader D. cassinianus and shows that several differently shaped nautiloids shared the same early Eocene seas.

Quick Identification

Look for: an involute Deltoidonautilus with a narrow to subangular outer profile, slightly convex flanks, a very small umbilicus and simple gently undulating sutures.

Diagnostic Features

  • Shell is planispiral, strongly involute and relatively streamlined.
  • Flanks are slightly convex and converge towards a narrow or subangular venter.
  • Umbilicus is very small because earlier whorls are strongly enclosed.
  • Septal sutures are simple and gently undulating rather than strongly zig-zag.
  • Outer shell profile is narrower and more peaked than the broad rounded whorl of Deltoidonautilus cassinianus.

Fossil Details

Typical size
About 50–70 mm; larger individuals are known.
Fossil material
Shell, Internal Mould / Cast
Preservation
Specimens are commonly internal moulds or incomplete phragmocones. The outer profile, suture pattern and undistorted whorl section are particularly important because crushing or loss of the venter can make the species difficult to separate from other Deltoidonautilus.

Similar Species

Recorded Fossil Sites

Synonyms & Previous Names

Nautilus sowerbyi; Angulithes sowerbyi

References

  • Edwards, F. E. (1849). A monograph of the Eocene Mollusca, or descriptions of shells from the older Tertiaries of England. Part I. Cephalopoda. Palaeontographical Society Monograph, 2, 1–56. Palaeontographical Society, London View reference
  • Hewitt, R. A. (2002). A review of the Early Eocene nautiloids of the London Clay Formation (upper division C to lowest division E) of south-east England, with particular reference to concretionary horizons and faunules in the offshore facies strata at Southend-on-Sea, Essex and in the adjacent cliffs of the Isle of Sheppey, Kent. Tertiary Research, 21(1–4), 39–50 View reference
Last Reviewed
26 August 2026 Reviewed by Sam Harris