Glyptophidium polli

Glyptophidium polli

(Casier, 1946)

Common name Cusk-eel relative
Fossil group Bony Fish
Order Ophidiiformes
Family Ophidiidae
Genus Glyptophidium
Taxonomic status Taxonomically Uncertain
Geological age Ypresian

Summary

Glyptophidium polli was a cusk-eel relative known from London Clay otoliths. Ophidiids are predominantly bottom-associated marine fishes, and Eocene otolith assemblages in north-western Europe suggest that Glyptophidium formed part of a diverse soft-bottom demersal community. A diet of small benthic invertebrates and fishes is plausible from family ecology, but cannot be demonstrated directly from the otoliths.

The species is common enough in some Ypresian otolith assemblages to be useful palaeoecologically. Its ear stone resembles those of living Glyptophidium but differs in proportions and sulcus form, providing evidence that the lineage was already established in warm Eocene shelf seas.

Quick Identification

Look for: an elongate ophidiid sagittal otolith with a convex inner face, a long central sulcus and a comparatively narrow sulcus floor; the margins may be weakly crenulated and the outer face can show low tuberculate relief.

Diagnostic Features

  • Otolith is elongate with length clearly exceeding height.
  • Inner face is distinctly convex along the long axis.
  • Sulcus is long and relatively narrow compared with the overall otolith height.
  • Dorsal and ventral margins may carry fine crenulation rather than being completely smooth.
  • Outer face can show low irregular tubercles or relief, especially in well-preserved adult specimens.

Fossil Details

Preservation
London Clay otoliths may be chipped, rounded, dissolved or polished. Damage to the rostrum and antirostrum changes the outline, while abrasion of the inner face can weaken or erase the sulcus; either can make a species-level identification unsafe.

Recorded Fossil Sites

No fossil-site occurrences have yet been recorded for this species.

References

  • Lin, C.-H.; Steurbaut, E.; Nolf, D. (2024). Early Eocene fish otoliths from the eastern and southern USA. European Journal of Taxonomy, 935(1), 203–240 View reference
  • Schwarzhans, W. (2007). The otoliths from the Middle Eocene of Osteroden near Bramsche, north-western Germany. Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen, 244(3), 299–369 View reference
  • Steurbaut, E.; Nolf, D. (1988). Ypresian teleost otoliths from Belgium and northwestern France. Bulletin de la Société belge de Géologie, 97(3–4), 321–347 View reference
  • Stinton, F. C. (1966). Fish otoliths from the London Clay. Faune ichthyologique du London Clay, 404–464. British Museum (Natural History), London View reference
Last Reviewed
15 August 2026 Reviewed by Sam Harris