Eocolius walkeri

Eocolius walkeri

Dyke & Waterhouse, 2001

Common name Enigmatic neoavian bird
Fossil group Birds
Order Neoaves incertae sedis
Family incertae sedis
Genus Eocolius
Taxonomic status Taxonomically Uncertain
Geological age Ypresian

Summary

Eocolius walkeri was originally described as a mousebird relative, but later anatomical work found that the characters needed to place it securely within Coliiformes are lacking. The current London Clay synthesis therefore treats it as a neoavian bird of uncertain ordinal position.

Its small body and flight apparatus show that it was a fully volant land bird, but a mousebird style climbing and feeding ecology should not be assumed. Insectivory or mixed feeding is possible for a small arboreal neoavian, yet the fossil evidence does not currently justify a more specific lifestyle reconstruction.

Quick Identification

Look for: an associated small bird skeleton or a very well preserved humerus and coracoid matching the type morphology. Do not identify it as a mousebird from size alone; the supracoracoid nerve foramen and humeral proportions are important specialist characters.

Diagnostic Features

  • The coracoid has a supracoracoid nerve foramen, unlike Archaeodromus.
  • The humeral dorsal tubercle is less elongate than in Archaeodromus.
  • The ventral supracondylar tubercle does not extend as far proximally as in Archaeodromus.
  • The distal humeral flexor process differs from the blunter Archaeodromus condition.
  • No unique character combination currently secures the species within Coliiformes.

Fossil Details

Preservation
Small hollow bones can be crushed or incomplete. Preservation of the coracoid foramina and humeral ends is crucial for useful comparison.

Similar Species

Recorded Fossil Sites

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

Last Reviewed
25 August 2026 Reviewed by Sam Harris