Macaronichnus Clifton and Thompson, 1978

DESCRIPTION: Densely packed, thin subvertical to subhorizontal cylindrical smooth-sided burrows with circular cross section. The diameters range from 1 to 5 mm; some up to 1 cm diameter. Longitudinally sinuous, never branch, but interpenetrations are common. May be meniscate.

BEHAVIOR(S): Deposit feeder (fodinichnia) that largely sustains itself on bacteria and organic matter on the surface of sand grains, which are ingested during locomotion.

ENVIRONMENTAL SETTINGS: Shallow marine nearshore, high-energy sandy environments; intertidal and shallow subtidal deposits.

POSSIBLE TRACEMAKERS: Polychaete worms (Ophelia; bristle worms).

GEOLOGIC RANGE: Cambrian-recent.

ADDITIONAL REFERENCES:

REMARKS: Smaller diameter examples follow sedimentary bedding features; some are lined by dark-colored heavy minerals produced by selective feeding; sometimes referred to as cryptobioturbation.

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