The Ichnogenus Undichna, With Examples From The Permian Of The Falkland Islands

• Published in: Palaeontology
• Main Author: Trewin, Nigel H.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2000
• Subjects: Lion Island
• Online Access: http://dx.doi.org/10.1111/1475-4983.00158; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2F1475-4983.00158; https://onlinelibrary.wiley.com/doi/pdf/10.1111/1475-4983.00158

Abundant, well‐preserved and variable species of Undichna are described from the Permian of the Falkland Islands. The environment is considered to be non‐marine and the traces are associated with turbidite and rhythmite deposits. There are strong similarities between the Undichna and other ichnogenera of the Falkland Islands and those of the Eastern Cape Province of South Africa, thus strengthening the view that the missing eastern end of the Permian Karoo Basin is present in the Falklands. Undichna binaU. insolentia occur associated within glacially influenced rhythmite and turbidite facies of a non‐marine basin in the Cantera Formation, Camilla Creek, East Falkland. U. quina isp. nov. occurs on Sea Lion Island and is associated with thin (mm–cm scale) graded interbeds between thicker amalgamated sandstones in a sequence deposited by density currents derived from a delta feeding the same non‐marine basin. The elements that comprise Undichna traces are (1) single sinusoidal grooves, (2) paired sinusoidal grooves, (3) broad shallow grooves, (4) repeated arcuate imprints, (5) irregular grooves, (6) striated brush‐like imprints. A distinct, repeated morphology is only produced by a constant activity of the tracemaker (generally a fish). Irregular activity (e.g. acceleration, sharp turns) or current action produces non‐constant morphology, lacking the defining regularity of the ichnogenus Undichna. Such irregular forms can frequently be identified as a modified expression of a described ichnospecies, but morphologically do not fall within the definition of the ichnospecies. It is suggested that rather than create new names they should be referred to as ‘cf. Undichna isp.’ (irregular form).