New occurrences of Ichniotherium and Striatichnium from the Lower Permian Kildare Capes Formation, Prince Edward Island, Canada: palaeoenvironmental and biostratigraphic implications


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Abstract:  Tracks and trackways of the vertebrate ichnotaxon Ichniotherium sphaerodactylum and a trace of the invertebrate ichnotaxon Striatichnium bromackerense are described for the first time in association outside of Europe. The tracks are identified as I. sphaerodactylum based on their characteristic rounded digit ends, the ovoid sole-pad of the pedal imprint and the increase in digit lengths from digits I–IV, and the invertebrate trace is identifiable as S. bromackerense based on the band-like systems of distally bifurcated striae. The tracks of I. sphaerodactylum are the largest known to date and represent rare evidence of large-bodied terrestrial vertebrates in the Kildare Capes Formation of Prince Edward Island, Canada. Morphometric differences between ichnospecies of Ichniotherium and other ichnospecies previously collected from Prince Edward Island are examined in a multivariate analysis, and results suggest that the distance between the manus and pes of the same imprint pair, the width of pace and the length of certain digits is useful for species identification. The association between I. sphaerodactylum and S. bromackerense was previously known only from the Bromacker quarry, Tambach Formation, Germany, which is interpreted as a seasonally dry, semi-arid upland environment. The co-occurrence of these traces suggests that the Eldon locality of Prince Edward Island is similar in depositional environment to the Bromacker quarry in Germany, and allows for comparison of these two localities for the first time. As diadectids are thought to be the trackmakers of Ichniotherium, the Eldon locality of the Kildare Capes Formation may, with further work, be considered as another example of the rare, herbivore-dominated palaeoenvironment, which is generally uncharacteristic of the Early Permian of North America.