BRULE: THE EARLIEST RECORD OF GREGARIOUS TETRAPOD BEHAVIOUR IN THE WORLD'S ONLY KNOWN WALCHIAN CONIFER FOSSIL FOREST

On the shore at Brule, Nova Scotia, a unique paleontological site provides an hitherto unavailable window on the terrestrial paleoecology of paleoequatorial Pangaea at the onset of the Permian Period. We here report on the results of eight years of investigative research at the site. Preserved within a redbed stratal sequence are 92 stump casts (d=8-81cm) and prostrate trees preserved to lengths of 15m amidst a monotypic foliar litter of Walchia branchlets, interpreted as an in situ stand of walchian conifers. Although ubiquitous in early Permian redbeds of paleotropical Pangea, Brule stands as the only known example in the world of a walchian conifer forest.

Impressed on every bedding surface of the pervasively dessication-cracked, mud-draped redbeds is a profusion of tetrapod footprints that we ascribe conservatively to the ichnotaxa Amphisauropus latus, Limnopus vagus, Gilmoreichnus brachydactylus, Dimetropus nicolasi, Dromopus agilis and Varanopus cf. microdactylus. The trackmakers of this cosmopolitan Euramerican ichnofauna of European affinity are inferred to represent cotylosaur reptiliomorphs, temnospondyl amphibians and pelycosaur reptiles. Trackways of Amphisauropus latus, Limnopus vagus and Gilmoreichnus brachydactylus demonstrate unequivocal and evocative evidence of gregarious behaviour, meeting criteria of impression, spacing, preferred direction (linear and non-linear)and simultaneous change in gait.

Invertebrate grazing traces and on discrete horizons the ostracod Carbonita scalpellus, branchiopod Leaia sp., large palaeopterid (dragonfly) insect wings and soft sediment deformation consistent with microbial mats contribute to the reconstruction of ephemeral flooding and subsequent exposure consistent with a dryland riverbed 'waterhole' treed by White's 'Children of Adversity' under a semiarid monsoonal climate.