Ichnotaxonomy and Behavioral Implications of Lingulide-Derived Trace Fossils from the Lower and Middle Triassic of Western Canada

Lingulide brachiopods have been important components of Phanerozoic marine ecosystems since the Paleozoic. Although lingulides developed an infaunal lifestyle early in their history, trace fossils attributed to their burrowing behavior have not been commonly recognized. Lingulichnus verticalis Hakes, the sole described lingulide-derived trace fossil, has been interpreted as a lingulide dwelling trace. Although modern lingulides engage in a wide variety of infaunal activities, including maintaining position during sediment aggradation (escape from burial) and reburial after erosional exhumation, ichnofossils reflecting these activities have not been previously recognized. Lingulide brachiopods and trace fossils reflecting the full spectrum of lingulide burrowing behavior (described herein) are common in Lower and Middle Triassic strata of western Canada. The description of Lingulichnus verticalis is revised to include spreitenate as well as simple vertical structures. L. inclinatus isp. nov. includes obliquely oriented forms. L. hamatus isp. nov. is described to include J- and U-shaped forms. Lingulichnus in the Triassic of western Canada occur in proximal offshore, offshore transition, lower shoreface, deltaic, estuarine and intertidal flat settings. The paucity of reports of Lingulichnus in the trace-fossil literature (and absence of reports of Lingulichnus in post-Triassic strata) is likely related as much to difficulties in recognizing these forms as it is to low preservation potential.