PALAEOBIOLOGY OF THE CLIMACTICHNITES TRACEMAKER

Abstract

Trace fossils such as Climactichnites offer rare insights into the palaeobiology of Cambrian soft-bodied animals, especially those that inhabited emergent sand flats and are not known from body fossils. Analysis of field and museum Climactichnites, together with experiments on the preservation of similar modern trails, indicates that the tracemaker was an elongate, bilaterally symmetrical, dorsoventrally flattened, soft-bodied animal with a muscular foot. These characteristics are consistent with the tracemaker being a primitive mollusc or mollusc-like animal. Unlike most Neoproterozoic and Cambrian molluscs, the tracemaker could reach considerable size; at up to c. 69 cm long, it was one of the largest Cambrian animals of its time. When moving on the sediment surface, locomotion resulted from muscular waves generated along the sole of its flexible foot; the foot was extended and then clamped onto the substrate. Contraction of pedal muscles then pulled the body forward.Sedimentary structures associated with Climactichnites wilsoni, such as polygonal desiccation cracks, raindrop impressions, adhesion structures and gas escape structures demonstrate that the animal inhabited intermittently subaerially exposed environments. The tracemaker's method of locomotion is similar to that employed by modern intertidal gastropods, which make Climactichnites-like trails on exposed sand flats. However, these modern trails are not preserved because of erosion by wind, waves, tides and subsequent bioturbation. Abundant microbial sedimentary structures are associated with C. wilsoni, and together with low levels of vertical bioturbation, intimate that microbial binding may have mediated the preservation of these early mollusc trails.

The Tommotian phase of the Early Cambrian Agronomic Revolution in the carbonate mud environment of central Siberia

“…The wavy sole of the Siberian trace is of a kind known among the Cambrian trace fossils only in the Late Cambrian (Furongian) Climactichnites from various sites in North America (Getty ; Getty & Hagadorn , ). The surface trails there are associated with burrows and resting traces.…”

New Insights on the Impact of Tidal Currents on a Low-gradient, Semi-enclosed, Epicontinental Basin—the Curtis Formation, East-central Utah, USA

“…Subaqueous deposits are less frequent towards the eastern border of the study area, as the supratidal deposits become more common. Note that the uppermost aeolian sequence is also overlain by a thin sandstone crust that is typically structureless, yet shows evidence of local subaqueous reworking, and potential sand stromatolite structures, similar to those described by Getty and Hagadorn (2009). Whereas FA 7 is sharply overlain by the supratidal, rusty red to dark brown, evaporite-rich, sabkha deposits of FA 8 (Summerville Formation), the transition from the upper Curtis FA 6 sub-to supratidal strata into FA 8 supratidal environment is gradual (Fig.…”

Overprinted allocyclic processes by tidal resonance in an epicontinental basin: The Upper Jurassic Curtis Formation, east‐central Utah, USA

“…The traceable erosive truncations are supersurfaces (sensu Kocurek, 1988), implying that the Moab Member consists of five stacked aeolian sequences. Towards Duma Point (19), subtidal to intertidal deposits are commonly found overlying these supersurfaces, whereas supratidal deposits become more frequent towards the eastern and more continental part of the study area, linked with the development of local sand stromatolite structures similar to those described by Getty and Hagadorn (2009). These supratidal deposits are often associated with sparsely vegetated palaeosol horizons, as testified by the development of rhizoliths in the underlying strata.…”