Similarly, asteroids also produced wide and shallow striations perpendicular to the arm axis by tube-feet movement. The one backward arm erased the striations, and parallel fine striations remained in four arm depressions. When the ophiuroids resumed crawling, they raised their disc and four arms above the substratum and dragged one arm backward. The oral tube-feet produce fine, radial striations in the central depression. The basal-arm tube-feet produce well spaced, fine, parallel striations that are perpendicular to the arm axis. When ophiuroids stopped crawling, they buried themselves shallowly in the substratum, removing substratum under their arms and discs by using their tube-feet. To clarify the process of producing the striations in the trace fossil Asteriacites, we observed the behavior of living ophiuroids and asteroids in aquariums. These studies show that there are important differences in the morphology and in the production of asteroid and ophiuroid traces. The producers were observed to move from the resting position in the opposite direction of an ill-defined depression remained. The size and shape of trace fossils suggest that the producers may belong to an ophiuroid species found from the Late Jurassic around Ried. The resting traces of living ophiuroids (four well preserved depressions and an ill-defined one) were much wider than the producing animals. On the other hand, Asteriacites lumbricalis is interpreted to originate from ophiuroids based on the previous experimental study of living ophiuroids. Asteriacites quinquefolius was very similar to these resting traces of living asteroids, and its producer is suggested to be an asteroid. The producers were observed to move from the resting position in the direction of the indistinct depression. The sizes of traces were more or less the same as the producing animals. Similar shaped resting traces were also observed on the deep-sea floor. Consequently, a star-shaped like depression was left behind with four radiating wider and sub-triangular arm furrows tapering toward the tip and one straight or indistinct sub-triangular depression left by the bulldozing starfish. When it moved from the resting position, the three front arms of the moving asteroid bulldozed the substrate in front of these arms. scoparius buried itself shallowly, keeping its arms in a pentamerous symmetrical position. quinquefolius and to examine the producing process, resting traces of living asteroids, Astropecten scoparius and some deep-sea starfishes were observed in an aquarium and in situ, respectively. The large and small traces were assigned to Asteriacites quinquefolius and Asteriacites lumbricalis, respectively. If visibility is reduced while driving, motorists are urged to slow down, watch for tail lights ahead and be prepared to stop.Two different size star-shaped trace fossils are described from the Upper Jurassic Hienheim Formation in Germany. The federal weather agency said people should take care when walking or driving during the storm. "The wintry mix will taper off early Thursday morning to a risk of patchy freezing drizzle," Environment Canada said in the warning.Īs the snow and ice pellets accumulate on the ground, surfaces such as highways, roads, walkways and parking lots will become "icy, slippery and hazardous," Environment Canada added. The storm is expected to continue into early Thursday, but a "light wintry mix of precipitation" is also possible on Thursday afternoon and into the evening. In areas where ice pellets mix with freezing rain, there will likely be less accumulation, the agency said. They may mix or turn into freezing rain on Wednesday night. The federal weather agency said light snow and ice pellets are expected to become heavy at times late Wednesday afternoon and into the early evening. "There may be a significant impact on rush hour traffic in urban areas," Environment Canada said. There is a risk of freezing rain and light ice sticking to surfaces. Total amounts could be between 10 and 15 centimetres, Environment Canada said in an updated winter storm warning on Tuesday night. (Evan Mitsui/CBC - image credit)Ĭanada's federal weather agency is warning Torontonians to watch out for slippery conditions as a winter storm is expected to bring a mix of snow and ice pellets to the city starting late Wednesday afternoon. Commuters brave slippery conditions on the Don Valley Parkway in Toronto during a severe winter storm last year.
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