Astropolichnus CRIMES & ANDERSON, 1985
Astropolichnus hispanicus (CRIMES, LEGG, MARCOS & ARBOLEYA, 1977): p. 112; =Astropolithon hispanicus CRIMES, LEGG, MARCOS & ARBOLEYA, 1977: p. 112; subsequent designation by CRIMES & ANDERSON (1985): p. 314-315.
Cup-like traces, consisting of a raised rim (when preserved as convex hyporeliefs) with numerous unbranched radial ridges seperated by grooves and surrounding a circular area showing usually severed remains of a central axial cylinder. Less frequently, the complementary structures are preserved as concave epireliefs (PILLOLA et al., 1994: p. 259).
Derivation of name:
Unknown, probably as derivation from Astropolithon DAWSON (1878: p. 83) that was regarded as sand volcanoe by PICKERILL & HARRIS (1979).
A re-examination of Astropolithon hindii DAWSON, 1878 at its type locality by PICKERILL & HARRIS (1979) showed that the structures were positive features on the upper, rather than the lower, surface of the beds. Thus, PICKERILL & HARRIS (1979) concluded that Astropolithon hindii DAWSON, 1878 was infact produced as sand volcanoes by fluid flow. They therefore regarded Astropolithon hindii DAWSON, 1878 as pseudofossil. In contrast, Astropolithon hispanicus CRIMES, LEGG, MARCOS & ARBOLEYA, 1977 was accepted as biogenic structure (p. 1033). Therefore, CRIMES & ANDERSON (1985) erected Astropolichnus to include Astropolithon hispanicus and designated it as type ichnospecies..
Terrigeneous facies in shallow marine environments (PILLOLA et al., 1994).
Known Stratigraphic Range:
Lower Cambrian (Upper “Tommotian” - Lower “Atdabanian”; CRIMES, 1987; Base to middle part of the Upper “Ovetian”; PILLOLA et al., 1994)
Detailed information for each ichnospecies
- Astropolichnus hispanicus CRIMES, LEGG, MARCOS & ARBOLEYA, 1977
- Diagnosis: Astropolichnus with 30-48 radial ridges separated by narrow grooves and wide (transversally) circular area of the xial cylinder occupying about one third of the entire trace. Long radial ridges, of abput equal size, distally widening (emended after PILLOLA et al., 1994: p. 262).
- Orientation: Positive hypichnia.
- Morphological category (KNAUST, 2012): BUrrow, subvertical, unbranched, plug-shaped, passive fill, no lining.
- Ethological category: Domichnion (PILLOLA et al., 1994).
- Environment: Fully marine(?).
- Derivation of name: After the Latin name for (Spain = Hispania) where the first specimens originated (CRIMES et al., 1977).
- Types: Institute of Geological Sciences, London, Great Britain; Holotype Inventary-No.: IGS/FOR 3707; Paratypes Inventary-No.: IGS/FOR 3707 (second example on same block as holotype); further paratypes with inventary-numbers: IGS/FOR 3708-3711; University of Oviedo, Spain: AMC 1202, 1205-1208 & 1220.
- Type locality: Road-cut between Los Barrios de Luna and Mallo, N-Spain (locality 15, see map in CRIMES et al., 1977).
- Type horizon: Herrerķa Sandstone; Lower Cambrian.
- Geographical distribution: Normandy (France), Iberian Massif (Spain), Sardinia? (Italy), Newfoundland (Canada) PILLOLA et al., 1994.
- Remarks: During periods of high sedimentation rates equilibrated domichnia or fugichnia may occur (PILLOLA et al., 1994). Traces were usually constructed in argillaceous to silty, unconsolidated substrates and later passively filled with fine to coarse sand. As tracemakers organisms with a similar life-style as modern mud- or sand-dwelling sea anemones are assumed (PILLOLA et al., 1994). Small specimens are usually lacking which might be related to a free swimming behaviour in early life-stages (as also observed in modern cnidarians; PILLOLA et al., 1994).