Katian Stage

Biological

• These Ordovician sediments possess 15 species of miospores 

  • Naked laevigate monads; naked fused dyads (i.e. Pseudodyadospora); naked fused tetrads (i.e. Tetrahedraletes); naked unfused tetrads (i.e. Stegambiquadrella); smooth envelope enclosed dyads (i.e. Segestrespora); envelope enclosed ornamented tetrads; naked unfused dyads (i.e.Dyadospora); ornamented envelope enclosed dyads (i.e. Segestrespora); smooth envelope enclosed tetrads (i.e. Velatitetras); ornamented envelope enclosed tetrads (i.e. Velatitetras); envelope enclosed monads (i.e. Sphaerasaccus)

• Many are bryophyte-like spores found in these Late Ordovician sediments

  • Fossil evidence for sporophytes with in situ spores from Oman at 450 Ma (Wellman et al., 2003)

• Macrofossils of plants are found as smooth tubes, similar to hydroids.

• Spores from the Lindegård Mudstone (late Katian–early Hirnantian) represent the earliest record of early land plant spores from Sweden and possibly also from Baltica (Badawy et al., 2014)

  • Implies that land plants had migrated to the palaeocontinent Baltica by at least the Late Ordovician.

• This discovery reinforces the earlier suggestion that the migration of land plants from northern Gondwana to Baltica in the Late Ordovician was facilitated by the northward migration of Avalonia, which is evidenced by the co-occurrence of reworked, Early–Middle Ordovician acritarchs, possibly suggesting an Avalonian provenance in a foreland basin system.

• Radiolarians radiate during this time