Darriwilian Age

What happened during this time?

Flora

• The oldest known land plant macrofossils are known from this Age (13Jul2021)

• Bryophyte macrofossils from five different groups discovered at the Douglas Dam locality, Tennessee (Retallack 2019)

  • Hornworts(Casterlorum crispum), in the Leiosporocerotaceae: similar to the living Leiosporoceros dussii 

  • Liverworts

    • Thalloid liverwort (Cestites mirabilis) in the Marchantiaceae: similar to the living Marchantia polymorpha

    • Balloonwort (Janegraya sibylla), in the Sphaerocarpaceae: similar to the living Sphaerocarpus

  • Mosses

    • Peat moss (Dollyphyton boucotii), in the Sphagnales (Flatbergiaceae?):  similar to the living living Flatbergium

    • Harsh moss (Edwardsiphyton ovatum) in the Pottiales (Pottiaceae?): similar to the living Tortula leucostoma

Cryptospores

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

  • Oldest embryophytic spores have a lamellated wall structure of a single Hanadir Member monad (Taylor et al. 2017)

    • Homogeneous walls are characteristic of extant embryophyte sporoderm, which is actively secreted by a tapetum.

• This implies that these Ordovician cryptospores developed within a sporangium

• These Middle Ordovician sediments possess 8-10 species of meiospores 

  • 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

  • Several other possible meiospore types: 

    • Naked laevigate monads

    • Naked monads with pseudo-trilete mark (i.e. Imperfectotriletes)

    • Naked unfused dyads (i.e.Dyadospora),

    • Ornamented envelope enclosed dyads (i.e. Segestrespora)