Macerations of Middle Ordovician (Llanvirnian) shales from Saudi Arabi
a yield an assemblage of spores of probable land plants (cryptospores)
, acritarchs, and chitinozoa, The production of sporopollenin-containi
ng, sporelike tetrads is considered a fundamental character of the emb
ryophytes, because no extant algae produce spores of this type. No tri
lete spores were found at this horizon, reinforcing previous assertion
s that obligate meiotic tetrads predate the earliest trilete spores, S
poromorph tetrads and dyads, in conjunction with cuticlelike fragments
, were probably derived from terrestrial plants at a bryophyte grade.
Although there are reports of possibly older cryptospores, the Hanadir
assemblage described herein clearly establishes their presence by Lla
nvirnian time.