NEW EVIDENCE FOR LAND PLANTS FROM THE LOWER MIDDLE ORDOVICIAN OF SAUDI-ARABIA

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.