Fossil Seed Ferns

In 1927 T. G. Halle published an extensive synthesis of the Permian fossil plant assemblages from China’s Shanxi Province that included five genera and species of seed plant that either had ovules in organic attachment or closely and repeatedly associated with foliage. These fertile pteridosperms were the subject of a later publication (1929) that provided additional information on each species, but since that time only Nystroemia pectiniformis Halle has been subjected to detailed investigation based on the original materials. Reinvestigation of the remaining four species has yielded additional examples and new information for each species, and has confirmed the pteridospermalean affinity for three of the four species. Alethopteris norinii Halle shows organic attachment of a pollen organ similar to Wittleseya (Newberry) Halle and is reinterpreted as a microsporangiate medullosan pteridosperm. Emplectopteris triangularis Halle and Sphenopteris tenuis (Schenk) Halle both bear numerous ovules attached directly to the leaf laminae, with Emplectopteris conforming with the gross-organisation of callistophytalean pteridosperms and Sphenopteris tenuis being interpreted as a derived lagenostomalean pteridosperm. However, discovery of the counterpart to the key specimen of Pecopteris wongii Halle that Halle interpreted as bearing ovules demonstrates this species to be a sterile marattialean frond that agrees with its assignment to Pecopteris. In addition, two further specimens are demonstrated to be fertile organs of previously unknown pteridosperms; Norinosperma shanxiensis gen. et sp. nov. bears cardiocarpalean ovules abaxially on the proximal portions of the frond with ovules positioned directly on the veins of a leaf lamina; Norinotheca shanxiensis gen. et sp. nov. bears large pollen organs abaxially and singly on the vein of the leaf lamina. Collectively Halle’s pteridosperms remain important today as they are some of the few specimens that actually demonstrate organic connection of fertile organs to foliage, helping to characterise the morphology and organisation of this seed plant group. These species also demonstrate the persistence of seed plant families and genera in the Permian of China that became regionally extinct at the end of the Carboniferous in Euramerica, and show that pteridosperms remained an important component of Permian as well as Carboniferous floras globally.

Well-preserved floras from the Alpine Early–Middle Triassic are rare, and thus our understanding of the vegetation in this area during this period of time continues to be incomplete. As a result, every new find represents a significant piece of information that deserves thoughtful consideration. Anisian (Middle Triassic) sphenophytes and pteridosperms have recently been recovered from the Ku¨hwiesenkopf locality (Monte Pra` della Vacca) in northern Italy. The sphenophytes are represented by stem fragments, strobili and isolated sporangiophore heads
of Equisetites, as well as by a few specimens of Neocalamites
sp. and Echinostachys sp. The pteridosperms include abundant remains of the peltasperm foliage type Scytophyllum bergeri. A second Scytophyllum species in this flora, S. apoldense, is regarded as conspecific with S. bergeri based on epidermal anatomy; the two morphotypes are interpreted as sun and shade leaves of a single biological species. The seed-bearing disc Peltaspermum bornemannii sp. nov. probably represents the female reproductive structure of S. bergeri. Additional pteridosperm remains include foliage assignable to Sagenopteris sp. and Ptilozamites sp., in both cases perhaps the earliest records of these genera.

Abundant and well-preserved plant macrofossils have been recently collected near Dogna in the Julian Alps (Northeastern
Italy). The macroflora is borne by a thick succession of subtidal clays, marls and bioturbated to nodular wackestone-packstones
ascribed to the Rio del Lago Formation. The ammonoids and palynomorphs from the formation indicate typically an early Carnian age. The plant association includes mainly conifers and pteridosperms, but rare ferns and horsetails have been found as well. Several conifers are represented both by shoots, leaves and less abundant fructifications, including well-preserved cuticles of cheirolepidiaceous affinity. The seed fern leaves belong to the genus Ptilozamites, the fern pinnae to the genus Marantoidea and the horsetail stems to the genus Equisetites. Small amber drops have been also found in association with the macroflora. The palynological samples are dominated by pollen attributed to the conifers (58%), mostly represented by species of cheirolepidiaceous affinity. Pteridosperm pollen is also well-represented, while spores of ferns and lycopods are rare.