Reinhard Zetter

Episodic migration of oaks to Iceland: Evidence for a North Atlantic “land bridge” in the latest Miocene

Dating the subsidence history of the North Atlantic Land Bridge (NALB) is crucial for understanding intercontinental disjunctions of northern temperate trees. Traditionally, the NALB has been assumed to have functioned as a corridor for plant migration only during the early Cenozoic, but recent findings of plant fossils and inferences from molecular studies are challenging this view. Here, we report dispersed pollen of Quercus from Late Miocene sediments in Iceland that shows affinities with extant northern hemispheric white oaks and North American red oaks. Older (15 to 10 Ma) sediments do not contain pollen of Quercus suggesting it arrived after that time. Pollen from the 9-8 Ma Hrútagil locality is indistinguishable from morphotypes common among white and red oaks. In contrast, pollen from the 5.5 Ma Selárgil locality has a tectum that is at present confined to North American white and red oaks, indicating a second episode of migration to Iceland. These findings suggest that transatlantic migration of temperate plant taxa may not have been limited by vast areas of sea or by cold climates during the Miocene. Furthermore, our results offer a plausible explanation for the remarkably low degree of genetic differentiation between modern disjunct European and North American oaks.

Pollen, fruits, and leaves of Tetracentron (Trochodendraceae) from the Cainozoic of Iceland and western North America and their palaeobiogeographic implications

Dispersed pollen, fruits, and leaves of Tetracentron (Trochodendraceae) are described from the Miocene of Iceland and assigned to a new species, Tetracentron atlanticum. The Icelandic fossils represent the first unambiguous record of Tetracentron for the Cainozoic of Europe. Well‐preserved dispersed grains of Tetracentron are also identified from the Eocene and Miocene of western North America and compared to the Icelandic fossils. In general, Tetracentron pollen is rather uniform through the Eocene to Recent, only displaying minor variation in ornamentation. Leaves are diagnostic at the species level. The findings add substantial new information to the generally poor fossil record of Tetracentron and indicate a more circumpolar distribution of the genus than previously assumed. The north‐eastern Asian – western North American Cainozoic distribution for plant taxa presently confined to East Asia is relatively common. In contrast, the extension to Iceland is remarkable, particularly in view of the absence of the genus in the fossil record from eastern North America, Greenland, and Central Asia and mainland Europe.

Advances in our knowledge of the Miocene plant assemblage from Kreuzau, Germany

Abstract The history of palaeobotanical research on Kreuzau is outlined. The sedimentary succession is interpreted and the age of the site discussed. Based on a compilation of the different plant parts, the florisitic composition of the assemblage is analysed. Some new and interesting discoveries are described and inferences made with regard to the habitats of these and other elements. Different techniques are used in an evaluation of the palaeoclimate and signs of faunal interaction mentioned.

A multidisciplinary approach to reconstruct the Late Oligocene vegetation in central Europe

Abstract An interdisciplinary approach has been taken in the evaluation of the paleobotanical record of Late Oligocene vegetation in the Thierbach member of the Weiselster basin, Germany. Sedimentological, paleopedological, paleobotanical (megafloral and carpological), palynological and palynofacies, and biogeochemical investigations have been coordinated on an abandoned channel-fill sequence in order to develop a comprehensive data base from which to reconstruct this setting. The benefits of using multidisciplinary data sets are outlined including how these data sets may not only be complementary or contradictory, but also how independent data sets amplify and validate interpretations.

Fossil Ericaceae from New Zealand: deconstructing the use of fossil evidence in historical biogeography

The Australasian Ericaceae epitomize many problems in understanding the biogeography of the southern hemisphere, especially the relative contributions of Gondwanan vicariance and dispersal. Late Cretaceous fossil pollen of the family suggests extreme antiquity of the group in Australasia, but recent phylogenetic evidence suggests much younger histories for most of the groups in that region. This paper documents two new species of latest Oligocene-Early Miocene macrofossils of Ericaceae from New Zealand. Cyathodophyllum novae-zelandiae G.J.Jord. & Bannister gen. and sp. nov. is the oldest record of the tribe Styphelieae, but is of a clade now extinct in New Zealand, possibly related to the Tasmanian genus Cyathodes. Richeaphyllum waimumuensis G.J.Jord. & Bannister sp. nov. is a member of Richeeae, but it is ambiguous as to whether it is a member of the impressive modern New Zealand radiation in Dracophyllum. These fossils emphasize the fact that at least some of the fossil pollen of Ericaceae may have been derived from extinct lineages and therefore should not be used as evidence for the antiquity of any modern New Zealand clade of Ericaceae. New fossils and/or detailed analysis of fossil and extant pollen may help resolve such uncertainty.

The fossil pollen record of Araceae

The fossil record of Araceae pollen beginning in the late Early Cretaceous and peaking in the Paleocene/Eocene is very sparse up to now, consisting of three highly distinctive types: zona-aperturate pollen of the Monstera or Gonatopus type (very similar to Proxapertites operculatus), an ulcerate-spiny type typical for Limnobiophyllum, and a polyplicate, omniaperturate pollen type (an ephedroid pollen with non-gnetalean affinities) which was recently reported from the late Early Cretaceous (Mayoa portugallica). An extensive literature search has shown that some distinctive Ephedripites forms (the Paleogene Ephedripites vanegensis, and the Late Cretaceous Ephedripites elsikii) are very similar to pollen of Spathiphyllum and both species are here transferred from Ephedripites to Spathiphyllum (as comb. nov.). We also add new fossil findings to the Araceae record. The new findings include a zona-aperturate, microperforate to microreticulate pollen type from the Palaeocene of Colombia, highly similar to extant Gonatopus or Zamioculcas or Monstera pollen (Araceae) and to fossil Proxapertites operculatus, which is currently seen as a fossil equivalent; and, an ulcerate, spiny pollen from the Eocene of Stolzenbach, Germany, extending the range of Limnobiophyllum (Pandaniidites), which is thought to be an extinct member of extant Araceae. The three pollen types add considerably to the reliable fossil record of the family that now contains more than 20 records of these three pollen types: with the zona-aperturate type recorded from the tropical or subtropical regions of Northern and Southern America, Central Africa, Southern and Central Europe, from the Indian subcontinent and the Malayan Archipelago; the ulcerate type occurring in North America and Europe; and the polyplicate type mainly occurring in South America and South-West Europe. Now we have good evidence that some of the aroid subfamilies were already in existence in the Cretaceous, increasing in diversity and worldwide distribution in the Paleogene.

Fagaceae pollen from the early Cenozoic of West Greenland: revisiting Engler’s and Chaney’s Arcto-Tertiary hypotheses

In this paper we document Fagaceae pollen from the Eocene of western Greenland. The pollen record suggests a remarkable diversity of the family in the early Cenozoic of Greenland. Extinct Fagaceae pollen types include Eotrigonobalanus, which extends at least back to the Paleocene, and two ancestral pollen types with affinities to the Eurasian Quercus Group Ilex and the western North American Quercus Group Protobalanus. In addition, modern lineages of Fagaceae are unambiguously represented by pollen of Fagus, Quercus Group Lobatae/Quercus, and three Castaneoideae pollen types. These findings corroborate earlier findings from Axel Heiberg Island that Fagaceae were a dominant element at high latitudes during the early Cenozoic. Comparison with coeval or older mid-latitude records of modern lineages of Fagaceae shows that modern lineages found in western Greenland and Axel Heiberg likely originated at lower latitudes. Further examples comprise (possibly) Acer, Aesculus, Alnus, Ulmus, and others. Thus, before fossils belonging to modern northern temperate lineages will have been recovered from older (early Eocene, Paleocene) strata from high latitudes, Engler’s hypothesis of an Arctic origin of the modern temperate woody flora of Eurasia, termed ‘Arcto-Tertiary Element’, and later modification by R. W. Chaney and H. D. Mai (‘Arcto-Tertiary Geoflora’) needs to be modified.

The Morphology of Pollen Tetrads and Viscin Threads in Some Tertiary, Rhododendron-Like Ericaceae

Abstract The morphology of pollen tetrads and viscin threads is described in fossil Ericaceae pollen from various Eocene/Oligocene/Miocene localities in Europe (Germany, Austria), North America (eastern U.S.A.), and Asia (eastern China). The typical characters of the tetrad configuration, the exine ornamentation and sculpturing, and especially the viscin thread morphology are extremely similar to or even indistinguishable from that in extant members of Rhododendron. All these pollen morphological features strongly suggest that all the investigated material can be assigned to a modern taxon of the Ericaceae: either to Rhododendroideae or even to Rhododendron itself.

Assessing the Fossil Record of Asterids in the Context of Our Current Phylogenetic Framework1

Abstract The fossil record provides good evidence for the minimum ages of important events in the diversification and geographic spread of Asteridae, with earliest examples extending back to the Turonian stage of the Late Cretaceous (~89 million years ago [Ma]). Some of the fossil identifications accepted in previous considerations of asterid phylogeny do not stand up to careful scrutiny. Nevertheless, among major clades of asterids, there is good evidence for a range of useful anchor points. Here, we provide a synopsis of fossil occurrences that we consider reliable representatives of modern asterid families and genera. In addition, we provide new examples documented by fossil-dispersed pollen investigated by both LM and SEM studies including representatives of Loranthaceae, Amaranthaceae, Cornaceae (including Nyssa L., Mastixia Blume, Diplopanax Hand.-Mazz.), Sapotaceae, Ebenaceae, Ericaceae, Icacinaceae, Oleaceae, Asteraceae, Araliaceae, Adoxaceae, and Caprifoliaceae from Paleogene sites in Greenland, western North America, and central Europe, and of Lamiaceae and Asteraceae from the Middle to Late Miocene in northeastern China. We emphasize that dispersed pollen, taken along with megafossil and mesofossil data, continue to fill gaps in our knowledge of the paleobotanical record.

Combined LM and SEM study of the Middle Miocene (Sarmatian) palynoflora from the Lavanttal Basin, Austria: Part II. Pinophyta (Cupressaceae, Pinaceae and Sciadopityaceae)

Abstract The palynoflora from the Lavanttal Basin is characterised by a diverse spectrum of conifers. Their pollen is mostly well preserved allowing for high taxonomic resolution. Most coniferous taxa belong to the Pinaceae (Abies, Cathaya, Cedrus, Keteleeria, Larix, Picea, Pinus and Tsuga) and the Cupressaceae (Cryptomeria, Glyptostrobus and Sequoia), but pollen of Sciadopityaceae (Sciadopitys) is also occuring. The presence of these conifer taxa supports previous suggestions based on sedimentological and palynological observations that the sediments of the Lavanttal Basin accumulated in a lowland/wetland environment. Many of the taxa described in this paper had a wide, mostly Northern Hemispheric distribution, occupying swamps, river plains, deltas, hummocks and also better drained habitats located near to the main areas of sedimentation during most of the Cenozoic. Modern relatives of most of the fossil taxa prefer ample precipitation, suggesting that during the Middle Miocene (Sarmatian), the Lavanttal area received plenty of rainfall; there is no indication of a seasonal climate with a drought period. In general, the conifer taxa identified here are suggestive of a warm-temperate climate.