Alnus carpinoides Lesquereux 1883

Belonging to the Betulaceae (birch) family, trees and shrubs of the genus Alnus are more commonly known as Alders. There are about 30 extant species, distributed throughout the North Temperate Zone as well as in South America along the Andes. The largest species in Europe is the Black Alder (A. glutinosa), reaching over 30 meter. By contrast, the widespread Green Alder (A. viridis) is rarely more than a 5 meter tall shrub.

These plants are monoecious, bearing separate reproductive units of both sexes, referred to as catkins. The male catkins are very elongate, while the female catkins are shorter and rounded. Alnus differs from Betula (the birches, belonging to the same family) in that the female catkins are woody and do not disintegrate at maturity, opening to release the seeds in a similar manner to many conifer cones. Pollination generally occurs by wind, though some species are also visited by insects.

The photos below show fossil specimens of A. carpinoides from the Oligocene (~31 Ma) of the Little Butte Volcanic Series (Oregon, US). The foliage assigned to this species has a rather variable morphology [Brown, 1936]. The species is well figured and described by Lesquereux [1883]. A. carpinoides comprises specimens that are pronouncedly broadly ovate-acuminate in shape, with roudned-cuneate bases. Of the extant species, A. carpinoides most closely resembles A. tenuifolia, native to the western United States.

Specimens figured here at OergroenMuseum were obtained in trade with Scott Morrison, one of the most knowledgeable collectors I've had the pleasure trading plant fossils with. 

 Figures 1-3: A. carpinoides leaves and female catkins
Figure 4: extant specimen of A. glutinosa

References:

• Brown, R. W., (1936) Additions to some fossil floras of the western United States, Geological Survey professional paper, 186: 163-206
• YPM Paleobotany - Online Catalog (LINK)

Rhizome from a Miocene lakeside at Rátka, Hungary

Subterranean rooting-organs of aquatic and waterside plants, called rhizome, occur relatively common as fossils. It is however, much more rare for them to fossilize as petrifactions, preserving the three-dimensional structure to the finest detail. A series of (in)active quarries along the road connecting the villages of Rátka and Mád (northeastern Hungary) form one of the few sites worldwide to produce such a high-quality mode of anatomical preservation of grass-like plants.  

The Rátka locality is situated at the western margin of the Herceg-Köves-hegy Mountains of the Tokaj Mountains (part of the Carpathians). This volcanic region has since long been known, both for its famous Tolkaj wines [e.g. Howkins, 1999] and its geology [Szabo, 1865 in Gregor, 2007]. The quarries operate in a highly variable sequence of limnic (lake) deposits, consisting of hydroquartzites, geyserites and tuffites, which is surrounded and underlain by andesitic-dacitic volcanics, rhyolitic lavas and zeolite-rich tuffs, that make up the broader area [cf. Pécsi-Donáth and Nagy, 1988]. These volcanics are Sarmatian (Upper Miocene, Tortonian equivalent) in age [Huber and Pavlicek, 2007]. At that time, about 10-11 Ma, the area around Rátka formed a large, flat terrain and lake, being fed silica-rich groundwater by at least ten hot-springs. Intensive post-volcanic events periodically caused tectonic movement. When plant debris would enter the lake, the siliceous water impregnates the wood tissue, forming clear transparent opal, thereby preserving the plants in amazing detail [Huber and Pavlicek, 2007; Gregor, 2007].

The rhizome found at Rátka was described and named Rhizocaulon huberi, after the collector who originally discovered the permineralised material, by Gregor [2007]. According to the given diagnosis and classification, it is not yet ascertained whether Rhizocaulon huberi belongs to the Poaceae (true grasses, such as the genera Phragmites and Arundo) or the Cyperceae (sedges). Although, in his comparison with extant taxa, Gregor notes that the rhizome from Rátka seems to have less in common with the sedge family, uncertainty remains, and therefore, the rhizome was provisionally grouped into the morphogenus Rhizocaulon Sapporta.

Figures 1-7 show parts of the root (figs. 1-3) and the appending blade of grass (figs. 4-6), together with a schematic of the complete rhizome (fig. 7). The club-like rhizome has side-buds and numerous rounded lateral root-ropes, which tend to concentrate in concentric rows. Length of the rhizome ranges up to about 10 cm, with a thickness between 2 and 4 cm [Gregor, 2007]. It consists of two parts, a smooth inner part and an outer structure, which is heavily lobed (e.g. figs. 1-3, and this comparison to an extant species). The leaf sheaths (figs. 3-6) can be subdivided into groups, based on their relative position, namely those that are derived directly from the rhizome, and the parts of the blade that are more distant, or even sub-aerial [Gregor, 2007]. The morphology of the sclerenchyma changes from circular to triangular (fig. 5) and then narrows down, going from the rhizome to the surface, leaving only a radially built-up longitudinal structure in the uppermost parts of the leaf sheath [Gregor, 2007] (fig. 7). 

Figures 1-6: (1-3) parts of the rhizome and root, (4-6) the leaf sheath, appending blade of grass.

Figure 7: Schematic with cross-sections [from Gregor, 2007].

The specimens featured here at OergroenMuseum were obtained by trade with Wolfgang Putz, an Austrian collector specializing in petrified wood. The beautiful Rátka collection on his website is extensive and well photographed. See also Andrej Knjasew's page on Rátka (in Russian). Furthermore, I would like to add that the Documenta naturae issue on the topic (in German) is a great acquisition to the library of all who are interested in fossil plants.

References:

• Gregor, H.-J. (2007) Rhizocaulon huberi nov. spec., Rhizome von Poaceen/Cyperaceen aus dem Obermiozän von Rátka (Ungarn, Sarmatium), Documenta naturae 167, 21-49 (link).
• Howkins, B. (1999) Tokaji: a classic – lost & found, The International Wine and Food Society, 1-24, London, UK (PDF).
• Huber, P.C. and P. Pavlicek (2007) Rátka, eine obermiozäne (Sarmatium) Fundstelle für Hölzer und Rhizome in Ungarn, Documenta naturae 167, 1-19 (link).
• Pécsi-Donáth, É. and G. Nagy (1988) Co(II) ion sorption of zeolitic rocks and minerals from Tokaj Hill (Hungary), in Occurrence, Properties and Utilization of Natural Zeolites, eds.: D. Kalló and H.S. Sherry, Akadémiai Kiadó, Budapest, 291-308.

Zelkova Spach 1841

Zelkova is a genus of deciduous trees and shrubs, members of the elm family (Ulmaceae), and comprises six extant species, namely: Z. abelicea, Z. carpinifolia, Z. serrata, Z. sicula, Z. sinica, and Z. schneideriana. Leaves of Zelkova are alternate, have serrated margins, and differ from Ulmus foliage in having a symmetrical base to the leaf blade. The wood has a ring-porous structure. Zelkova species are monoicous, the female flowers being placed atop, and the male flowers below the shoots. The fruit borne by Zelkova plants can be described as dry, asymmetrical drupes, produced singly in the leaf axils.

Up to the end of the Pliocene, Zelkova was common throughout Europe and also occurred in the northern Americas. Extensive glaciation during the Pleistocene however, confined the genus’ range. Nowadays, Zelkova can only be found in areas where (less severe) local glaciation occurred, such as the eastern Mediterranean islands and the Caucasus in Europe, and parts of eastern Asia [Follieri et al. 1986]. Figure 1 shows a fossil specimen from the Miocene of Hungary. Two other examples, namely Z. nervosa from the Eocene of Utah (Green River Formation) and Z. brownii from the Eocene of Nevada, can be found here and here, respectively. Figure 2 displays an extant Z. serrata from Osaka-fu, Japan.

Figures 1-2: (1) Zelkova sp. from the Miocene of Hungary (2) Z. serrata (Thunb.) Makino 1903, extant species, Osaka-fu, Japan (c) photo: Kenpei, 2007

References:

• Follieri, M., D. Magri, and L. Sadori, (1986) Late Pleistocene Zelkova Extinction in Central Italy, New Phytologist 103 (1): 269-273

The 'Aachener Oberkreide' flora

The Aachen Formation is part of the Chalk Group and comprises the oldest Cretaceous strata to be found in northeast Belgium, the southern Netherlands, and adjacent Germany. It lies unconformably atop folded, heavily weathered Palaeozoic basement and forms the infill and cover over a palaeo-peneplain. Its thickness varies from about 1 to 130m [Batten et al., 1988].  The Aachen Formation is commonly regarded as middle to late Santonian in age [Meijer, 2000], although estimates do vary from middle Cenomanian to early Campanian [Batten et al., 1988].

Two Members (a lower and an upper one) can be recognized within the Aachen Formation, namely the Hergenrath Beds, alternatively known as the “Basiston” [Breddin et al., 1963], and the Aachen Beds. Sedimentary facies range from lagoonal for the lowermost parts to fluviatile and littoral for the uppermost deposits [Meijer, 2000].

The Hergenrath Beds consist mainly of grey to limonite-coloured (sandy) clays, minor silts, and light grey very fine quartzite sands. Coarser sands and gravel intercalations, which can be up to several meters thick, occur widely near the Hergenrath Beds’ base [Knapp, 1978]. Brown coal layers in the order of centimeters thick are found locally [Meijer, 2000] and ferruginous horizons are also present, with red clays forming a minor component of the Hergenrath Beds [Batten et al., 1988]. Some beds contain numerous small wood fragments (figs. 1-4) and the clays can contain compressions of leaves (figs. 5-6). According to Batten et al. [1988] most of the plant remains described by Debey [1948] were most likely collected from this part of the succession. Towards the southeast the coarse sands and gravel component increases and the Hergenrath Beds probably transgress into the Mospert Sands/Gravels, which are considered to be of the same age [Batten et al., 1988]. Depending on palaeo-relief of the underlying basement, the total thickness of the Hergenrath Beds varies between about 10 and 35m.

The Hergenrath Beds and the overlying Aachen Beds are separated by a minor disconformity. The period of erosion/non-deposition is thought to have been relatively short, and it its, therefore, reasonable to assume both sides of the hiatus are part of the same geological stage [Batten et al., 1988; Meijer, 2000].

Compared to the Hergenrath Beds, the Aachen Beds are rather uniform in composition, with the bulk of the sequence consisting of white to yellow, fine quartzite sands, some of which are strongly cross-bedded. However, the base contains accumulations of coarse sands. Clay lenses occur locally throughout the lower part of the Aachen Beds. Remains of twigs (figs. 1-4) and foliage (figs. 5-6) can be found in these and the more silty intervals. The sands contain petrifactions of coniferous cones (fig. 7) [e.g. Stockmans, 1946] and abraded silicified driftwood (fig. 8), often showing boreholes, bored by Teredo bivalves (fig. 9) [Batten et al., 1988; Meijer, 2000]. The composition of this silicified wood assemblage, as well as the anatomy of these woods, indicates a seasonal and humid warm-temperate to subtropical climate [Meijer, 2000].

The uppermost strata of the Aachen Beds are usually 1-6m of clayey silts, generally referred to as the “Dach-schluff” [Batten et al., 1988]. The Member is terminated by an erosion surface which separates the Aachen Formation from the Vaals Formation.

Figures 1-9: (1-4) coniferous twigs, Aachen area, (5-6) leaves, Aachen area, (7) remains of a cone, Aachen area, (8) silicified wood, Aachen area, (9) driftwood (Cedrus sp.) showing borings of Teredo bivalves, Hergenrath, Belgium

The following website is in German, but I found it to be a very nice source of information on the Aachen Formation. Besides that, the specimens featured there by Helmut Knoll are just amazing and really worth a look. Most specimens featured here on OergroenMuseum came to me via a Russian collector, Andrej Knjasew, specializing in fossil wood. His collection is also well worth a digital visit. Fantastic material!

References:

• Batten, D.J., J. Dupagne-Kievits, and J.K. Lister (1988) Palynology of the upper Cretaceous Aachen Formation of northeast Belgium. The Chalk District of the Euregio Meuse-Rheine - M. Streel and M.J.M. Bless (Editors), April 1988: 95-103
• Breddin, H., H. Bruhl, and H. Dieler, (1963) Das Blatt Aachen-NW der praktisch-geologischen Grundkarte 1:5000. Geol.Mitt., 1:251-428
• Knapp, G. (1978) Erlauterungen zur Geologischen Karte der nodlichen Eifel, 1:100.000; 2. Auflage Geol. L. - Amt Nordrh.-Westf., Krefeld, 152p.
• Meijer, J.J.F., (2000) Fossil woods from the Late Cretaceous Aachen Formation, Review of Palaeobotany and Palynology 112 (2000) 297–336
• Stockmans, F. (1946) Vegetaux de l'assise des Sables d'Aix-la-Chapelle recoltes en Belgique (Senonien inferieur). Mem. Mus. roy. Hist. nat. Belg., 105: 50p.

Nymboida Coal Measures

The Nymboida Coal Measures (Clarence-Moreton basin, New South Wales) represent a southern extension of the Esk Trough (Queensland, Australia). The plant fossils from these deposits make up a Dicroidium-flora,typical for the Middle Triassic (Anisian-Ladnian) of Gondwana. Ginkophytes, ferns and cycads (see figures) are also components of such assemblages. The specimens figured here come from the Farquhars Coal Seam, part of the Basin Creek Fm. (Open Cut quarry).

Figures 1-6: plant fossil specimens found at the Nymboida Open Cut quarry.

                    (1) Sphenobaiera argentinae (Kurtz) Frenguelli, 1946, 

                    (2) Asterotheca chevronervia Holmes, 2001, 

                    (3) Dicroidium cf. odontopteroides var. remotum (Szajnocha) Retallack, 1977, 

                    (4) Kurtziana cf. cacheutensis (Kurtz) Frenguelli, 1942, 

                    (5) Dicroidium sp., 

                    (6) Dicroidium zuberi Retallack, 1977

References:

• Holmes, W.B.K. (2000), The Middle Triassic megafossil flora of the Basin Creek Formation, Nymboida Coal Measures, New South Wales, Australia. Part 1. Bryophyta, Sphenophyta, Proceedings of the Linnean Society of New South Wales 122, pp. 43-68
• Holmes, W.B.K. (2001), The Middle Triassic megafossil flora of the Basin Creek Formation, Nymboida Coal Measures, New South Wales, Australia. Part 2. Filicophyta, Proceedings of the Linnean Society of New South Wales 123, pp. 39-87
• Holmes, W.B.K. (2003), The Middle Triassic megafossil flora of the Basin Creek Formation, Nymboida Coal Measures, New South Wales, Australia. Part 3. Fern-like foliage, Proceedings of the Linnean Society of New South Wales 124, pp. 53-108 
• Holmes, W.B.K. and H.M. Anderson (2005), The Middle Triassic megafossil flora of the Basin Creek Formation, Nymboida Coal Measures, New South Wales, Australia. Part 4. Umkomasiaceae. Dicroidium and Affiliated Fructifications, Proceedings of the Linnean Society of New South Wales 126, pp. 1-37
• Holmes, W.B.K. and H.M. Anderson (2005), The Middle Triassic megafossil flora of the Basin Creek Formation, Nymboida Coal Measures, New South Wales, Australia. Part 5. The genera Lepidopteris, Kurtziana, Rochipteris and Walkomopteris, Proceedings of the Linnean Society of New South Wales 126, pp. 39-79 
• Holmes, W.B.K. and H.M. Anderson (2007), The Middle Triassic Megafossil Flora of Basin Creek Formation, Nymboida Coal Measures, New South Wales, Australia. Part 6. Ginkgophyta Proceedings of the Linnean Society of New South Wales 128 pp. 155-200 
• Holmes, W.B.K. and H.M. Anderson (2008), The Middle Triassic Megafossil Flora of the Basin Creek Formation, Nymboida Coal Measures, New South Wales, Australia. Part 7. Cycadophyta Proceedings of the Linnean Society of New South Wales 129 pp. 113-149
• Holmes, W.B.K., H.M. Anderson annd J.A. Webb (2010), The Middle Triassic megafossil flora of the Basin Creek Formation, Nymboida Coal Measures, New South Wales, Australia. Part 8. The Genera Nilssonia, Taeniopteris, Linguifolium, Gontriglossa and Scoresbya, Proceedings of the Linnean Society of New South Wales 131, pp. 1-26