Biogeography in the Sub-Arctic. Группа авторовЧитать онлайн книгу.
from Agatdalen (Grímsson et al. 2016a, 2016b).
Koch (1963) collected and described plant fossils from the late Palaeocene Agatdalen Formation, Nuussuaq Peninsula. Most common macrofossil elements of the Agatdalen flora are Metasequoia (locally), Trochodendroides [as Cercidiphyllum], Macclintockia, and Platanus bella (Heer) Kvaček, Manchester and Guo [as Dicotylophyllum bellum (Heer) Seward and Conway]. Koch (1963) recognized the extant genus Liriodendron (Figure 3B) but placed leaf imprints similar to modern Sassafras (Figure 3C) within the extinct genus Lauraceaephyllum based on subtle differences in venation between the fossil and the modern genus. Revision of the Agatdalen macroflora by Grímsson et al. (2016a) reduces the ca. 38 taxa by Koch (1963) down to ca. 32. Still, the newly studied palynoflora from the same formation is relatively rich, comprising at least 145 angiosperms, 25 gymnosperms and around 30 different spore types (Grímsson et al. 2016a, 2016b). Overall, the palaeovegetation of the Agatdalen area appears to have been dominated by riparian elements (ferns, Taxodioideae, Trochodendroides, Platanus, Figure 4C and D), and Fagaceae, Betulaceae, Hamamelidaceae and Vitis (Figure 4A) as elements of the well‐drained hinterland. The enigmatic plant Macclintockia also played a significant role in the palaeofloral assemblages.
Figure 3 Palaeocene fossil leaves from West Greenland (Agatdalen, Atanikerluk) and the Faroe Islands (Mykines). (A) Small acrodromous leaf from Upper Atanikerluk B, MGUH 6443 [as Paliurus pusillus Heer in Heer (1883; Pl. LXXXI, figs 9 and 10)]. (B) Liriodendron sp., from Agatdalen, MGUH 10393 [as cfr. Liriodendron sp. in Koch (1963; Pl. 16, fig. 1)]. (C) Sassafras sp., from Agatdalen, MGUH 10420 [as Lauraceaephyllum stenolobatus Koch in Koch (1963; Pl. 30, fig. 2)]. (D) Large actinodromous leaf from Upper Atanikerluk B, MGUH 6435 [as Cissites steenstrupi Heer in Heer (1883; Pl. LXXXI, fig. 1)]. (E) Metasequoia occidentalis (Newb.) Chaney, from Mykines (Beinisvørð Formation), S134471. (See colour plate section for colour representation of this figure.)
Figure 4 Palaeocene leaves and Eocene pollen from West Greenland (Agatdalen, Hareø) and the Miocene of Iceland (Selárdalur, Botn). (A) Vitis sp., from Agatdalen, MGUH 10421 [as cfr. Vitis olriki Heer in Koch (1963; Pl. 30, fig. 3)]. (B) Tilia selardalense Grímsson, Denk & Símonarson, from Selárdalur. (C) Platanus sp., from Agatdalen, MGUH 10412 [as Platanus sp. cfr. aceroides Goepp. in Koch (1963; Pl. 26, fig. 1)]. (D) Platanus sp., from Hareø. (E) Platanus sp., from Botn. (F) Platanus leucophylla (Unger) Knobloch, from Selárdalur, IMNH 302.
Figure 5 Palaeocene fossil leaves from Atanikerluk, West Greenland. (A) Fagopsiphyllum groenlandicum (Heer) Manchester, from Upper Atanikerluk A, MGUH 6894 [as Fagus castaneaefolia Ung. in Heer (1868; Pl. XLVI, fig. 3a)]. (B) Fagopsiphyllum groenlandicum (Heer) Manchester, from Upper Atanikerluk A, MGUH 6269 [as Castanea ungeri Heer in Heer (1883; Pl. LXIX, fig. 3)]. (C) Fagopsiphyllum groenlandicum (Heer) Manchester, from Upper Atanikerluk A, MGUH 6270 [as Quercus grönlandica Heer in Heer (1883; Pl. LXIX, fig. 4)]. (D) Eotrigonobalanus sp., from Upper Atanikerluk B, MGUH 6349 [as Quercus laharpii Gaud. in Heer (1883; Pl. LXXIV, fig. 2)]. (E) Eotrigonobalanus sp., from Upper Atanikerluk B, MGUH 6372 [as Pterocarya denticulata Web in Heer (1883; Pl. LXXVI, fig. 1)]. (F) Eotrigonobalanus sp., from Upper Atanikerluk B, MGUH 6390 [as Laurus reussii Ettingsh. in Heer (1883; Pl. LXXVII, fig. 7)]. (G) Eotrigonobalanus sp., from Upper Atanikerluk B, S109006 [as Laurus primigenia Ung. in Heer (1880; Pl. III, fig. 8a)]. (H) Eotrigonobalanus sp., from Upper Atanikerluk B, S109107. (See colour plate section for colour representation of this figure.)
Macrofossils of the Upper Atanikerluk A flora comprise a large number of leaves resembling various modern genera of Fagaceae. Among these, Fagopsiphyllum is fairly abundant (Figure 5A to C, see Plate section). Figure 5C shows a typical leaf of Fagopsiphyllum; in contrast, the leaves shown in Figure 5A and B, although falling into the morphological variability of Fagopsiphyllum, clearly are reminiscent of leaf types encountered in modern taxa of Quercus section Cyclobalanopsis, and of the castaneoid genera Lithocarpus and Castanopsis (see illustrations in Camus 1929 et seq.). Another distinct leaf type is morphologically similar to both leaves from the Paleogene of North America (Dryophyllum‐like leaves; Jones and Dilcher 1988) and to Eotrigonobalanus from Europe (Kvaček and Walther 1989; Figure 5D to H). The pollen spectrum of the Upper Atanikerluk A flora has not yet been studied with high resolution scanning electron microscopy (SEM). However, the contemporaneous Agatdalen flora and the middle Eocene Hareø flora have recently been investigated and yield a remarkably high diversity of Fagaceae pollen (Grímsson et al. 2015, 2016a). Pollen unambiguously referable to Fagus, along with macrofossils of this genus, provide reliable evidence of this genus in the Cenozoic of Greenland (Figure 6A and B and Figure 7A). In addition, pollen of various Castaneoideae (according to Ørsted; see Praglowski 1984) is documented (Figure 6C and D). Numerous types of Quercus pollen represent various sections within the genus: Sect. Lobatae (Figure 6I and J), Lobatae/Quercus (white or red oaks; Figure 6K and L) and sect. Protobalanus (see Grímsson et al. 2015). Apart from this, additional Fagaceae pollen types represent extinct or ancestral lineages, Eotrigonobalanus (Figure 6G and H), Paraquercus (see pl. 12, Figures 1 to 5 in Grímsson et al. 2016b), and the pollen shown in Figure 6E and F. The latter is indistinguishable from pollen of the modern Quercus sect. Ilex (according to Denk and Grimm 2010; Denk et al. 2017; synonymous with subgenus Heterobalanus according to Menitsky 1984, 2005). This type of pollen has been suggested to be plesiomorphic within oaks (Denk and Grimm 2009a). In the Neogene of Europe, pollen of this type co‐occurs with leaves of Quercus drymeja Unger and Q. mediterranea Unger belonging to Quercus sect. Ilex (Denk et al. 2010b). Based on the modern distribution of this group of oaks from the Mediterranean area to south of the Himalayas and Southeast Asia (Menitsky 1984; Denk and Grimm 2010) and of the absence of foliage indicative of this group, the pollen encountered in the Eocene Hareø flora of