Náttúrufræðingurinn

Volume

Náttúrufræðingurinn - 1983, Page 184

Náttúrufræðingurinn - 1983, Page 184
SUMMARY Acer-leaves and samaras from lcelandic deposits by Lic. scienl. Leifur A. Símonarson, Raunvísindastofnun Háskólans, Dunhaga 3, 107 Reykjavík, Iceland and Dr. rer. nat. Walter L. Friedrich, Geologisk Institut, Árhus Universitet, C. F. M0llers Alleé 120, DK-8000 Árhus C, Denmark. In 1976 and 1982 the authors described fossil Acer-leaves and samaras from seve- ral Tertiary localities in Iceland and pointed out that they are distinct from recent and fossil species. There are two different types of samaras, as well as leaves, which seem to prove that there were at least two Acer-species living in Iceland in the Upper Miocene and Pliocene. Acer-samaras from the Hreðavatn area, West Iceland, are different from recent and fossil forms, especially due to their large size (up to 90 mm), big locules (up to 30 mm) and the characteristic wing form. We named them Acer askelssoni in 1976. They compare with the fruit of the recent species A. saccharinum from North Amer- ica. Another type of Acer-samaras from the Hreðavatn area, and several other localities in West and Northwest Iceland, is much smaller (up to 25 mm), with com- parative larger locules (up to 10 mm) and a different wing form, e. g. the tip of the wing is more ovate. These samaras are closely related to the modern species A. rubrum from eastern North America. In Iceland this latter type is always found together with Acer-leaves closely related to this species. The leaves are up to 15 cm long and 13 cm broad, quinquelobat, with the central lobe longer than the lateral ones. The proximal part of the central lobe has parallel margins. The angle between the central lobe and the upper lateral lobes is 38°—60° or 46,1° on average. The leaf base is cordate. The margin has straight- convex serration. The nervation is very similar to that of A. rubrum, however, the finest ends are not as often biforked. In 1982 we referred these leaves to a new species, Acer islandicum, and tentatively the smaller type of samaras is also referred to this species. They are synonymous with earlier described A. otopterix, A. crenati- folium, A. crassinervium, A. tricuspida- tum, A. rubrum and in part Vitis islandica from Iceland. Another type of Acer-leaves, up to 14 cm long and 18 cm broad, i. e. broader than they are long, has been found together with the samaras referred to as A. askelssoni. These leaves are quinquelobat, with the central lobe of similar length as the upper lateral lobes. The proximal part of the central lobe does not have parallel margins. The angle between the central lobe and the upper lateral lobes is 36°—50° or 42° on average. The leaf base is cordate. The margin has straight-straight serration. These leaves seem closely related to the modern North American species. A. sac- charum and may belong to A. askelssoni. Apparently Acer became extinct in Ice- land 7 Ma ago. About 6 Ma ago the first tillites were formed in Iceland, obviously by local glaciations on mountain tops and in inland areas. However, they represent the worldwide climatic deterioration that probably brought about the extinction of Acer and other Tertiary thermophilic spe- cies in Iceland. 168
Page 1
Page 2
Page 3
Page 4
Page 5
Page 6
Page 7
Page 8
Page 9
Page 10
Page 11
Page 12
Page 13
Page 14
Page 15
Page 16
Page 17
Page 18
Page 19
Page 20
Page 21
Page 22
Page 23
Page 24
Page 25
Page 26
Page 27
Page 28
Page 29
Page 30
Page 31
Page 32
Page 33
Page 34
Page 35
Page 36
Page 37
Page 38
Page 39
Page 40
Page 41
Page 42
Page 43
Page 44
Page 45
Page 46
Page 47
Page 48
Page 49
Page 50
Page 51
Page 52
Page 53
Page 54
Page 55
Page 56
Page 57
Page 58
Page 59
Page 60
Page 61
Page 62
Page 63
Page 64
Page 65
Page 66
Page 67
Page 68
Page 69
Page 70
Page 71
Page 72
Page 73
Page 74
Page 75
Page 76
Page 77
Page 78
Page 79
Page 80
Page 81
Page 82
Page 83
Page 84
Page 85
Page 86
Page 87
Page 88
Page 89
Page 90
Page 91
Page 92
Page 93
Page 94
Page 95
Page 96
Page 97
Page 98
Page 99
Page 100
Page 101
Page 102
Page 103
Page 104
Page 105
Page 106
Page 107
Page 108
Page 109
Page 110
Page 111
Page 112
Page 113
Page 114
Page 115
Page 116
Page 117
Page 118
Page 119
Page 120
Page 121
Page 122
Page 123
Page 124
Page 125
Page 126
Page 127
Page 128
Page 129
Page 130
Page 131
Page 132
Page 133
Page 134
Page 135
Page 136
Page 137
Page 138
Page 139
Page 140
Page 141
Page 142
Page 143
Page 144
Page 145
Page 146
Page 147
Page 148
Page 149
Page 150
Page 151
Page 152
Page 153
Page 154
Page 155
Page 156
Page 157
Page 158
Page 159
Page 160
Page 161
Page 162
Page 163
Page 164
Page 165
Page 166
Page 167
Page 168
Page 169
Page 170
Page 171
Page 172
Page 173
Page 174
Page 175
Page 176
Page 177
Page 178
Page 179
Page 180
Page 181
Page 182
Page 183
Page 184
Page 185
Page 186
Page 187
Page 188
Page 189
Page 190
Page 191
Page 192
Page 193
Page 194
Page 195
Page 196
Page 197
Page 198
Page 199
Page 200
Page 201
Page 202
Page 203
Page 204
Page 205
Page 206
Page 207
Page 208
Page 209
Page 210
Page 211
Page 212
Page 213
Page 214
Page 215
Page 216
Page 217
Page 218
Page 219
Page 220
Page 221
Page 222
Page 223
Page 224
Page 225
Page 226
Page 227
Page 228
Page 229
Page 230

x

Náttúrufræðingurinn

Direct Links

If you want to link to this newspaper/magazine, please use these links:

Link to this newspaper/magazine: Náttúrufræðingurinn
https://timarit.is/publication/337

Link to this issue:

Link to this page:

Link to this article:

Please do not link directly to images or PDFs on Timarit.is as such URLs may change without warning. Please use the URLs provided above for linking to the website.