564
Journal of Paleontology 92(4):546–567
series of 1–3 pits and its different combinations of circular, hexa- gonal, and flattened pit shapes (Fig. 9). In Figure 10, the dispersion graphics compare species of the
genus Agathoxylon using data obtained from the specimens ana- lyzed in this contribution (Tables 1, 2) and fromthe literature. For this reason, in this study, data such as uniseriate pits, shape of the pits, and maximum number of pits in the cross-fields were col- lected from the following Agathoxylon species: A. africanum (Bamford) Kurzawe and Merlotti (Permo-Triassic, Jurassic– Cretaceous?) and A. karooensis (Bamford)Kurzawe andMerlotti (Permian and Cretaceous?) from South Africa (Bamford, 2000); A. protoaraucana (Triassic–Lower Jurassic) of Argentina (Gnaedinger and Herbst, 2009); A. liguaensis Torres and Philippe of the Lower Jurassic of Chile (Torres and Philippe, 2002) and Argentina (Gnaedinger et al., 2015); Dadoxylon (A.) termieri (Attims, 1965;Giraud and Hankel, 1985) of the Lower Jurassic of Africa;Cretaceous species described by Falcon-Lang andCantrill (2000, 2001); and A. chapmanae of Poole and Cantrill (2001). In Figure 10, the differences between fossil species are
clearly observed; only two groups of taxa occupy the same “morphology space”: (1) A. karooensis, Araucarioxylon sp. (Falcon-Lang and Cantrill, 2000), and the Patagonia specimens identified as A. santalense; and (2) A. termieri, Araucarioxylon sp. 1 (Falcon-Lang and Cantrill, 2001), and Araucarioxylon sp. 2 (Falcon-Lang and Cantrill, 2001), when comparing characters like percentage of uniseriate pits versus maximum number of cross-field pits (Fig. 10.1). When looking at anato- mical characters, such as uniseriate pits versus the shape of the pits, the groups of species mentioned are distinguished from each other, occupying different spaces in the above-mentioned graph (Fig. 10.2). The results obtained showthat not only is the number of pits in
the cross-field a diagnostic character, but also the shape of the radial pits (IAWA Committee, Richter et al., 2004). These parameters cannot only be used to discriminate genera and species of wood found in the same Formation, but also to establish differences/ similarities between other taxa described in other Formations.
Conclusions
This paper describes four coniferous wood taxa from the La Matilde Formation, clearly differentiated on the basis of their qualitative and quantitative anatomical parameters, that can be distinguished by their different percentages of tracheid radial pitting shapes and distribution (seriation) as well as by the range and mean number of pits in the cross-fields. This study con- tributes to the method proposed by Falcon-Lang and Cantrill (2000) because these parameters can be used to discriminate species of wood found in the same formation and between other taxa described in other formations. The findings in the La Matilde Formation of leaves and
Agathoxylon is cosmopolitan, but the species A. agathioides
and A. santalense have been previously described from the Upper Jurassic–Lower Cretaceous of the Rajmahal Hills, Bihar, India (Sah and Jain, 1964; Kraüsel and Jain, 1964), while A. termieri was described from the Lower Jurassic of Africa (Attims, 1965; Giraud and Hankel, 1985) and Argentina (Gnaedinger, 2006). Based on the analysis of ~250 specimens carried out so far,
in eight localities of the Gran Bajo de San Julián sector, and through data on the distribution of the in situ logs obtained from the census carried out in the forests, the Agathoxylon taxa described here presents a different floristic distribution in the La Matilde Formation. Agathoxylon agathioides and A. santalense together with Taxodioxylon Gothan and Prototaxoxylon intertrappeum Prakash and Srivastava species are found in the top of the sedimentary sequence that appears in the Barda Blanca and Cerro Conito localities, and in the NW Laguna La Guadalosa outcrop from Gran Bajo de San Julián sector and Bajo El Puma locality of the central and south-western sector (Gnaedinger and Herbst, 2006; Gnaedinger, 2007b). Agathoxylon termierii associated with fern stipes and Podocarpaceae wood (Podocarpoxylon feruglioi Gnaedinger; Circoporopitys herbstii Gnaedinger) was identified in the base of the sedimentary sequence, near the carbonaceous levels in the Barda Blanca and Cerro Conito localities, as well as in the northern part of the Estancia Meseta Chica locality (Gnaedinger, 2007b). Finally, A. santacruzense n. sp. with Circoporoxylon
austroamericanum Gnaedinger was found only in the south- eastern border of Laguna del Carbón locality (Gnaedinger, 2007b). The distinction of the species through qualitative and quantitative analyses and according to the distribution of the specimens in the different localities and in some localities in different strata of the sedimentary sequence could be indicating diverse forests at different moments during the Jurassic of the Patagonia (Gnaedinger, work in preparation). In this way, it could indicate, according to the distribution of the in situ logs of the fossil species found in the Barda Blanca and Cerro Conito localities, that these taxa formed small forests, or local forests, or small forests within dense forest, which is a habitat coincident with the extant Araucariaceae.
Acknowledgments
This contribution was partially funded by the Secretaría General de Ciencia y Técnica, Universidad Nacional del Nordeste (SGCyT-UNNE.PI 2015, 2018, Q005, 2014) and the Consejo Nacional de Investigaciones Científica y Técnicas-CONICET (PIP 2014, 2016, No. 112 201301 00317) in a grant conferred to SCG. The authors are grateful to Katarzyna Piper, Editorial Services (UK) for revision of the English grammar.
branch impressions and silicified seed and pollen cones indicate that the “Jaramillo Petrified Forest” was mainly composed of Coniferales belonging to the families Araucariaceae, Podocarpaceae, and? Taxodiaceae. According to the xylological analysis carried out in this study, the presence of the family Araucariaceae in the forests of the La Matilde Formation is corroborated.
References
Agashe, S., and Gowda, P., 1978, Anatomical study of a gymnospermous wood from Lower Gondwana of Maharashtra: Phytomorphology, v. 28, p. 269–274.
Agashe, S., and Prasad, K., 1989, Studies in fossil gymnospermouswoods, part 7. Six new species ofLowerGondwana (Permian) gymnospermouswoods from Chandrapur District, Maharashtra State, India: Palaeontographica, v. 138 B, p. 71–102.
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 |
Page 231 |
Page 232
