Zhao et al.—New Jurassic Nilssoniopteris species from Xinjiang of China


Remarks.—The morphogenus Nilssoniopteris was established by Nathorst (1909) to accommodate European Jurassic cyca- dophyte leaves with an entire margin, without designating a type species (but assigned only one species, N. tenuinervis, to the newly erected genus). Soon afterwards, Thomas and Bancroft (1913) suggested that this generic name should be abandoned. Later, Harris (1932a) recognized the need for establishing a genus of Taeniopteris-type leaves with bennettitalean cuticle features and proposed the new name Taeniozamites. However, Florin (1933a) noted that the genus Nilssoniopteris should be restored with precedence over Taenizamites. Harris (1937) endorsed this view, and in his 1969 paper (Harris, 1969) gave the first diagnosis of Nilssoniopteris based on the original description of Nathorst (1909). Watson and Sincock (1992) slightly emended the diagnosis by adding the strap leaf shape. Boyd (2000) expanded the range of leaf forms to include lobed leaves, while Pott et al. (2007) further emended the diagnosis to include leaves that are completely dissected down to the rachis. In addition, after reviewing the macro- and micro- morphological features of the mid-Mesozoic Laurasian bennet- titalean leaf morphogenera, Pott and Mcloughlin (2009) further specified the lamina of Nilssoniopteris to be of four types: (1) entire margined; (2) having incompletely segmented (or “dissected”) lobes in the middle, but with basal and/or apical portions entire-margined; (3) having a completely but irregu- larly segmented middle portion, but with apical and/or basal portions entire-margined; and (4) having a (completely) and regularly segmented middle portion, but with apical and/or basal portions entire-margined. To summarize, the middle portion of the lamina of Nilssoniopteris can be of almost any shape that a bennetitalean lamina may have (from entire-margined, to incompletely dissected/lobed, completely and irregularly segmented, as well as completely and regularly segmented), as long as at least the apical and/or basal portions are entire- margined. Bennetitalean leaves with other shapes, particularly those whose whole blades are regularly segmented, were assigned by the authors to Anomozamites or Pterophyllum, which can be further separated by whether or not the leaflets (or lobes/segments) are up to two times as long as broad and whe- ther the leaves are impari-pinnate or pari-pinnate. As all of our present specimens are entire-margined and readily assignable to Nilssoniopteris, therefore we tentatively simply follow the diagnosis of Pott et al. (2007) and Pott and Mcloughlin (2009) to which we add the emendation, particularly of venation pattern.


527 In previous diagnoses, the veins of Nilssoniopteris were


noted as being free, simple or forked, ending at the margin. Accordingly, when Zhou (1978) described several taeniopter- ioid laminae from the Upper Triassic of Fujian, China (with veins sometimes bifurcated and then merging again or with two neighboring veins merging to form one vein, which are different from the simple veins traditionally described for Nilssoniopteris and Nilssonia, the marginal veins described in Yabeiella, and the forking and anastomosing secondary veins of Danaeopsis), he erected a new genus and a new species, Mironeura dakengensis, with unknown reproductive structures and cuticle features, to accommodate these fossils (Fig. 2.5). Later, more fossils that resemble Nilssoniopteris in macromorphology and cuticular features but with forked and merged veins were reported under the genus Nilssoniopteris, including Nilssoniopteris beyrichii from the Lower Cretaceous of Huolinhe, Inner Mongolia, China (Deng, 1995), Nilssoniopteris neimenguensis from the Lower Jurassic of Xilinhot, Inner Mongolia, China (Deng et al., 2017b), and Nilssoniopteris zirabensis from the Lower Jurassic of Iran (Schweitzer and Kirchner, 2003) (Fig. 2.1–2.3). This type of vein anastomosis was also reported in entire-margined Nilssonia having cycadalean-type cuticles, such as Nilssonia dictyophylla from the Lower Cretaceous of the outer zone of Japan (Kimura and Okubo, 1985) (Fig. 2.4) and Nilssonia taeniopterides from the Upper Triassic–Lower Jurassic of Queensland, Australia (Pattemore, 2016). These special veins are also found in our Xinjiang samples, especially in Nilssoniopteris crassiaxis n. sp., which fork and then merge, or merge with the adjacent veins. Due to the fact that this anastomosing venation is shared by both the bennettitalean Nilssoniopteris and the cycadalean Nilssonia, we see no logical reason to establish a new taxon solely on the basis of these anastomosing veins.We thus add the anastomos- ing venation to the diagnoses of these two genera, and accordingly, suggest abandoning the genus name Mironeura Zhou, 1978. Because no cuticular features were provided, we suggest following the notion of van Konijnenburg-van Cittert et al. (2017) to transferM. dakengensis Zhou, 1978 to the genus Taeniopteris.


Nilssoniopteris hamiensis Zhao and Deng, new species Figures 3–8


2010 Nilssoniopteris vittata; Deng et al., p. 93, fig. 4.11C.


Figure 2. Line drawings of species with anastomosing veins in Nilssonia and Nilssoniopteris.(1) Nilssoniopteris beyrichii (Deng, 1995); (2) Nilssoniopteris neimenguensis (Deng et al., 2017b); (3) Nilssoniopteris zirabensis (Schweitzer and Kirchner, 2003); (4) Nilssonia dictyophylla (Kimura and Okubo, 1985); (5) Mironeura dakengensis (Zhou, 1978), which should be more correctly transferred to Taeniopteris.


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