Otozamites douglasii Drinnan

Pole, Mike, 2019, Middle-Late Jurassic plant assemblages of the Catlins coast, New Zealand, Palaeontologia Electronica (a 51) 23 (3), pp. 1-48 : 15-17

Otozamites douglasii Drinnan in McLoughlin, Tosolini, Nagalingum and Drinnan, 2002

Figure 9

1917 Ptilophyllum acutifolium Morris ; Arber, p. 53, pl. 11, figs. 1, 2, 5.

2002 Otozamites douglasii Drinnan ; McLoughlin et al., p. 47, fig. 32.

Material. Black Point : LX1191, Blue Cod Bay : LX0679, 0681, Curio Bay: LX1229–1231, Otara- 36: LX2362, Slope-01: LX0656, Slope-04: Noted in the field.

Description. Fronds elongate, over 200 mm long ( Figure 9.1 ), pinnules adaxialy inserted, at around 60-70°, 13–14 mm long, 2.7–4.3 mm wide, apex acute, acroscopic margin straight or slightly concave, basiscopic margin convex ( Figure 9.1 ), acroscopic margin of leaflet base slightly or distinctly auriculate ( Figure 9.3 , 4 ) and sometimes slightly imbricate ( Figure 9.5 ), basiscopic pinnule edges distinctly contracted ( Figure 9.3 ), veins 6–9, sometimes radiating from base ( Figure 9.4 ), or acroscopic veins, either curving slightly acropetally, or running shortly to the margin.

Remarks. Several specimens have adaxialy inserted leaflet bases some of which are slightly imbricate at the base. These appear to be conspecific with what Arber (1917) illustrated as Ptilophyllum acutifolium . However, in neither case are basiscopic leaflet edges decurrent, but distinctly contracted ( Figure 9.3 ), thus placement in Ptilophyllum is inappropriate (Halle, 1913; Harris, 1969; Watson and Sincock, 1992). In addition, the acroscopic margin of leaflet bases is slightly or distinctly auriculate ( Figure 9.3 ), a character that is generally regarded as indicating Otozamites . Rees and Cleal (2004) cautioned that the leaflet bases could be distorted during taphonomic processes and that acroscopic veins curving acropetally was a more reliable character of Otozamites and would clarify any confusion with Zamites . There is no indication of leaftlet distortion in the Catlins material and, in the present specimens, the acroscopic veins either curve slightly acropetally, run shortly to the margin, but in one specimen ( Figure 9.4 ), more clearly radiate. Thus, the material described here and Arber’s (1917) Ptilophyllum acutifolium are assigned to Otozamites , a move already suggested by Cantrill (2000). Rees and Cleal (2004) argued the distinction between Ptilophyllum and Otozamites was probably artificial and that they “likely belonged to a ‘natural’ genus.”

In terms of pinnule shape and venation, the closest morphological match of the Catlins material is with Otozamites douglasii from the Lower Cretaceous of Victoria (McLoughlin et al., 2002), and although epidermal details are needed to be sure, the Catlins material is assigned to that species. However, there may be more than one species. For example, the O. linearis illustrated from Antarctica by Gee (1989) tens to have a higher pinnule L/W ratio than the Catlins material, although Bomfleur et al. (2011) documented a wider range of pinnule shape. Those Otozamites differ from most of the Catlins Coast Otozamites in their strongly radiating veins. However, one fragmentary Catlins specimen does show distinctly radiating veins (and also has a more prominent auricle).

Figures

FIGURE 4. Cladophlebis patagonica pinnules. 1. LX1498, Black Point (Note the distinct apical broadening of the pinnule base); 2. LX1074, Curio Bay; 3. LX1197, Slope-02; 4. LX1069, The Boat Harbour; 5. LX1076, Curio Bay (Note that some of the veins dichotomise twice.); 6. LX2070, The Boat Harbour (Note the pronounced apical broadening of the pinnule base which continues to the adjacent pinnule as a ‘wing’. All scale bars equal 10 mm).

FIGURE 9. Otozamites douglasii 1. Photographed in the field, Slope-04; 2. LX1231, Curio Bay; 3. LX656, Slope-01, with slightly auriculate acroscopic margin of the pinnule bases; 4. LX1191, Black Point, showing distinctly auriculate acroscopic margin of the pinnule bases; 5. LX1231, Curio Bay, with contracted basiscopic margin of the pinnule bases. All scale bars equal 10 mm.