Pseudoctenis? ensiformis Halle, 1913

Pole, Mike, 2019, Middle-Late Jurassic plant assemblages of the Catlins coast, New Zealand, Palaeontologia Electronica (a 51) 23 (3), pp. 1-48 : 17-19

Pseudoctenis? ensiformis Halle, 1913

Figure 10

1886 Pterophyllum matauriensis Hector , p. 66, textfig. 30A.

1913 Pseudoctenis ensiformis Halle , pl. 6, fig. 8.

1917 Pterophyllum matauriensis Hector ; Arber, p. 52, pl. 9, fig. 2, pl. 12, fig. 1.

1934 Pterophyllum matauraense Hector ; Edwards, p. 99.

1989 Pseudoctenis ensiformis Halle ; Gee, p. 24, pl.

5, fig. 18.

2004 Pseudoctenis? ensiformis Halle ; Rees and Cleal, p. 37, pl. 11, figs. 1–4, text fig. 4.

Material. Haldane-Curio Bay Road: LX1199-1207, LX1210, LX1212, LX1214, LX1215.

Description. Leaf apparently once pinnate, pinnae arising laterally on rachis. Rachis 1–3 mm wide. Pinnae alternate, arising at c. 90°, separate or connected by basal lamina. Pinnae separated by 3–12 mm away from the rachis. Pinna margins entire, near-parallel beyond the base. Pinna bases expanded basiscopically and acroscopically. Pinna apices unknown. Pinnae> 45 mm long, width 6.5–9 mm beyond the base. Pinna venation prominent, 4–6 veins at pinna base, then commonly dichotomising, or sparsely anastomosing at varying distances from the rachis, to 8–9 veins across pinna width. Otherwise, veins. Basiscopic veins curving parallel to basiscopic margin, acroscopic veins parallel to acroscopic margin, then all becoming subparallel.

Remarks. A collection of frond fragments from a road cut behind Curio Bay have laterally inserted leaflets with expanded bases, both dichotomising and anastomosing veins and some striations on the rachis. On gross morphology these are likely the same species as Pterophyllum matauriensis, (Hector, 1886) and figured by Arber (1917), from the Mataura River, about 60 km inland from Curio Bay, although without mention of anastomosing veins.

Halle (1913) placed similar Jurassic material from Hope Bay, Antarctica, into Pseudoctenis ensiformis. He noted that Pseudoctenis has “occasional” anastomoses, Ctenis has regular anastomoses, whereas Pterophyllum has none. Halle (1913, p. 51) wrote that the characteristic feature of the Hope Bay material was the “widening of the pinnae at the base, both edges bending outwards and sometimes nearly joining those of the next lower and higher pinnae, thus forming a rounded sinus. To this feature corresponds a peculiarity in the course of the veins: the uppermost one or two veins in each pinna do not bend downwards

POLE: CATLINS COAST JURASSIC when joining the rachis, as do the others, but upwards, parallel with the distal edge of the pinna.” These specific features and the overall form of his material are very similar to the Curio Bay material and are probably conspecific.

Gee’s (1989) treatment of the Hope Bay material agreed with Halle’s (1913) placement in Pseudoctenis. She drew attention to Pterophyllum medlicottianum from India (Bose and Banerji 1981) that was similar in “general aspect, but differing in its unforking veins.” However, Rees and Cleal (2004), working on additional Hope Bay material, and following Harris (1964, 1969a), stated that both Pseudoctenis (a cycad) and Pterophyllum (a bennettitalean) “rarely if ever show anastomosing veins.” They placed some Hope Bay material into Ctenis, especially because of its frequently anastomosing venation. However, this is quite dissimilar to the Curio Bay material in having lobed margins. They provisionally kept Halle’s (1913) taxon in Pseudoctenis but suffixed it with ‘?’ to indicate they could not be sure it was a true cycad. The material studied by Rees and Cleal (2004) showed “mainly simple veins” in contrast to Gee’s, which she said bifurcated “occasionally and unpredictably, from 0 to 4, usually 3, times per pinna, often at the pinna base.” Rees and Cleal (2004) emphasised the similarities of the Hope Bay material with the Indian Pterophyllum medlicottianum, but widened the net to two other species, Pt. footeanum and Pt. morrsianum, which only differed in having sporadic dichotomies. They argued there was a “strong possibility” that all four taxa would prove synonymous.

Following Thomas (1930), Watson and Sincock (1992) restricted Pterophyllum to species that have known Bennettitalean cuticle, and specifically excluded anastomosing venation in their diagnosis. More recent work on the genera includes Pott and Krings (2010), who noted that Ctenis and Pseudoctenis are “similar in macromorphology” but (following Seward, 1911) they were “easily distinguishable” on account of anastomoses in Ctenis. They also emphasised the striate nature of the rachis in Pterophyllum.

The Curio Bay material is very fragmented, but even in those fragments the dichotomies and anastomoses are apparent, and hardly “rare” (although the anastomoses are not common enough to regard them as a Ctenis). They appear to add to the evidence of Pseudoctenis? ensiformis, Pterophyllum medlicottianum, Pt. Footeanum, and Pt. morrsianum being synonymous, with the degree of both dichotomies and anastomoses being variable. The Curio Bay material is regarded as Pseudoctenis? ensiformis, following Rees and Cleal (2004).

Figures

FIGURE 10. Pseudoctenis? ensiformis 1. LX1204; 2. LX1212; 3. LX1206; 4. LX1214. All Haldane-Curio Bay Road, scale bars equal 10 mm.