Cladophlebis, Brongniart, 1849

Pole, Mike, 2019, Middle-Late Jurassic plant assemblages of the Catlins coast, New Zealand, Palaeontologia Electronica (a 51) 23 (3), pp. 1-48 : 7-8

Genus CLADOPHLEBIS Brongniart, 1849 , emend. Seward, 1894

Remarks. Cladophlebis is probably the most ubiquitous plant fossil in the New Zealand Jurassic but despite this, nomenclature remains unclear. The first publication of plant fossils from New Zealand (Unger, 1864) describes Polypodium hochstetteri , material which would now be regarded as Cladophlebis . By the time of Arber (1917) and Edwards (1934) at least five species of Cladophlebis apparently, were known in the New Zealand Jurassic; Cladophlebis australis , C. sp. cf. C. albertsi , C. antarctica , C. denticulate , and C. cf. reversa . Arber (1917, p. 31) regarded C. australis as the “most abundant of all species, without exception” in the New Zealand Jurassic. Then, based on one of Arber’s (1917, pl. 4 fig. 1) figures of Cladophlebis australis, Frenguelli (1947) erected a new species, Cladophlebis patagonica . In this taxon, the pinnules were distinctly elongate and well-separated from each other, and with lateral veins that mostly bifurcated a single time, except for one of the two basal veins that could sporadically dichotomise again. He reserved C. australis for specimens in which double-bifurcation was prominent (Retallack, 1983, noted that in this sense, C. australis would be generally restricted to the Triassic). McQueen (1956) accepted C. australis and remarked on the variability of the pinnule wing.

Herbst (1966) formalised the description of Cladophlebis patagonica but illustrated it with a line drawing of a frond entirely different from Frenguelli’s (1947) concept of the species. In Herbst’s (1966) illustration, the pinnules are (or are almost) touching each other. The veins all fork once, except for two possible indications of a second dichotomy. The veins are also dense and markedly reflexed. In his later review of Argentinian Cladophlebis , his figure (Herbst, 1971, fig. 3) of C. patagonica again showed neither the well-separated pinnules nor the basal twice-forking venation that was the basis for Frenguelli (1947) to separate a new species.

Johnston et al. (1987) argued that New Zealand Cladophlebis that had once-forking secondary venation had been commonly misidentified as C. australis , and instead, compared most records with C. indica (Sahni and Rao, 1933) . Included in their concept of C. cf. C. indica was Arber’s (1917) pl. 4 fig. 1 specimen, which Frenguelli (1947) had figured as C. patagonica . The specimen of C. cf. C. indica illustrated by Johnston et al. (1987) from the Jurassic of Nelson is only the apex of a single pinnule, so does not show the full shape, pinnule separation, or basal venation that would be required to distinguish C. indica from Frenguelli’s C. patagonica . However, Raine (1987) figured more complete material from the Jurassic of the Manganui Valley in the North Island with the closely spaced pinnules and consistently once-forking venation as in C. indica . Most recently, Thorn (2001) listed Cladophlebis cf. C. australis from Kawhia Harbour in the North Island.

Cladophlebis species occur in the Jurassic of Hope Bay and Botany Bay, Antarctica. Following the pioneering work of Halle (1913) there have been two major works revising the floras, by Gee (1989) and Rees and Cleal (2004). Both recognised only one entire-margined species, Halle’s C. oblonga . Gee (1989) specifically regarded it as distinct from similar species elsewhere, such as C. australis , C. patagonica and C. indica .

A practical problem with the Catlins Coast material is that the venation is often faint and it is usually not straightforward to determine whether the veins dichotomise once or twice. Typically, the margins are also vague, and it is difficult to be sure that a slightly dentate margin is not an artefact of preservation. Despite this, the material I have collected appears to be entire-margined, with mostly singly-forking veins, but there are some that fork again. This later feature recalls Cladophlebis patagonica , although it is not restricted to the most basal veins as per Frenguellli (1947). However, many specimens have the remarkably long pinnules, and pinnules with a high length/width ratio, which Frenguelli associated with C. patagonica . In addition, most specimens have pinnules in which the base broadens apically. This feature is visible in Arber’s (1917, pl. 4, fig. 1) specimen that Frenguelli (1947) placed in C. patagonica , but is absent on Herbst’s (1966, 1971) specimen. Apically broadening pinnules were also associated with C. denticulata by both Gee (1989) and Birkenmajer and Ociepa (2008). However, both papers also agreed that the pinnule length/width ratio of C. denticulata was <3. Thus, even if the nature of the margin is obscure, the larger pinnule length/width ratio for the Catlins material rules out C. denticulata in most cases. In some of the Catlins Coast material the pinnae actually join to form a slight wing along the rachis, a feature noted for the Owaka Creek material by McQueen (1956). Raine’s (1987) North Island C. indica have a distinct wing between the pinnules, but do not show apically broadening pinnule bases. The concept of C. indica provided by Sahni and Rao (1933) was that the pinnules were mainly non-entire. However, the figures of the original Pecopteris indica (Oldham and Morris, 1863, pl. 27) do not show non entire margins, but many of the pinnules appear to overlap (similar to some extant New Zealand Blechnum ) rather than be joined by a wing, and in the only figure showing a wing (2a) veins from adjacent pinnules meet in the sinus. These later two features suggest this material is distinct from any New Zealand fossils.

The present Catlins material agrees very well with that illustrated by Unger (1864) as Polypodium hochstetteri from the Waikato, a validly published name according to Mildenhall (1970). The drawing of this specimen appears to have taken care to show the sporadic second forking of veins, a wing between pinnules, and some apical broadening of the base.

Arber’s specimen with well-separated pinnules that Frenguelli used as the basis of Cladophlebis patagonica appears to be aberrant, and the specimen then chosen by Herbst (1971) to represent the species differs from the New Zealand material in its dense and strongly curved veins.

However, based on the pinnule shape, instances of doubly-forking venation, at least some of the Catlins coast material is regarded as Cladophlebis patagonica . None of the material is consistent with C. australis , although C. indica cannot be ruled out.