Austrosequoia novae-zeelandiae ( Ettingshausen, 1887 ) Mays and Cantrill

Mays, Chris, Bevitt, Joseph J. & Stilwell, Jeffrey D., 2017, Pushing the limits of neutron tomography in palaeontology: Three-dimensional modelling of in situ resin within fossil plants, Palaeontologia Electronica 196 (9), pp. 1-12 : 4-6

Austrosequoia novae-zeelandiae ( Ettingshausen, 1887) Mays and Cantrill

Figure 2 , Appendix

v. 2017 Austrosequoia novae-zeelandiae ( Ettingshausen, 1887) ; Mays and Cantrill in Mays, Cantrill, Stilwell, and Bevitt, (in press), figs. 2, 3, 6.

See Mays et al. (2017) for additional synonymy.

Description. Ovulate cone, woody, globose to ellipsoidal, 11.8 mm diameter, axial length not preserved, 11 preserved, helically arranged bract-scale complexes. Cone axis slender (1.4 mm in diameter), and enervated by at least two longitudinal resin canals. Bract-scale complexes are obtriangular in outline, peltate with pedicellate base, have a truncated apex and no apical protuberance. Complexes are 3.8–4.7 mm long, flaring at peltate distal head to 4.1–5.6 mm wide (N = 8). Ovuliferous scales and bracts are not clearly demarcated. Dorsal surface of complex has a longitudinal furrow/groove (<0.75 mm deep), bisected by a medial ridge, which is especially prominent on the lateral margins. Complexes have endogenous resin pockets; these tend to be elongated towards pedicellate base and subspherical towards distal margin. Minimum bract-scale complex resin volume was 0.9–1.6% (as a proportion of total cone bract-scale complex volume; see Present Limitations and Future Directions). There is no evidence of resin within associated fertile shoot; morphology of shoot not well-preserved enough to provide further details here.

Specimen examined. PL1227 (field code TPF0135-1).

Remarks. Axial length was not measurable, nor were all bract-scale complexes preserved, because of erosional truncation. All preserved characters of this specimen conform to previous specimens of Austrosequoia novae-zeelandiae from the Tupuangi Formation, Chatham Islands (Mays et al., 2017). However, the following additional characters were revealed by neutron tomography ( Figure 2.3 ): 1) small endogenous resinous cells/pockets within the complexes; and 2) prominent resin reservoirs within the cone axis, delineating at least two resin canals (each up to 39% of the total axis diameter). These were revealed by the extraordinarily high neutron attenuation of fossil resin, relative to the surrounding coalified plant tissue ( Table 2).

Stratigraphic range. The section of the stratigraphic succession from which the fossil was sourced has been correlated to the Ngaterian New Zealand chronostratigraphic stage ( Mays and Stilwell, 2013), corresponding to the Cenomanian global stage (100.5–93.9 Ma; Raine et al., 2015). This species has previously been recorded from Cenomanian strata of the Chatham Islands (Mays et al., 2017), and?Turonian–Campanian strata of mainland New Zealand ( Pole, 1995).

Occurrences. Zealandia: 1) Waihere Bay, Chatham Islands (Mays et al., 2017); and 2) Shag Point, New Zealand ( Ettingshausen, 1887).

Figures

FIGURE 2. Austrosequoia novae-zeelandiae (Ettingshausen, 1887) Mays et al., 2017, PL1227. 1) Transverse section of a partially exposed, desiccated ovulate cone. 2) Neutron tomographic reconstruction largely encapsulated in sedimentary matrix, white indicates high neutron attenuation, oblique-transverse view. 3) Volume rendering of neutron tomographic reconstruction, RNA = Relative Neutron Attenuation, grid texture on RNA spectrum indicates relative transparency, regions of highest neutron attenuation represent in situ resin within cone axis and minor enclaves of resin near the distal ends of the bract-scale complexes, desiccation exhibited by large gaps in coalified organic remains (blue/green), oblique-transverse view. 4) Greyscale histogram from neutron tomographic reconstruction of PL1227 (16-bit) these values represent the neutron attenuation of the reconstructed volume, colours and transparency textures as per Figure 2.3, threshold values presented in Table 2, the spectrum has been cropped at the extremes for this graphical representation. See Appendix for an animation of the virtually extracted specimen illustrated in Figure 2.3.