Callograptus cf. niagarensis Spencer, 1878

Rickards, R. B., Chapman, A. J., Wright, A. J. & Packham, G. H, 2003, Dendroid and Tuboid Graptolites from the Llandovery (Silurian) of the Four Mile Creek Area, New South Wales, Records of the Australian Museum 55 (3), pp. 305-330 : 320-321

Callograptus cf. niagarensis Spencer, 1878

Fig. 16B

cf. 1878 Callograptus niagarensis Spencer , pp. 458, 463.

cf. 1909 Callograptus niagarensis Spencer ; Bassler, p. 13–14, fig. 15. (A full synonymy was given by Bassler [1909]).

Material. AM F114739 from F14, Bridge Creek.

Description. A single rhabdosome with the proximal region missing shows a series of diverging, wavy stipes, probably compound to judge from the striations along their length, unconnected by dissepiments and branching in an irregular manner. The stipes are rather broad proximally, about 0.50 mm, and more distally narrow to 0.25 mm, and appear to be constructed of long narrow tubes although the distal terminations of these tubes—the apertures—are not seen. Autothecae may be simple, denticulate spaced at? 20 in 10 mm.

Remarks. Callograptus niagarensis is known from only one specimen from the Niagaran dolomites and shales. The holotype appears to have a central dominant stipe: unfortunately this cannot be ascertained in our specimen. The wavy and diverging nature of the stipes is very similar in both specimens, but the Bridge Creek specimen has stipes which are a little more robust. Like the holotype, the Bridge Creek specimen shows bundles of tubes comprising the stipe, though not clearly. The original description suggests about 16 (auto)thecae in 10 mm (40 to the inch) which is not too different from our specimen which might be of the order of 20 in 10 mm.

Figures

Fig. 16. A, Callograptus ulahensis n.sp., AM F114760, holotype, BF15; B, Callograptus niagarensis, AM F114739, W885; C–E, Pseudodictyonema graptolithorum, respectivelyAM F114755,AM F114753 and AM F114645, all from F14. Scale bars 1 mm.