Australian Museum Journal Dendroid and tuboid graptolites from the Llandovery (Silurian) of the Four Mile Creek area, New South Wales

Shortform:
Rickards et al., 2003, Rec. Aust. Mus. 55(3): 305–330
Author(s):
Rickards, R. B.; Chapman, A. J.; Wright, A. J.; Packham, G. H.
Year published:
2003
Title:
Dendroid and tuboid graptolites from the Llandovery (Silurian) of the Four Mile Creek area, New South Wales
Serial title:
Records of the Australian Museum
Volume:
55
Issue:
3
Start page:
305
End page:
330
DOI:
10.3853/j.0067-1975.55.2003.1387
Language:
English
Date published:
10 December 2003
Cover date:
10 December 2003
ISSN:
0067-1975
CODEN:
RAUMAJ
Publisher:
The Australian Museum
Place published:
Sydney, Australia
Subjects:
SILURIAN; PALAEONTOLOGY
Digitized:
10 December 2003
Available online:
10 December 2003
Reference number:
1387
EndNote package:
EndNote file
Title page:
Title page (12kb PDF)
Complete work:
Complete work (5418kb PDF)

Abstract

Twenty-four taxa of Llandovery dendroid and tuboid graptolites from the Cadia Coach Shale and Glendalough Formation in the Four Mile Creek area, S of Orange, New South Wales, provide the most diverse benthic graptolite record known from rocks of this age. Eighteen new taxa described here are: the dendroids Dendrograptus avonleaensis, D. ashburniaensis, Dictyonema williamsae, D. paululum australis, D. jenkinsi, D. muirae, D. warrisi, Callograptus bridgecreekensis, C. rigbyae, C. ulahensis, Stelechocladia praeattenuata, Acanthograptus praedeckeri, A. praedeckeri minimus, Thallograptus christoffersonae, Koremagraptus obscurus and C. elegantulus; and the tuboids Reticulograptus thomasi and Cyclograptus? australis. The six previously-named taxa are: Dictyonema cf. delicatulum Lapworth, D. falciferum Bulman, D. venustum Lapworth, Callograptus cf. niagarensis Spencer and Pseudodictyonema graptolithorum (Pocta); and one species in open nomenclature is Dictyonema sp. 1. These occur with graptoloids at Four Mile Creek, allowing precise stratigraphic correlation of the faunas with probably the gregarius Biozone (middle Llandovery), and the crispus and griestoniensis Biozones (late Llandovery) of Europe. Criteria for dendroid classification are discussed and some implications for reconstructing the evolutionary history of the group are reviewed. The evolution of anastomosis and dissepiments is seen as of prime importance in the development of three major changes in the Middle to Upper Cambrian, which are: 1, ordered Dendrograptus ? Callograptus: 2, ordered Dendrograptus ? Dictyonema; 3. ordered Dendrograptus ? Desmograptus. The development of compound stipes, while important in defining the Acanthograptidae, is recognized as having arisen independently in three other lineages.

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