TREMADOC TR1LOBITES OF THE DIGGER ISLAND FORMATION,
WARATAH BAY, VICTORIA
By P. A. Jell
Museum of Victoria, 285-321 Russell Street, Melbourne, Victoria 3000
Abstract
Trilobites of the Digger Island Formation at Digger Island, 1 .5 km south of Walkerville on Waratah
Bay . South Gippsland are described and assigned an early Tremadoc age approximately equivalent to the
Kaineila meridionalis zone of Argentina. It is impossible to correlate directly with any known Australian
sequence but indirectly it is considered older than La 1 .5 zone of the Victorian graptolite sequence and ap-
proximately contemporaneous with the Oneolodus bkuspaius-Drepanodus simplex zone of western
Queensland. Four new genera, Natmus (Hystricuridae), Barachyhipposiderus (Harpedidae), and Landyia
and lictorispina (Pilekiidae) are erected with eleven new species, N. viclns, N. tuberus, B. logimus, L.
elizabelhae, V. holmesorum, Neougnosms eckurdti, Onychopyge parkerae, Pseudokainellu diggerensis,
Austraioharpes singleioni, A. expansus, and Proioplionwrops lindneri. New taxa left in open
nomenclature are referred 10 Pilekia. Tessalacauda, and the Hystricuridae. The Argentinian species
Micragnosius hoeki (Kobayashi, 1939), Slmmardia erquemis Kobayashi, 1937, and Leiostegium douglasi
Harrington, 1937 are identified,
Introduction
Digger Island is a small stack approximately
75 m in diameter, isolated from ihe mainland
above half-tide, and situated approximately
1.5 km south of Walkerville on the western
shore of Waratah Bay, South Gippsland; it
consists of brown, largely decalcified mud-
stones containing a rich faunule of trilobites,
brachiopods, gastropods, hyolithids, and
isolated cystoid plates. The ftrsi detailed ac-
count of the geology of this coastline (Lindner,
1953), to which readers are referred for details
of locality and geological setting, contained a
list of trilobiie identifications by O. P.
Singleton with nine specific and two generic
nomina nuclei. He assigned the faunule an early
Tremadoc age on the basis of identifications of
Leiostegium and Kaineila.
Singleton (1967) divided ihe formation infor-
mally into three parts; 1, a lower portion of
massive recrystallised grey limestone without
fossils except for a single nautiloid; 2, brown
decalcified mudstone with the trilobites and
associates; and 3, upper shales and muddy
limestones with orthoid brachiopods. On this
occasion he listed only six trilobites at generic
level and reiterated the Tremadoc age of the
beds.
Kennedy (1971) recorded Curdylodus rotun-
datus, Onetodus sp., and Drepanodus spp.
from the formation and concurred with the
Tremadoc age. These conodonls were derived
Memoirs ol the Museum Viclona,
No, 46, 1985.
from samples taken some distance along strike
from the trilobite locality; they come from near
locality 2 of Lindner (1953, fig. 3) (D. J. Ken-
nedy pets, coram.). Webby et al. (1981) using
Kaineila and Leiostegium made a direct correla-
lion between the Kainella-Leiostegium zone
(i.e. trilobite zone D of Ross (1951) and Hintze
(1953) in North America) and the Digger Island
Formation fauna; they also made an indirect
correlation between this North American zone
and the LA 1.5 zone of Psigraptus of Cooper
and Stewart (1979). At the same time, however,
they showed the Australian trilobiie fauna of
the prc-Lancefieldian Datsonian stage as
Leioslegiid/Kainellid/Ceratopygid (Ony-
chopyge) whereas the Warrendian (contem-
porary of the Lancefieldian), had only a
Leiostegiid component mentioned. If the
association of leiostegiid with kainellid is so im-
portant then the text and chart of Webby et al.
(1981) seem incongruous.
Jones et al. (1971, p. 23) suggested a late
Tremadoc to early Arenig age for the Digger
Island Formation.
None of the attempts to date the trilobite
faunule has been based on detailed taxonomic
study as evidenced by Ihe description herein of
18 separate taxa; all were collected in
decalcified mudstone in the middle of the Dig-
ger Island Formation, on the northern and
western sides of Digger Island below or just
above high tide level (Fig. 1).
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BioStor
