Abstract:
Graptolites from the Yass district of New South Wales include important material from: low in the
Black Bog Shale; from the Yarwood Siltstone Member; 2 levels high in the Black Bog Shale; 2 levels low
in the Rosebank Shale; low in the Cowridge Siltstone; and in the lower part of the Elmside Formation.
The faunas from the lower 4 levels are late Ludlow (early Late Silurian), and the higher 4 levels are
Prídolí (late Late Silurian).Twenty-seven graptolite taxa, a considerable increase on previous records
from Yass, have been identified in the late Ludlow and Prídolí of the district. These taxa enable the
Ludlow-Prídolí boundary to be identified some 20 m above the base of the Rosebank Shale (Booroo Ponds
Group); our stratigraphically highest collection from the Elmside Formation is latest Prídolí, supporting
the previous placement of the base of the Devonian approximately midway through the Elmside
Formation (Barambogie Group). The following graptolite Biozones have been identified: praecornutus,
cornutus,parultimus, bouceki and transgrediens. Twenty Yass taxa are described, including the new
species Bohemograptus paracornutus, Pristiograptus shearsbyi, Neocucullograptus? yassensis and the new
subspecies Monograptus perneri elmsidensis and M. formosus jenkinsi. The following are recorded from
Australia for the first time: Bohemograptus praecornutus Urbanek, 1970; Crinitograptus operculatus
Münch, 1938; and Pristiograptus kolednikensis Pribyl, 1940. Dictyonema sp. cf. D.sherrardae Rickards
et al., 1995 and D. elegans Bulman, 1928 are considered late evolutionary derivatives of long-ranging
dendroid species. Linograptus posthumus introversus Rickards & Wright, 1997 is interpreted as a short-
lived, late Ludlow offshoot of the long-ranging L. p. posthumus Richter, 1875. Bohemograptus
praecornutusis regarded as the ancestor of B. paracornutus, the B. cornutus evolutionary plexus being
recognised for the first time in Australia. Late forms of Pristiograptus dubius (Suess,1851) probably
gave rise to P. shearsbyi n.sp. and Pristiograptus kolednikensis probably arose in the basal Prídolí from
the late Ludlow P. fragmentalis (Boucek, 1936). Some material described and discussed by Brown &
Sherrard (1952) is reinterpreted. Bohemograptus paratenuis n.sp. is proposed for material assigned by
Urbanek (1970) to B. bohemicus aff. tenuis (Boucek, 1936); this species is known only from Poland.
