Biostratigraphy of Devonian microvertebrates 
419 
DEVONIAN 
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Thelodont indet. 
Cheiracanthoides comptus 
Nostoleois so. cf. N. costata 
N. costata 
Nostolepis so. 1 
sp. 2 
sp. 3 
Nostolepis spp. 
— 
Acanthoides sp. 
— 
Cladolepis sp. cf. C. gunnelli 
Ohiolepis 
?Phoebodontid indet. 
Chondrichthyan incertae sedis 
Arthrodire Indet. 
-- 
— 
TPtyctodontid Indet. 
Placoderm indet. 
Onychodontid indet. 
— 
?Dipnoan indet. 
— 
Cosmlne scales 
Palaeoniscoid indet. 
?Osteichthyan indet. 
Figure 2 Stratigraphic ranges of microvertebrates 
discussed in text. Heavy line is range in 
Broken River Group; light line is range 
reported from other localities. 
Stratigraphic level 
Givetian ( varcus Zone). 
Remarks 
All thelodonts have similar rounded head scales 
with undulating crown margins and radiating ribs, 
whereas trunk scales tend to be more distinctive 
(Turner 1986). The Broken River scale resembles 
head scales of Australolepis seddoni Turner and 
Dring, 1981 described from the Frasnian Gneudna 
Formation in the Carnarvon Basin of WA, in its 
rounded shape, bifurcated ridges radiating from a 
central plateau on the crown, and size (0.5 mm), 
but lacks the deep furrows on the crown and the 
stepped ridges on the vertical crown surface 
typical of this genus. However, the specimen 
cannot be unequivocally assigned to Australolepis. 
It also resembles head scales of the turiniid genus 
Turinia (e.g. Turner et al. 1981, figure 7G). For the 
present the Broken River scale is assigned in open 
nomenclature to Order Thelodontida. Turner and 
Dring (1981) suggest that Australolepis and Turinia 
are related, the former possibly being derived from 
the Early Devonian T. australiensis Gross, 1971. 
Turner (pers. comm.) considers Australolepis may 
be a neotenous form of T. australiensis. 
Description 
The scale has a gently rounded central crown 
extending outwards in five low, broad ridges. One 
anterior and one lateral ridge bifurcate slightly at 
the distal end (Figure 6M). The neck is smooth and 
low. The elliptical base is larger than the crown, 
with a wide rounded rim surrounding the central 
shallow pulp cavity (Figure 6N). 
Discussion 
Thelodonts, most commonly turiniids, have been 
reported from Australian localities ranging in age 
from close to the Siluro-Devonian boundary to the 
early Frasnian; these are listed by Long and Turner 
(1984) and Young (1993, 1995), and figured by 
Pickett et al. (1985), Turner et al. (1981), Young and 
Gorter (1981), Turner (1986, 1991, 1993), Young et 
al. (1987), and Long et al. (1988). No thelodont 
scales from the Broken River region are described 
or figured in the literature, but Young (1995) 
reports an endemic turiniid from the pesavis- 
sulcatus Martins Well Limestone, and Turner (1993) 
mentions, from the Broken River Group, a 
Lochkovian Turinia australiensis morphotype, and 
turiniid and nikoliviid-like scales of no specified 
age. 
Subclass Acanthodii Owen, 1846 
Order Climatiida Berg, 1940 
Family Climatiidae Berg, 1940 
Cheiracanthoides Wells, 1944 
Type species 
C. comptus Wells, 1944. 
Diagnosis 
Scales with flat or slightly convex crown. 
