Lower Devonian acanthodians from New South Wales 
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Figure 3 Dentigerous jawbone fragments from Trundle beds, central New South Wales. A,B, posterior ?upper jaw 
fragment MMMC02280: A, lateral view and B, occlusal/medial view; C,D, mid jaw fragment MMMC02279: 
C, medial view, D, close-up of tubercles on medial ridge in C; E, anterior jaw fragment MMMC02278. Scale 
bars = 0.1 mm; arrows indicate rostral direction; Figures C,D,E are SEM photographs of uncoated 
specimens. 
complete or best preserved specimen of each type 
is first described and figured, followed by brief 
details of other specimens of the same type. 
Posterior jaw bone fragment (Figure 3A,B) 
This fragment (MMMC02280) is 2.4 mm long, 1.5 
mm deep and 1.0 mm wide at the anterior, broken 
edge. The top edge of the bone is narrow, and the 
anterior section bears small rounded denticles. A 
small, flat, ledge-like process juts out medially 
towards the posterior end; the end of the bone then 
curves gently round to the bottom edge. On the 
medial side, a ridge starts at the anterior edge of 
the ledge-like process, increasing in size as it 
sweeps down and forward to form the medial side 
of the basal concavity for the jaw cartilage. The 
lateral side of the bone is slightly convex top to 
bottom, and bears small, rounded denticles in the 
upper half. 
A second similar fragment is 3.0 mm long, with 
the same shape and relative robustness, and is 
contralateral to the illustrated jaw fragment. 
Dentigerous jaw bone (Figure 3C,D) 
The best preserved jaw bone fragment 
(MMMC02279) is 4.0 mm long, 0.7 mm wide 
posteriorly and increasing to 1.0 mm wide 
anteriorly, and is approximately 1.0 mm deep. The 
