340 
C.J. Burrow 
edges, and the wear on the denticulated surface, 
could indicate that it was supported by the jaw 
cartilage itself. 
Perhaps these elements represent a dentition 
intermediate between the climatiid pattern of rows 
of tooth whorls, and the denticulated jaw bones of 
ischnacanthids. Nearly all climatiid tooth whorls 
described to date (e.g., from Nostolepis striata and 
Climatius reticulatus, Figure 7B,C) have flattened, 
blade-like cusps attached to a concave base of 
relatively constant width. Latviacanthus Schultze & 
Zidek 1982 is an exception: the cusps have a 
circular parabasal section, but unlike other 
climatiids the tooth whorl base concavity is at right 
angles to the curvature of cusps. That is, the cusps 
are directed rostro-caudally rather than medially, 
as in all other described species (Figure 7D). 
Single teeth and tooth-like cones 
The single teeth (Figure 5A) from the Trundle 
beds are similar to those previously attributed to 
Gomphonchus (Gross 1957). However, Gross' 
'Domzahne' have a broad concave base, whereas 
those from the Trundle beds do not. These teeth 
may be ontogenetically 'young' versions of the 
robust Type II dentition cones. 
The two types of dentition cones, although 
bearing some similarity to phosphatized arthropod 
jaw fragments, appear identical to the cones 
described by Valiukevidius (1992), from the oral 
cavity of Poracanthodes menneri. The fragile Type I 
cones were possibly associated with the branchial 
arches. Although ValiukeviCius (1992) suggested 
that the Type II cones were similarly positioned, 
their robustness could indicate a position further 
forward in the mouth cavity. 
Many of the diverse acanthodian dental elements 
from the Trundle beds might derive from a single 
ischnacanthid species, but it is probable that they 
are from at least two species. As noted above, a 
large number of acanthodian scales has also been 
retrieved from the Trundle beds samples (Burrow 
in press); most of them have been assigned to 
"Nosfo/epis" guangxiensis Wang 1992 and a new 
species. The latter appears to belong to a group of 
acanthodians whose scales have a poracanthodid- 
type histology, but lack pore canal openings on the 
crown surface. Juozas Valiukeviiius (Lithuanian 
Geology Institute, Vilnius) has also studied 
acanthodian scales from late Lochkovian deposits 
of the Baltic states, with this type of histology 
(pers. comm.). 
A distinctive feature of all the tooth whorls and 
the jaw fragments is the arrangement of their 
cusps, with each large central cusp usually being 
flanked by two or three smaller cusps. Although 
the newly described element, the denticulated plate 
plus tooth whorl, and the multiple tooth whorl 
have a similar cusp arrangement to the other 
Figure 8 Hypothetical reconstruction of lower jaw of 
ischnacanthid from the Trundle beds, central 
New South Wales (individual elements not 
necessarily to scale), aj = anterior jaw bone 
fragment, gr = groove, mr = medial ridge, pt 
= palatine tooth, ws = symphysial tooth 
whorl; arrow indicates rostral direction. 
whorls and jaw fragments, the cusps of the former 
two have a circular parabasal section rather than 
the tri-carinate, or sub-triangular form of the cusps 
of the symphysial tooth whorls and jaw fragments. 
In an attempt to reconstruct the original anatomical 
positions of the various dental elements, these two 
types are kept separate. The proposed lower jaw 
