38 
J.A. Long 
Figure 4 Boomeraspis goujeti gen. et sp. nov. Sp plate, as preserved. Camera lucida sketch; where the bone is missing 
the impression of the tubercular ornament in the rock is indicated, paratype WAM 93.7.5. 
from the same individual. The unit from which the 
fish plates were collected also contains isolated 
thelodont scales of Turinia antarctica, and plates of 
an as yet undetermined species of Bothriolepis. 
Boomeraspis therefore comes from within either the 
askinae or kohni biozones of Young (1988), and 
could be regarded as late Givetian in age. 
Description 
The four isolated plates of Boomeraspis (Figures 
2-4) may be used to give a tentative restoration of 
the overall shape of the trunk-shield (Figure 5), 
which assumes it was short and relatively high as 
in other groenlandaspidids. The trunk-shield had a 
prominent lateral ridge running from the PL plate 
which presumably continued on to the AL plate, as 
for other phlyctaeniids, such as Tiaraspis (Gross 
1962, Schultze 1984) and Phlyctaenius (Young 1983). 
Posterior dorsolateral plate 
The PDL (Figures 2A; 3A, B) measures 30 mm in 
rostrocaudal length along the dorsal margin, and is 
42 mm in maximum depth as measured from the 
top of the dorsal margin to the anteroventral 
overlap area dividing the PL and AVL plates. The 
dorsal margin of the PDL tapers vertically (Figure 
3B) suggesting that the two PDLs most likely met 
in contact underneath the MD plate as occurs in 
Groenlandaspis. The main lateral-line canal groove 
(He, Figure 3A) is inflected through an angle of 120° 
in the posterior third of the plate, and there is a 
prominent vertical ridge (ri. Figure 3A) running 
from the point of inflection to the ventral margin of 
the plate. The posterior division of the main lateral¬ 
line canal is less well defined and does not extend 
all the way to the posterior margin of the plate. 
The ADL overlaps the PDL (ov.ADL, Figure 3A) 
for about two thirds the anterior margin, but does 
not overlap that section of the PDL containing the 
anterior end of the main lateral line canal groove. 
The overlap margins for the MD, ADL and PL 
plates (ov.MD, ov.ADL, ov.PL; Figure 3A) are 
slightly narrower than that for the AVL plate 
(ov.AL, Figure 3A). The inner surface of the PDL is 
not known. 
Posterior lateral plate 
The PL is a relatively large and distinctive plate 
in Boomeraspis compared to that in other 
groenlandaspidids (Figure 6), extending for nearly 
the length of the PDL plate. It has a subrectangular 
outline with a strongly convex dorsal margin 
(Figures 2C, 3C), and a gently curved posterior 
margin that is oriented almost vertically. The 
prominent lateral ridge (tr.r. Figure 3C) originates 
in the posterior third of the plate and increases in 
thickness evenly towards the anterior margin, 
appearing as a thick ridge on the lateral lamina. 
The ventral external margin of the PL (where the 
dermal ornament terminates) is almost straight, 
and the overlap areas for the PVL and AL (ov.PVL, 
ov.AL, Figure 3C) are both quite extensive, much 
broader than the overlap margins on the PDL plate. 
Unlike Groenlandaspis the PL of Boomeraspis lacks a 
posteroventral extension of the overlap area for the 
PVL plate. The ornament is of regularly spaced 
tubercles which are largest in the posterodorsal 
comer of the plate. 
Posterior ventrolateral plate 
The PVL (Figure 2A) is known from part and 
counterpart, although the anterior margins are not 
well preserved. It is a narrow plate having a lateral 
lamina extending just over half the plate length. 
The posterior margin of the lateral lamina is evenly 
Figure 5 Boomeraspis goujeti gen. et sp. nov. Attempted 
restoration of the trunk shield based on the 
presence of the PVL, PL, PDL and Sp plates 
and their margins with neighbouring plates. 
Extent of the anterior trunk-shield plates and 
shape of the MD plate is based on 
comparsions with other groenlandaspidids. 
