Early Silurian phacopide trilobites from central Victoria, Australia
Author
Sandford, Andrew C.
Author
Holloway, David J.
text
Memoirs of Museum Victoria
2006
2006-12-31
63
2
215
255
https://museumsvictoria.com.au/collections-research/journals/memoirs-of-museum-victoria/volume-63-issue-2-2006/pages-215-255/
journal article
10.24199/j.mmv.2006.63.17
1447-2554
12210410
Ananaspis
Campbell, 1967
Type
species.
Phacops fecundus
Barrande, 1846
from the
Kopanina Formation
(Ludlow),
Koledník
,
Bohemia
, by original designation
.
Diagnosis
. Glabella moderately to strongly convex (sag., tr.), vertical or slightly overhanging anteriorly in dorsal view. Composite lobe expanding strongly forward, maximum width twice width at L1 or a little more. L2 commonly significantly shorter (exsag.) than L3. Eye of moderate to large size, lower edge situated in or slightly above lateral border furrow anteriorly and distant from lateral border furrow posteriorly, visual surface lacking strongly raised sclera (may be slightly thickened dorsally). Palpebral area as high as or higher than palpebral lobe. Fixigenal portion of lateral border furrow deep and continuous with posterior border furrow. Vincular furrow shallow to moderately impressed medially, commonly rather weakly notched laterally. Glabellar sculpture of bimodal tubercles lacking perforations and with superimposed and interspersed granules, doublure finely and densely granulate. Hypostome with short (sag.) posterior border having 3 angular points on margin. Pygidial pleural furrows deep and wide (exsag.), interpleural furrows distinct.
Figure 5. A–D,
Acernaspis
? sp., NMV P139804, cephalon, × 4, from PL385, Costerfield. E–G,
Phacopidae
gen.indet.3, NMV P139353, enrolled exoskeleton from PL1369, Springfield; E, × 4.0; F, × 4.5.
Remarks.
This diagnosis distinguishes
Ananaspis
from a number of closely related genera recognised since the work of
Campbell (1967)
.
Echidnops
Sandford, 2002
is the closest to
Ananaspis
but differs not only in having characteristic occipital and thoracic axial spines but also a much more deeply incised vincular furrow medially.
Paciphacops
Maksimova, 1972
is distinguished especially by the strongly raised sclera on the visual surface and the perforate glabellar tubercles, but in addition L1 is more depressed medially, the glabella is more raised and subquadrate in anterior profile, and the vincular furrow is deep medially.
Lochkovella
Chlupáč, 1972
(see also
Sandford, 2004
) differs from
Ananaspis
in that the cephalic tuberculation is finer and of more uniform size, the eye is situated very low on the cheek with its lower edge indenting the lateral cephalic border, the hypostome has a long (sag.) posterior border with five marginal denticles, the pygidial interpleural furrows are not as deep, and the pygidial granulation is coarser. Similar distinctions can be made with
Nephranomma
Erben, 1952
(see
Sandford, 2003
) which further differs from
Ananaspis
in lacking a vincular furrow medially and in having a distinctive scaly sculpture on the cephalic doublure. See the remarks on
Ivops
gen. nov.
for comparison of that genus with
Ananaspis
.