A new species of Peribrissus (Echinoidea, Spatangoida) from the middle Miocene of South Australia 
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Table 1. Comparison of diagnostic features of Peribrissus janiceae sp. nov. with those of the type species of the genus, P. saheliensis Pomel, 1883, 
and P. sotgiai Giorgio, 1923. 
Diagnostic feature 
Peribrissus janiceae sp. nov. 
Peribrissus saheliensis Pomel 
Peribrissus sotgiai Giorgio 
Width/length ratio of test 
89.7%TL 
Similar 
Similar 
Maximum width location 
Marginally posterior at 
54.3%TL 
Marginally anterior, approx. 
45%TL 
Similar to P. saheliensis 
Height//length ratio of test 
66.4%TL 
Not known 
Approx. 54%TL 
Maximum height location 
Slightly anterior at 44.8% 
Well anterior but posterior of 
apical disk, approx. 30%TL 
Well posterior, approx. 
68%TL 
Anterior lateral profile 
High, vertically convex 
Slopes forward from apex at 
approx. 35° 
Similar to P. janiceae 
Posterior lateral profile 
High vertical truncation 
Oblique truncation 
Oblique truncation 
Adoral surface lateral profile 
Flat, posterior of peristome 
Unknown (type specimen 
compressed) 
Slightly swollen posterior of 
centre 
Sulcus 
Max. depth/width ratio approx. 
1:4.6, occurs below ambitus 
Figured much deeper with a 
depth/width ratio of approx. 1:2.2 
Figured far shallower and 
wider than P. janiceae 
Apical system location and type 
21%TL, ethmolitic, 3 
gonopores (none in plate G2) 
Approx. 33%TL, detail of apical 
system unknown (Pomel 1887). 
Stefenini (1911) incorrectly 
assumes 4 gonopores. This 
repeated by Mortensen (1950) 
and Fisher (1966). 
Approx, average of 2 
specimens 25%TL, 
ethmolitic. Giorgio’s 
description refers to 4 
gonopores but states the pore 
in G2 almost atrophied 
Ambulacmm III, marginal 
tubercles 
Not unduly prominent, situated 
just outside adradial sutures 
Similar to P. janiceae 
Larger, far more prominent 
with rows further apart 
Detail of petals 
Straight, parallel sided and 
sunken 
Similar, but probably shallower 
Similar 
Length differentiation paired 
petals 
Anterior petals 138% longer 
than posterior ones 
Similar to P. janiceae 
More equal, but posterior 
petals still shorter than 
anterior ones 
Anterior paired petals 
divergence angle 
175° 
Approx. 13 5° 
Described as 140°. Giorgio’s 
figures, however, suggest 
divergence wider 
Posterior paired petals 
divergence angle 
315° 
Approx. 295° 
Similar to P. janiceae 
Peristome 
Reniform and slightly sunken 
Insufficient information for 
comparison 
Insufficient information for 
comparison 
Periproct 
Vertically elliptical at top of 
posterior truncation 
Semicircular, assumed high on 
posterior truncation 
Elliptical (axis not clear), 
high on posterior truncation 
Fascioles, marginal and 
semipetalous 
Marginal fasciole occurs just 
above sloping ambitus and is 
joined by semipetalous fasciole 
at right angles behind and 
below anterior paired petals 
Similar, but with semipetalous 
fasciole shown angled forward at 
junction with marginal fasciole, 
apparently due to less oblique 
divergence of anterior petals 
Insufficient information for 
comparison, as stated to be 
only visible in some places 
Apical system situated well anterior of centre at 21.0% TL 
from anterior ambitus to centre of disk and is level with 
proximal end of paired petals. Ethymolitic with three 
gonopores, no gonopore in plate G2, and approximately 60 
hydropores fairly evenly spaced over the latter’s length. 
Paired petals straight, parallel sided, sunken, open distally 
and devoid of tubercles. Anterior paired petals 138% longer 
than posterior pair, extending 50% of the radius (28.0%TL) 
measured along the surface of the perradial suture from centre 
of ocular to ambitus. Anterior paired petals diverge at 175° and 
contain 23/24 pore pairs, posterior petals 315° and 20/21 pairs. 
Outer pores elliptical, inner pores slightly smaller and more 
tear shaped. Zone between inner and outer pores approximately 
equal in width to outer pores, pairs not conjugate. Interporiferous 
zone marginally narrower than poriferous zones. 
Ambulacrurum III depressed for its full length below 
