Zhen & Nicoll: Canning Basin Serratognathus bilobatus Fauna 
11 
Repetski (1982) were actually species of Diaphorodus and 
not congeneric with their revised “A.” deltatus. 
Kennedy (1980) proposed Diaphorodus as the replace¬ 
ment of Acodus and selected A. delicatus Branson & Mehl, 
1933 as the type species. In his revision of this species 
from the Early Ordovician Jefferson City Formation of 
Missouri, he recognized a seximembrate apparatus including 
the following types of elements: oistodiform (= M of our 
interpretation) represented by the form species Oistodus 
expansus Branson & Mehl, 1933 (see Kennedy, 1980, pi. 1, 
figs 20-22); acontiodiform (= Sa herein; see Kennedy, 1980, 
pi. 1, figs 14-17); drepanodiform (= ?Sc herein) represented 
by the form species Cordylodus simplex Branson & Mehl, 
1933 (see Kennedy, 1980, pi. 1, figs 9-11); distacodiform (= 
Sd herein) represented by the form species Paltodus distortus 
Branson & Mehl, 1933 (see Kennedy, 1980, pi. 1, figs 18, 
19); acodiform (= Pa herein) represented by the form species 
A. delicatus Branson & Mehl, 1933 (see Kennedy, 1980, 
pi. 1, fig. 3); and oistodiform (= ?Pb herein) represented by 
the form species Oistodus vulgaris Branson & Mehl, 1933 
(see Kennedy, 1980, pi. 1, figs 23-25). This multi-element 
species reconstruction is more or less agreeable with our 
current understanding of Acodus, except that the asym¬ 
metrical tricostate Sb element was absent in the type species 
of Diaphorodus defined by Kennedy (1980). However, 
Stouge & Bagnoli (1999) considered both Diaphorodus and 
Acodus (represented by ‘ 'Acodus ” deltatus) as valid genera. 
According to their illustrations of both Diaphorodus sp. A 
from the Cow Head Group of western Newfoundland (Stouge 
& Bagnoli, 1999, pi. 1, figs 1-7) and “A.” deltatus from the 
Kopingsklint Formation of Oland (Bagnoli et al., 1988; 
Stouge & Bagnoli, 1999, text-fig. 2), both Diaphorodus with 
a septimembrate apparatus and Acodus with a seximembrate 
apparatus have a nearly identical species apparatus and 
element morphology, except there is no Sa element for “A.” 
deltatus. As argued by Zhen et al. (2005, p. 306), we prefer 
to retain Acodus as a valid genus and consider Diaphorodus 
tentatively as a junior synonym of Acodus pending further 
studies of these and other closely related forms. 
Acodus deltatus? Linstrom, 1955 
Fig. 4S-X 
Acodus deltatus deltatus Linstrom.—McTavish, 1973: 39, 
pi. 1, figs 1-9, 12-14, text-fig. 3p-t. 
Material. 209 specimens from three samples (Table 1). 
Remarks. By assigning the Emanuel material to Acodus 
deltatus Lindstrom, 1955, McTavish (1973) defined A. deltatus 
as having a seximembrate apparatus. However, in a later 
revision of this Baltic species, Bagnoli etal. (1988) suggested 
that only some illustrated specimens referred to A. deltatus 
deltatus by McTavish (1973) might be doubtfully assignable 
to A. deltatus. Stouge & Bagnoli (1999) further indicated that 
the Emanuel material referred to A. deltatus was not conspe- 
cific with the type specimens from Sweden. As revision of 
the Acodus species described by McTavish (1973) and other 
related coniform taxa occurring in the Emanuel Formation is 
still in progress and will be presented elsewhere, the currently 
material is only tentatively referred to A. deltatus. 
Acodus? transitans McTavish, 1973 
Fig. 4M-R 
Acodus transitans McTavish, 1973: 41,42, pi. 1, figs 10, 11, 
15, 17, 19, 21, 24, text-fig. 3 m-o. 
Material. Four specimens from three samples WCB705/133 
(Table 1). 
Remarks. Acodus transitans is characterized by having a 
number of small and rudimentary denticles on the posterior 
process of its P and S elements, and represents a transitional 
form between Acodus and Prioniodus. Only a small number 
of specimens were available in this study (Fig. 4M-R). A 
comprehensive revision of Acodus species from the Emanuel 
Formation will be undertaken in a separate contribution. 
Drepanodus Pander, 1856 
Type species. Drepanodus arcuatus Pander, 1856. 
Drepanodus arcuatus Pander, 1856 
Fig. 5A-F 
Drepanodus arcuatus Pander, 1856: 20, pi. 1, figs 2, 4-5, 17, 
30, 731; Lofgren & Tolmacheva, 2003: 211-215, figs 2, 
3A-C, E-H, 5K-V, 6M-U, 7H-N, 8A-G {cum syn.)\ Zhen 
et al., 2004: 52-53, pi. 3, figs 1-12; Zhen et al., in press a: 
fig. 5A-N {cum syn.). 
Material. 95 specimens from three samples (Table 1). 
Remarks. Recently revised as having a septimembrate 
apparatus (Fofgren & Tolmacheva, 2003), D. arcuatus is 
a pandemic species widely distributed in various environ¬ 
ments from inner shelf to slope (or basinal) settings with a 
long stratigraphic range from the late Tremadocian to Fate 
Ordovician. It is a fairly common species in the Emanuel 
with specimens generally larger in comparison with those of 
other taxa. The cusp of the Sa element varies from proclined 
(Fig. 5B) to reclined (Fig. 5A), the Sd element has a twisted 
cusp and inwardly flexed anterobasal corner (Fig. 5C, D), 
the Pb element is characterized by having a strongly reclined 
cusp and a more or less square base in lateral view with basal 
margin curved into a right angle, and the Pa element bears 
a flared base with a shallower basal cavity (Fig. 5F). The 
symmetrical Sa element with a proclined cusp (Fig. 5B) is 
identical with the neotype and other illustrated specimens 
from western Russia and Sweden (Fofgren & Tolmacheva, 
2003, fig. 3A, B, fig. 60), and from the Honghuayuan 
Formation of Guizhou (Zhen et al., in press a, fig. 5B). The 
illustrated Sd, Pb and Pa elements are also comparable with 
those illustrated by Fofgren & Tolmacheva (2003) from 
Russia (fig. 3E-G) and Sweden (fig. 50,V), and those from 
the Honghuayuan Formation of Guizhou (Zhen et al., in 
press a, fig. 51, 5F, 5N). 
