22 
Records of the Australian Museum (2009) Vol. 61 
resembles the Sa, but is asymmetrical with a more convex 
outer lateral face (Fig. 10E-G). The Sc element is identical 
with the asymmetrical element represented by the holotype of 
the species from the Liangjiashan Formation of North China 
(An et al., 1983, pi. 12, fig. 26) with a convex outer lateral 
face and concave inner lateral face and with several costae 
(2 to 4) near the anterior margin (Fig. 10H-K). Zhen et al. 
(in press a, fig. 9G-F) reported the occurrence of this species 
in the Honghuayuan Formation in Guizhou. The Sc element 
recently illustrated from the Honghuayuan Formation in 
Guizhou (Zhen et al., in press a, fig. 9G-I) shows a more 
compressed base, and the Sa element (Zhen et al., in press a, 
fig. 9J-F) has the base less extended posteriorly, with costae 
on the lateral face more towards anterior. 
Semiacontiodus Miller, 1969 
Type species. Semiacontiodus nogamii Miller, 1969. 
Semiacontiodus sp. cf. Semiacontiodus 
cornuformis (Sergeeva, 1963) 
Fig. 15L-T 
Scolopodus cornuformis Sergeeva.—An, 1987: 183, pi. 7, 
figs 10-11, 13-16; Ding etal. in Wang, 1993: 202, pi. 5, 
fig. 33; Zhen et al., in press a: fig. 9D-F. 
Material. 26 specimens from three samples (Table 1). 
Remarks. Three morphotypes of this species are recognized 
in the Emanuel samples representing a symmetry transition 
series including symmetrical Sa (Fig. 15F,M), asymmetrical 
Sb (Fig. 15N,0), and strongly asymmetrical and laterally 
more compressed Sc (Fig. 15P-T) elements. Although these 
specimens have relatively shorter bases, they otherwise 
resemble those of S. cornuformis (Sergeeva, 1963), which 
was revised as consisting of a septimembrate apparatus 
(Fofgren, 1999). 
Serratognathus Lee, 1970 
Type species. Serratognathus bilobatus Lee, 1970. 
Serratognathus bilobatus Lee, 1970 
Fig. 11A-L 
Serratognathus bilobatus Lee, 1970: 336, pi. 8, figs 6, 7; 
Metcalfe, 1980: pi. 1, figs 16-19; An, 1981: pi. 2, fig. 26; 
An & Ding, 1982: pi. 5, fig. 25; An et al., 1983: 149, pi. 
16, figs 20-22, pi. 17, figs 1, 2; An, 1987: 189, 190, pi. 
18, fig. 11; Ding, 1987: pi. 6, fig. 16; An & Zheng, 1990: 
pi. 7, fig. 13; Ding et al. in Wang, 1993: 207, pi. 20, fig. 
5; Chen & Wang, 1993: fig. 2Q, 2U; Wang et al, 1996: 
pi. 2, figs 1-7,9; Nicoll & Metcalfe, 2001: fig. 6.19-6.22; 
Metcalfe, 2004: pi. 2, figs 9-10. 
Material. Seven specimens from three samples (Table 1). 
Diagnosis. Species of Serratognathus with a trimembrate 
apparatus, including symmetrical Sa, asymmetrical Sb, 
and strongly asymmetrical Sc elements; all elements semi- 
conical in outline with fan-shaped array of small, closely 
spaced denticles along anterior and lateral edges of overlap¬ 
ping laminar layers; cusp small, posteriorly positioned and 
anterolaterally enclosed by up to 16 vertically overlapping 
laminar layers, which are anterobasally divided by a broad 
median groove into two lobe-like lateral processes; basal 
cavity absent. 
Description. Trimembrate apparatus, including symmetrical 
Sa, asymmetrical Sb, and strongly asymmetrical Sc elements 
which form a symmetry transition series; each element 
semi-conical in outline, formed by upwardly overlapping 
layers, resembling a half-cut onion; composed of the cusp 
and a gently posterolaterally extended lobe-like lateral 
process on each side. Cusp small or indistinctive, weakly 
compressed laterally with a broad posterior face, and the 
anterior margin embedded in up to 16 surrounding overlap¬ 
ping layers, which are bordered by small, closely spaced 
denticles along the anterior and lateral margins. Discrete 
denticles surround the cusp in a semicircle, representing 
the anterolateral edge of each overlapping layer. Node-like 
denticles weakly developed on posterior face, may be absent 
towards the base (Fig. 11B, E, G, I); fine striae microstruc¬ 
ture best developed on the posterior face in the area above 
the basal margin (Fig. 11 I, J). Denticulate anterior margin 
of each layer turned upwards. Basal face smooth, wide, and 
distally arched; crescentic in outline in basal view; bisected 
by anteroposteriorly directed median groove extending 
anterobasally to separate into two lobes underneath each 
lateral process. Basal cavity absent; basal end of the cusp 
represented by a small ring-like node (Fig. 1 IK), but in one 
specimen basal cavity represented by a small, shallow pit 
underneath the cusp (Fig. 1 IB). 
Sa element symmetrical, outline crescentic in upper view 
with convex anterior face and concave posterior face, and 
tower-like in anterior view (Fig. 11 A). Cusp small, located 
posteromedially with a short lobe-like process on each 
side, which extends posterolaterally; in anterior view, two 
processes separated anterobasally by a prominent rather deep 
median groove (Fig. 11A). Basal face smooth, bisected by 
the median groove into two symmetrical lobes. 
Sb element (Fig. 11B-F) like Sa, but asymmetrical; inner 
lateral process shorter in posterior view (Fig. 1 IB), extending 
laterally with basal margin nearly horizontal; outer lateral 
process longer extending posterolaterally (Fig. 11C). Basal 
margin of the two processes forming an angle of 125° or 
more in the upper view (Fig. 1 IE). Basal face asymmetrical, 
with a longer lobe under outer lateral process and a shorter 
lobe under inner lateral process. One specimen (Fig. 1 IB) 
exhibits a small and shallow basal cavity. 
Sc element (Fig. 11G-L) similar to Sb, but strongly 
asymmetrical with longer and more strongly posteriorly 
extended lateral processes. In upper view, the basal margins 
of the two lateral processes form a rather narrower angle 
of about 70-80° (Fig. 11G, L); outer lateral process longer 
(Fig. 11G, L). 
Remarks. Lee (1970) illustrated two specimens of 
Serratognathus bilobatus from the Dumugol Formation of 
South Korea, with the figured holotype (Lee, 1970, pi. 8, fig. 
7a-d) assignable to the asymmetrical Sb element defined 
herein and the other figured paratype (Lee, 1970, pi. 8, fig. 
6) is a symmetrical Sa element. Both specimens are identical 
with those from the Emanuel Formation. Serratognathus 
bilobatus differs from S. diversus An, 1981 (Figs 12-14) 
from the Honghuayuan Formation of South China mainly in 
having a smaller, often indistinct, cusp (Fig. 11G, H). 
