Systematic palaeontology
The taxonomic classifications of Becker (2002) and Liebau (2005) are used in
the paper. Abbreviations: CA, cardinal angles; ACA, anterior cardinal angle;
PCA, posterior cardinal angle; AB, anterior border; PB, posterior border; DB,
dorsal border; ADB, anterodorsal border; PDB, posterodorsal border; VB,
ventral border; AVB, anteroventral border; PVB, posteroventral border; L,
maximum length; H, maximum height; W, maximum width.
Family Aparchitidae Jones, 1901
Genus Aparchites Jones, 1889
Aparchites? productus Polenova, 1960
(Plate 1, fig. 1)
1960 Aparchites productus Polenova: 8–9, pl. 1, fig. 2.
Material: Two carapaces and two
valves.Description:
Equivalve carapace. DB straight and long; CA obtuse. AB rounded with a large
radius of curvature and a maximum convexity located between first third of
H and mid-H; VB regularly curved; PB with a relative small radius of
curvature and a maximum convexity located below mid-H. Surface smooth.
Dimensions:
L=0.76–0.80 mm, H=0.61–0.65 mm,
W=0.47–0.51 mm.Occurrence: Late Devonian, Guangxi (Xiangtian and
Wuzhishan formations of Yangdi section), South
China.Remarks: In
lateral outline, the specimens resemble Aparchites productus
Polenova, 1960 from the Middle Devonian of the Russian Platform (Polenova,
1960). The specimens figured by Polenova (1960, Plate 1, figs. 2a, b), as
well as our specimens, do not posses the adventral structure characteristic
of the genus. Therefore, our species is assigned to Aparchies with
doubt.
Aparchites? sp.
(Plate 1, fig. 2)
Material: Two carapaces and two
valves.Description:
DB straight to slightly curved; AB and PB rounded; VB regularly concave; left
valve slightly overlaps the right along the free margins. Surface
smooth.Dimensions:
L=0.36–0.42 mm, H=0.30–0.37 mm,
W=0.24–0.27 mm.Occurrence: Late Devonian, Guangxi (Wuzhishan
Formation of Yangdi section), South China.Remarks: In outline, the specimens resemble
Aparchites circularis Wei, 1983 from Early Devonian of Sichuan,
South China (Wei et al., 1983), but poor preservation makes further
identification impossible.
Family Uncertain
Genus Parasargentina Zheng, 1982
Parasargentina sp.
(Plate 1, fig. 3)
Material: Two carapaces and four
valves.Description:
Round ovoid carapace, DB straight to slightly arched; AB and PB rounded; VB
regularly concave; left valve slightly overlaps the right along the free
margins. Surface smooth.Dimensions: L=0.51–0.56 mm, H=0.36–0.40 mm,
W=0.24–0.27 mm.Occurrence: Late Devonian, Guangxi (Xiangtian and
Wuzhishan formations of Yangdi section), South
China.Remarks: In
lateral outline, the specimens could be attributed to the genus
Parasargentina Zheng, 1982, for their nearly straight dorsal margin
and rounded AB, but poor preservation forbids further assignation.
Family Scrobiculidae Posner, 1951
Genus Scrobicula Posner, 1951
Scrobicula cf. rotundata Polenova, 1952
(Plate 1, fig. 4)
Material: Three carapaces and two
valves.Description:
DB slightly curved; AB rounded with a large radius of curvature and a maximum
convexity located a little below mid-H; VB nearly straight on left valve
and regularly convex on right one; PB with a relative small radius of
curvature and a maximum convexity located at mid-H. Left valve overlaps
slightly the right one with a maximum at VB. Surface
reticulated.Dimensions: L=0.32–0.40 mm, H=0.19–0.26 mm,
W=0.20–0.26 mm.Occurrence: Late Devonian, Guangxi (Wuzhishan
Formation of Yangdi section), South China.Remarks: In lateral outline, the specimens are close
to Scrobicula rotundata Polenova, 1952 from the Middle Devonian of
the Russian Platform (Polenova, 1952), but differs by the smaller radius of
curvature of the PB.
Genus Roundyella Bradfield, 1935
Roundyella reticulata Wei, 1988
(Plate 1, fig. 5)
1988 Roundyella reticulata Wei: 284, pl. 95, fig. 14.
Material: Five carapaces and six
valves.Description:
Small equivalve carapace with subrectangular outline in lateral view. DB
straight and long; ACA obtuse and bigger than PCA. AB rounded with a large
radius of curvature and a maximum convexity located a little below mid-H;
VB regularly curved; PB with a relative small radius of curvature and a
maximum convexity located at mid-H. Surface finely
reticulated.Dimensions: L=0.40–0.42 mm, H=0.22–0.24 mm,
W=0.15–0.16 mm.Occurrence: Middle Devonian of Longmen Mts.,
Sichuan, South China, and Late Devonian of Yangdi section, Guangxi, South
China.
Roundyella aff. reticulata Wei, 1988
(Plate 1, figs. 6, 7)
Material: Four carapaces and six
valves.Description:
Small equivalve carapace with subrectangular outline in lateral view. DB
straight and long; ACA obtuse and bigger than PCA. AB rounded with a large
radius of curvature and a maximum convexity located below mid-H; VB
regularly curved; PB with a relative small radius of curvature and a maximum
convexity located at lower third of H. Surface finely
reticulated.Dimensions: L=0.42–0.45 mm, H=0.24–0.26 mm,
W=0.16–0.18 mm.Occurrence: Late Devonian, Guangxi (Wuzhishan
Formation of Yangdi section), South China.Remarks: In lateral outline, the specimens resemble
Roundyella reticulata Wei, 1988 from the Middle Devonian of Sichuan,
South China (Wei, 1988), but differ by the small radius of curvature of the
PB.
Family Paraparchitidae Scott, 1959
Genus Paraparchites Ulrich & Bassler, 1906
Paraparchites circularis (Wei, 1983)
(Plate 1, fig. 8)
1983 Aparchites circularis Wei; Wei et al.: 46, pl. 11, figs. 7–9.
1988 Antiparaparchites circularis (Wei); Wei: pl. 102, figs. 2–3.
Material: Three
valves.Description:
Subrounded carapace. DB slightly curved; both AB and PB rounded with a large
radius of curvature and a maximum convexity located at mid-H; VB regularly
curved. Surface smooth. Dimensions: L=0.41–0.55 mm,
H=0.42–0.53 mm.Occurrence: Late Devonian, Guangxi (Xiangtian and
Wuzhishan formations of Yangdi section), South
China.Remarks: The
present specimens are assigned to Paraparchites circularis (Wei et
al., 1983) from the Early Devonian of Sichuan, South China. Wei (1988)
changed the generic attribution, certainly due to the lack of adventral
structure and referred the species to Antiparaparchites Coryell &
Rogatz, 1932. This genus is considered as a junior synonym of
Paraparchites since the revision of Paraparchitoidea by Sohn (1971,
1972).
Paraparchites subcircularis (Wang & Shi, 1982)
(Plate 1, figs. 9, 10)
1982 Antiparaparchites subcircularis Wang & Shi: 103, pl. 3, figs. 11–13.
1988 Antiparaparchites subcircularis Wang & Shi; Wei: pl. 102, fig. 6.
Material: Six carapaces and two
valves.Description:
Carapace rounded. DB regularly convex; both AB and PB rounded with a large
radius of curvature and a maximum convexity located at mid-H; VB regularly
curved. Left valve overlaps the right one with maxima at DB and AB, surface
smooth.Dimensions:
L=0.75–0.81 mm, H=0.74–0.80 mm, W=0.35–0.41 mm. Occurrence: Middle Devonian of Guangxi, South China;
Late Devonian of Guangxi (Liujiang and Wuzhishan formations of Nandong
section), South China. Remarks: Antiparaparchites Coryell &
Rogatz, 1932 is considered as a junior synonym of Paraparchites
since the revision of Paraparchitoidea by Sohn (1971, 1972).
Family Glyptopleuridae Girty, 1910
Genus Glyptopleura Girty, 1910
Glyptopleura sp.
(Plate 1, fig. 11)
Material: Three
valves.Description:
DB straight and long; CA obtuse and ACA larger than PCA. Both AB and PB
rounded with large radius of curvature and maximum convexity located at
mid-H; VB regularly curved. Valve ornamented by longitudinal narrow ridges.
Surface finely reticulate.Dimensions: L=0.68–0.72 mm, H=0.32–0.36 mm.
Occurrence: Late
Devonian, Guangxi (Wuzhishan Formation of Yangdi section), South
China.Remarks: In
lateral outline, the specimens resemble Glyptopleura
venosa (Ulrich, 1891) from the Late Devonian to the Early
Carboniferous of the Illinois, USA (Ulrich, 1891), but broken valves forbid
further assignation.
Family Geisinidae Sohn, 1961
Genus Knoxiella Egorov, 1950
Knoxiella cf. tuqiaoensis Wei, 1988
(Plate 1, fig. 12)
Material: Four
carapaces.Description: DB long and straight; CA obtuse; AB
with a relatively large radius of curvature, and with a maximum curvature
located at mid-H; VB regularly rounded with a maximum curvature located at
posterior part of VB; PB rounded with a large radius of curvature and a
maximum located at mid-H. A short and deep subcentral sulcus almost reaches
the dorsal border.Dimensions: L=0.43–0.50 mm, H=0.30–0.35 mm,
W=0.29–0.32.Occurrence: Late Devonian, Guangxi (Xiangtian and
Wuzhishan formations of Yangdi section), South China. Remarks: The specimens resemble Knoxiella
tuqiaoensis Wei, 1988 from the Middle Devonian of Longmen Mts.,
Sichuan, South China (Wei, 1988) in outline, but poor preservation of the
surface ornamentation forbids further assignation.
Genus Sargentina Coryell & Johnson, 1939
Sargentina sp.
(Plate 1, fig. 13)
Material: Two carapaces and three
valves.Description:
DB regularly convex; AB with relatively large radius of curvature with
maximum located at mid-H; PB with small radius of curvature with maximum
located a little below mid-H; VB slightly concave. Overlap of right valve
on left one with a maximum at VB. A short subcentral sulcus located a little
below DB. Surface smooth.Dimensions: L=0.41–0.48 mm, H=0.28–0.35 mm,
W=0.26–0.32 mm. Occurrence: Middle Devonian of Yunnan, South China;
Late Devonian of Guangxi (Xiangtian and Wuzhishan formations of Yangdi
section), South China. Remarks: In outline, the specimens are close to
Sargentina arcuata (Egorov, 1950) sensu Wei et al., 1983 from the
Early Devonian of Sichuan, South China (Wei et al., 1983). But S. arcuata is more elongate and has a larger radius of curvature at PB. Our
specimens may belong to a new species. The poor preservation could not allow
a precise determination.
Family Uncertain
Genus Westmontia Loranger, 1963
Westmontia cf. devilensis Casier & Lethiers, 1997
(Plate 1, fig. 14)
Material: Two carapaces and two
valves.Description:
DB long and straight; CA obtuse; AB flattened with a relatively large radius
of curvature and with a maximum located a little below mid-H; PB flattened
with a large radius of curvature with maximum located at mid-H; VB straight
to slightly curve. S2 developed and nearly reach to DB. Right valve
slightly overlaps the left one with a maximum at
VB.Dimensions:
L=0.85–1.05 mm, H=0.48–0.65 mm,
W=0.28–0.36 mm.Occurrence: Late Devonian, Guangxi (Wuzhishan
Formation of Nandong section), South China.Remarks: The specimens resemble Westmontia devilensis Casier & Lethiers, 1997 from the Frasnian–Famennian (Late
Devonian) of Nevada, USA (Casier and Lethiers, 1997), in outline, but differ
by more obtuse CA.
Family Acratiidae Gründel, 1962
Genus Acratia Delo, 1930
Acratia cf. longituda (McGill, 1963)
(Plate 1, figs. 15, 16)
(1) Acratia cf. mossolovica Egorov, 1953.
Right lateral view of complete carapace, YD15016, Frasnian, Yangdi section
(Bed 0). (2) Acratia cf. mayselae Egorov, 1953.
Right lateral view of complete carapace, YD15017, Famennian, Yangdi section
(Bed 68). (3) Acratia cf. zhongyingensis Wang,
1978. Right lateral view of complete carapace, YD15018, Famennian, Yangdi
section (Bed 58). (4) Acratia cf. buregiana Egorov, 1953. Right lateral view of complete carapace, ND15004, Famennian,
Nandong section (Bed 68). (5) Acratia cf.
silincula Polenova, 1953. Right lateral view of complete carapace,
ND15005, Famennian, Nandong section (Bed 68). (6) Acratia
aff. badwildungensis Casier & Lethiers, 1999. Right lateral view
of complete carapace, YD15019, Famennian, Yangdi section (Bed 79).
(7) Acratia sp. Right lateral view of complete carapace,
YD15020, Famennian, Yangdi section (Bed 68). (8) Famenella cf. postkairovaensis Lethiers & Casier, 1996. Right lateral view
of complete carapace, ND15006, Famennian, Nandong section (Bed 68).
(9) Famenella sp. 1. Right lateral view of complete
carapace, ND15007, Famennian, Nandong section (Bed 68). (10, 11) Famenella sp. 2. Right lateral view and dorsal view of complete
carapace, respectively, ND15008, Frasnian, Nandong section (Bed 59).
(12, 13) Bairdia sp. Right lateral view and dorsal view of
complete carapace, respectively, YD15021, Frasnian–Famennian, Yangdi section
(Bed 0). (14) Bairdiacypris cf. brevis (Wang,
1978) sensu Wei et al., 1983. Right lateral view of complete carapace,
YD15022, Frasnian–Famennian, Yangdi section (Bed 0).
(15) Bairdiacypris cf. quarziana (Egorov, 1953)
sensu Casier & Lethiers, 1998. Right lateral view of complete carapace,
ND15009, Frasnian, Nandong section (Bed 60).
(16) Fabalicypris pseudoillustris Lethiers, 1974. Right
lateral view of complete carapace, ND15010, Frasnian–Famennian, Nandong
section (Bed 60). (17) Rectobairdia cf.
wuxuantianensis Jiang in Wei et al., 1983. Right lateral view of
complete carapace, ND15011, Famennian, Nandong section (Bed 68).
(18) Bythocypris cf. fabalis Cooper, 1941. Right
lateral view of complete carapace, YD15023, Frasnian–Famennian, Yangdi
section (Bed 3). (19, 20) Healdiacypris wabamuensis Lethiers, 1981. (19) Right lateral view of complete carapace,
ND15012. (20) Dorsal view of complete carapace, ND15013; Famennian,
Nandong section (Bed 68). Scale bars represent 200 µm.
Material: Seven
carapaces.Description: DB slightly convex; AB with a
relatively large radius of curvature and with a maximum located a little
below mid-H; PB with a small radius of curvature and with a maximum located
at mid-H; VB regularly curved with a maximum convexity located at between
first third of L and mid-L. Overlap of left valve on right one. Surface
smooth.Dimensions:
L=0.42–0.51 mm, H=0.21–0.25 mm,
W=0.10–0.12 mm.Occurrence: Late Devonian, Guangxi (Xiangtian and
Wuzhishan formations of Yangdi section), South
China.Remarks: In
outline, our specimens are closed to Acratia longituda (McGill,
1963) from the Middle and Late Devonian of Alberta, Canada (McGill, 1963),
and Chaohu, Anhui, China (Chen and Bao, 1990). But Acratia longituda (McGill, 1963) is more elongate.
Acratia cf. mossolovica Egorov, 1953
(Plate 2, fig. 1)
Material: Three
carapaces.Description: DB nearly straight; AB and PB with a
relatively small radius of curvature and with a maximum located at mid-H;
VB slightly curved to straight. Overlap of left valve on right one with a
maximum at DB. Surface smooth.Dimensions: L=0.92–1.01 mm, H=0.38–0.45 mm,
W=0.40–0.47 mm. Occurrence: Late Devonian, Guangxi (Xiangtian
Formation of Yangdi section), South China.Remarks: In outline, our specimens resemble
Acratia mossolovica Egorov, 1953 from the Late Devonian of the
Russian Platform (Egorov, 1953). But A. mossolovica is more elongate
and has a larger radius of curvature at AB and PB. Our specimens may belong
to a new species.
Acratia cf. mayselae Egorov, 1953
(Plate 2, fig. 2)
Material: Three
carapaces.Description: Carapace diamond-shaped in lateral
outline; DB regularly arched; ADB and PDB arched; AB and PB with small radius
of curvature and with maxima located at mid-H; VB regularly concave. Left
valve slightly overlaps the right with a maximum at VB. Surface smooth.
Dimensions:
L=0.58–0.68 mm, H=0.38–0.45 mm, W=0.34–0.41 mm.
Occurrence: Late
Devonian, Guangxi (Wuzhishan Formation of Yangdi section), South
China.Remarks: In
lateral outline, these specimens resemble Acratia mayselae Egorov, 1953 from the Late Devonian of the Russian Platform (Egorov, 1953).
They differ by a more tapered AB.
Acratia cf. zhongyingensis Wang, 1978
(Plate 2, fig. 3)
Material: Two carapaces and three
valves.Description:
DB regularly convex; AB with a large radius of curvature and with a maximum
located between first third of H and mid-H; PB with a relative small
radius of curvature and with a maximum located at lower third of H; VB
nearly straight. Left valve slightly overlaps the right one along the free
margins with a maximum at DB and VB. Surface smooth.
Dimensions:
L=0.41–0.50 mm, H=0.21–0.28 mm, W=0.17–0.24 mm.
Occurrence: Late
Devonian, Guangxi (Wuzhishan Formation of Yangdi section), South
China.Remarks: In
lateral outline, the specimens resemble Acratia
zhongyingensis Wang, 1978 from the Late Permian of Guizhou, China
(Wang, 1978). It differs by being more elongate.
Acratia cf. buregiana Egorov, 1953
(Plate 2, fig. 4)
Material: Five
carapaces.Description: DB slightly convex; AB with a
relatively small radius of curvature and with a maximum located at lower
third of H; PB with a large radius of curvature and with a maximum located
at mid-H; VB slightly concave. Overlap of left valve on right one with a
maximum at DB. Surface smooth. Dimensions: L=0.58–0.65 mm, H=0.32–0.38 mm,
W=0.20–0.24 mm.Occurrence: Late Devonian, Guangxi (Wuzhishan
Formation of Nandong section), South China.Remarks: The specimens are close to Acratia
buregiana Egorov, 1953 from the Late Devonian of the Russian
Platform (Egorov, 1953) in outline, but they differ by a sharper ADB and a
rounder AB.
Acratia cf. silincula Polenova, 1953
(Plate 2, fig. 5)
Material: Four
carapaces.Description: DB slightly curve; AB with relatively a
large radius of curvature and with a maximum located at mid-H; PB with a
small radius of curvature and with a maximum located at lower third of H;
VB nearly straight. Slight overlap of left valve on right one; maximum at VB.
Surface smooth.Dimensions: L=0.48–0.60 mm, H=0.28–0.38 mm,
W=0.25–0.35 mm. Occurrence: Late Devonian, Guangxi (Wuzhishan
Formation of Nandong section), South China. Remarks: The specimens resemble Acratia
silincula Polenova, 1953 from Frasnian-Famennian (Late Devonian) of
the Russian Platform (Polenova, 1953) in outline, but differ by a flattened
AB.
Acratia aff. badwildungensis Casier & Lethiers, 1999
(Plate 2, fig. 6)
Material: Five
carapaces.Description: DB straight; AB with relatively a large
radius of curvature and with a maximum located at mid-H; PB with a small
radius of curvature and with a maximum located at lower third of H; VB
regularly curved. Left valve slightly overlaps the right one with a maximum
at DB. Surface smooth.Dimensions: L=0.48–0.60 mm, H=0.21–0.31 mm,
W=0.19–0.28 mm.Occurrence: Late Devonian, Guangxi (Wuzhishan
Formation of Yangdi section), South China. Remarks: In lateral outline, the specimens strongly
resemble Acratia badwildungensis Casier & Lethiers,
1999 from Frasnian–Famennian (Late Devonian) of the Schmidt quarry, Germany
(Casier et al., 1999). They differ by a more elongate carapace and an AB with
a larger radius of curvature.
Acratia sp.
(Plate 2, fig. 7)
Material: Three carapaces and two
valves.Description:
DB straight, almost equal and parallel to VB; AB and PB taping. The left
valve slightly overlaps the right one. Surface
smooth.Dimensions:
L=0.52–0.67 mm, H=0.23–0.33 mm, W=0.20–0.25 mm.
Occurrence: Late
Devonian of western Junggar, NW China, and Guangxi (Wuzhishan Formation of
Yangdi section), South China.Remarks: In outline, the specimens resemble Acratia tanaica Egorov, 1953 from the Late Devonian of the Russian Platform
(Egorov, 1953), but broken valves forbid further assignation.
Genus Acratina Egorov, 1953
Acratina ivanovoensis Egorov, 1953
(Plate 1, figs. 17, 18)
1953 Acratina ivanovoensis Egorov: 45, pl. 20, fig. 5a–c.
2017 Acratina ivanovoensis Egorov; Song et al.: 266, fig. 8B.
Material: Four carapaces and three
valves.Description:
DB nearly straight, ADB and PDB straight; AB with a small radius of curvature
and with a maximum located below mid-H; PB with a relative large radius of
curvature and with a maximum located at lower third of H; VB nearly
straight. Left valve slightly overlaps the right one along the free margins
with maxima at DB and VB. Surface smooth.Dimensions: L=0.41–0.50 mm, H=0.21–0.28 mm,
W=0.17–0.24 mm. Occurrence: Frasnian-Famennian (Late Devonian) of
the Russian Platform, western Junggar, NW China, and Yangdi section, Guangxi,
South China.
Genus Famenella Polenova, 1953
Famenella cf. postkairovaensis Lethiers & Casier, 1996
(Plate 2, fig. 8)
Material: Three carapaces and two
valves.Description:
DB straight to slightly convex; AB with a relatively large radius of
curvature and with a maximum located below mid-H; PB with a small radius of
curvature and with a maximum located at mid-H; VB straight to slightly
curved. Left valve overlaps the right one with a maximum at VB. Surface
smooth.Dimensions:
L=0.32–0.40 mm, H=0.18–0.23 mm, W=0.14–0.20 mm.
Occurrence: Late
Devonian, Guangxi (Wuzhishan Formation of Nandong section), South
China.Remarks: In
outline, the specimens resemble Famenella postkairovaensis
Lethiers & Casier, 1996 from the Late Devonian of Coumiac (France)
(Lethiers and Casier, 1996), but differ by bigger radius of curvature of PB
and AB.
Famenella sp. 1
(Plate 2, fig. 9)
Material: Four carapaces and two
valves.Description:
DB slightly convex; AB with a relatively large radius of curvature and with a
maximum located at mid-H; PB with a small radius of curvature and with a
maximum located at mid-H; VB straight to slightly curved. Left valve
overlaps the right one with a maximum at VB. Surface
smooth.Dimensions:
L=0.38–0.45 mm, H=0.20–0.24 mm, W=0.17–0.21 mm.
Occurrence: Late
Devonian, Guangxi (Wuzhishan Formation of Nandong section), South
China.Remarks: These
specimens are assigned to the genus Famenella Polenova, 1953 based
on their outline, but poor preservation makes impossible further assignation.
Famenella sp. 2
(Plate 2, figs. 10, 11)
Material: Two carapaces and one
valve.Description: DB
slightly convex; AB with a large radius of curvature and with a maximum
located at mid-H; VB nearly straight; PB with a relative small radius of
curvature and with a maximum located at the lower third of H; left valve
slightly overlaps the right one. Surface smooth.
Dimensions:
L=0.71–0.78 mm, H=0.35–0.41 mm, W=0.40–0.45 mm.
Occurrence: Late
Devonian, Guangxi (Wuzhishan Formation of Nandong section), South
China.Remarks: These
specimens are assigned to the genus Famenella Polenova, 1953, for
their outline. But this one has a smaller radius of curvature of PB by
comparison with other species belonging to the genus. It may be a new
species; however, to date, the material is insufficient to establish a new
species.
Family Bairdiidae Sars, 1887
Genus Bairdia McCoy, 1844
Bairdia sp.
(Plate 2, figs. 12, 13)
Material: Two
carapaces.Description: DB regularly slightly curved; AB and PB
rounded and almost equal; VB slightly concave; AVB and PVB nearly straight.
Left valve overlaps the right with a maximum at PB. Surface
smooth.Dimensions:
L=0.61–0.65 mm, H=0.32–0.35 mm,
W=0.25–0.28 mm.Occurrence: Late Devonian, Guangxi (Xiangtian and
Wuzhishan formations of Yangdi section), South
China.Remarks: In
outline, the specimens are close to Bairdia dushanensis Shi, 1964,
from the Middle and Late Devonian of Guizhou, South China (Shi, 1964). The
difference is the larger radius of curvature of PB in our specimens and the
maximum located higher. They may belong to a new species.
Genus Bairdiacypris Bradfield, 1935
Bairdiacypris cf. brevis (Wang, 1978) sensu Wei et al., 1983
(Plate 2, fig. 14)
Material: Four
carapaces.Description: DB slightly convex; AB with a
relatively large radius of curvature and with a maximum located at mid-H;
PB with a small radius of curvature and with a maximum located at below
mid-H; VB straight to slightly curved. Left valve slightly overlaps the
right one. Surface smooth. Dimensions: L=0.80–0.90 mm, H=0.41–0.49 mm,
W=0.28–0.34 mm. Occurrence: Late
Devonian, Guangxi (Xiangtian and Wuzhishan formations of Yangdi section),
South China.Remarks:
In lateral outline, the specimens resemble Bairdiacypris brevis (Wang, 1978) sensu Wei et al., 1983 from the Late Permian of Guizhou, South
China (Wei et al., 1983), but they differ by less overlap at VB.
Bairdiacypris cf. quarziana (Egorov, 1953) sensu Casier & Lethiers, 1998
(Plate 2, fig. 15)
Material: Two carapaces and three
valves.Description:
DB straight; AB with a relatively large radius of curvature and with a
maximum located below mid-H; PB with a small radius of curvature with a
maximum located at the lower third of H; VB slightly convex. Left valve
overlaps the right one with a maximum at DB and AB. Surface
smooth.Dimensions:
L=0.41–0.50 mm, H=0.26–0.33 mm,
W=0.22–0.28 mm.Occurrence: Late Devonian, Guangxi (Wuzhishan
Formation of Nandong section), South China.Remarks: The specimens resemble Bairdiacypris quarziana (Egorov, 1953) sensu Casier & Lethiers,
1998, from the Late Devonian of Nevada, USA (Casier and Lethiers, 1998), in
outline, but differs by a smaller radius of curvature on AB.
Genus Fabalicypris Cooper, 1946
Fabalicypris pseudoillustris Lethiers, 1974
(Plate 2, fig. 16)
1974 Fabalicypris pseudoillustris Lethiers: 1616, pl. 1, figs. 3, 4.
Material: Four carapaces three
valves.Description:
DB slightly curved; AB and PB rounded and nearly equal; VB straight to
slightly convex. Left valve overlaps the right one, with a maximum at VB.
Surface smooth. Dimensions: L=0.85–0.90 mm, H=0.43–0.48 mm,
W=0.32–0.35 mm.Occurrence: Late Devonian–Early Carboniferous of
the Dinant Basin, Belgium, and Late Devonian of Guangxi (Wuzhishan Formation
of Nandong section), South China.
Genus Rectobairdia Sohn, 1960
Rectobairdia cf. wuxuantianensis Jiang, 1983
(Plate 2, fig. 17)
Material: Two carapaces and three
valves.Description:
DB nearly straight; AB with a large radius of curvature and with a maximum
located at mid-H; PB with a relative small radius of curvature and with a
maximum located at the lower third of H; VB slightly curved. Left valve
slightly overlaps the right one with maximum at VB. Surface
smooth.Dimensions:
L=0.71–0.89 mm, H=0.41–0.52 mm,
W=0.37–0.44 mm.Occurrence: Late Devonian, Guangxi (Wuzhishan
Formation of Nandong section), South China.Remarks: The outline of our specimens is similar to
Rectobairdia wuxuantianensis Jiang, 1983 from the Middle Devonian of
South China (Wei et al., 1983), but our specimens differ by larger carapaces
and a smaller overlap on DB.
Family Bythocyprididae Maddocks, 1969
Genus Bythocypris Brady, 1880
Bythocypris cf. fabalis Cooper, 1941
(Plate 2, fig. 18)
Material: Two carapaces and three
valves.Description:
DB regularly arched and ADB and PDB almost equally inclined; AB with a small
radius of curvature and with a maximum located at lower third of H; PB with
a relatively larger radius of curvature and with a maximum located at
mid-H; VB slightly convex. Left valve overlaps right one with a maximum at
VB. Surface smooth.Dimensions: L=0.30–0.41 mm, H=0.19–0.27 mm,
W=0.16–0.24 mm.Occurrence: Late Devonian of Guangxi (Xiangtian and
Wuzhishan formations of Yangdi section), South
China.Remarks: In
outline the specimens resemble Bythocypris fabalis Cooper, 1941,
from the Early Carboniferous of Illinois, USA (Cooper, 1941), but differ by a
smaller radius of curvature at PB.
Family Bairdiocyprididae Shaver, 1961
Genus Healdiacypris Bradfield, 1935
Healdiacypris wabamuensis Lethiers, 1981
(Plate 2, figs. 19, 20)
1981 Healdiacypris wabamuensis Lethiers: 66, pl. 12, figs. 116–119.
(1) Bairdiocypris cf. cracenis Jiang,
1983. Right lateral view of complete carapace, YD15024, Frasnian–Famennian,
Yangdi section (Bed 98). (2) Praepilatina adamczaki
Olempska, 1979. Right lateral view of complete carapace, ND15014,
Frasnian–Famennian, Nandong section (Bed 68).
(3) Praepilatina? sp. Right valve, YD15025, Frasnian,
Yangdi section (Bed 21). (4) Microcheilinella cf.
postacuta Wei, 1988. Right lateral view of complete carapace,
YD15026, Frasnian, Yangdi section (Bed 1). (5, 6) Microcheilinella cf. ventrasa Polenova, 1960. Right
lateral view and dorsal view of complete carapace, respectively, YD15027,
Frasnian, Yangdi section (Bed 1). (7, 8) Microcheilinella
cf. larionovae Polenova, 1960. Right lateral view and dorsal view of
complete carapace, respectively, YD15028, Frasnian, Yangdi section (Bed 1).
(9, 10) Kummerowillina prima (Adamczak, 1976).
(9) Right lateral view of complete carapace, YD15029;
(10) Dorsal view of complete carapace, YD15030; Frasnian–Famennian,
Yangdi section (Bed 68). (11) Kummerowillina cf.
oblonga (Wei, 1988). Right lateral view of complete carapace,
YD15031, Frasnian, Yangdi section (Bed 15).
(12) Kummerowillina suboblonga (Wei, 1988). Right lateral
view of complete carapace, YD15032, Frasnian, Yangdi section (Bed 15).
(13) Silenites demirotunda Wei, 1988. Right lateral view of
complete carapace, ND15015, Frasnian–Famennian, Nandong section (Bed 68).
(14) Paracoelonella cf. saltatoria Wang & Cao,
1997. Left lateral view of complete carapace, ND15016, Frasnian, Nandong
section (Bed 60). (15) Entomoprimitia cf. kayseri
(Waldschmidt, 1885). Right lateral view of complete carapace, ND15022,
Frasnian, Nandong section (Bed 66). (16) Bertillonella subcircularis Stewart & Hendrix, 1945. Right lateral view of complete
carapace, ND15017, Frasnian–Famennian, Yangdi section (Bed 54); Frasnian,
Nandong section (Bed 59). Scale bars represent 200 µm.
Material: Eight carapaces and three
valves.Description:
DB regularly convex; AB with a relatively large radius of curvature and with
a maximum located at mid-H; PB with a small radius of curvature and with a
maximum located at lower third of H; VB nearly straight. Left valve
overlaps the right one with maxima at DB and AB. Surface smooth.
Dimensions:
L=0.53–0.70 mm, H=0.30–0.44 mm,
W=0.30–0.40 mm.Occurrence: Late Devonian, western Canada, and
Guangxi (Wuzhishan Formation of Nandong section), South China.
Genus Bairdiocypris Kegel, 1932
Bairdiocypris cf. cracenis Jiang, 1983
(Plate 3, fig. 1)
Material. Three carapaces and two
valves.Description:
DB regularly convex; AB with a relatively large radius of curvature and with
a maximum located a little below mid-H; PB with a small radius of curvature
and with a maximum located at lower third of H; VB nearly straight. Left
valve strongly overlaps the right one with maxima at DB and ADB. Surface
smooth.Dimensions:
L=0.92–1.10 mm, H=0.57–0.61 mm, W=0.40–0.45 mm.
Occurrence: Late
Devonian, Guangxi (Xiangtian and Wuzhishan formations of Yangdi section),
South China. Remarks:
The specimens strongly resemble Bairdiocypris cracenis
Jiang, 1983 from the Middle Devonian of Yunnan, South China (Wei et al.,
1983) in outline. However, the broken carapaces forbid further attribution.
Genus Praepilatina Polenova, 1970
Praepilatina adamczaki Olempska, 1979
(Plate 3, fig. 2)
1979 Praepilatina adamczaki Olempska: 115, pl. 22, fig. 5.
1997 Praepilatina adamczaki Olempska; Olempska: 313, fig. 10G, H.
2017 Praepilatina adamczaki Olempska: Song et al.: 268, fig. 8J.
Material: Four carapaces and two
valves.Description:
DB strongly convex, ADB and PDB almost symmetrically inclined; AB and PB
widely rounded; VB straight to slightly concave. Left valve overlaps right
one all around carapace with maxima at VB and AB. Surface
smooth.Dimensions:
L=0.46–0.58 mm, H=0.32–0.43 mm,
W=0.21–0.33 mm.Occurrence: Late Devonian of Holy Cross Mts.,
Poland, western Junggar, Xinjiang, NW China, and Guangxi (Liujiang and
Wuzhishan formations of Nandong section), South China.
Praepilatina? sp.
(Plate 3, fig. 3)
Material: Three
valves.Description:
Carapace rounded in lateral outline. DB strongly curved; PB slight rounder
than AB; VB regularly curved. Left valve slightly overlaps the right one
along the free margins with maximum at VB. Surface smooth.
Dimensions:
L=0.50–0.60 mm, H=0.46–0.55 mm.Occurrence: Late Devonian, Guangxi (Xiangtian and
Wuzhishan formations of Yangdi section), South
China.Remarks: Based
on the rounded outline our specimens may be assigned to the genus
Praepilatina Polenova, 1970. The specimens in outline resemble
Praepilatina subcirculata Wang & Ma, 2007 from the Late Devonian
in Xikuangshan, Hunan, China (Wang and Ma, 2007), but they differ by a more
curved PVB. Our specimens perhaps belong to a new species, but at present the
material is insufficient to establish it.
Genus Silenites Coryell & Booth, 1933
Silenites demirotunda Wei, 1988
(Plate 3, fig. 13)
1988 Silenites demirotunda Wei: 301, pl. 109, figs. 11–13.
Material: Three carapaces and two
valves.Description:
Carapace arched. DB regularly curved; both AB and PB rounded with a small
radius of curvature and a maximum convexity located at lower third of H. VB
straight. Slight overlap of left valve on right one with a maximum at DB.
Surface smooth. Dimensions: L=0.71–0.80 mm, H=0.33–0.41 mm,
W=0.25–0.32 mm. Occurrence: Late Devonian of Sichuan and Guangxi
(Wuzhishan Formation of Nandong section), South China.
Family Microcheilinellidae Gramm, 1975
Genus Microcheilinella Geis, 1933
Microcheilinella cf. postacuta Wei, 1988
(Plate 3, fig. 4)
Material: Three
carapaces.Description: DB straight; VB slightly curved on left
valve and straight on right one; both AB and PB rounded, the former smaller.
Strong overlap of left valve on right one all around the carapace with maxima
at PVB and PB. Surface smooth.Dimensions: L=0.63–0.70 mm, H=0.21–0.25 mm,
W=0.24–0.28 mm. Occurrence: Late Devonian, Guangxi (Xiangtian
Formation of Yangdi section), South China.Remarks: In lateral outline, the specimens strongly
resemble Microcheilinella postacuta Wei, 1988, from the
Early Devonian of Sichuan, South China (Wei, 1988). It differs by its
stronger overlap at PVB.
Microcheilinella cf. ventrasa Polenova, 1960
(Plate 3, figs. 5, 6)
Material: Two carapaces and five
valves.Description:
DB regularly arched; AB with a small radius of curvature and with a maximum
located below mid-H; PB with a relative large radius of curvature and with
a maximum located at mid-H; VB regularly curved on left valve and nearly
straight on right one. Left valve strongly overlaps the right one, with a
minimum at AB. Surface smooth.Dimensions: L=0.67–0.72 mm, H=0.45–0.48 mm,
W=0.48–0.51 mm. Occurrence: Late Devonian, Guangxi (Xiangtian
Formation of Yangdi section), South China.Remarks: The specimens resemble
Microcheilinella ventrasa Polenova, 1960, from the Middle Devonian
of the Russian Platform (Polenova, 1960) in outline. It differs by its more
elongate lateral outline and smaller overlap at AVB.
Microcheilinella cf. larionovae Polenova, 1960
(Plate 3, figs. 7, 8)
Material: Two carapaces and two
valves.Description:
DB slightly arched; both AB and PB rounded and quite equivalent; VB slightly
curved. Left valve overlaps the right one with maxima at VB and PVB. Surface
smooth. Dimensions:
L=0.60–0.65 mm, H=0.34–0.38 mm, W=0.40–0.43 mm.
Occurrence: Late
Devonian, Guangxi (Xiangtian Formation of Yangdi section), South China.
Remarks: The
specimens resemble in outline Microcheilinella larionovae
Polenova, 1960 from the Middle Devonian of the Russian Platform (Polenova,
1960). It differs by absence of pit ornamentation on the valves.
Family Healdiidae Harlton, 1933
Genus Kummerowillina Adamczak, 1978
Kummerowillina prima (Adamczak, 1976)
(Plate 3, figs. 9, 10)
1976 Kummerowia prima Adamczak: 394, pl. 30, figs. 197–199.
1978 Kummerowillina prima Adamczak: 515.
1988 Kummerowia prima Adamczak; Wei: pl. 109, fig. 5.
Material: Five
carapaces.Description: Small and almost quadrangular carapace.
Both DB and VB nearly straight; both AB and PB rounded and quite equivalent.
Overlap of left valve on right valve all around the carapace with a maximum
at VB. Surface smooth. Dimensions: L=0.34–0.40 mm, H=0.16–0.20 mm,
W=0.08–0.12 mm. Occurrence: Middle Devonian of Poland, Early
Devonian of Sichuan, South China and Late Devonian of Guangxi (Xiangtian and
Wuzhishan formations of Yangdi section), South China.
Remarks: The genus of
Kummerowia Adamczak, 1976 is in reality a junior synonym of
Kummerowia Samoilova & Smirnova, 1960. It has been replaced
by Kummerowillina (Adamczak, 1978).
Kummerowillina cf. oblonga (Wei, 1988)
(Plate 3, fig. 11)
Material: Two carapaces and three
valves.Description:
DB regularly arched; AB with a small radius of curvature and with a maximum
of curvature located at lower third of H; PB with a relative large radius
of curvature and with a maximum located at mid-H; VB nearly straight to
slightly convex. Left valve overlaps the right one with maxima at VB and PVB.
Surface smooth.Dimensions: L=0.75–0.82 mm, H=0.37–0.43 mm,
W=0.25–0.30 mm. Occurrence: Late Devonian, Guangxi (Xiangtian
Formation of Yangdi section), South China.Remarks: The specimens resemble Kummerowia oblonga Wei, 1988 from the Middle Devonian of Longmen Mts., South China
(Wei, 1988) in outline. It differs by its straighter VB and a smaller overlap
on PB.
Kummerowllina suboblonga (Wei, 1988)
(Plate 3, fig. 12)
1988 Kummerowia suboblonga Wei: 300, pl. 109, fig. 10.
2017 Kummerowia suboblonga Wei; Song et al.: 272, fig. 9L–M
Material: Four carapaces and two
valves.Description:
Small and almost quadrangular carapace. Both DB and VB straight and nearly
parallel; AB and PB almost equivalent and regularly rounded. Left valve
slightly overlaps the right one along the free margins. Surface
smooth.Dimensions:
L=0.40–0.45 mm, H=0.20–0.24 mm, W=0.20–0.25 mm.
Occurrence: Early
Devonian of Sichuan, South China; Late Devonian of western Junggar, NW China,
and Guangxi (Xiangtian Formation of Yangdi section), South China.
Family Uncertain
Genus Paracoelonella Wang, 1983
Paracoelonella cf. saltatoria Wang & Cao, 1997
(Plate 3, fig. 14)
(1, 2) Richterina striatula (Richter, 1848). (1) Right lateral
view of complete carapace, YD15033, Frasnian–Famennian, Yangdi section
(Bed 1). (2) Right lateral view of complete carapace, ND15018,
Frasnian, Nandong section (Bed 65). (3, 4) Richterina (Volkina) zimmermanni (Volk, 1939). (3) Right
lateral view of complete carapace, ND15019. (4) Right lateral view
of right valve, ND15020; Frasnian, Nandong section (Bed 60).
(5) Rabienella volki (Rabien, 1958). Right valve, YD15034,
Frasnian, Yangdi section (Bed 1). (6) Nehdentomis aff.
tenera (Gürich, 1896). Right lateral view of complete carapace,
ND15021, Frasnian, Nandong section (Bed 65). Scale bars represent
200 µm.
Material: Two carapaces and two
valvesDescription: DB
regularly convex; AB with a relatively large radius of curvature and with a
maximum located at mid-H; PB with a small radius of curvature and with a
maximum located at lower third of H; VB nearly straight. The right valve
strongly overlaps the left one with a minimum at PB. Some small nodules
distribute irregularly on the surface.Dimensions: L=0.60–0.68 mm, H=0.28–0.33 mm,
W=0.24–0.27 mm. Occurrence: Late Devonian, Guangxi (Wuzhishan
Formation of Nandong section), South China.Remarks: The specimens close to Paracoelonella saltatoria Wang & Cao, 1997 from the Early
Devonian of Yunnan, South China (Wang and Cao, 1997) in outline. However, in
our specimens the ADB is sharper and the VB is straighter.
Family Entomozoidae Přibyl, 1951
Genus Entomoprimitia Kummerow, 1939
Entomoprimitia cf. kayseri (Waldschmidt, 1885)
(Plate 3, fig. 15)
Material: One carapaces and four
valves.Description:
Carapace subelliptic. DB straight; AB and PB rounded and nearly equal; VB
regularly convex. Surface with 10 concentric ribs, and four to five
longitudinal ribs in the middle part of the carapace; a small node is present
at the end of sulcal depression. The sulcus is shallow and
short.Dimensions:
L=1.00–1.20 mm, H=0.96–1.08 mm, W=0.35 mm.
Occurrence: Late
Devonian, Guangxi (Wuzhishan formations of Nandong section), South
China.Remarks:The
specimens resemble Entomoprimitia kayseri (Waldschmidt,
1885) from the Late Devonian of Germany (Waldschmidt, 1885) in outline. It
differs by the absence of swelling and node before the sulcal depression.
Genus Bertillonella Stewart & Hendrix, 1945
Bertillonella subcircularis Stewart & Hendrix, 1945
(Plate 3, fig. 16)
1945 Bertillonella subcircularis Stewart & Hendrix: 100, pl. 11, figs. 1, 2.
1981 Bertillonella subcircularis Stewart & Hendrix 1945; Duffield & Warshauer: 81, pl. 3, figs. 11,
12.
1984 Bertillonella subcircularis Stewart & Hendrix 1945; Wang: 30, pl. 3, fig. 6.
1987 Bertillonella subcircularis Stewart & Hendrix 1945; Wang: 315, pl. 2, fig. 12.
2009 Bertillonella subcircularis Stewart & Hendrix 1945; Wang: 39, pl. 12, figs. 10, 11.
Material: Three carapaces and 12
valves.Description:
Carapace subelliptic. DB straight to slightly curved; AB and PB rounded and
nearly equal; VB regularly convex. Surface with 15–20 concentric ribs; outer
ribs extending parallel to margins; central ones are less-developed, arranged in circular or oval
pattern.Dimensions:
L=1.00–1.30 mm, H=0.96–1.10 mm,
W=0.36–0.45 mm.Occurrence: Late Devonian of Ohio and Virginia, USA;
Middle–Late Devonian of Guangxi (Yangdi and Nandong sections), South China.
Genus Richterina Gürich, 1896
Richterina striatula (Richter, 1848)
(Plate 4, figs. 1, 2)
1848 Cytherina striatula Richter: 64, pl. 5, fig. 56.
1913 Richterina striatula Reinh. Richter; Paeckelmann: 192, pl. 3, fig. 6.
1939 Richterina (Richterina) striatula (Richter); Kummerow: 60, pl. 7, fig. 6.
1954 Richterina (Richterina) striatula (Reinh.Richter 1848); Rabien: 119, pl. 2, fig. 15; pl. 4, fig. 37.
1978 Richterina (Richterina) striatula (Richter); Gooday: 110, pl. 1, figs. 1–3.
1979 Richterina (Richterina) striatula (Richter, 1848); Olempska: 139, pl. 30, fig. 10.
1984 Richterina (Richterina) striatula (Richter); Wang: 53, pl. 12, fig. 3A–D.
1985 Richterina striatula (Richter); Casier: pl. 3. fig. 43.
1992 Richterina (Richterina) striatula (Richter, 1848); Olempska: fig. 2A–I, fig. 3A–D.
2009 Richterina striatula (Richter 1848); Wang: 76, pl. 26, figs. 10–12.
Material: 12 carapaces and 12
valves.Description:
Carapace oval. DB regularly convex, CA obtuse; AB and PB rounded and equal;
VB regularly concave. Surface with about 25 longitudinal ribs; outer ribs
extending parallel to margins; central ones are less-developed,
arranged in circular or oval pattern.Dimensions: L=0.50–0.60 mm, H=0.36–0.40 mm;
W=0.25–0.28 mm. Occurrence: Late Devonian of Germany, Poland,
France, Belgium, and Algeria; Late Devonian, Guangxi (Yangdi and Nandong
section), South China.
Richterina (Volkina) zimmermanni (Volk, 1939)
(Plate 4, figs. 3, 4)
1939 Entomis (Nehdentomis) zimmermanni Volk: 250, pl. 1, fig. 10.
1954 Richterina (Volkina) zimmermanni (Volk); Rabien: 110, pl. 2, fig. 14; pl. 4, figs. 33, 34.
1975 Richterina (Volkina) zimmermanni (Volk); Casier: pl. 3, fig. 2a–c.
1982 Richterina (Volkina) zimmermanni (Volk); Casier: pl. 2, fig. 6.
1984 Richterina (Volkina) zimmermanni (Volk); Wang: 51, pl. 12, figs. 1–3.
2002 Richterina (Volkina) zimmermanni (Volk); Olempska: 262, fig. 9C–E.
2009 Richterina (Volkina) zimmermanni (Volk); Wang: 70, pl. 25, figs. 1–3.
2011 Richterina (Volkina) zimmermanni (Volk); Nazik & Groos-Uffenorde: 172, pl. 1, fig. 9.
Material: 15 carapaces and six
valves.Description:
Carapace ovate. DB straight to slightly curved, CA obtuse; AB and PB rounded
and nearly equal; VB regularly convex. Surface with about 15–20 longitudinal
ribs; outer ribs extending parallel to margins; central ones
are less-developed, arranged in oval pattern.
Dimensions:
L=0.68–0.86 mm, H=0.49–0.61 mm;
W=0.30–0.48 mm.Occurrence: Late Devonian of Germany, Poland,
France, Belgium, Algeria, Turkey, and Guangxi (Liujiang and Wuzhishan
formations of Nandong section), South China.
Genus Rabienella Gründel, 1962
Rabienella volki (Rabien, 1958)
(Plate 4, fig. 5)
1958 Waldeckella volki Rabien; Rabien & Rabitz: 173, pl. 1, fig. 2.
1987 Rabienella volki (Rabien); Wang: 311, pl. 1, figs. 4–8.
1989 Rabienella volki (Rabien); Groos-Uffenorde and Wang: pl. 2,
fig. 13.
2009 Rabienella volki (Rabien); Wang: 50–51, pl. 17, figs. 4–8.
Material: Five valves.Description: Carapace oval. DB regularly convex; AB
and PB rounded and equal; VB regularly concave. Surface with about 15
concentric ribs; outer ribs extending parallel to margins; central ones
arranged in circular or oval pattern. Dimensions: L=0.95–1.00 mm, H=0.54–0.57 mm.
Occurrence: Late
Devonian of Germany and Guangxi (Xiangtian Formation of Yangdi section),
South China.
Genus Nehdentomis Matern, 1929
Nehdentomis aff. tenera (Gürich, 1896)
(Plate 4, fig. 6)
Material: Five carapaces and three
valves.Description:
Carapace ovate. DB straightened to slightly curved; AB and PB rounded and
nearly equal; VB regularly convex. Surface with longitudinal ribs; central
ones are less developed.Dimensions: L=0.73–0.88 mm, H=0.55–0.65 mm,
W=0.30–0.37 mm. Occurrence: Late Devonian, Guangxi (Wuzhishan
Formation of Nandong section), South China.Remarks: The specimens resemble Nehdentomis tenera (Gürich, 1896) from the Early Devonian of South China (Wang,
2009) in outline and longitudinal ribs, but differs by larger radius of
curvature of AB and PB, and N. tenera is more elongate. It may
belong to a new species.