Bull. Tohoku Univ. Museum, No. 15, pp. 5–8, 2016
© by The Tohoku University Museum

Bandoceras, a new Late Silurian genus of orthocerid
cephalopod from the Hitoegane Formation, Gifu
Prefecture, Central Japan
Shuji Niko
Department of Environmental Studies, Faculty of Integrated Arts and Sciences, Hiroshima University, Higashihiroshima 7398521, Japan
Abstract: A new genus of orthocerid cephalopod, Bandoceras, is proposed on the basis of B.
gifuense sp. nov. from the Ludlow (early Late Silurian) calcareous shale of the upper Hitoegane
Formation in the Shinhirayuonsen area, Takayama City, Gifu Prefecture, Central Japan. Its
morphologies of septal necks, connecting rings, endosiphuncular deposits suggest the newgenus and species belong to the subfamily Spyroceratinae. Bandoceras gifuense differs from thepossible ancestor, Gordonoceras Teichert and Glenister, 1953, from the Lower (or Middle) Silurianof Tasmania, in having transverse surface lirae.

Introduction
The Hitoegane Formation, named by Nakai (1984), crops
out in the Hitoegane and Shinhirayuonsen area, Takayama
City, Gifu Prefecture, Central Japan. A diverse fauna ofmiddle to late Ludlow (or Pridoli; Late Silurian) age, including
tabulate corals (Niko, 2001, 2004, 2007, 2008), trilobites(Kobayashi and Hamada, 1974, 1987) and machaerid(Kobayashi and Hamada, 1976), have been described from
calcareous beds (= the Hitoegane Limestone Member in Igo,1990) of the upper part of the formation. Recently, a single
orthocerid specimen was collected from this fossiliferous
member as the first occurrence of cephalopod from theformation. The intent of this paper is to propose a new genus
and species, Bandoceras gifuense, on the basis of the newmaterial.

Systematic Paleontology
Order Orthocerida Kuhn, 1940
Superfamily Pseudorthoceratoidea Flower and Caster, 1935
Family Pseudorthoceratidae Flower and Caster, 1935
Subfamily Spyroceratinae Shimizu and Obata, 1935
Genus Bandoceras gen. nov.
Type species.—Bandoceras gifuense sp. nov. bymonotypy.
Diagnosis.—Exogastric cyrtocone with gradual conch
expansion and subcircular cross section; shell surface
ornamented by transverse lirae; sutures straight andtransverse; camerae short; siphuncle relatively narrow,subcentral with suborthochoanitic to cyrtochoanitic septal
necks and subcylindrical connecting rings; endosiphunculardeposits form continuous lining; cameral deposits mostly
episeptal-mural.
Etymology.—The generic name honors the late Dr. Yuji
Bando, in recognition of his contributions to the taxonomic
and biostratigraphic studies on fossil cephalopods.
Discussion.—The siphuncular morphologies of thiscephalopod, such as the suborthochoanitic to cyrtochoanitic
septal necks, subcylindrical connecting rings and continuouslining of the endosiphuncular deposits, suggest that thenew genus belongs to the Spyroceratinae of the family
Pseudorthoceratidae. In the subfamily, Gordonoceras
Teichert and Glenister (1953; type species, G. bondi Teichert
and Glenister, 1953, p. 39, 40, pl. 4, figs. 1‒3, text-fig. 2C)from the Lower (or Middle) Silurian of Tasmania, shows
close similarity with Bandoceras gen. nov. in its exogastricconch with gradual expansion, subcentral siphuncle andshort camerae, but is differentiated by the latter in lacking
distinct surface ornamentation. The author believes that
Gordonoceras is the ancestor of Bandoceras.
The Early Carboniferous genus Pseudocyrtoceras
Schindewolf (1943; type species, Cyrtoceras acus
Koninck, 1880, p. 28, 29, pl. 35, figs. 6, 6a, 7, pl. 36,fig. 3; Schindewolf, 1943, fig. 15) differs from the newgenus in having more rapid expansion of the conchwith dorsoventrally depressed profiles and the wellinflated subglobular connecting rings. Among them, the6Shuji Niko

Figure 1. Bandoceras gifuense gen. et sp. nov., holotype, IGPS coll. cat. no. 111568, from the Upper Silurian Hitoegane
Formation in Takayama City, Gifu Prefecture. 1. Lateral view, venter on left. 2. Transverse polished section, venter down. 3.
Partial enlargement of Figure 1.1 to show details of surface ornamentation. 4. Longitudinal thin section, showing details ofseptal neck. 5. Dorsoventral polished section of apical shell, venter on left. 6, 7. Longitudinal thin sections of adoral shell,
venter on left (but oblique to dorsoventral plane), showing details of siphuncle, endosiphuncular deposits (in Figure 1.6), andcameral deposits. Scale bar is 5 mm in Figure 1.1; 4 mm in Figure 1.2; 2 mm in Figures 1.3, 1.6, 1.7; 0.2 mm in Figure 1.4; 2.5mm in Figure 1.5.
latter is one of the important characters of the subfamily
Pseudorthoceratinae Flower and Caster, 1935.
Similar surface ornamentation with Bandoceras is foundin a Middle Silurian species Orthoceras wauwatosense

Whitfield (1882, p. 297, pl. 19, fig. 2; Foerste, 1928, p. 250‒
252, pl. 53, figs. 2A‒D, 3(?), pl. 56, fig. 9(?) as Geisonoceras
wauwatosense) that is the type species of Geisonocerina
Foerste, 1935. Internal features of the species are7

Silurian cephalopod from Gifu
incompletely known but reportedly it has an orthoconic
conch with circular cross section and very deeply concaved
septa. Familial placement of Geisonocerina is still uncertain.
The Middle Ordovician genus Centroonoceras Kobayashi(1934; emended by Niko, 2005; type species, Ooceras?
tokunagai Kobayashi, 1927, p. 202, 203, pl. 18, figs. 10a,b; Niko, 2005, p. 1028‒1030, figs. 1.1‒1.8) also resembles
Bandoceras. However, the relatively wide siphuncle ofCentroonoceras suggests that it belongs to the familyProteoceratidae Flower, 1962. Similarities between the twogenera are probably superficial.
Bandoceras gifuense sp. nov.
Figure 1
Diagnosis.—Same as for the genus.
Description.—A single longiconic phragmocone, 53
mm in approximate length and 3.5 mm in diameter at
apical end, is available for study. It is faintly exogastriccyrtocone with gradual conch expansion, whose angle isapproximately 6°; apical shell and body chamber are notpreserved; cross sections of conch are subcircular indicating
weak lateral compression; ratios of lateral conch diameterper dorsoventral one are approximately 0.88; surface
ornamentation consists of transverse lirae that are slightly
oblique and incline toward dorsum; there are approximately
8 ridges in 1 mm of conch length. Sutures are essentiallystraight and transverse; septal curvature is shallow andclosely spaced to form short camerae; form ratios ofcamerae (maximum width per length in dorsoventral plane)
range from 2.5 to 5.6; siphuncle is subcentral (ventral fromcenter) in position and relatively narrow; ratios of siphuncular
position (distance of central axis of septal foramen fromventral shell surface per corresponding conch diameter in
dorsoventral plane) are 0.39‒0.41; siphuncular wall consistsof suborthochoanitic to cyrtochoanitic septal necks and thinconnecting rings; septal neck length is short, 0.19‒0.27 mm;
connecting rings weakly expanded in camerae and indicate
subcylindrical shape. Endosiphuncular deposits partly
preserved in adoral shell, and form continuous lining on
ventral siphuncular wall; cameral deposits well-developed,episeptal-mural (or mural in rare cases).
Material examined.—Holotype, IGPS coll. cat. no. 111568.
The specimen is kept in the Tohoku University Museum,Sendai.
Etymology.—The specific mane is derived from Gifu
Prefecture.
Occurrence.—The new species described herein is fromthe middle to late Ludlow (early Late Silurian) calcareous
shale at west bank of the Takahara-gawa River in theShinhirayuonsen area. The site is at 36°14’10”N latitude and137°31’28”E longitude, whose position on geographic map

was given in figure 1 in Niko (2008).

Acknowledgements
The holotype of Bandoceras gifuense gen. et sp. nov.
was found and generously donated to the Tohoku University
Museum by Mr. Yukio Miyake. Mr. Yoshihito Senzai provided
field assistance. Reviewer Dr. Masayuki Ehiro madevaluable suggestions that improved an earlier draft of thispaper. I would like to thank for these collaborators.

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