First discovery of fossil Nautilus pompilius Linnaeus, 1758 (Nautilidae, Cephalopoda) from Pangasinan, northwestern Philippines

Abstract

A chambered nautilus shell from the early Pleistocene deep-water sediments in the Bolinao area of Pangasinan province, northwestern Luzon, Philippines is described. Although the shell is fragmentary, the shell features indicate that the specimen is referable with reservation to the extant Nautilus pompilius Linnaeus, 1758. This finding represents the first and oldest fossil record of N. pompilius and complements the Plio-Pleistocene gap of the nautiloid fossil records. Taphonomic implications for Cenozoic nautiloids were briefly discussed.

Full text

Fossil Nautilus pompilius from Philippines 89
Paleontological Research, vol.12, no. 1, pp. 89-95, April 30, 2008
© by the Palaeontological Society of Japan
Introduction
Modern chambered nautiluses are the only living
nautiloids and all belong to the single genus Nautilus
(Nautilidae, Nautiloidea, Cephalopoda; but see Ward
and Sanders, 1997). The genus includes ve or six rec-
ognized species living in deep waters of the tropical
Indo-Pacic (Saunders, 1987). A molecular analysis us-
ing mtDNA and nuclear DNA suggests that they diver-
sied during the last several million years (Wray et al.,
1995). The oldest fossil records of the genus Nauti-
lus include the late Eocene-early Oligocene Nautilus
praepompilius Shimansky, 1957, from the Republic of
Kazakhstan (Saunders et al., 1996) and the late Eocene
N. aff. cookanum Whiteld, 1892, from northwestern
Washington, USA (Squires, 1988). After the late Oligo-
cene, no fossil example of Nautilus has heretofore been
reported except for a recently collected specimen of N.
pompilius from the Holocene uplifted reefal sediment
in Leyte, Philippines (Kase et al., unpublished data).
Two other genera assigned to the Nautilida, Eutrepho-
ceras and Aturia, persisted to the end of the Miocene,
so that the fossil record of nautiloids has been totally
unknown for the Plio-Pleistocene (Kummel, 1956;
Teichert and Matsumoto, 1987). In this context, dis-
covery of a fossil example from this time interval is
therefore important for understanding the evolutionary
history of nautiloids. Fossil nautiloids have been an-
ticipated in Plio-Pleistocene marine sediments exposed
in areas where chambered nautiluses occur today (the
Indian and western Pacic Oceans; see House, 1987).
We document here the discovery of the rst fossil ex-
ample of the genus Nautilus, best interpreted as belong-
ing to N. pompilius Linnaeus, 1758, from this interval,
First discovery of fossil Nautilus pompilius
Linnaeus, 1758 (Nautilidae, Cephalopoda)
from Pangasinan, northwestern Philippines
RYOJI WANI1, ROBERTO S. P. DE OCAMPO2, YOLANDA M. AGUILAR3, MAYBELLYN A. ZEPEDA3,
YUKITO KURIHARA4, KYOKO HAGINO5, HIROKI HAYASHI6 AND TOMOKI KASE4
1JSPS Postdoctoral Fellow for Research Abroad, Department of Geology, University of South Florida,
4202 E. Fowler Ave., SCA 528, Tampa, FL 33620-5201, USA (e-mail: wani.com@nifty.com)
2Geology Division, the National Museum of the Philippines, P. Burgos Street, Manila 1000, Philippines
(e-mail: rspdeocampo@yahoo.com.ph)
3Mines and Geosciences Bureau, North Ave., Diliman, Quezon City, Philippines
(e-mail: yolagui@yahoo.com, mazepeda@pacic.net.ph)
4Department of Geology, the National Museum of Nature and Sciences (formerly National Science Museum),
3-23-1 Hyakunincho, Shinjuku-ku, Tokyo 169-0073, Japan (e-mail: kurihara@kahaku.go.jp, kase@kahaku.go.jp)
5Division of Earth and Planetary Sciences, Hokkaido University, N10W8, Kita-ku, Sapporo 060-0810, Japan
(e-mail: hagino@nature.sci.hokudai.ac.jp)
6Department of Geoscience, Interdisciplinary Faculty of Science and Engineering, Shimane University,
1060 Nishikawatsu-cho, Matsue-shi, Shimane 690-8504, Japan (e-mail: hayashi@riko.shimane-u.ac.jp)
Received May 25, 2007; Revised manuscript accepted August 20, 2007
Abstract. A chambered nautilus shell from the early Pleistocene deep-water sediments in the Bolinao area. A chambered nautilus shell from the early Pleistocene deep-water sediments in the Bolinao areaA chambered nautilus shell from the early Pleistocene deep-water sediments in the Bolinao area
of Pangasinan province, northwestern Luzon, Philippines is described. Although the shell is fragmentary,
the shell features indicate that the specimen is referable with reservation to the extant Nautilus pompilius
Linnaeus, 1758. This nding represents the rst and oldest fossil record of N. pompilius and complements
the Plio-Pleistocene gap of the nautiloid fossil records. Taphonomic implications for Cenozoic nautiloids
were briey discussed.
Key words: Nautilus pompilius, Early Pleistocene, Philippines, Nautilidae

Ryoji Wani et al.90
namely, from Lower Pleistocene sediment in Pangas-
inan province of northwestern Luzon, Philippines.
The specimen described here was collected by De
Ocampo in 1979, and is found in the collection of the
National Museum of the Philippines at Manila. Recent-
ly, Aguilar, Zepeda, Kurihara, Kase, and Wani surveyed
the stratigraphic position of the unit that yielded the
specimen, and Hagino and Hayashi analyzed nannofos-
sils and planktonic foraminifers to determine the age of
the unit.
Material and stratigraphy
The specimen discussed herein is in the collection
of the Geology Section of the National Museum of the
Philippines at Manila with registration number NMP-
491B. It was collected from a siltstone unit exposed at
locality TBC-1, on the northeastern corner of Tambac
Island in Tambac Bay, Bani Municipality, Pangasinan,
Philippines (16°15.617´N, 119°55.115´E; Figures 1, 2).
Fierstine and Welton (1983) reported the occurrence of
a fossil black marlin Makaira indica from this site. The
sediment exposed at this site consists of bioturbated,
unconsolidated sandy siltstone, gently dipping to the
west. Well preserved mollusks occur sporadically in
the siltstone beds at this site as well as in beds exposed
along the shore and in sea cliffs around the Tambac Bay
area. Shuto (1983, 1986) postulated that the siltstone
beds in this area were deposited at a depth of ca. 300 m
based on the lithology and associated fossil mollusks.
The fossil-bearing siltstone in the Tambac Bay area is
overlain by uplifted Pleistocene reefal limestone, named
the Bolinao Limestone by Aurelio and Peña (2002).
No previous report has mentioned the presence of the
fossiliferous sediment below the Bolinao Limestone
in the Tambac Bay area, except for Shuto (1986), who
referred it to the Cabatuan Formation without detailed
explanation, and De Ocampo (1983) who named it the
Zaragosa Mudstone. The Cabatuan Formation proper
consists of Plio-Pleistocene shallow marine sediments
in the Iloilo Basin of Panay (Corby et al., 1951; Aurelio
and Peña, 2002). Presumably, Shuto (1986) used this
formation name to refer to the fossil-bearing beds in
the Tambac Bay area because he regarded the fossil-
bearing beds as contemporaneous with the Cabatuan
Formation in the Iloilo Basin. The Neogene clastic unit
in Zambales and Pangasinan provinces was classically
named the Santa Cruz Marl and was later renamed the
Santa Cruz Formation (see Aurelio and Peña, 2002).
Corby et al. (1951) mapped this unit extending over the
western ank of the Zambales range and the Pangas-
inan Peninsula. Karig et al. (1986) surveyed the Santa
Cruz Formation in the Cabaluan area (ca. 50 km south
of the Tambac Bay area), divided it into three members
with a total thickness of ca. 750 m, and dated the upper
member as late Miocene to earliest Pliocene based on
planktonic foraminifers. However, the upper limit of the
Santa Cruz Formation is not exposed in the Cabaluan
area. We presume that the fossil-bearing formation in
the Tambac Bay area is an extension of the uppermost
part of the Santa Cruz Formation. However, the re-
ported age of the Santa Cruz Formation is much older
than the formation in the Tambac Bay area as discussed
below. Additional studies are needed to clarify the stra-
tigraphy of this area.
Two different ages have been given for the fossil-
bearing beds in the Tambac Bay area: Fierstine and
Welton (1983) dated the bed at locality TBC-1 as early
Pleistocene based on planktonic foraminifers, whereas
Shuto (1986) reported the occurrence of planktonic
foraminifers indicative of Blow’s (1969) zone N21 or
thereabouts (Late Pliocene) for the beds in the Tambac
Bay area. To conrm the age of the beds in this bay
area, we analyzed planktonic foraminifers and nanno-
fossils. Figure 2 shows the stratigraphic distributions
of four species of planktonic foraminifers important for
age assignment. Globigerinoides stulosus, which oc-
curs only in the lowest bed in the Tambac Bay area at
Figure 1.. Geographic map showing the position of the fos-
sil locality.

Fossil Nautilus pompilius from Philippines 91
POB-C, has its last occurrence (LO) at 1.77 Ma (Grad-
stein et al., 2004), while Globigerinoides sacculifer is
in all the samples examined and occurs abundantly at
POB-B. This fact strongly suggests that the datum plane
of 1.77 Ma is situated between POB-C and POB-B.
Another age-diagnostic species, Globoturborotalita
obliquus, is found below WLA-1 (Figure 2). The LO of
this species in the Atlantic is 1.30 Ma, but its LO in the
Pacic is still unsettled (Gradstein et al., 2004). Lastly,
Globorotalia tosaensis, whose LO is 0.61 Ma (Gradstein
et al., 2004), occurs throughout the entire stratigraphic
sequence in this area (Figure 2). These age ranges in-
dicate that the age of the bed at locality TBC-1 can be
estimated to range between 1.77 and 0.61 Ma.
Nannofossil analysis of the bed at locality TBC-1
yielded the age-diagnostic species Reticulofenestra
asanoi; however, the unit was devoid of another age-
diagnostic species, Gephyrocapsa parallela. The rst
occurrences of these species are 1.16 and 0.95 Ma, re-
spectively (Sato et al., 1999), which means that the bed
at locality TBC–1 was probably deposited between 1.16
and 0.95 Ma. The nannofossil age range determination
is congruent with the age obtained from the planktonic
foraminifer analysis. Therefore, based on the microfos-
sil age distribution, the age of the bed at locality TBC-1
is early Pleistocene.
Description of specimen NMP-491B
Specimen NMP-491B consists of the two nal
chambers of the phragmocone and a nearly complete
body chamber (ca. 135° in maximum angle; Maximum
Diameter [Max. D] = 160.5 mm). The shell material
is preserved on the body chamber, and the conch is
slightly crushed laterally. The coiling is compressed and
involute (Figure 3). The whorl section is oval (measured
width [W] = 80.1 mm; W/D = 0.50), with broadly
rounded anks. The shell has a very small umbilicus
(ca. 6% of D), and the umbilical callus is seemingly ab-
sent. The shell exterior is smooth with sinuous growth
lines that distinctly outline the hyponomic and ocular
sinuses. The shell color patterns are not preserved. The
siphuncular foramen with retrochoanitic septal necks
is subcentral within the whorl. The suture consists of a
broadly rounded ventral saddle, a broad lateral lobe, a
small saddle in the vicinity of the umbilical shoulder, a
shallow lobe on the umbilical wall, a small saddle near
the umbilical seam, and a dorsal lobe (Figure 4.2). The
septa are adapically convex. Abnormal shell growth and
predatory traces by other organisms are not observed. A
barnacle shell is attached within the posterior part of the
body chamber (Figure 3.2); this position inside the body
chamber indicates the Nautilus individual was dead at
the time of barnacle attachment.
Discussion
Although specimen NMP-491B is only partly pre-
served, the shell bears some diagnostic features that
characterize modern Nautilus pompilius. These char-
acteristics are as follows (Table 1): (1) The shell W/D
ratio of 0.50 closely approximates those of the modern
N. pompilius in the Philippines and N. macrompha-
lus Sowerby, 1849 (0.48–0.52 and 0.52, respectively;
Hirano and Obata, 1979; Tanabe and Tsukahara, 1987),
but the ratio is smaller than those of the Eocene-age N.
praepompilius Shimansky, 1957 (0.60; Saunders et al.,
1996) and N. aff. cookanum Whiteld, 1892 (0.67;
Squires, 1988). (2) The shell involution is the same as
in N. pompilius (Saunders, 1981, 1987), but it is more
evolute in modern Nautilus macromphalus (Saunders,
1987; Ward, 1987) and the fossil N. praepompilius
(Saunders et al., 1996). (3) The size of umbilicus rela-
tive to shell diameter in NMP-491B (ca. 6%) is small
like that seen in modern N. pompilius (ca. 5–9%; Saun-
ders, 1987; Ward, 1987) and the fossil N. aff. cookanum
Figure 2.. Columnar section of the fossil-bearing area
showing the stratigraphic position of the interval that yielded the
Nautilus specimen and the stratigraphic ranges of the planktonic
foraminifers. For localities, see Figure 1.

Ryoji Wani et al.92
Figure 3.. Early Pleistocene specimen of Nautilus cf. pompilius Linnaeus, 1758. 1–4. Right and left lateral, apertural and ventral
views of NMP-491B, from early Pleistocene, Bolinao area, Pangasinan Province, northwestern Philippines, ×0.58. Triangles indicate posi-
tion of last septum. A barnacle shell (10 mm in diameter) is attached within the posterior part of the body chamber.

Fossil Nautilus pompilius from Philippines 93
(ca. 6%; Squires, 1988), but the umbilical size in N.
praepompilius is somewhat larger (ca. 9%; Saunders
et al., 1996), and it is much larger in N. macromphalus
(ca. 15–16%; Saunders, 1987; Ward, 1987).
Although the above-mentioned shell characters t
well both NMP-491B and modern shells of N. pompili-
us, some minor morphological differences are present.
In so far as is known, all the modern and fossil species
of Nautilus have essentially the same elements in suture
lines, but the shape and position of the lateral lobe and
the umbilical saddle differ in each species (Saunders,
1987; Squires, 1988; Saunders et al., 1996). NMP-491B
can be distinguished from N. praepompilius and N.
aff. cookanum in having the lateral lobe situated more
ventrally and the two saddles separated more distantly,
but these elements are almost the same in position in
NMP-491B and modern shells of N. pompilius and
NMP-491B (Figure 4). The only difference is that the
lateral lobe is shallower and the saddle in the umbilical
shoulder is less acute in NMP-491B compared to that
of the modern N. pompilius. Such minor differences are
not considered taxonomically signicant at the species
level in Nautilus at this time. Another difference is that
the small umbilicus of NMP-491B apparently lacks an
umbilical callus. Modern specimens of N. pompilius are
sometimes known to lack an umbilical callus on one or
both sides (Mapes et al., 1979; Saunders, 1981, 1987;
Wray et al., 1995). With only a single fossil speci-
men from the Philippines available for study, it seems
reasonable that specimen NMP-491B could have ab-
normal callus development. For these reasons specimen
NMP-491B can be assigned to N. pompilius with some
reservation. However, if additional Nautilus specimens
are recovered from this interval in the Philippines, and
these specimens are also missing the umbilical callus,
then a taxonomic reassessment must be made. Nautilus
stenomphalus Sowerby, 1849 from the Great Barrier
Reef in Australia also has a small, open umbilicus and
a color pattern that differs slightly from those observed
on N. pompilius. However, it has been suggested that
N. stenomphalus is a variant of N. pompilius (Saunders,
1987; Saunders and Ward, 1987b; Woodruff et al., 1987;
Wray et al., 1995), and it seems to be a reasonable and
conservative course to follow this interpretation at this
Figure 4.. Sutures of modern and fossil Nautilus. 1. Modern
Nautilus pompilius, from Tagnan area, Philippines, at a phragmo-
cone diameter of ca. 130 mm, ×0.72; 2. Early Pleistocene speci-
men of cf. N. pompilius, at a phragmocone diameter of ca. 130
mm, ×0.72; 3. Late Eocene–Early Oligocene N. praepompilius
Shimansky, 1957, at a phragmocone diameter of ca. 50 mm, ×
1.9, reproduced from Saunders et al. (1996); 4. Late Eocene N.
aff. cookanum Whiteld, 1892, at whorl height of 20 mm, ×1.9,
reproduced from Squires (1988). Arrows point toward aperture.
Abbreviations: V, ventral saddle; L, lateral lobe; USh, saddle in
umbilical shoulder; USe, saddle near umbilical seam; D, dorsal
lobe.
Table 1.. Dimensions of shell morphology in the genus Nautilus. Abbreviations: W, shell width; D, shell diameter.
Age W/D Umbilicus diameter/D References
N. cf. pompilius
(NMP-491B)
early Pleistocene 0.50 6% This study
N. pompilius modern 0.48–0.52 5–9% Hirano and Obata (1979),
Tanabe and Tsukahara (1987),
Saunders (1987), Ward (1987)
N. macromphalus modern 0.52 15–16% Saunders (1987), Ward (1987)
N. praepompilius late Eocene–
early Oligocene
0.60 9% Saunders et al. (1996)
N. aff. cookanum late Eocene 0.67 6% Squires (1988)

Ryoji Wani et al.94
time. These detailed comparisons with modern and fos-
sil species of Nautilus demonstrate that NMP-491B can
best be assigned to N. pompilius with reservation.
There is still the intriguing question of why fossil
nautiloids are so scarce in younger Cenozoic sediments
compared with Paleozoic and Mesozoic ammonoids and
nautiloids. In view of the general low population den-
sity in deep waters of modern nautiluses (Saunders and
Ward, 1987a), nektobenthic mode of life (Saunders and
Ward, 1987a), and expected postmortem behavior re-
sulting from delayed waterlogging of air chambers (Wani
et al., 2005; Wani and Ikeda, 2006), shells of Nautilus
may scatter widely around their original habitats. In-
deed, previous observations on sunken shells of modern
Nautilus reect such a distribution (e.g., Roux et al.,
1991). These facts suggest that fossil Nautilus in the
younger Cenozoic had low population densities, similar
to modern nautiluses, which may explain their sporadic
fossil occurrences.
Acknowledgments
We sincerely thank W. J. Mago (Mines and Geosci-
ences Bureau, Philippines) for cooperation in the eld-
work. This study was funded by a grant from the Japan
Society for the Promotion of Science (no. 18253007)
and also by a grant from the National Museum of
Nature and Sciences, Tokyo.
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