Rare Occurrence of Nautilus sp. Fossils from Batangas ......fossils (Figure 2). Sediments prepared for planktonic Figure 1. Geologic map of Talim Point, Lian, Batangas showing the

Keywords: Batangas, Calatagan Formation, fossil, Luzon, Nautilus

Rare Occurrence of Nautilus sp. Fossils from Batangas, Philippines

*Corresponding Author: [email protected]

1Nannoworks Laboratory, National Institute of Geological Sciences College of Science, University of the Philippines

Diliman, Quezon City 1101 Philippines2Geology and Paleontology Division, National Museum of the Philippines

Ermita, Manila 1000 Philippines

3College of Fisheries, President Ramon Magsaysay State University Candelaria, Zambales 2212 Philippines

Two nautilid (Cephalopoda, Mollusca) fossils are discovered from an exposure of the late Miocene – early Pliocene Calatagan Formation in Talim Point, Lian, Batangas, southwestern Luzon. They were identified as Nautilus sp. because of the similarity in conch shape and sutures to those of extant species of Nautilus. The two Nautilus specimens were found in a fine- to medium-grained sandstone unit and observed to be associated with other macrofossils such as corals, gastropods, bivalves, brachiopods, and echinoids. The age of the Nautilus specimens was determined through the analysis of the planktonic foraminifera in the sandstone matrix. These specimens represent the oldest fossil record of Nautilus in the Philippines.

Philippine Journal of Science149 (3): 495-501, September 2020ISSN 0031 - 7683Date Received: 07 Jan 2020

Abigael L. Castro1,2*, Allan Gil S. Fernando1, Alyssa M. Peleo-Alampay1, Geleen Rica S. Javellana1, Dorothy Joyce D. Marquez1,3,

and Jaan Ruy Conrad P. Nogot1,2

INTRODUCTIONIn the Philippines, the first fossil record of a chambered Nautilus (i.e. Nautilus pompilius) was reported by Wani and co-authors (2008). The fossil was found in a siltstone outcrop in Tambac Island, Pangasinan, northwestern Philippines. Based on foraminifera and calcareous nannofossil analyses, the siltstone unit was dated as early Pleistocene. Another N. pompilius fossil was found in Leyte and was dated as Holocene (de Ocampo 2013). Apart from these two findings, no other Nautilus fossils older than early Pleistocene have been reported in the Philippines to date.

During our fieldwork in Talim Point in Lian, Batangas in 2012, a poorly to moderately preserved nautilid shell was found in a sandstone unit, below a limestone outcrop mapped as part of the Calatagan Marl (Ancog 1997; Figure 1). Subsequently, another nautilid specimen was found in the same unit in 2018. The Calatagan Marl is now known as the Calatagan Formation and is composed of lithologies varying from tuffaceous marine siltstones to coralline limestones (MGB 2010). A late Miocene – early Pliocene age was assigned to the Calatagan Formation based on planktonic foraminifera (Castro et al. 2013).

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MATERIALS AND METHODSThe two Nautilus specimens examined were collected during our geologic fieldwork in Talim Point on September 2012 and December 2018. Detailed stratigraphic logging was done to document and describe lithologies and sedimentary structures. A variety of marine macrofossils were recovered together with the two nautilid specimens from the outcrop – such as echinoids, corals, brachiopods, gastropods, and bivalves. All macrofossils were cleaned and photographed for inventory. These fossils are now stored at the Nannoworks Laboratory of the National Institute of Geological Sciences, College of Science, University of the Philippines.

RESULTS

Geology of the AreaThe outcrop is located along a coast that is fringed with coral rubble. The 7.5 m-high outcrop consists of fossiliferous calcarenite, limestone, sandstone, and siltstone beds that have a northwest strike and northeast dip. The lowermost bed hosting the nautilid fossils is around 30 cm thick and consists of coarse-grained sandstones. Apart from the nautilid fossils, this sandstone bed also contains foraminifera, mollusks, and echinoid fossils (Figure 2). Sediments prepared for planktonic

Figure 1. Geologic map of Talim Point, Lian, Batangas showing the location where the two examined Nautilus sp. fossils were found (modified from Ancog 1997). The fossils were recovered from an outcrop belonging to the late Miocene to early Pliocene Calatagan Formation. The location of the Nautilus sp. fossils is indicated by the black circle in Figure 1c.

Figure 2. Stratigraphic profile of the investigated section in Talim Point. Asterisks (*) denote the layers where samples were collected for foraminifera and calcareous nannofossil analyses. The nautilid fossils were observed and collected at the lowermost bed (indicated by the arrow).

Figure 2. Stratigraphic profile of the investigated section in Talim Point. Asterisks (*) denote the layers where samples were collected for foraminifera and calcareous nannofossil analyses. The nautilid fossils were observed and collected at the lowermost bed (indicated by the arrow).

Philippine Journal of ScienceVol. 149 No. 3, September 2020

Castro et al.: Rare Nautilid Fossils

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foraminifera analysis revealed an assemblage consisting of Globorotalia acostaensis, Globorotalia plesiotumida, Pulleniatina obliquiloculata, Sphaeroidinella dehiscens, Globigerinoides ruber, and Globigerinoides obliquus extremus, which suggests a late Miocene – early Pliocene age for the Calatagan Formation based on the Blow Zonation Scheme (Bolli and Saunders 1985) for planktonic foraminifera. Above this bed is a massive limestone unit that contains abundant coral fragments. The limestone is overlain by calcarenite and calcilutite beds that contain echinoids and mollusks. Overall, the Talim Point section can be interpreted as shelfal marine deposits proximal to a reef environment due to the common occurrence of reef-derived bioclasts.

Systematic Paleontology

Class CEPHALOPODA, Cuvier 1758 Subclass NAUTILOIDEA, Agassiz 1847 Order NAUTILIDA, Agassiz 1847 Family NAUTILIDAE, de Blainville 1825 Genus NAUTILUS, Linnaeus 1758 Nautilus sp.

Figures 3–6 and 7(1–2) plus Tables 1 and 2

Material: two fossil casts (Specimens 1 and 2)

Dimensions: see Tables 1 and 2 plus Figure 5

Description of the specimens: The first nautilid specimen (Specimen 1) found in Talim Point is a moderately

Figure 3. Nautilus sp. Specimen 1 embedded in the sandstone unit shown in Figure 2.

Figure 4. Nautilus sp. Specimen 1 excavated from the outcrop; (a) Uneroded left lateral side of conch with preserved sutures; (b) dorsal view; and (c) eroded right lateral side of conch consisting of septate phragmocone and partial body chamber. Possible siphuncle positions are indicated by the arrows on the right lateral side of the conch.

Figure 5. Nautilus sp. Specimen 1 and Specimen 2 measurements: (D) maximum shell diameter; (PD) phragmocone diameter; (U) umbilical diameter; (PL) phragmocone length; (H) whorl height; and (W) shell width. Measurements are presented in Tables 1 and 2.

Figure 6. A slightly smaller specimen of Nautilus sp. (Specimen 2) found in the same outcrop/bed as Specimen 1; (a) left lateral view and (b) dorsal view.



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preserved fossil cast of a fragmented shell without a greater portion of the body chamber (Figures 3 and 4). It measures 9.9 cm in diameter (Figure 5; Table 2). The right lateral side of the phragmocone is partly eroded (Figure 4c), but the left lateral side favorably preserves the uneroded sutures (Figure 4a) and whorl shape (Figure 4a, b). The preserved shell is nautiliconic, involute with a very narrow umbilicus and a rounded venter (Figure 4a, b). The visible sutures consist of a broadly rounded ventral saddle, broad lateral lobe, small saddle in the vicinity of the umbilical shoulder, and a shallow lobe on the umbilical wall. Siphuncle position could not be fully confirmed in the two specimens. In extant Nautilus species, siphuncle position is subcentral. Possible subcentral siphuncle positions are shown in Specimen 1 (Figure 4c). The individual chambers are intact and are filled with sand-sized calcareous sediments. Both the phragmocone and the partial body chamber sections of the shell are apparent and intact in the specimen.

Another nautilid specimen (Specimen 2) was found embedded in the same outcrop and bed as the previous one (Figure 6). The fossil cast is still enclosed in the host rock so that only the left lateral side of the partial phragmocone is visible. The preserved left lateral part of the phragmocone is largely eroded away, but the uneroded early shell portion favorably retains juvenile sutures. Similar to Specimen 1, the chambers are filled with sand-sized calcareous sediments.

DISCUSSION AND CONCLUSIONThe first nautiloid cephalopods appeared during the Cambrian Period (Kummel 1956). Their abundance soon started to decline during the Silurian, and only Orders Orthocerida and Nautilida existed in the Mesozoic (Kummel 1964). The Nautilida survived the end-Cretaceous mass extinction event and flourished again in the Paleogene. However, taxonomic diversity of the Nautilida has significantly declined after the Neogene, and only two genera (Nautilus and Allonautilus) of the Family Nautilidae exist today in tropical and subtropical deeper waters of the Western Pacific and eastern Indian Oceans (Ward et al. 2016a). The evolutionary history of these two extant genera has not yet been fully clarified because of their poor fossil record in the Cenozoic.

Two nautilid genera, e.g. Eutrephoceras of the Nautilidae and Aturia of the Aturidae, are known worldwide in marine Neogene deposits (Kummel 1964). Species of Eutrephoceras generally have a globular conch with broadly rounded venter and slightly sinuous simple

Table 1. Dimensions of shell morphology in modern and fossil species of Nautilus. Abbreviations: W – shell width, D – shell diameter, and U – umbilical diameter. Ratios except for this study are from Wani and co-authors (2008).

Species Age W/D U/D References

Nautilus sp.

Specimen 1late Miocene – early Pliocene

0.93 10.1% This study(W/D measurements for Specimens 1 and 2 are estimated because of preservation condition)

Specimen 2 0.81 17%

N. cf. pompilius early Pleistocene 0.50 6% Wani et al. 2008

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

Table 2. Shell measurements for Specimen 1 and Specimen 2. Figure 5 shows where measurements were taken.

Measurements Specimen 1(in cm)

Specimen 2(in cm)

Maximum shell diameter (D) 9.9 4.7

Phragmocone diameter (PD) 10.4 5.0

Umbilical diameter (U) 1.0 0.8

Phragmocone length (PL) 5.5 2.5

Whorl height (H) 6.5 2.7

Shell width (W) 9.2 3.8



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suture, as observed in E. izumoensis (Yokoyama) from the Miocene of Japan (Yokoyama 1913; Kobayashi 1960) and E. geelongensis (Foord) from the Miocene of South Australia (McGowran 1959). Species of Aturia are characterized by having a discoidal conch with flattened flank and rounded venter and a suture with broad and flattened ventral saddle, narrow pointed lateral lobe, and broadly rounded lateral saddle, as observed in the cosmopolitan species A. cubaensis (Lae) from the Miocene to the early Pliocene (e.g. Schlögl et al. 2011). The two nautilid specimens examined are easily distinguished from any specimens of Eutrephoceras and Aturia by the difference in suture patterns and conch shape. The suture pattern of Specimen 1 is similar to those in species of Nautilus and Allonautilus (Figure 7). However, the small saddle near the umbilical seam and dorsal lobe observed in Nautilus and Allonautilus (Kummel 1964; Ward and Saunders 1997) could not be confirmed in the examined specimens. Shells of Allonautilus species (A. scrobiculatus (Lightfoot) and A. perforatus (Conrad) are characterized by having a relatively wide umbilicus and a quadrate whorl section [see Figures 4 and 7 of Ward and Saunders (1997)]. These features are not observed in the two nautilid specimens examined; hence, the generic position of the two specimens are safely placed in Nautilus. We could not determine the species level relationship of the two specimens because of poor preservation. The narrow umbilicus of the two specimens suggests an affinity to Nautilus pompilius Linnaeus, which is widely known from the Western Pacific ranging from the Philippines in the west to American Samoa in the east. This interpretation should be verified by a future study based on additional, better-preserved specimens. In this paper, we provisionally describe the two nautilid specimens under Nautilus sp.

The fossil record gap for the genus Nautilus and its age controversy were recognized in previous work (e.g. Ward 1984; Wani et al. 2008; Teichert and Matsumoto 2010). Ward (1984) mentioned several studies (i.e. Miller 1947; Shimansky 1962; Kummel 1964) that reported varying age ranges for the genus Nautilus. For Miller (1947), in which Kummel (1956) agrees, the genus Nautilus only includes currently extant species or Eocene–Recent species. However, a later work of Kummel (1964) restricts the Nautilus as an Oligocene-Recent genus. Shimansky (1962), believes that the genus should include all those from the Cretaceous until Recent. However, a later study of Ward and co-authors (2016a) states that the genus Nautilus occurred as far back as the Early Cretaceous (in Australia) and in the Late Cretaceous (in California and British Columbia). Paleocene and Eocene Nautilus were also present in Australia and Great Britain, respectively. The same study also claims that there could be other Nautilus fossils elsewhere that are not yet identified or perhaps identified under the genus Cimomia or Eutrephoceras.

Figure 7. Suture patterns of modern and fossil nautilid species; (1) Specimen 1 (Nautilus sp.) from Batangas, Philippines (this study); (2) Specimen 2 (Nautilus sp.) from Batangas, Philippines (this study); (3) modern Nautilus pompilius from Bohol, Philippines (Wani et al. 2008); (4) fossil N. cf. N. pompilius from Pangasinan, Philippines (Wani et al. 2008); (5) Nautilus praepompilius from Victoria, Australia (Ward et al. 2016b); and (6) N. pompilius from Papua New Guinea (Ward et al. 2016b). Abbreviations: V – ventral saddle, L – lateral lobe, and D = dorsal lobe. Arrows point toward the aperture. Figure modified from Wani et al. (2008) and Ward et al. (2016b).

The genus Nautilus is phenotypically variable and is relatively immune to forming new species even under genetic isolation (Ward et al. 2016a). The transition from N. praepompilius (Paleogene) to modern Nautilus could be a product of a long-term phyletic evolution producing more compressed shells gradually over time.

Available fossil records show that Nautilus praepompilius Shimansky 1957 is the oldest known species of Nautilus. This species was first described from the late Eocene of Kazakhstan (Shimansky 1957; Saunders et al. 1996). Subsequently, its occurrence was confirmed in the



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Paleocene of Victoria, South Australia (Ward et al. 2016b), and possibly in the Turonian to Maastrichtian (Upper Cretaceous) of California (Ward et al. 2016a). Another species of Nautilus, N. cookanum Whitfield was described from the upper Eocene Cowlitz Formation of Washington, USA (Ward and Saunders 1997).

In Southeast Asia, fossil records of Nautilus are known in Java, Indonesia (Martin 1880) and the Philippines (Wani et al. 2008). The Indonesian Nautilus fossil was described under N. javanus Martin 1880, and its age was believed to be late Miocene (Martin 1880). In the Philippines, fossil specimens of N. pompilius Linnaeus were reported from the Pleistocene of Pangasinan and the Holocene of Leyte (Wani et al. 2008).

This new discovery of Nautilus specimens from the Neogene deposits in Batangas is important in understanding the evolutionary history of this genus. It was previously believed that nautilids do not have any fossil record during the Pliocene and Pleistocene (Kummel 1956). The fossils discovered in Batangas so far represent the oldest fossil Nautilus in the Philippines and the only late Miocene to the early Pliocene record of Nautilus in the world.

ACKNOWLEDGMENTSWe would like to acknowledge the extensive and comprehensive suggestions and comments of the anonymous reviewers, which greatly improved the manuscript. Our sincere thanks to Dr. Tomoki Kase (Kanagawa University) for his valuable insights. Acknowledgment is due also to the 2012 Matabungkay fieldwork participants of the NIGS Nannoworks Laboratory (John Warner Carag, Raquel Felix, Maria Paola Grajo, Clarence Magtoto, Regina Marie Maximo, Kristina Rochelle Montalbo, Ma. Angelica Peña, Dianne Jules Rosario, Jolly Joyce Sulapas, and Kerve Supnet) and the Geology 131 (Micropaleontology) Class of 2018 of the National Institute of Geological Sciences, University of the Philippines.

STATEMENT ON CONFLICT OF INTERESTThe authors have no conflict of interest to declare.

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Rare Occurrence of Nautilus sp. Fossils from Batangas ......fossils (Figure 2). Sediments prepared for planktonic Figure 1. Geologic map of Talim Point, Lian, Batangas showing the