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Home , Aturia, Calatagan, Hoko River Formation, Leyte (province), Nautilida

Philippine Journal of Science 149 (3): 495-501, September 2020 ISSN 0031 - 7683 Date Received: 07 Jan 2020

Rare Occurrence of sp. Fossils from ,

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

1Nannoworks Laboratory, National Institute of Geological Sciences College of Science, University of the Philippines Diliman, City 1101 Philippines 2Geology and Paleontology Division, National Museum of the Philippines Ermita, 1000 Philippines 3College of Fisheries, President Ramon Magsaysay State University Candelaria, 2212 Philippines

Two nautilid (Cephalopoda, ) fossils are discovered from an exposure of the late – early Pliocene Formation in Talim Point, Lian, Batangas, southwestern . 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.

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

INTRODUCTION During our fieldwork in Talim Point in Lian, Batangas in 2012, a poorly to moderately preserved nautilid shell In the Philippines, the first fossil record of a chambered was found in a sandstone unit, below a limestone outcrop Nautilus (i.e. Nautilus pompilius) was reported by Wani mapped as part of the Calatagan Marl (Ancog 1997; Figure and co-authors (2008). The fossil was found in a siltstone 1). Subsequently, another nautilid specimen was found in outcrop in Tambac Island, , northwestern the same unit in 2018. The Calatagan Marl is now known Philippines. Based on foraminifera and calcareous as the Calatagan Formation and is composed of lithologies nannofossil analyses, the siltstone unit was dated as varying from tuffaceous marine siltstones to coralline early Pleistocene. Another N. pompilius fossil was found limestones (MGB 2010). A late Miocene – early Pliocene in and was dated as Holocene (de Ocampo 2013). age was assigned to the Calatagan Formation based on Apart from these two findings, no other Nautilus fossils planktonic foraminifera (Castro et al. 2013). older than early Pleistocene have been reported in the Philippines to date.

*Corresponding Author: [email protected]

495 Philippine Journal of Science Castro et al.: Rare Nautilid Fossils Vol. 149 No. 3, September 2020

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.

MATERIALS AND METHODS The 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.

Figure 2. Stratigraphic profile of the investigated section in Talim Point. Asterisks (*) denote the layers where samples were RESULTS collected for foraminifera and calcareous nannofossil analyses. The nautilid fossils were observed and collected at the lowermost bed (indicated by the arrow). Geology of the Area The 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 Figure 2. Stratigraphic profile of the investigated section in Talim Point. Asterisks (*) denote the layers where samples were is around 30 cm thick and consists of coarse-grained collected for foraminifera and calcareous nannofossil sandstones. Apart from the nautilid fossils, this sandstone analyses. The nautilid fossils were observed and collected bed also contains foraminifera, mollusks, and echinoid at the lowermost bed (indicated by the arrow). fossils (Figure 2). Sediments prepared for planktonic

496 Philippine Journal of Science Castro et al.: Rare Nautilid Fossils Vol. 149 No. 3, September 2020 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 Figure 4. Nautilus sp. Specimen 1 excavated from the outcrop; to a reef environment due to the common occurrence of (a) Uneroded left lateral side of conch with preserved reef-derived bioclasts. 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 Systematic Paleontology by the arrows on the right lateral side of the conch. Class CEPHALOPODA, Cuvier 1758 Subclass NAUTILOIDEA, Agassiz 1847 Order , 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 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. Figure 3. Nautilus sp. Specimen 1 embedded in the sandstone unit shown in Figure 2.

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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 1 0.93 10.1% This study late Miocene – early (W/D measurements for Specimens Pliocene 1 and 2 are estimated because of Specimen 2 0.81 17% preservation condition)

N. cf. pompilius early Pleistocene 0.50 6% Wani et al. 2008 Hirano and Obata 1979; N. pompilius Modern 0.48–0.52 5-9% Tanabe and Tsukahara 1987; Saunders 1987; Ward 1987 N. macromphalus Modern 0.52 15-16% Saunders 1987; Ward 1987 late – early N. praepompilius 0.60 9% Saunders et al. 1996 Oligocene N. aff. cookanum late Eocene 0.67 6% Squires 1988

Table 2. Shell measurements for Specimen 1 and Specimen 2. Figure Another nautilid specimen (Specimen 2) was found 5 shows where measurements were taken. embedded in the same outcrop and bed as the previous Measurements Specimen 1 Specimen 2 one (Figure 6). The fossil cast is still enclosed in the (in cm) (in cm) host rock so that only the left lateral side of the partial Maximum shell diameter (D) 9.9 4.7 phragmocone is visible. The preserved left lateral part of Phragmocone diameter (PD) 10.4 5.0 the phragmocone is largely eroded away, but the uneroded early shell portion favorably retains juvenile sutures. Umbilical diameter (U) 1.0 0.8 Similar to Specimen 1, the chambers are filled with sand- Phragmocone length (PL) 5.5 2.5 sized calcareous sediments. Whorl height (H) 6.5 2.7 Shell width (W) 9.2 3.8 DISCUSSION AND CONCLUSION preserved fossil cast of a fragmented shell without a The first appeared during the greater portion of the body chamber (Figures 3 and 4). Period (Kummel 1956). Their abundance soon It measures 9.9 cm in diameter (Figure 5; Table 2). The started to decline during the , and only Orders right lateral side of the phragmocone is partly eroded and Nautilida existed in the (Figure 4c), but the left lateral side favorably preserves (Kummel 1964). The Nautilida survived the end- the uneroded sutures (Figure 4a) and whorl shape (Figure mass extinction event and flourished again 4a, b). The preserved shell is nautiliconic, involute with a in the Paleogene. However, taxonomic diversity of the very narrow umbilicus and a rounded venter (Figure 4a, Nautilida has significantly declined after the Neogene, b). The visible sutures consist of a broadly rounded ventral and only two genera (Nautilus and ) of the saddle, broad lateral lobe, small saddle in the vicinity of Family Nautilidae exist today in tropical and subtropical the umbilical shoulder, and a shallow lobe on the umbilical deeper waters of the Western Pacific and eastern Indian wall. Siphuncle position could not be fully confirmed in Oceans (Ward et al. 2016a). The evolutionary history of the two specimens. In extant Nautilus species, siphuncle these two extant genera has not yet been fully clarified position is subcentral. Possible subcentral siphuncle because of their poor fossil record in the . positions are shown in Specimen 1 (Figure 4c). The Two nautilid genera, e.g. of the Nautilidae individual chambers are intact and are filled with sand- and of the Aturidae, are known worldwide in sized calcareous sediments. Both the phragmocone and marine Neogene deposits (Kummel 1964). Species of the partial body chamber sections of the shell are apparent Eutrephoceras generally have a globular conch with and intact in the specimen. broadly rounded venter and slightly sinuous simple

498 Philippine Journal of Science Castro et al.: Rare Nautilid Fossils Vol. 149 No. 3, September 2020 , 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 Figure 7. Suture patterns of modern and fossil nautilid species; (1) should be verified by a future study based on additional, Specimen 1 (Nautilus sp.) from Batangas, Philippines better-preserved specimens. In this paper, we provisionally (this study); (2) Specimen 2 (Nautilus sp.) from Batangas, describe the two nautilid specimens under Nautilus sp. Philippines (this study); (3) modern Nautilus pompilius from , Philippines (Wani et al. 2008); (4) fossil The fossil record gap for the genus Nautilus and its age N. cf. N. pompilius from Pangasinan, Philippines (Wani controversy were recognized in previous work (e.g. Ward et al. 2008); (5) Nautilus praepompilius from Victoria, 1984; Wani et al. 2008; Teichert and Matsumoto 2010). Australia (Ward et al. 2016b); and (6) N. pompilius from Ward (1984) mentioned several studies (i.e. Miller 1947; Papua New Guinea (Ward et al. 2016b). Abbreviations: V – ventral saddle, L – lateral lobe, and D = dorsal lobe. Shimansky 1962; Kummel 1964) that reported varying Arrows point toward the aperture. Figure modified from age ranges for the genus Nautilus. For Miller (1947), in Wani et al. (2008) and Ward et al. (2016b). 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 genus Nautilus is phenotypically variable and is the Nautilus as an Oligocene-Recent genus. Shimansky relatively immune to forming new species even under (1962), believes that the genus should include all those genetic isolation (Ward et al. 2016a). The transition from from the Cretaceous until Recent. However, a later study of N. praepompilius (Paleogene) to modern Nautilus could Ward and co-authors (2016a) states that the genus Nautilus be a product of a long-term phyletic evolution producing occurred as far back as the Early Cretaceous (in Australia) more compressed shells gradually over time. and in the Late Cretaceous (in California and British Columbia). and Eocene Nautilus were also Available fossil records show that Nautilus praepompilius present in Australia and Great Britain, respectively. The Shimansky 1957 is the oldest known species of Nautilus. same study also claims that there could be other Nautilus This species was first described from the late Eocene of fossils elsewhere that are not yet identified or perhaps Kazakhstan (Shimansky 1957; Saunders et al. 1996). identified under the genus Cimomia or Eutrephoceras. Subsequently, its occurrence was confirmed in the

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