Cypraeidae of the Indo-Pacific: Cenozoic Fossil History and Biogeography

BULLETIN OF MARINE SCIENCE, 47(1): 23-34, 1990

CYPRAEIDAE OF THE INDO-PACIFIC: CENOZOIC FOSSIL HISTORY AND BIOGEOGRAPHY

E. Alison Kay

ABSTRACT The cowries (Cypraeidae) of the Indo-Pacific are described in terms of their origins in the Tethys and Indonesian Tertiary, and their distribution in space in the Tertiary and today. Twenty-one species groups are identified in the discussion. The earliest Indo-Pacific cowries are recorded in the Palaeocene of Pakistan and India, then part of the Tethys Sea. In Indonesia the earliest cowries are Middle Miocene. Six of 18 species groups were represented in Pakistan- India. First occurrence of four species groups occurs in Indonesia; six groups appear contemporaneously in the Pacific and in Australia. Five groups present in the Indonesian Miocene and Pliocene are now extinct in Indonesia, although species in two groups, Barycypraea and Zoila, live today in the Indian Ocean and Australia respectively. The distribution of cowries in the Indo-Pacific is not random. The patterns of spatial distribution in the fossil record and of Recent endemism in the central Pacific and Indian Ocean indicate speciation occurred beyond the geographical boundaries of the Malay Archipelago and provide support for Ladd's hypothesis of the importance of peripheral speciation in the Indo-Pacific.

The question is deceptively simple: what is the relationship of the Recent Cypraeidae (true cowries) of the Indo-Pacific to the Indonesian Tertiary? The question stems from Ekman's (1953: 18) thesis that the Indo-Malayan archipelago is "centre and focus from which the others recruited its fauna" (see also Briggs, 1974). More than 80 species of fossil cowries are reported from the Indonesian Tertiary, and it seems a reasonable assumption that knowledge of the history of these cowries can provide some insight into paleobiogeography and evolution in the Indo-Pacific biota. The following account is a first approximation, in a purely descriptive mode, towards answering the question. The Indonesian cowrie fauna is described in terms of its origins, its composition over time, and its distribution in space both in the Tertiary and today.

SOURCES OF DATA AND CAVEATS

This review, which involves about 250 species level taxa and 25 species complexes, has been assembled from a variety of sources. The major fossil collections studied are those of Pakistan, India and Burma described by Forbes, Sowerby, Vredenburg and others in the 19th century, and now in the British Museum (Natural History), and the Indonesian Tertiary cowries in the Martin Collection, Rijksmuseum fUr Geologie, Leiden. Collections of Recent cowries in the B. P. Bishop Museum, Honolulu, Hawaii; the British Museum (Natural History), London; C. M. Burgess collection, Honolulu, Hawaii; California Academy of Science, San Francisco, California; the U.S. National Museum of Natural History, Washington, D.C., and the Zoologisch Museum, Universitet Amsterdam, provided much of the data for present distribution records. For purposes of dating the Pakistan-India-Burma and Indonesian Tertiary faunas, Shuto's (1975; 1976; 1984) correlations of Neogene formations of southeast and south Asia have been followed. I also follow Shuto (1976) in applying a broad brush to the history of the cowries: Shuto notes that while molluscan faunas within a given subprovince (for example, Pakistan and Burma) can be correlated stage to stage, inter-subprovincial correlations (between Pakistan and Indonesia) can only be described by broad terminologies such as Middle Miocene, Upper Miocene, Pliocene, etc. Shuto's (1976) subprovince of Pakistan, India, and Burma is here referred to as Pakistan-India. The term "Indonesia" is used in referring to the Miocene to Pliocene fossils of that area, and Malay Archipelago (encompassing Indonesia and the Philippines) is used sensu Ekman (1953) for Recent distributional records. Terminology for the distribution of Recent cowries in the Indo-Pacific, Indo-West Pacific, and Western Pacific is that of Springer (1982). Indo-Pacific refers to "the Indian Ocean including contiguous

23 24 BULLIETIN OF MARINE SCIENCE, VOL. 47, NO. I, 1990

Table I. Species groups in the Cypraeidae represented in the Indo-Pacific, Pakistan-India, and In- donesian Tertiary. * = group extinct. Eras: Mio, Miocene; Olig, Oligocene; Plio, Pliocene; Rec, Recent. Locales: Afr, Africa; Austr, Australia; Carib, Caribbean; CP, Central Pacific; Ene, Marshall Islands; Indon, Indonesia; 10, Indian Ocean; IWP, Indo-west Pacific; Jap, Japan; Mal, Malay Archipelago; Med, Mediterranean; NZ, New Zealand; Okin, Okinawa; Pak-Ind, Pakistan-India; Sind, South India; WArn, Western Americas; WP, Western Pacific. Characters: ap, aperture; bc, bursa copulatrix; dent, denticle; foss, fossula; into bract, internal bract; Rad, radula

Barycypraeat Foss. ribbing obsolete. Mantle brown, black. Mio: Pak-Ind., Indon, Carib. Rec: I 10, 1 Rad. tooth shaft: lateral internal bracts, later- Carib. Shell 30-60 mm; depressed; ap. den- al basal dent. Females: bc. tate or edentate. Foss. smooth. Mantle thin, Lyncina mottled tan. Rad. tooth shaft: paired basal Mio: Pak-Ind, Indon., Fiji, Guam. Rec: 4 IP, dent., into bract. Females: bc. Dev. direct. 310, 4WP, 7 CPo Shell 30-70 mm, cylindri- Bistolida calor pyriform; ap. teeth usually across base. Plio: Indon. Rec: 7 IP, 1 Mal, 3 CPo Shell 13- Foss. ribbed. Mantle dark, gray/brown. Cen- 26 mm; cylindrical, ovate; ap. teeth barely on tral rad. tooth domed; Rad. tooth shaft: no base. Foss. ribbed. Mantle gray/pale yellow. basal dent. or bracts. Females: bc. Rad. tooth shaft: no basal dent. Females: be. Mauritia Blasicrura Mio: Indon; Plio: New Hebrides, Tonga. Rec: Plio: Indon. Rec: I Mal, 4 IWP; I 10, I WP. 5 IP, 2 10, I CPo Shell 35-100 mm; mar- Shell 12-20 mm; pyriform-ovate; ap. teeth on gined; ap. teeth confined to ap. Foss. ribbed. base. Foss. ribbed. Mantle dark, gray-brown. Rad. tooth shaft: paired basal dent., internal Rad. tooth shaft: no basal dent. Females: be. and subtending bracts. Females: no bc. Chelycypraea Miolyncina* Rec: liP. Shell 100 mm; inflated; ap. teeth Eoc.-Mio. Pak-Ind, Indon. Shell 30-60 mm; confined to ap. Foss. ribbed. Mantle transpar- ovate; ap. v-shaped, labrum declivous; ap. ent. Rad. tooth shaft: no basal dent. or inter- teeth confined to ap. and in post. channel. nal bract; laterals reduced. Females: be. Foss. ribbed. Cribrarula Nesiocypraeat Mio: Indon, Fiji, Jap. Rec: liP, 1 WP, 4 10, Rec: 6 WP. Shell 30-50 mm, pyriform; ap. 4 CPo Shell 15-30 mm; ovate, cylindrical; teeth confined to ap. Foss. smooth. Rad. margined; ap. teeth on base. Foss. absent or tooth shaft: with medial dent., into bract. ribbed. Mantle crimson. Rad. tooth shaft: paired basal dent. Females: be. Notadusta L. Olig: NZ; Mio: Indon, Austr. Rec: 3 WP. Cypraea Shell 15-24 mm; ovate, rostrate; ap. teeth Mio: Indon., Guam. Rec: 2 [P, 2 10. Shell confined to ap. Foss. smooth. Col. smooth 75-100 mm; cylindrical-inflated; ap. teeth confined to ap. Foss. ribbed. Mantle gray- Ovatipsa brown. Rad. tooth shaft: basal dent., into Mio: Indon. Rec: liP, I 10. Shell 20-30 bract. Females: bc. mm; pyriform; ap. teeth coarse, across base. Foss. ribbed. Rad. tooth shaft: no basal dent. Erosaria Female: no bc. Mio: Pak-Ind, Indon, Fiji, Guam. Rec: 13 IP, I 10, 10 CPo Shell 10-50 mm; col. margin Proadusta* pitted; ap. teeth on base. Foss. ribbed. Mantle Mio: Pak-Ind, Indon. Described by Schilder dark, brown/gray. Rad. tooth shaft: single (1939) but not easily distinguished from other basal dent.; internal, subtending bracts. Fe- genera. males: no bc. Purpuradusta Erronea Plio: Indon. Rec: 4 IP, 5 IWP, I CPo Shell 6- Mio: Pak-Ind, Indon, Fiji, Ene. Rec: 7 IP, 4 20 mm, cylindrical; ap. teeth confined to ap. IWP, 7 WP, I Mal. Shell 20-40 mm; pyri- Foss. ribbed. Mantle red. Rad. tooth shaft: form, ovate; ap. teeth on base. Foss. ribbed. paired basal dent. Females: no bc. Mantle dark, brown/gray. Rad. tooth shaft: Pustularia paired basal dent., int. bract. Females: no bc. Mio: Indon, Fiji. Rec: 5 IP, I CPo Shell 15-20 Luria mm; globular to inflated-ovate; ap. finely Mio: Pak-Ind, Indon, Fiji. Rec: liP, I CP, I dentate, teeth on base. Foss. smooth. Mantle 10, I Carib., I WArn. Shell 25-40 mm; cy- yellow, gray. Rad. tooth shaft: paired basal lindrical, pyriform; ap. teeth confined to ap. dent. KAY: BIOGEOGRAPHY OF INDO-PACIFIC CYPRAEIDAE 25

Table I. Continued

Ta/paria confined to ap. Foss. ribbed. Mantle red. Plio: Indon, Fiji, Okin, E. Afr. Rec: lIP, I Central rad. tooth domed; rad. tooth shaft: no 10. Shell 60-70 mm; cylindrical-ovate; ap. basal denticles. Females: bc. teeth confined to ap. Foss. ribbed. Mantle Zoi/a dark. Rad. tooth shaft: paired basal denticles, OIig-Mio: Austr. SInd; Plio: Indon. Rec: 5 into bract. Females: bc. Austr. Shell 45-100 mm; ovate, subpyriform, Ta/osto/ida humped; margined; ap. weakly dentate. Foss. Pleist: Indon. Rec.: lIP, 2 CPo Shell 10-25 smooth. Rad. tooth shaft: paired basal dent., mm; ovate, cylindrical; margined; ap. teeth internal and subtending bracts. Females: bc. t I agree with Liltved and Le Roux (1988) that Cypraea mus is a relict Barycypraea and not Siphocypraea as defined by Petuch (1979). * Luque (1980) suggests that the western Pacific deepwater cowries be included with Cypraea pyrom and other Atlantic cowries in Schilder;a. Nesiocypraea is recognized as distinct here until more anatomical evidence is available.

seas, and the Pacific Ocean as far east as Easter Island but excluding the area occupied by the coast and offshore islands ... ofthe Western Hemisphere" (Springer, 1982). Indo-West Pacific refers to the Indian Ocean and the western Pacific. By western Pacific is meant the Pacific Ocean west of the western margin of the Pacific lithospheric plate which includes inland seas such as the South China Sea, Arafura Sea, and Coral Sea. Central Pacific refers to cowrie distribution primarily on non-marginal portions of the Pacific Plate, although some central Pacific cowries may encroach in the western Pacific.

COWRIES: SPECIES COMPLEXES AND BIOLOGY The mesogastropod family Cypraeidae, the "true cowries," of which there are about 200 Recent species, is represented by about 150 species in the Indo-Pacific, and 50 species restricted to the Mediterranean, coast of West Africa, South Africa, Caribbean, west coast of the Americas, and south and western Australia. The Indo-Pacific cowries are arranged in 18 species groups (Table 1) recognized on the basis of anatomical characters, as well as characters of the protoconch and adult shell. The species groups listed are modifications of the genera and subgenera recognized by Schilder (1927; 1932) and Schilder and Schilder (1938-39; 1971) (and see Wilson and McComb, 1967; Kay, 1981; 1985; Gosliner and Liltved, 1985). Present evidence suggests that the species groups recognized here may be monophyletic groups or clades, but they are here regarded simply as groups of related species. Most of the Indo-Pacific cowries have geographic ranges and depth distribution similar to those of hermatypic corals. Highest diversity is between 300N and 300S (Stehli, 1968), and most cowries are found at depths of less than 30 m. The assemblages in which fossil cowries are found indicate that similar associations existed at least from the Palaeocene. Fossil assemblages from which cowries have been described from the Upper Ranikot (Palaeocene) and Gaj (Eocene) beds of Pakistan and Miocene beds of Qui lon, India and Indonesia include other mollusks, corals, and echinoderms characteristic of coral reef associations today. There are exceptions to the coral reef association, however: among Recent cowries, Erronea barclayi of the Indian Ocean and Lyncina joycae of the South China Sea occur at depths of more than 150 m, and species of Nesiocypraea from the South China Sea are known from depths of 140-> 350 m (Burgess, 1985). Developmental patterns for most Indo-Pacific cowries appear to include a veliger larval stage that is probably planktonic for periods of at least some weeks. Pelagic veliger larvae of Erosaria, Lyncina, Purpuradusta and Talparia in Hawaii (Taylor. 1975) are in the plankton for 1.5 to 2 weeks. Scheltema (1986) reports cypraeid larvae in about 13% of plankton tow stations in the Central Pacific. 26 BULLETIN OF MARINE SCIENCE, VOL. 47, NO.1, 1990

Direct development in which post-metamorphic juveniles emerge directly from the egg capsule is reported for cowries from the temperate waters of southern Western Australia (Wilson, 1985), several South African cowries (Gosliner and Liltved, 1985), and the Caribbean Barycypraea mus (Anonymous, 1981).

FOSSIL HISTORY OF THE CYPRAEIDAE Early History. - The ancestors of the present day cowries are thought to be represented in the Jurassic of southern Europe by Zitellia (Columbellinidae) (Taylor and Walls, 1975). The oldest recognizable Cypraeidae are two species from the late Jurassic or early Cretaceous of Sicily, Palaeocypraea tithonica and P. gemel- laroi, both of di Stefano 1882. From their first appearance in what was then the Tethys Sea, cowries appeared in Africa and North and South America in the Cretaceous. Their geographical distribution from the Cretaceous to the mid-Eocene is markedly cosmopolitan: Palaeocypraea, Bernaya, and Gisortia are all recorded from the Mediterranean, Caribbean, western America, and Pakistan-India. Species groups from the Eocene to Recent show more restricted regional patterns: seven of ten species groups appearing in the Miocene occur in one or two areas (the Indo-Pacific and Australia) and all but one of nine species groups from the Pliocene to Recent time is restricted to the Indo-Pacific. The evolution of the Indo-Pacific fauna can be traced to the ancient Tethys seaway which, from Triassic to Miocene time, connected the Mediterranean and Indo-Pacific across what is now the Middle East and Pakistan. The seaway was closed in the Early Miocene (Adams, 1981), and the faunas of the Mediterranean and the Indo-Pacific evol.ved separately. Cowries of Pakistan- India. - The earliest cowries of Pakistan-India are recorded in the Palaeocene Cardita beaumonti beds of the Upper Ranikot of Pakistan. Cowries become increasingly diversified in the region up to the closure of the Tethys: 25 species in six species groups are recorded for the Paleocene-Eocene and 19 species in eight species groups (Table 2) occur in the Miocene of Pakistan, South India, and Burma. Seven of these species groups are first occurrences.

INDONESIAN FOSSIL RECORD Miocene. - In Indonesia the earliest recognizable molluscan faunas are middle Miocene (Shuto, 1976); earlier strata (Te5) are mainly argillaceous and contain no significant molluscan assemblages. Miocene and Pliocene faunas are shown in Tables 1 and 2 and Figure lA and B. The Miocene is the richest of the Indonesian Tertiary cowrie faunas, with 13 species groups and about 50 species. Six of the species groups were present in Pakistan-India; four species groups appear contemporaneously in the Middle Miocene (letter stage Tf) of Fiji (Ladd, 1977), one in Okinawa (MacNeil, 1960), one in Guam (Ladd, 1977), and one in Australia (Darragh 1985). Only one species group, Mauritia, is first recorded in the Indonesian Miocene. Barycypraea and Erosaria, each with 10 nominal species, are the dominant species groups; Erronea with 8 species and Miolyncina with 5 are next in dominance rank. Barycypraea is not only numerous in species, but also in abundance. There are about 13 specimens of Barycypraea per species in the Martin collection compared with an average of 7 specimens per species in the other species groups. Pliocene and Pleistocene. -Species composition in the Pliocene and Pleistocene is quite different from that in the Miocene, and fewer species groups and species KAY: BIOGEOGRAPHY OF INDO·PACIFIC CYPRAEIDAE 27

Table 2. Geographic and geologic distribution of species groups and number of species (in parentheses) in the Tertiary of Pakistan-India, Indonesia, and the Pacific. Data from Schilder and Schilder 1971; Ladd 1977, 1982; MacNeil 1960

Pakistan Japan Marshall Species group India Indonesia Okinawa Fiji Guam Islands Hawaii Miocene Barycypraeat (5) (10) Cypraea (2) (I) Cribraru/a (I) (I) Luria (I) (2) (I) Lyncina (3) (2) Erosaria (I) (10) (2) (1) Fossacypraea* (5) Pustularia (3) (2) Erronea (4) (8) (I) Mauritia (I) Miolyncina* (I) (5) Notadusta (2) Ovatipsa (I) Proadusta* (1) (1) Zoila* (I) Pliocene Bistolida (2) Blasicrura (I) Cribraru/a (I) (I) (I) Cypraea (I) Erosaria (11) (3) (2) (3) Erronea (9) (3) Luria (I) (I) (I) Lyncina (3) (2) (2) Purpuradusta (2) Pustu/aria (I) (2) Talostolida (I) Talparia (I) (I) (I) Zoila (I) Pleistocene Bistolida (2) Blasicrura (1) Cribraru/a (I) Cypraea (I) Erosaria (6) (3) (I) (6) Erronea (12) (I) Luria (I) Lyncina (I) (1) (I) (6) Mauritia (I) (3) Purpuradusta (3) (I) Pustu/aria (I) (I) Ta/ostolida (I) (1) (I) Talparia (I) Zoila (I) • = Extinct. t Barycypraea has been extinct in Indonesia since the Pliocene but three species survive today, B. fultoni from South African waters, B. (euler; in the Red Sea, and B. mus in the Caribbean. ; ZoUa which is known from the Miocene of India and Pliocene and Pleistocene of Indonesia is extinct in Indonesia today but sUTVives in southwestern Australia. are recorded (Table 2, Fig. lA, B). Three of the Miocene species groups are extinct by Pliocene time, and only 2 species of the lO surviving Miocene species groups are represented in the Pliocene and Pleistocene. Erosaria (34% of the species assemblage) and Erronea (27% of the assemblage) are dominant. Five species 28 BULLETIN OF MARINE SCIENCE, VOL. 47, NO. I, 1990

17 12 EXTINCT SPECIES MIOCENE PLIOCENE ,. COMPLEXES 11 15 ~ INDONESIA ~ INDONESIA

14 • PACIFIC • PACIFIC OTHER 13 : 12 ·u 11 EROS ARIA LYNCINA ~ 10 '" a .• 1: 7 5 OTHER z

lSpecies••••Complell9S Species Complexes Figure 1 lA (left). Species composition in the Miocene ofIndonesia and the Pacific. Extinct complexes include Barycypraea, }Jiolyncina and Proadusta. Other complexes are Cypraea, Cribrarula, Mauritia, Notadusta and Ovatipsa. Pacific includes Fiji, Guam, Marshall Islands, and Okinawa. IB (right). Species composition in the Pliocene ofIndonesia and the Pacific. Other complexes are Bistolida, Blasicrura, Cribrarula, Cypraea, Purpuradusta, Talostolida, Talparia, and Zoila with one or two species in each. Pacific includes Fiji, Guam, Enewetak, Marshall Islands, and Okinawa. groups are recorded for the first time, of which one (Talparia) appears contemporaneously in the Pliocene of Guam (Ladd, 1977) and Okinawa (MacNeil, 1960). Zoila is first recorded in Indonesia in the Pliocene but there are earlier records for this species group in the Late Oligocene-Middle Miocene of Australia (Dar- ragh, 1985) and the Upper Miocene Quilon beds ofIndia (Dey, 1962). In the Pleistocene record of 10 species groups and 29 species, Erronea with 12 species is dominant. There is one Pleistocene extinction in Indonesia, Zoila, which in Recent time has a restricted distribution in the temperate waters of Western Australia (Wilson and McComb, 1967).

TERTIARY COWRIES IN THE PACIFIC Tertiary fossils from the Pacific are summarized in Ladd (1977; 1982). The largest number of Miocene cowries occurs in Fiji (four species groups, seven species) (Fig. 1A). One species each in Cribrarula and Cypraea is also recorded from Okinawa (MacNeil, 1960) and Guam (Ladd, 1977), and one species each in two species groups, Erosaria and Erronea is recorded from Enewetak, Marshall Islands (Ladd, 1977). Three species are found in common with Indonesia but all were extinct by the Pliocene: Cribrarula cincta in Japan, Erronea kamai in the Marshall Islands and Pustularia everwijni in Fiji. The remaining six Miocene species survive today. The Pliocene record shows an increase in the number of species complexes (Fig. lB); and Indo-Pacific cowries are also recorded from East Africa (Cox, 1930). The Pleistocene record from East Africa to Hawaii is a prediction of the modern record: more than half of the Recent cowries recorded from Hawaii are also known from Pleistocene reefs in the area, and endemic species such as Luria tessellata and Cribrarula gaskoini in Hawaii and Talparia exusta in the Indian Ocean (Bom et al., 1982) have clearly differentiated.

RECENT FAUNA Fifteen species groups with fossil records in the Indonesian Tertiary comprise part of what is today the Indo-Pacific cowrie fauna; two species groups which do not have confirmed fossil records are also part of that fauna (Table 1). Neither KAY: BIOGEOGRAPHY OF INDO-PACIFIC CYPRAEIDAE 29

Table 3. Geographic distribution of Indo-Pacific cowries (INDO-PAC, Indo-Pacific; MALAY, Malay Archipelago, IWP, Indo-West Pacific; 10, Indian Ocean; WP, Western Pacific; CP, Central Pacific; END, Endemic)

Malay No. Indo-Pac. Arch. IWP 10 WP CP END Region Species (%J (%J <%) ('!OJ <%) ('!OJ (%J Malay Arch. 79 62 8 8 14 6 <2 West. Pac. 83 61 14 5 20 Central Pac. 87 56 6 38 Indian O. 79 62 9 29 species groups nor species of cowries are uniformly distributed in the Indo-West Pacific. Forty-nine species in 14 species groups are widespread (e.g., "Indo-Pa- cific"). Other species groups are restricted to the Malay Archipelago, western Pacific, central Pacific and Indian Ocean (Kay, 1985) (Table 3). Malay Archipelago and the Western Pacific. -In the Malay Archipelago, the geo- graphically equivalent area of the Indonesian Tertiary, 14 species groups and 79 species are represented. More than half the species (62%) are wide-ranging in the Indo-Pacific (Table 3); 30% are Indo-West Pacific species or shared with the western Pacific or the Indian Ocean. Only two species are currently recognized as endemic to the archipelago. Erosaria, Erronea, and Purpuradusta are the dominant species groups (Table 4), and Blasicrura is virtually restricted to the Malay Archipelago and the western Pacific. Species composition in the western Pacific is like that in the Malay Archipelago (Tables 3, 4) but there are more species and a substantial endemic element. The western Pacific cowries are distinguished primarily by the endemic species group Nesiocypraea with six species from deep water of the South China Sea and near the New Hebrides. In other species groups with western Pacific endemics, five species are endemic to Japan, and four species are endemic to the New Caledonian- New Hebrides-Solomon Islands section. Central Pacific- - In the central Pacific 87 species are recorded, of which 36% are endemic. Erosaria, Lyncina and Purpuradusta are the dominant species groups; neither Blasicrura nor Nesiocypraea is found on the Pacific Plate. From west to east, species numbers decline, wide-ranging Indo-west Pacific species are replaced by central Pacific endemics, and species composition changes.

Table 4. Distribution of species groups with five or more species as a percentage of the cowrie assemblage

Malay Arch. Western Pacific Central Pacific Indian Ocean Species group (%) (%J ('!OJ (%J

Erosaria 21 19 26 25 Erronea 19 16 8 II Purpuradusta 13 13 II 10 Mauritia 8 6 7 9 Lyncina 8 8 13 10 Pustularia 6 6 7 4 Blasicrura 6 5 o I Nesiocypraea o 7 o o Bistolida 5 4 7 6 Cribrarula I 2 6 2 Talostolida I I 6 I 30 BULLETIN OF MARINE SCIENCE, VOL. 47, NO. I, 1990

90 80 Indo

.:::~:~'. ~ 65 .•0...... Fojl

~ 60 0'" ._••_••••~~.

o Gum ••.••.•.•• Ene ~ 55 .•••.•...~ .•

E 50 .•.• ~ .•...... ~ 30 45 • Soulh 01 Equlltor • ~.•••• •. 20

40 a Norlh 01 Equator Sam ••••••.•~

Haw"o 35 . Figure 2 (left). Numbers of cowrie species from west to east across the Pacific. Ene, Enewetak; Fij, Fiji; Gum, Guam; Haw, Hawaii; Indo, Indonesia; NG, New Guinea; akin, Okinawa; Sam, Samoa; Tah, French Polynesia. Figure 3 (right). The distribution of Indo-Pacific and Central Pacific species across the Pacific. Abbreviations as in Figure 2.

That species richness decreases west to east across the Pacific is well documented (Ekman, 1953; Kay, 1980; 1984). Among the cowries, the number of species decreases both above and below the equator (Fig. 2). The distribution of species groups shows a similar although less marked decline (from 16 in the west to 11- 13 in the east). The proportion ofIndo- Pacific species increases both above and below the equator betwe:en Indonesia and Guam and Samoa (Fig. 3), and then declines at the periphery (Hawaii and southeast Polynesia). Concomitant with the drop in Indo-Pacific species is a rise in the number of species endemic to the central Pacific: in Hawaii and southeast' Polynesia, more than one-third of the assemblages are central PacifIc species. Species composition changes among the islands of the Pacific (Fig. 4A): species of Lyncina and Erosaria make up a greater proportion of the assemblages in Hawaii and southeast Polynesia than they do elsewhere, and species of Erronea and Purpuradusta lesser proportions of the assemblages. The increase in dominance of Erosaria and Lyncina is the result of the numbers of endemic species in these species groups: 9 of the 15 species groups have endemic species, but more than 50% of the endemism occurs in Erosaria and Lyncina (Table 5). Two foci of endemism in the central Pacific have been identified (Kay, 1984), in Hawaii and in southeast Polynesia (Table 5). Springer (1982) distin- guishes three types of endemism which can be recognized among the central Pacific cowries: some are widely distributed, others are limited to a few islands or groups of islands, and a third group includes single island endemics (Table 5). Many of the central Pacific endemics can be traced to a widespread Indo-Pacific species. Erosaria granulata and E. cassiaui, for example, endemic to the Hawaiian Islands and Easter Island, respectively, are anatomically and conchologically related to the widespread E. nucleus, and Cribrarula gaskoini of the Hawaiian Islands is obviously related to C. cribraria which has an Indo-Pacific distribution. Some cowries with a primarily central Pacific distribution encroach in the western Pacific. Mauritia maculifera is recorded from Okinawa, and Lyncina ventriculus has been found at Cocos Keeling in the Indian Ocean, although it is not recorded in intervening areas. Indian Ocean.-In the Indian Ocean, cowrie diversity is rather more uniform than in the Pacific, but there is a steep diversity gradient at the southern margin (the southern Mascarenes) (Stehli, 1968; Taylor, 1971). In keeping with Taylor's (1971) note that for the molluscan fauna as a whole, continental shorelines and KAY: BIOGEOGRAPHY OF INDO-PACIFIC CVPRAEIDAE 31

45 • EAOSAAIA

• LVNCINA 40 0 EROSARIA a LYNCINA 35

HlIW'

Figure 4 4A (left). The distribution of the Erosaria and Lyncina species groups from west to east across the Pacific (abbreviations as in Figure 2). 4B (right). The distribution of the Erronea and Purpuradusta species groups from west to east across the Pacific. Abbreviations as in Figure 2.

continental islands tend to have larger faunas than do smaller islands in the Indian Ocean, more cowrie species are reported from the continental margins and islands (an average of 41 species from East Africa to the Gulf of Aden) than from the oceanic islands (an average of 33 species). The Indian Ocean endemics also occur around continental margins and islands: all 23 endemic cowries are reported from continental margins or are associated with continental islands. Species composition in the Indian Ocean is rather like that of the central Pacific: Erosaria, Erronea, Lyncina and Purpuradusta are the dominant species groups, Nesiocypraea is absent, and only one species of Blasicrura is reported. Forty-two percent of the endemic species are in Erosaria and Lyncina.

Table 5. Endemism in the Cypraeidae in the Central Pacific (' widespread on the Pacific Plate; 2 restricted to a few islands; J single island endemics)

Species group Hawailan Islands Southeast Polynesia Central Pacific Bistolida goodalli' summersi' Cribrarula gaskoinP astaryP bernardP cumingP Erosaria granulata2 caputdraconisJ irrorata' semiplota2 cassiaui3 ostergaardP dillwyni2 englerti3 kingae2 obvelata2 thomasP Luria tessel/ata2 Lyncina sulcidentata2 bouteti2 aurantium' leviathan' propinqua' schilderorum' ventriculus' Mauritia maculifera' Purpuradusta serrubfera2 Pustularia mauiensis2 Talostolida alisonae2 subteres2 burgessi' rashleighana2 32 BULLETIN OF MARINE SCIENCE, VOL. 47, NO.1, 1990

DISCUSSION The cowries of the Indonesian Tertiary clearly bear the legacy of their Tethyan ancestry, a relationship recognized in Shuto's (1976) suggested Middle Miocene biogeographic province in which three subprovinces are differentiated: Burma- Pakistan, Malaya-Philippines-Indonesia, and Taiwan-Japan. The absence of a Lower Miocene molluscan facies (Te) in Indonesia is awkward in that the story of the connection between the eastern Tethys and Indonesia is incomplete. Ifspecies numbers can be taken as indication ofa period of speciation, however, then four species groups, Barycypraea, Erosaria, Erronea, and Miolyn- dna, with from 4 to 10 species in the Indonesian Middle Miocene, must have speciated fairly extensively during that earlier time. The geographic pattern of the fossil record must of necessity reflect the occurrence of Cenozoic facies in the Pacific. Despite the limitations of the fossil record, it is clear that associations with Fiji, Guam, the Marshall Islands and Okinawa in the Pacific, and a tie with Australia, were in place by the Middle Miocene. The contemporaneous occurrences of species groups and species in these areas and Indonesia are evidence for a biogeographical province and speciation extending beyond the geographical boundaries of Indonesia. Both the fossil and Recent history of the Indo-Pacific cowries is one of increasing morphological, ecological and spatial diversification. Jablonski's (1979) model of speciation in the Order Neogastropoda during the Middle and Late Cretaceous in which it "reached present diversity by extensive, rapid origination at low taxonomic levels with gradual accumulation of new families, rather than the ... early appearance of higher categories comprising only a few low-level taxa" has been extended by Kohn 1(1985) to include the family Conidae during the Tertiary and Quaternary. The fossil history of the Cypraeidae also fits that model. The distribution of the cowries today is not random: the dominance of some species groups in some areas, their absence in others, and the concentration of central Pacific and Indian Ocean endemics at the periphery of those regions, are indicative of the play of ecological, developmental and historical factors in de- termining the picture we see today. The patterns of spatial distribution in the fossil record and of endemism in Recent time indicate speciation beyond the boundaries of the Malay Archipelago and provide support for Ladd's (1960) hypothesis that Pacific islands "could have been the home of many elements of the Indo-Pacific fauna."

ACKNOWLEDGMENTS

The advice, help and patience ofthe many curators and technicians in the molluscan collections in which I have worked are most gratefully acknowledged. I am particularly indebted to Dr. de Groot and Dr. P. Gaemart, Rijksmuseum fur Geologie, Leiden; Professor E. Gittenberger of the Rijksmuseum van Naturlijke Historie, Leiden, Dr. H. Coomans, Museum fur Zoologie, Universitet Amsterdam; C. P. Nuttall and R. Cleevelly of the Department of Paleontology, British Museum (Natural History), London; and to Dr. P. Morda.n, Dr. 1. D. Taylor, and Ms. K. Way of the Mollusca Section, British Museum (Natural History), London. I also thank P. Kilham for help with the illustrations.

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DATEACCEPTED: January 18, 1989.

ADDRESS: Department of Zoology, University of Hawaii, 2538 The Mall, Honolulu, Hawaii 96822.