J. Paleont., 84(3), 2010, pp. 000–000 Copyright ’ 2010, The Paleontological Society 0022-3360/10/0000-0000$03.00

RUDISTS OF TIBET AND THE TARIM BASIN, CHINA: SIGNIFICANCE TO REQUIENIIDAE PHYLOGENY

ROBERT W. SCOTT,1 XIAQIAO WAN,2 JINGENG SHA,3 AND SHI-XUAN WEN3 1Department of Geosciences, University of Tulsa, Tulsa, Oklahoma 74104, ,[email protected].; 2China University of Geosciences, Beijing, China; and 3LPS, Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences, Nanjing

ABSTRACT—Rudists are a principal biotic component of Cretaceous carbonates in Tibet and in the Western Tarim Basin. Barremian to Maastrichtian carbonate units are widespread on the northern margin of the Indian Plate and in Tethyan tectonic slices that were welded onto Eurasia in successive stages during the Late Cretaceous and Paleogene. In far northwestern Tibet, Barremian-Cenomanian endemic rudists and cosmopolitan orbitolinid foraminifera occupied isolated carbonate platforms in the eastern Tethys. Rudists, corals, and stromatoporoids composed bioherms up to 10 m thick and several kilometers in lateral extent. A unique endemic requieniid rudist, Rutonia, is compared to morphologically similar but older, less derived genera. Associated specimens in this assemblage are indeterminate requieniid valves, monopleurids, and two genera with three radiolitid species that are re-described and taxonomic positions re-evaluated. In southern Tibet, mainly endemic Campanian-Maastrichtian radiolitid rudists and cosmopolitan larger benthic foraminifera contributed to carbonate shelves on the northern Indian Plate near the Cretaceous equator. In the Western Tarim Basin Cenomanian strata yield Tethyan rudist species. Coiling morphometric analysis using the three-dimensional morphology Raup diagram shows that Requieniidae valves in contact with the substrate are convergent with the basic gastropod shell. More derived strongly coiled, younger requieniids were adapted to encrusting or semi-infaunal habits. Stratigraphic analysis confirms that Requieniidae diversity crises coincided with Cretaceous oceanic anoxic events Two end members of valve geometry each appear to be primitive and derived characters respectively and separate the family Requieniidae into two clades that are here recognized as two new subfamilies. The end members are defined by the coiling geometry, whether the spire is close to the plane of commissure or it is translated along the coiling axis and by myophore structures. The older matheroniform clade has a low spirogyrate LV that is translated slightly from the commissure along the coiling axis; this group is composed of Matheronia (and its subgenus Monnieria), Hypelasma, Lovetchenia, Rutonia, and Kugleria. Genera in the younger clade have a tall trochospiral LV that is translated along the coiling axis and consists of Requienia, Toucasia, Pseudotoucasia, Apricardia, Bayleoidea, and Bayleia. Claditics support these relationships.

INTRODUCTION Mesorbitolina texana (Roemer, 1849) (senior synonym of

RETACEOUS CARBONATE shelves and platforms in the Tethys Orbitolina kurdica Henson, 1948, according to Simmons et al., C Realm were populated by marine benthic communities 2000) and Mesorbitolina pervia (Douglas, 1960) together with dominated by unconventional rudist bivalves, scleractinia, and Praeradiolites hedini Douville´ (1917), Sphaerulites [formerly various types of larger benthic foraminifera (Masse et al., Praeradiolites] biconvexus (Yang et al., 1982), and Praeradio- 1995). Rudist distribution and species composition are rather lites ngariensis Yang et al. (1982). The Cenomanian Gamba- well known in the western part of the Tethys Realm of North cunkou Formation yields Mesorbitolina aperta (Erman, 1854), Africa, southern Europe, Turkey, and the Middle East Orbitolina concava (Lamarck, 1816), and Conicorbitolina (Steuber and Lo¨ser, 2000). However, rudists in the eastern conica (D’Archiac, 1837) with the rudists Praeradiolites hedini part of southern Asia are poorly known. In Tibet/Xizang, and Rutonia bangonghuensis Yang et al. (1982), and mono- pleurids. Six additional rudist species were created by Gou and Cretaceous carbonates are quite thick and widespread and Shi (1998): list them. rudists are a principal biotic component. The Chinese The objectives of this contribution are to demonstrate the geosciences community has described many rudist species geological importance of Tibetan rudists and to synthesize (Qian, 1993; Gou and Shi, 1998; Wen, 1999; Wen et al., 2000). their distribution, biostratigraphy, paleoecology, and phylo- Douville´ (1916) first reported Upper Cretaceous rudists genetic considerations. A modern description of the locally from southern Tibet collected during a 1903 British expedition known requieniid genus, Rutonia, prompts a morphological (Fig. 1). The Campanian assemblage consisted of Bournonia analysis and a cladistic hypothesis of the rudist Family haydeni Douville´ (1916) and Bournonia tibetica Douville´ Requieniidae that suggests the Family Requieniidae be divided (1916) associated with Biradiolites. The Maastrichtian rudist into two subfamilies. This paper follows phylogenetic research is Plagioptychus tibeticus Douville´ (1916) with the larger of Upper Jurassic and Lower Cretaceous species by Masse benthic foraminifers Orbitoides, Lepidorbitoides and Ompha- (1994, 2002) and Gourrat et al. (2003). locyclus. These assemblages are part of the Campanian- Maastrichtian Zongshan Formation (Willems et al., 1996). MATERIAL Albian and Cenomanian rudists and orbitolinid foraminif- Large collections of rudists and other megafossils as well as era are significant components of thick carbonate units in far samples for microfossil thin sections were collected during the northwestern Tibet in the Ngari, Xizang area (Fig. 1) (Wan et 1980 expedition. These materials were distributed between the al., 2003). The Albian Lanshang Formation is from 1,000 to University Museum at China University of Geosciences 3,000 m thick (Fig. 2) and is dated by the foraminifers Beijing and the Paleontological Institute in Nanjing. Speci- 0

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FIGURE 1—Major sedimentary terranes of the Tibetan-Qinghai-Xizang Plateau in present-day position. Legend: 1(marine shelf facies, 2) deep sea facies, and 3) continental facies (from Wen, 1999). The key rudist localities are 1) Ngari region (Yang et al., 1982): type area of Radiolites bangonghuensis, Praeradiolites biconvexus, and Praeradiolites ngariensis; and 2) Zongshan area with villages of Kampa Dzong and Tuna, (N28u to 28u209 by W88u309 to 89u159) (Douville´, 1916): type area of Bournonia haydeni and Bournonia tibetica, and Plagioptychus tibeticus. mens collected by later expeditions are at the Chengdu and extends for many kilometers across the Ngari region in Institute of Technology. western Tibet (Fig. 1, site 1). In places rudist-coral bioherms Dr. Zetong Nie (personal commun., 2007), who, with Dr. up to 10 m thick and several tens of meters wide are encased in Xiaqiao Wan, participated in the geological expedition to marl. Rudists and corals dominate the bioherms and algae are Tibet, reviewed for us the rudist occurrences. The rudist- accessory biota. At the bioherm margins orbitolinids are bearing Langshan Formation carbonate is up to 1,000 m thick common and are intermixed with rudist talus debris. Overlying the buildups at the base of the marl, orbitolinids and intraclasts of the rudist-coral bioherm are abundant and diminish up section (Yang et al., 1982, fig. 2).

BIOGEOGRAPHY OF TIBETAN RUDISTS The Tibetan Plateau today is a complex tectonic province composed of several terranes or blocks sandwiched between the Indian Plate to the south and the Eurasian Plate on the north (Fig. 3) (Huang and Chen, 1987; Qian, 1993; Li and Xiao, 1995; Wang et al., 1997; Gou and Shi, 1998; Wen, 1999; Wen et al., 2000; Sha et al., 2002; Wan et al., 2003; Sha et al., 2004). North of the Indian Plate in northwestern Tibet the Lhasa Block is bounded by the Yarlung-Zangbo and the Bangong-Nu River suture zones (Fig. 1). Albian-Cenomanian carbonates with rudists (Yang et al., 1982) are located at the northwest end of the Lhasa Block in the Ngari district (Fig. 1, site 1). During the middle Cretaceous this tectonic slice was positioned between approximately 10u and 20u north latitudes (Fig. 3; Golonka, 2002). A second tectonic slice, the Qiang- tang block, lies north of the Lhasa Block and south of the Eurasian Plate. This latter block hosts Cretaceous carbonates FIGURE 2—Generalized stratigraphic classification of rudist-bearing in the Karakorum and Kunlun mountains and the Tarim formations in Tibet (modified from Wen, 1999; Wang et al. 2002). Basin along its southern margin (Wen, 1999). The Qiangtang

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rudists are known from this subprovince; however, the Tithonian megalodontid, Protodiceras lanonglaensis Li and Grant-Mackie (1994), occurs west of Mount Everest/Qomo- langma in the Nyalam district at the base of the Xuomo Formation. By Campanian-Maastrichtian times the Indian Plate had moved into the tropical zone and bivalves including rudists were part of the Tethyan Eastern Mediterranean Subprovince (Gou and Shi, 1998; Wen, 1999). Common rudists were endemic species of Biradiolites, Bournonia, Lapeirousia, Plagioptychus, and Praeradiolites (Appendix 1). North of the Yarlung-Zangbo suture zone on the Lhasa Block, bivalve assemblages include Tethyan and eastern Asian types of the Eastern Mediterranean Subprovince (Wen, 1999). In the Gandes forearc basin, a possible Eoradiolites is reported from the Aptian-Albian Sangzugang Formation, which is equivalent to the Langshan and Maryo formations. Rudist genera in the Albian-Cenomanian Langshan Formation include Monopleura, Praeradiolites, Requienia, Rutonia, and FIGURE 3—Plate tectonic sketch map during the latest Cretaceous to Toucasia; two of these fourteen species are cosmopolitan earliest Paleogene time, c. 81–58 Ma (modified from Golonka, 2002, fig. 34 and Masse and Gallo Maresca, 1997, fig. 5). Black ovals indicate Ngari (Appendix 1). Farther northwest in the Karakorum Belt of the and Zongshan areas of Fig. 1. Dashed lines–ocean spreading center and Qiantang Block, Early Cretaceous rudist species are endemic transform faults; dash-dot lines–subduction zones; solid lines–approxi- and two of five Late Cretaceous species are endemic. Upper mate modern plate boundaries. Cretaceous Turonian rudists in the lower part of the Tielongtan Group are Biradiolites, Durania, Praeradiolites, block docked with the Eurasian Plate in latest Jurassic and the Sauvagesia, and Vaccinites (including its junior synonym Lhasa block docked with Qiangtang and Eurasia in the middle Rhedensia) (Gou and Shi, 1998; Wen, 1999). The younger Cretaceous (Wan et al., 2003). Santonian-Maastrichtian assemblage in the Tielongtan in- On the northern Indian Plate, Cretaceous marine sedimen- cludes Distefanella, Lapeirousia, and Hippurites (Appendix 1). tary rocks comprise two belts, the shallow water Southern On the Eurasian Block in the Tarim Basin and in the West Tethys Himalaya and the deep water Northern Tethys Kunlun Belt, the Cenomanian-Turonian Kukebai Formation Himalaya belts (Wen, 1999). Shallow-water Aptian-Albian hosts the cosmopolitan species of Ichthyosarcolites among bivalves of the Southern Tethys Himalaya formed an endemic other Tethyan bivalves. Farther west in Tadzhikistan and center as the Indian Plate moved northward (Masse et al., Uzbekistan this genus occurs with Caprinula soluni Bobkova 1995; Wen, 2000). During the Campanian-Maastrichtian the in the middle Cenomanian section (Pojarkova, 1984). Late northern margin of the Indian Plate was a mixed carbonate- Cretaceous rudists in the Tielongtan Group and Yigeziya siliciclastic shelf when the Zongshan Formation with its rudist Formation of the West Kunlun Belt are Biradiolites, paleocommunities was deposited (Fig. 3) (Willems et al., 1996; Gyropleura, Lapeirousella, Osculigera, and Sauvagesia, how- Wang et al., 2001; Wan et al., 2002). In late Cretaceous the ever the majority of species appear to be endemic (Appendix 1) Indian Plate was south of the equator in the tropical zone and (Gou and Shi, 1998; Wen, 1999). in Paleogene time it docked with the Lhasa Block (Wen, 2000; Wan et al., 2002; Wang et al., 2002; Sha et al., 2004). STRATIGRAPHIC DISTRIBUTION OF REQUIENIIDAE Based on an analysis of total Cretaceous Bivalvia assem- Species of the Family Requieniidae first appear in the latest blages, northern India together with eastern Arabia and Kimmeridgian Age and went extinct in the Maastrichtian Age northeastern Africa were part of the North Indian Subpro- (Fig. 4). Although this family did not diversify during the vince (Kauffman, 1973). In contrast, Tibetan bivalve assem- Cretaceous Period to the extent that other rudist groups did, it blages of the Lhasa Block shared species with assemblages in was a persistent component of shallow water carbonate shelf Turkey and comprise the Eastern Mediterranean Subprovince. communities. As did other rudist groups, Requieniidae These two subprovinces together with the Western Mediter- experienced multiple extinctions during or soon after some ranean Subprovince comprise the Indo-Mediterranean Region Cretaceous oceanic anoxic events (Masse and Philip, 1986; of the Tethyan Realm (Kauffman, 1973). Comparison of the Ross and Skelton, 1993; Masse, 1994, 2002; Scott, 1995). The Late Aptian-Albian radiolitids, however, shows that a oldest requieniid species, Hypelasma salevensis (Favre in Mediterranean assemblage differed in species composition Joukowsky and Favre, 1913) evolved from diceratids, such from the Southwestern Asian assemblage (Masse and Gallo as Epidiceras or Plesiodiceras, during the latest Kimmeridgian Maresca, 1997). The Southwestern Asian assemblage popu- in southern France (Skelton, 1999; Gourrat et al., 2003). lated distinct tectonic blocks of Iran, Afganistan, northern Matheronia appeared in the Tithonian and diversified in the Pakistan, and northwestern Tibet. This rudist data suggests Early Valanginian but suffered extinction during the mid- that Kauffman’s Eastern Mediterranean Subprovince may be Valanginian crisis (Masse, 2002). During the Hauterivian, composed of two distinct assemblages that were partly members of the family became cosmopolitan and diversified geographically isolated. This issue may be addressed by more into the Barremian and Early Aptian, when the family was detailed collections from these areas. composed of four genera. Two genera went extinct following Early Cretaceous bivalve assemblages of the northern the early Aptian OAE1a and two survived. The family Indian Plate and Himalayan belts consist of Gondwana diversified again during the Albian and Cenomanian, but species similar to those in Australia, Antarctica, East Africa, only one genus survived the latest Cenomanian–earliest and South America. These assemblages comprise the Himal- Turonian OAE2. Following this stressful even,t the family yan Subprovince or endemic center (Wen, 1999, 2000). No was represented by two genera that continued into the

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FIGURE 4—Stratigraphic ranges of requieniid genera and inferred evolutionary branching.

Campanian-Maastrichtian it (Fig. 4). Requieniid species phores are rounded swellings on the shell wall and the diversity and abundance apparently dwindled through the posterior myophores are platforms. This form was epifaunal, Maastrichtian and the family did not survive the Cretaceous resting on is anterior margin. The requieniform morphotype is extinction. characterized by a slowly expanding valve with a tightly coiled spire that is translated along the coiling axis and by relatively REQUIENIIDAE SHELL GEOMETRY symmetrical anterior and posterior margins. The myophores Shell geometry is genetically programmed for adaptation to are either subequal or the posterior is larger. This form was specific substrate relationships (Raup, 1966) as has been semi-infaunal with its spire inserted into the sediment. The demonstrated for rudists (Skelton, 1991; Masse, 1994, 2002). toucasiform morphotype has a rapidly expanding valve with a Raup (1966) has shown that shell geometry can be defined by moderate spiral and with a flattened anterior margin; the valve four parameters: 1) shape of the generating curve, which is is greatly compressed anteriorly-posteriorly and is keeled; the mapped by the commissure outline; 2) the rate at which the posterior myophore is the larger. This form was attached to whorl expands during growth; 3) the shift of the commissure the substrate at least in its early growth (Masse, 2002, 2009). away from the coiling axis; and 4) the rate at which the whorl The different coiling geometries of these three morphotypes is displaced along the coiling axis. These parameters were can be defined by the translation along the coiling axis (T), the measured on caprinids and aid in their taxonomic discrimi- whorl expansion rate (W), and the increasing distance of the nation and testing of evolutionary hypotheses (Scott and commissure from the coiling axis (D) (Raup, 1966; Raup and Weaver, 2008; Scott and Weaver, in press). Stanley, 1971) (Fig. 5). These parameters were estimated by The Requieniidae are divided into three morphologic measuring selected specimens (Appendix 2) and by comparing groups by the coiling and expansion rate of the LV-AV and typical specimens of the genera with the diagrams of Raup RV-FV and by the inferred orientation to the substrate: (1966) and Raup and Stanley (1971). The matheroniform matheroniform, requieniform and toucasiform (Masse, 1994, morphotype is characterized by Matheronia munieri Paquier 2002). The matheroniform morphotype includes elongate from Barremian limestone in southern France (in Douville´, inflated valves that expand in diameter rapidly from the 1918, Pl. 1, figs. 8, 9). The LV is coiled approximately one protoconch, have a low trochospiral form, and have an whorl and translation along the axis is low (T , 1). The whorl anterior margin is somewhat flattened; the anterior myo- expansion rate is low (W , 10) and the commissure is

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FIGURE 5—Three-dimensional morphospace of mollusk shell geometry (Raup and Stanley, 1972). Requieniidae morphology compares to that of Gastropoda.

displaced only slightly along the axis (D , 0.1–0.2) (Fig. 5, marine habitats. For example, in Austria Heterodiceras shells MfLV). This morphotype is homeomorphic with many are part of Tithonian subtidal deposits offshore of gravelly exogyrid bivalves. beach deposits (Sanders et al., 2007). These shells have been The requieniform morphotype is characterized by Requienia disturbed by periodic high-energy events and other tapho- ammonia (Goldfuss) from Barremian limestone in southern nomic processes. France (in Douville´, 1918, Pl. 1, figs. 6a, 6b; Masse, 1988b, Pl. 1, figs. 1–3). The LV is coiled up to three turns and translated PHYLOGENETIC SPECULATIONS ON REQUIENIIDAE (T) moderately. The whorl expansion rate is low (W , 10) and The Order Hippuritoida Newell (1965) is a clade character- the displacement is slightly greater than the matheroniform ized by a two-layer shell wall, the outer of which is composed (Fig. 5, RfLV). The toucasiform morphotype is represented by of fibrous prismatic calcite and the inner originally of several species because the shell form is variable. The aragonite (Skelton, 1978; Skelton and Masse, 2000; Skelton trochospiral LV has up to three clockwise turns and the low and Smith, 2000). Dentition consists of two teeth in the RV trochospiral RV is about two counterclockwise whorls. The and one in the LV. Species have two subequal adductor tall spired form (Fig. 5, TfLV1) is represented by Toucasia muscles either on the shell wall or on specialized plates. The patagiata (White, 1884) from the Middle-Upper Albian Hippuritoid clade is divided into two monophyletic clades Edwards Formation in Texas and the low spired form based on which valve is on the substrate. Members of the (Fig. 5, TfLV2) is represented by Toucasia hancockensis Superfamily Requienioidae Douville´ (1914) are attached to the Whitney (1952) in Garcı´a-Barrera (1995, Pl. 1, figs. 3, 6) from substrate by the LV-AV and the family is composed of Lower Albian limestones in southwest Mexico and Texas. The epidiceratids including Epidiceras, Heterodiceras, and Plesio- requieniform and toucasiform morphotypes are homeomor- diceras and the monophyletic Family Requieniidae Douville´ phic with the typical gastropod form as noted earlier by (1914) (Skelton, 1978, 1999, 2008; Masse, 1994, 2002). Younge (1967, p. 87). However, shell coiling served very However, Malchus (1995) suggested that Requieniidae are different functions in these groups. The requieniid coiling paraphyletic because he believed that the genera do not share a enabled the bivalve to fix itself in the substrate, in contrast to derived character. All other rudists comprise the Superfamily mobile gastropods in which the coiled valve encased the soft Hippuritoidea Gray (1847), which has the RV-AV on the parts and positioned them above the large foot. substrate (Skelton, 1978, 2008; Skelton and Masse, 2000). The diceratids, including Diceras, Heterodiceras, Epidiceras, Plesiomorphic characters shared by the epidiceratids and Plesiodiceras, and Eodiceras, have two inflated, torted requieniids are: 1) external ligament in a groove, 2) spirogyrate prosogyrous valves. The geometry of both valves is similar shell, 3) two teeth in RV and one tooth in LV, 4) subequal to the geometry of the Matheronia LV, except that the coiling muscle structures, and 5) shell composed of a prismatic outer axis of diceratids is at a larger angle to the commissure plane calcite layer and an inner aragonitic layer (Skelton, 1978, 1999; than in requieniids (Gourrat et al., 2003). Thus to derive Masse, 2002). Autapomorphic characters are: 1) highly requieniids from epidiceratids, the inflation of the RV was inequivalved with smaller RV, 2) LV trochospiral to reduced and coiling increased slightly. Requieniids evolved helicospiral, 3) coiling axis at small angle to commissural from diceratids and expanded into offshore, mainly shallow, plane so umbo crosses commissure plane, 4) LV anterior a flat

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surface clinging to substrate (Gourrat et al., 2003). Because of these shared characters the Family Requieniidae would seem

11. to be monophyletic. The Family Requieniidae is composed of twelve genera and Ligament subgenera (Dechaseaux and Perkins, 1969) and two subse- quently created by Yang et al. (1982) and Masse (1988a). Eleven valve characters make up the data matrix used by cladistic anaylsis (Table 1; Appendix 3). Some genera are 10. LV Dentition described less thoroughly than others so that the matrix is rather small. To test these phylogenetic hypotheses the Phylogenetic Analysis Using Parsmony-PAUP 4.0 Beta software was run (Swofford, 2002) assuming Heterodiceras as the ‘outgroup’ genus. Two consensus trees show similar

Dentition groups of taxa (Fig. 6A, B). The ‘‘strict consensus tree’’

9. RV Posterior (Fig. 6A) is a very conservative estimate of consensus that separates two generic groups (Swofford, 2002; Forey, 2009). The ‘‘majority-rule concensus tree’’ (Fig. 6B) results in similar generic groups although they are rooted at higher levels than

cavities the strict consensus tree. These groups are found in more than

8. Accessory half of the rival trees. In both trees Apricardia, Requienia, Toucasia, and Pseudotoucasia are closely grouped and Bayleia and Bayleoidea are in the next closest branch. Bayleoidea, however, requires a thorough re-examination to consider the origin of the accessory cavity (J.-P. Masse, 2010, personal bands

7. Siphonal communication). A second group is more loosely allied; Lovetchenia, Hypelasma, Matheronia, and Monnieria are separated from Kugleria and Rutonia. The suggested evolutionary relationships and the basic

6. RV character states delineate two requieniid clades (Fig. 6C).

Myophore Shared primitive character sets of the Requieniidae are 1) inequivalved shell in which the LV-AV is larger and more torted than the RV-FV; 2) distinct growth rings; finer growth lines develop in younger genera and radial striae with fine 5. LV growth lines are on three genera; 3) RV-FV dentition is Myophore composed of a larger posterior and a smaller anterior tooth; 3) the posterior muscle attachment is larger than the anterior and attached to various projecting posterior myophore structures;

4. LV and 4) two-layered wall structure of outer calcite and inner Ornament aragonite (Skelton, 1978; Masse, 2002). The LV-AV of species of the Requieniidae is prosogyrate coiled clockwise when viewed from the exterior and is much larger than the RV (Skelton and Smith, 2000; Gourrat et al., 2003). This coiling Form direction is opposite to the opisthogyrate counter-clockwise 3. RV Shell LV-AV of oysters such as Exogyra, which has been noted by many rudist specialists (see Malchus, 1995). Two end members of valve geometry each appear to be

Form characterized by primitive and derived characters respectively

2. LV Shell and separate the Requieniidae into two clades (Fig. 6C). The end members are defined by the coiling geometry, whether the spire is close to the plane of commissure or it is translated 100100 0100000 0 0100100 0 0100100 0 0 0 00 0 0 00 0 00 0 00 122301 0132311 0 1122300 0 1 1 10 1222?1 0 ? 0 10 122200 0 0 0 10 122200 1 0 ? ?0111200 1 0 0 10 111210 0 2 0 10 1212?0 0 0 0 10 111100 0 0 0 10 111110 0 0 1 ?0 1112?0 0 0 0 10 0 0 10 0 ?0 along the coiling axis. The older matheroniform clade has a structure 1. Micro- low spirogyrate LV that is translated slightly from the commissure along the coiling axis; this group is composed of Matheronia (and its subgenus Monnieria), Hypelasma, Love- tchenia, Rutonia, and Kugleria. Genera in the younger clade have a tall trochospiral LV that is translated along the coiling axis and consists of Requienia, Toucasia, Pseudotoucasia, Apricardia, Bayleoidea, and Bayleia. The requieniform LV of Requienia is translated more greatly than the toucasiform LV. The geometry of the RV also separates the two clades. In the matheroniform clade the RV is slightly inflated and is coiled —Requieniid morphologic characters used in cladistic analysis. See Appendix 2 for character descriptions. 1 with little translation, whereas in the younger clade of Genera requieniform and toucasiform groups the RV is flat to convex Diceras Heterodiceras Epidiceras Plesiodiceras ABLE Apricardia Requienia Toucasia Pseudotoucasia Baleyia Bayleoidea Lovetchenia Hypelasma Kugleria Matheronia Monnieria Rutonia Outgroup T with little or no coiling translation. Growth rings are

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FIGURE 6—Cladograms of Requieniid genera based on A) strict concensus and B) majority rule. C) Cladogram of Requiienidae genera showing evolutionary relations. Valve cross sections for Bayleia and Bayleoidea based on Palmer (1928, Figs. 4, 5 and Pl. 6 Fig. 2). Cross sections of myophores of Lovetchenia, Matheronia, Requienia, Toucasia, and Pseudotoucasia from Masse (2002, fig. 1).

suppressed in younger genera and radial striae appear late in the diceratids such as Epidiceras and Plesiodiceras.An the phylogeny. apomorphic character is the RV posterior myophore of Within the matheroniform clade, Lovetchenia is distin- Pseudotoucasia, which is a plate mounted on a buttress guished by its inflated RV and myophores on extensions from separate from the cardinal area. the valve margins. Rutonia has a greatly inflated RV and wider The posterior myophore on the LV is of two types: 1) a myophores. Kugleria has a greatly extend posterior tooth on narrow ledge or plate extending from the valve wall and its RV (Fig. 6C). This succession is consistent with the known separate from cardinal plate, or 2) an impression directly on stratigraphic order (Fig. 4). valve surface as in Hypelasma, Monnieria, and Requienia. Another character that differentiates these two groups is the Radial bands are wide shallow depressions expressed as form of the posterior myophore of the RV. The older state in subtle curves in the growth lines on the posterior margin of the all genera except Requienia, Pseudotoucasia, and Apricardia is LV in Toucasia and Requienia. Radial bands are not an extension of the cardinal platform along the posterior valve recognized in other requieniid genera or in diceratids. margin as in Kugleria (Masse et al., 1998), whereas the Accessory cavities are present in two genera and define a younger state has the posterior myophore on a separate plate separate subgroup. Bayleia has a cavity below the ligament projecting from the valve wall. In both clades, the anterior groove and two on either end of the posterior myophore of the myophore structures of both valves are elongate flat surfaces RV (Palmer, 1928, figs. 4, 5). Bayleoidea has a cavity between on the inner anterior wall similar to the shallow muscle scar the RV posterior myophore and valve wall (Palmer, 1928, pl. pits of many bivalves. On the RV the primitive posterior and 6, fig. 2); however, this feature may be diagenetic (Masse, anterior myophore structures are similar to the myophores of 2010, personal communication).

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Dentition of the RV is composed of two cardinal teeth, the from the valve wall. The anterior muscles were attached to the posterior of which is taller than the anterior one and the LV valve interior wall. Bayleoidea and Bayleia differ from has one smaller tooth. In most genera the large posterior tooth Toucasia mainly by the presence of one and three posterior of the RV is arcuate, but in Apricardia and Kugleria it is a cavities respectively and by the absence of fine radial striae curved cone. In Bayleoidea the teeth are subequal knobs. and radial bands. The ligament is a primitive character of both clades and is situated in a curved groove external to the dentition and on SYSTEMATIC PALEONTOLOGY the posterior margin as it is in the diceratids. Order HIPPURITOIDEA Newell, 1965 The Tibetan Albian-Cenomanian Rutonia appears to be Superfamily REQUIENIOIDAE Douville´, 1914 similar to older requieniid types and illustrates iterative Family REQUIENIIDAE Douville´, 1914 evolution. Its morphology is similar to morphologies of Late This family includes the genera Requienia Matheron 1843, Jurassic-earliest Cretaceous diceratids and the Hauterivian- Apricardia Gue´ranger 1853, Matheronia Munier-Chalmas early Aptian requieniid, Lovetchenia. Both morphotypes have 1873 (including the subgenus Monnieria Paquier, 1898), prosogyrally coiled subequal, inflated valves. The LV was Toucasia Munier-Chalmas 1873, Bayleia Munier-Chalmas attached or inserted into the soft substrate. The RV is coiled in 1873, Hypelasma Paquier, 1898, Pseudotoucasia Douville´ a plane with little translation along the coiling axis. Two 1911, Bayleoidea Palmer 1928, Kugleria Bouman 1938, phylogenetic hypotheses on the origin of Rutonia must be Rutonia Yang, Nie, Wu, and Liang 1982, and Lovetchenia tested. First, that it descended from Lovetchenia, although no Masse 1988a. Most species in these genera are strongly late Aptian to early Albian species has yet been found. Masse inequivalved, generally the LV umbo intersects the commis- (2002) proposed that Lovetchenia evolved from Matheronia by sure plane, and the outer shell layer is thick. The larger expanding the myophore plates on both valves and inflating prosogyrate left valve (LV) lay upon the substrate as the the RV. The myophore plates of Rutonia are similar in form attached valve (AV); the smaller right valve (RV) is the upper, and structure to those of Lovetchenia. However the coiling free valve (FV). Most genera are simply ornamented by faint planes of both valves of Lovetchenia are close to the growth lines or winkles; radial striae rare. The external commissure plane, whereas in Rutonia the spire of the LV is ligament is a shallow arcuate groove dorsal to the cardinal slightly displaced along the coiling axis and the valve is slightly platform. Dentition in LV-AV is a single small central tooth trochospiral. This hypothesis is consistent with a monophy- and in RV-FV two unequal teeth, the posterior tooth generally letic subfamily Matheroniinae new subfamily herein. is the larger of the two. Anterior muscle insertion in LV-AV is An alternative hypothesis is that Rutonia evolved from one on shell wall and in RV-FV it is on the wall or on an extension of the late Albian species of Requienia, Toucasia,or of cardinal platform. The posterior muscle insertion in the LV- Pseduotoucasia. The valves of Requienia are quite asymmetric, AV is on the shell wall or a myophore plate. The posterior the RV-FV being flat operculiform so that the genus is an muscle insertion in the RV-FV is on a myophore plate unlikely ancestor. Toucasia, however, is a candidate ancestor extending either from the shell wall at a right angle or from the that ranges from Barremian to Cenomanian and both valves cardinal platform (Malchus, 1998; Masse et al., 1998; Gourrat of some species are trochospirally coiled like Rutonia. et al., 2003). Radial bands are weakly developed on posterior However the posterior myophore on the FV of Rutonia is an side of LV-AV of some species. extension of the cardinal platform and in Toucasia it is a The Requieniidae evolved from diceratids, possibly Plesio- separate plate extending from the valve wall. Also the large diceras muensteri (Goldfuss, 1840) in the latest Kimmeridgian posterior tooth on the RV-FV of Rutonia is positioned more and diversified moderately during the Cretaceous as did other posteriorly than it is on Toucasia. This hypothesis implies that rudist families; the family was extinct by the end of the Matheroniinae is polyphyletic. Cretaceous (Fig. 4) (Gourrat et al., 2003; Masse, 1994; In the more derived clade of requieniforms and toucasi- Skelton, 1978, 1985, 1991). Requiieniid species were locally forms, the RV of Toucasia and others is flat to opercular and abundant as frictional or attached clingers (Skelton, 1991) in the RV posterior myophore is Y-shaped (Fig. 6C). In caprinid buildups and in shelf biostromes (Scott, 1981). Pseudotoucasia the RV posterior myophore has migrated from the valve margin to an inner position. Bayleoidea has a Subfamily REQUIENIINAE Douville´, 1914 new subfamily single cavity between the wall and the myophore plate that Type genus.—Requienia Matheron, 1843 (nominotypical may not be a primary feature. In Apricardia the posterior taxon). myophore is a plate below and separate from the cardinal Diagnosis.—LV requieniform or toucasiform, tall trochos- shelf, and its posterior tooth is enlarged (Mainelli, 1995). pire translated along the coiling axis; RV flat to convex with Finally Bayleia has developed three small cavities along its little or no coiling translation; the LV myophores are inflated posterior shell margin of the RV. The high spirogyrate areas on the shell wall or projecting plates; the RV posterior Requienia was derived from Hypelasma by the development myophore plate is separate from the cardinal platform; RV of the posterior myophore plate on the RV. Toucasia and posterior tooth reduced in size in some genera. Growth rings Pseudotoucasia then descended from Requienia by the addition are suppressed; some genera with radial bands; some with of a keeled LV and a posterior myophore plate in the LV. radial striae; some with accessory canals. The subfamily Palmer (1928, p. 37) suggested that Toucasia was the includes the genera Requienia, Toucasia, Pseudotoucasia, ancestor of Bayleia, which evolved to Bayleoidea. However Apricardia, Bayleoidea, and Bayleia. Bayleoidea is older than Bayleia and cannot be the descendent species. These three genera have very similar external forms in Subfamily MATHERONIINAE new subfamily which the larger LV-AV is spirogyrate, with coiling displaced Type genus.—Matheronia Munier-Chalmas, 1873. slightly along the coiling axis; its posterior margin is flattened. Diagnosis.—LV matheroniform, low spirogyre translated The much smaller RV-FV is opercular. All three have small slightly from the commissure along coiling axis; RV slightly teeth in both valves. The posterior myophore structure on inflated, coiled with little translation along axis; the LV both valves of each species is a thin plate jutting interiorly myophores are expanded plates on the valve wall; on the RV

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the posterior myophore plate extends from the cardinal RUTONIA BANGONGHUENSIS Yang, Nie, Wu, and Liang, 1982 platform; RV posterior tooth a large arcuate ridge. The Figure 7.1–7.11 subfamily includes Matheronia (and its subgenus Monnieria), Rutonia bangonghuensis YANG,NIE,WU, AND LIANG, 1982, Hypelasma, Lovetchenia, Rutonia, and Kugleria. pl. 2, figs. 2, 3, 6a, 6b, 7a, 7b. Genus LOVETCHENIA Masse, 1988a Type specimens.—Holotype 80A003 LV, location of spec- Type species.—Requienia lovcensis Zlatarski, 1886, p. 312, imen unknown; paratypes 80A058, RV, 80A051, 80A060(052) pl. 3. deposited in the University Museum, China University of Matheronia lovetchensis (Zlatarski); PAQUIER, 1903, p. 25, pl. Geosciences, Beijing. II, fig. 3; pl. III, figs. 1–3. Diagnosis.—Monospecific genus. Original Description (translation).—Shell large, inequi- Lovetchenia lovetchensis (Zlatarski); MASSE, 1988a; 1993; 2002. valved; LV fixed, coiled, conical to turbinate, curved, changing greatly in shape. Valve height greater than 100 mm, diameter Diagnosis.—Lovetchenia has a very convex RV-FV that is of the valve up to 70mm. The early growth stage is gently distinctly spiral in the plane of commissure. Both myophores coiled and later becomes straight. RV nearly planispiral, of the RV-FV are interior platforms subparallel with the coiling for one turn into low, conical shape, cap-like, and has commissure plane and extend from the cardinal platform. On obvious grooves. The RV has two teeth; the anterior one is the LV-AV the posterior myophore is a narrow platform about half the size of the posterior one; the posterior tooth is a circumscribed by a distinct bourrelet (Masse, 2002). high, protruding, curved arc; the two teeth are parallel and Discussion.—Lovetchenia is found in Hauterivian to lower extend dorsally, separated by a deep triangular pit that reflects Aptian carbonate strata along the northern margin of the the tooth of the LV; but the teeth of the LV are not preserved. Mediterranean Sea (Masse, 1988a). The shell is thick and the body cavity is shallow (translation). Genus RUTONIA Yang, Nie, Wu, and Liang, 1982 Description.—LV-AV moderate size, thick, prosogyrate clockwise up to 360u, deeply inflated, beak rounded elongate, Type species.—Rutonia bangonghuensis Yang, Nie, Wu, and expanding slowly into adult valve. Internal features not Liang, 1982, p. 297. observed. RV-FV moderate size, thick, prosogyrate counter- Diagnosis.—Both valves very convex, inflated; beak of LV- clockwise up to 180u, deeply inflated, beak broadly rounded, AV displaced along coiling axis away from commissure plane. oriented posteriorly; commissure outline ovate, slightly extended Dentition of RV-FV consists of two teeth, a small, knob-like postero-ventrally at postero-ventral corner; commissure margin anterior tooth and tall arcuate posterior tooth along the deeply folded into a trough; umbo greatly arched, posterior flank postero-dorsal margin. Posterior muscle of RV-FV inserted on steeper than anterior; valve surface with faint concentric growth wide plate extending ventrally from cardinal platform. Other rings. External ligament groove originates beneath beak and myophores are unknown. Ligament groove narrow along extends posteriorly in a broad arch to end of tooth. Two teeth, postero-dorsal margin. anterior tooth conical, posterior tooth tall, thick, long, curved Original Description (translated).—Character: large inequi- from below beak to posterior margin, surface smooth. Myophore valved shell. Left valve spirally twisted for several whorls; surfaces gently arched wide, smooth. Measurements of specimen right valve (RV-FV) is free, coiled once, operculate. The right 80A051: height 7.5 cm, length 6.1 cm, width 4.0 cm; specimen valve has two teeth, the anterior one smaller and the posterior 80A060(052): height 6.3 cm, length 4.8 cm, width 3.4 cm. one larger, the anterior tooth only half as long as posterior Discussion.—Rutonia has internal structures that are similar tooth; both separated by a socket. The LV-AV has no to Lovetchenia. The myophores of the RV-FV are wide preserved teeth. The anterior adductor scar in the RV-FV is platforms attached to the valve inner wall as in Lovetchenia. anterior to the anterior tooth and the posterior muscle scar is The dentition and ligament groove of the RV-FV are also like on the hinge plate posterior to the tooth. The ventral margin that of Lovetchenia. Other features are not yet known. Rutonia of the right valve is broadly concave, thick shelled with a small and Lovetchenia differ from Matheronia, which has a flat cap- body cavity. shaped RV-FV and on the LV-AV the beak is close to the Original Discussion.—We place this new genus in Requie- commissure. The LV-AV of Rutonia differs from that of niidae because of three main characters: (1) the LV is fixed, the Lovetchenia;inRutonia the beak of the LV-AV is displaced RV is free; (2) the LV is strongly coiled and the RV is cap- along the coiling axis from the commissure plane, whereas in shaped; and (3) the RV has two large teeth, the anterior is Lovetchenia the beak coils in the commissure plane. The coiling small and the posterior is large. The FV-LV is cone-shaped, of the LV-AV is closer to that of Toucasia and Pseudotoucasia. turbinate, the FV-RV is low cone-shaped and curved; the Distribution.—Rutonia bangonghuensis is known only from posterior tooth of the RV is much larger and arched than the the Ngari district of northwestern Tibet between the Yarlung- anterior tooth; the RV has grooves, which differs from other Zangbo and the Bangon-Nu River suture zones. It is interbedded Requieniidae genera (translation). in the Langshan Formation with Upper Albian-Lower Cen- Discussion.—Rutonia differs from Lovetchenia by its some- omanian orbitolinids: Orbitolina aperta (Erman) (late Albian- what smaller posterior myophore plate on the RV-FV and by early Cenomanian), Orbitolina concava (Lamarck), (early its more inflated RV-FV. Rutonia differs from Matheronia by Cenomanian), Orbitolina conica (D’Archiac) (early-middle Cen- its more inflated RV-FV, by its longer posterior tooth and by omanian), and Orbitolina concava var. qatarica Henson (early its longer posterior myophore on the RV-FV. The LV-AV of Cenomanian) (Yang et al., 1982; Wan et al., 2003). Monnieria is more elongate and keeled than that of Rutonia. The LV-AV of Rutonia is tightly coiled with moderate INDETERMINATE REQUIENIID VALVES translation along the axis and serves to support the animal Figure 8.6–8.10 in the soft substrate. The RV-FV of Rutonia is weakly coiled Specimens.—Specimen 80A54 and specimen 80A59 depos- with slight translation. Both valves are inflated indicating that ited in the University Museum, China University of Geosci- soft parts were distributed in both valves. ences, Beijing.

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FIGURE 7—Rutonia bangonghuensis Yang, Nie, Wu, & Liang, 1982: 1–5, specimen 80A051, RV-FV, 30.75, exterior, interior, posterior, anterior, and ventral views; 6–10, specimen 80A060 (049-9), RV-FV, 31.0, ventral, anterior, exterior, interior, and dorsal views; 11, specimen 80A003, holotype, LV- AV, 30.5, dorsal view from Yang et al. with coiling axis added (1982, pl. 2, fig. 2). Specimen catalog numbers in Figures 7–9 refer to the University Museum at China University of Geosciences Beijing.

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FIGURE 8—1–5, Monopleura sp., 1, 2, specimen 80A67; 3–5, specimen 80A56; 6–10, Indeterminate Requieniid right valves sp.; 6–7, interior and exterior views of specimen 80A54; 8–10, exterior, interior and lateral views of specimen 80A59 showing the knob and sulcus. Bar 5 1 cm.

Description.—Two oval flat valves appear to be opercular Superfamily HIPPURITOIDEA Gray, 1848 RV of indeterminate requieniids. Specimen 80A54 (Figs. 6.6, (nom. transl. Newell, 1965, ex Hippuritidae Gray, 1848) 6.7) is a moderate gray, circular, disk-shaped, concavo-convex Family MONOPLEURIDAE Munier-Chalmas, 1873 valve about 3 by 4 cm in diameter and 2 cm thick. The exterior MONOPLEURA Matheron, 1843 surface has fine growth rings and is spirally coiled counter- clockwise in a prosogyral manner. The center is a circular Type species.—Monopleura varians Matheron, 1843; subse- depression. The interior surface consists of a central spirally quent designation by Kutassy, 1934. coiled knob surrounded by a flat outer ring that bears a thin MONOPLEURA sp. circular line similar to a pallial line. Figure 8.1–8.5 Specimen 80A59 (Figs. 6.8–6.10) is a moderate dark gray, ovate disk-shaped valve about 4.5 by 5 cm in diameter and Toucasia sp. YANG,NIE,WU, AND LIANG, 1982, p. 297, fig. 3, 2.5 cm thick. The valve outline has two straight sides that meet Pl. 2, fig. 1. at a rounded right angle; the other margins are arcuate. One Specimens.—80A56, 80A67, University Museum, China corner is indented and partly enclosed by a raised ring. On the University of Geosciences Beijing. interior side, this ring extends as a circular ridge with a small Description.—The two small, conical specimens are com- central depression. On the exterior surface, this circular knob posed of light gray calcareous shell material typical of is bordered by a sulcus. The interior surface also bears a thin monopleurids rather than the dark brown calcite of the circular line similar to a pallial line. requieniid shell. The conical valves are spirally twisted as are Distribution.—These specimens were collected from the many monopleurid specimens, and they are ornamented by upper part of the Langshan Formation with Rutonia faint concentric growth rings that indicate a conical form and other rudists in the Ngari district of northwestern rather than the spirally coiled requieniids. One specimen is a Tibet. cluster of one or two attached to a larger individual.

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Distribution.—The specimens were collected in the Rutog Type specimens.—Praeradiolites gilgitensis types are at area with the other rudists in the Langshan Formation Ecole des Mines, Lyon; types of Praeradiolites ngariensis (33u289250N, 79u359250E) (Yang et al., 1982). 80A007, 80A008, are at University Museum, China University of Geosciences Beijing. Family RADIOLITIDAE d’Orbigny, 1848 Diagnosis.—RV/AV subcyclindrical to ovate, tall, orna- Genus PRAERADIOLITES Douville´, 1902 mented by evenly spaced, narrow costae, each divided by thin Type species.—Radiolites fleuriaui d’Orbigny, 1842 shallow striae; body cavity ovate; ligament ridge changes Key generic characters are: 1) ligament ridge, 2) folded or towards commissure from planar to bulbous; radial bands wavy growth rings on posterior margin, 3) two ventral radial wide and slightly expressed. bands, Ab and Pb, with convex up growth laminae separated Original Description of P. ngarensis.—Shell cylindrical- by an interband band, Ib, expressed by concave up growth conical, with outer shell layer composed of closely spaced lamellae, and 4) outer calcite shell layer with rectangular cells funnel plates, which are longitudinally folded and furrowed; and polygonal cells in radial bands (Douville´, 1902; Floquet, ligament ridge typically bulb-shaped in cross section. The 1998; Masse et al., 2007). inner layer is about 1–3 mm thick. In transverse section [of the RV-AV] there is one tooth and two sockets. E and S bands are PRAERADIOLITES HEDINI Douville´, 1916 indistinct on the outer shell (translation). Praeradiolites hedini DOUVILLE´ , 1916, p. 147, pl. 11, fig. 2–6; Description of P. ngarensis.—RV-AV subcyclindrical, tall KU¨ HN, 1932, p. 126; SA´ NCHEZ, 1981, p. 151; YANG et al., gradually expanding cone, ornamented by evenly spaced, 1982, p. 299, pl.1, figs.1, 5a–c, text-fig. 5; MASSE AND narrow costae, each divided by thin shallow striae. Internal GALLO MARESCA, 1997, p.102, 107; STEUBER, 2000, p. 161. valve cross section ovate, longer dimension either dorsal- Praeradiolites cf. hedini DOUVILLE´ , 1916; DOUVILLE´ , 1926b, ventral or anterior-posterior; outer wall dark gray, composed p. 353, text-fig. 8. of radial and concentric laminae, one to two times thicker than Eoradiolites hedini (DOUVILLE´ , 1916); YANIN, 1989, p. 15; inner spar wall. Ligament ridge a wide plate extending from outer wall layer with a bulbous tip. Central tooth on RV-AV a MASSE ET AL., 2007, p. 706 narrow, curved spar plate projecting posteriorly at about a 45u Type specimens.—Ecole des Mine, Lyon. angle to dorsal margin. RV-AV myophore is a narrow plate. Diagnosis.—Tall slightly tapering RV/AV ornamented by LV-FV cardinal platform a wide horseshoe-shaped plate, longitudinal rounded costae; ligament ridge is planar with a anterior and posterior myophore plates wide ovate, embayed tee-shaped to Y-shaped tip; Ab and Pb bands broadly rounded around ligament; distally the anterior bar fades into triangular separated by a shallow fold. anterior tooth; posterior tongue-shaped tooth extends from Description.—The RV/AV is elongate, cylindrical to slightly myophore plate inserted between central tooth of RV-AV and conical, up to 12–15 cm tall and 4–5 cm in diameter; the ligament ridge; myophore plate has hollow spaces in thickest transverse section is elliptical; the concentric growth lamellae part. The ventral exterior margin is eroded so that the Ab and of the outer calcite wall are inclined about 30 degrees to the Pb bands cannot be seen. long axis of the RV and 15–20 mm apart; the outer shell is Discussion.—Based on known structures of these two ornamented by rounded longitudinal costae up to 5 mm wide; species, it is reasonable to place them in synonomy in the the inner aragonite shell layer is thin dorsally and laterally, genus Eoradiolites. Praeradiolites gilgitensis clearly possess the thickening at the ventral Ab and Pb bands. The anterior band anterior and posterior bands (Douville´, 1926b, figs. 7, 8) is a higher amplitude fold than the posterior band; they are characteristic of Eoradiolites as described by Masse et al. separated by a broad shallow fold. The ligament ridge is (2007). These bands parallel the valve length and deflect the narrow, flat dorsally and expands interiorly in a tee- or Y- exterior growth lamellae slightly; in transverse cross sections shape. The LV/FV is unknown. the concentric lamellae are folded outwards. The microstruc- Discussion.—The planar tee-shaped or Y-shaped ligament ture of the outer shell wall is composed of concentric lamellae ridge and the low rounded longitudinal costae differentiate P. with polygonal cells (Pusdey et al., 1985) in contrast to the hedini from other species. quadrangular cells of Eoradiolites davidsoni. However Masse Distribution.—This species ranges from the Albian through et al. (2007) included both microstructures in Eoradiolites. The the Cenomanian and is a member of the Southwest Asian outer shell wall of Praeradiolites ngariensis is like that of E. fauna (Masse and Gallo Maresca, 1997) in northwestern India gilgitensis. The radial bands of Praeradiolites ngariensis are and Tibet in the region around Rutog in the Langshan incompletely preserved but suggest the out-folded character Formation. (Figs. 9.1–9.3) described by Masse et al. (2007). So the latter species is tentatively assigned to the genus Eoradiolites. It can Genus EORADIOLITES be considered to be a junior synonym of E. gilgitenesis based Type species.—Eoradiolites davidsoni Adkins, 1928, on the right valve outline, the configuration of the myocar- dinal structure, and the ornament. Eoradiolites gilgitensis (DOUVILLE´ , 1926b) Figure 9.1–9.3 Masse et al., 2007 suggested that Praeradiolites griegsbachi be assigned to the genus Eoradiolites based on the flat Praeradiolites gilgitensis DOUVILLE´ , 1926b, p. 353, pl. 13, figs. posterior band. Eoradiolites griegsbachi is close to E. 4a, 4b, text-figs. 7, 8; PUDSEY ET AL., 1985, p. 160–161, fig. gilgitensis in its broadly rounded outline (Douville´, 1926a) 5. and occurrence in Himalayan Cretaceous strata (Masse and Eoradiolites gilgitensis DOUVILLE´ in MATHUR AND VOGEL, Gallo Maresca, 1997). The large myocardinal structures of 1988, p. 698–699, pl. 1, figs. 1–5, pl. 2, figs., 1–5, pl. 3, figs. these three sets of specimens are similar to each other and to E. 1–3; provides previous synonomy; MASSE AND GALLO davidsoni, taking into account that the transverse sections of MARESCA, 1997a, p. 102; STEUBER, 2000, p. 81. each appear to be at different distances below the commissure Praeradiolites ngariensis YANG,NIE,WU, AND LIANG, 1982, plane. The ligament ridge of the three Asian taxa projects into p. 299, pl. 1, figs. 2, 3; PUDSEY ET AL., 1985, p. 161. the body cavity and expands towards the commissure as a

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FIGURE 9—Radiolitidae. 1–3, Praeradiolites ngariensis Yan, Nie, Wu, & Liang, 1982: 1, paratype 80A008, view into RV-AV, cut is at a 40–50u angle to growth axis; 2, anterior margin of 80A008 RV-AV; 3, holotype 80A007, view into RV-AV, cut is at a 3–40u angle to growth axis. 4–7, Sphaerulites biconvexus Yang, Nie, Wu, & Liang, 1982, holotype 80A048: 4, view into RV-AV; 5, interpretation of interior structures of RV-AV (Yang et al., 1982, fig. 6); 6, lateral view of dorsal margin; 7, lateral view of ventral margin; L 5 ligament, Eb 5 exhalent band, am and pm 5 anterior and posterior myophores, Sb 5 radial band, 1, 3 5 teeth of RV, 2 5 tooth of LV. Bar 5 1 cm.

Journal of Paleontology pleo-84-03-04.3d 31/3/10 16:49:25 13 Cust # 09-137 0 JOURNAL OF PALEONTOLOGY, V. 84, NO. 3, 2010 bulb. The ligament of E. ngariensis is composed of dark Type specimen.—80A048, University Museum, China Uni- compact outer shell material and not a secondary deposit as versity of Geosciences Beijing. suggested by Pudsey et al. (1985; Mathur and Vogel, 1988). Diagnosis.—RV-AV low subconical, wider than high, However the ligament ridge of E. davidsoni is short and external prismatic shell layer very wide, flaring; ligament long, narrow. narrow; no accessory cavities. Radial bands broadly rounded. The cardinal tooth of the RV-AV of P. gilgitensis is long, Original Description (translation).—Shell large (diameter of narrow and hooked; that of ngariensis is also long and narrow body cavity greater than 55 mm), the outer shell layer extends and slightly curved, and that of griesbachi is short and narrow. 45 mm; total length of the specimen is 55 mm, shell sub- The anterior myophores of the RV of all three species are biconvex. The outer shell layer of the FV is about 45 mm broad v-shaped extensions of the inner shell layer. The thick, marked by closely spaced funnel plates (intersection posterior myophores of gilgitensis and ngariensis are short angle about 80u between outer and inner shell layers); lamellae rounded projections from the inner valve wall; greigsbachi close to inner layer inclined and become subhorizontal appears to have no such projection. outwards. The specimen has two major growth rings each The myocardinal structures of the LV-FV of gilgitensis, about 3 mm thick. Ligament ridge narrow, about 8.5 mm long; ngariensis, and griesgbachi are large arcuate to horseshoe- appearing to join with cardinal tooth, and inserted between shaped plates that project into the RV similar to that of E. two teeth of FV. Muscle insertion plates broad. davidsoni (Masse et al., 2007, fig. 3A2). The anterior teeth of Description.—RV/AV low, very wide, anterior-posterior gilgitensis and ngariensis are large, ovate and the posterior dimension 14.5 cm, dorsal-ventral dimension 8.0 cm; convex teeth are rounded. The anterior tooth of griegsbachi is v- base, commissure surface gently convex; mantle margins very shaped and the posterior tooth is rectangular and bifid. The wide from 1.5 to 7.0 cm, thick outer prismatic shell layer. Body LV myophores of ngariensis are larger than those of cavity excentrically ovate, anterior-posterior dimension longer gilgitentsis and are perforated by large cavities; this could be than dorsal-ventral, 6.0 cm by 5.0 cm; anterior margin evenly a function of the position of the transverse cuts. curved, antero-ventral margin straight merging into shallow The four new radiolitid species created by Gou and Shi sulcus of E radial band, postero-ventral corner narrow, (1998) possess radial bands like those of Eoradiolites and are abrupt, posterior margin straight and inclined posteriorly, distinguished by features of the ligament ridge and ornament. dorsal margin broadly curved. Outer wall layer with radial and Praeradiolites gegyainensis Gou and Shi (1998) has a flattened concentric prisms, wide anteriorly, extremely extended poste- ligament ridge and a thicker inner shell layer than E. riorly; inner spar layer very thin. Ligament ridge a thin plate ngariensis. Praeradiolites daxungensis Gou and Shi (1998) 0.85 cm long extending from invagination of interior margin has a short, quadrate ligament ridge. The ligament ridge of of outer wall layer, radial bands are gentle swellings on inner Praeradiolites bangoinensis Gou and Shi (1998) is described as sparry wall layer. Anterior myophore is kidney-shaped shelf ‘‘…distinct, strong, short (about 5 mm in length), and wedge on the inner wall. Teeth of RV-AV and LV-FV are ovate with shaped.’’ Praeradiolites perbellus Gou and Shi (1998) has a long direction dorsal-anterior direction. very thin ligament ridge. Praeradiolites coquenensis Gou and Discussion.—The morphology of this species meets all the Shi (1998) has a very short, wide ligament ridge. Serial sections characteristics of the genus Sphaerulites. The RV-AV of through successive ontogenetic stages are needed to under- Sphaerulites Lamarck (1819) is flattened and wider than high; stand the growth stages of these shells. These species may be it is characterized by highly foliaceous growth lamellae, junior synonyms of E. gilgitensis. For example the tip of the ventral bands expressed as undulations or subtle folds in the ligament ridge of Praeradiolites ciryi Floquet (1991) varies growth lamellae and internally as embayments in the valve considerably from rounded to blunt to bifurcate depending on margin, ligament ridge well developed in older forms; LV-FV its preservation (Floquet, 1998). convex, rarely planar; cardinal apparatus similar to that of Distribution.—The type locality of E. gilgitensis is near Praeradiolites (Toucas, 1907; Dechaseaux and Coogan, 1969). Gilgit in the Yasin area of northwestern Pakistan (Douville´, Sphaerulites biconvexus differs from Sphaerulites cantabricus 1926b, gave these coordinates: 73u209E and 36u209N; Douville´ (1889), the Albian species of northern Iberia, by its locality S2(iii) of Pudsey et al., 1985). The upper Aptian- wider anterior-posterior expansion of the outer prismatic layer lower Albian age of the Gilgit, Yasin outcrop is constrained and by the absence of accessory cavities. S. biconvexus also by Orbitolina (Mesorbitolina) texana (Roemer) (Pudsey differs from the French Cenomanian Sphaerulites foliaceus et al., 1985). The type locality of E. ngariensis is near Lameila, Lamarck (1819) by its thinner inner shell layer, narrow Ritu County in the Albian Langshan Formation with O. ligament, and by the absence of accessory cavities on either texana, Orbitolina (Mesorbitolina) pervia, Praeradiolites side of the ligament. hedini, and Sphaerulites biconvexus. The five Praeradiolites Distribution.—Type locality is in Jiagang, Ritu County and species of Gou and Shi (1998) range throughout the Langshan was collected from the Albian Langshan Formation with Formation. Mesorbitolina texana, Mesorbitolina pervia, Praeradiolites hedini, and Praeradiolites ngariensis. The type locality of S. griesbachi is near Herat, Afganistan (Douville´, 1926a) and is not well constrained by age-diagnostic CONCLUSIONS fossils. Rudists are a principal biotic component of Cretaceous Genus SPHAERULITES Lamarck, 1819 carbonates in Tibet and in the Western Tarim Basin. Barremian to Maastrichtian carbonate units are widespread Type speciesSphaerulites foliaceus Lamarck, 1819. on the northern margin of the Indian Plate and in Tethyan tectonic slices. In northwestern Tibet, Barremian-Cenomanian SPHAERULITES BICONVEXUS (Yang, Nie, Wu, and Liang, 1982) endemic rudists, corals, stromatoporoids, and cosmopolitan Figure 9.4–9.7 orbitolinid foraminifera built bioherms on carbonate plat- Praeradiolites biconvexus YANG,NIE,WU, AND LIANG, 1982, forms in the eastern Tethys. The endemic Requieniid rudist p. 299, Pl. 1, figs. 4a–c. Rutonia is compared to morphologically similar but older, less

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derived genera. Associated specimens in this assemblage are D’ARCHIAC, E. J. A. 1837. Memoire sur la formacion cretace du sud-ouest monopleurids and two genera with three radiolitid species that de la France. Socie´te´ge´ologique de France, Memoire No. 2(7):157–193. DECHASEAUX,C.AND A. H. COOGAN. 1969. Family Radiolitidae Gray, are re-described and taxonomic positions re-evaluated. In 1848, p. N803–N817. In L. R. Cox et al.. (eds.), Treatise on Invertebrate southern Tibet Campanian-Maastrichtian mainly endemic Paleontology. Pt. N. Mollusca 6. Bivalvia, Vol. 2. Geological Society of radiolitid rudists and cosmopolitan larger benthic foraminif- American and University of Kansas Press, Lawrence. era contributed to carbonate shelves on the northern Indian DECHASEAUX,C.AND B. F. PERKINS. 1969. Family Requieniidae Douville´, 1914, p. N779–N781. In L. R. Cox et al.. (eds.), Treatise on Plate near the Cretaceous equator. In the Western Tarim Invertebrate Paleontology. Pt. N. Mollusca 6. Bivalvia, Vol. 2. Basin Cenomanian strata yield Tethyan rudist species. Geological Society of American and University of Kansas Press, Three-dimensional morphometric analysis shows that Re- Lawrence. quieniidae valves are convergent with the basic gastropod DES MOULINS, C. 1826. Essai sur les Sphe´rulites qui existent dans les shell. More derived strongly coiled, younger requieniids were collections de MM. F. Jouannet, membre de l’Acade´mie royal des Sciences, belle Lettres et Arts de Bordeaux, et Charles Des Moulins. adapted to encrusting or semi-infaunal habits. Stratigraphic Bulletin d’Histoire naturelle de la Socie´te´ Linne´enne de Bordeaux, analysis confirms that Requieniidae diversity crises coincided 1:148–303. with Cretaceous oceanic anoxic events DOUGLASS, R. C. 1960. The foraminiferal genus Orbitolina in North Two end members of valve geometry and internal mor- America. U.S. Geological Survey Professional Paper 333, 52 p. DOUVILLE´ , H. 1889. Sur quelques rudistes du terrain cre´tace´ infe´rieur des phology appear to be primitive and derived characters Pyre´ne´es. Bulletin de la Socie´te´ge´ologique de France, Se´ries 3, 17:627– respectively and separate the Family Requieniidae into two 655. clades that are here recognized as two new subfamilies. The DOUVILLE´ , H. 1902. Classification des Radiolites. Bulletin de la Socie´te´ end members are defined by the coiling geometry, whether the ge´ologique de France, Se´ries 4, 2:461–477. ´ ´ spire is close to the plane of commissure or it is translated DOUVILLE´ , H. 1910. Etudes sur les rudistes de Sicile, d’Alge´ria, d’Egypt, du Liban et de la Perse. Socie´te´ge´ologique de France, Memoire No. 41, along the coiling axis and by myophore structures. The older p. 1–84. matheroniform clade has a low spirogyrate LV that is DOUVILLE´ , H. 1911. Observations sur les ostre´ide´a. Origine et classifica- translated slightly from the commissure along the coiling axis; tion. Socie´te´ge´ologique de France, Bulletin, Se´ries 4, 10:635–646. this group is composed of Matheronia (and its subgenus DOUVILLE´ , H. 1914. Les Re´quie´nide´s et leur e´volution. Bulletin de la Monnieria), Hypelasma, Lovetchenia, Rutonia, and Kugleria. Socie´te´ge´ologique de France, Se´ries 4, 14:380–383. DOUVILLE´ , H. 1916. Les calcaires a orbitolines et a Radiolites du Thibet. Genera in the younger clade have a tall trochospiral LV that is In: S. Hedin (ed.), Southern Tibet. Discoveries in former times translated along the coiling axis and consists of Requienia, compared with my own researches in 1906–1908, 5:145–147. Toucasia, Pseudotoucasia, Apricardia, Bayleoidea, and Bayleia. DOUVILLE´ , H. 1917. Les terrains cre´tace´s de l’Asie occidentale. Compte Claditics support these relationships. rendu sommaire des Se´ances de la Socie´te´ge´ologique de France, p. 121– 122. ACKNOWLEDGMENTS DOUVILLE´ , H. 1918. Le Barre´mien supe´rieur de Brouzet. Troise`me Partie: Les Rudistes. 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Journal of Paleontology pleo-84-03-04.3d 31/3/10 16:49:29 17 Cust # 09-137 0 JOURNAL OF PALEONTOLOGY, V. 84, NO. 3, 2010 Campanian- Maastrichtian tan species. Tielongtan Gp. As cf. Tielongtan Gp. Tielongtan Gp. cosmopolitan (C) species Albian- Turonian Kukebai Formation ?Turonian- Maastrichtian Tielongtan Gp. Tielongtan Gp. Tielongtan Gp. Tielongtan Gp. Albian- Turonian Langshan Fm. Langshan Fm. Langshan Fm. indet. Gp. Campanian- Maastrichtian Albian- Cenomanian Terrane Lhasa Block Qiangtang Block Eurasia Block-Tarim Basin Campanian- Himalayan Maastrichtian Cen-Turon C Alb-Turon E indet. Langshan Fm. Upper Tielongtan Gp. Tielongtan Gp. As sp. Haut-Turon C Alb-Cen E Langshan Fm. Langshan Fm. UK E Alb-Cen E Langshan Fm. Alb-Cen E Langshan Fm. Langshan Fm. Tielongtan Gp. UK C Langshan Fm. Alb-Cen E Langshan Fm. Alb-Turon E Langshan Fm. Langshan Fm. Alb-CenAlb-TuronAlb-Turon E E E Langshan Fm. Langshan Fm. Langshan Fm. Langshan Fm. Alb-Cen E Langshan Fm. Alb-Turon E Langshan Fm. Lower Tielongtan Gp. Tielongtan Gp. UK C ´ Gou Gou Des Gou Gou Yang Gou Yang (Yang Gou Gou 1987 UK E Zongshan Fm. Gou 1987 Alb-Turon E Langshan Fm. ¨ser, 2000; ranges of genera from Dechaseaux and Coogan, 1969; ranges of endemic (E) taxa from primary publications. E—endemic species; C—cosmopoli Astre 1954 UK Langshan Fm. Douville (Lapeirouse Yang 1984 Uk E Langshan Fm. Upper Tielongtan Gp. Matheron Polsak 1967 Sant-Camp C sp. Aptian Langshan Fm. Taxa Age Biogeog. sp. L-UK Zongshan Fm. Langshan Fm. Jiega Fm., sp. Langshan Fm. sp. Barrem-Apt Langshan Fm. sp. Alb-Turon Langshan Fm. Langshan Fm. sp. L-UK Jingzhushan sp. Tith-Cen sp. Barrem-Apt Langshan Fm. Jiega Fm. —Rudist taxa reported from Tibet and Tarim Basin. Data sources: Yang et al., 1982; Lan and Wei, 1995; Gou and Shi, 1998; Wen, 1999; Zhang, 2000; Ranges of sp. L-UK Langshan Fm. Langshan Fm. 1 sp. Apt-Cen Langshan Fm. Parona 1921 Gou and Shi 1998 1842 et al. 1982 Yang 1984 and Shi 1998 et al. 1982 Moulins 1826 and Shi 1998 and Shi 1998 and Shi 1998 1987 and Shi 1998 et al., 1982) 1916 1781) from Steuber and Lo Ichthyosarcolites tricarinatus Caprina Coralliochama anomalusa Monopleura Rutonia bangonghuensis Mitrocaprina xinjiangensis Eoradiolites Eoradiolites curvicornis Praeradiolites Toucasia Toucasia carinata Matheronia Pachytraga Praecaprina Amphitricoelus Agriopleura Praeradiolites coqenensis Praeradiolites bangoinensis Praeradiolites perbullus Praeradiolites daxungensis Praeradiolites cylindraceus Praeradiolites saxeus Sphaerulites biconvexus Praeradiolites exiguus Praeradiolites gegyainensis Praeradiolites gregareus Praeradiolites hedini Radiolites aliensis Radiolites angeoides Praeradiolites ngariensis Radiolites crassus PPENDIX Ichthyosarcolitidae Caprinidae Monopleuridae A Requieniidae Radiolitidae

Journal of Paleontology pleo-84-03-04.3d 31/3/10 16:49:30 18 Cust # 09-137 SCOTT ET AL.—TIBETAN AND CHINESE RUDISTS 0 Campanian- Maastrichtian Yigeziya Fm. Tielongtan Gp. Yigeziya Fm. Tielongtan Gp. Tielongtan Gp. Yigeziya Fm. Yigeziya Fm. Tielongtan Gp. Tielongtan Gp. Tielongtan Gp. Tielongtan Gp. Tielongtan Gp. Albian- Turonian Yigeziya Fm. Tielongtan Gp. Yigeziya Fm. Yigeziya Fm. Yigeziya Fm. ?Turonian- Maastrichtian sp. Lower Tielongtan Gp. Lower Tielongtan Gp. Tielongtan Gp. Tielongtan Gp. Tielongtan Gp. Tielongtan Gp. Upper Tielongtan Gp. Lower Tielongtan Gp. Albian- Turonian as sp. Langshan Fm. Tielongtan Gp. Langshan Fm. of cf. persica Gou and Shi 1998] Campanian- Maastrichtian Durania Albian- Langshan Fm.-doubtful Cenomanian Terrane Lhasa Block Qiangtang Block Eurasia Block-Tarim Basin Campanian- Himalayan Maastrichtian Camp E Langshan Fm. UK E Camp E Camp E Camp-Maas E Camp-Maas E Zongshan Fm. indet. Maast E UK C Camp E UK E UK C UK E UKAlb-Turon E C Zongshan Fm. Langshan Fm. Langshan Fm. Upper Tielongtan Gp.- Maas E Con-Sant E ´ ´ 1910 UK C ´ 1916 Camp-Maas E Zongshan Fm. Langshan Fm. Jiega Fm. Tielongtan Gp. ´ 1916 Camp-Maas E Zongshan Fm. Polsak Yang Bobkova Yang Pojarkova Yang Yang 1984 UK E Yang 1984 UK E Yang 1984 UK E Cox 1933 Camp-Maast E Reported in Des Lan and Douville Gou and Douville Douville Roemer 1852 Alb-Cen C Douville Pojarkova tibetica Taxa Age Biogeog. Bobkova 1961 cf. ? Sp. Turonian sp. UK sp. Cenomanian Langshan Fm. sp. UK Zongshan Fm. Langshan Fm. Jiega Fm. Lower Tielongtan Gp. sp. UK Langshan Fm. Upper Tielongtan Gp. Tielongtan Gp. sp. Santonian sp. UK sp. Turonian —Continued. ´ 1916 ´ 1926 1 ? Sp. UK sp. L-UK darwaseana 1955 1984 1961 1926 Douville Bobkova 1961 Douville 1955 1984 1967 1984 Moulins 1826 Shi 1998 Wei 1995 Lan and Wei 1995 Gyropleura magianensis Vaccinites Gyropleura vakhschensis Hippurites Rhedensia Himeralites Petkovicia Gyropleura vakhschensis Dictyoptychus persica Plagioptychus Radiolites kunlunensis Radiolites xinjiangensis Biradiolites Biradiolites boldjuanensis Horiopleura haydeni Biradiolites lumbricoides Milovanovicia Biradiolites minor Bournonia fourtaui Bournonia haydeni Bournonia tibetica Bournonia xinjiangensis Gorjanovicia acuticostata Medeella Distefanella Sauvagesia kunlunensis Sauvagesia texana Sauvagesia xinjiangenisis Lapeirousella qiemaganensis Durania Lapeirousia jouanneti Lapeirousia lomata Osculigera yengisarensis Osculigera oytarensis PPENDIX A Polyconitidae Hippuritidae New Family? Dictyoptychidae Plagioptychidae

Journal of Paleontology pleo-84-03-04.3d 31/3/10 16:49:33 19 Cust # 09-137 0 JOURNAL OF PALEONTOLOGY, V. 84, NO. 3, 2010 Zlatarski Gueranger Paquier, Palmer 1928, Mexico Schnarrenberger 1901, Italy 1898, France 1886, Bulgaria Munier-Chalmas 1873, France 1853, France Paquier, 1898, Italy Gras, 1854, France T. steinmanni H. colloti R. lovcensis B. clivi B. pouechi A. carinata Monnieria romani Caprotina virginiae characters Type species cavity Miscellaneous posterior accessory 3 posterior cavities primitive character Ligament groove groove groove groove groove groove groove groove groove groove external arcuate external arcuate external arcuate external arcuate arched ridge external arcuate external arcuate external arcuate external arcuate external arcuate character Diceras Myophore derived cardinal plate; anterior on wall anterior on wall anterior on wall plate; anterior on wall anterior on wall cardinal platform on wall plate extension; anterior on wall below cardinal plate below cardinal plate platform like plate; anterior on wall large extensions of cardinal posterior on cardinal character anterior small conical Dentition primitive unknownposterior large conical posterior on ledge posterior on ledge lines or striae lines or striae growth lines small posterior on plate; growth lines small knob posterior on small plate; growth lines large posterior on swelling; growth lines small posterior on plate; anterior fine growth growth lines external arcuate coarse growth lines posterior tall, coarse growth lines tooth small on myophore plate T - W - D Ornamentation Morphmetrics Shell shape keel keel trochospiral keel keel keel convex keel Toucasiform Matheroniform Matheroniform 0.5 - 10 - 0.1 Toucasiform Toucasiform Toucasiform Matheroniform Matheroniform 0.8 - 10 - 0.2 primitive character —Key morphometric characters of Requieniidae genera. 2 RV-FV opercular growth lines both small subequal posterior on extened LV-AV convex, low spiral, LV-AV convex, low spiral, LV-AVRV-FV tall spirogyrate, opercular growth lines posterior arcuate ridge posterior on cardinal RV-FV opercular, convex growth lines posterior tall arcuate plates extend from LV-AV convex low RV-FV convex, coiled growth lines posterior larger posterior on cardinal LV-AV convex, low spiral, LV-AVRV-FV convex, low spiral, conical fine growth RV-FV opercular spiral growth lines posterior tall RV-FV opercular or LV-AV low trochospiral, PPENDIX Genera A Kugleria Hypelasma Lovetchenia Bayleoidea Baleyia Apricardia Monnieria Matheronia

Journal of Paleontology pleo-84-03-04.3d 31/3/10 16:49:34 20 Cust # 09-137 SCOTT ET AL.—TIBETAN AND CHINESE RUDISTS 0 Yang, ´, 1889 Nie, Wu, Liang, 1982 Matheron, 1843, France Goldfuss, 1837, France Douville R. bangonghuensis Requienia carinata Chama ammonia Spain Toucasia santanderensis characters Type species shallow margin well developed Miscellaneous siphonal bands elevated post. 2 siphonal bands primitive character Ligament groove groove groove groove groove groove groove groove groove external arcuate external arcuate external arcuate external arcuate external arcuate external arcuate character Myophore derived plate from cardinal ledge wall plate extension; ant. on shell wall plate; anterior on wall butress cardinal platform both on shell wall external arcuate character Dentition primitive small post. on plate; ant. on radial striae long. striae growth linesgrowth lines ? posterior largergrowth lines, posterior on ? Tibet growth lines, growth lines external arcuate concentric wrinkles small arcuate both on valve wall external arcuate - 0/0 T - W - D Ornamentation Morphmetrics Shell shape trochospiral trochospiral spiral, keel spirogyrate keel keel Toucasiform 3.5/1.25 - 0/0 Matheroniform Requieniform 2.5 - 4.0 - 0.25 Toucasiform primitive character —Continued. 2 LV-AVRV-FV convex, low convex, LV-AVRV-FV convex, lo-hi arched trochospiral growth lines tall arcuate post. on cardinal LV-AVRV-FV convex, tall opercular, spiral growth lines posterior on large LV-AVRV-FV convex, low spiral, opercular, arched growth lines posterior plate on wall LV-AVRV-FV tight low spiral, opercular ? posterior large arcuate extensions of PPENDIX Genera Toucasia Rutonia Requienia Pseudotoucasia A

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APPENDIX 3 5. LV Posterior Myophore. 0, separate ledge or plate extending from REQUIENIIDAE CHARACTER STATES. valve wall; 1, impressed directly on interior valve surface. 6. RV Myophore. 0, posterior myophore plate extending from the 1. Shell Microstructure. 0, Single layer aragonite; 1, two layers-calcite & cardinal platform along the posterior valve margin; 1, posterior aragonite. myophore is a separate plate attached to and projecting from the 2. Shell Form LV. 0, subequivalved spirogyrate, moderate translation valve wall. along coiling axis; 1, inequivalved, low spirogyrate, translated slightly 7. Siphonal Bands. 0, absent; 1, wide shallow depressions expressed from the commissure along the coiling axis, matheroniform; 2, very as subtle curves in the growth lines on the posterior margin of the inequivalved, tall trochospiral, translated moderately along the LV. coiling axis, toucasiform; 3, very inequivalved, tall trochospiral, 8. Accessory Cavity. 0, none; 1, one or more associated with RV translated greatly along the coiling axis, requieniform. posterior myophore. 3. Shell Form RV. 0, inflated, strongly coiled; 1, slightly inflated and is 9. RV Posterior Tooth. 0, a large arcuate ridge; 1, curved cone; 2, small coiled with little translation; 2, flat to convex with little or no coiling subequal. translation. 10. LV Central Tooth. 0, large conical; 1, small knob-like. 4. Ornament. 0, coarse growth rings; 1, coarse growth rings and radial 11. Ligament. 0, long arcuate groove posterior to hinge plate; 1, short striae; 2, fine growth lines only; 3, fine growth lines and radial striae. small pit below beak.

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