Journal of Micropalueontolo~,~,15: 135- 149. 0262-821 X/96 $07.00 0 1996 British Micropalaeontological Society.
A review and classification of fossil didemnid ascidian spicules
OSMAN VAROLI & SIMON D. HOUGHTON' 'Varol Research, 12 Tan-y-bryn Road, Rhos-on-Sea, North Wales, LL28 4AE, UK. 'FibreCount UK Ltd, Suite 22, Dinnington Business Centre. Outgang Lane, Dinnington, Sheffield S31 7QY, UK.
ABSTRACT - 'This study discusses and classifies iossil didemnid ascidian spicules. Threc new fossil genera and nine new fossil species are described based on spicule morphology. The genera are Bonrtia gen. nov.. Rrgardia gem nov. and Monniofia gen. nov. The species are Bonetia arum sp. nov., B. hrrvis sp. nov., R. qitusitrirnc'afa sp. nov.. B. trirncatri sp. nov.. Rigairdia mulrirudiata sp. nov., R. prurcisu sp. nov., Micrascidites partciruilinfits sp. nov., Monnrofia acirforrnis sp. nov.. and M. fascicrtlata sp. nov. Recognizing these distinctive fossil didemnid spicules in tine-grained sediments should provide useful pnlaeoenvironmental information and may stimulate interest in their biostratigraphy. .I. Microprilnronfol. 15(2): 135-149, October. 1996
INTRODUCTION The class Ascidiacea, also known as sea-squirts, are Ascidians, often called sea squirts, are sessile, filter feeding sessile, mostly colonial tunicates and are common marine tunicates (subphylum Urochordata) which are important invertebrates worldwide. The sack-like zooic ranges in size members of marine benthonic communities throughout shelf from 1 to 10cm. Most (c. 95%) ascidians form colonies in seas. Living ascidians have attracted a widespread interest the shallow water of the continental shelf where they are from biologists because of their evolutionary position as attached to rocks and shells; or they are occasionally fixed in close relatives of the vertebrate (Plough, 1978). mud and sand by filaments or stalks. Colonial organization Although most ascidians are soft-bodied, some species varies within the class, but although the colony itself may secrete distinctive aragonitic spicules. Didemnid spicules are grow to a considerable size, usually the individuals forming often found in slides prepared for calcareous nannofossil it are very small (see Plough, 1978, plate VII). examination. These stellate or spherical-shaped spicules Ascidians are filter feeders and extract plankton from range in size between 10 and 70 pm and, more rarely up to water which passes through the pharynx. The water currents 125 pm. Although living didemnid ascidians are well known are drawn in through branchial slits by ciliary action. Some from the continental shelves throughout the world, fossil deep-sea ascidians obtain their food from the surrounding didemnid spicules are very rarely reported by palaeon- sediments. Other deep-sea ascidians feed on minute animals tologists and, therefore, at present are of little use as (nematodes and epibenthic crustaceans) which are caught palaeoenvironmental or biostratigraphic markers. with lobes situated around the buccal siphon. Ascidians are This study summarizes the present knowledge of ascidians hermaphroditic, each individual having male and female in relation to didemnid ascidians and fossil ascidian spicules. gonads. When the eggs are externally fertilized they hatch All type material has been deposited in the Department of into free-swimming larvae similar in appearance to tadpoles. Palaeontology, Natural History Museum. However. as the larvae mature, they usually attach themselves to some suitable object and lose their tail. SCOPE OF STUDY DIDEMNID ASCIDIANS This study is based on observations by the authors during All didemnid ascidians are sessile and colonial, they are investigations of nannofossil assemblages from worldwide common and have a global distribution ranging from the localities, ranging from Asia, the Middle East, North Africa, Arctic to the Antarctic (Plough, 1978). Most are found in Europe and the Gulf of Mexico, over a period of fifteen shallow water (0-50 m) attached to rocks. shells and other years. Additionally, the published records of ascidian spicule hard surfaces. They are rarely found in deep water, distribution have been compiled. exceptions include 1,rptoclinide.s faroensis (1500 m) and Dirlernnitrn alhiurn polare (1430 m). Didemnid ascidians are BIOLOGY AND ECOLOGY OF ASCIDIANS depth-sensitive and different species occupy well-defined Forms belonging to the subphylum Tunicata have a body areas on the sea bottom, conditioned by ocean currents and (zooid) covered by a complex tunic (from which the name water temperatures. Ascidians are usually very vulnerable to tunicate is derived) containing a substance chemically almost prolonged freshwater influences. Heavy cyclonic rainfall identical with cellulose. The tunicates consist of three regularly kills large colonies of ascidians close to the classes: the scssile Ascidiacea and the free-floating Australian coastline (P. Mather, pers. comm. in Heckel, Thalaliacea and Larvacea. Over 1300 species of Tunicata 1973). Dead ascidian bodies may float on the surface of the have been descriibed; the great majority of which belong to sea, where wind, tides and current drift may play a part in the Ascidiacea (Barnes, 1980). their distribution.
135 Varol & Houghton
DIDEMNID ASCIDIAN SPICULES also favours spicule secretion, whereas attachment to a Ascidians are soft-bodied animals and, with the exception of flexible object which allows even slight bending or spicules in didemnid and polycitorid ascidians, they are movement of the test, frequently results in secretion of rarely found as fossils. Monniot (1970) described Cystodyfes smaller types of spicules with shorter and less well-formed (Polycitorida) from Pliocene deposits of Brittany, France. rays or points. Didemnid spicules secreted in polar and Didemnid ascidians secrete fibrous spicules which, according subpolar species are frequently only sparsely distributed in to Matthews (1966), are composed of aragonite with high the surface layer of the test and are burr-like with levels of strontium (6.5%). In this study, several specimens poorly-developed spicule rays (Van Name, 1945; Kott, recovered in sediments from the Red Sea (DSDP Leg 23, 1969). Fossil didemnid ascidian spicules of varying shape Site 229A) were analysed using energy dispersive X-rays have been recorded in sediments of Jurassic to Quaternary (EDAX) to identify the strontium level. However, only age (Boekschoten, 1981). Living didemnid ascidians are traces of strontium (<1%)were observed in the spicules. classified primarily on the characteristics of the zooid; so it is The origin of the spicules remains unknown. Loewig & difficult to assign individual spicules to living species. Until Koelliker (1846), Hardman (1886), Woodland (1907) and now, therefore, Tertiary didemnid spicules which are Prenant (1925) suggested that the spicules were developed spherical in shape have been placed in Micvuscidites and independently of the zooid, whereas Michelsen (1919), PCrks those which are disc-shaped are assigned to Neanthozoites (1947) and Van Name (1952) indicated that the spicules (produced by Polycitoridae). were products of the zooid and originatcd in the lateral If a direct relationship can be established between fossil organs. In living ascidians, the spicules are surrounded by a spicules and living species, the information obtained from double-layered membrane (Lafargue & Kniprath, 1978). living forms may be applied to fossil spicules, assuming they Spicule formation is therefore not simply the result of have not changed their habitat with time, and provide useful physico-chemical processes. palaeoenvironmental information. Spicule characteristics have not been used by biologists The occurrence of recent didemnid-spicule-rich sediments for generic level taxonomy of living ascidians. Classification seems to be restricted to tropical and subtropical is based instead on a range of soft body elements (see carbonate-rich sediments. Heckel (1973) found high Elredge, 1966). However, at specific level, spicules and their concentrations of didemnid spicules (>lo% of the characteristics have been used by many authors as the nannoplankton fractions) occurred around the main primary diagnostic feature, in conjunction with characteris- carbonate reef areas of the Great Barrier Reef. Heckel tics of the zooids. concluded that the spatial distribution of the spicules in the Presence or absence of spicules, their diameter, ray sediments was controlled by selective preservation of the count, arrangement, distribution and density of rays are aragonitic spicule rays. Freshwater discharge into the basin usually considered as primary diagnostic criteria, in severely reduced the preservation potential of the spicules in conjunction with the characteristics of the zooid. However, the sediments. Berrill (1950) and Elredge (1966) treated these criteria as of When studying fossil occurrences of didemnic spicules, secondary importance or disregarded them as given species special attention must be taken to distinguish in siiu can be spicular or aspicular depending on environmental occurrences. The durability of didemnid spicules to the controls. processes of erosion, transport and deposition in warm Variations in spicule presence in ascidians could, however, waters is shown by their occurrence in turbidite deposits be the result of confusing more than one species whose adjacent to carbonate-rich shelf environments (Beall & definitions are only based on the characteristics of the zooid. Fischer, 1963: Wei, 1993). Didemnid spicules also survive In a given colony, spicules are usually identical. Van Name digestion and have been reported in fish guts (Rae, 1967) (194s) states in a discussion on Dirlemnitm cunidum that ‘I confirming fish predation and indicating another method of am far from being able to overcome the fear that I am dispersal of the spicules from their sessile habitat into soft confusing more than one species, but after the examination sediments. of a large amount material from various American localities Spicules are composed of aragonite and thus are highly I am at a loss to find a reliable basis for dividing it by susceptible to dissolution. Stieglitz (1972) recorded strongly studying museum specimens’. etched didemnid spicules from Recent sediments from the Spicule distribution and density of cover may very widely Bimini Lagoon, Bahamas. Aragonite dissolution in freshwat- not only within a given species, but also occasionally within er phreatic environments in tropical areas has also been well the same colony. Van Name (1952) suggested that variable documented (Land, 1970). The recovery of spicules in distribution and density occurs when colonies undergo a sediments therefore suggests high sedimentation rates certain amount of regression during unfavourable periods. and/or rapid sealing of sediments soon after deposition At such times the spicule remains fixed within the tunic (Houghton & Jenkins, 1988). while the zooids degenerate and are added to when new The susceptibility of ascidian spicules to dissolution and zooids develop. diagenesis may restrict their value as biostratigraphic Waters rich in carbonatc, particularly coral reef areas, are indicators. However, although ascidians are mainly benthic, especially favourable for the development of didemnid they also have a free-swimming (tadpole) larval phase. This colonies with large spicules with elongated and well-formed initial pelagic life cycle, coupled with a reported conical rays. The attachment of colonies to some rigid object cosmopolitan distribution of many species (Knott, 1969;
I36 Fossil dideninid ascidian spicules
Plough, 1970) may yet indicate that ascidian spicules have zonal markers. For example, Kokia, a possible ascidian potential interbasin correlation in well-preserved sections. spicule, has so far been documented from Valanginian to Hypersaline lagoonal and shallow water carbonate Berriasian sediments of the North Sea area. However, van platform sequences should provide fruitful starting mate- Niel (1994) suggests that Kokia specimens show a rials. Ascidian spicules are reported to be particularly construction similar to calcareous pentalith genera in the common in faecal pellets and other carbonate mud Braarudosphaeracae; but because of their high number of aggregates of the Great Bahamas Bank (Purdy, 1963). rays, Kokia should still be considered ‘incertae sedis’. Significantly, as diagenesis proceeded, only ascidian spicules Didemnum minutum seems to be restricted to the Middle were found to remain as the non-recrystallized constituents and Upper Jurassic and has a wide geographical distribution. within the pellets. Didemnid spicules also occur in carbonate High frequency variations of spicule abundance could also be muds deposited in lagoons and carbonate shoals from Belize used for local biostratigraphic correlation (cf. Heckel, 1973). (Matthews, 1966) and in the Bimini Lagoon, Bahamas Wei (1993) studied tunicate spicule abundances in (Stiegletz, 1972). sediments from the Great Barrier Reef and Queensland The stratigraphical and geographical distribution of Plateau (ODP Leg 133 sites) and concluded that tunicate ascidiari spicules for the Mesozoic and Tertiary-Quaternary spicules do not appear to be promising biostratigraphic are givm in Tables 1 to 2. The biostratigraphical potential of markers for the Pliocene-Pleistocene. However, listed didemnid spicules has still to be explored, and full below are the tentative ranges of the genera described here: stratigraphic ranges of the species are yet to be established. (a) Monniotiu recorded range Pleistocene However, a few are already known to be moderately good (b) Rigaudia recorded range Pliocene-Pleistocene
AGE 1 AUTHORS ~ AREA
Micrascidites vulgaris
Durand, 1948 & 1955 France Chauvel, 1952 France Durand & Pelhate, 1961 Quatemruy - Pliocene France Bonet & Beneviste-Velasquez, 1971 Mexico Cita, 1973 Mediterranean Houghton & Jenkins, 1988 Celtic Sea Wei, 1993 Great Banier Reef Deflandre & Deflandre-Rigaud, 1956 Australia Deflandre-Rigaud, 1968 Australia Miocene Monniot & Buge, 1971 France Heckel, 1973 Austraha Varol, 1985 Turkey Deflandre-Rigaud, 1949; 1956 & 1968 France Durand, 1952 France Eocene Deflandre & Deflandre-Rigaud, 1956 France Bouche, 1962 France Lezaud, 1966 France Rigaudia
Pleistocene I Edwards, 1973 I Coral Sea (described as Micrascidiies vulgaris) Wei, 1993 Great Banier Reef
Pleistocene - Pliocene Wei, 1993 Great Banier Reef (described as Tunicate spicules)
Monniofia
Pleistocene - Pliocene Wei, 1993 Great Banier Reef (described as Tunicate spicules) Table 1. Stratigraphical and geographical distribution of Tertiary and Quaternary ascidian spicules.
137 Varol & Houghton
SPECIES AGE AREA AUTHORS
Didemnuni minurum Callovian Britain
Didemnuni sherlundensis Valanginian North Sea Perch-Nielsen, 1988 Varol & Girgis. 1994 Camian Germany Jafar, 1983 Didemnum cusciununr Rhaetian Irian Jaya Varol & Girgis. 1994 Camian - Rhaetian Indian Ocean Bralower efal.. 1991 Didemnum pseudotrifdum Rhaetian Germany Jafar, 1983 Irian Jaya Varol & Girgis, 1994 Campanian Atlantic Cita & Gartner, 197 1 Canipanian NW Pacific Bukry, 1975 Rucinolitlrus? mugnus Campanian Turkey Varol. 1983 Canipanian - Eocene Pacific Bcrgen, 1985 I Tentative ascidian spicules
Bemasiii Pcrch-Nielsen. I9XX Kokia borealis Valanginian Valanginian-upper Ryazanian Varol & Girgis. 1994
~ ~ ~ ~ uppx Ryazanian __ Kokiu curvatu - Valanginian Kokiu sp.A upper Ryazanian Kokia sp. 1 Hauterivian Table 2. Stratigraphic and geographical distribution of MesoLoic ascidian spicules and othcr possibly related spicules.
(c) Bonnetiu recorded range Middle Miocene-Pleistocene widest in diameter along the jointed part of the rays. The (d) Micrascidiies recorded range Lower Eocene-Pleis- free part is always narrower and is conical or truncated tocene. conical. 3. Rigaudia-type rays resemble a sharpened pencil. Their MORPHOLOGY OF SPICULES free lengths are cylindrical, with parallel sides to the ray The arrangement and shape of the rays in spicules can be and a truncated peripheral end. utilized as diagnostic features for the identification of 4. Monniotia-type rays are unequal in length, composite and genera. The ratio of the length of the free part of the ray to are constructed of needle-like elements forming bundle- that of the joined part, together with the number and like structures with or without a free part. density of rays, are used for the determination of the Two major types of spicule construction have been species. The stellate spicules are assigned to the genus recognized in this study: (a) stellate spicules; (b) spherical Micrascidites and the spherical spicules assigned to the new spicules. genera Bonetia, Rigaudia and Monniotia. Stellate spicules are composite spicules constructed of Spicule rays are defined as the parts in which a spicule is several layers of petaloid units which may be flat or naturally separated or divided. Each ray therefore has two concavo-convex. In these petaloid layers each spicule ray parts: the joined part (where each ray joins to the next) and radiates from the centre of the unit. Adjacent petaloid cycles the free part. The joined inner parts of the rays are always are then joined in a saddle-like manner to form a complete conical with their apices towards the centre, whereas the spicule (Fig. 2). The number of rays is reduced towards the free parts of the rays may be conical, truncated conical or outermost cycle. Stellate spicules are found in Micrascidites. cylindrical. Spherical spicules are constructed from rays which radiate In this study, four major types of ray were identified and from the centre of the spicule and are found in Bonetia, this led to the recognition of three new gcnera (Fig. 1). Riguurlia and Monniotia. All the rays in the spicules are 1. Micruscidites-type rays are biconical or rhomboid in axial approximately the same length. section, without an inflection between the free and joined An advantage of using spicule morphology as a system of parts of the rays. classification is that individual species may be identified even 2. Bonetia-type rays arc biconical, but with a distinct if only isolated rays are preserved rather than complete inflection between the joined and free parts. The rays are spicules.
138 Fossil didemnid ascidian spicules
Fig. 1. MicrrrsL.itfires-type. Bonetia-type, Ri,qrrirdicr-typc and Monniotin-type spicule rays.
CONCLUSIONS overlooked by many palaeontologists because of their small Didemnid ascidian spicules should have been more widely size, their tendency to break up in to individual spicule rays, reported in the fossil record, but have probably been and possible confusion as to their organic origin. Future
13’) Varol & Houghton
conical rays which have a greater diameter in the joined part of the ray than the free part (Bonetia-type rays).These rays radiate from the centre of the spicule. Different species of this genus are distinguished by the number of rays, shape of the free part, and ratio of the length of the free part to that of the joined part of the rays. Remarks. Bonetiu differs from Micrascidires by having rays which are greater in diameter along the joined part of the ray, whilst the latter has rhomboidal rays. Bonefia is a spherical spicule, whereas Micrascidites is a stellate spicule. Other spherical spicules, Rigaudia and Monniofia, are distinguished from Bonetiu by having rays with a cylindrical free length and needle-like bundle rays respectively. Bonetia acuta sp. nov. (PI. 1, fig. 9; PI. 2, figs 6, 9: P1.3, fig. 4: P1.4, fig. 14) 1993 Tunicate spicules Wei: pl. 1, figs 1-2. Derivation of name. From latin acutus ( = sharpened). Diagnosis. Species of Bonetia with spicules containing 20-30 rays in which the free part is conical with a length greater than that of the joined part. Holotype. PI. 2, fig. 9. (NF514lNeg. 9). Type level and locality. Late Pleistocene (Zone NN21), Red Sea (DSDP Leg 23, Site 229A, Core 2, Section 5, 40-45 cm). side view plan view Dimensions of holotype. Diameter of spicule = 29.0 pm Fig. 2. Structural units ol Micruscidites. length of free part of rays = 8.5 pm. Remarks. B. acutu is distinguished from B. hreuis by having fewer rays (20-30) and by the length of the free studies on didemnic spicules should concentrate on mapping part of the rays always being greater than that of the their areal distribution in sediments and also provide jointed part. B. truncuta and B. qiiasitruncata have rays detailed morphological descriptions. Such studies should be with truncated free parts. particularly useful in palaeoenvironmental analysis of Occurrence. Pliocene to Pleistocene of the Red Sea, fine-grained sediments and also should determine their value Middle Miocene of southern Turkey, and middle Miocene as biostratigraphical markers. to Pleistocene of Indonesia, India, West Africa and Egypt. The aragonitic spicules of didemnid ascidians are more susceptible to solution than the calcitic remains of coccoliths Bonetia brevis sp. nov. and foraminifera. The didemnid spicules, like aragonitic (PI. 2, fig. 8; PI. 3, fig pteropods, are therefore likely to be better preserved in Derivation of name. From Latin hreuis ( = short). basins having high bottom water temperatures, sluggish Diagnosis. Species of Bonetiu with 40-60 rays per spicule circulation, and rapid sedimentation rates such as the which have the conical free parts shorter than the joined Mediterranean Sea. Red Sea and the Persian Gulf. part of each ray. Holotype. PI. 2, fig. 8 (NF514/Neg. 8). SYSTEMATIC DESCRIPTIONS Type level and locality. Late Pleistocene (Zone NN21), Subphyllum Tonicata Lamarck. 1816 Red Sea (DSDP Leg 23, Site 229A Core 2, Section 5, Class Ascidiacea Blainville, 1825 40-45 cm). Order Enterogona Perrier, 1898 Dimensions of holotype. Diameter of spicule 21.0 pm: Suborder Aplousobranchia Lahille, 1886 length of free part of rays 3.0pm. Family Didemnidae Milne Edwards, 1891 Occurrence. Late Pleistocene sediments of the Red Sea Genus Bonetia Varol & Houghton, gen. nov. and Middle Miocene sediments of southern Turkey. Type species. Bonetia hrevis sp. nov. Bonetia quasitruncata sp. nov. Derivation of name. In honour of Dr. F. Bonet, Mexico. (PI. 2, fig. 5: PI. 4, figs 9-10) Diagnosis. Spherical spicules with conical or truncated Derivation of name. From latin quasi ( = almost).
~~~~~ Explanation of Plate 1 Note that all SEM micrographs are from the Late Pleistocene of the Red Sca (DSDP Leg 23, Site 229A). unless otherwise stated. Figs 1-4. Micmrcidiries uirlgurir: fig. 1, x4200: Fig. 2, X4900; Fig. 3, X6300; Fig. 4, X9800. Figs 5-8. Rigairdia niirlriradiata sp. nov. Holotype (Fig. S): Fig. 5, X4900: Fig. 6, X 14 700: Fig. 7, XS600: Fig. 8, X 12600. Fig. 9. Bonetiu uciitu sp. nov. X770O.
140 Fossil didemnid ascidian spicules
'1 2 3
6 -4 5
7 8 9 Plate 1
141 Varol & Houghton
2 3
5 6
7 8 9 Plate 2
142 Fossil didemrtid ascidian spicules
Diagnosis. Species of' Boneria with 20-30 rays per spicule Type level and locality. Late Pleistocene (Zone NN21), in which the free part is a truncated cone in shape. Red Sea (DSDP Leg 23, Site 229A, Core 2, Section 5, Holotype. PI. 2, figs 5 (NF514/Neg. 6) depth 40-45 cm). Type level and locality. Late Pleistocene (Zone NN21), Dimensions of holotype. Diameter of spicule = 19.5 pm: Red Sea (D!jDP Leg 23, Site 229A, Core 2, Section 5, maximum diameter of rays = 1.7 pm. 40-45 cm). Remarks. R. multiradiata differs from R. p,raecisa by Dimensions of holotype. Diameter of spicule = 21.0 pm: having a greater number (70-90) of thinner and longer length of the free part of the rays 2.5 pm. rays, than the latter which has 30-45 thicker and shorter Remarks. B. yuasitruncata differs from R. tritncafa by rays. having rays with distinct truncated cone-shaped free parts, Occurrence. Pleistocene sediments of the Red Sea and the whereas the latter has a higher number of rays that are Gulf of Aden. Also recorded by Edwards (1973) in practically wi1:hout a free part. Pleistoce sediments from Leg 21 of DSDP in the Occurrence. Pleistocene sediments of the Red Sea and the southwest Pacific. Gulf of Aden. Bonetia truncata sp. nov. Rigaudia praecisa sp. nov. (PI. 2, fig. 7) (PI. 2, fig. 4: PI. 4, figs 15-17) Derivation of name. From latin (=cut off), Derivation of name. Latin tricncutus ( = cut off), referring praecisa, to the truncated free part of the rays. referring to the truncated peripheral ends of the rays. Diagnosis. Species of Bonetin having spicules containing Diagnosis. species of Rigaicdia having 30-45 moderately 35-50 mys without free parts. thick and short pencil-like rays radiating from the centre Holotype. PI. 2, fig. 7 (NF414,"eg. 5) of the sphere. Type level and locality. Late Pleistocene (Zone NN21), Holotype. PI. 2, fig. 4 (NF514/Neg. 4). Red Sea (DSDP Leg 23, Sile 22YA, Core 2, Section 5, Type level and locality. Late Pleistocene (Zone NN21), 40-45 cm). Red Sea (DSDP Leg 23. Site 22A, Core 2, Section 5. 40-45 cm). Dimensions of holotype. Diameter of spicule = 12.0 pm, Dimensions of holotype. Diameter of spicule = 14.5 pm; maximum diameter of rays = 2.0 pm). Remarks. B. truncata is distinguished from other species maximum diameter of rays = 2.7 pm. of Ronc-tia by having spicules with rays practically without Occurrence. Pleistocene of the Red Sea, Gulf of Aden. a free part. Indonesia and Egypt. Occurrence. Pleistocene sediments of the Red Sea and Gulf of Aden. Genus Micrascidites Deflandre & Deflandre-Rigaud, 1956 Type species. Micrascidites vulgaris Deflendre & Genus Rigaudia Varol & Houghton gen. nov. Deflandre-Rigaud, 1956. Type species. Rigaudia multirudiata sp. nov. Remarks. Stellate spicules with rhomboidal or biconical Derivation of name. In honour of Dr M. Deflandre- rays. Rigaud, Paris.. Diagnosis. Slpherical spicule having numerous rays in Micruscidites yaucirudiatus sp. nov. which the free part is cylindrical with a truncated distal (PI. 3, fig. 2: PI. 5, figs 11-12) end. These rays radiate from the centre of the sphere. 1993 'Tunicate spicules Wei: pl. 2, figs 1-3, 8. The rays are partly joined and the inter-ray areas are Derivation of name. From Latin paucit (=few in usually narrow. Species of this genus are distinguished the number), referring to the low number of rays. length. diameter, number and density of rays. Diagnosis. species of Micruscidites having three to five Rigaudia multiradiata sp. nov. large rhomboidal rays in which the length of the free part (PI. 1, figs 5-8: PI. 5, fig 1-4) is at least five times, and maximum diameter is at least 1973 Micrascidities vulgaris 19.56 Edwards: 663, PI. 2. tigs 1, two times, greater than the length of the jointed part. 3-4. Holotype. PI. 5, fig. 11 (NF514/Neg. 11). l9Y3 Tunicate spicules Wei: PI. 2, figs 12, 14-15. Type level and locality. Late Pleistocene (Zone NN21), Derivation of name. From latin multics ( = many): radius Red Sea (DSDP Leg 23, Site 229A, Core 2, Section 5, ( = ray), referrring to the high number of rays. depth 40-45 cm). Diagnosis. Species of Riga~4diawith 70-90 thin cylindrical Dimensions of holotype. Diameter of spicule = 21.5 pm; pencil-like rays which leave narrow inter-ray spaces. maximum length of rays = 11.0 pm, maximum width Holotype. PI. 1, fig. 5 (NF514/Negs. 1). 5.0 pm, maximum length of joined part = 2.0 pm.
Explanation of Plate 2 Figs 1-3. Monriiotiu fuscicidatrr sp. nov. Holotype (Fig. 3): Fig. 1, X4200: Fig. 2, XI6 100: Fig. 3, X7700. Fig. 4. Riguitdiu praeisa sp. nov. Holotype: X7700. Fig. 5. Bonvfiri qilusirrirncutrr sp. nov. Holotype: X4900. Figs 6, 9. Honrtia aciira sp. nov. Holotype (Fig. 9): Fig. 6, X4900; Fig. 9, X.42(K). €ig. 7. Boneria trrincutn sp. nov. Holotype: X7700. Fig. 8. Bonrrirr hrruih sp. nov. Holotype; X4900.
143 Varol & Houghton
I
2
3
4 5
6 7
Plate 3 Fossil did'emnid ascidian spicules
Remarks. M. pauciradiatus is distinguished from M. the spicule rays extend to the centre of the spherical uulgaris by having fewer rays (.3-5) and a greater ratio of spicule. length of free part to that of the jointed part of the ray. Dimensions of holotype. Diameter of spicule 15.0 pm; This ratio is more than 4:1 in ,IM. paucirudiutus whereas it maximum diameter of bundle = 3.5 pm; maximum dia- is less than 3 : 1 in M. vulgaris. meter of rays = 0.7 pm. Occurrence. Middle Miocene sediments of southern Remarks. M. fusciculata is distinguished from M. aciformis Turkey ;and Indonesia, and Pliocene to Pleistocene by having rays constructed from bundle-like elements and sediments of the Red Sea, Gulf of Aden, Indonesia and with a free part. M. aciformis lacks bundle-like structures Egypt. and has a greater number of rays. Micrascidites uulgaris Deflandre & Deflandre-Rigaund, 1956 (PI. 1, figs 1-4: PI. 3, fig. I; PI. 5, figs 5-9) Remarks. The number of rays varies between 8 and 30. Monniotia aciformis sp. nov. The free parts of the rays are conical with bluntly pointed (PI. 4, figs 5-7) peripheral ends. Further subdivision of this species may be 1993 Tunicata spicules Wei: pl. 2, fig. 13. possible using inumber of rays and ratio of the length of Derivation of name. From Latin ucus, (=needle), and the free part to that of the joined part. forma ( = form) referring to the shape of the rays. Occurrence. This species has been reported from Eocene Diagnosis. Species of Monniotiu having innumerable to quaternary sediments (Table 2). In the present study it needle-like unequal rays without any free part. Only some is also recorded from deposits of similar age worldwide. of the longest rays extend to the centre of the sphere. Genus Monniotiu Varol & Houghton gen. nov. Holotype. PI. 4, fig. 5 (NF514/Neg. 10). Type and locality. Late Pleistocene (Zone NN21), Red Type species. Monniotiu fasciculutu sp. nov. Sea (DSDP Leg 23, Site 229A, Core 2, Section depth Derivation of name. In honour of Dr F. Monniot, Paris. 5, Diagnosis.. Spherical spicules having rays which are 40-45 cm). needle-like and: unequal in length, only some of whirh Dimensions of holotype. Diameter of spicule = 10.5 pm. Remarks. is distinguished from extend to the centre of the sphere. The rays may or may M. aciformis M. fasciculata by having a greater number of rays and the absence of not have ;I free part. bundle-like elements. In addition, the rays in Remarks. Monniotia differs from other spherical spicules M. aciformis have no free part. such as Bonetia and Rigaudia by having rays constructed Occurrence. occurs in Pleistocene sediments of needldike elements (Monniotia-type), which taper M. uciformis of the Red Sea. towards the 'centre of the spicule. The composite Monnioticz spicule rays all radiate from the centre of the sphere. In contrast, the genera Bonetia and Rigaudia have conical truncated conical rays and truncated cylindrical or ACKNOWLEDGEMENTS rays which all radiate from the centre of the sphere Mr D. Harrison (Simon Petroleum Technology), Dr J. respectively. Young, Dr Wuchung Wei and an anonymous reviewer are Monniotia fusciculata sp. nov. thanked for their help, advice and constructive review on a (PI. 2, figs 1-3; P1. 4, figs 1-4) draft of the manuscript. Thanks are also due to Mr A. 1993 Tunicate spicules Wei: P1. IL, fig. 1. Davies (University College North Wales, Bangor) for Derivation of name. From Latin fusciculutus, ( =joined in assistance during SEM examination. Samples from DSDP small bundles), referring to the construction of rays from Site 292A were aupplied by the Ocean Drilling Program. needle-like elements. Diagnosis. Species of Monnioticr having spicules with rays which are arranged in bundles and which have no free parts. Received May 1993 Holotype. PI. 2, fig. 3 (NF514/Neg. 3). Accepted August 1995 Type level andl locality. Late Pleistocene (Zone NN21), Red Sea (DSDP Leg 23, Site 229A, Core 2, Section 5, depth 40-45 cm). REFERENCES Description. Spherical spicules containing 20-40 bundle- Barnes. R. D. 1980. lnuertehrute Zoologv. Saunders College, like spicule rays. Each spicule ray is constructed of 10-20 Philadelphia. needle-like elements which are unequal in length. Each Beall, A. & Fischer, A. G. 1963. Sedimentology. In Ewing, M.. ray consists of a fee part and joined part. Only a few of Lamar Worzel, J. et ul. Initial Reports of the Deep Sea Drilling
Explanation of Plate 3
Fig. 1. Micrascidites uulgaris sp. nov. X 12 000. Fig. 2. Micmscidites puucircrdiatus sp. nov. X 11 000. Fig. 3. Rigaudia cf. praecsia sp. nov. x 12 000. Fig. 4. tlonetia acuta sp. nuv. X 1.5 000. Fig. 5. Boneria hrevrs sp. nov. From middle miocene of southern Turkey X 14 000. Fig. 6. Bonetia? sp. sp. n(ov. X6800. Fig. 7. 13onetia quasitruncata sp. nov. X3.500.
145 1 2 3 4
5 6 7 8
9 10 11
12 13 14
15 16 17 18 Plate 4 Fossil tlidemnid ascidian spicules
Program, 1: 521-593, (IS Government Printing Office, Washington. Durand. s. & Pelhate, A. 1961. A propos des microfossiles des I sediments dandriens du Massif armoricain. Compre Randue de Bergen. J. A. 1985. Nannofossil Biostratigraphy at Site 585, ~~~t somm. SociCtC de GCologie France. 6: 167-168. Mariana Basin. In Moberly, R., Schlange R, S. 0. el 01. /nl/jal Edwards, A. R. 1973. Calcareous nannofossils from the southwest RePorls of !’he Deep Sea Drilling Project, 89 285-296, US Pacific Deep Sea Drilling Project, Leg 21. In Kennett, s. p., Government Printing Office, Washington. Houtz, R. E. et al. Initial Reports of the Deep Sea Drilling Project. Rerrill, hi. J. 1950. The tunicata, with an account of British species. 21: 641 -691. Us Government printing Press, Washington, Proceedings of the Royal Society of London, 133: 1-354. Elredge. L. G. 1966. A taxonomic review of Indo-Pacific didemnid Blainville. H. M. D. de. 1825. Manuel de Malacologje de ascidians and description of twenty three Central Pacific species. Conchdogie. Libraire F. G. Lavrault Libraire, Paris. Micronesic, 2: 161-216. Boekschoten, 1981. Autopalaeontology of Ascidians. Netles Hardman, W. A. 1886. Report on the tunicata collected during the Jahrhuch Palaontologie Ahhandlungen. 2: 76-83. voyage of the H.M.S. Challenger during the years 1873-1876. Bonet. F. & Benveniste-Velasquez, N. 1971. Espiculas de ascidies Part 11. Ascidia compositae. Report of the Scientific Results of the foSiks 1‘ actulaes. Revista del lnstitirto Mexicano del Petroleo, 3: Voyage of the H.M.S. Challenger. Zoology, 14 1-43. 8-35. Heckel, H. 1973. Late Oligocene to Recent nannoplankton from the Bouche, F. M. 1962. Nannofossiles calcaires du LutCtien du Bassin Capricorn Basin (Great Barrier Reef Area). Geological Slrrvey of de Paris. Revitr de MicropalContologie, 5: 75- 103. Queerisland Puhlication, 359 1-24. Bralower, T. J., IBown. P. R. & Siesser, W. G. 1991. Significance of Houghton, S. D. & Jenkins. D. G. 1988. Subtropical microfossil IJpper Triassic nannofossils from the Southern Hemisphere indicators from the Pliocene Celtic Sea. Marine Geology, 79 (ODP Leg 122, Wombat Plateau, NW Australia. Marine 119-126. Micropaleontology, 17: 1 19- 154. Jafar. S. A. 1983. Significance of late Triassic calcareous Brookfield. M. E. 1988. Where are all the fossil sea squirts’? nannoplankton from Austria and southern Germany. Neues Micropa/eonto180gy,34: 277-283. Jahrbuch Geologic, itnd Palaeontologie A bhandlungen, 166 Ruge, E. $3~Monniot, F. 1972. Nouveaux spicules d’Ascidies de 21 8-259. I’YprCsian du hassin de Paris et du Toarcicn des Deux-Seures. Kok, C. P. 1985. An early Cretaceous nannofossil from the central Geobios. 5: 83-90. North Sea. International Nannoplankton Newsletter, 2 38. Bukry, D. 1975. Coccolith and silicoHagellate stratigraphy, North Kott, P. 1969. Antarctic Ascidiacea, Volume 13, Antarctic Research western Pacitic Ocean Deep Sea Drilling Project Leg 32. In Series. American Geophysical Union, National Academy of Larson, I<. L., IMoberly, R. et al. initial Reports of the Deep Sea Sciences Publication No. 1725. Drilling Project, 32: 677-701, US Government Printing Office. Lafargue, P. F. & Kniprath, F. 1978. Formation des spicules de Washington. Didemnidae. Marine Biology, 45: 175-184. Chauvel, J. 1952. Microfossiles du Pliocene se Saint-Jean-la-Poterie Lahaille, F. 1886. Sur la classification des tuniciers. Cornptes Rendu (Morbihan). 76 Congres ile SoriCtC de Savantes, Rennes. 19.51, de I’Academie des Sciences de Paris, 102: 1573-1575. 159-162. Lamarck, J. B. 1816. les tuniciers (Tunicata). Histoire naturelle des Cita. M. B. 1973. Inventory of biostratigraphical findings and animaux sans vertCbrCs. Lihraire VerrliBre, Paris, 3: 80- 130. problems. In Ryan, W. B. F., Hsu, K. J. et ul. Initial Reports of the Land, L. S. 1970. Phreatic versus meteoric diagensis of limestones. Deep Sea Drilling Project, 13: 1045-1065, IJS Government Evidence from a fossil water table. Sedimentology, 14 175-185. Printing Ofice, ’Washington. Lazaud, L. 1966. Les nannofossiles calcaires de la formation de C‘ita, M. R. & Gartner, S. 1971. Deep Sea Upper Cretaceous from Varengeville (Cuisien, cap D’Ailly, Seine-Maritime). Bulletin de the Western North Atlantic. In Farinacci, A. (Ed.), Proceedings la SociPtP GCologie de Normandie. 56: 41-44. of the I1 Planktonic Conference Roma 1970. Edizioni Tccno- Loewig, C. & Koelliker, R. E. von 1846. Observations sur scienza, 1: 287-319. I’existence d’une substance ternaire, identique avec la cellulose DeHandre. <;. & Deflandre-Rigaud, M. 1956. Micrascidites manip. dans une classe d’animaux sans vertCbrCs, les Tuniciers. Comptes nov., sclerites de Didemnides (Ascidies, Tuniciers) fossiles due Kendue de I’AcadCmie des Sciences de Paris, 22: 38-40. LutCtian ,du Bassin Parisien et du Balcombien d’Australia. Matthews, R. K. 1966. Genesis of recent lime mud in Southern Compte Rtwtiue Sommaire de la SocittP GPologique de France, 4 British Honduras. Journal of Sedimentary Petrology, 36: 428-454. 47-48. Michelsen, W. 1919. Zur Kenntnis der Didemniden. Abhandlungen I)eHandre-R~gaud,M. 1949. Quelques observations sur les spicules Naturwissenshasten. Herausgegeben vom Naturwissen- d’Eponges calcaires fossiles. Microscopie, 1: 151-161. schaftlichen Verein. Hamburg, 21: 1-44. [)enandre-Rigaud, M. 1956. Les sclerites d’Alcyonaires fossiles. Milne Edwards, H. 1841. Observations sur les acidies composees Elements d’une especie nouvelle: N. .stellatus. Cahiers de des cClt&s de la Manche. Memoires de I’AcadCrnie Royale Sciences Micropalb~~ntologie.1: 1-7. de la Institiite de France, 18: 217-326. Detlandre-Ri5aud, M. 1968. Remarques sur le genre Neanthozoites Monniot, F. 1970. Cystodytes incrassatus nov. sp. Ascidie fossile du DeH.-Rig. ;3 propos d’une espece nouvelle: N. stellatatiru Cuhiers Pliocene, Breton. Compte Rendu de I’AcadCmie des sciences de tle MicropalContologie. 1: 1-7. Park, ser. D., 271: 2280-2282. Durand. S. 1048. Presence de spicules d’Ascidies dans le Redonien Monniott. F. & Buge. E. 1971. Les spicules d’ascidies Cossiles et d’ Apigne (Ilk-et-.Vilaine). Conzpte Rendiie de 1’AcadCmie des actuelles. Annales de Puliontologie, 57: 93-105. Sciences de ftzr
147 Varol & Houghton
1 2 3
4 5 “6
7 9
12 10 Plate 5 n 148 Fossil dideninid ascidian spicules
Perrier, E. 1898. Note sur le classification des Tunciers. Compte Kokia (incertae sedis). Journal of Nannoplankton Research, 16 Rendue de Academie de Sciences de Paris, 126 1758-1762. 75-77. Plough, H. H. 1978. Sea squirts of the Atlantic continental shelf from Varol, 0. 1983. Late Cretaceous-Palaeocene calcareous nannofos- mainc. to Te,ras. John Hopkins University Press, Baltimore. sils from the Kokaksu Section (Zonguldak, Northern Turkey). Prenant, M. 1925. Contributions a I’itude cytologique de calcaire. Neus Jahrbuch Palaontologie Abhandlungen, 166: 431 -460. 11. Siir les condition de formation des spicules chez les Varol. 0. 1985. Miocene calcareous nannofossils from the Mut Dideninidae. Bulletin de Biologie de France et Belgique, 59 basin, southern Turkey. Journal of Micropalaeonrology, 4: 403-453. 127-139. Purdy, Ei. G. 1963. Recent calcium carbonate facies of the Great Varol, 0. & Girgis, M. H. 1994. New taxa and taxonomy of some Bahania Bank. 1. Petrography and reaction groups. Journal of Jurassic to Cretaceous calcareous nannofossils. Cretaceous Geolo!;y, 71: 334-355. Research, Neues Jahrbuch Palaontologie Abhandlungen, 192 Rae, B. M. 1967. The food of cod in the North sea and on the west 22 1-253. coast of Scotland. Marine Research, 1: 1-68. Wei, W. 1993. Abundance patterns of Tunicate spicules at the Great Stiegletz, R. D. 1972. Scanning electron microscopy of the Barrier Reef-Queensland Plateau Transect sites: Implications for fine-grained fraction of Recent carbonate sediments from downslope transport and Early Pleistocene initiation of the Bimini. Bahamas. Journal of Sedimentology and Petrology, 42 Central Great Barrier Reef. In McKenzie. J. A,, Davies, P. J.. 211-226. Palmer-Julson, A. et al. Proceedings of the Ocean Drilling Van Name, W. G. 1945. ’The North and South American Ascidians. Program, Scientific Results, College Station, TX (Ocean Drilling Amerkin Mu.reum of Natural History Bulletin, N. Y.,84: 1-476. Program) 133: 447-453. Van Name, W. G. 1952. Tunicata. The “Manihiae” Expedition to Woodland, W. N. F. 1907. Studies in spicule formation. VI. The the Gulf of A gaba (VIII). Bulletin of the British Museum scleroblastic development of the spicules in some Mollusca and in (Natural History), Zoology Series, 1: 215-220. one genus of colonial ascidians (Leptoclinum). Quarterly Journal Van Niel, B. E. 1994. Scanning electron micrographs of the genus 0.f the Microscopic Society, 51: 45-53.
- Explanation of Plate 5 All figs X240. Figs 1-4. Rigaudia multiradiata sp. nov. Figs 5-9. Micrascidiies vulgaris sp. nov. Fig. 10. species and genus indeterminate sp. nov. Figs 11-12. Micrascidites pauciradiatus sp. nov. Holotype (Fig. 11).
149