PALEOCENE BIVALVES FROM THE PEBBLE POINT FORMATION, VICTORIA, AUSTRALIA Thomas A. Darragh Museum of Victoria, 285 Russell Street, Melbourne, Victoria 3000 Darragh, Thomas A., 1994:12:31. Paleocene bivalves from the Pebble Point Formation, Victoria, Australia. Proceedings of the Royal Society of Victoria 106: 71-103. ISSN 0035-9211. Thirty-two bivalve taxa arc recorded from the Paleocene Pebble Point Formation, Otway Basin, Victoria, Australia, of which 11 are newly described and 17 are recorded in open nomenclature. New species are LameUinucula pyrenoides, Austra/oneilo cu/trata, Limopsis rupestris, Myrtea faseolata, Cyamiocardium silicula, Astarte (Astarte) notialis, Venericardia (Rotundicardia) petraea, Carditel/opsis bel/issima, Bertinella lapidaria, Dosinia (Dosinobia) saxalilis, Ca/listina (Tikia)? scopulensis. The environment was one of high energy, shallow water and the climate was probably cool temperate. The fauna is composed mostly of genera that were cosmopolitan during the Paleocene and shows no close affinity with any other, suggesting considerable isolation from other Paleocene faunas. Lahillia and Australoneilo are the only taxa with a particular Antarctic and South American affinity and Lahillia, Dosinia (Dosinobia) and Callistina (Tikia)? have an affinity with New Zealand. Eotrigonia is the only endemic genus present. Keywords: Bivalvia, Late Paleocene, Otway Basin, Victoria, Australia, palaeoecology, bio¬ geography, taxonomy, new taxa. PALEOCENE MOLLUSCAN FAUNAS occur in corioensis ‘very thick variety’ from east of the Australia in the Carnarvon, Perth and Otway Gellibrand River based on Wilkinson’s collection. Basins, but despite their importance have received little attention. Factors in this neglect are the restricted and poor outcrop, the sparsely fossil- PREVIOUS WORK iferous nature of the rocks and the very hard matrix making extraction difficult. The only formally named molluscs in the fauna Paleocene faunas arc potentially important in of the Pebble Point Formation are two nautiloid providing clues to the origin of the later Tertiary cephalopods, Aturoidea distorts and Nautilus vic- faunas of Australia and to the nature of the fauna torianus (Teichert 1943); three bivalves, Nuculana present in the region at the time of the separation paucigradata, Cucullaea (Cucullona) psephea and of the Australian plate from the Antarctic plate. Lahillia australica, and a scaphopod, Dentalium They are also critical for understanding the faunal (Fissidentaliurn) gracilicostatum (Singleton 1943), recovery and evolutionary radiation following the all described from collections made by George end-Cretaceous mass extinction. Baker, who studied the stratigraphy and sediments The bivalves described here occur in the Pebble of the coastline between Moonlight Head and Point Formation in the Otway Basin, Western Curdies Inlet (Baker 1943). Teichert (1943) and Victoria. Of the other Paleocene formations of Singleton (1943) recognised that the fauna was Australia, the Cardabia Calcarenite (including the the oldest known from the Australian Tertiary. Boongarooda Greensand Member, Wadera and Teichert concluded that the age was Eocene and Pirie Members) in the Carnarvon Basin, Western Singleton that the age was Early Eocene or possibly Australia contains few bivalves and there is nothing Paleocene. Singleton recognised links between the in common with the Pebble Point Formation; the bivalves and those in South America, Antarctica King’s Park Shale in the Perth Basin is known only and New Zealand. from subsurface (McGowran 1964). In 1986 Darragh described a further bivalve, Molluscs now known to be of Paleocene age were Eotrigonia pa/eocenica. first collected by C. S. Wilkinson from Pebble The foraminiferal fauna was described by Point (his locality Aw 6) during his geological McGowran (1965), who concluded that it was of survey of the Otway Ranges and coast in 1864 middle Paleocene age, correlated with Zone P3, (Wilkinson 1865). The molluscs were never des¬ Globorotalia pusilla pusilla-Globorotalia angulata cribed, though McCoy (1876) recorded Cucullaea zone. Later McGowran (1991) refined this cor- 71 72 THOMAS A. DARRAGH relation, stating that the Pebble Point marine On the Otway coast the formation consists of transgression fell near the P4/P5 boundary, late 20-30 m of coarse quartzose sandstone, grits Paleocene (Thanetian or Seelandian). conglomerate and gritty ferruginous clays (Baker 1950). When fresh the rock matrix has a bluish colour. In outcrop along the coast it is highly LOCALITY AND NATURE OF FORMATION ferruginous and cemented owing to oxidation, but The Pebble Point Formation outcrops in coastal the carbonate fossils are still preserved. Fossils are cliffs between Moonlight Head and the mouth of not uniformly distributed but found in a narrow the Gellibrand River. It transgressively overlaps the band about 3 m thick about 10 m above the base early Cretaceous Otway Group sediments and is of the formation. Other macrofossils present are conformably overlain by the Dilwyn Formation rare solitary corals, shark teeth, fish vertebrae and (Late Paleocene-Early Eocene) (Baker 1950). Mol¬ crab remains. luscs are extremely rare in the formation. Inland Matrix adhering to the fossils is very fine¬ it outcrops in western Victoria in the valleys of grained, limonitic, often cemented, with fine to the Wannon River and Grange Burn west of coarse quartz grains embedded in it. In less Hamilton and at Killara Bluff on the Glenelg River weathered matrix glauconite pellets are common. and opposite at Bahgallah south of Casterton. The ferruginous matrix contains siderite which in These inland outcrops are highly ferruginised and many cases bonds chemically to the shell smother¬ weathered. No carbonate has survived and fossils ing fine detail of the shell surface. It is impossible are difficult to determine. At Killara Bluff where to remove this coating without damage to the the calcium carbonate of the fossils has been shell itself. replaced by limonite (Kenley 1951, 1971), Kenley Since it is very difficult to collect fossils in situ, (1954) recorded 16 m of ferruginous sands and fine recourse has to be made to beach boulders, from conglomerates containing Nucuiana paucigradata, which most fossils have been collected. Fossils in Cucullaea (Cucullona) psephea, Eotrigonia sp., partially weathered boulders can be separated from Lahillia australica, Panopea sp. and Aturoidea the matrix by careful picking with needles. Fossils distorts. exposed on the surface of indurated boulders Spencer-Jones (1971) recorded thick-bedded, can only be collected with hammer and chisel heavily ferruginised coarse to fine gravels, coarse and their preparation is extremely difficult and and fine sandstone, pebbly sandstone and limonitic time-consuming. siltstone in the valleys of the Wannon River and Grange Burn in the area of the Parkhill and Morgiana Estates and extending southwest to the Locality Miakite Creek valley. A maximum thickness of The details of the localities from which material 61 metres was recorded near the Parkhill Estate was collected are as follows. The numbers are from southwest of Wannon. These sediments overlap the the Museum of Victoria fossil locality register and Late Cretaceous Otway Group sediments and in are used throughout to save repetition. turn are overlain by formations of the Oligocene to Miocene Heytesbury Group. PL 3001 SE side of Dilwyn Cove, N side of Bell Fossils, abundant at some localities, are found Point, 6 km SE of Princetown, from boulders on in these sediments as moulds, but in most cases beach derived from 0.5 m grey (weathered) so ferruginised that determination is not possible. sandstone about 15 m above beach, Victoria, At some localities where the ferruginous siltstones Princetown 903100. outcrop, well preserved moulds can be found which PL 3002 N side of Dilwyn Cove, S side of Pebble enable a determination to be made. Fossils collected Point, G.S.V. loc. Aw6, 5 km SE of Princetown, by D. Spencer-Jones in 1964 from two such local¬ Victoria, Princetown 900103. ities have been examined. The bivalve fauna is PL 3003 Cove between Buckley Point and Point reasonably diverse and all determinable fossils Pember, 4.5 km SE of Princetown, Victoria, occur in the Pebble Point Formation on the coast. Princetown 894109. Therefore, it is reasonable to infer that these PL 3004 Shelly band about 10 m above beach, ferruginous sediments arc a lateral extension of the NW side of Buckley Point, 4 km SE of Prince¬ Pebble Point Formation. This means that the town, Victoria, Princetown 894109. Paleocene marine incursion in the Otway Basin was PL 3005 W end of large slip at Killara Bluff at far more extensive than previously realised and top section, allot. 4, sect. A, Parish of Killara, extends inland nearly as far as the later Miocene Victoria, Dartmoor WD313291. incursion. PL 3006 Ironstone about 100 m above river, right PALEOCENE BIVALVES FROM THE PEBBLE POINT FORMATION 73 bank of Glenelg River on Hazell Bank, Bahgallah, Lucinidae Jagolucina’l sp. Victoria, Dartmoor WD324296. lucinid A pL3176 Cutting on Morgiana Road, about 5 km lucinid B south of Wannon, left bank Grange Burn, Cole¬ Myrtea faseolata sp. nov. Thyasiridae Thyasira sp. raine WD 760267. Ungulinidae Felaniella (Zemysia) sp. pL3177 South Bowing gully running into right Erycinidae Borniola sp. bank of Grange Burn, about 0.5 km south of Cyamiidae Cyamiocardium silicula sp. nov, Clayton’s Road, 3.5 km southeast of Wannon, Astartidae Astarte (A.) notialis sp. nov. Coleraine WD729253. Carditidae Venericardia (Rotundicardia) petraea sp. nov. jvlost of the material described here was collected Carditellopsis bellissima from fallen boulders at PL3003. sp. nov. Lahilliidae Lahillia australica Singleton Tellinidae Bertinella lapidaria sp. nov. Veneridae Dosinia (Dosinobia) saxatilis ENVIRONMENT AND DEPOSITION sp. nov. Callistina (Tikia)? scopulensis Baker (1950) suggested that the Pebble Point For¬ sp. nov. mation consisted of littoral, shallow-water deposits Corbulidae Caryocorbula sp. and McGowran (1965) stated that the foraminifera Hiatellidae Panopea sp. indicated a shallow-water, open marine environ¬ Cuspidariidae Cuspidaria sp. ment. The bivalves suggest a similar environment. Verticordiidae Verticordia sp. A majority of specimens show signs of abrasion suggesting that the specimens were transported some distance before burial. There are few arti¬ culated pairs of valves extant. Of these pairs, Table showing numbers of specimens used in this study. specimens of Bertinella? lapidaria sp. nov. are the most common. Even the infaunal species, such Limopsis rupestris sp. nov. 394 Astarte (A.) notia/is sp. nov. 319 as Panopea sp., have the valves disarticulated Ledina paucigradata Singleton 288 suggesting exhumation after death. Many species Bertinella lapidaria sp. nov. 114 have heavy robust shells. Such evidence, together Cucullaea psephea Singleton 94 with the coarse particles in the host rock, suggest Venericardia (Rotundicardia) petraea sp. nov. 82 a high energy, shallow-water environment. Anomia sp. 81 Dosinia (Dosinobia) saxatilis sp. nov. 65 Cyamiocardium silicula sp. nov. 64 Carditellopsis bellissima sp. nov. 51 BIVALVE FAUNA Lahillia australica Singleton 42 Eotrigonia paleocenica Darragh 31 There are 32 taxa recorded here but three are Lamellinucula pyrenoides sp. nov. 28 represented by such poor material that comparison Neilo (Australoneilo) cult rat a sp. nov. 24 with other taxa is not possible. In addition there Callistina (Tikia)? scopulensis sp. nov. 15 are two other taxa whose relationships are not clear Myrtea faseolata sp. nov. 13 as the material available may consist of juveniles. Comitileda sp. 11 Jagolucina'l sp. 10 The fauna so far identified is as follows: Electroma sp. 7 Nuculidae Lamellinucula pyrenoides Parvamussium sp. 7 sp. nov. Caryocorbula sp. 6 Nuculanidae Comitileda sp. Pycnodonte (Phygraea) sp. 6 Ledina paucigradata Singleton Verticordia sp. 4 Neilo (Australoneilo) cult rata Cuspidaria sp. 4 sp. nov. lucinid B 4 Cucullaeidae Cucullaea psephea Singleton Pinna sp. 4 Limopsidae Limopsis rupestris sp. nov. Panopea sp. 4 Pinnidac Pinna sp. limid 3 Pteriidae Electrotna sp. Thyasira sp. 2 Propeamussiidae Parvamussium sp. Felaniella (Zemysia) sp. 2 Anomiidae Anomia sp. Borniola sp. 1 Limidae limid lucinid A 1 Gryphaeidae Pycnodonte (Phygraea) sp. Total 1718 Trigoniidae Eotrigonia paleocenica Darragh 74 THOMAS A. DARRAGH TROPHIC COMPOSITION Epifaunal, attached, suspension feeding: Pycnodonte (Phygraea) sp. A valid trophic analysis of the fauna is not possible, because of the problems associated with collecting Infaunal carvivore: an unbiased sample. However, notwithstanding Cuspid aria sp. these problems, some broad generalisations can be made. It will be seen by comparing the numbers PREDATION of individuals given above with the generalised groupings below, that the fauna as a whole is Countersunk boreholes (total 57) are present on dominated by infaunal, suspension feeding bivalves 54 of the 1781 specimens studied. The holes were with a significant infaunal, deposit feeding com¬ probably bored by a small species of naticid ponent. Three infaunal species comprise well gastropod present in the fauna. Most of the holes over half (62%) the number of specimens. This (82%) were bored into 44 specimens of Astarte (A ) pattern of composition suggests very shallow water. notialis sp. nov. One specimen had two uncom¬ Nuculanids, tellins and astartids are very common pleted holes, a second had one uncompleted and elements in Recent northern hemisphere, cool one completed hole and a third specimen had two shallow-waters (Thorson 1957), but Li mops is does completed holes. All other bored Astarte had onlv not seem to have been recorded as a common one borehole. Other completed holes were found element in association with them. Attempts to com¬ on specimens of Jagolucina? (3), Cyamiocardium pare a Paleocene assemblage from the southern silicula sp. nov. (3), Carditellopsis bellissima sp hemisphere with Recent faunas of the northern nov. (3), and Bertinella lapidaria sp. nov. (2) hemisphere, or any other Recent fauna, should be treated with caution, because of the great TEMPERATURE difference in time and space. Also two of the most common elements in the Pebble Point fauna, It is only possible to give a very general indication Limopsis and Astarte, have living representatives of the water temperature in which the fauna which are eurybathyal. Limopsis aurita occurs from lived. The fauna as a whole is similar to northern 38 to 3175 m and Astarte sulcata from 10 to hemisphere Boreal faunas (see below) which pre¬ 2000 m (Ekman 1967). sumably lived in cool temperate water. There are no genera present which are found in the warm- water faunas of the Paleocene of Africa and Generalised grouping of species according to Asia. Species of genera such as Myrtea, Thyasira feeding type and habitat Felaniella, Borniola, and Carditellopsis are found Infaunal deposit feeding: living in cold to warm temperate waters off eastern Lamellinucula pyrenoides sp. nov., Comitileda sp., Australia. Ledina paucigradata Singleton, Neilo (Austra- loneilo) cult rata sp. nov., Bertinella lapidaria sp. RELATIONSHIPS WITH OLDER nov., Verticordia sp. AUSTRALIAN FAUNAS Infaunal suspension feeding: The only Late Cretaceous fauna described from Cucullaea psephea Singleton, Limopsis rupestris Australia is that from the Miria Formation sp. nov., Eotrigonia paleocenica Darragh, Jago- Carnarvon Basin, Western Australia (Darragh & lucinal sp., Iucinid A, lucinid B, Myrtea faseolata Kendrick 1991). Given the geographical and strati- sp. nov., Thyasira sp., Felaniella (Zemysia) sp., graphical separation of this fauna from that at Borniola sp., Cyamiocardium silicula sp. nov., Pebble Point, it could not be expected that Astarte (A.) notialissp. nov., Venericardia (Rotun- they would have much in common and, indeed dicardia)petraea sp. nov., Carditellopsis bellissima only three genera in the Miria fauna might have sp. nov., Lahillia australica Singleton, Dosinia provided an ancestor for Pebble Point genera: (Dosinobia) saxatilis sp. nov., Callistina (Tikia)? Pycnodonte (Phygraea), Panopea and Trigonia. scopulensis sp. nov., Caryocorbula sp., Panopea The first two are cosmopolitan genera and the sp. Pebble Point representatives may easily have been derived from some other source, the Antarctic or Semi-infaunal byssate, suspension feeding: Pinna New Zealand for instance. However, Trigonia miriana has many features similar to the Pebble Epifaunal, byssate, suspension feeding: Point Eotrigonia paleocenica and may belong to Electroma sp., Parvamussium sp., Anomia sp., an ancestral group of the Pebble Point taxon limid. (Darragh 1986). PALEOCENE BIVALVES FROM THE PEBBLE POINT FORMATION 75 RELATIONSHIPS WITH 2. A temperate to warm-temperate fauna in YOUNGER FAUNAS the Early Paleocene found in Europe in Belgium and France (Glibert & Van dcr Poel 1973) Species of Comitileda, Cucullaea, Limopsis, Pinna, and in America from New Jersey in the north Parvamussium, Anomia, Pycnodonte, Eotrigonia, as far south as Brazil (Gardner 1933). The Rotundicardia, Cardite/lopsis, Pa nopea, Cuspi- Paleocene fauna of the United States Pacific daria and Verticordia are found in Eocene rocks coast could also be considered as part of this in the Otway Basin. Though most of the Eocene group (Zinsmeister 1983). species do not seem to be closely related to the 3. A tropical to warm water. Early to Late Paleocene species, the species of Limopsis, Rotun¬ Paleocene Tethyan fauna extending from central dicardia and Carditellopsis do seem to be related. west Africa and north Africa eastwards as far The species of Comitileda, however, does seem to as India and Burma (Adegoke 1977). be close to Oligocene and Miocene species and 4. A southern hemisphere group of faunas from possibly represents the beginning of a lineage. isolated localities of varying ages in New Zealand Other than the Paleocene record, Myrtea is found (Finlay & Marwick 1937), Australia, Antarctica from Pliocene to Recent, Thyasira is known from (Zinsmeister & Macellari 1988) and southern Middle Miocene to Recent and Zemysia, Cyamio- South America. cardium and Borniola are only known in the Recent fauna of Australia. It seems unlikely that the The first and third of the above groups are Paleocene species are directly related to the relatively homogeneous. The second group can Miocene and living species, but species of the latter be divided into an American subgroup of rela¬ two genera are small to minute and too much tively homogeneous faunas and a European sub¬ emphasis should not be placed on their absence group. The two subgroups have much in common because such molluscs from the Australian Tertiary (Gardner 1933). have been little studied. The Pebble Point fauna has 10 genera, or about Pebble Point genera not found above the one third of the genera present, in common with Paleocene in Australia are Lamellinucula, Ledina, group one. These genera are all regarded as cosmo¬ Australoneilo, Astarte, Lahillia, Bertinella, Dosin- politan in cool to temperate waters. Many cosmo¬ obia and Caryocorbula. politan or widely distributed genera are also shared with the second group. None of the Pebble Point genera, except the cosmopolitan genus Pycnodonte BIOGEOGRAPHY (Phygraea), are shared with group three. An authoritative biogeographic analysis of the The only Paleocene faunas in the southern hemi¬ Pebble Point fauna is not yet possible because sphere are those at Pebble Point, the Wangaloan the generic placement of several of the species is fauna of New Zealand; on the Antarctic Peninsula doubtful. Equally the generic placement of many and in southern South America. species described from other Paleocene faunas The Wangaloan fauna, a moderately diverse, around the world is in doubt. Despite these prob¬ shallow water fauna comprising about 20 genera lems some general conclusions can be made, is significantly older than that at Pebble Point, however, as the taxonomy and relationships of being early Teurian or Danian (Beu & Maxwell Paleocene species become better known, modi¬ 1990). Faunas on the Antarctic Peninsula are also fication will no doubt be required. It should also diverse and are of shallow water origin, but are be emphasised that these conclusions are drawn either significantly older, Late Cretaceous ranging from a study of the bivalves only and information into the Early Paleocene, or much younger, Mid from the gastropods may modify them. to Late Eocene (Zinsmeister & Macellari 1988; Paleocene faunas arc not particularly widespread Stihvell & Zinsmeister 1992). Paleocene faunas in throughout the world and some have not yet been southern South America are so poorly known that the subject of modern revision, making comparison a comparison has not been attempted. difficult. They fall into four very broad groupings. At Pebble Point there are 32 bivalve taxa, of 1. An Early Paleocene Boreal fauna found in which only six seem to be related to taxa from Europe extending from Denmark in the west the Wangaloan (Ledina, Cucullaea, Electroma, as far east as the Volga Basin in Ukraine and Myrtea, Lahillia and Dosinobia). The Pebble Point possibly to Tashkent (Ravn 1939; Makarenko species of Ledina, Cucullaea, Lahillia and Dosi¬ 1970; Anderson 1973, 1974). In the Late Paleo¬ nobia are close enough to the Wangaloan taxa to cene, this fauna extended further south into the suggest that they are descended from them. A Anglo-Franco-Belgian Basin. further three taxa (Comitileda, Zemysia, Caryo- 76 THOMAS A. DARRAGH corbula) seem related to taxa from the Eocene of elements of the modern molluscan fauna were New Zealand. established (Darragh 1985). Only five taxa seem to be related to Antarctic forms; Australoneilo, Cucullaea, Pinna, Lahillia TERMINOLOGY and Panopea. These taxa are related to both Late Cretaceous and Late Eocene Antarctic forms. Of The tooth notation used in the descriptions is that these Cucullaea and Lahillia are shared with New of Boyd & Newell (1969). Zealand. Electroma also occurs in the Late Eocene All specimens are housed in the Invertebrate of Antarctica. However, Cucullaea, Pinna and Palaeontology Collection, Natural History Divi¬ Panopea are cosmopolitan genera and cannot be sion, Museum of Victoria, register prefix NMV P. regarded as necessarily indicating a close relation¬ Figured specimens were all whitened before ship between faunas. being photographed. Both Astarte and Cyamiocardium occur in Antarctic living faunas. Except as recorded here, SYSTEMATICS Astarte is not known living or fossil either in Australia or New Zealand. Astarte is considered Family Nuculidae a typical member of cool-water boreal faunas. Lamellinucula Schenck, 1944 In general the Pebble Point bivalves suggest considerable isolation from other Paleogene faunas Type species. Nucula tamatavica Odhner, 1943, Recent, and lend little support to the idea that southern Madagascar. Australia, or at least the Otway Basin, was part of the late Cretaceous-early Tertiary Weddellian Lamellinucula pyrenoides sp. nov. Province (Zinsmeister 1979). The only unequivocal Fig. 1J, N, Q, T Weddellian taxa present are Lahillia and Neilo (Australoneilo) which presumably had a circum¬ Description. Shell of small size (4-5 mm), ovate, polar distribution. Other characteristic Weddellian strongly inequilateral, equivalve, moderately in¬ taxa such as aporrhaids and struthiolariids are flated, opisthogyrate, umbo situated about V4 to not present. !/5 from posterior end, valves slightly flattened to This comparative isolation of the Pebble Point depressed on posterior flank. Lunule very narrow, fauna can be explained by the disposition of the barely developed. Escutcheon very narrow. Sculp¬ Australian continent vis-a-vis Antarctica. Accepting ture of 21 to 39 fine, sharp, commarginal ribs, the scenario as depicted by Frakes et al. (1987, slightly narrower than interspaces and on some Figs 8-13) and Veevers et al. (1991, Figs 6-8), it specimens with a thin anastomosing riblet between would seem that a narrow east-west seaway open some ribs. End of ribs at anterior margin against to the west, but restricted or blocked in the east escutcheon somewhat thicker. Inter-rib spaces with by the South Tasman Rise, existed between Aus¬ fine, close spaced, radial costae. Sculpture begins tralia and Antarctica from Cenomanian times about 1 mm from umbo; anterior to this valve through into the Paleocene. Circulation of water is smooth. Muscle scars subcircular. Hinge with and hence migration or transport of larvae from 7 posterior and 13 anterior teeth. Resilifer directed the east would have been limited, thus preventing forwards, not projecting. Internal valve margin easy migration of taxa from the New Zealand with fine denticulations. region and the Antarctic Peninsula area. Most of Dimensions the taxa present were representatives of cosmo¬ Holotype P142956 L 5.1 H 4.1 T 3.0 (pr) politan groups, whose larvae would have been Paratype P142957 4.2 3.5 pelagic and long-lived, allowing wide dispersal. The fauna of the Maastrichtian Miria Formation Type material. Holotype PI42956, collected T. A. Dar¬ is also dominated by cosmopolitan generic taxa ragh, 17 February 1981; Paratype P142957, collected T. A. Darragh, 24 November 1992. (Darragh & Kendrick 1991; Darragh & Kendrick 1994) suggesting isolation of the Australian plate Type locality. PL3003. at that time. Apart from Eotrigonia, endemic Occurrence and material. PL3003 (27 specimens), Australian bivalve taxa had not evolved by Paleo¬ PL3004 (1 specimen). cene time and it was not until the Late Eocene that endemic elements developed. By this time the fauna Remarks. There is nothing quite like this taxon had also received an influx of new immigrants from in the Australian Eocene, though species which may the Tethyan and New Zealand regions and the basic possibly belong in the genus occur in the Oligocene PALEOCENE BIVALVES FROM THE PEBBLE POINT FORMATION 77 and Miocene. The genus has a cosmopolitan dis¬ Remarks. One specimen is a pair with a counter¬ tribution and is known from the Paleocene of sunk gastropod drill hole in the right valve. Europe, Asia and North America. There is nothing This species bears a very close resemblance to like it recorded from the early Tertiary of New Comitileda brachyryncha Maxwell, Eocene, New Zealand or the Antarctic. Zealand and also to C. praelonga Tate, Oligocenc There is possibly another species of nuculid to Miocene, Australia. The latter is more rostrate, present represented by one specimen with a smooth slenderer and more pointed at the posterior end, valve surface and denticulate internal ventral mar¬ but the differences are slight. It is more tumid than gin. It is triangular in shape rather than oval. Also C. miliacea but is not as elongate and the uinbo present are 16 very small (0.8-1 mm) specimens is not so opisthogyral. Leda rhamphidia Cossmann, that are thick shelled, tumid and triangular with Paleocene, Belgium is somewhat similar in shape a smooth external valve surface and smooth to C. miliacea. internal ventral margin. It is not clear if these specimens are juveniles of the smooth species or Ledina Dali, 1898 represent yet another species of nuculid, possibly Type species. Leda smirna Dali, 1898 (= Leda eborea an Austronucula. Conrad, 1860 non Conrad, 1846), Eocene, United States of America. Family Nuculanidae Comitileda Iredale, 1924 Ledina paucigradata (Singleton, 1943) Type species. Leda miliacea Hedley, 1902, Recent, New Fig. 1H-I, O-P, R-S, U-V South Wales. Nuculana paucigradata Singleton, 1943: 268, pi. 12, Until a proper revision of the small rostrate fig. la, b. nuculanids is undertaken, I follow Maxwell (1992) Description. Shell solid of medium to large size in using this genus rather than Ledina to which for genus (10-14 mm), elongate-ovate, posteriorly Australian species have been previously assigned. rostrate, equivalve, moderately inflated, umbones The genus occurs in New Zealand from Middle low, situated at about V3 distance from anterior Eocene to Recent and in Australia from Paleocene border. Anterior dorsal margin straight, merging to Recent. into the strongly convex anterior margin; ventral margin regularly and gently curved, abruptly Comitileda sp. cf. C. brachyryncha Maxwell, 1992 merging into posterior margin; posterior margin Fig. 1K-M short, in some specimens rounded to blunt point; posterior ventral margin slightly convex, abruptly Description. Shell small (2-3 mm), ovate, almost truncated by posterior margin. equilateral, somewhat tumid, slightly rostrate at Surface of valves sculptured with fine growth posterior end. Umbo central, projecting slightly, striae only. very slightly opisthogyral. Anterior dorsal margin Hinge with 10-14 anterior teeth, chevron shaped, gently convex; anterior margin strongly convex, pointed toward umbo, becoming weaker toward merging into convex ventral margin; ventral margin umbo; 19-23 posterior chevron shaped teeth, gently convex, concave where it merges with the becoming straighter and vertically aligned toward posterior margin; posterior dorsal margin straight; umbo. Small triangular resilifer between anterior posterior margin short, strongly convex. Surface and posterior tooth series. of valve smooth except for growth ridges. Hinge Anterior muscle scar laterally elongated; poster¬ with 10 posterior and 8 anterior chevron-shaped ior scar vertically elongate. Pallial sinus shallow, teeth, apex directed towards umbo. Muscle scars wide, usually not visible. Internal margins of valves subequal, barely visible; pallial line with shallow smooth. rounded sinus. Internal valve margin smooth. Dimensions Dimensions Holotype PI27990 L 11 H 6 T 2 Figured specimen P142863 L 2.7 H 1.9 Figured specimen PI42961 14 7 2.3 LV Figured specimen P143862 2.2 1.4 Figured specimen PI42962 12 7 2.3 RV Figured material. Figured specimen PI42863, collected Figured specimen P142960 11 6 4.5 Pair T. A. Darragh, 8 March 1977; Figured specimen PI42862, Figured specimen PI42963 12 6 6.6 Pair collected T. A. Darragh, 22 November 1993. Types. Holotype PI27990 (MUGD 1868), left valve, Occurrence and material. PL3003 (11 specimens). collected G. Baker, January 1942. The holotype has 78 THOMAS A. DARRAGH Fig. 1. A-G, Neilo (Australonei/o) cu/trata sp. nov. A-B, NMV P142861, paratype, PL3003, x 1.8. C-D, NMV P142859, paratype, PL3003, xl.8. E, G, NMV P142858, holotype, PL3003, Xl.5. F, NMV P142860, paratype, PL3003, x3.5. H-I, O-P, R-S, U-V, Ledina paucigradata (Singleton). H-l, NMV P127990, holotype, second point NW of Pebble Point, x3.5. O, NMV P142961, PL3003, x3.5. P, NMV P142960, PL3003, x3.7. R-S, U-V, NMV P142963, pair, PL3003, X3.75. J, N, Q, T, Lamellinucida pyrenoides sp. nov. J, NMV P142957, paratype, PL3003, x6.2. Q, NMV P142957, x8.1. N, NMV P142956, holotype, PL3003, x6.1. T, NMV P142956, holotype, x9.6. K-M, Comitileda cf. C. brachyryncha Maxwell. K, NMV P142862, PL3003, 13. L-M, PI42863, PL3003, x8.1. PALEOCENE BIVALVES FROM THE PEBBLE POINT FORMATION 79 approximately one millimetre broken off the posterior posteriorly. Umbo small, slightly projecting, ortho- end. Figured specimens, PI42960, PI42961, PI42962, gyral, situated about V valve length from anterior 3 collected T. A. Darragh, 8 March 1977; Figured specimen end. Anterior margin somewhat sharply rounded; P142963, collected T. A. Darragh, 27 November 1972. anterior dorsal margin concave; posterior dorsal Type locality. Coastal cliffs 2V2 miles south-east of margin concave, abruptly truncated by posterior Princetown, Victoria, second point north-west of Pebble margin; ventral margin long, gently convex. Point (= PL 3004). Posterior umbonal ridge ill defined. Occurrence and material. PL3001 (14 specimens), Lunule very narrow and weak. Escutcheon PL3003 (240 specimens), PL3004 (34 specimens). narrow, extending to posterior margin, sharply defined by ridge. One or two shorter ridges within Remarks. This is one of the most common mol¬ escutcheon. luscs in the fauna. Paired valves are very uncom¬ Sculpture consisting of to 14 widely spaced, 8 mon. L. paucigradata is very similar in overall somewhat irregular, thin, commarginal riblets features to the New Zealand Paleocene L. taioma extending to about 2.5-3 mm from beak, present (Finlay & Marwick 1937), but is more elongate, on central flank but not present on posterior or the umbo is not so centrally situated and the anterior flanks. Remainder of valve sculptured with anterior dorsal margin is straight rather than growth increments only. concave as in L. taioma. Hinge with chevron shaped teeth with apices Compared with the type species of the genus, directed toward umbo, becoming thinner and L. smirna Dali (Gardner 1933), paucigradata is straightening toward beak and meeting under it. more elongate and not so equilateral. Both L. 15 to 19 anterior teeth and 22 to 29 posterior teeth. fresnoensis (Dickerson) and L. duttonae (Vokes) No resilifer. (Paleocene and Eocene of California) have better Pallial sinus wide, moderately deep, extending developed lunules and escutcheons (Moore 1983). about halfway between umbo and posterior border, Darragh (1985) recorded L. paucigradata from sloping gently ventrally. Muscle scars barely visible, the Rivernook Member of the Dilwyn Formation. small, oval; anterior elongated dorso-ventrally; Collection of better preserved material shows that posterior elongated laterally. Internal valve margin the determination was in error. smooth. Apart from the occurrence here, the genus is Dimensions known only from the Paleocene to Eocene of New Holotype P142858 L 21 H 11 T 3.5 Zealand and North America. Paratype PI42859 18 9 3 Paratype P142861 17 9 3.5 Type material. Holotype PI42858, left valve; Paratype P142859, right valve, collected T. A. Darragh, 27 Nov¬ Neilo (Australoneilo) Zinsmeister 1984 ember 1977; Paratype P142861, right valve, collected Type species. Australoneilo rossi Zinsmeister, 1984, T. A. Darragh, 13 November 1984. Late Eocene, Antarctica. Type locality. PL3003. Zinsmeister (1984) distinguished Australoneilo Occurrence and material. PL 3001 (6 specimens); from Neilo by the absence of commarginal ribbing PL 3003 (14 specimens); PL3176 (3 specimens); PL3177 (1 specimen). 2125-2131 feet, Kaladbro 2 bore (1 speci¬ and by it having a poorly developed rostrum. These men); Mersey Valley Oil Co., 1926; Mumbannar no. 1, differences are slight, particularly as some species 1492-1502 feet, 37°5'37"S,14I°03'19"E, 4 km NE of of Neilo have obsolescent ribbing, so subgeneric Mumbannar (2 specimens). status seems appropriate. Australoneilo may be distinguished by its more prominently curved rather Remarks. In outline this species is very close to than almost straight ventral margin and by the lack the type species, N. (A.) rossi, but is about half of a prominent umbo to posterior ventral margin the size, slightly narrower and more elongate and ridge. Neilo also has a prominently rectangular has riblets on the umbo. N. (A.) gracilis (Wilckens truncated posterior margin. 1907), Late Cretaceous-Paleocene, Southern Pata¬ gonia and Seymour Island and N. (A), casei Zins¬ Neilo (Australoneilo) cultrata sp. nov. meister & Macellari 1988, Paleocene, Seymour Island both lack the fine umbonal ribs of N. (A.) Fig. 1A-G cultrata and are not so elongate. Description. Shell of small size for subgenus The subgenus was previously known only from (18-21 mm), narrow, elongate, subquadrangular, the Late Cretaceous, Paleocene and Eocene of moderately swollen medially and tapering gently Antarctica and South America. 80 THOMAS A. DARRAGH jymz* ¥ - ; • * w ft/Uit'Tri*¥'* ?fr>y3 Fig. 2. A-G, Cucullaeapsephea Singleton. A-B, NMV P142865, PL3004, x 1.2. C, E, NMV P127953, holotype second point NW of Pebble Point, xl. D, F, NMV P142866, PL3004, xl.2. G, NMV P127954, paratype’ second point NW of Pebble Point, xl.