Infaunal Suspension Feeders Research Articles

Early Cretaceous bivalves of the Romualdo Formation, Araripe Basin, northeastern Brazil

The fossil-rich Romualdo Formation (late Aptian/early Albian), Araripe Basin, northeastern Brazil, contains world-renowned Fossillagerstätten characterized by exceptionally preserved fossils. Macroinvertebrates in this formation are primarily represented by mollusks, echinoids, and decapod crustaceans. Mollusk shells are abundant in certain stratigraphic intervals, forming coquinas or shell pavements. Despite recent advances in our understanding of the taxonomy of certain groups, comprehensive taxonomic studies are lacking for almost the entire bivalve fauna. Therefore, a detailed taxonomic analysis is presented here. The described bivalves include four new genera (Araripenomia, Ciceromya, Inversatella, Australoeocallista), and six new species (Araripenomia infirma, Inversatella cearensis, Ciceromya edentulosa, Australoeocallista juazeiroi, Legumen kaririense, and Corbulomima delicata), in addition to Musculus maroimensis, Crassatella maroimensis, “Myrtea” sp. and “Tellina” sp. This bivalve fauna mainly consists of cosmopolitan and endemic brackish/marine genera, with Tethyan affinities. The fauna is not homogeneously distributed in the sedimentary succession of the Romualdo Formation, but is constrained to the third order highstand systems tract. Bivalves recorded from muddy facies are strongly dominated by infaunal and semi-infaunal suspension feeders. Assemblages of the sand-dominated facies, with dense shell accumulations of semi-infaunal to epifaunal byssate and infaunal suspension feeders, were formed under shallow, higher energy conditions. Despite the degree of generic endemicity, the mytilids, anomiids, crassateliids, astartids, tellinids, and corbulids are related to the bivalve fauna of the Early Cretaceous Riachuelo Formation of the Sergipe-Alagoas Basin, as previously demonstrated for the bakevelliids and echinoids. Indeed, the Romualdo bivalve fauna is, in part, a modified and impoverished brackish/marine fauna of the Riachuelo Formation.

Changes in bivalve assemblages at the onset of the OAE2 event in the Peri-Tethyan area (Bohemian Cretaceous Basin)

The Ocean Anoxic Event (OAE2) at the Cenomanian-Turonian boundary presents a unique record of gradual global warming and its effects on benthic organisms. The present research considers a palaeoecological, systematical and statistical evaluation of bivalve assemblages from the Pecínov Member in the Bohemian Cretaceous Basin. The well-exposed succession of Cenomanian through lower Turonian strata contains one of the most complex records of the OAE2 in central Europe. In total, 392 specimens have been studied and assigned to 24 genera within 21 families and 9 orders. The bivalve association prior to the positive shift of the δ13Corg (peak “a” sensu global carbon curve; lower part of the Metoicoceras geslinianum Zone) is strongly dominated by infaunal suspension feeders, followed by semi-infaunal suspension feeders. The near-absence of free-living epifaunal bivalves may be linked to a very fine, muddy substrate and water turbidity, a limiting factor for many epifaunal species. Infaunal deposit feeders are also present but comparatively rare, indicating a nutrient-rich environment with energy levels sufficiently high to keep organic matter in suspension. The Cucullaea glabra – Pseudoptera anomala assemblage of this level is considered to have formed during normal, shallow (15–20 m, supported by abundant material of Pinna) marine conditions. The association inhabiting the area above this level (upper part of the M. geslinianum Zone, S. gracile/E. septemseriatum Subzone) is characterized by the Panopea gurgitis – Rhynchostreon suborbiculatum assemblage suggesting considerably shallower depths and higher energy. Clusters of Modiolus and small oysters characterize the upper parts directly prior to the prominent positive δ13Corg peak “b” (the major peak of OAE2 CIE; ? base/lower part of the N. juddii Zone). No benthic fauna occurs above this level.

Middle Miocene serial killers: Drilled gastropods from the south-western margin of the Central Paratethys, Croatia

This paper focuses on traces of drilling predation in the middle Miocene gastropod assemblage of the Zaprešić Brijeg locality, Croatia, which provides further insight into the palaeoecology of the south-western margin of the Pannonian Basin System during the Badenian. The analyzed gastropod shells were collected in the first half of the 20th century, and are housed in the Croatian Natural History Museum (CNHM) in Zagreb. The CNHM Zaprešić Brijeg collections contain 11063 gastropod shells, of which 1024 have been identified as drilled (9.3% of the sample), with 633 successfully drilled, 113 unsuccessfully drilled, and 278 multiply drilled shells. The most represented families are Potamididae, Nassariidae, Clavatulidae, Turritellidae, Cerithiidae, Muricidae and Naticidae. The gastropod families Naticidae and Muricidae are recognized as the probable predators based on the shape of the drill holes. Middle Miocene (Badenian) gastropods drilling frequency at Zaprešić Brijeg is 5.72%, which is lower than the recorded Badenian gastropods drilling frequency in the Central Paratethys, while the overall gastropod prey effectiveness from the studied locality (15.15%) is higher than the average of the neighbouring Badenian localities in the Central Paratethys. Among the most represented gastropods at this locality, the highest drilling frequency occurs in the infaunal suspension feeders Turritellidae (14.45%), which mostly show traces of the naticid drilling.

TRACING ORIGIN AND COLLAPSE OF HOLOCENE BENTHIC BASELINE COMMUNITIES IN THE NORTHERN ADRIATIC SEA

The shallow northern Adriatic Sea has a long history of anthropogenic impacts that reaches back many centuries. While the effects of eutrophication, overfishing, pollution, and trawling over recent decades have been extensively studied, the major ecological turnovers during the Holocene as a whole remain poorly explored. In this study, we reconstruct ecological baselines defining benthic ecosystem composition prior to major anthropogenic changes at four stations characterized by low sedimentation and millennial-scale time averaging of molluscan assemblages. We discriminate between natural and anthropogenic drivers based on (1) stratigraphic changes in the composition of molluscan communities observed in sediment cores and (2) changes in concentrations of heavy metals, pollutants, and organic enrichment. The four 1.5-m long sediment cores reach back to the Pleistocene–Holocene boundary, allowing for a stratigraphic distinction of the major sea-level phases of the Holocene. During the transgressive phase and maximum flooding, sea-level and establishment of the modern circulation pattern determined the development of benthic communities in shallow-water, vegetated habitats with epifaunal biostromes and, in deeper waters, with bryozoan meadows. After sea-level stabilization, the composition of these baseline communities remained relatively uniform and started to change markedly only with the intensification of human impacts in the late highstand, leading to a dominance of infauna and a decline of epifauna at all sites. This profound ecological change reduced species richness, increased the abundance of infaunal suspension feeders, and led to a decline of grazers and deposit feeders. We suggest that modern soft-bottom benthic communities in the northern Adriatic Sea today do not show the high geographic heterogeneity in composition characteristic of benthos prior to anthropogenic influences.

Molluscan benthic communities at Brijuni Islands (northern Adriatic Sea) shaped by Holocene sea-level rise and recent human eutrophication and pollution.

The effects of and the interplay between natural and anthropogenic influences on the composition of benthic communities over long time spans are poorly understood. Based on a 160-cm-long sediment core collected at 44 m water depth in the NE Adriatic Sea (Brijuni Islands, Croatia), we document changes in molluscan communities since the Holocene transgression ~11,000 years ago and assess how they were shaped by environmental changes. We find that (1) a transgressive lag deposit with a mixture of terrestrial and marine species contains abundant seagrass-associated gastropods and epifaunal suspension-feeding bivalves, (2) the maximum-flooding phase captures the establishment of epifaunal bivalve-dominated biostromes in the photic zone, and (3) the highstand phase is characterized by increasing infaunal suspension feeders and declining seagrass-dwellers in bryozoan-molluscan muddy sands. Changes in the community composition between the transgressive and the highstand phase can be explained by rising sea level, reduced light penetration, and increase in turbidity, as documented by the gradual up-core shift from coarse molluscan skeletal gravel with seagrass-associated molluscs to bryozoan sandy muds. In the uppermost 20 cm (median age <200 years), however, epifaunal and grazing species decline and deposit-feeding and chemosymbiotic species increase in abundance. These changes concur with rising concentrations of nitrogen and organic pollutants due to the impact of eutrophication, pollution, and trawling in the 20th century. The late highstand benthic assemblages with abundant bryozoans, high molluscan diversity, and abundance of soft-bottom epi- and infaunal filter feeders and herbivores represent the circalittoral baseline community largely unaffected by anthropogenic impacts.

Albian infaunal Pholadomyida (Cretaceous Bivalvia), Comanchean Carbonate Shelf, Texas

AbstractSpecies of the megaorder Poromyata, although common and relatively diverse in Albian–lower Cenomanian Comanchean strata in Texas and northern Mexico, have been neglected as biostratigraphic markers and paleoecological indicators. Since 1852, more than a dozen species have been identified asHomomyaAgassiz, order Pholadomyida, superfamily Pholadomyoidea orPleuromyaAgassiz, order Pholadida, superfamily Pleuromyoidea. Because valve morphologies of the two genera are similar in many ways, casts are difficult to separate. Statistical analysis of key morphological properties objectively defines species concepts and assesses synonymies. Eight species are retained inHomomya; four are synonymized with these. Two species are provisionally retained in “Homomya” although they differ significantly. One species is reassigned toLiopistha (Sergipemya) alta(Roemer, 1852).Pleuromya henselli(Hill, 1893) is reassigned toPanopea.Homomyid species range from upper Aptian to lower Cenomanian of the Comanchean Series in Texas and Mexico. Their ranges vary in duration from one million years up to eight million years. These infaunal suspension feeders occupied calcareous mud and carbonate shelf substrates. Two sets of species are distinct morphotypes: a smaller-sized set ofH. knowltoniHill, 1895;H. tarrantensisPerkins, 1961;H. tlahualiloensisPerkins, 1961; andH. kellumiPerkins, 1961 and a larger-sized set ofH. cymbiformisPerkins, 1961;H. austinensisShattuck, 1903;H. vulgarisShattuck, 1903;H. budaensisWhitney, 1911; andH. auroraensisPerkins, 1961. Two end-member morphotypes are represented by the “streamlined”Homomya knowltoni, which is an elongate, slightly inflated form with a relatively high umbo, and the cylindricalHomomya budaensis, which is a very elongate, tubular, inflated form with a very low umbo.

Taxonomic and ecological variations of Permian-Triassic transitional bivalve communities from the littoral clastic facies in southwestern China

Immediately after the latest Permian mass extinction, bivalve faunas colonized the Permian-Triassic Transitional Beds (PTTB), especially in littoral clastic facies of South China. The Permian-Triassic (P-Tr) transitional bivalve fauna is composed of holdovers, long-term survivors and newly evolved taxa, and characterized by moderate diversity and high dominance. However, the taxonomy and ecology of this bivalve fauna of littoral clastic facies have not been well understood, especially in comparison with offshore marine records. This paper presents a study on a P-Tr transitional bivalve fauna from five sections of littoral clastic facies in southwestern China, and as such it contributes to a better knowledge of the ecological processes of benthic communities during the P-Tr transition. In total, 20 species in 13 genera of bivalves are identified from the PTTB in the lower part of the Kayitou Formation and the basal part of the Feixianguan Formation of the five sections. Cluster analysis suggests that the transitional bivalve fauna could be further divided into two successive communities (early and late communities), and each is composed of five assemblages. Promyalina–Neoschizodus community (early community) is characterized by presence of holdover taxa, high taxonomic diversity and evenness, and more abundant shallow infaunal suspension feeders. In Pteria community (late community), taxonomic diversity and evenness are much lower, and stationary epifaunal suspension feeders boost at the expense of shallow infaunal suspension feeders compared with the Promyalina–Neoschizodus community. Furthermore, the Promyalina–Neoschizodus community shows a clear spatial variation along environmental gradient from brackish lagoon to shallow marine settings, while the Pteria community is more uniform and homogeneous laterally. The Promyalina–Neoschizodus community in the studied region is of latest Permian age while the Pteria community should belong to the earliest Triassic. Consequently, a significant taxonomical and ecological turnover of bivalve communities occurred between the Promyalina–Neoschizodus community and the Pteria community during the extinction interval in southwestern China.

Late Paleocene‐middle Eocene benthic foraminifera on a Pacific seamount (Allison Guyot, ODP Site 865): Greenhouse climate and superimposed hyperthermal events

AbstractWe investigated the response of late Paleocene‐middle Eocene (~60–37.5 Ma) benthic foraminiferal assemblages to long‐term climate change and hyperthermal events including the Paleocene‐Eocene Thermal Maximum (PETM) at Ocean Drilling Program (ODP) Site 865 on Allison Guyot, a seamount in the Mid‐Pacific Mountains. Seamounts are isolated deep‐sea environments where enhanced current systems interrupt bentho‐pelagic coupling, and fossil assemblages from such settings have been little evaluated. Assemblages at Site 865 are diverse and dominated by cylindrical calcareous taxa with complex apertures, an extinct group which probably lived infaunally. Dominance of an infaunal morphogroup is unexpected in a highly oligotrophic setting, but these forms may have been shallow infaunal suspension feeders, which were ecologically successful on the current‐swept seamount. The magnitude of the PETM extinction at Site 865 was similar to other sites globally, but lower diversity postextinction faunas at this location were affected by ocean acidification as well as changes in current regime, which might have led to increased nutrient supply through trophic focusing. A minor hyperthermal saw less severe effects of changes in current regime, with no evidence for carbonate dissolution. Although the relative abundance of infaunal benthic foraminifera has been used as a proxy for surface productivity through bentho‐pelagic coupling, we argue that this proxy can be used only in the absence of changes in carbonate saturation and current‐driven biophysical linking.

Substrate control of benthos in a Middle Cambrian near-shore, epeiric palaeoenvironmental setting

Late Middle Cambrian Mail Change Limestone, a thin (< 30 m) lime mudstone unit of the epeiric Middle and Late Cambrian Georgina Basin, Australia is unusually rich in epifaunal linguliform brachiopods, especially acrotretids. It is the only unit of this abundantly fossiliferous Cambrian basinal succession where the representation of this group is more prolific than that of trilobites. The diminutive size of acrotretids, generally less than 3 mm in shell diameter in the case of common taxa from the Mail Change Limestone, raises questions of how an epizoic lifestyle was achieved on muddy substrates. Facies analysis indicates that lime mud substrates associated with deposition of the Mail Change Limestone included microbial firm-ground which developed in upper shoreface settings, and ephemeral evaporate horizons of supratidal or high intertidal association, during the shallow-water phases of repeating parasequence cycles. Lime muds of shoreface association are brachiopod-rich, suggesting that firm-ground substrates were favoured attachment sites for populations of anchoring epizoic acrotretids. The conical shell form typical of this group evolved in part to minimize current drag, reducing stress on pedicle attachment, and in part to induce turbulence at the shell gape to facilitate feeding. The high incidence of undamaged acrotretid valves, representing a spectrum of growth stages, obtained from the Mail Change Limestone suggests that failure of pedicle attachment was a major contributor to mortality in this group. Firm-ground was also characterised by ubiquitous fine-scale, Planolites-like, open burrows which housed substantial populations of wormlike suspension feeders (?polychaetes) which also took advantage of firm-ground substrates. Near-shore substrates were also host to suspension feeding Lingulella and Protospongia and a deposit feeder responsible for Thalassinoides ichnofossils. Substrates associated with deposition of the Mail Change Limestone were unfavorable to colonization by vagile, seafloor feeding ptychopariid trilobites which are poorly represented in the unit. In contrast, agnostid trilobites of nektonic habit were less limited by trophic opportunities and are more commonly represented. Diverse agnostids ranged into very shallow marine, shoreface, environments represented by the Mail Change Limestone. The association of abundant epifaunal linguliforms and infaunal suspension feeders with firm-ground suggests that substrate stability strongly influenced the nature and biomass of Middle Cambrian sessile benthos. Evolutionary strategies among sessile benthos to take full advantage of shallow marine level bottom environments were not realised until the Ordovician biodiversity event.

Modern bivalve shell assemblages on three atolls offshore Belize (Central America, Caribbean Sea)

The Belize atolls—Glovers Reef, Lighthouse Reef and Turneffe Islands—show differences in geomorphology, lagoonal depth, bottom sediment, growth of mangroves and sea-grass, exposure to waves and currents as well as in their sedimentation rates and their age. Bivalve shell assemblages in lagoonal areas reflect these geomorphological differences. On each atoll, 32 to 44 recent sediment samples were taken (total number of samples 111) and bivalve shells subsequently identified. The resulting database (32,122 bivalve shells in total) was analysed using Q-mode cluster analyses. Both the distribution of species characteristic of different lagoonal habitats and the distribution of bivalves with different life and feeding habits were investigated. Epifaunal suspension feeders were found particularly on hard-bottom along the reef-crests or clinging to mangrove roots. Infaunal suspension feeders show a more diverse distribution. Deeper lagoonal parts and areas with mangrove growth are often inhabited by chemosymbiont-carrying bivalves, indicating locations of reduced sediment. Deep burrowing detritus feeders are very abundant in shallow-water areas with moderate to high water agitation and were seldom found in Halimeda-rich sediments.

LINGULIDE BRACHIOPODS AND THE TRACE FOSSIL LINGULICHNUS FROM THE TRIASSIC OF WESTERN CANADA: IMPLICATIONS FOR FAUNAL RECOVERY AFTER THE END-PERMIAN MASS EXTINCTION

Abstract The environmental distribution of lingulide brachiopods in western Canadian Triassic marine successions, their relationship with other infaunal organisms occupying the same ecospace, and their role in the aftermath of the Permian-Triassic extinction event is summarized. Western Canada is an ideal location to assess lingulide distribution patterns as upper Paleozoic and lower Mesozoic strata are extensively exposed, and lingulides (cf. Lingularia Biernat and Emig) and the trace fossil Lingulichnus Hakes are both common. A distribution comparison of in situ lingulides and Lingulichnus Hakes with concordantly emplaced lingulide shells and shell beds shows clearly that the latter is a poor indicator of true environmental distribution of these infaunal suspension feeders. Lingulides are rare in uppermost Paleozoic strata in the study area. Most occurrences consist of isolated valves or abraded material in erosional lags. Lingulides remain minor components of infaunal communities during the earliest Tr...

Plant–herbivore interactions in seagrass meadows

During the past two decades we have gained much insight into the factors that regulate the productivity of seagrass dominated ecosystems, especially those at low latitudes. Here, we review and reassess the importance of plant–herbivore interactions in seagrass meadows, focusing on recent studies that have examined: 1) grazing on live seagrass leaves; 2) consumption of epiphytic algae growing on seagrass leaves; and 3) consumption of planktonic algae from the waters surrounding seagrass meadows. The major conclusion is that, in contrast to what has been reported in much of the literature on food webs in seagrass meadows, a diverse grazing pathway continues to represent an important conduit for the transfer of energy from the primary producers to higher order consumers. This remains true, although in many areas consumption of seagrasses is reduced in an historical context, owing to the overharvesting of many large species of herbivorous waterfowl, turtles and mammals. We also summarize our view of the important gaps in understanding the broadly defined topic of herbivory in seagrass-dominated ecosystems. We suggest that future studies should focus on: understanding the foraging strategies of seagrass herbivores; quantifying the impact of herbivory on seagrass demography, including effects on sexual reproduction, the fate of flowers, and the production of fruits and seeds; and documenting the commonness of compensatory responses to grazing. In addition, the role of chemical defenses in seagrass species remains inadequately investigated. Studies of the roles of nutritional content (as measured by C/N/P ratios) and chemical defenses are also fertile grounds for future studies of epiphytes and their grazers, as are additional experiments to quantify the relative roles of top-down and bottom-up factors as they determine algal growth and abundance. There is also a need to expand the geographical scope of studies of epiphyte–grazer interactions from cold temperate to sub-tropical and tropical waters. Suspension feeders also need to be studied more broadly, with additional experiments required to quantify their effects on water clarity and their ability to fertilize pore waters, and whether benefits from these activities balances the costs of shading and competition for space that can result from both epifaunal and infaunal suspension feeders.

Changes in Late Cretaceous–early Tertiary benthic marine assemblages: analyses from the North American coastal plain shallow shelf

The Mesozoic–Cenozoic transition is generally seen as a pivotal time in the evolution of benthic marine assemblages but the details of the timing and drivers of these changes are poorly known. The Atlantic and Gulf Coastal Plains of the United States contain assemblages preserved as original aragonitic and calcitic material in unconsolidated sediments. This makes coastal plain assemblages ideally suited to paleoecological analyses. Data derived from bulk samples of the Coffee Formation (lower/middle Campanian: Mississippi) as well as published faunal lists from comparable samples of the Severn (Maastrichtian: Maryland), Providence (Maastrichtian: Georgia and Alabama), Stone City (Eocene: Texas), and Gosport (Eocene: Alabama) Formations are used to assess changes in taxonomic diversity and ecomorphological group (life habit and trophic group) composition through this time interval.These analyses find a significant decrease in rarefied-sample species richness from the Campanian through the Eocene, but no change in evenness. With the notable exception of the Stone City Formation, increases in carnivore (neogastropod) richness and abundance occur before the Campanian. Epifaunal suspension-feeding species are a smaller proportion of the sample richness in Eocene samples than in Cretaceous samples. Decreased relative epifaunal suspension-feeder biomass but unchanged relative numbers of epifaunal suspension-feeder individuals suggests a relative decrease in epifaunal suspension-feeder size. Infaunal suspension feeders increase in richness and abundance through the interval. The proportion of drilled bivalves and gastropods does not change through the interval. Changes found in the structure of local shallow-shelf benthic assemblages from the Campanian through the Eocene are generally small relative to the variability between samples. Formation-level variation between assemblages is high relative to the magnitude of the temporal signal, emphasizing the need for investigators to include multiple formations per interval in tests of temporal trends.

An early Pennsylvanian waterhole deposit and its fossil biota in a dryland alluvial plain setting, Joggins, Nova Scotia

The terrestrial ecology of Pennsylvanian tropical wetlands is understood in detail, but coeval dryland ecosystems remain highly enigmatic. To fill this gap in our knowledge, a Pennsylvanian (Langsettian) continental red-bed succession was studied at the classic Joggins locality, Nova Scotia. These units represent the deposits of seasonally dry, alluvial plains traversed by anastomosed drainage networks. One channel complex informally known as the ‘Hebert beds’ (the focus of this study) contains an unusual fossil assemblage and is interpreted as an alluvial waterhole deposit that formed following drought-induced cessation of channel flow. Adpressed and charred fossil plant remains indicate that the alluvial plain surrounding the waterhole was covered by fire-prone cordaite vegetation, with hydrophilic lycopsids and sphenopsids restricted to waterlogged riparian niches. Gigantic unionoid freshwater bivalves, locally in life position, and occurring in large numbers in the waterhole, were probably infaunal suspension feeders during periods of fluvial activity, but aestivated in channel bottom muds when flow ceased. Abundant terrestrial gastropods found clustered around fossil plant detritus may have been deposit feeders scavenging dry portions of channel floors. Common partially articulated remains of small to medium-sized tetrapods possibly represent animals drawn to the waterhole during drought when surface water was scarce elsewhere. In terms of both sedimentology and biology, the Hebert beds alluvial complex bears a very close similarity to the seasonal drainages and waterholes of present-day central and northern Australia. This unique deposit sheds significant new light on the nature of Pennsylvanian dryland tropical ecology.

Selective extinction among Early Jurassic bivalves: A consequence of anoxia

Analyses of taxonomically standardized data sets demonstrate several statistically robust extinction patterns in Early Jurassic bivalve species from northwest Europe and the Andean basins of South America. In both regions, extinction intensities were significantly enhanced in late Pliensbachian and early Toarcian time as compared to all other time intervals. The same intervals (except for the early Toarcian of South America) also represent times of unusual extinction selectivity, with infaunal taxa suffering distinctly more than epifaunal forms. As infaunal suspension feeders are extremely rare components of Early Jurassic oxygen-controlled macrofaunas, these results are entirely compatible with sedimentological and geochemical data suggesting that widespread anoxia was a principal cause of the diversity crisis. Although many biotic traits that enhance survivorship during background times seem to be irrelevant during major mass extinctions, patterns of survivorship selectivity may provide more distinct clues to the causes of less severe mass extinctions.

The importance of fossil taxa in the knowledge of Neopterygian interrelationships

SUMMARY OF COMMUNICATIONS PALEONTOLOGICAL TOPICS AlexanderW.A.Kellner(Organizer) MODE OF LIFE OF THE MACROFOSSILS FROMTHE CABECAS FORMATION (DEVONIAN), PARNAIBABASIN, BRAZIL CleberF.daSilva 1 andDeusanaM.C.Machado 21 Estagiario do Laboratorio de Comunidades Paleozoicas, De-partamento de Ciencias Naturais, ECB, CCBS, UNI-RIO, Av.Pasteur 428, Urca, Rio de Janeiro – RJ. 2 Laboratorio de Comunidades Paleozoicas, Departamento deCiencias Naturais, ECB, CCBS, UNI-RIO, Av. Pasteur 428,Urca, Rio de Janeiro – RJ.Presented by DiogenesdeAlmeidaCampos The Cabecas Formation belongs to the CanindeGroup and corresponds to the Devonian depositional se-quence of the Parnaiba Basin. This unit is divided in twomembers, from base to top: Passagem and Oeiras. ThePassagem Member is of marine-deltaic origin and yieldedthe macrofossils studied here; the Oeiras Member is afos-siliferous and was deposited under fluvio-deltaic condi-tions. Fifteen taxa of the twenty-five known from thePassagem Member were found in the studied samples, asfollows: six brachiopods, six bivalves, one trilobite andone tentaculitid. Besides those, five additional ones arereported for the first time in this unit: two brachiopods(lingulid and Terebratulidae indet.), one inderminated bi-valve and two crinoids [Hexacrinites (?) sp. and Pen-tagonostipes (?) sp.]. These species fell under sevenmodes of life: (1) reclined epibenthic suspension feed-ers, represented by Pleurochonetes comstocki (Rathbun1874) and Mucrospirifer (?) pedroanus (Rathbun 1874);(2)attachedepibenthicsuspensionfeeders,representedbyPustulatia(?) curupira (Rathbun 1874), Mutationellinaeindet. D, Rhipidothyrididae sive Mutationellidae indet.B, Rhipidothyrididae sive Mutationellidae indet. D, Ter-ebratulidae indet., Hexacrinites (?) sp. and Pentagonos-tipes (?) sp.; (3) infaunal suspension feeders, representedby Grammysioidea lundi (Clarke 1899), Grammysioideasp. A and Tentaculites sp. (cf. T. eldregianus Rathbun1874); (4) semi-infaunal suspension feeders, representedby Spathella pimentana (Rathbun 1874); (5) infaunal de-positfeeders, representedbyCucullellatriquetra(Conrad1841), Nuculites (Nuculites) aff. N. (N) oblongatus (Con-rad 1841) and Palaeoneilo sp. A; (6) mobile epibenthicpredator, represented by Metacryphaeus meloi (Carvalhoet al. 1997); and (7) mobile epibenthic herbivore, repre-sented by Plectonotus derbyi (Clarke 1899). These habitsand their abundance agree with the previous suggestionthat the Cabecas Formation was deposited in a shallowmarine environment near the coast with moderated distur-bance from marine currents. — ( December 20, 2001 ).

Morphological variation among the appendicular bones of the Titanosauridae (Dinosauria: Sauropoda) from the Bauru Basin (upper Cretaceous) of Peirópolis (MG), Brazil

SUMMARY OF COMMUNICATIONS PALEONTOLOGICAL TOPICS AlexanderW.A.Kellner(Organizer) MODE OF LIFE OF THE MACROFOSSILS FROMTHE CABECAS FORMATION (DEVONIAN), PARNAIBABASIN, BRAZIL CleberF.daSilva 1 andDeusanaM.C.Machado 21 Estagiario do Laboratorio de Comunidades Paleozoicas, De-partamento de Ciencias Naturais, ECB, CCBS, UNI-RIO, Av.Pasteur 428, Urca, Rio de Janeiro – RJ. 2 Laboratorio de Comunidades Paleozoicas, Departamento deCiencias Naturais, ECB, CCBS, UNI-RIO, Av. Pasteur 428,Urca, Rio de Janeiro – RJ.Presented by DiogenesdeAlmeidaCampos The Cabecas Formation belongs to the CanindeGroup and corresponds to the Devonian depositional se-quence of the Parnaiba Basin. This unit is divided in twomembers, from base to top: Passagem and Oeiras. ThePassagem Member is of marine-deltaic origin and yieldedthe macrofossils studied here; the Oeiras Member is afos-siliferous and was deposited under fluvio-deltaic condi-tions. Fifteen taxa of the twenty-five known from thePassagem Member were found in the studied samples, asfollows: six brachiopods, six bivalves, one trilobite andone tentaculitid. Besides those, five additional ones arereported for the first time in this unit: two brachiopods(lingulid and Terebratulidae indet.), one inderminated bi-valve and two crinoids [Hexacrinites (?) sp. and Pen-tagonostipes (?) sp.]. These species fell under sevenmodes of life: (1) reclined epibenthic suspension feed-ers, represented by Pleurochonetes comstocki (Rathbun1874) and Mucrospirifer (?) pedroanus (Rathbun 1874);(2)attachedepibenthicsuspensionfeeders,representedbyPustulatia(?) curupira (Rathbun 1874), Mutationellinaeindet. D, Rhipidothyrididae sive Mutationellidae indet.B, Rhipidothyrididae sive Mutationellidae indet. D, Ter-ebratulidae indet., Hexacrinites (?) sp. and Pentagonos-tipes (?) sp.; (3) infaunal suspension feeders, representedby Grammysioidea lundi (Clarke 1899), Grammysioideasp. A and Tentaculites sp. (cf. T. eldregianus Rathbun1874); (4) semi-infaunal suspension feeders, representedby Spathella pimentana (Rathbun 1874); (5) infaunal de-positfeeders, representedbyCucullellatriquetra(Conrad1841), Nuculites (Nuculites) aff. N. (N) oblongatus (Con-rad 1841) and Palaeoneilo sp. A; (6) mobile epibenthicpredator, represented by Metacryphaeus meloi (Carvalhoet al. 1997); and (7) mobile epibenthic herbivore, repre-sented by Plectonotus derbyi (Clarke 1899). These habitsand their abundance agree with the previous suggestionthat the Cabecas Formation was deposited in a shallowmarine environment near the coast with moderated distur-bance from marine currents. — ( December 20, 2001 ).

On a fossil lobster (Decapoda, Malacostraca, Crustacea) from the Riachuelo Formation, Albian of the Sergipe Basin, Brazil

SUMMARY OF COMMUNICATIONS PALEONTOLOGICAL TOPICS AlexanderW.A.Kellner(Organizer) MODE OF LIFE OF THE MACROFOSSILS FROMTHE CABECAS FORMATION (DEVONIAN), PARNAIBABASIN, BRAZIL CleberF.daSilva 1 andDeusanaM.C.Machado 21 Estagiario do Laboratorio de Comunidades Paleozoicas, De-partamento de Ciencias Naturais, ECB, CCBS, UNI-RIO, Av.Pasteur 428, Urca, Rio de Janeiro – RJ. 2 Laboratorio de Comunidades Paleozoicas, Departamento deCiencias Naturais, ECB, CCBS, UNI-RIO, Av. Pasteur 428,Urca, Rio de Janeiro – RJ.Presented by DiogenesdeAlmeidaCampos The Cabecas Formation belongs to the CanindeGroup and corresponds to the Devonian depositional se-quence of the Parnaiba Basin. This unit is divided in twomembers, from base to top: Passagem and Oeiras. ThePassagem Member is of marine-deltaic origin and yieldedthe macrofossils studied here; the Oeiras Member is afos-siliferous and was deposited under fluvio-deltaic condi-tions. Fifteen taxa of the twenty-five known from thePassagem Member were found in the studied samples, asfollows: six brachiopods, six bivalves, one trilobite andone tentaculitid. Besides those, five additional ones arereported for the first time in this unit: two brachiopods(lingulid and Terebratulidae indet.), one inderminated bi-valve and two crinoids [Hexacrinites (?) sp. and Pen-tagonostipes (?) sp.]. These species fell under sevenmodes of life: (1) reclined epibenthic suspension feed-ers, represented by Pleurochonetes comstocki (Rathbun1874) and Mucrospirifer (?) pedroanus (Rathbun 1874);(2)attachedepibenthicsuspensionfeeders,representedbyPustulatia(?) curupira (Rathbun 1874), Mutationellinaeindet. D, Rhipidothyrididae sive Mutationellidae indet.B, Rhipidothyrididae sive Mutationellidae indet. D, Ter-ebratulidae indet., Hexacrinites (?) sp. and Pentagonos-tipes (?) sp.; (3) infaunal suspension feeders, representedby Grammysioidea lundi (Clarke 1899), Grammysioideasp. A and Tentaculites sp. (cf. T. eldregianus Rathbun1874); (4) semi-infaunal suspension feeders, representedby Spathella pimentana (Rathbun 1874); (5) infaunal de-positfeeders, representedbyCucullellatriquetra(Conrad1841), Nuculites (Nuculites) aff. N. (N) oblongatus (Con-rad 1841) and Palaeoneilo sp. A; (6) mobile epibenthicpredator, represented by Metacryphaeus meloi (Carvalhoet al. 1997); and (7) mobile epibenthic herbivore, repre-sented by Plectonotus derbyi (Clarke 1899). These habitsand their abundance agree with the previous suggestionthat the Cabecas Formation was deposited in a shallowmarine environment near the coast with moderated distur-bance from marine currents. — ( December 20, 2001 ).

DESCRIPTION AND PALEOBIOGEOGRAPHIC SIGNIFICANCE OF A RARE CENOMANIAN MOLLUSCAN FAUNULE FROM BATHURST ISLAND, NORTHERN AUSTRALIA

A middle Cenomanian faunule from the Moonkinu Formation of Bathurst Island in Northern Australia contains the best-preserved suite of benthic Mollusca known from the Cretaceous of the Australian region. Twenty-four species of bivalves, gastropods, and scaphopods, many exquisitely preserved with original aragonitic nacre, are recognized. Thirteen are new: Nucula s.l. meadinga n. sp. (Nuculidae), Nuculana bathurstensis n. sp. (Nuculanidae), Jupiteria? n. sp. A (Nuculanidae), Varicorbula cretaustrina n. sp. (Corbulidae), Vanikoropsis demipleurus n. sp. (Vanikoridae), Euspira n. sp. A (Naticidae), Amuletum praeturriformis n. sp. (Turridae), Granosolarium cretasteum n. sp. (Architectonicidae), Echinimathilda moonkinua n. sp. (Mathildidae), Acteon bathurstensis n. sp. (Acteonidae), Biplica antichthona n. sp. (Ringiculidae), Goniocylichna australocylindricata n. sp. (Cylichnidae), and Dentalium (Dentalium) n. sp. A (Dentaliidae). Nominal species of Nuculana, Grammatodon, Cylichna, and Laevidentalium also are present. The occurrence of ammonites, including taxa that occur in the type Cenomanian, securely establishes the fauna as middle Cenomanian (Acanthoceras rhotomagense Zone). The Moonkinu Formation and its faunule were deposited in a high-energy, shallow-shelfal setting, as part of a large-scale regressive cycle recognized as the Money Shoals Platform of northern Australia. The assemblage represents a parauthochthonous suite which experienced little or no post mortem transport. Epifaunal and infaunal suspension feeders (some 60 percent) dominate the bivalve fauna with a subordinate representation of deposit-feeding infaunal burrowers (some 40 percent). Nearly all of the gastopods were carnivores with the aporrhaid Latiala mountnorrisi (Skwarko), probably a deposit feeder, the only exception. The scaphopods were probably micro-carnivores. Concentrations of the ammonite Sciponoceras glaessneri are likely the result of mass kills in surface waters. The cosmopolitan nature of the Bathurst Island fauna at the genus-level reflects unrestricted oceanic circulation patterns and an equitable climate on a global scale during the Cenomanian. The retreat and disappearance of the Australian epicontinental sea at the close of the Albian coincided with reduced endemism in the molluscan faunas, after which time the continental shelves hosted a rich suite of cosmopolitan affinity. The high number of endemic species in the Moonkinu Formation probably represents an early stage of broad-scale genetic separation among Southern Hemisphere molluscan stocks, a trend that became increasingly pronounced through the Late Cretaceous. The new records of Varicorbula, Amuletum, Granosolarium, Echinimathilda, and Goniocylichna represent the oldest occurrences recorded for these genera and are suggestive of Southern Hemisphere origins.

Description and paleobiogeographic significance of a rare Cenomanian molluscan faunule from Bathurst Island, northern Australia

A middle Cenomanian faunule from the Moonkinu Formation of Bathurst Island in Northern Australia contains the best-preserved suite of benthic Mollusca known from the Cretaceous of the Australian region. Twenty-four species of bivalves, gastropods, and scaphopods, many exquisitely preserved with original aragonitic nacre, are recognized. Thirteen are new:Nuculas.l.meadingan. sp. (Nuculidae),Nuculana bathurstensisn. sp. (Nuculanidae),Jupiteria? n. sp. A (Nuculanidae),Varicorbula cretaustrinan. sp. (Corbulidae),Vanikoropsis demipleurusn. sp. (Vanikoridae),Euspiran. sp. A (Naticidae),Amuletum praeturriformisn. sp. (Turridae),Granosolarium cretasteumn. sp. (Architectonicidae),Echinimathilda moonkinuan. sp. (Mathildidae),Acteon bathurstensisn. sp. (Acteonidae),Biplica antichthonan. sp. (Ringiculidae),Goniocylichna australocylindricatan. sp. (Cylichnidae), andDentalium (Dentalium)n. sp. A (Dentaliidae). Nominal species ofNuculana, Grammatodon, Cylichna,andLaevidentaliumalso are present. The occurrence of ammonites, including taxa that occur in the type Cenomanian, securely establishes the fauna as middle Cenomanian (Acanthoceras rhotomagenseZone). The Moonkinu Formation and its faunule were deposited in a high-energy, shallow-shelfal setting, as part of a large-scale regressive cycle recognized as the Money Shoals Platform of northern Australia. The assemblage represents a parauthochthonous suite which experienced little or no post mortem transport. Epifaunal and infaunal suspension feeders (some 60 percent) dominate the bivalve fauna with a subordinate representation of deposit-feeding infaunal burrowers (some 40 percent). Nearly all of the gastopods were carnivores with the aporrhaidLatiala mountnorrisi(Skwarko), probably a deposit feeder, the only exception. The scaphopods were probably micro-carnivores. Concentrations of the ammoniteSciponoceras glaessneriare likely the result of mass kills in surface waters. The cosmopolitan nature of the Bathurst Island fauna at the genus-level reflects unrestricted oceanic circulation patterns and an equitable climate on a global scale during the Cenomanian. The retreat and disappearance of the Australian epicontinental sea at the close of the Albian coincided with reduced endemism in the molluscan faunas, after which time the continental shelves hosted a rich suite of cosmopolitan affinity. The high number of endemic species in the Moonkinu Formation probably represents an early stage of broad-scale genetic separation among Southern Hemisphere molluscan stocks, a trend that became increasingly pronounced through the Late Cretaceous. The new records ofVaricorbula, Amuletum, Granosolarium, Echinimathilda,andGoniocylichnarepresent the oldest occurrences recorded for these genera and are suggestive of Southern Hemisphere origins.