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Agglutinated foraminiferal assemblages from the Oligocene section of an exploration well drilled in the distal part of the Congo Fan are fully documented and interpreted for palaeoenvironment. A total of 65 ditch cutting samples were analysed at 10 m intervals, from 3630 to 4270 m below rotary table. An average of 170 specimens were extracted per sample, with over 100 species being documented and described using SEM and light photography. The results reveal the most taxonomically diverse deepsea Oligocene fauna yet described. Six assemblages have been defined and analysed with Correspondence and 'Morphogroup' Analysis. These are 1. Nothia robusta / Reticulophragmium Assemblage (4110-4270 m), 2. Nothia robusta / Scherochorella congoensis / Discammilloides sp. 1 Assemblage (4000-4100 m), 3. High diversity Reticulophragmium Assemblage (3870-3990 m), 4. Portatrochammina profunda Assemblage (3790-3860 m), 5. Nothia latissima Assemblage (3730-3780 m) and 6. Low abundance Assemblage (3630-3720 m). Palaeobathymetric estimates range from middle -lower bathyal based on comparison with living taxa and morphogroup distributions. These results extend the known stratigraphic range (last occurrences) of Reticulophragmium amp/eetens into the Oligocene in the Atlantic, and possibly also Paratrochamminoides gorayskii, Paratrochamminoides olszewskii, Trochamminoides aff. proteus, Trochamminoides subcoronatus, Haplophragmoides horridus and Haplophragmoides walteri, although reworking is documented with these species. Results also extend the known first occurrences of Recurvoides azuaensis, Spiropsammina primula, Cyclammina aff. orbicularis, Discamminoides sp. and Glaphyrammina americana into the Oligocene. Large scale variations within faunas are largely assigned to documente d variations in sand content, where higher proportions of sand generally coincide with reduced diversity and abundance along with a dominance of opportunistic species such as Nothia robusta, Nothia latissima and Ammodiscus latus. A major excursion in the infaunal morpho group, suspension-feeding morpho group and diversity and abundance within Assemblage 2 is termed the 'Scherochorella Event', and does not correlate with an increase in sand. This fauna is thought to be the result of lower oxygen conditions allowing the dominance of the low oxygen morphotype Scherochorella congoensis and the opportunistic species Nothia robusta. Deep-water circulation in the Atlantic at this time is generally thought to have been strong, and this event suggests that there may have been a temporary expansion of the oxygen minimum zone during the Late Oligocene, coinciding with increased benthic 8180 values, global cooling, and increased upwelling associated with a stronger polar front. The otherwise high diversity of the fauna in the well supports the interpretation of well-oxygenated conditions.
The development of benthic foraminiferal assemblages during the past 6,000 yrs was investigated in Holocene sediment cores from three carbonate platforms (Turneffe Islands, Lighthouse Reef, and Glovers Reef) of Belize, Central America. Foraminiferal assemblages and their diversity were determined in different time periods to identify their dependence on environmental factors, such as lagoonal age, lagoonal depth, water circulation, substrate, bottom-water temperature, and salinity. Geochemical proxies (δ18O and δ13C), obtained from the common larger foraminifer Archaias angulatus were used to estimate Holocene seasonal BW-temperatures and climate variabilities. A total of 51 samples were taken from 12 vibracores for taxonomic determination and 10 to 15 subsamples of 32 tests of Archaias angulatus were used for stable oxygen and carbon isotope analyses. Based on cluster analyses, seven benthic foraminiferal assemblages are distinguished during the Holocene. The three platforms exhibit characteristic differences in benthic foraminiferal fauna and diversity, which are controlled by their respective environments during the last 6,000 yrs. Turneffe Islands has four benthic foraminiferal assemblages, which are typical for restricted lagoons with fluctuating salinity. Lighthouse Reef is inhabited by two benthic foraminifera associations, which are characteristic of high water exchange with the surrounding ocean and clear waters. Glovers Reef is characterized by two benthic foraminiferal assemblages, which occur in deeper lagoons with slow water circulation. In general, during the Holocene, the highest mean diversity, evenness, and richness of benthic foraminifera were found in the Turneffe Islands and the lowest occurred at Glovers Reef. The foraminiferal faunas of the Lighthouse and Glovers Reefs had been in a “Diversification Stage” since 6,000 yrs, whereas the foraminiferal fauna of the Turneffe Islands reflects the development from a “Colonisation” (~4,000 yrs BP) to a “Diversification Stage” (~2,000 yrs to present time). Lagoonal depth, water circulation, substrate, and BW-temperature have higher influence on foraminiferal diversity as compared to lagoonal size and age. The negative correlation between diversity and lagoonal depth is based on differences in light intensity and substrate. In contrast to Lighthouse Reef, the Turneffe Islands and Glovers Reef show decreasing diversity of benthic foraminifera with increasing lagoon depth, due to finer sediment, turbid waters and/or dense mangrove growth, which reduce the light intensity and the number of species. Water Circulation also affected the benthic foraminifera modes of living and their diversity during the last 6,000 yrs. Increasing abundances of infaunal taxa refer to restricted circulation and/or lower oxygen conditions, as assumed for the Turneffe Islands and Glovers Reef. Increasing abundances of epifaunal foraminifera, as observed in the Lighthouse Reef indicate better circulation and/or higher oxygen conditions. Holocene BW-temperature reconstructions based on δ18O of single Archaias angulatus tests do not correspond to typical Holocene climate models of the Caribbean. In the Belize area, mean BW-temperature trends indicate local climate variations. A decrease of δ13C values during the last 1,000 yrs could be related to the “Suess Effect”. The seasonal BW-temperature variations within single large benthic foraminifera tests correspond to present-day temperature fluctuations in the lagoons, and indicate higher temperatures in Summer and Autumn and lower temperatures in Winter and Spring.
Presented herein is the first morphological analysis of turtle relationships to examine the monophyly of many turtle groups by using only single species as terminals and by integrating a large number of primitive fossil taxa. The data matrix consists of 136 osteological parsimony informative characters with 169 derived character states for 45 fossil and 22 living species of the clade TESTUDINATA. The results corroborate the monophyly of a large number of previously hypothesized clades, but refute the accepted hypothesis regarding the basal split of living turtles. In particular, the primitive turdes Proterochersis robusta, Kayentachelys aprix, Mongolochelys efremovi, Meiolania platyceps, and Kallokibotion bajazidi are removed from their current position as crown turtles and placed along the phylogenetic stem of this clade. The age of the turtle crown is thereby adjusted from the Late Triassic to the Late Jurassic, which is relevant to testing molecular clock hypotheses. This revised topology has important implications for the evolution of several character complexes, because it implies that the common ancestor of all living turtles must have had a partially braced brain case and a primitive trochlear mechanism. Other noteworthy conclusions include the tentative exclusion of protostegids from CHELONIOIDEA, the placement of Platysternon megacephalum outside of CHELYDRIDAE, and the tentative interpretation of Sandownia harrisi as a basal eucryptodire.
Glyptostrobus Endlicher is well represented in early Early Cretaceous to Pleistocene deposits in the middle to high latitudes of North America and Eurasia. Although the taxonomy and nomenclature of the genus is complicated, the fossil record indicates Glyptostrobus was represented by a small number of species. The genus first appears in Aptian age deposits from western Canada and Greenland, and achieved a wide distribution early in its evolutionary history. Exchange of Glyptostrobus between Asia and North America occurred across the Spitsbergen and Beringian corridors, which were functional about 110 and 100 million years ago, respectively The Late Cretaceous fossil record of Glyptostrobus shows that the genus had spread into Russia, China and the shores of the Turgai Strait. By the early Tertiary, Glyptostrobus was a prominent constituent of the polar broad-leaved deciduous forests. Paleocene age deposits across western Canada and the United States indicate the genus was present in great abundance in the lowland warm temperate and subtropical forests east of the Rocky Mountains. The broad distribution in North America and Russia during the Paleocene and Eocene indicates that Glyptostrobus grew and reproduced under a diverse range of climatic and environmental conditions, including the cold and unique lighting conditions of the polar latitudes. The presence of Glyptostrobus in Europe indicates the North Atlantic land bridges that extended between North America and Eurasia (Fennoscandia) and Europe during the early Tertiary were used. In Europe, extensive Glyptostrobus dominated swan1ps occupied the Central European Depression during the late Tertiary. Increasing global aridity and cooling, as well as landscape stabilization together with increasing competition for resources and habitat by representatives of the Pinaceae, seem to have forced the genus out of North America, Europe and most of Asia during the Miocene and Pliocene. In Japan, Glyptostrobus persisted until the early Pleistocene. After the early Pleistocene extinction in Japan, Glyptostrobus reappeared in southeastern China. Details of the taxonomic and biogeographic history of Glyptostrobus are examined.
Taphonomy and palaeoecology of Laetoli as well as Makuyuni, Arusha region in northern Tanzania
(2004)
This thesis is the result of the Hominid Corridor research Project in Tanzania since 1993 to 1995 that include Pliocene and Pleistocene localities. The localities under study include Laetoli and Manyara area in Arusha Region, northern Tanzania. The thesis has the following specific objectives: firstly, to identify taxa recovered from the studied assemblages; secondly, to underpin taphonomic history of the assemblages under study; thirdly, to elucidate further palaeoecological reconstruction of the assemblages; and finally, to examine surface fossil fauna modifications including agents of modifications either hominids or carnivores.
The Upper Laetolil Beds are dated at 3.5 million years ago (Ma) and the Ndolanya Beds are bracketed in age between 3.5 and 2.41 Ma. The Naibadad Beds, also from Laetoli area, are date to be between 2.2 to 2.1 Ma. The Naibadad Beds are correlated with the base of Bed I at Olduvai Gorge. There are so far no absolute dates for Manyara assemblages. Based on biostratigraphic correlation, the younger overlying unit, the Upper Manyara Beds are estimated to belong to Later Pleistocene and the Lower Manyara Beds are estimated to belong to Early Pleistocene. The Upper Manyara Beds are correlated to the age of Bed III at Olduvai Gorge, while the Lower Manyara Beds are interpreted to span the same contemporaneity with the upper part of Bed II at Olduvai Gorge.
At Laetoli localities, terrestrial mammals while localities from Manyara besides terrestrial mammals dominate fauna; they include aquatic species such as fish, crocodiles and hippopotamus. The main families recovered from Upper Laetolil Beds complement those already recovered from former research works by other workers. This is also true for the younger overlying stratigraphic horizon, the Upper Ndolanya Beds. Thus, mammalian families recovered from Upper Laetolil Beds include Bovidae, Carnivora, Elephantidae, Equidae, Lagomorpha, Suidae, Rodentia, Hominoidea and Rhenocerotidae. Remains of an invertebrate, Gastropoda were also recovered. For Upper Ndolanya Beds include almost the same families recovered from Upper Laetolil Beds, but based on former recovery of fossil fauna, these Beds outnumber greatly the Upper Laetolil Beds in bovid composition by 20 per cent. Such a change in species composition is noticed also from South African localities and East African localities such as the East Turkana. This is interpreted to be due to climatic change drier environments that included species adapted to such palaeoclimates.
For the first time, our team has been able to retrieve specimens identifiable to taxa, a pattern that not possible from previous workers who claimed to have recovered too sparse specimens to be identifiable to any taxon.
The Upper Manyara Beds as well as Lower Manyara taxonomic composition include aquatic species besides the large terrestrial mammalian fauna retrieved from there. In due regard, the former horizon is attributed to have affinity with Olduvai Bed III components and the latter, older horizon, is attributed to have affinity with upper parts of Bed II times at Olduvai Gorge. The Lower Manyara Beds can be said to have, in relative terms, affinity to species recovered from site RC 11 of the Chiwondo Beds, Malema region in northern Malawi, although the former site may be equable to the terminal age of the latter locality.
Fossil hominid remains; attributable to genus Homo and possibly species Homo erectus have been recovered from two localities, Mk 2 and Mk, along Lower Manyara Beds. On the other hand, stone tools, identified to belong to the Acheulian industrial technocomplex, were recovered from site Mk 4.
All of fossil fauna from Laetoli sites were mostly exfoliated and there shows to be little effect in terms of hydrodynamic sorting of the fossil bones. However, intense carnivore activity is witnessed due to the almost one to one ratio of proximal to distal ends. This is also true for the Lower Manyara Beds locality. Through examination of surface modifications of the fossil fauna, it has been established that there was carnivore consumption of ungulates. There is no evidence of hominid involvement that has to be testified by stone tools.
The Siwalik formations of northern Pakistan consist of deposits of ancient rivers that existed throughout the early Miocene through the late Pliocene. The formations are highly fossiliferous with a diverse array of terrestrial and freshwater vertebrates, which in combination with exceptional lateral exposure and good chronostratigraphic control allows a more detailed and temporally resolved study of the sediments and faunas than is typical in terrestrial deposits. Consequently the Siwaliks provide an opportunity to document temporal differences in species richness, turnover, and ecological structure in a terrestrial setting, and to investigate how such differences are related to changes in the fluvial system, vegetation, and climate. Here we focus on the interval between 10.7 and 5.7 Ma, a time of significant local tectonic and global climatic change. It is also the interval with the best temporal calibration of Siwalik faunas and most comprehensive data on species occurrences. A methodological focus of this paper is on controlling sampling biases that confound biological and ecological signals. Such biases include uneven sampling through time, differential preservation of larger animals and more durable skeletal elements, errors in age-dating imposed by uncertainties in correlation and paleomagnetic timescale calibrations, and uneven taxonomic treatment across groups. We attempt to control for them primarily by using a relative-abundance model to estimate limits for the first and last appearances from the occurrence data. This model also incorporates uncertainties in age estimates. Because of sampling limitations inherent in the terrestrial fossil record, our 100-Kyr temporal resolution may approach the finest possible level of resolution for studies of vertebrate faunal changes over periods of millions of years. Approximately 40,000 specimens from surface and screenwash collections made at 555 localities form the basis of our study. Sixty percent of the localities have maximum and minimum age estimates differing by 100 Kyr or less, 82% by 200 Kyr or less. The fossils represent 115 mammalian species or lineages of ten orders: Insectivora, Scandentia, Primates, Tubulidentata, Proboscidea, Pholidota, Lagomorpha, Perissodactyla, Artiodactyla, and Rodentia. Important taxa omitted from this study include Carnivora, Elephantoidea, and Rhinocerotidae. Because different collecting methods were used for large and small species, they are treated separately in analyses. Small species include insectivores, tree shrews, rodents, lagomorphs, and small primates. They generally weigh less than 5 kg. The sediments of the study interval were deposited by coexisting fluvial systems, with the larger emergent Nagri system being displaced between 10.1 and 9.0 Ma by an interfan Dhok Pathan system. In comparison to Nagri floodplains, Dhok Pathan floodplains were less well drained, with smaller rivers having more seasonally variable flow and more frequent avulsions. Paleosol sequences indicate reorganization of topography and drainage accompanying a transition to a more seasonal climate. A few paleosols may have formed under waterlogged, grassy woodlands, but most formed under drier conditions and more closed vegetation. The oxygen isotopic record also indicates significant change in the patterns of precipitation beginning at 9.2 Ma, in what may have been a shift to a drier and more seasonal climate. The carbon isotope record demonstrates that after 8.1 Ma significant amounts of C4 grasses began to appear and that by 6.8 Ma floodplain habitats included extensive C4 grasslands. Plant communities with predominantly C3 plants were greatly diminished after 7.0 Ma, and those with predominantly C4 plants, which would have been open woodlands or grassy woodlands, appeared as early as 7.4 Ma. Inferred first and last appearances show a constant, low level of faunal turnover throughout the interval 10.7–5.7-Ma, with three short periods of elevated turnover at 10.3, 7.8, and 7.3–7.0 Ma. The three pulses account for nearly 44% of all turnover. Throughout the late Miocene, species richness declined steadily, and diversity and richness indices together with data on body size imply that community ecological structure changed abruptly just after 10 Ma, and then again at 7.8 Ma. Between 10 and 7.8 Ma the large-mammal assemblages were strongly dominated by equids, with more balanced faunas before and after. The pattern of appearance and disappearance is selective with respect to inferred habits of the animals. Species appearing after 9.0 Ma are grazers or typical of more open habitats, whereas many species that disappear can be linked to more closed vegetation. We presume exceptions to this pattern were animals of the mixed C3/C4 communities or the wetter parts of the floodplain that did not persist into the latest Miocene. The pace of extinction accelerates once there is C4 vegetation on the floodplain. The 10.3 Ma event primarily comprises disappearance of taxa that were both common and of long duration. The event does not correlate to any obvious local environmental or climatic event, and the pattern of species disappearance and appearance suggests that biotic interactions may have been more important than environmental change. The 7.8 Ma event is characterized solely by appearances, and that at 7.3 Ma by a combination of appearances and disappearances. These two latest Miocene events include more taxa that were shorter ranging and less common, a difference of mode that developed between approximately 9.0 and 8.5 Ma when many short-ranging and rare species began to make appearances. Both events also show a close temporal correlation to changes in floodplain deposition and vegetation. The 7.8 Ma event follows the widespread appearance of C4 vegetation and is coincident with the shift from equid-dominated to more evenly balanced large-mammal assemblages. The 7.3 to 7.0 Ma event starts with the first occurrence of C4-dominated floras and ends with the last occurrence of C3-dominated vegetation. Absence of a consistent relationship between depositional facies and the composition of faunal assemblages leads us to reject fluvial system dynamics as a major cause of faunal change. The close correlation of latest Miocene species turnover and ecological change to expansion of C4 plants on the floodplain, in association with oxygen isotopic and sedimentological evidence for increasingly drier and more seasonal climates, causes us to favor explanations based on climatic change for both latest Miocene pulses. The Siwalik record supports neither “coordinated stasis” nor “turnover pulse” evolutionary models. The brief, irregularly spaced pulses of high turnover are characteristic of both the stasis and pulse models, but the high level of background turnover that eliminates 65–70% of the initial species shows there is no stasis in the Siwalik record. In addition, the steadily declining species richness and abrupt, uncoordinated changes in diversity do not fit either model.
In this study the rich variety of fossil microorganisms and other ultrastruchlres in the Messel oil shale is documented. The taphonomy of the micro- and the macro organisms is discussed and a basic model for microbial life in the Eocene Lake Messel is proposed. Documentation of the Messel microbiota was made using a scanning electron microscope fitted with an energy-dispersive X-ray analyzer, and a transmission electron microscope. The most common objects discovered were fossil bacteria in the form of cocci, coccobacilli, bacilli, curved rods and filaments, preserved as moulds, crusts, casts, encrusted casts and clay-coated casts. The main lithifying mineral is apatite, followed by siderite. The bacteria occur on fossil remains of macroorganisms. Sideritic bacteria are usually found on keratinous substrates, whereas apatitic bacteria occur preferentially on fish remains. Lithification of the bacteria was selective. It is suggested that the preserved bacteria were heterotrophic, Gram-positive anaerobes, which may have belonged to the group of clostridians.
The siliceous claystone and chert lithologic units of the Triassic-Jurassic chert-clastic sequence are well exposed in the Inuyama, Mt. Kinkazan and Hisuikyo areas of the southeastern Mino Terrane. Twenty-one continuous sections from those areas were investigated in order to establish comprehensive radiolarian biozones and clarify the successive lithologic changes through the Triassic and lowest Jurassic. Twenty new radiolarian zones are established; the lowest two are assemblage zones and the others are defined by the first or last occurrence of index taxa. The definitions are as follows in chronological order: TR 0, Follicucullus Assemblage Zone (early Spathian or older); TR 1, Parentactinia nakatsugawaensis Assemblage Zone (late Spathian); TR 2A, Eptingium nakasekoi Lowest-occurrence Zone (early Anisian); TR 2B, Triassocampe coronata group Lowest-occurrence Zone (early Anisian); TR 2C, Triassocampe deweveri Lowest-occurrence Zone (late Anisian); TR 3A, Spine A2 (possiblly derived from Oertlispongus inaequispinosus) Lowest occurrence Zone (late Anisian) ; TR 3B, Yeharaia elegans group Lowest-occurrence Zone (early Ladinian); TR 4A, Muelleritortis cochleata Lowest-occurrence Zone (late Ladinian); TR 4B, Spongoserrula dehli Lowest-occurrence Zone (late Ladinian to early Carnian); TR 5A, Capnuchosphaera Lowest-occurrence Zone (early Carnian); TR 5B, Poulpus carcharus sp. nov. Lowest-occurrence Zone (early to late Carnian); TR 6A, Capnodoce- Trialatus Concurrentrange Zone (late Carnian to early Norian), TR 6B, Trialatus robustus-Lysemelas olbia gen. et sp. nov. Partial-range Zone (early Norian); TR 7, Lysemelas olbia gen. et sp. nov. Lowest-occurrence Zone (early to late Norian); TR 8A: Praemesosaturnalis multidentatus group Lowest-occurrence Zone (late Norian); TR 8B: Praemesosaturnalis pseudokahleri sp. nov. Lowest-occurrence Zone (late Norian) ; TR 8C: Skirt F (possiblly derived from Haeckelicyrtium takemurai) Lowest-occurrence Zone (late Norian to early Rhaetian); TR 8D: Haeckelicyrtium breviora sp. nov. Taxon-range Zone (early to late Rhaetian) ; JR OA: Haeckelicyrtium breviora sp. nov.-Bipedis horiae sp. nov. Partial-range Zone (Hettangian); and JR OB: Bipedis horiae sp. nov. Lowest-occurrence Zone (Hettangian/Sinemurian) . These zones are correlated to previousy established radiolarian assemblages and zones in Japan and other regions. Age assignment of the zones is also discussed on the basis of the correlation and other available chronological data. The original stratigraphic succession of the Triassic in the studied area, which ranges in age from Early Triassic to Early Jurassic, is more than 100 m in thickness and can be reconstructed in detail. The succession is subdivided into seven units based on lithologic features. Each unit was probably accumulated under a particular sedimentary condition, thus successive changes of paleoceanographic environments during Triassic time can be traced continuously. Nine new genera including Ayrtonius, Blonzella, Braginella, Bulbocampe, Enoplocampe, Lysenzelas, Parvibrachiale, Spongoxystris and Veles, and 47 new species are described herein. A comprehensive list of identified taxa is presented.
Homology of virtually all major components of facial anatomy is assessed in Archosauria in order to address the function of the antorbital cavity, an enigmatic structure that is diagnostic for the group. Proposed functions center on its being a housing for a gland, a muscle, or a paranasal air sinus. Homology is approached in the context of the Extant Phylogenetic Bracket method of reconstructing unpreserved aspects of extinct organisms. Facial anatomy and its ontogeny was studied in extant archosaurs (birds and crocodilians) to determine the osteological correlates of each soft-tissue component; resemblances between birds and crocodilians comprised the similarity test of homology. The congruence test of homology involved surveying phyiogenetically relevant fossil archosaurs for these bony signatures. The facial anatomy of extant birds and crocodilians is examined in detail to provide background and to discover those apomorphic aspects that contribute to the divergent specialization of these two groups and thus obscure homologies. Birds apomorphically show enlarged eyeballs, expanded nasal vestibules, and reduced maxillae, whereas crocodilian faces are dorsoventrally flattened (due to nasal rotation) and elongated. Most facial attributes of archosaurs are demonstrably homologous and in fact characterize much more inclusive groups. Special emphasis has been placed on the nasal conchae and paranasal air sinuses. Within Amniota, the following conchal structures are homologous, and all others are neomorphs: avian caudal concha, crocodilian concha + preconcha, Sphenodon caudal concha, squamate concha, and probably the mammalian crista semicircularis. The avian antorhital paranasal air sinus is homologous with the crocodilian caviconchal sinus; the maxillary sinus of placental mammals is not homologous with the archosaurian paranasal sinus. With regard to the function of the antorbital cavity, archosaurs possess homologous nasal glands, dorsal pterygoideus muscles, and paranasal air sinuses, but the osteological correlates of only the paranasal sinus involve the antorbital fenestrae and fossae. Thus, the antorbital cavity is best interpreted as principally a pneumatic structure.
Multivariate statistical analyses are used to distinguish species in the genera Montastraea and Solenastrea through a continuous Neogene sequence (five Ma time interval) in the Cibao Valley of the northern Dominican Republic. Some older (by approximately 10 Ma) material from the same region also is included in the analyses. The material consists of approximately 280 colonies of Montastraea (74 of which are measured) from a total of 59 localities, and 66 colonies of Solenastrea (15 of which are measured) from a total of 37 localities. Twelve additional colonies of Montastraea from the Vokes' collections of the same localities are also measured, and added to the data set. The material is first sorted into the two genera on the basis of qualitative examination of septal structure, the structure of the columella and associated paliform lobes, and the texture of the coenosteum. Sixteen characters consisting of linear distances and counts are measured in transverse thin-sections of ten corallites per colony in Montastraea; ten similar characters are measured on the upper surface of ten calices per colony in Solenastrea. The data are analyzed using cluster and canonical discriminant analysis to group the colonies into clusters representing species. Seven species are so defined in Montastraea and two in Solenastrea. These groupings are then used statistically to reclassify type specimens for 12 of the 17 described species of Montastraea and four of the seven described species of Solenastrea. Three of the 12 species are synonymized in Montastraea, and two of the four species are synonymized in Solenastrea. Further qualitative study of the remaining types suggests that nine species of Montastraea and two species of Solenastrea existed altogether in the Caribbean during the Neogene. The stratigraphic range of two of the seven Dominican Republic species of Montastraea is shown to extend back to the Oligocene. Another of the Dominican Republic species is found to exist today, and is widely distributed throughout the Caribbean. Of the nine Neogene Caribbean species, only this species survived the Plio-Pleistocene extinction event. Only one species of Mantastmea is found to be endemic to the Dominican Republic. One of the remaining three species of Montastraea also has a limited stratigraphic distribution and appears confined to the southern Caribbean. Both species of Solenastrea appear to range from the Early Neogene to the Recent, and are widely distributed throughout the Caribbean. Trends within each species of Montastraea are analyzed through the sequence using nonparametric statistical procedures. Significant changes are detected upsection for at least four of the seven species in character complexes related to corallite size, septal development, and coenosteum development; however, significant correlations with species diversity suggest that these trends may be environmental in origin. Occurrence data suggest that two of the seven species of Montastraea may be indicative of shallow, nearshore conditions, whereas another two may be confined to muddy, and presumably deeper, patch reeflocalities. When data spanning the Oligocene to Recent are analyzed, significant directional trends are detected in one of the three longerranging Dominican Republic species; however, the amount of change does not exceed that observed within modern species. This suggests that, despite an apparent zigzag pattern, net stasis may be the rule in Montastraea. This study represents part of a multidisciplinary project on the paleontology and stratigraphy of the northern Dominican Republic, coordinated by P. Jung and J. B. Saunders of the Naturhistorisches Museum in Basel, Switzerland.