PaleoBios, Volume 13, Supplement to Number 49 1990 CALIFORNIA PALEONTOLOGY CONFERENCE ABSTRACTS DIVERSITY DISTRIBUTION OF MODERN HERMATYPIC CORAL GENERA AND ITS BEARING ON THE LONGITUDINAL POSITIONING OF CIRCUM-PACIFIC TERRANES. BELASKY, Paul, Dept. of Earth and Space Sciences, Univ. of CA, Los Angeles, CA, 90024 Large-scale tectonic transport has been widely proposed as a probable mode of origin of Cordilleran suspect terranes containing Tethyan taxa of Permian and Triassic age. An alternative model (Newton, 1988) suggests that major displacements in longitude are not required because these anomalous Tethyan faunal elements represent pantropic taxa that migrated with attenuating diversities into the eastern paleo- Pacific. Both hypotheses are tested using the generic diversity of modern hermatypic corals at 120 localities in the Pacific and Indian oceans. A second order polynomial surface was constructed from the data by using trend surface analysis and a correlation of 81% between the data and the diversity surface was obtained. The surface has a shape of a latitudinally-compressed dome centered over the Indo-Pacific region and nearly symmetrical about the Equator. Eastwardly-decreasing gradient of the coral diversity distribution was used to find the present positions of four Pacific islands. Hawaii (20°N, 156°W), Tahiti (18°S, 149°W), Easter Island 27°S, 109° W) and Tutuila (American Samoa; 14°S, 171°W) were each removed separately from the data, and new diversity surfaces were obtained from the reduced data set. Neither the shape, nor the orientation of the surface changed measurably following the removal of each data point. The islands were then returned to the map using their geomagnetically- derived lalitudes and the longitudes obtained from the intersections of lines of latitude with the appropriate diversity contours. Easter Island and Tahiti were placed 120 km northwest and less than 100 km southeast from their actual locations respectively. Hawaii and Samoa were placed approximately 1200 km southeast and 130 km west of their actual locations, respectively. The results show that the method is most successful for well-sampled sites with low to medium diversity (e.g. Easter Island, Tahiti). The longitude of Samoa, a high-diversity site, is difficult to constrain because contours run almost parallel to the Equator near the center of the diversity surface. The error in the location of Hawaii is reduced by approximately 400 km when the effect of nondipole field in the vicinity of Hawaii (Cox, 1975) is taken into account. If Tahiti were tectonically transported to tropical America at some time in the future, the diversity of its coral fauna (28 genera) would be out of context with that of the surrounding region (6 genera or less). Tahiti would therefore be correctly interpreted as an exotic terrane from the central or western Pacific on the basis of its diversity values alone. The "pantropic distribution" model would fail to correctly explain its anomalous position. Because of the low diversity of Permian Tethyan genera in Cordilleran suspect terranes the magnitude of their longitudinal displacement is diffticult to determine on the basis of the diversity data alone. However, the presence of even a few Tethyan faunal elements in these terranes implies substantial displacement in longitude because of the greater width of the paleo-Pacific, the lower generic diversity of Permian corals in comparison to that of the modern Indo-Pacific Scleractinia and the sampling bias. More data on diversity of different Permian and Recent faunal groups will be necessary in order to test the paleogeographic potential of the proposed method. DEPTH-DEPENDENT SPECIES BIAS IN COCCOLITHOPHORE TEST REMAINS BOYSEN, Marilyn P. and SILVER, Mary W., 273 Applied Sciences Bldg., Univ. of CA, Santa Cruz, CA, 95604 The calcium carbonate tests of the phytoplanktonic coccolithophores are important components of carbonate oozes and are useful in stratigraphy and reconstructions of paleoceanic circulation, temperature and community structure. In order to understand and correctly interpret the data generated from the coccolithophore signal, it is necessary to understand the life processes of the organisms as well as the death, dissolution, sedimentation and burial, or taphonomic, processes. Previous studies have demonstrated that phytoplankton live in species-specific depth layers. Other authors have characterized these as an upper, warmer, nutrient-poor layer and a lower, colder, darker, nutrient-rich layer. This study involves identifying the depth layer in which the coccolithophore exists in life and comparing this with the depth layer of the calcium carbonate test remains. Our data show that the intact skeletons of coccolithophores (coccospheres) are distributed in the Page 2 Abstracts 1990 California Paleontology Conference water column in two distinct groups that closely approximate the range of living organisms. Coccosphere parts (coccoliths) that occur alone or in aggregates reflect these species-specific groupings. Data from coccoliths found in sub-euphotic zone samples corroborate earlier suggestions, based on fecal pellet and isotopic studies, that the material leaving the euphotic zone is derived primarily from the lower layer. Consequences to paleoceanic reconstructions are: 1) the temperature signal of material from the lower layer would imply a cooler euphotic zone than really existed; 2) attempts at reconstruction of species diversity, already severly inhibited due to dissolution and preservation factors, is further compromised; 3) there is less material available for delivery to the sediments than would be expected from total euphotic zone standing stock because coccolithophore abundances are lower in the deeper layer. ONTOGENETIC VARIATION IN MAG- NESIUM CONTENT OF THE RECENT BRACHIOPOD TEREBRATALIA TRANS- VERSA BUENING, Nancy, Dept. of Geology, Univ. of CA, Davis, CA 94616 Electron microprobe analyses of the Recent brachiopod Terebratalia transversa indicate that the amount of magnesium incorporated into the shell mineralogy is influenced by physiological factors related to growth rate rather than to temperature variations. Magnesium content of skeletal calcite varies as a function of both environmental and genetic factors. In general, magnesium content of calcites increases as ambient seawater temperature increases (Chave, 1954). However, magnesium contents of both organically and inorganically precipitated calcite formed at the same temperature are not the same. This disparity suggests that genetic factors (e.g., biological partitioning) may mask the temperature/ magnesium relationship (Lowenstam and Weiner, 1989). Spot analyses (avoiding punctae) performed on polished longitudinal sections of T. transversa collected from intertidal (l-2m) and subtidal (74m) depths from Puget Sound, Washington, show relatively high levels of MgC03 near the umbonal region followed by a significant drop and leveling off of the MgC03 content toward the commissure. This trend corresponds to the growth pattern of T. transversa, where initial growth is rapid and then slows down to a constant rate as individuals age (Paine, 1969 and Thayer, 1975). If the temperature effect were strong, a significant difference in magnesium content between subtidal and intertidal populations would be expected. However, no distinctive patterns or differences in MgC(>3 levels between intertidal and subtidal populations are apparent. The same ontogenetic pattern of magnesium uptake observed in shells from both populations suggests that biological partitioning of magnesium related to growth rate filters out the temperature effect in the process of biomineralization in T. transversa. This study demonstrates the need for further investigation of the magnesium/temperature relationship in skeletal calcites. Chave, K.E. 1954. Aspects of the biogeochemistry of magnesium: 1. Calcareous marine organisms. Jour. Geol. 62:266-283. Lowenstam, H.A. and S. Weiner. 1989. On Biomineraliztion. Oxford University Press, New York. 324 pp. Paine, R.T. 1969. Growth and size distribution of the brachiopod Terebratalia transversa Sowerby. Pac. Sci. 23:337-343. Thayer, C.W. 1975. Size-frequency and population structure of brachiopods. Paleogeog., Paleoclim., Paleoecol. 17:139-148. MARINE MAESTRICHTIAN (?) WITHIN THE ARCTIC CIRCLE ON THE SOUTHWEST MARGIN OF MACKENZIE DELTA, CANADA DURHAM, Jean B., Dept. of Biology, Dominican College, San Rafael, CA 94701; J. Wyatt DURHAM, Museum of Paleontology, Univ. of CA, Berkeley, CA 94720; Robert F. KAAR, Dept. of Earth Sciences, San Francisco City College, San Francisco, CA. 94112 On a primarily non-geological excursion along the Dempster Highway into arctic Canada in June, 1989, a previously unreported fossiliferous rock sequence was encountered. About 8m (25 feet) of mostly fine to medium grained clastic sediments crop out in roadcuts along the highway just west of the Peel River crossing (67° 20'N, 154° 55'W) near Fort McPherson. A rapid reconnaissance was made and some molluscan fossils collected. Some beds are locally calcareous and in part phosphatic. Fossils are usually fragmentary and locally abundant. Tentatively identified genera include Astarte, Cymbophora, Flaventia , Gyrodes, Nucula, Pholadomya, Perna, and Pterocerella. A few kilometers (about 3) farther southwest along the highway a deep road fill is present at the foot of an escarpment. Lithologically the included sediments are similar to those of the above locality and it is suggested that they were transported from it. Fossils present here included Astarte, Aphrodina tippana, Troostella (?), Calliomphalus and a pectinid. The Aphrodina and Pterocerella as well as the total 1990 California Paleontology Conference Abstracts Page 3 assemblage, suggest a Maestrichtian age. The geologic map of the region by Norris (mapped in 1974 and published in 1981) shows only Lower Cretaceous in the vicinity and Aptian-Albian fossils have been found within 5 kms. MORE ON THE HELICOPLACOIDS (ECHINODERMATA) DURHAM, J. Wyatt, Museum of Paleontology, Univ. of CA, Berkeley, CA, 94720 The Helicoplacoids are among the oldest (perhaps 560 my) known non-carpoid echinoderms. Their pyriform to fusiform expansible test may attain a height of 8 cm. Detailed external morphologic variation is great, for which several major taxa are recognized. In some taxa, ambulacral tubefeet emerge between sequential plates, in others between contemporaneous plates. The mouth was terminal, not lateral as interpreted by Derstler (1981) and Paul and Smith (1984). Ambulacra are not recognizable in early ontogeny, a single ambulacrum appears at one-third adult size and branches at one-half. Two parallel branches then continue to oral area. Helicoplacoids lived upright with aboral (originally proposed as "apical") pole imbedded in seafloor sediments. No special attachment morphology is recognizable. Contrary to Paul and Smith's (1984) interpretation, no "flooring plates" under the ambulacra have been recognized in sections across them. Paul and Smith considered them to be at the base of the non-carpoid echinoderm evolutionary development but they are best considered as a "dead end" lateral branch of the principal lineage. Helicoplacoids are known from Early Cambrian (Atdabanian Age) sediments of the Cordilleran geosyncline from Death Valley, California, north into British Columbia. LATE-QUATERNARY VEGETATION CHANGE IN THE CENTRAL SIERRA NEVADA AND ITS PALEOCLIMATIC IMPLICATIONS. EDLUND, Eric, and BYRNE, Roger, Geography Dept., Univ. of CA, Berkeley, CA, 94720. The Quaternary vegetation history of the Sierra Nevada is as yet poorly understood. The pollen record is dominated by taxonomically difficult groups such as Pinus and the TCT type (Taxodiaceae, Cupressaceae, Taxaceae), and few well-dated diagrams have been published. At higher elevations, where most lakes are located, pine pollen accounts for more than 90 percent of the present rain. In this paper, we show how lakes at intermediate elevations (ca. 2,000 m) provide a more sensitive record of vegetation change. Pollen, microscopic charcoal, and conifer needles from Lake Moran on the North Fork of the Stanislaus document a complex history of vegetation change in which Artemisia, Juniperus, Pinus, Quercus, and Abies have played important roles. The record covers approximately the last 15,000 years. Analysis of microscopic charcoal indicates that fires were more frequent in the area during the late- Pleistocene and early Holocene. This was also a period in which what was probably a closed canopy forest dominated by pines (Pinus contorta and Pinus monticola) gave way to a more open woodland in which Quercus was important. The Lake Moran record clearly indicates that the postglacial vegetation history of the Sierra involved much more than upslope migration of plants as the ice retreated. Climatic change was probably the primary factor responsible for changes evident in the fossil record. THE YOUNGER DRYAS COOL EPISODE, ORCA BASIN, GULF OF MEXICO FLOWER, Benjamin P, KENNETT, James P., Dept. of Geological Sciences and Marine Science Institute, Univ. of CA, Santa Barbara, CA, 93106 The Younger Dryas episode was a brief return to near- glacial conditions (11-10 ka) during the last deglaciation. Two major features characterize this enigmatic cooling: its brevity, and its confinement to the Northern Hemisphere. Younger Dryas cooling is well-documented in European pollen records and in Greenland ice cores, but its geographic extent in the marine record is less well known. Previously, evidence for Younger Dryas cooling in marine sequences from the Atlantic Ocean has concentrated at latitudes higher than 45° N. Here we summarize evidence for its presence in the Gulf of Mexico. Oxygen isotopic and faunal assemblage data on planktonic foraminifera from two piston cores in the anoxic Orca Basin indicate a marked cooling of surface waters, radiocarbon dated at between 11.2 and 10.2 ka. This interval immediately follows the well- known deglacial meltwater spike and is characterized by relatively high 8180 values averaging -0.5 % and by cool-water planktonic foraminiferal assemblages. The presence of the Younger Dryas cool episode in the Gulf marks the southernmost latitude in the North Atlantic at which it has so far been reported. The interval of more positive 8180 during Younger Dryas time in the Gulf ofMexico has also been interpreted as a temporary cessation of meltwater influx to the Gulf (Broecker et al., Nature 1989). Evidence from proglacial lakes of North America Page 4 Abstracts 1990 California Paleontology Conference suggests that meltwater was diverted eastward through the St. Lawrence seaway during this interval. The timing of the meltwater cessation supports the contention that low-salinity, low-density meltwater disrupted thermohaline circulation in the North Atlantic and cooled the region during the Younger Dryas interval. A simple rediversion of meltwater to the Gulf as a result of the Younger Dryas Laurentide glacial advance is not supported by the oxygen isotopic record of the pink variety of Gs. ruber, a summer species in the Gulf. There is no evidence for increased summer meltwater flow, which is contrary to expectation, and yet an important increase in temperature and/or meltwater flow is evident in the year-average isotopic record of the white variety of Gs. ruber. This incongruity is possibly explained by important changes during the winter months, involving some combination of increased meltwater flow and higher temperatures. TAPHONOMY OF THE PIPESTONE SPRINGS LOCAL FAUNA GARCIA, Daniel, Museum of Paleontology, Univ. of CA, Berkeley, CA 94720 The Pipestone Springs local fauna (Late Eocene, Chadronian), located in Jefferson County, Montana, is one of the classic mammalian fossil sites in North America. This fossil assemblage occurs within tuffaceous siltstones, which were deposited by clast- deficient debris flows. The fossil material consists mostly of mammalian microvertebrate remains, but some mammalian macrovertebrate remains are present. The microvertebrate remains show characteristics of a mammalian carnivore-generated scatological assemblage. These remains are usually fragmentary, isolated, and all skeletal elements are represented. Mammalian coprolites are also commonly found; many contain identifiable bone. Macrovertebrate remains are almost always fragmentary and some exhibit gnaw and puncture marks. Bone chips are also abundant throughout this fossil assemblage. It appears as if macrovertebrate remains accumulated on the ground as a result of mammalian carnivore and scavenger activity. Overall, this fossil assemblage represents a good approximation of the mammalian community living at that time. FOSSIL VERTEBRATES FROM THE LATE CRETACEOUS JUDITH RIVER FORMATION, NORTH-CENTRAL MT GOODWIN, Mark B., Museum of Paleontology, Univ. of CA, Berkeley, CA 94720 Recent work in the Judith River Formation of northcentral Montana augments the known Judithian faunas by the addition of new taxa from over 200 localities. This collection provides a new base for comparison with Judithian faunas from Montana and Canada. Near-shore marine, overbank, and channel sandstone facies were sampled from four study areas. Faunal differences noted between study areas are related to marine-nonmarine facies changes. The largest collection of fossils was recovered from Kennedy Coulee, 15 km north of Rudyard, Hill County, Montana. A laterally extensive coal bed separates-the "Foremost" equivalent beds from the overlying "Oldman" sediments. A comparison of mammal producing microvertebrate localities from the "Foremost" and "Oldman" beds showed no significant faunal changes. Notable additions to the faunal list from the type area include two pachycephalosaurids: Omatotholus sp.and a full- domed morphotype; a partial skeleton of Brachylophosaurus , eight turtle taxa, and ten species of mammals. Potassium-argon and argon-argon analyses of two tuffs indicate an age of ca. 78 Ma for the Judith River Formation in Kennedy Coulee (Goodwin and Deino, 1989). VERTEBRATE PALEONTOLOGY AND BASIN ANALYSIS, NORTH BOULDER BASIN, JEFFERSON COUNTY, MT. LOFGREN, Donald L., Museum of Paleontology, Univ. of CA, Berkeley, CA, 94720 The North Boulder Basin (NBB) is a fault-bounded Tertiary basin that contains a thick package of non- marine sediments. Vertebrate fossils, conglomerate provenance, and sediment distribution patterns provide the basis for interpreting the evolution of the NBB. Presence of Chadronian (Renova Fm), Late Arikareean (Negro Hollow Beds) and Early-Early Late Barstovian (Six Mile Creek Fm.) age sediments are indicated by fossil mammals including, Chadronian: Macrotarsius sp., Megacerops sp., Merycoidon sp., and Oreonetes sp.; Late Arikareean: Diceratherium sp., Stenomylus sp., Oxydactylus sp., Dinohyus sp., Hysiops sp., and Merycoides sp.; Early-Early Late Barstovian: Merychippus sp., Aepycamelus, sp. Aelurodon sp., Leptarctus sp., Merriamoceras sp. and Paracosoryxsp. Chadronian sediments (Renova Fm) reflect mixed mass-flow and fluvial-floodplain deposition while Late Arikareean sediments (Negro Hollow Beds) represent mass-flow with lesser fluvial-floodplain and lacustrine(?) deposition. Chadronian (and less 1990 California Paleontology Conference Abstracts Page 5 certainly Late Arikareean) sediment distribution patterns and conglomerate provenance (mainly Boulder Batholith granitics) indicate the presence of a southeast-draining alluvial plain that probably extended into the Three Forks Basin. Coarser— grained Early- Early Late Barstovian sediments (Six Mile Creek Fm) indicate the extensive development of alluvial fans. In contrast to Chadronian-Late Arikareean sediments, Early-Early Late Barstovian conglomerates were derived from localized uplifts centered in the Negro Hollow-Doherty Mt (Paleozoic carbonates) and Bull Mt (Elkhorn Mt Volcanics) areas. These uplifts truncated previously developed drainage patterns and delineated the present day configuration of the NBB. A PRELIMINARY REPORT ON THE ELASMOBRANCH FAUNA OF THE EOCENE LA MESETA FORMATION, ANTARTICA PENNINSULA LONG, Douglas J., Museum of Paleontology, Univ. of CA, Berkeley, CA, 94720. The waters around present day Antarctica contain an exceedingly depauperate elasmobranch fauna. However, recent investigations into the Eocene marine sediments of the La Meseta Formation of Seymour Island, Antarctic Peninsula have produced thirteen fossil sharks and one skate new to the Antarctic region. Two, Stegostoma sp.. and Pseudoginglymostoma sp. are new to the fossil record. Three, Anomotodon multidenticulata n.sp. , Squalus weltoni n.sp., and Lamna australis n.sp. are previously undescribed species. Heptranchias howelli, Squalus sp., Centrophorous sp., Deania sp., Dalatiasicha sp., Odontaspis winkleri, Carcharis cuspidata, Scoliodon sp. and teeth of Rajidae indent, are reported in Antarctica for the first time. In addition, the new fossil shark material greatly expands the representation of the other previously known fossil sharks from Seymour Island: Squatina sp., Pristiophorous sp., Carcharias macrota, Carcharodon auriculatus, and Myliobatus sp. The elasmobranch fauna of the La Meseta Formation is important because it 1) suggests a temperate marine climate for this area in the Eocene; 2 ) gives early evidence for diurnal vertical migration in some of the fossil sharks; 3) provides insight into the distribution and biogeography of these Eocene elasmobranchs; (4 supports the idea that the Eocene Antarctic ichthyofauna was very diverse, and 5) demonstrates the extent of polar extinction due to the terminal Eocene Event. MICROPALEONTOLOGICAL STUDY OF TERTIARY ROCK FORMATIONS ALONG THE NAGA-TOLEDO AREA, CABE ISLAND, PHILLIPINES LUBAS, Lourdes L., Energy Research Laboratory, Office of Energy Affairs, Makati, Metro Manila, Phillipines A paleontological study of sedimentary rocks bearing small and larger foraminifera was conducted along a small section of the Naga-Toledo area of Centra] Cebu, a known coal basin in the central southeastern part of the Philippines Of the 28 rock samples collected, most were hard dense limestones which grade into marls with common to abundant larger foraminifera and two were fine-grained clastic sediments with few suspected small planktonic and benthonic foraminifera. The rock samples were processed into 27 thin sections and 65 whole specimen thin sections of isolated larger foraminiferal specimens. Preliminary micropaleontological analysis revealed that the larger foraminiferal specimens were largely megalospheric and have mostly calcareous perforate tests. Initial morphological analysis indicates the presence of the genera Nummulites and Lepidocyclina pointing to biozones marking Oligocene to Miocene ages consistent with the ages determined in previous studies of the same area where the rock samples were collected. Larger foraminifera generally live in warm shallow tropical seas. BIOGEOGRAPHY AND AFFINITY OF LOWER DEVONIAN (PRAGIAN) OSTRACODES FROM CENTRAL NEVADA LUPTOWITZ, Lisa M., Earth Sciences Dept., Univ. of CA, Riverside, CA 92521 Early Devonian faunas display increasing worldwide provincialism, with a peak near the Pragian-Emsian boundary. Brachiopods and corals from Nevada exhibit this high level of provincialism, but display a greater affinity with the Appohimchi (Eastern Americas Realm) faunas than with other Cordilleran (Old World Realm) faunas. A silicified ostracode fauna from the Pragian of central Nevada provides an opportunity to test this affinity pattern for ostracodes. A diverse and abundant ostracode assemblage (41 genera, 53 species) was recovered from the Kobeh Member of the McColley Canyon Formation in the northern Roberts Mountains of central Nevada. The assemblage is similar to other Pragian and Emsian ostracode assemblages from Nevada in that it is dominated by Hollinaceans and lacks Beyrichiaceans. Unlike the brachiopods and corals, the Kobeh ostracodes are a subequal mix of provincial, bi- provincial and cosmopolitan genera. The Kobeh Page 6 Abstracts 1990 California Paleontology Conference ostracodes also have a greater percentage of shared genera with northern Cordilleran (western Canada and Alaska) assemblages than with Appohimchi assemblages. These results suggest that, for ostracodes, there was no barrier to mixing within the Cordilleran Region, and that ostracode mixing between Nevada and the Appohimchi Subprovince was partially restricted. The majority of the Kobeh ostracode species are new or have been left in open nomenclature. Many of them are very similar to previously described species from the Middle Devonian of the Michigan Basin Subprovince, suggesting that they originated in Nevada and subsequently moved via a passageway into eastern North America. PRE-EUROPEAN/POST-EUROPEAN VEGETATION CHANGE IN CENTRAL CALIFORNIA: A HIGH RESOLUTION RECORD FROM THE SANTA BARBARA BASIN. MENSING, Scot, and BYRNE, Roger., Geography Dept., Univ. of CA, Berkeley, CA 94720. The varved sediments of the Santa Barbara Basin provide a unique record of Holocene vegetation change insofar as the high sedimentation rate makes it possible to sample at yearly intervals. During the last few years, researchers at Scripps (Schimmelmann and Lange) have dated cores that bridge the gap between surface box cores and piston cores. This gap dated to the 17th and 18th centuries. This period was presumably a time of major vegetation change in coastal California as the establishment of the Missions involved the introduction of livestock, alien plant species, and the decimation of the native Indian population. In this paper we present pollen and charcoal evidence from several cores which indicates that changes in the frequency and intensity of wildfires had an important impact on the composition of vegetation in the Transverse Ranges. In the pre- European period fires were infrequent but very intense, whereas in the present century there have been relatively few major conflagrations. Changes in the relative importance of woodland taxa such as oaks, may have been brought about by these changes in wildfire regimes. A 20 YEAR RECORD OF PALEORAINFALL AND RECENT ENSO EVENTS FROM REEF CORALS AT PADANG BAI (BALI, INDONESIA) BY LASER-INDUCED FLUORESCENCE SPECTROMETRY MOORE, Michael D., Dept. of Paleontology, Univ. of CA, Berkeley, CA 94720; PALMER, Cynthia E.A., SILVA, Robert J., Nuclear Chemistry Div., Lawrence CA 94551; BUDDEMEIER, Robert W., Kansas Geol. Survey, Lawrence, KS, 66046; RUSSO, Richard E., Applied Sciences Div., Lawrence Berkeley Laboratory, Berkeley, CA 94720 At best, Pacific weather records date only to the mid- 1800's. This lack of long-term data limits understanding of the frequency and magnitude of past El Nino-Southern Oscillation (ENSO) events. High- resolution proxy records of much greater length can be obtained from long-lived reef corals. In tropical climates, organic products of terrestrial decomposition (fulvic and humic acids) are flushed from drainage basins by monsoon rains and incorporated into the skeletons of corals on nearshore reefs. When present, these acids appear as fluorescent yellowgreen bands under UV light. Recent work in Australia has shown that variations in fluorescence intensity can be an accurate measure of past river discharge and rainfall. It was hypothesized that fluorescent banding might exist in Indonesian corals, and if so, would provide a highly sensitive record of ENSO activity due to Indonesia's unique geographic setting. A major atmospheric center of action, known as the Equatorial Low, is located over Indonesia. In normal years, deep convection generated by the Equatorial Low drives tropospheric circulation in the equatorial Pacific and brings monsoon rains to Southeast Asia. During ENSO events, the Equatorial Low loses strength and shifts eastward, producing drought in Indonesia. Core samples were collected from large Porites lobata colonies at Padang Bai, W. Bali, using a SCUBA-powered pneumatic drill. Laser-induced fluorescence spectrometry (354 nm) was used to measure interannual variation in fluorescence intensity along the growth axis of the slabs. Coral growth chronologies were generated by skeletal densitometry. Results show good correlation between fluorescence intensity (at 550 nm) and local rainfall records (1965-85). The ENSO events of 1972-73 and 1982-83 (the strongest event on record) are indicated by negative departures in fluorescence intensity proportional to event strength. The presence of a fluorescence proxy in Indonesian corals combined with the sensitivity of laser-induced fluorescence spectrometry makes possible paleorainfall reconstructions from cores dating back 500-700 years. POSTCRANIAL DESCRIPTIONS OF ILARIA AND NGAPAKALDIA (VOM- 1990 California Paleontology Conference Abstracts Page 7 BATIFORMES, MARSUPIALIA) AND THE EVOLUTION OF VOMBATIFORM POSTCRANIAL MORPHOLOGY. MUNSON, Carol J., Biology Dept., Univ. of California, Riverside, CA 92521 The postcrania of the vombatiform marsupial Ilaria illumidens from medial Miocene strata of South Australia are described and compared to other vombatiforms with the observation that it shares a similar morphology of the manus and pes with living wombats. While this similarity indicates a certain degree of fossorial activity, the size and vertebral, morphology of Ilaria argue against a burrowing lifestyle. Another medial Miocene vombatiform, Ngapakaldia tedfordi, is described as having a generalized plesiomorphic skeleton similar in many ways to that of the phalangeriform possums, but with adaptations for greater size and a plantigrade, terrestrial habitus. Besides stouter and more robust limbs, these adaptations are evident in the concave dorsal surface and laterally facing fibular facet of the astragalus that creates a less flexible upper ankle joint. For this study, a cladistic analysis was made using the postcrania of all the families in the Vombatiformes and several species representing outgroups in order to establish synapomorphies for the group and to evaluate the position of these two genera within it. The results of this analysis indicate that the ilariids and vombatids probably share a common ancestor based on the similarity of the metapodials and phalanges, especially the uniquely identical morphology of the proximal metapodial facets. Ngapakaldia's similarity in form to phalangeriform possums reflects the arboreal ancestry of the vombatiform clade and indicates the plesiomorphic state from which the postcrania of other, more specialized, vombatiform families (i.e. fossorial wombats and ilariids) are derived. COMPARISON OF ISOLATED UPPER MOLARIFORM TEETH FROM MERY- CHIPPINE DENTITION BASED ON COMPARISON OF WEAR PATTERNS PAJAK, Alois F., Earth Sciences Dept., Univ. of CA, Riverside, CA, 92521 Large numbers of isolated merychippine upper molariform teeth have been recovered from the lower Barstow Formation, Mud Hills, California. Two species, "Merychippus" stylodontus and "M". intermontanus, have been used to define separate biozones within the lower and upper Barstow Fm. respectively. Because of convergences and parallelism in dental morphology, differentiation between the two species on the basis of cheek tooth dentitions is difficult A census was made of upper molar morphology of a quarry sample purported to represent "Merychippus" stylodontus, with characteristics being recorded with respect to height of the mesostyle. This sample was compared to another, considered to represent "M." intermontanus. Based on this comparison, several differentiating characteristics have been determined, including differences in crown height and wear patterns. FAUNA AND FLORA IN DOMINICAN AMBER POINAR, George O., Jr., Dept. of Entomological Sciences, Univ. of CA, Berkeley, CA., 94720. The process of amberization (chemical and physical changes which result in die formation of amber from freshly exuded plant resins) is one of the most pristine forms of fossilization, with entombed organisms often closely closely resembling their original condition. During a faunal and floral survey of inclusions in amber from the Dominican Republic, representatives of 5 animal phyla (including 12 classes, 42 orders, and 295 families) and 2 plant kingdoms (including 6 divisions, 8 classes, and 16 families) were recovered. Amongst these are some rare fossils that are ordinarily not preserved by the more traditional methods of fossilization and have not been found in more nordierly amber deposits (Baltic, Canadian, Alaskan, etc.). These include tropical angiosperm flowers and the fruiting stages of various fungi, including the first identifiable fossil mushroom (Agraracales). Rare invertebrates include terrestrial gastropods: the first known fossil Zorapteran, Zorotypus paleus; the first Tertiary representative of the order Solpugida, Haplodontus proterus; the first known fossil Allantonematid (Nematoda) parasites of insects and the first known fossil cases of mite parasitism (Erythraedae) of adult moths (Lepidoptera). Among vertebrate fossils in Dominican amber are included the best preserved fossils of the lizards, Anolis and Sphaerodactylus, bird feathers and mammalian hair (containing parasitic listrophorid mites and staphylinoid beetle larvae. These vertebrate fossils represent the earliest recod of these groups in the West Indies. COCCOLITH CRYSTALLOGRAPHY AND COCCOSPHERE CONSTRUCTION IN BRAARUDOSPHAERA BIGELOWI—A MODEL FOR INTRACELLULAR BIO- MINERALIZATION. RUNNEGAR, Bruce, Dept. of Earth and Page 8 Abstracts 1990 California Paleontology Conference Space Sciences and Institute of Geophysics and Planetary Physics, Univ. of CA, Los Angeles, CA 90024 The coccosphere of the "living fossil" Braarudosphaera bigelowi is a regular dodecahedron formed of twelve equal-sized plates called pentaliths. Each pentalith is composed of five pie-shaped pieces of calcite set at approximately 72° to each other. The surfaces of the segments correspond to the calcite form {10-14} and the c axes of the crystals are consistently inclined in a counter-clockwise array in planes which lie perpendicular to one of the five segment junctions. These junctions do not coincide with a low-index lattice direction. B. bigelowi appears to be derived from Early Cretaceous species which had star-shaped pentaliths formed of five {10-14} rhombohedra. Truncation of the points of the star to produce the pentagonal pentalith of B. bigelowi was apparently achieved by making use of the fact that the {10-10} direction is almost coplanar with the {10-14} lattice direction of the adjacent segment. The 58° bevel of the proximal edges of each pentalith which is required in the assembled coccosphere may have developed from initial crystallographic angles of 69° {10-10} and 75° {10-14}. By analogy with well-studied living haptophytes, it is probable that the architecture of the pentaliths of B. bigelowi is specified by an organic baseplate or "scale". This base-plate is likely to have quasi- pentameral symmetry, a structural component formed of carbohydrate and cellulose, and a calcium-binding component which may either be a carbohydrate or a protein rich in acidic amino acids. The dodecahedral form of the coccosphere and its automatic assembly on the cell is a consequence of the pentameral shape of its components. Thus the evolutionary origin of the dodecahedral coccosphere of B. bigelowi and the extraordinary longevity of this "species" are ultimately due to the nature and properties of the mineral calcite. SEXUAL DIMORPHISM IN FOSSIL POPULATIONS: THE RANCHO LA BREA HORSE THROUGH TIME SCOTT, Eric and GUST, Sherri, George C. Page Museum of La Brea Discoveries, 5801 Wilshire Blvd., Los Angeles, CA, 90036 The Rancho La Brea (RLB) asphalt deposits in Los Angeles, California are the world's richest concentration of terrestrial late Pleistocene fossils. Specimens representing more than 140 individuals of extinct horse have been recovered from the "tar pits" to date; most of these have been assigned to the taxon Equus cf. E. occidentals Leidy 1865. A statistical analysis of measurements of the third metacarpel and metatarsal (Willoughby, 1948) suggested a bimodal distribution using the metapodial caliber index, or MCI (minimum width shaft/ articular length x 100). This bimodality was attributed to the effects of "sexual differentiation". At that time, radiometric chronostratigraphy was not available for RLB deposits. The present study uses linear measurements of metapodials grouped by radiometric age. Univariate statistical analysis of the MCI reveals normal distributions for all time periods. In addition, results show a trend toward increasing geometric volume of metapodials (highly correlated with overall body size) from 32-20ka. A similar (though not significant) pattern is observed in the MCI. When the metapodial sample is treated as a single population, this change in body size through time increases the sample variance and confounds analysis of the distribution of the MCI. Evidence indicates no sexual dimorphism in the sample of metapodials from RLB Equus. Investigations of sexual dimorphism in fossil populations must take into account changes in size and morphology through time. Willoughby, D.P., 1948. A statistical study of the metapodials of Equus occidentalis Leidy. Bull. So. Cal. Acad. Sci., 47:84-94. HARDMASS SCALING AND CONSTRUC- TIONAL EFFECTIVENESS IN FORAMIN- IFERA: PALEOBIOLOGICAL IMPLI- CATIONS SONG, J. Yan, Dept. of Integrative Biology and Museum of Paleontology, Univ. of CA, Berkeley, CA, 94720 A quantitative study of foraminiferal morphology, which involves image analyzing and statistical testing, has yielded some interesting results: (1) In general, hardmass scaling in foraminifera follows the universal form of the allometric equation, i. e. Y = a Xb. (2) Various groups differ in terms of shell constructional effectiveness (volume of chamber space created with unit amount of shell material), external irregularity (ratio of surface to volume), and internal complexity (ratio of interior area to chamber capacity). (3) Planktonic foraminifera use significantly less shell material, and are structurally simpler than benthic types. (4) Agglutinated tests occupy the other end of the constructional spectrum, using more shell material by volume and having higher structural complexity. (5) The non-mineralized organic test appears to reflect a low level of 1990 California Paleontology Conference Abstracts Page 9 architectural sophistication. (6) An extensive variability occurs in test construction of the perforate type, which may contribute to understanding the broad evolutionary success of the suborder. A GIANT ARMADILLO (PAMPATHER- IINAE, EDENTATA) FROM THE MIO- CENE LA VENTA FAUNA OF COLUMBIA THEODOR, Jessica, M., Museum of Paleontology, Univ. of CA, Berkeley, CA, 94720. Pampathere material from the La Venta fauna consists of two partial crania, several mandibles, isolated teeth, osteoderms, and considerable numbers of postcranial elements. This material represents a new taxon (description in prep.), not Kraglievichia. This taxon is the oldest well-known pampathere. Its morphology is conservative, although the astragalo- calcaneal articulation is unusual and unlike that of later forms. While the size of this form is comparable to that of Kraglievichia, its osteoderm morphology is keeled, lacking the characteristic ornament of Kraglievichia. The La Venta fauna is generally put in the Friasian land mammal age, but recent work on the fauna by Kay et al. suggests that the fauna may be Santacrucian in age. The fauna is distinctive and contains a large number of species known only from these localities.