NAPC 2001

Abstracts, Ag - An
(5/17/01)

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THE SIGNIFICANCE OF HIGHLY VARIABLE CONCENTRATIONS OF DECAPOD FINGERS: A COMPARISON OF THE PALEOECOLOGY, TAPHONOMY, AND SEDIMENTOLOGY OF SEVERAL AMERICAN NEOGENE DEPOSITS

AGNEW, Jeffrey G., Dept. of Geological Sciences, University of Florida, Gainesville, FL, USA; Roger W. Portell and Douglas S. Jones, Florida Museum of Natural History, University of Florida, Gainesville, FL, USA; and Carol M. Tang, California Academy of Sciences, San Francisco, CA, USA

A number of studies have documented the taphonomy and infrequent occurrence of whole-bodied decapods, with various explanations being offered for their preservation or lack thereof. However, little research has been conducted on the ubiquitous and often abundant decapod cheliped segments in shelly deposits. Such remains represent nearly all of the known decapod taxa from the Neogene of Florida and considerably more taxa are waiting to be identified. Even less is understood about the taphonomic, paleoecological, and sedimentological context of deposits with decapod fingers. The circumstances that lead to the destruction of whole-bodied crabs may favor the preservation of their heavily calcified and highly resistant fingers. Therefore, any model of decapod taphonomy should encompass all states of preservation and not just the most extraordinary.

Do unusual densities of decapod chelipeds require unique environmental conditions that allow for their preservation or do they simply reflect large populations? Of course, it seems probable that both are required, but whether one exerts a greater influence over the other is uncertain. This presentation explores specific factors that may control the occurrence, abundance and condition of decapod fragments in shell beds and other deposits. The paleoecology, taphonomy, and sedimentology of nine shell beds in a Plio-Pleistocene section from south-central Florida with an unusually dense concentration of decapod fingers is compared to other formations with differing abundances of decapod parts. These include select deposits from the Miocene of northwest and north-central Florida and the Dominican Republic, the Pliocene of southern Florida, and the Pleistocene of Baja California, Jamaica, and southern Florida. The influence that seagrass, callianassid shrimp, sediments, and depositional processes have on the occurrence and preservation of decapod parts will be discussed.

NEW FINDINGS OF CAPRINID RUDISTS (BIVALVIA-HIPPURITACEA) IN THE CERRO DE LABRADORES, STATE OF NUEVO LEÓN, MÉXICO

AGUILAR, Javier P., and Yolanda B. Pichardo, Facultad de Ciencias de la Tierra, Universidad Autónoma de Nuevo León, México

The Cerro de Labradores is located in the west central part of the State of Nuevo León, and belongs to the northeastern part of the Sierra Madre Oriental. The reefal facies of the Cupido Formation (Imlay, 1937) outcrops in vast areas of this region. This lithological member was identified by Padilla-Sánchez (1978), noting the abundance of monopleurid, requienid and caprinid rudists, associated with oysters, fragments of corals and other organisms. Johnson (1984) made a detailed study of the lagunal facies of the Cupido and El Abra Formations, describing the requienids at specific levels. The authors found in this locality many specimens of the following species of caprinid rudists: Amphitriscoelus waringi Harris and Hodson, Caprina douvillei Paquier, Praecaprina varians Paquier and Offneria simplex Chartrousse and Masse. The last three species are reported for the first time from Mexico. These speciesare also present in other localities of the American Province of the Tethys Realm, like Trinidad, Venezuela, Cuba and Texas. Amphitriscoelus waringi is an endemic species of this province. The other three species exist also in the Mediterranean Province of the Tethys Realm. The four species are well known as indicative of early Aptian age. On the other hand, the sedimentary sequence of the Cupido Formation, which is lower Aptian, was already determined by Padilla-Sánchez (1978, 1982) on the basis of the presence of Nannoconus bermudezi Kamptner and N. elongates Bronnimann.

LOWER TERTIARY LARGER FORAMINIFERA FROM PAKISTAN

AKHTAR, Muhammad, Geological Survey of Pakistan, Lahore, Pakistan; and Aftab A. Butt, Institute of Geology, Punjab University, Lahore, Pakistan

Age-diagnostic benthonic larger foraminifera have been recorded mainly from the Upper Paleocene and the Lower Eocene succession represented dominantly by the carbonate platform deposits. The Middle Eocene in northern Pakistan is essentially a red bed facies with some fossiliferous interbeds. This sequence is overlain by a stratigraphic unit developed as bank facies. Stratigraphically important foraminiferal species are Miscellanea miscella (d'Archiac & Haime), Lockhartia haimei (Davies), Lockhartia tipperi (Davies), Lockhartia conditi (Nuttall), Ranikothalia sindensis (Davies), Ranikothalia nuttalli (Davies), Actinosiphon tibetica (Douville), Operculina patalensis Davies & Pinfold, Operculina salsa Davies & Pinfold, Operculina subsalsa Davies & Pinfold, Assilina dandotica Davies & Pinfold, Assilina spinosa Davies & Pinfold, Assilina subspinosa Davies & Pinfold, Assilina laminosa Gill, Assilina granulosa (d'Archiac), Assilina exponens (Sowerby), Discocyclina ranikotensis Davies & Pinfold, Discocyclina dispansa (Sowerby), Nummulites mamillatus (Fichtel & Moll) and some alveolinids. Bioclastic wackestone, packstone and the grainstone microfacies are developed in these shallow-marine, shallow shelf deposits. The Paleocene-Eocene can be distinguished by the appearance of Assilina granulosa (d'Archiac), Discocyclina dispansa (Sowerby), Nummulites mamillatus (Fichtel & Moll) and the alveolinids. Miscellanea miscella (d'Archiac & Haime) is mostly found in Paleocene strata worldwide but its reported occurrence in the Lower Eocene has been substantiated in southern Pakistan in the Murree-Brewery Gorge around Quetta.

TOWARD A REVISION OF THE CHRONOSTRATIGRAPHY OF THE JOHN DAY FORMATION, OREGON

ALBRIGHT, L. Barry, Museum of Northern Arizona, Flagstaff, AZ, USA; Theodore J. Fremd, John Day Fossil Beds National Monument, Kimberly, OR, USA; Michael O. Woodburne, University of California, Riverside, CA, USA; Carl C. Swisher, Rutgers University, Piscataway, NJ, USA; and Bruce J. MacFadden, Florida Museum of Natural History, Gainesville, FL, USA

Although the Whitneyan, Arikareean, and Hemingfordian North American Land Mammal "Ages" were first typified in the Great Plains, the succession there contains significant unconformities, a generally poor magnetic record, relatively sparse radioisotopic calibration, and a major faunal hiatus within the Arikareean. In the John Day Valley of central Oregon, however, is a thick, remarkably complete sequence of Oligocene-early Miocene strata (the John Day Formation) highly amenable to addressing these shortcomings and long known to harbor one of the richest records of mid-Tertiary mammals in North America.

Although Prothero and Rensberger conducted the first magnetostratigraphic study of the John Day in 1980, new advances in geochronology call into question the validity of those early results. In our recent attempt to reinvestigate John Day chronostratigraphic relationships, we sampled nearly 300 sites for magnetostratigraphy over 500 meters and sampled several tuffs for ⁴⁰Ar/³⁹Ar dating. Our preliminary study indicates that the Turtle Cove Member stratigraphically upward through the lower Kimberly Member extends from chron C12n to C7n.2n, or from about 30.5­24.9 Ma. However, the rocks we sampled showed unusual behavior characteristic of a complex magnetic mineralogy in contrast to rocks in which the primary remanent magnetization is carried in magnetite whereby a well defined polarity determination and magnetic direction result. We also found several intervals of anomalously long normal polarity for this time period based on our preliminary dating of associated tuffs. Our preliminary correlation together with the mammal fauna of the lowermost interval suggests that the Arikareean began nearly 1 m.y. earlier in the Pacific Northwest than in the Great Plains.

Studies currently in progress are addressing these problems and will also provide a temporal framework that will allow reappraisal and refinement of the correlation between the classic mammalian faunas of the Northern Great Plains and the John Day region.

LATE HOLOCENE RECORDS OF INVERTEBRATE DIVERSITY AND TURNOVER FROM LAKE TANGANYIKA, EAST AFRICA, AND THEIR CONSERVATION IMPLICATIONS

ALIN, Simone R., Andrew S. Cohen, and Heather D. Heuser, Dept. of Geosciences, University of Arizona, Tucson, AZ, USA; and Manuel R. Palacios-Fest, Terra Nostra Earth Science Research, Tucson, AZ, USA

Lake Tanganyika is a global hotspot of freshwater biodiversity, with ~2000 described species and high levels of endemism, and is located in a region with rapid human population growth. Nearshore benthic communities are the most diverse and the most susceptible to anthropogenic habitat alteration. Ostracods serve as conservative paleoecological indicators of change in benthic communities, because they have a higher response threshold to sediment inundation than fish and molluscs. Ostracods are preserved in sediment cores in sufficient abundance to allow high-resolution reconstruction of biodiversity turnover through the recent period of intensive land-use change in the lake's watersheds.

Using detrended correspondence analyses (DCA) of ^14C- and ²¹⁰Pb-dated fossil ostracod assemblages, we compared recent diversity trends in numerous sediment cores collected offshore from watersheds experiencing various degrees of deforestation. Offshore from deforested watersheds, sediment accumulation rates increased by a factor of two- to ten-fold over the last c. 150 years with rate increases triggered by high rainfall (El Niño) events. Cores near highly disturbed, large watersheds showed paleoecological trends toward decreasing species diversity and increasing dominance relative to historical conditions at the same sites. Intermediate disturbance conditions are often correlated with slightly higher ostracod diversity in living assemblages than at undisturbed sites. In cores from moderately disturbed areas, DCA revealed progressive change in ostracod assemblages through time, although overall species richness and levels of dominance did not change (often the identity of dominants did). In cores from undisturbed areas, no major transitions in the ostracod fauna occurred.

Paleoecological records of microinvertebrate diversity at sites around Lake Tanganyika suggest that localized recent transitions in species composition of benthic communities can be ascribed to anthropogenic alteration of the lake habitat.

SPECIES-LEVEL EVOLUTION OF AMMONOID SUTURE COMPLEXITY: PASSIVE OR DRIVEN?

ALLEN, Emily G., Committee on Evolutionary Biology, University of Chicago, Chicago, IL, USA

Recently, many patterns historically interpreted as evolutionary trends have been re-evaluated to discriminate between two possible underlying mechanisms: passive diffusion away from morphological bounds or active directional selection. Yet few studies address how analytical biases, such as taxonomic window, affect interpretations of these patterns. Here, I examine some of these issues by contrasting species- and genus-level analyses of the evolution of ammonoid suture complexity.

Genus-level analysis of the evolution of Paleozoic ammonoids provides strong evidence for a driven trend toward increased suture complexity over time (Saunders & Work 1997; Saunders et al. 1999). In contrast, results from tracking species-level changes in the Prolecanitida, an order of Paleozoic ammonoids, are more consistent with the passive diffusion model. Over the 100 m.y. prolecanitid duration, species show a 1400% increase in mean suture complexity as a consequence of a highly increased variance. This increase is correlated with the loss of simple-sutured species; however, there is no steady attrition of less complex forms as was reported for genera. Instead, average minimum complexity remains constant within families and there is a stepwise loss associated with the extinction of higher taxonomic groups. Changes in suture complexity across stratophenetic ancestor-descendent (A-D) pairs show a minor, non-significant preference for increases (n=87) over decreases (n=72). Among species, the mean magnitude of increases (45.5%) is twice that of decreases (21.8%). Large increases in complexity are associated with the rise of new genera; this observation may help to resolve the species-level results with the significant bias in genus-level prolecanitid A-D pairs for increases (n=28) over decreases (n=6). As both the loss of simple-suture species and the appearance of highly differentiated forms coincide with the rise of new genera one would expect the trend to appear driven at higher taxonomic levels, regardless of the species-level behavior.

TURRITELLID GASTROPODS OF THE NEOGENE OF THE NORTHERN DOMINICAN REPUBLIC: A ROSETTA STONE FOR THE MID-LATE CENOZOIC WESTERN ATLANTIC HISTORY OF THE GROUP?

ALLMON, Warren D., Paleontological Research Institution, Ithaca, NY, USA

Gastropods of the family Turritellidae are rare overall in Neogene sediments of the northern Dominican Republic, although they are occasionally locally abundant. They are also relatively un-diverse, with only three species having previously been recognized: Turritella planigyrata Guppy 1867, T. tornata Guppy 1866, and T. submortoni Maury 1917 (which may be synonymous with planigyrata). ("Turritella" is used here sensu lato.) Yet the occurrence of the group in these well-sampled exposures may provide important information about its biogeographic, phylogenetic, and paleoenvironmental history. T. tornata appears to belong to a clade that includes T. rina Palmer 1937 and its relatives from the Eocene and Paleocene of the US Gulf Coastal Plain, as well as several taxa in the later Neogene of Florida and elsewhere, including the abundant T. perattenuata Heilprin 1887 and the Recent T. exoleta Linnaeus 1758. T. planigyrata may belong to a clade that includes T. mortoni Conrad 1830 from the Paleocene of the Gulf Coast and its Paleogene relatives. Its later relatives remain unknown. Preliminary analysis of the paleoenvironmental distribution of turritellids in the Domincan sequence suggests that it may document part of the transition from a more thermophilic pattern that characterized the group earlier in its history to a more frigiphilic and nutriphilic habit that characterizes and controls its distribution later.

THE PALEOBIOLOGY DATABASE

ALROY, John, NCEAS, University of California, Santa Barbara, CA, USA

The Paleobiology Database is a five-year, NSF-funded initiative to build an open, World Wide Web-based resource for the paleontological community. The Database currently includes 50 Ph.D.s and 19 students from 33 institutions; any professional researcher who wants to contribute data may join. Researchers enter, edit, and analyze data over the Web.

We also plan to develop Web-based data sharing protocols with other databases. The Paleobiology Database originated in the Phanerozoic marine paleofaunal diversity project (1998­2000), which was funded by the National Center for Ecological Analysis and Synthesis (NCEAS). This initiative, which seeks to produce a sampling-standardized Phanerozoic diversity curve using rigorous statistical techniques, continues as the Paleobiology Database marine working group. It has so far compiled data on 10,076 Neoproterozoic-Paleogene fossil collections that are made up 118,821 taxonomic occurrences, mostly from North America and Europe. Three new working groups for paleobotany (discussed later in the symposium), vertebrates, and taphonomy have been established. The vertebrate group's initial goal is to quantify large-scale sampling intensity patterns by databasing a randomly drawn subsample of the literature. The group also will bring together existing data sets: the North American Mammalian Paleofaunal and Fossil Mammal Systematics Databases; a global data set on dinosaurian taxonomy, phylogeny, and body size; detailed occurrence data on Karoo vertebrates; and additional data on both terrestrial and marine Mesozoic and Cenozoic vertebrates. The taphonomy group bridges the others and seeks to quantify large-scale taphonomic patterns in the record. All four groups meet periodically at NCEAS. Preliminary results concerning three research areas will be discussed: removing the effects of sampling intensity bias from estimates of diversity using occurrence data; analyzing abundance distributions using specimen count data; and modelling the dynamics of evolutionary trends using phylogenetic and morphometric data.

ENVIRONMENTALLY ASSOCIATED ALLOMETRY AND SIZE TRUNCATION IN NEOGENE CARYOCORBULA OF THE NORTHERN DOMINICAN REPUBLIC

ANDERSON, Laurie C., Dept. of Geology and Geophysics, Louisiana State University, Baton Rouge, LA, USA; and Peter D. Roopnarine, Dept. of Invertebrate Zoology and Geology, California Academy of Sciences, San Francisco, CA, USA

Richly fossiliferous Neogene deposits of the northern Dominican Republic have been a source of taxa for numerous evolutionary studies over the last two decades. A reexamination of Dominican Caryocorbula from this area using landmark-based techniques, relative warp analysis and canonical variates analysis reveals better separation among morphologies than is achieved with traditional measures and principle components analysis. At least three species can be recognized. As is common in Neogene Caryocorbula of tropical America, a strong allometric trend is apparent among species. Because species distributions are strongly facies dependent, this allometric trend is correlated with an environmental gradient. Larger, elongate Caryocorbula occur in marginal- to very shallow-marine deposits (<30 m). Intermediate-sized subtriangular Caryocorbula occur in sediments deposited in shallow-water (also <30 m) with a fully marine salinity. The smallest Caryocorbula, which are triangular, are found in sediments deposited in water of intermediate depth (30­100 m). Caryocorbula in deeper-water deposits (>100 m), however, are the same shape as, but are larger than, those found in intermediate depths.

These Dominican sections one of the few molluscan-rich shallow-marine units of Messinian and Zanchlean age that are well documented in tropical America. In these uppermost Miocene to lower Pliocene sediments, the earliest evidence of a dramatic size decrease in Caribbean Caryocorbula is recorded. This size minimum does not appear to be facies related or taphonomicaly based. The size minimum does not appear to have affected all corbulids, however, and large-bodied Bothrocorbula are locally abundant in the upper Miocene Cercado Formation. The size decrease in Caryocorbula appears to be triggered by a productivity collapse associated with emergence of the Isthmus of Panama that also warmed the Caribbean and made it more carbonate rich.

RESURRECTION OF AN OLD WORLD FOSSIL, THE ECHINOID, MELONECHINUS MULTIPORUS

ANGELI, Nicholas, Patricia Eicks, and Bruce L. Stinchcomb, Dept. of Geology, St. Louis Community College at Florissant Valley, St. Louis, MO, USA

Some historically significant, paleontological wonders once described in the rudimentary firsts of documented literature often remain silent, throwing up no barriers of questionable origin, affiliations or misinterpretations. They remain dormant and undaunted as the world of paleontology grew up around them, leaving only a trail of unparalleled enchantment for us to follow.

Melonechinus Meek and Worthen 1860 (Melonites Norwood and Owen 1846) is one such fossil. Described by J.G. Norwood and D.D. Owen through the Transactions of the Saint Louis Academy of Science after a visit to Saint Louis in the winter of 1844­1845. Three specimens were recovered from near low water mark along the Mississippi River from the Limestone Formation of what is presently known as the St. Louis Formation, Mississippian or Lower Carboniferous Period. Additional discoveries were later made in the old north city sections. These yielded specimens of the cantaloupe-shaped echinoid made famous by their discovery as a biostrome in a quarry. Workman noted their unusual shape and commonly referred to them as coltsfoot in reference to the resemblance of the frog of a horse's foot.

Minor taxonomy problems were worked out by paleontologists such as Agassiz, McCoy, Jackson, Jaggar, Keys, and of course Meek and Worthen. These Victorian paleontological dilemmas started at the class level and included the inclusion of echinoids with the Crinoidea. Early thinking suggested that echinoids were attached by a pedicel stalk or jointed columns, simply because some washed in crinoid stems were consolidated with the specimens. Almost all other systematical descriptions had to do with the number and arrangement of ambulacral plates and pores. Later works solved problems at the species level eventually settling at fourteen species by 1910.

In 1860 Meek and Worthen renamed the genus Melonechinus from Melonites to which Lamarck first applied the name (Melonites) for the genus Polypi (an anthozoa) thus retaining the name if so needed.

PHYLOGENETIC AND BIOGEOGRAPHIC IMPLICATIONS OF PERMIAN DICYNODONTS FROM RUSSIA

ANGIELCZYK, Kenneth D., Dept. of Integrative Biology and Museum of Paleontology, University of California, Berkeley, CA, USA

Anomodont therapsids have been known from Russia since the first half of the 20th century. Most research on these forms traditionally focused on Permian basal anomodonts such as Otsheria, Ulemica, and Venyukovia or derived Triassic dicynodonts similar to Kannemeyeria. However, several recently described Permian dicynodonts show clear differences from their Gondwanan contemporaries, indicating that Eastern Europe may have been an area of considerable endemism for dicynodonts.

To examine the relationships of the Russian dicynodonts, a cladistic data matrix was constructed of six Russian taxa and 18 genera known predominantly from South Africa. Forty-six morphological characters were coded and Patranomodon and Otsheria were used as outgroups to root the most parsimonious cladograms. The results of this analysis suggest that the Russian taxa Elph and Interpresosaurus form a clade that is the basal sister of the clade including taxa such as Dicynodon, Kannemeyeria, Oudenodon , and Aulacephalodon. Also, Dicynodon, Lystrosaurus, and Kannemeyeria nest within a clade including the Russian taxa "Dicynodon" trautscholdi, Delectosaurus, and Vivaxosaurus. Vivaxosaurus is reconstructed as the sister group of Kannemeyeria.

These results are interesting because they are compatible with a Russian origin of many South African dicynodont genera. However, at the current level of taxon sampling, it is equally parsimonious to posit dispersal into Eastern Europe by South African taxa. Stratigraphic information could help resolve this uncertainty, but correlations between Russia and South Africa are poor. Further phylogenetic and stratigraphic studies will be necessary to test the hypotheses presented here, but these results emphasize that the South African fossil record does not preserve the full history of dicynodont evolution in the Late Permian.