The Paleogene of Wyoming and Montana and the Neogene Siwaliks of Pakistan contain deposits representing a wide variety of terrestrial environments. Although fossils are preserved in all of these environments, fossil vertebrates are abundant in only certain facies. These principal preservational environments vary within and, particularly, between formations in each region.

The Bighorn and Crazy Mountain basins of Wyoming and Montana contain abundant remains of Paleocene and Eocene vertebrates. Over 1800 localities in this region have been established in the Paleocene Fort Union and Paleocene to Eocene Willwood formations. The distribution of vertebrate remains changes dramatically upsection in this sequence. The Fort Union consists of thick fluvial sandstones and minor swampy floodplain mudstones in the lower part, and more widely separated channel sandstones interbedded with better drained floodplain deposits that include paleosol horizons in the upper part. These changes reflect a local increase in aggradation rate. Vertebrates are preserved almost exclusively in channel mud-clast conglomerates in the lower part of the formation, but appear in a wider variety of environments (channels, splays, swamps, and paleosols) in the upper part. The Willwood Formation continues the changes evident in the upper Fort Union. With increased aggradation rates, floodplain deposits became thicker and more well drained. Except for rare occurrences in other environments (channels, a variety of calcareous environments, and oxbows), fossils are recovered primarily from paleosol horizons developed in fine grained floodplain deposits.

The Fort Union channel deposits contain assemblages that are often highly biased samples of faunal composition with large aquatic taxa well represented and small terrestrial forms unevenly represented. The upper Fort Union and Willwood floodplain paleosols contain more homogeneous (and therefore comparable) assemblages. These paleosols differ systematically, however, in terms of soil maturity and vertebrate composition, and they are commonly biased against large or aquatic taxa.

The distribution of Siwalik vertebrate localities among sedimentary environments is known for four formations spanning early middle to late Miocene: Kamlial, Chinji, Nagri, and Dhok Pathan. The principal deposits in which fossils occur are: major stream channel complexes, secondary (floodplain) channels, crevasse splays, and floodplains. The Kamlial and Nagri formations, dominated by coarse lithologies (>50% sandstone), are notably less productive of fossil localities than the Chinji and Dhok Pathan formations, dominated by fine grained lithologies (>50% mudstone). In the Kamlial and Nagri formations, major channel complexes form the most prevalent environment, and more localities are associated with these channels than with any other environment. In the Chinji and Dhok Pathan formations, the most prevalent environment is floodplain, but more localities are associated with the secondary channels on these floodplains than with any other environment. In the Chinji Formation, most localities developed in secondary channels occur in fining-upward fill sequences, whereas in the Dhok Pathan Formation, most sites in these channels occur in their lag deposits. In these more productive formations, the abundance of certain mammalian taxa is correlated with specific depositional environments. Change upsection in the abundance of these taxa could result largely from change in facies productivity.

The taphonomy of the two areas is similar in that channel lag deposits are an important source of fossil vertebrates. The major difference is that the Rocky Mountain Paleogene contains fewer, but highly productive, environments that changed significantly through time, including the Eocene emergence of floodplain paleosols as the primary environment of vertebrate preservation.

The marine vicariant event resulting from the Pliocene emergence of the Central American Isthmus presents a unique opportunity for calibrating rates of molecular evolution. The synchronous fragmentation of the ranges of previously widespread taxa into Western Atlantic and Eastern Pacific components (geminates) enables one to make comparisons of rates among higher taxa on the same time scale and to evaluate the regularity of rates of molecular evolution among all species sampled. Other advantages of this approach are that the time scale (approximately 3 Ma) is one of particular interest for evolutionary biologists concerned with speciation and one that minimizes the ambiguities associated with augmentation of divergence values to account for multiple hits at a site. The divergence values derived for geminate pairs are independent, allowing statistical evaluation of variance in rates.

The current popularity of the relative rates test as the final arbiter of questions regarding rates and rate variation is primarily a matter of convenience and not a reflection of methodological superiority. A review of the commonly used techniques for calibrating rates of molecular evolution shows that each approach has limitations. Temporally based calibrations of rates are necessary complements to time-independent comparisons.

Interpretation of transisthmian molecular comparisons in the literature have in many cases been unduly influenced and confused by molecular clock assumptions and the restriction of studies to single higher-level taxa. Analysis of the apparently contradictory published data as well as new results from sequence comparisons of fishes, urchins and snails suggests a synthesis: taxon specific rates of molecular evolution, with reduced variance within taxonomic groups and great variance among all groups sampled.

Biological parameters, in addition to physical parameters, are important in determining past ecology, taphonomy and the effects of human intervention. Research conducted on a Recent community of gastropods and two late Pleistocene fossil assemblages from Puerto Penasco, Mexico, reveal a complex pattern of interrelationships among gastropod shell users. First, shell representation is biased in the intertidal of Puerto Penasco, Mexico, because of a complex mosaic of secondary shell occupants. Hermit crabs (five species) represent almost half (47%) of the intertidal gastropod shell resource available throughout the year. Living snails are represented by 17 out of the 32 gastropod taxa. Additionally, hermit amphipods (three species) occupy ten gastropod taxa. Hermit crabs and hermit amphipods retain the shells in anomalous habitats (that differ from the living snail). Second, physical factors act as a temporal component which affects shell use and availability during the seasons at Puerto Penasco. Late winter storms mix-up the intertidal distribution of living gastropods and hermit crabs. Subtidal to low intertidal shells appear in the high intertidal; living snails are buried under a thick bed of sand. Most importantly, empty shells become available, and the hermit amphipod population peaks. Thus, physical factors contribute to the demise of living snails (i.e, burial by sand) and the mixing of shells. However, the organisms (hermit crabs and amphipods) maintain this motif by retaining the shells in the anomalous habitats.

Third, all hermit crab species (Paguristes anahuacus, Pagurus lepidus, Paguristes roseus), except for one (the high intertidal, Clibanarius digueti), have epi-and endobionts associated with the gastropod shell. More than 20 species of invertebrates bore into or encrust the hermitted shells at Penasco. Of these, the encrusting bryozoans Hippothoa, Hippopodinella adpressa, ?Floridia antiqua, Lichenopora, Antropora tincta and the boring spionid polychaetes (Polydora commensalis, Polydora, Boccardia) and spirorbid polychaetes (Spirorbis; Serpula) are important bionts to use in recognizing hermit crab shell use in the fossil record of the northern Gulf of California. The encrusting bryozoans (H. adpressa and A. tincta) are present on Pleistocene gastropods at the unusual Pelican Point terrace deposit (large gastropod shells preserved among large bryozoan encrusted cobbles) indicating hermit crab inhabitation. These bryozoans appear to protect the gastropods from taphonomic alteration.

Finally, reworked fossil shells occur within the hermit crab guild and the beach drift assemblage. Hermit crabs retain fossil shells of the moon snail, Polinices, (n=two occurrences) and Turritella (n=3 occurrences). These species are common in the coquina beach rock which makes up the intertidal substrate of Puerto Penasco. However, reworking of fossil coquina is quite substantial in the beach drift assemblage. Three sampling periods (=150 samples) indicate the following: three species of fossil bivalves (Chione, Trachvcardium and Glycimeris) and five species of fossil gastropods (Oliva, Polinices, Muricanthus, Nassarius, and Turritella) dominated the beach drift assemblage (over 16, 600 fossil whole shells/fragments). Fossil Chione represented the most shells (958 valves;>15,557 fragments). Recent bivalves were represented by 1115 shells/fragments (representing 12 species) and Recent gastropods contained mostly fragments (1069 pieces; 30 species). Additionally, the fossil gastropods were large, unlike the species that occur today, which have been picked over by humans. Thus, a large part of active beach deposition at Puerto Penasco contains late Pleistocene shells, taphonomically altered by secondary occupants and beachcombers.

In 1962 Zuckerkandl & Pauling suggested that the amino acid sequence of proteins might evolve in a clock-like fashion and thus may be useful for phylogenetic reconstruction. Since then, many different molecular approaches to phylogenetic reconstruction have been proposed (Wilson et al., 1977). Enthusiasm for the clock hypothesis was dampened by the discovery that rates of molecular evolution for many macromolecules have been highly variable through time (Romero-Herrera et al., 1979). However, the contribution of molecular characters to the study of phylogeny is not necessarily dependent on the notion of a molecular clock and molecular approaches continue to be an important source of phylogenetic information. One of the more powerful and cost-effective molecular techniques for phylogenetic purposes is DNA-DNA hybridization, which measures the single-copy nuclear DNA sequence divergences between species.

Paleontological studies can bring to light two important aspects of the speciation process: long term patterns of morphological change, and the paleoenvironmental context of such changes. We examined the temporal patterns of morphological change and their geographic and paleoenvironmental context in species of Prunum (Marginellidae; Gastropoda) from the Neogene of the northern Dominican Republic. We document a speciation event from P. coniforme (Sowerby 1849) to P. christineladdae (Maury 1917) which is unusual in both its temporal expression, and in the relative clarity of the ecological setting for speciation.

We believe that the changes in morphology from P. coniforme to P. christineladdae represent a speciation event. The two species are distinguished by several shell features, including overall shape, spire height, relative height of the top of the lip, and apertural denticulations. The nature and magnitude of these differences, compared with morphological differences among extant species of Prunum, indicate that separate species designations are warranted for P. coniforme and P. christineladdae. A sequence of stratigraphic and morphological intermediates between these species provides strong stratophenetic evidence for speciation.

The stratigraphic interval characterized by intermediate morphologies includes approximately 22 m of section. Sedimentation rates yield estimates of approximately 73,000–275,000 years for our interval of morphologic change. This transitional interval represents between 0.6–2.5 % of the total duration of the ancestral species.

The patterns of morphological change exhibited by the two species generally fit the predictions of punctuated equilibrium; change from ancestor to descendent is relatively rapid, outside the transitional interval species exhibit no directional morphologic trends, and the ancestral species persists after speciation.

Our data reveal some information on the mode of speciation. Prunum species from our study area exhibit well-defined depth ranges. P. christineladdae occurs only in deep water deposits, whereas P. coniforme is common in shallow water deposits. Based on distributional data, we suggest that depth, or one or more of its associated variables, was critical to the isolation and evolution of P. christineladdae.

This important group of ornithischian dinosaurs has a history that extends from the Early Jurassic until the close of the Cretaceous Period. The group as a whole can logically be subdivided into three quite distinct lineages: the heterodontosaurs, the hypsilophodonts, and the iguanodonts. I shall discuss the attributes of these groups separately, so that direct comparisons can be drawn by the reader of the way in which ornithopods as a whole evolved and diversified during the latter part of the Mesozoic. However, before going on to deal with these individual groups of ornithopods in a little more detail, I shall briefly outline their history and degree of relatedness.

Screen-washing bulk samples of fossilliferous matrix is the method of choice for concentrating relatively large numbers of small fossils from unconsolidated sediments. The technique is most effective when used to disaggregate dry and unconsolidated sand, silt, and silty clay. Ideally, when the dry fossil-bearing particles will pass through an appropriate size screen-mesh, leaving behind a residue of fossils and coarser grain sizes. Organic-rich sediments, overconsolidated silt, silty clay, maris and clays may require soaking in dilute chemical solutions to encourage disaggregation. The extraction of fossils from these more intractable sediments, therefore, generally will be limited to the processing of quantitatively small samples (several hundred grams), in the laboratory.

AS RECENTLY as thirty years ago, deaccessioning was a dirty word in museums. It was considered an abrogation of an institution's fundamental responsibility to care of its collections in the public trust. Miller (1985) has chronicled some of the public controversy that attended deaccessioning in the early 1970's. However, in the intervening time, museums' approach to deaccessioning has changed as they grapple with burgeoning collections, decreasing funding bases, pressure to narrow and focus their missions, and rising standards of care. Now deaccessioning is regarded by the majority as a necessary and appropriate tool in collections management, albeit one that operates within strict ethical and legal constraints.

A museum's collections policy should address criteria for deaccessioning, levels of approval needed, methods of disposition, use of funds resulting from sales, and records keeping. In addition, staff must develop procedures for identifying material for deaccessioning. In the following sections we review the currently accepted standards in the museum field for these areas, as well as discussing how some of these issues apply particularly to paleontological collections. It may be appropriate for paleontology departments to develop guidelines and procedures that further refine the museum's overall collections policy to fit the needs of their collections and the conventions of their field.

Sepkoski (1981a,b, 1988) has characterized the Cambrian fauna as unique, both in terms of taxonomic composition and in environmental distribution of taxa. Compared with the rest of the Phanerozoic, the frequency of mass extinction in the Cambrian must also rank as a distinctive feature which had a profound impact on macroevolutionary patterns. Three well-documented extinctions occurred in the Upper Cambrian of North America (Figure 1; Palmer, 1979; Westrop and Ludvigsen, 1987) and are best expressed in the trilobite faunas. Possible older extinctions may be present at the top of the Olenellus Zone and near the base of the Bolaspidella Zone (e.g., see Palmer, 1982) but more data are required.

We implemented an authentic research experience as part of the invertebrate paleontology course at University of North Carolina Wilmington to promote student learning objectives related to understanding course content, critical thinking, problem solving, and oral and written communication. This semester-long research project, worth 20% of the course grade, is incorporated into the laboratory component of the course, and employs best practices of active and collaborative learning. Students work as teams to develop and test paleoecological and/or evolutionary hypotheses using field-collected or archived bulk samples. Following sample processing, specimen identification, and data collecting and analysis, students write a research paper using the format of a professional paper, with individually and team-written parts, and present their results orally. After completion, one or more abstracts based on the results are submitted to a professional meeting. Typically, several students attend the meeting and present the posters. This approach allows students to experience authentic research from conception to dissemination. Since 2003, the course has been offered seven times, resulting in 13 published and presented abstracts. Over half the students remained involved in paleontology following the course by presenting the work or taking additional courses or independent study, demonstrating that the experience was received positively. This approach provides a model for other instructors, as the research project can be adapted to a variety of geological settings and topics. Successes and challenges in implementing such a project are discussed.

Science is so exciting! Why? Because it is awe-inspiring, fun, and creative. Most scientists would not do anything else — they are truly dedicated to what they do. You can hardly get them to be quiet once they start talking about their work. Unlike most people, they usually love their jobs! However, this is not the common view presented of most scientists. They are commonly thought of as nerds, freaks, weirdoes, or evil-doers as portrayed in movies or television. These are fantasies where, with a few exceptions, scientists are shown negatively because it fits dramatic needs (Crichton, 1999). It's just not true in real life.