Principal component analysis has been used to test for similarities in ecology and life habit between modern and fossil birds; however, the two main portions of the hind limb—the foot and the long bone elements—have not been examined separately. We examine the potential links between morphology, ecology, and phylogeny through a synthesis of phylogenetic paleoecological methods and morphospace analysis. Both hind limb morphologies and species’ ecologies exhibit extreme phylogenetic clumping, although these patterns are at least partially explainable by a Brownian motion style of evolution. Some morphologies are strongly correlated with particular ecologies, while some ecologies are occupied by a variety of morphologies. Within the morphospace analyses, the length of the hallux (toe I) is the most defining characteristic of the entire hind limb. The foot and hind limb are represented on different axes when all measurements are considered in an analysis, suggesting that these structures undergo morphological change separately from each other. Early birds tend to cluster together, representing an unspecialized basal foot morphotype and a hind limb reliant on hip-driven, not knee-driven, locomotion. Direct links between morphology, ecology, and phylogeny are unclear and complicated and may be biased due to sample size (~60 species). This study should be treated as a preliminary analysis that further studies, especially those examining the vast diversity of modern birds, can build upon.

A priori choices in the detail and breadth of a study are important in addressing scientific hypotheses. In particular, choices in the number and type of characters can greatly influence the results in studies of morphological diversity. A new character suite was constructed to examine trends in the disparity of early Paleozoic crinoids. Character-based rarefaction analysis indicated that a small subset of these characters (~20% of the complete data set) could be used to capture most of the properties of the entire data set in analyses of crinoids as a whole, noncamerate crinoids, and to a lesser extent camerate crinoids. This pattern may be the result of the covariance between characters and the characterization of rare morphologies that are not represented in the primary axes in morphospace. Shifting emphasis on different body regions (oral system, calyx, periproct system, and pelma) also influenced estimates of relative disparity between subclasses of crinoids. Given these results, morphological studies should include a pilot analysis to better examine the amount and type of data needed to address specific scientific hypotheses.

Models of functional ecospace diversification within life-habit frameworks (functional-trait spaces) are increasingly used across community ecology, functional ecology, and paleoecology. In general, these models can be represented by four basic processes, three that have driven causes and one that occurs through a passive process. The driven models include redundancy (caused by forms of functional canalization), partitioning (specialization), and expansion (divergent novelty), but they also share important dynamical similarities with the passive neutral model. In this second of two companion articles, Monte Carlo simulations of these models are used to illustrate their basic statistical dynamics across a range of data structures and implementations. Ecospace frameworks with greater numbers of characters (functional traits) and ordered (multistate) character types provide more distinct dynamics and greater ability to distinguish the models, but the general dynamics tend to be congruent across all implementations. Classification-tree methods are proposed as a powerful means to select among multiple candidate models when using multivariate data sets. Well-preserved Late Ordovician (type Cincinnatian) samples from the Kope and Waynesville formations are used to illustrate how these models can be inferred in empirical applications. Initial simulations overestimate the ecological disparity of actual assemblages, confirming that actual life habits are highly constrained. Modifications incorporating more realistic assumptions (such as weighting potential life habits according to actual frequencies and adding a parameter controlling the strength of each model’s rules) provide better correspondence to actual assemblages. Samples from both formations are best fit by partitioning (and to lesser extent redundancy) models, consistent with a role for local processes. When aggregated as an entire formation, the Kope Formation pool remains best fit by the partitioning model, whereas the entire Waynesville pool is better fit by the redundancy model, implying greater beta diversity within this unit. The ‘ecospace’ package is provided to implement the simulations and to calculate their dynamics using the R statistical language.

One of the most remarkable differences between Paleogene penguins and their living relatives is the shape and length of their beaks. Many of the Eocene and Oligocene penguins have a thin and elongated spear-like bill, which contrasts with the proportionally shorter and more robust bill of most living species. These differences suggest an important shift in their feeding strategies. This study explores the morphological disparity on the skull of penguins, emphasizing bill morphology and it relationship with feeding habits. For this, the skulls of 118 species of aquatic birds, including 21 fossil and living penguins, were analyzed using two-dimensional geometric morphometric. The results show that, unlike what has been reported for modern birds overall, in penguins and Aequornithes, bill elongation is related to a reduction of the braincase. The discriminant analysis shows that there are significant differences between penguins that feed near or far from the coast and between those that consume nectonic and planktonic prey, identifying Madrynornis as the only extinct form with a possibly planktonic diet. Additionally, it is clear that Paleogene penguins occupy a region of morphospace unexplored by most diving birds, with the western grebe being their closest modern analogue. This is consistent with the hypothesis that giant penguins hunted by harpooning and not by biting as living forms do, signaling a significant change in the habits of those birds leading to the emergence of their crown group.

Because the paleontologic concept of Coccolithophoridae species is restricted and far removed from the biologic concept, which itself is not yet satisfactorily established, calcareous nannofossil taxonomy remains in an unsatisfactory state. This situation is clearly reflected by various authors' widely different interpretations of the phylogenetic relationships among species in a given genus and among genera. Examples taken from the extant genus Helicosphaera suggest that because of parallel evolution, delineation of phylogenetic relationships among coccolith morphospecies using morphologic data alone are hazardous, as is delineation of phylogenetic relationships among closely related genera.

True muscular articulations, as opposed to ligamentary ones, are reported here for the first time in the biserial arms of advanced inadunate crinoids (Poteriocrinina). The topography of biserial articular surfaces indicates clearly derivation from a uniserial muscular articulation with two muscle scars, a transverse ridge, and other structures considered typical of this articular mode. Biserial muscular articulations extend from the arm base to within a few brachials of the arm tip, although the articulations are more pronounced and better developed proximally. The inadunate facets are compared with those of the biserial arms of camerates, which are shown to be non-muscular and probably were capable of only limited movement. The arm movements of inadunate biserial arms are interpreted to have been ones where alternating muscle bundles on either side of the arm induced twisting motions of the arms so that a planar filtration fan mode of feeding was possible, in contrast to the parabolic feeding fan or other modes of feeding that were probably performed by other Paleozoic crinoids.

Life span bias potentially alters species abundance in death assemblages through the overrepresentation of short-lived organisms compared with their long-lived counterparts. Although previous work found that life span bias did not contribute significantly to live–dead discordance in bivalve assemblages, life span bias better explained discordance in two groups: longer-lived bivalve species and species with known life spans. More studies using local, rather than global, species-wide life spans and mortality rates would help to determine the prevalence of life span bias, especially for long-lived species with known life spans. Here, we conducted a field study at two sites in North Carolina to assess potential life span bias between Mercenaria mercenaria and Chione elevata, two long-lived bivalve species that can be aged directly. We compared the ability of directly measured local life spans with that of regional and global life spans to predict live–dead discordance between these two species. The shorter-lived species (C. elevata) was overrepresented in the death assemblage compared with its live abundance, and local life span data largely predicted the amount of live–dead discordance; local life spans predicted 43% to 88% of discordance. Furthermore, the global maximum life span for M. mercenaria resulted in substantial overpredictions of discordance (1.4 to 1.6 times the observed live–dead discordance). The results of this study suggest that life span bias should be considered as a factor affecting proportional abundances of species in death assemblages and that using life span estimates appropriate to the study locality improves predictions of discordance based on life span compared with using global life span estimates.

Geographic range size and abundance are important determinants of extinction risk in fossil and extant taxa. However, the relationship between these variables and extinction risk has not been tested extensively during evolutionarily “quiescent” times of low extinction and speciation in the fossil record. Here we examine the influence of geographic range size and abundance on extinction risk during the late Paleozoic (Mississippian–Permian), a time of “sluggish” evolution when global rates of origination and extinction were roughly half those of other Paleozoic intervals. Analyses used spatiotemporal occurrences for 164 brachiopod species from the North American midcontinent. We found abundance to be a better predictor of extinction risk than measures of geographic range size. Moreover, species exhibited reductions in abundance before their extinction but did not display contractions in geographic range size. The weak relationship between geographic range size and extinction in this time and place may reflect the relative preponderance of larger-ranged taxa combined with the physiographic conditions of the region that allowed for easy habitat tracking that dampened both extinction and speciation. These conditions led to a prolonged period (19–25 Myr) during which standard macroevolutionary rules did not apply.

Evolutionary paleoecologists have proposed many explanations for Phanerozoic trends in ecospace utilization, including escalation, seafood through time, filling of an empty ecospace, and tiering, among others. These hypotheses can be generalized into four models of functional diversification within a life-habit ecospace framework (functional-trait space). The models also incorporate concepts in community assembly, functional diversity, evolutionary diversification, and morphological disparity. The redundancy model produces an ecospace composed of clusters of functionally similar taxa. The partitioning model produces an ecospace that is progressively subdivided by taxa along life-habit gradients. The expansion model produces an ecospace that becomes progressively enlarged by the accumulation of taxa with novel life habits. These models can be caused by a wide range of ecological and evolutionary processes, but they are all caused by particular “driven” mechanisms. A fourth, neutral model also exists, in which ecospace is filled at random by life habits: this model can serve as a passive null model. Each model produces distinct dynamics for functional diversity/disparity statistics when simulated by stochastic simulations of ecospace diversification. In this first of two companion articles, I summarize the theoretical bases of these models, describe their expected statistical dynamics, and discuss their relevance to important paleoecological trends and theories. Although most synoptic interpretations of Phanerozoic ecological history invoke one or more of the driven models, I argue that this conclusion is premature until tests are conducted that provide better statistical support for them over simpler passive models.

Pollen malformations have been proposed as a paleoenvironmental stress proxy. However, the frequency and variability of pollen malformations under near-optimal conditions and environmental stress, as well as their developmental origins, remain unclear. To bridge these gaps, we compared pollen malformation frequencies and assemblages of 14 extant conifer genera of Pinaceae and Podocarpaceae producing saccate (winged) grains grown under near-optimal conditions. These baseline pollen yields were compared with those produced by Pinus mugo ‘Columnaris’ cultured under an abiotic stress—three experimentally heightened ultraviolet-B radiation (UV-B) regimes proposed for the end-Permian crisis. We additionally reviewed previous cytological literature of abnormal microsporogenesis in conifers. Under near-optimal conditions, malformations comprise <3% of pollen yields in 12 out of 13 bisaccate genera and >10% of yields in the naturally trisaccate Dacrycarpus dacrydioides. We detected no phylogenetic pattern in malformation assemblages of the baseline comparisons. UV-B–irradiated P. mugo produced significantly higher malformation frequencies and different assemblage compositions when compared with baseline bisaccate lineages. We propose that pollen malformations originate during the meiotic and tetrad stages of microsporogenesis and present a framework for the ontogeny of different malformation types seen in the fossil record. Malformations comprising >3% of bisaccate pollen yields can be used as a paleoenvironmental stress proxy, but rare, naturally trisaccate lineages are not suitable for such assessments. Furthermore, heightened UV-B not only increases pollen malformation production, but also alters the types of abnormalities trees produce. Different environmental stresses may therefore leave behind distinct fingerprints in the fossil record.

Conodonts are among the first vertebrates to have evolved mineralized tooth-like structures. Among these, the so-called P1 elements are known to have been used to break down food and display a wide variety of morphologies. In particular, the repeated independent evolution of platform-like P1 elements have been suggested to correspond to similar functional constraints linked to diet. To test this hypothesis of convergence, we measured size (as element length) for various conodont taxa and used it as a proxy for trophic level. We then tested the correlation between size and platform presence/absence, both on raw data and in a phylogenetic context. Retaining or excluding the platform traits from the character matrix has limited impact on the resulting phylogeny. Contrary to platform presence/absence, size shows no phylogenetic signal. Using the raw data, size and platform presence appear positively correlated. That correlation, however, is no longer significant if one corrects for the phylogeny. We conclude that platform presence cannot be explained by an enlargement of the conodont element, be it via a trophic-level change or developmental constraints. This suggests that conodonts as a whole, and in particular platform-bearing conodonts, were an ecologically diverse group and that the various known platform types are likely to reflect different, rather than convergent, ecological niches.

Graphoglyptids are deep-marine trace fossils, often found preserved as casts in positive relief on the base of turbidites. Previous analyses of the behavioral evolution of graphoglyptids suggested they were slowly diversifying, becoming optimized, and getting smaller over time until the Late Cretaceous, when a sudden increase in diversification occurred. This current study quantifies the morphology of approximately 400 different graphoglyptid specimens, ranging in age from the Cambrian to the present, in order to evaluate the behavioral evolutionary interpretations made previously. Results from this study indicate that although some general evolutionary patterns can be discerned, they are not as straightforward as previously reported.

Different topological categories of trace fossils represent organisms’ responses to evolutionary pressures in unique ways. While burrow widths of meandering traces were becoming smaller over time, as predicted by previous workers, the burrow widths of the network traces were becoming smaller only until the Late Cretaceous, when they started to get larger again. The times of significant evolutionary changes in behavior were not consistent among various topological categories, with some morphological features being affected in the Late Cretaceous and others during the beginning of the Eocene. It is likely that the behavioral evolution of graphoglyptids was influenced by deep-marine global influences linked to climate change, glaciation, and deep-ocean warming. These influences affected each topological group uniquely, suggesting that different species or genera of trace makers were creating each of the topological categories. This is contrary to the hypothesis that all graphoglyptids were created by closely related species.

Studies of the internal anatomy of Mississippian camerate crinoids have revealed the presence and plan of groove and ridge networks here interpreted as evidence of former nervous systems in these animals. The inner thecal surfaces of hollow specimens and surfaces of internal chert molds possess radiating networks of grooves and ridges in both the dorsal cup and tegmen that resemble the plan of the aboral and hyponeural nervous systems, respectively, of modern crinoids. The aboral network of camerates radiates from the basal region of the dorsal cup at the point of stem attachment and provides one radially positioned nerve trunk per arm. In addition to the radial trunks, branches are present in each of the five interrays; the pattern in the CD (i.e., posterior) interray is different from the others. Two ring commissures interconnect the radial and interradial nerve trunks. The hyponeural nerve network in the tegmen originates from a ring commissure located near the upper part of the tegmen. From the ring commissure radiate radial and interradial nerve trunks that divide to produce two nerve trunks per arm as in modern crinoids. Raised ridges that define the hyponeural nerve network on the inner tegminal surface are separate from impressions representing the water vascular network.

By analogy to living crinoids, the aboral nerve center in camerates was located in the base of the dorsal cup. The radial portion of the aboral nervous system is judged to have functioned as the main motor network in camerates, innervating arm flexor muscles, pinnules, and arm epidermis, thus controlling the “display” of arms to form an effective filtration baffle. The interradial aboral nerves may have been sensory nerves which were part of an active balance system in these stalked echinoderms. The hyponeural system in camerates, as in living forms, probably acted as a sensory system by innervation of the lateral walls of the tube feet and arms. A third system, the ectoneural system, which lines the ciliated food grooves and gut of living crinoids has not been detected in fossil camerates; however, due to its functional significance, its presence in camerates was very probable.

The classical taxonomy of fossil invertebrates is based on subjective judgments of morphology, which can cause confusion, because there are no codified standards for the classification of genera. Here, we explore the validity of the genus taxonomy of 75 species and morphospecies of the Follicucullidae, a late Paleozoic family of radiolarians, using a new method, Hayashi's quantification theory II (HQT-II), a general multivariate statistical method for categorical datasets relevant to discriminant analysis. We identify a scheme of 10 genera rather than the currently accepted 3 genera (Follicucullus, Ishigaconus, and Parafollicucullus). As HQT-II cannot incorporate stratigraphic data, a phylogenetic tree of Follicucullidae was reconstructed for 38 species using maximum parsimony. Six lineages emerged, roughly in concordance with the results of HQT-II. Combined with parsimony ancestral state reconstruction, the ancestral group of this family is Haplodiacanthus. Five other groups were discriminated, the Parafollicucullus, Curvalbaillella, Pseudoalbaillella, Longtanella, and Follicucullus–Cariver lineages. The morphological evolution of these lineages comprises a minimum essential list of eight states of four traits. HQT-II is a novel discriminant analytical multivariate method that may be of value in other taxonomic problems of paleobiology.

Models presented here of shallow-marine siliciclastic deposition show that the widths of depth-defined regions differ markedly in response to sea-level change. These models add to recent studies that have emphasized the highly specific response of habitat area to sea-level change. Collectively, these studies indicate that a particular bathymetric zone on a particular margin may vary substantially in area during a sea-level change, while other such zones and margins may experience little or even opposite responses. In the models presented here, intermediate-depth and deep-water regions tend to show sinusoidal variations in width, with widening during relative falls in sea level and narrowing during relative rises. The shallow-water region displays markedly non-sinusoidal change and is consistently characterized by abrupt widening at the beginning of the highstand systems tract and an equally abrupt narrowing at the onset of sea-level fall at the beginning of the falling-stage systems tract. These onshore-offshore differences in how width and area change with sea level may explain why taxa in shallow-water settings tend to be more abundant, eurytopic, and widespread than those in deeper-water settings. Likewise, these models suggest that the evolution of novelty in nearshore habitats may be a response to wide variation in shallow-marine area during sea-level change.

The function of lunules in sand dollars is reviewed and it is argued that ambulacral lunules and the anal lunule evolved for quite different purposes. Whereas ambulacral lunules evolved to increase the perimeter of the test for food gathering, this was clearly not the original function of the anal lunule, although in some genera it has become secondarily adapted to this role. Many of the unique features of the anal lunule can be explained if it evolved as an outlet for ciliary feeding currents drawn centripetally into the mouth, without disrupting either oral or aboral currents. This allowed the entire margin of the test to be used for collecting the fine particles sieved through the aboral spine canopy. Anal lunules probably evolved only once, in the Miocene, and the Monophorasteridae and Mellitidae are probably sister groups.

The concept of punctuated equilibria was introduced by Eldredge and Gould (1972) as an interpretation of the sequential occurrence of species as actually observed in the fossil record. The pattern of sudden appearance of a new species followed by little or no morphological change during the remainder of the species' existence contrasts with phyletic gradualism, the pattern of slower, more evenly distributed change which was long considered to be the principal mode of species formation (Simpson 1944). The question of which is the dominant pattern of evolutionary change has continued as an actively debated theme in much of the paleontological literature of the past decade.

The Precambrian-Cambrian Boundary traditionally has been viewed as a fundamental discontinuity in the historical record of life. Almost from the birth of stratigraphic geology, it was recognized that the richly fossiliferous strata of Cambrian and younger periods were underlain by sedimentary rocks largely devoid of macroscopic fossils. Darwin (1872) was well aware of this dichotomy and of the “sudden manner in which several groups of species first appear” in the rock record. In the sixth edition of the Origin of Species (1872), he wrote, “The case [for this sudden appearance] at present must remain inexplicable … and may be truly urged as a valid argument against the views [on evolution] here entertained.” Careful biostratigraphic work by Walcott and others in the closing decades of the nineteenth century accentuated rather than dispelled the problem. Diverse Early Cambrian invertebrate assemblages were documented from North America and Scandinavia, but repeated searches for comparable fossils in Precambrian strata produced only a few, enigmatic remains (see review by Yochelson [1979]).

Individual egg size and clutch size of the largest of the dinosaurs (the sauropods) are both smaller than might be expected for such large oviparous organisms. We suggest that these effects can be understood in the light of likely incubation times of sauropod eggs. Using allometric relationships from extant birds and crocodilians, we estimate that time from laying to hatching was likely to have been 65–82 days. If total predation risk varies with length of incubation time, there may be egg sizes above which the advantages of larger initial hatchling size are outweighed by the increased risk of predation during the egg stage. Also, in seasonal environments there will often be a finite limit to the period over which environmental temperatures are high enough for egg development. Thus incubation time may have been an important constraint explaining the small individual size of sauropod eggs. We further suggest that for sauropods spatial dispersal of eggs in small clutches was an adaptive strategy to mitigate this high predation risk associated with long time of exposure in the egg stage. Such a dispersive strategy brings several benefits. Thus, incubation time may also be key to explaining the surprisingly small clutch sizes.

Associations of bathymetrically anomalous fossils, a phenomenon particularly common in shallow-water, marine, Neogene faunas of the northeastern Pacific, have yet to be explained adequately. No known physical transport processes can selectively move species upslope from deep water into diverse nearshore, shallow-water habitats. Previously proposed biological explanations are based on undocumented phenomena. We document bathymetric anomalies in Recent mollusc accumulations on Southeast Farallon Island, California, that are created by the activities of diving marine birds. Application of these observations to patterns in the Neogene fossil record is direct, involving the same genera and often the same species. We argue that the process has occurred since at least the Miocene when diving marine birds radiated rapidly, probably in response to trophic resources created by intensive upwelling (Lipps and Mitchell 1976) and that they could have transported specimens upslope in sufficient quantity to have contributed anomalous species to the Neogene fossil record. Specific examples from the literature are discussed.