bluuebunny/crossref_metadata_2025_split huggingface dataset:
Species in the fossil record: concepts, trends, and transitions
Authors: Gingerich Philip D. 
Published: July 2016

Morphological continuity in the fossil record is the principal evidence favoring evolution as a historical explanation for the diversity of life. Continuity is usually discussed on scales broader than the species level. Patterns of morphological variation characteristic of living species are useful in recognizing species on time planes in the fossil record, but the fossil record is rarely complete enough temporally or geographically to preserve more than a fraction of species living in a given interval. Transitions between known species are even rarer. Where transitions are preserved, new species appear to arise through anagenesis (transformation of an ancestral stock producing a modified descendant) and through cladogenesis (subdivision of an ancestral lineage where one or more descendants differ from the ancestral stock). Evolutionary species are often necessarily bounded arbitrarily in the dimension of time.Orthogenesis and punctuated equilibrium lie at opposite poles in a spectrum of speciation modes. Orthogenesis, highly constrained anagenesis, is probably rare. Cladogenesis appears to differ little from anagenesis once ancestral stocks are segregated. Limited evidence suggests that morphological differentiation during cladogenesis postdates genetic isolation. Hence punctuated equilibrium may be rare as well. Patterns of gradual change over time indicate that morphological evolution is reasonably viewed as continuous within and between species. Rates of evolution vary greatly (continuity does not require constancy). Rate distributions are truncated and biased by limits of stratigraphic completeness and time resolution: moderate to high rates of morphological evolution and species turnover are rarely recorded by fossils. Species durations are poorly characterized, but they appear to be so variable that there is no suggestion of periodicity. Species longevity is unpredictable. The episodic nature of faunal turnover suggests that extrinsic environmental factors rather than intrinsic homeostatic factors govern evolution at the species level.
The use of paleontology in systematics and biogeography, and a time control refinement for historical biogeography
Authors: Grande Lance 
Published: July 2016

Four main potential contributions of fossils to phylogenetic systematics and historical biogeography are (1) to provide additional taxa which (when sufficiently well preserved) can give new morphological and ontogenetic data in addition to those provided by Recent species; (2) to provide additional taxa which can increase the known biogeographic range of a taxon; (3) to help establish a minimum age for a taxon; and (4) to present fossil biotas that can be examined for biogeographic patterns not recognizable in younger (including the Recent) or older biotas.The first three points have been expressed or at least implied by other workers and are only briefly reviewed. The fourth point is proposed as a method of using fossil biotas to provide time controls to cladistic studies of historical biogeography. Previously, cladistic vicariance biogeographers have used fossilplusRecent biotas, or the Recent biota alone, for the geographic areas of study. Such investigations that lack any time control in the data base cannot effectively deal with areas that have complex histories as, for example, an earlier area of endemism in which area relationships are later complicated through the addition of exotic taxa by dispersal. By using time controls provided by fossil biotas, we may learn more about the relationships of areas with complex histories and may reveal biogeographical information that is sometimes unavailable through examination of the Recent biota.
Survivorship analysis of Cambrian and Ordovician trilobites
Authors: Foote Mike 
Published: July 2016

Cohort analysis is used to investigate survivorship of trilobites originating during the Cambrian and Ordovician. Using a time-homogeneous branching model, it is estimated that trilobite genera and species originating during the Ordovician survived three times longer than Cambrian genera and species. Monte Carlo simulation of survivorship is used to show that (1) Cambrian and Ordovician survivorship are significantly different, (2) Ordovician cohorts conform more closely to the time-homogeneous model than do Cambrian cohorts, and (3) deviations from temporal homogeneity are more often produced by extraordinary extinction than by unusually slow turnover.When Early Ordovician cohorts are decomposed into genera within families that originated in the Cambrian versus the Ordovician, no evidence that Cambrian and Ordovician survivorship differences are clade-specific can be found. Ordovician genera of Cambrian affinity and of Ordovician affinity become extinct at similar rates.Some of the ultimate causes of these differences in survivorship include (1) taxonomic inconsistency, (2) greater environmental stability in the Ordovician, and (3) more highly structured ecosystems in the Ordovician that may have led to the weeding out of extinction-prone taxa.
The decline and extinction of Plesiadapiformes (Mammalia: ?Primates) in North America: displacement or replacement?
Authors: Maas Mary C. , Krause David W. , Strait Suzanne G. 
Published: July 2016

Plesiadapiforms were among the most diverse and abundant of North American mammalian groups during the Paleocene epoch. Their decline and extinction has been attributed to a variety of causes, including competitive exclusion by rodents and/or by primates of modern aspect (euprimates), and the effects of late Paleocene–early Eocene climatic warming. However, analyses of generic and species richness and relative abundance patterns indicate that the decline of plesiadapiforms was more complex than usually supposed. The two major superfamilies, Plesiadapoidea and Microsyopoidea, exhibited very different patterns of decline. Microsyopoids and paromomyid plesiadapoids do not exhibit a pronounced decline in taxonomic richness and relative abundance during the Early Tertiary. Non-paromomyid plesiadapoids do decline markedly, but, when their taxonomic richness and relative abundance patterns are compared with those of potentially competing taxa (rodents and euprimates) only non-paromomyid plesiadapoids and rodents show the inverse relationship consistent with taxonomic displacement. Euprimates appear in North America after non-paromomyid plesiadapoids were virtually extinct. Analyses of body size, diet, diel activity patterns, and locomotion support the hypothesis that rodents and non-paromomyid plesiadapoids may have competed for the same resources; their paleobiogeographic histories also are consistent with the competition argument.Currently available paleoclimatological data for the Early Tertiary largely pertain to global temperature trends and are not detailed enough to demonstrate unequivocally whether the decline of non-paromomyid plesiadapoids coincided with climatic change. A more complete record of paleoclimatic indicators, especially from the Western Interior of North America, is needed to test the climate hypothesis adequately. The several independent lines of evidence considered here and elsewhere in reference to other mammalian taxa strongly support the hypothesis that competition with rodents was an important factor in a major restructuring of Early Tertiary mammalian communities in North America.
Crises in the Devonian history of the rugose corals
Authors: Oliver William A. , Pedder A. E. H. 
Published: July 2016

Detailed analysis of the stratigraphic ranges of Devonian rugose coral genera within the Old World and Eastern Americas Realms gives new information on faunal extinctions and other bioevents in both realms. Various origination and extinction metrics are calculated from tabulations of occurrences in each stage. The most significant faunal changes were near or at the ends of the Lochkovian and Frasnian stages. The former marks the gradual transition from dominance by Silurian families and genera to the characteristic Devonian coral assemblages; the latter marks the virtual extinction of the Devonian families and genera. Other coral events are related to the two major changes.The data provide new bases for comparing the histories of the two realms. Most of the events are recorded in both, giving support to previous suggestions that the causes were worldwide. The coral record shows an increase (probably episodic) in environmental deterioration persisting through the Middle Devonian and culminating in extinction at the end of the Frasnian. Eustatic sea level fluctuations may have caused the precursor events and a bolide impact may have caused the end-Frasnian extinction.
Effects of the Mesozoic Marine Revolution on the taxonomic, morphologic, and biogeographic evolution of a group: aporrhaid gastropods during the Mesozoic
Authors: Roy Kaustuv 
Published: July 2016

The mid-Mesozoic time was characterized by massive reorganization of the ecological structure of benthic marine communities. Although the general pattern of this “Mesozoic Marine Revolution” has been extensively documented, little is known about how it affected the taxonomic and morphologic diversities of individual lineages of organisms. Here I document group-level dynamics of the Mesozoic change using the fossil record of aporrhaid gastropods, a diverse and widespread family during that time. Using data gathered through field and museum work and extensive literature search, I compare and contrast patterns of taxonomic and morphologic change during the Jurassic and Cretaceous within a geographic framework. I also examine how the changes were manifested at different ecological and geographic scales.The Mesozoic history of the Aporrhaidae includes two major radiations separated by a period of overall stability. While both radiations increased the taxonomic diversity of the family, they had very different morphologic consequences, resulting in a striking discordance between morphologic and taxonomic diversity patterns. The initial radiation during Bajocian-Bathonian times established two large morphologic groups within the aporrhaids based mainly on differences in the shape of the apertural margin. The second, post-Albian, radiation saw higher origination rates and increased taxonomic and morphologic diversity among genera having simpler apertural margins, while genera with elaborate multidigitate apertures declined in taxonomic diversity but not in morphologic diversity. During post-Albian times the group with simpler apertural margins also tended to be more widespread compared to the group with multidigitate apertures. Comparison of regional and global taxonomic diversities reveals a discordance between regional and global taxonomic patterns: while diversities within certain geographic areas increased in concert with the global radiation, those for other areas decreased substantially, resulting in a remarkably constant average taxonomic diversity within geographic areas.
Stable isotopic signals and photosymbiosis in Late Paleocene planktic foraminifera
Authors: D'Hondt Steven , Zachos James C. , Schultz Gretchen 
Published: July 2016

Late Paleocene planktic foraminifera exhibit strong positive correlations between carbon isotopic values and test mass, but negative correlations between oxygen isotopic values and test mass. Based on analogy with modern taxa, these trends are probably ecotypic and may or may not apply to an ontogenetic series. AmongAcarininaandMorozovellaspecies, the magnitude and direction of these trends resemble those of modern planktic foraminifera with dinoflagellate photosymbionts. This is consistent with current models of photosymbiosis and calcification in planktic foraminifera and suggests thatAcarininaandMorozovellarelied heavily on photosymbionts for nutrition.AcarininaandMorozovellaspecies resemble modern, strongly photosymbiotic taxa in their association with low and mid latitude nearsurface water masses. However, their test morphologies differ greatly from those of extant taxa that bear obligate photosymbionts. Earliest Paleocene taxa that exhibit a similar paleohabitat association and similar size-related isotopic trends are characterized by still different test morphologies. These comparisons suggest that (1) throughout geologic time, strong reliance on photosymbiont activity has been closely linked to habitat, but not to test morphology; (2) photosymbiosis has been a common and convergently evolved strategy of planktic foraminifera over geologic time, and (3) modern relationships between planktic foraminiferal test morphology and photosymbiont dependence are largely an artifact of geologically recent phylogenetic relationships and shared ecologic strategies.Intersite comparison suggests that the stable isotopic signals of narrowly constrained size fractions of a late PaleoceneAcarininaorMorozovellaspecies can be used to reconstruct the magnitude and direction of relative variation in equilibrium stable isotopic values throughout its geographic and temporal range. This is supported by analogy with extant photosymbiotic taxa. However, since photosynthetic depletion of12C leaves13C-enriched HCO3-for calcification, the carbon isotopic values ofAcarininaandMorozovellatests may have been consistently greater than paleoseawater values. Failure to account for this effect could lead to overestimation of late Paleocene marine productivity.
Phylogeny reconstruction and the tempo of speciation in cheilostome Bryozoa
Authors: Jackson Jeremy B. C. , Cheetham Alan H. 
Published: July 2016

We compared phylogenies derived from morphological data for two cheilostome bryozoan genera,StylopomaandMetrarabdotos,with genetic differences between species (Stylopoma) and the stratigraphic occurrence of fossils (both genera). Correspondence between species ofStylopomadefined by protein electrophoresis and on preservable skeletal morphology is excellent, despite great morphological variability within colonies and the predominance of quantitative over discrete characters. Moreover, agreement between genetic and morphological classifications increased greatly when morphological discrimination was pushed to the limit, despite inability to consistently assign all specimens to species with high confidence. This “splitting” strategy also maximized the correlation between genetic distances and the distances between species in cladistically derived phylogenies.Fossil and living species of both genera are sufficiently abundant and widespread to provide credible limits for inferred ancestral relationships. Inclusion of fossils in cladistic analyses ofStylopomaincreased the consistency of cladistic hypotheses by up to 30% and provided a more effective means of rooting trees than comparison with living species of the most closely related genus (“outgroup”). Moreover, in the case ofMetrarabdotos,failure to incorporate stratigraphic information turned the cladogram virtually upside down, so that postulated ancestors first appear in the fossil record 6–16 m.y. after their putative descendants became extinct.Stratigraphically rooted trees suggest that most well-sampledMetrarabdotosandStylopomaspecies originated fully differentiated morphologically and persisted unchanged for > 1 to > 16 m.y., typically alongside their putative ancestors. Moreover, the tight correlation between phenetic, cladistic, and genetic distances among livingStylopomaspecies suggests that changes in all three variables occurred together during speciation. All of these observations support the punctuated equilibrium model of speciation.
Were the Ediacaran fossils lichens?
Authors: Retallack Gregory J. 
Published: July 2016

Ediacaran fossils are taphonomically similar to impressions of fossil plants common in quartz sandstones, and the relief of the fossils suggests that they were as resistant to compaction during burial as some kinds of Pennsylvanian tree trunks. Fossils of jellyfish are known from siderite nodules and fine-grained limestone, and even in these compaction-resistant media were more compressed during burial than were the Vendobionta. Vendobionta were constructed of materials that responded to burial compaction in a way intermediate between conifer and lycopsid logs. This comparative taphonomic study thus falsifies the concept of Vendobionta as thin soft-bodied creatures such as worms and jellyfish.Lichens, with their structural chitin, present a viable model for the observed preservational style of Vendobionta, as well as for a variety of other features that now can be reassessed from this new perspective. The diversity of Ediacaran body plans can be compared with the variety of form in fungi, algae, and lichens. The large size (ca. 1 m) of some Ediacaran fossils is reasonable for sessile photosynthetic symbioses, and much bigger than associated burrows of metazoans not preserved. Microscopic tubular structures and darkly pigmented cells in permineralized late Precambrian fossils from Namibia and China are also compatible with interpretation as lichens. The presumed marine habitat of Ediacaran fossils is not crucial to interpretation as lichens, because fungi and lichens live in the sea as well as on land.
Preferential survivorship of brooding corals in a regional extinction
Authors: Edinger Evan N. , Risk Michael J. 
Published: July 2016

Approximately half of the Caribbean Oligocene reef coral fauna became locally extinct during the Early Miocene; roughly two thirds of the genera driven to local extinction still survive in the Indo-Pacific. Coral genera with lecithotrophic larvae (brooders) preferentially survived, over those with planktotrophic larvae (broadcasters). Among 37 genera for which we inferred reproductive mode, 73% of brooding genera survived the Oligocene/Miocene extinction events, while only 29% of the broadcasting genera survived. The proportion of brooders to broadcasters also increased markedly. During the late Oligocene, 47% of Caribbean reef coral genera were broadcasters, but in the middle Miocene, only 32% of the genera were broadcasters.Survivorship in Puerto Rican reefs was correlated with tolerance of cold and turbid conditions. Genera tolerant of both cold water and turbidity had much higher survival rates than those tolerant of turbidity alone. Only 25% of the genera that could tolerate neither cold water nor turbidity survived. Most of the eurytopic genera were brooders, while most of the stenotypic genera were broadcasters.We present two hypotheses that may account for the preferential survivorship of brooders: the recruitment hypothesis, and the dispersal hypothesis. The recruitment hypothesis holds that brooders survive preferentially because lecithotrophic larvae have higher recruitment success than do planktotrophic larvae in marginal habitats, such as upwelling zones. This is supported by the correlation of brooding and eurytopy. The dispersal hypothesis suggests that brooders survive preferentially because lecithotrophic larvae, which typically inherit zooxanthellae from the egg, have a longer larval lifespan and, hence, a wider potential dispersal range, than planktotrophic larvae, which typically capture zooxanthellae from the water column. Biogeographic range data, however, do not support this second hypothesis: modern Indo-Pacific brooding and broadcasting genera have nearly identical ranges, and many brooding species have narrower longitudinal ranges than do broadcasting species. Preferential survivorship of brooding corals contrasts sharply with survivorship patterns among molluscs during extinction events; among molluscs, broadcasters are favored over brooders.A major increase in upwelling at the Oligocene/Miocene boundary was probably responsible for this extinction/geographic restriction event. Preferential survival of brooding and mixed mode coral genera appears to be a product of their being better able to recruit and survive in marginal conditions such as upwelling zones.
A biomechanical model for the morphogenesis of regular echinoid tests
Authors: Dafni Jacob 
Published: July 2016

Experiments were conducted to test the hypothesis that biomechanical constraints determine the morphology of regular echinoids. Hard-bottom-dwellingTripneustes gratilla elatensiswere transferred to an artifical sandy habitat to evaluate whether the change in substrate affects their height to diameter ratio (H/D). Within 1–2 months their H/D ratio increased significantly. This change was shown to be reversible to some extent. Surgical damage to the ambulacral system of one ray caused inactivation of tubefeet and atrophy of injured ambulacra. Test shape was also affected: the damaged ray was lower, and the nondamaged ambulacra deflected toward the treated one, producing bilateral symmetry as in recorded cases of teratology. Study ofT. g. elatensistetramers showed that while “perfect” tetramery was apparently associated with genetic aberration, “imperfect” tetramery results from mechanical injury at an early ontogenetic stage. Micromorphological study shows that in the longitudinal sutures, normally under tension, long and slender trabeculae develop, associated with long and well-aligned collagenous sutural fibers, while the latitudinal trabeculae and fibers are short and less organized. A mechanical effect is suggested by the oval cross-section of the fiber-anchoring trabeculae. Further, echinoid plates interact like soap bubbles, whereas the entire test behaves like a balloon, fastened to the substrate by the ambulacral tubefeet. All these observations support earlier hypotheses on the biomechanical control of echinoid test growth. A model is proposed in which the expansion of the inner mass, counteracted by the mechanical activity of the ambulacral tubefeet, mesenterial threads, and lantern muscles, affects sutural growth, thus controlling echinoid morphogenesis.A morphometric survey among regular echinoids reveals an inverse relationship between ambulacral width and relative ambital height. Although both increase of ambulacral width and lowering of ambitus-line are evolutionary trends, it is suggested that they are a response to a mechanical effect. H/D ratio was not related to ambulacral width on the phylogenetic level. It is therefore suggested that the latter correlation is ontogenetically controlled. Aspects of irregular echonoid evolution, such as bilateral symmetry, flattening, and formation of the ambulacral petaloid, also are explained by this model.
Are brachiopods better than bivalves? Mechanisms of turbidity tolerance and their interaction with feeding in articulates
Authors: Thayer Charles W. 
Published: July 2016

The dominance of Paleozoic articulate brachiopods in once-muddy environments may be explained by an array of mechanisms and structures that reject nonfood particles, in some cases without interruption of feeding: (1) behavioral flexibility of the lophophore and its individual filaments; (2) persistent, variable-speed rejection currents on the mantle, which sometimes concentrate pseudofeces in topographically controlled vortices; (3) costae and alae (which have many other probable functions); (4) inhalant currents elevated above substrate; (5) marginal setae.Some mantle currents parallel (and presumably augment) lophophore feeding currents; others diverge up to 90° to provide rejection while feeding continues. Contrary to previous reports, the lateral cilia seem to be involved in rejection and may reverse.Repeated claims for the superiority of the gill of suspension-feeding bivalves over the “weak” individual filaments of the lophophore are probably false. In suspension-feeding bivalves, simultaneous feeding and rejection are likely to be hindered by fused gill elements and mucus-trapping of food. The energetically efficient articulates are predicted to have a competitive advantage over suspension-feeding bivalves when oxygen or food is limiting, as, for example, after a bolide impact.