Inclusion Of Fossils Research Articles

Frontiers to science: free trade and museum ethics

There is nothing inherently wrong about museums purchasing specimens from commercial dealers who act honestly and in good faith. Indeed, a significant amount of the taxonomically important material in the UK's great public collections has been acquired in this way. Doing business with the trade does, however, carry risks, and there are many ways in which the unwary curator can be ripped off by an unscrupulous dealer. Apart from fakes and forgeries, the most pernicious and damaging aspect of the trade is in illicit material. Museums should respect the laws of countries which seek to protect fossils as part of their cultural patrimony. This ethic is enshrined in international convention and in the ethical codes that apply to UK museums both at an individual and institutional level, through the UK's Registration scheme. The UK is about to become signatory to the 1970 UNESCO Convention, which outlaws the international illicit trade in cultural property, and will create a new law to criminalise such activity. This paper argues the case for accepting UNESCO's inclusion of fossils in the definition of cultural property. The more relaxed ethic of some academic palaeontologists compared with the ethical standards of mainstream geological curators in the UK should be addressed by drafting a protocol, whose standards should be developed in consultation between curators, academics, and reputable representatives of the trade and third world countries from which most illicitly traded fossils originate.

Phylogeny reconstruction and the tempo of speciation in cheilostome Bryozoa

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.

The fossil record and estimating divergence times between lineages: Maximum divergene times and the importance of reliable phylogenies

Bounded estimates on divergence times between lineages are crucial to the calculation of absolute rates of molecular evolution. Upper (minimum) bounds on divergence times are easily estimated based on earliest fossil finds. Lower (maximum) bounds are more difficult to estimate; the age of putative ancestors may be used, though in practice it is virtually impossible to distinguish ancestors from primitive sister groups, which do not, of logical necessity, constitute lower bounds on divergence times. Two relatively new approaches to estimating lower bounds directly assess the incompleteness of the fossil record. The first uses taphonomic control groups to distinguish real absences from nonpreservation, while the second, and probably more powerful, uses the quality of the fossil record to estimate confidence intervals on the bases of stratigraphic ranges. For some groups, especially vertebrates, the inclusion or exclusion of problematic fossils can dramatically affect estimated lower bounds on divergence times, often swamping the uncertainties due to the incompleteness of the fossil record and/or correlation and dating errors. When datable paleogeographic events reflect ancient divisions of faunas, a lower bound on the divergence time of species within a fauna can be established based on the geologic, rather than fossil, record. The fossil records of hominids, eutherian mammals, echinoids, and geese are used as examples.

A Phylogenetic Analysis of the Caminalcules. III. Fossils and Classification

-The consequences of introducing fossil species into a numerical taxonomic data, set are examined, using the Caminalcules as an example. This group of organisms was generated artificially according to principles believed to resemble those operating in real organisms. Inclusion of fossils into the phenetic classification introduces some nonconvex taxa at higher phenetic levels, but unites phenetically homogeneous groups of mixed Recent and fossil composition. There is good correspondence of phenetics with phylogenetic sequences. The taxonomic relationships of the phenetic classification of Recent plus fossil forms can be explained by the amount of evolutionary change known to have occurred in given internodes. All but one of the mutually closest pairs in the phenogram are ancestor-descendant pairs. Gingerich's stratophenetic method yields a reasonably good estimated cladogram, but is misled by the occurrence of homoplasy in portions of the tree. Adding fossils improves estimates of the true cladogram based on the distance Wagner method but not estimates based on the Wagner parsimony algorithm. Estimated cladograms approach the true cladogram more closely than phenograms do, yet even the best estimate including the fossils has a strict consensus index no higher than 0.667. There are 10 characters that define genera. Their removal from the data base affects phenetic classifications slightly, cladistic classifications somewhat more. A cladistic classification of the Recent Caminalcules unnecessarily raises the ranks of some taxa. The less speciose and more symmetrical taxa emerge at lower taxonomic ranks than more speciose and asymmetrical taxa. Adding fossils to the Caminalcules requires a greater number of ranks for a cladistic than for a phenetic classification. [Phenetic classifications; cladistic classifications; classification of fossils; stratophenetics; Caminalcules; numerical taxonomy.] The availability of the true cladogeny of the Caminalcules, a group of artificially created organisms, has presented an opportunity for examining various principles and practices of current interest to systematists. In an earlier paper (Sokal, 1983a), I presented the images of all 77 Recent and fossil Caminalcules, definitions of their characters and the data matrix employed in this study, as well as a cladogram of their true phylogeny. A new standard phenogram was also featured. In a second paper (Sokal, 1983b), I examined the efficacy of numerical cladistic methods for finding the true cladogram from an assemblage of Recent species and examined the reasons for the departure of numerical phenetic and cladistic dendrograms from the correct genealogy. The current study deals with the consequences of introducing fossil species into a taxonomic data set, using the Caminalcules as a test case. It is of interest to compare the classifications obtained by numerical phenetic and numerical cladistic techniques in such a data set. Does introduction of fossil species simplify or complicate phenetic classifications, will it improve or worsen estimated cladograms, and does it widen or narrow the discrepancy between the two kinds of dendrograms? Knowing the true cladogram, including all fossils and the evolution of characters upon it, permits investigations of some additional taxonomic and evolutionary questions. I have already reported on various types of tree statistics and evolutionary rates (Sokal, 1983a). Here I examine whether a hierarchy of taxonomic characters can be said to exist. Furthermore, I look into the classifications that result when the Caminalcules are classified on the basis of phenograms or of cladograms, with or without the fossils. The Caminalcules are unusual as taxonomic objects in that they include all fossil members of the taxon up to and including their most recent common ancestor. The presence of fossils among the OTUs of a data set create prob-

Dystonic Reaction to Trifluoperazine

<h3>Abstract</h3> Biodiversity currently peaks at the equator, decreasing toward the poles. Growing fossil evidence suggest that this hump-shaped latitudinal diversity gradient (LDG) has not been persistent through time, with similar species diversity across latitudes flattening out the LDG during past greenhouse periods. This provides a new starting point for LDG research. Most studies assume the processes shaping the LDG have acted constantly through time and seek to understand why diversity accumulated in the Holarctic at lower levels than at the equator, <i>e.g.</i> as the result of limited dispersal, or higher turnover in Holarctic regions. However, fossil investigations suggest that we need to explain when and why diversity was lost at high latitudes to generate the LDG. Unfortunately, diversity lost scenarios in the Holarctic have been repeatedly proposed but not yet clearly demonstrated. Here, we use diversification approaches for both phylogenies and fossils to study the LDG of Testudines, Crocodilia and Lepidosauria. We show the LDG of these groups has varied over time, with high latitudes serving as a source of tropical diversity but suffering disproportionate extinction during transitional periods to cold climate. We outline the ‘asymmetric gradient of extinction and dispersal’ (AGED) framework, which contextualizes previous ideas behind the LDG under a time-variable scenario. We suggest the current steep LDG may be explained by the extinction of clades adapted to warmer conditions from the new temperate regions formed in the Neogene, together with the equator-ward dispersal of organisms tracking their own climatic preferences, when tropical biomes became restricted to the equator. Conversely, high rates of speciation and pole-ward dispersals can account for the formation of an ancient flat LDG during the Cretaceous–Paleogene greenhouse period. Our results demonstrate that the inclusion of fossils in macroevolutionary studies allows detecting extinction events less detectable in analyses restricted to present-day data only.