Plesiomorphic Character States Research Articles

A phylogenetic analysis of the Tubificinae (Oligochaeta, Tubificidae)

The Tubificinae is a monophyletic taxon in relation to the outgroup Rhyacodrilus. A hypothetical ancestor with almost completely plesiomorphic character states was included in the analyses. It appears at the base of the taxon as expected when the outgroup is used for rooting, but is unresolved in relation to the genera Lymphachaeta and Peipsidrilus. The genera with elongate atria form a monophyletic group, as do all the papillate taxa with the exception of Tubificoides. The generic and subgeneric rankings of the papillate taxa that constituted the bulk of the former genus Peloscolex require cladistic evaluation. The separation of Ilyodrilus, Teneridrilus, and perhaps even Tubificoides also needs to be investigated. Clitelloides and Lycodrilides are potential synonyms of Clitellio and Lycodrilus, respectively.

The rediscovery ofcyclopicina longifurcata(scott) (copepoda: cyclopinidae) in deep water in the north atlantic, with a key to genera of the subfamily cyclopininae

Abstract The marine cyclopoid, Cyclopicina longifurcata (Scorr) is redescribed on the basis of the holotype and a second female, recently collected in deep water in the North Atlantic off the Azores. Cyclopicina is one of the most primitive cycJopoids known, displaying many of the extreme plesiomorphic character states in the family Cyclopinidae. A key to genera of the subfamily Cyclopininae is presented and three new genera, Herbstina, Erythropolites, and Glareolina, are established.

The pollen morphology ofOdontites (Scrophulariaceae) and its taxonomic significance

The pollen morphology of 29 species ofOdontites and related genera was examined by light and scanning electron microscopy. Three major pollen types differing fundamentally in exine sculpturing were found. In the parasitic tribePedicularieae retipilate sculpturing is the most widespread type representing a plesiomorphic character state from which the two other types are derived. Of these, reticulate sculpturing is confined toOdontites, whereas a complex retirugulate pattern was found only in the monotypic Near East genusBornmuellerantha. Within the retipilate and the reticulate major types eight minor types were distinguished based on the differential correlation of exine surface morphology, size, shape and amb form. The pollen data are generally well correlated with macromorphological features and furnish important taxonomic characters at the genus—as well as at the specieslevel.

Allozyme genetic distances and evolutionary relationships in species of akodontine rodents (Cricetidae: Sigmodontinae)

Allozyme genetic distances were estimated for ten species of akodontine rodents, as compared with the Oryzomyini Oligoryzomys longicaudatus, which was used as an outgroup to assess plesiomorphic character-states. Twenty-six loci were analysed. Distribution patterns of allele frequencies were determined by both phenetic (UPGMA) and cladistic (PAUP') techniques. Allozyme analysis confirmed monophyly for the Akodontini, and among them, the distinctiveness of the genus Oxymycterus. Genetic divergence among the eight species of Akodon was small compared to most known species of rodents. Phenrtic and phylogenetic analysis between Bolonys obscurus and species of Akodon was m agreement with previous chromosomal work but in disagreement with the indications of morphology. The general lack of allozymic differentiation among members of the Akodontini suggests that in this group molecular divergence is unrelated to speciation. Molecular clock estimation calibrated by fossils showed that generic divergence within Akodontini started at least in the late Miocene and that divergence of Akodintini from Orizomyini occurred within the Miocene.

Evolutionary and morphological significance of the deflecting wrinkle in the lower molars of the Hominoidea.

The deflecting wrinkle is a well-known character state of the lower m2 and M1 of the human dentition, but there is little information regarding its presence in great apes. The deflecting wrinkle is more frequent on M2-3 in all extant pongid genera studied in this paper except Pan paniscus, in which M1 has the highest frequency (16.0%) and in which this wrinkle is absent on M3. In Gorilla, it is absent on M1, with only a low incidence on M2-3. Its greatest frequency in Pongo is always on M2 (20.2%), which is the greatest expression of the trait in the great apes. We interpret the presence of the deflecting wrinkle as an incidental effect and suggest that it represents a plesiomorphic character state in the Hominoidea.

Ephemeroid wing venation based upon new gigantic Carboniferous mayflies and basic morphology, phylogeny, and metamorphosis of pterygote insects (Insecta, Ephemerida)

Gigantic as well as very large mayflies from the middle Upper Carboniferous (Westphalian) strata of Europe and North America are described: the adult and nymph of Bojophlebia prokopi n. gen., n. sp. (Bojophlebiidae n. fam.) and the nymphs of Lithoneura piecko n. sp. and Lithoneura clayesi n. sp. (Syntonopteridae). Evolution of ephemerid wing venation during 300 million years is summarized. Autapomorphic, apomorphic, and plesiomorphic character states of venation are categorized. Venational nomenclature of Recent Ephemerida is emended based on its evolutionary changes. Evidence that wing veins occurred primitively as a pair of fluted sectors is documented in Carboniferous mayflies in the costa, subcosta, radius, anal, and jugal. Ephemeroids and odonatoids are sister groups that share the veinal anal brace AA fused with CuP at an area important for flight. Ancestral Odonatoephemerida are the sister group of the extinct haustellate Paleoptera. The Carboniferous nymphs bear three pairs of almost homonomous thoracic wings and, on the abdomen, nine pairs of legs and nine pairs of tracheal gills (wing homologues). This proves that abdominal legs have been totally reduced in Recent Ephemerida except for the claspers (gonopods) and that tracheal gills are not flattened legs. The metamorphic instar probably originated in relatively young instars. Insectan cerci developed from segmented, arched, functional legs of abdominal segment 11, which were still present in this primitive condition in Carboniferous Monura.

Revision of the genus Stigmatonotum Lindberg (Hemiptera Lygaeidae)

AbstractThe genus Stigmatonotum is redescribed, an analysis of important taxonomic and phylogenetic characters given and a key to species included. All species are diagnosed or described. Two new species are described, S. elongatum (Tanzania, Natal) and S. attenuatum (Ghana). S. carinatum Linnavuori is synonymized with S. afra StÅl. Plociomera japonica Distant and S. minutum Malipatil are synonymized with S. geniculatum (Motschulsky). Linnavuori's record of S. capucinum and Hsiao et al.'s of S. rufipes are referred to S. geniculatum. Lectotypes are selected for S. rufipes and S. geniculatum. Humilocoris Harrington is noted as having an erroneous type species. The status of the genus relative to Stigmatonotum is discussed. The third, fourth, and fifth instars of S. capucinum are described. Habitat notes are included for several species and general distributional data given for all species. There is a discussion of plesiomorphic and apomorphic character states. A cladogram is provided.

Origins and relationships of primitive members of the Opisthobranchia (Mollusca: Gastropoda)

An examination of possible prosobranch precursors of opisthobranchs and pulmonates suggests that archaeogastropods are poor candidates, as they lack the complex female glands which characterize all higher gastropods. Similarities between members of the Rissoacea and Cerithiacea with the Opisthobranchia and Pulmonata are here considered to be a result of parallel evolution. Much of the basis for suggesting phylogenetic aRinities between members of these taxa hinges on the supposition that pyramidellids are opisthobranchs. This contention is questioned, as the euthyneurous nervous system and hermaphroditic reproductive system share weak structural and positional homologies with opisthobranchs. The range of morphological variation within the Pyramidellidae should be more thoroughly investigated, as this taxon is poorly known. The reproductive system of members of the Littorinacea is largely homologous with that found in the least derived opisthobranchs and pulmonates. This, when considered in conjunction with other morphological and palaeontological evidence, suggests that the least derived mesogastropods, the Littorinacea, provide a more precise model of the opisthobranch-pulmonate ancestor among living prosobranchs. The specialization of the digestive system in littorinaceans suggests that morphological divergence has taken place following the cladogenesis of these taxa, and that a direct ancestor/descendent relationship cannot be implied from extant littorinaceans. The status of Acteon and other acteonids as archetypal opisthobranchs is questioned. Moditication 01 all morphological systems, with the exception of the shell and mantle complex, diminish the position of the Acteonidae as ancestral opisthobranchs. Members of the Ringiculidae more closely approach the ancestral form, but have undergone modification, as well. No extant opisthobranch retains all plesiomorphic character states. For this reason, in addition to the fact that contusion exists as to the plesiomorphic conditions of some characters within the Opisthobranchia, a hypothetical ancestral opisthobranch is characterized. It appears that parallel evolution, which confounds the relationships of certain prosobranchs and opisthobranchs, is also evident within the Opisthobranchia. Much of the confusion that has surrounded the determination of phylogenetic relationships within the Opisthobranchia relates directly to the high incidence of parallelism throughout the subclass.