Distribution Of Genus Research Articles

The distribution of Australian relict plants and its bearing on angiosperm evolution

The distribution of relict plants in the Australian flora shows a bimodal distribution of genera with relict vegetative characters and a unimodal distribution centred on N.E. Queensland for floral characters. Archaic features of the vegetative group link them with the Glossopteridae of Permian age. The geophysical history of the continent is reviewed and indicates only minor climatic changes since the Permian, which would permit the survival of primitive vegetative features. The bimodal distribution of this group is accounted for by the Cretaceous marine invasion of the continent and the unimodal distribution of the floral relicts by a preponderance of genera of Indo-Malaysian affinity, which could not have entered Australia until contact was made with New Guinea about 45 m. y. B.P. Two different cycles of evolutionary diversification are responsible for the two elements. Vegetative features of the Proteaceae relate to the Glossopteridae and are supported by Permian fossils scarcely distinguishable from modern leaves of Epacridaceae. If recent discoveries of Glossopteris fructifications are accepted as pro-angiosperms, it is shown that some anomalies in the vascular supply to the androecium in the Proteaceae can be accounted for.

The subfamily classification of the Micropezidae and the genera of Eurybatinae (Diptera: Schizophora)

ABSTRACTThe classification of the family Micropezidae is re‐examined and a key is given to the five subfamilies now recognised, of which Calycopteryginae is described as new and Eurybatinae is raised from tribal rank. Metopochetini is a new tribe of Eurybatinae. A key is given to the nine genera now included in the Eurybatinae, of which Papeza is described as new. P.szentivanyi is a new species from Papua. Notes on the taxonomy and distribution of genera are included. The position of Anaeropsis Bigot in the Micropezidae is confirmed. New synonymies are established as follows: Crepidochetus Enderlein (= Gongylocephala Czerny syn. n.); Metopochetus bivittatus (Macquart) (= Calobata tenuipes Walker syn. n.). New generic combinations are as follows: Metopochetus terminalis (Walker) and M.compressus (Walker) from Calobata; Crepidochetus nigrifemur (Czerny), C.pallidus (Steyskal), and Cater (Steyskal) from Gongylocephala; Crosa fragilis (Walker) from Micropeza; Crosa nigriventris (Enderlein) and C.uneifera (de Meijere) from Eurybata.

The geographical distribution of brachiopods in the British Middle Lias

Summary A study of the rhynchonelloid and terebratuloid faunas of the zone of Pleuroceras spinaturn in the Lower Jurassic of the British Isles has revealed a pronounced lateral variation in the distribution of genera and species. Four distinct faunal provinces are distinguished within the British area, and two of these are subdivided into two and three subprovinces respectively. The palaeo-ecological and palaeogeographical implications of the distribution are discussed. The Mendip, Moreton in Marsh and Market Weighton axes are shown to have acted as faunal barriers in spinatum Zone times. The ironstone facies of the Midlands provided a strongly selective environment. There are marked affinities between the brachiopod fauna of South-West England and that of Normandy, and also between those of Yorkshire and western Germany. The Hebridean region is believed to have been populated by migratory streams from both the above faunas, together with a third stream coming presumably from the north. A strong and ,effective faunal barrier existed along the line of the Pennines, possibly connecting with the Moreton in Marsh axis. Certain forms are thought to have been restricted to particular areas throughout considerable spans of Jurassic time.

Phylogeny in the Planorbidae.

Summary.The taxonomic characters in the Planorbidae, their theoretical background and the general basis of their application have been discussed. The various characters have been critically reviewed. In practice the male copulatory organ and the radula have proved to be the most important structures for phylogenetic studies in the family. The prostate comes next in importance. Occasionally the pallial ridges, the jaw, the general shape of the shell, the central nervous system and the lateral appendages are important as characters for comparative studies. More rarely still other features are useful.Representatives of almost all the planorbid genera have been examined morphologically and their phylogenetically important characters have been accounted for. The material examined includes the type species of twenty genera.On a comparative morphological basis the family Planorbidae has to be divided up into three subfamilies, the Plesiophysinae, the Bulininae and the Planorbinae. The Plesiophysinae are aberrant and well separated from the other subfamilies. The Bulininae are in the first place characterized by the presence of an ultra‐penis. The evolution of the ultra‐penis structure from the ordinary basommatophoran penis type is explained. Finally, the subfamily Planorbinae includes the greater majority of the planorbid genera.The genera of the subfamily Planorbinae are shown to form nine groups. For various reasons the following characters can be regarded as more or less primitive in Planorbinae: a spired, sinistral shell, a moderately concentrated central nervous system, long marginal teeth with both posterior and lateral cusps, the presence of pallial ridges, a terminal pore on the penis, the absence of a flagellum or other appendages on the copulatory organ and a simple prostate. Amerianna on the one hand and Physastra with Miratesta on the other seem to be most closely related to the primitive planorbine form though they do not have all the primitive features. The remaining groups can be arranged in two main branches characterized by two different types of marginal teeth in the radula. The branch characterized by short marginals includes the genera which can be grouped under the Planorbis tribe and the Segmentina tribe as well as the genus Acrorbis. The branch characterized by long marginals includes the genera which can be grouped under the Biomphalaria and the Helisoma tribes. The genera Camptoceras, Drepanotrema and Fossulorbis may perhaps also belong to this branch.In the Segmentina tribe and in the Helisoma tribe an accessory praeputial organ and an accessory duct between this organ and the upper end of the praeputial lumen or the penis sheath has evolved. These structures have almost certainly evolved independently in the two tribes. The probable origin of the structures has been reconstructed.The most likely relationships within the family Planorbidae are presented diagrammatically in the figs. 181, 200 and 209.The phylogenetically based classification present in this paper is critically compared with F. C. Baker's classification of the Planorbidae. Some remarks on the validity of various genera are also given.A synopsis of the broad distribution of the conventional planorbid genera is given in fig. 210. It shows a fairly good correlation between relationship and distribution of the genera.

On the Distribution of Genera and Species of Non–migratory Land–Birds in the Philippines.

On the Distribution of Genera and Species of Non–migratory Land–Birds in the Philippines.

The Distribution of Genera and Species of Non-Migratory Land Birds in the Philippines

The Distribution of Genera and Species of Non-Migratory Land Birds in the Philippines