摘要:

The morphology of the erythrosuchid ankle joint is reassessed. Two specimens, recently thought to have been incorrectly referred toErythrosuchus africanus, are shown without doubt to belong to this taxon. Furthermore, the morphology is essentially similar to that of other early archosaurs. The tarsus ofErythrosuchusis poorly ossified and consists of a calcaneum, astragalus, and two distal tarsals. The calcanea ofErythrosuchus, Vjushkovia triplicostata, andShansisuchus shansisuchusare all similar in being dorsoventrally compressed, possessing a lateral tuber, and lacking a perforating foramen. The astragalus ofV. triplicostatais currently unknown. The astragalus ofShansisuchusis apparently unique in form. The erythrosuchid pes is therefore more derived than has been recently proposed. The tarsal morphology of several other archosauromorph taxa is reviewed and many details are found to be at variance with the literature. The plesiomorphic condition for the Archosauromorpha consists of four distal tarsals and a proximal row of three elements; two of which articulate with the tibia. These proximal elements are interpreted as the astragalus, calcaneum, and a centrale, and the same pattern is retained in the earliest archosaurs. This reassessed tarsal morphology has implications for the homology of the centrale and reconstruction of early diapsid phylogeny.

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1996.tb00128.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

A multivariate morphometric study of the Greater white‐toothed shrew (C. russula) throughout its Palearctic range was carried out to search for patterns of geographic variation within the species boundary. Burnaby's and multiple group principal component analysis allowed the adjustment of raw data with respect to within‐sample allometric variation. Multivariate ‘size‐free‘results show a stepped cline with the phenotypical trait reduction and shape change from the eastern to the western Maghreb. Pleistocene fossil mandibles proved to have low phenetic distances with eastern populations (Tunisia, east Algeria) and it is argued that their character set is the primitive condition. The ancestral Mid‐Pleistocene shrews lived in a relatively more humid climate. Geo‐climatic changes in the north African range during the Quaternary provoked phenetic variation ofC. russulaand, it can be argued, evolution of the modern westernC.r. yebalensis.A historical process can thus be assumed as the main cause of this categorical variation, by segmentation of the species range due to geo‐climatic events. Morphometric discontinuity within theC. russulaMaghreb range is shown to be congruent with karyological and biochemical studies. Moroccan and Tunisian shrews differ, for example, in NFa chromosomes and electrophoretical traits. A stasipatric process should be invoked to explain categorical variation in the Maghreb range. Colonization and divergence of insular populations results in more or less differentiated geographic races. The populations of Ibiza and Pantelleria are close to the species threshold (Nei's D ≥ 0.1). The process of speciation undergone by the Greater white‐toothed shrew results in a complex pattern of geographic variation, including both allopatric and n

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1996.tb00129.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The maxilla II, normally present in crustaceans, is absent in most adult anomopods although it was found to occur in embryos of six species of this group. The appendage is reduced in representatives of families that lack it in the adult. The disappearance of the second maxilla is accomplished in a different way in the Chydoridae and Bosminidae as compared with the Daphniidae. A biramous structure of this appendage was observed in some stages of development in the largest species of Anomopoda. This feature of morphology is similar to the situation in other Branchiopoda.

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1996.tb00130.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Current phylogenics of mosasauroid reptiles are reviewed and a new phylogeny examining aigialosaur interrelationships presented. Patterns of mesopodial ossification and overall limb morphology are described for adult mosasauroids. Ossification sequences are mapped onto a phylogeny in order to assess the distribution of ontogenetic characters. Consistent and ordered distributions are found. Based on the phylogenetic distribution of ossification patterns, an overall mesopodial ossification sequence for mosasaurs is proposed. Carpal sequence: ulnare—distal carpal four (dc4)—intermedium—dc3—radiale or dc2—de1 or pisiform and dc5. Tarsal sequence: astragalus—distal tarsal four or calcaneum. Skeletal paedomorphosis is recognized as a dominant pattern in the evolution of mosasauroid limbs. Apomorphic characters of skeletal paedomorphosis, apparent in most taxa, reach extremes in tylosaurs. Arguments for the presence of a single proximal cartilage in the tarsus of mosasaurs are made. This cartilage is presumed to include ossification centres from which both the astragalus and calcaneum

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1996.tb00131.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Reproduction in the ctenostomate bryozoanAlcyonidium mytiliDalyell, 1848, was studied over 2 years, revealing confusion in the literature over the diagnostic characters of the species and incorrect assumptions about the mode of reproduction. The literature is briefly reviewed and an approximate type locality from the Firth of Forth, Scotland, is identified.Alcyonidium mytiliis comprehensively redescribed from material collected in the Firth of Forth and from 2 years' collections in the Daugleddau estuary, near Pembroke Dock, South Wales. Zooid and polypide dimensions and modal tentacle number (16) have been determined from large samples. Most importantlyA. mytilipossesses a conspicuous intertentacular organ when reproductive; is oviparous, with eggs discharged through the intertentacular organ developing into cyphonautes larvae; and has a prolonged winter reproductive period. The contrary indications in the literature are a consequence of confusion with a superficially similar but larviparous species.

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1996.tb00132.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY