摘要:

Three new genera of pteraspidids from Arctic Canada improve the known distribution of the family beyond Europe, Spitsbergen and eastern Canada where they have biostratigraphic value.

ISSN:0272-4634    

DOI:10.1080/02724634.1983.10011942

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Hardistiella montanensisn. gen. et sp. from the Lower Carboniferous (Namurian) Bear Gulch Limestone Member of the Heath Formation, Montana, is the only lamprey known to retain a clearly hypocercal tail and an anal fin provided with rays. These two characters are plesiomorphous and are also met with in “anaspids” and “thelodonts.” An analysis of the relationships of the petromyzontids indicates that they are the sister group of some of the “anaspids.”

ISSN:0272-4634    

DOI:10.1080/02724634.1983.10011943

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

The use of Paleozoic ichthyoliths in geology has been extremely limited due, in part, to the taxonomic problems involved in their identification and the lack of adequate documentation affording comparisons of elements from various studies. Part II of a catalog of 156 Late Pennsylvanian ichthyoliths consists of diagnoses and illustrations mainly of teeth. Each ichthyolith has been identified by a coded, utilitarian classification system.

ISSN:0272-4634    

DOI:10.1080/02724634.1983.10011944

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

New preparation of the British Museum specimen ofArchaeopteryxhas exposed the left side of the braincase and the sagittal suture. The skull is much broader and more bird-like than earlier interpreted by deBeer (1954), supporting the estimates of brain size by Jerrison (1973). The braincase has an elongate laterosphenoid and parietal. There is no sagittal crest. The prootic is ven-trolaterally depressed, with several pneumatic foramina. There is a single cotyle for the quadrate, formed by the otoccipital and prootic. The skull appears to have had a squamosal of unusual form.Arachaeopteryxdiffers from theropod dinosaurs in the morphology and position of the quadrate articulation, the structure of the prootic, and the morphology of the occiput.

ISSN:0272-4634    

DOI:10.1080/02724634.1983.10011945

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

The late Quaternary stream sediments and clay of Saltville Valley, southwestern Virginia, have yielded vertebrate fossils since 1782. Excavations in 1980 and 1981 uncovered 49 associated bones of an extinct musk ox skeleton (MARSH 1). MARSH 1 provides new information on the nature of the postcranial skeleton of extinct musk oxen, and information on traumas, disease and somatic degeneration experienced by this individual in life. Taphonomic analysis suggests that MARSH 1 died between early spring and early fall (probably spring), that carnivore activity began at or soon after death, and that all or most of the remaining skeleton was entombed by clay sediments soon after death.

ISSN:0272-4634    

DOI:10.1080/02724634.1983.10011946

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

The microtine mousePitymys meadensisHibbard, a species indicative of the late Irvingtonian mammal age in the United States, is present in a fauna of Rancholabrean age in the Valley of Mexico at El Tajo de Tequixquiac. It is closely related to the livingPitymys quasiaterof Sierra Madre Oriental. Following the reasoning of Van der Meulen, the species group ofPitymys pinetorumis recognized as a distinct North American lineage and the North American speciesP. meadensis(fossil),P. quasiater, andP. nemoralisare considered more closely related to Old World species ofPitymys, some of which have been placed in the genusNeodon. Pitymysand its immediate ancestorAllophaiomysare known from Europe and Asia in early Irvingtonian time.Allophaiomysalso dispersed southward from Beringia into North America in early Irvingtonian time, where thepinetorumspecies group developed from it in late Irvingtonian time. Thepinetorumspecies group seems always to have been restricted to the dry steppes of the northern Great Plains and to the forests well east of the Mississippi River. Thequasiaterspecies group dispersed from Beringia into North America in late Irvingtonian time and now survives partly in geographic asylum in central Mexico and the southern United States, as well as in southern Asia and southern Europe. It also survives partly in ecologic asylum withMicrotus, a more dominant microtine genus, in the more northerly parts of the United States and Europe. The genus is distinctly separate fromMicrotusand is here recognized as having full generic status.

ISSN:0272-4634    

DOI:10.1080/02724634.1983.10011947

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

ISSN:0272-4634    

DOI:10.1080/02724634.1983.10011948

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

ISSN:0272-4634    

DOI:10.1080/02724634.1983.10011949

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

ISSN:0272-4634    

DOI:10.1080/02724634.1983.10011950

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor