摘要:

The standard-length frequency histogram for the Eocene catostomidAmyzon aggregatumfrom the Horsefly beds of British Columbia shows a series of distinct peaks. The peaks, or modes, are interpreted as averaged year classes produced by repeated, annual winter deaths of the fishes. Fishes interpreted as being aged 0,+ at death were about 40 mm SL (standard length), with peaks for successive averaged year classes at about 80 mm (1+), 125 mm (2+), 175 mm (3+), and 225 mm SL (4+). For most individuals, body depth increased rapidly between 60 and 120 mm SL, or between the ages of 1+ and 2+. These individuals are interpreted as females. Some individuals show no apparent change in bodth-depth to standard-length growth parameters, remain relatively slender and elongate, and are interpreted as males.

ISSN:0272-4634    

DOI:10.1080/02724634.1984.10011966

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Albionbatrachus wightensisn.gen. et sp. from the late Eocene of the Isle of Wight is the only representative of the family Palaeobatrachidae known from England.A. wightensisdiffers from most palaeobatrachids in having dorsal skull bones with prominent sculpturing and an hourglass-shaped frontoparietal bone. It agrees with other members of the family in having a synsacrum, procoelous vertebrae, and an azygous frontoparietal. The fossil palaeobatrachid described asPalaeobatrachussp. by Vergnaud-Grazzini and Hoffstetter from Oligo-Miocene deposits at Laugnac, France, shows close resemblance toA. wightensisand is also included in the new genusAlbionbatrachus.

ISSN:0272-4634    

DOI:10.1080/02724634.1984.10011967

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Members of the family Baenidae cease significant growth and co-ossify the shell as adults. Recognition of adults allows size to be effectively used as a means of taxon discrimination in taxonomic, stratigraphie, and ecologie studies. The feature is used to discriminate the Eocene generaBaenaandChisternonand trace their increase in size through time.

ISSN:0272-4634    

DOI:10.1080/02724634.1984.10011968

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The first skull and an additional mandible ofProsthennops elmoreiWhite are described and the species is transferred toMylohyusCope on the basis of several derived characters including molariform premolars, post-canine diastema length greater than length of cheek tooth series, and posterior position of the orbit. A distinctive feature of this species is its laterad projecting, inflated triangular zygomatic process. In other knownMylohyusskulls (all from the Pleistocene) the zygoma is not expanded into a laterad projecting process, but is inflated anterior to the glenoid fossa and its ventral surface provides a broad origin for M. masseter lateralis. The wing-like zygomata ofM. elmoreiare probably primitive forMylohyus.

ISSN:0272-4634    

DOI:10.1080/02724634.1984.10011969

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

A new genus and species,Nakalimys lavocati, is described from the Nakali locality, Kenya, of about 10 Ma. This muroid rodent is assigned to the Rhizomyidae and is most similar toKanisamys indicusfrom the Miocene of Pakistan, with which it was originally considered congeneric.Nakalimys, with other rodents and vertebrates, points to interchange between eastern Africa and southern Asia earlier than 10 Ma, before a more recent period of strong faunal similarity at about the beginning of the Pliocene.Nakalimyspossesses many primitive characters, but was not directly ancestral to fossil and extantTachyoryctesof Africa.

ISSN:0272-4634    

DOI:10.1080/02724634.1984.10011970

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

There is an extensive Pleistocene record, from early Irvingtonian to present, of pocket gophers (genusGeomys) in Florida. Evolutionary trends include the widening of lower cheekteeth and the expansion of the retromolar fossa; these changes resulted in progressively more efficient mastication. Other trends in dental characters include the loss of enamel from the posterior face of P4and a change in the occlusal shape of M3from elongate and bilophate to subtriangular. Mandibular and dental features distinguish early and middle Irvingtonian samples from late Irvingtonian to modern samples, which are referred to the extantGeomys pinetis. The new species may be diagnosed both quantitatively from mandibular characters and qualitatively from characters of the upper dentition.

ISSN:0272-4634    

DOI:10.1080/02724634.1984.10011971

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

ISSN:0272-4634    

DOI:10.1080/02724634.1984.10011972

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

ISSN:0272-4634    

DOI:10.1080/02724634.1984.10011973

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor