摘要:

The monotypic family †Ostariostomidae Schaeffer, 1949 is represented by a single specimen †Ostariostoma wilseyiSchaeffer, 1949. This unique and enigmatic fossil is the impression of the left side of a complete, articulated skeleton from Upper Cretaceous or lower Paleocene freshwater deposits of the Livingston Group in Montana. It was originally described based on the incompletely prepared type specimen and identified as a clupeoid. Based on a more complete preparation of the holotype, we redescribe †O. wilseyiin previously unknown detail and reexamine its phylogenetic relationships. It clearly is not a clupeoid because it lacks all known derived characters of Clupeomorpha. Unfortunately, even based on the additional morphological information available to us, we were unable to clearly identify †Ostariostomaeven to superorder. Our questionable assignment of †Ostariostomato Osteoglossomorpha (possibly a hiodontoid) is not strongly supported and needs to be further tested with additional material, should it be discovered.

ISSN:0272-4634    

DOI:10.1080/02724634.1991.10011412

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Seismosaurus halli, gen. et sp. nov. (Sauropoda, Diplodocidae) is a new large sauropod from the Brushy Basin Member of the Morrison Formation (Upper Jurassic/Lower Cretaceous) of central New Mexico. The holotype is a partially articulated skeleton consisting to date of approximately 20 caudal vertebrae, five sacral vertebrae, eight dorsal vertebrae, partial pelvis, five chevrons, and ribs. Distinguishing features include the structure of the caudal vertebrae, pelvis, and chevrons. The extraordinary dimensions of these bones indicate an axial length of 39–52 meters.

ISSN:0272-4634    

DOI:10.1080/02724634.1991.10011413

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Articulated specimens of fish recovered from the Paskapoo Formation, of Tiffanian (Paleocene) age, near Red Deer, Alberta, are described as a new genus and species of smelt (Family Osmeridae). The new smelt is characterized by a long, toothed mandible and premaxilla and a slender, toothless maxilla, in combination with the virtual absence of teeth inside the mouth and a distinct second ural centrum. Cladistic analysis of osteological features of osmerids and several outgroups indicates that the new genus is most closely related toPlecoglossus, a Recent genus not always included in the family. These two in turn are more closely related to a derived clade of osmerid genera (Allosmerus, Osmerus, Spirinchus, Thaleichthys) than they are to primitive osmerids (HypomesusandMallotus). Anal fins of the new fish are sexually dimorphic, and several presumed males probably have breeding tubercles. Possibly the fish became stranded after attempting to spawn during a high-water stage. Anadromous life histories, which characterize many modern smelt species, may well have originated prior to the Paleocene. The Joffre Bridge fossil site, however, is so distant from Paleocene seas that it is unlikely that these particular fish were anadromous.

ISSN:0272-4634    

DOI:10.1080/02724634.1991.10011414

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

This study focuses on the variability of dental morphology and the relationships of the earliest arctocyonid species. Analysis of arctocyonid premolars and molars from the Bug Creek Anthills local fauna (Hell Creek Fm., Puercan, Montana) shows far wider ranges of variation of many dental characters than were previously recognized. Based on morphological and morphometrical differences, two additional species,Oxyprimus erikseniandMimatuta morgoth, are distinguished fromProtungulatum donnaewithin the arctocyonid sample from the Bug Creek Anthills local fauna. Cladistic analysis of 18 dental characters ofO. erikseni, P. donnae, M. morgothand the Late Cretaceous eutherian outgroup taxa suggests thatP. donnaeandM. morgothform a monophyletic group to the exclusion ofO. erikseni. New data suggest that it is necessary to modify the stratigraphic ranges of these arctocyonid species. In order to ensure the reliability of the biochronological sequence of the Bug Creek channel deposits based on the number of arctocyonid species, it is also necessary to further assess the ranges of dental variations of arctocyonids with larger samples of specimens from other Bug Creek channel deposits in addition to Bug Creek Anthills.

ISSN:0272-4634    

DOI:10.1080/02724634.1991.10011415

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

A new vertebrate fauna has been recovered from the Dogtown Member of the Torreya Formation, Hawthorn Group (early to middle Miocene), northern Gadsden County, Florida. Fossils were recovered from four fuller's earth clay mines. This new fauna, called the Willacoochee Creek Fauna (WCF), contains at least 68 vertebrate taxa, including 29 mammals, from marine, freshwater, and terrestrial environments. The WCF is restricted to the early Barstovian land-mammal age based on the presence ofCopemys, Perognathus, Rakomeryx, andTicholeptus, and the overlapping chronologic ranges of 8 other mammals.Lanthanotherium, Perognathus, and a squalodont whale are reported from the southeastern U.S. for the first time. Biochronological range extensions into the early Barstovian are proposed forLanthanotherium, Anchitherium clarenceiand “Merychippus” primus. The WCF is the first well documented early Barstovian fauna in the southeastern U.S., thus filling a large gap in the temporal distribution of vertebrate faunas in the region. The Torreya Formation records a transition from early Hemingfordian to early Barstovian faunas. Important faunal events include the transition from parahippine to merychippine horses and their subsequent diversification, and the local first appearances ofCopemys, Mylagaulus, andPerognathus. The WCF is the youngest vertebrate fauna known from the Torreya Formation and provides a new upper age limit to that unit. The occurrence of the Midway Local Fauna (late Hemingfordian) and the WCF at the same lithostratigraphic intervals indicates the Dogtown Member is time-transgressive, i.e., younger to the north.

ISSN:0272-4634    

DOI:10.1080/02724634.1991.10011416

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Paleoparadoxia weltoni, a new species in the order Desmostylia, is based on the anterior portion of a skeleton. The specimen is from the earliest Miocene (early Saucesian benthonic foraminiferal stage; Arikareean land mammal age correlative) Skooner Gulch Formation exposed near Point Arena, California, and is the geochronologically oldest definite record of this genus. The new species is very similar toPaleoparadoxia tabataifrom slightly younger early Miocene deposits in Japan, but has smaller teeth and distally-expanded incisors.Paleoparadoxia weltoniis distinguished from all other desmostylians by its lack of an m3 hypoconulid and its well-developed p4 paraconid. A phylogenetic analysis of desmostylians tentatively corroborates the monophyly ofPaleoparadoxiaand strongly supports a clade comprisingPaleoparadoxia, Cornwallius, andDesmostylus.

ISSN:0272-4634    

DOI:10.1080/02724634.1991.10011417

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

A change in repository is noted and a complete description is given for IMNH 714/40119, a partialBison alaskensiscranium collected in 1894 along the Snake River in the vicinity of American Falls. This specimen, the first documented fossil from the American Falls local fauna, is morphologically distinct from the larger-hornedB. latifronsand the shorter-hornedB. priscus, both of which are also found in southeastern Idaho. It and other specimens ofB. alaskensisfrom late Pleistocene sediments in the American Falls area demonstrate a morphologic canalization of the species and document that a substantial population ofB. alaskensisinhabited southeastern Idaho. A stratigraphie review ofBisonmaterial from the American Falls area suggests that as many as four species ofBisoninhabited Idaho during the late Rancholabrean and that bothB. latifronsandB. alaskensissurvived well into the late Pleistocene.

ISSN:0272-4634    

DOI:10.1080/02724634.1991.10011418

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

ISSN:0272-4634    

DOI:10.1080/02724634.1991.10011419

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

ISSN:0272-4634    

DOI:10.1080/02724634.1991.10011420

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

ISSN:0272-4634    

DOI:10.1080/02724634.1991.10011421

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor