摘要:

A new species of psittacosaur,Psittacosaurus xinjiangensis, is based on one articulated skeleton and additional disarticulated material from several individuals. Diagnostic features of the species include an anteriorly flattened jugal horn, an unusually high denticle count on maxillary and dentary crowns, a proportionately narrow iliac postacetabular process, and ossified tendons that extend along the tail.

ISSN:0272-4634    

DOI:10.1080/02724634.1988.10011724

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

A new psittacosaur species,Psittacosaurus meileyingensis, is based on a well preserved skull with referred cranial and postcranial remains. The skull is tall relative to its length and has a subcircular profile. Distinctive characteristics of the new species include a low horn on the quadratojugal and a prominent ventral flange on the dentary.

ISSN:0272-4634    

DOI:10.1080/02724634.1988.10011725

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Two lower jaws of the Judithian didelphidAlphadon halleyiwere recovered from the Egg Mountain locality, Two Medicine Formation, near Chouteau, Montana. These are the first mammalian fossils reported from this formation and they document for the first time the association of M, through M4inA. halleyi. Of the small, Judithian species ofAlphadon, A. halleyiSahni,A. sahniiLillegraven and McKenna, andA. attaragosLillegraven and McKenna were established on isolated lower teeth. OnlyA. russelliFox from the Oldman Formation was established on associated upper and associated lower molars. These species were distinguished by differences in size and subtle morphological features. The new material from the Two Medicine Formation documents the changes in size of the teeth in a single lower molar dentition and provides the basis for a test of the validity of the small Judithian species ofAlphadon. A. praesagus, A. russelli, andA. halleyiare recognized as members of the Judithian faunas.A. sahniimay be a valid species or might be based on a sample of larger teeth ofA. halleyi.

ISSN:0272-4634    

DOI:10.1080/02724634.1988.10011726

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The largest and best preserved complete specimen of the unusual lungfishConchopoma edesiis described. The specimen was found in a Middle Pennsylvanian concretion from the Mazon Creek. The orbital region is particularly well preserved, including a sclerotic ring, the first described in a post-Devonian lungfish. The large F bone and the position of one of the Q bones between the F and one of the E bones are new features of the species. There is evidence of a hypohyal. The pelvic fins are large and leaf-shaped, unlike the long narrow pelvic fins preserved on other specimens. The variation in fin shape is probably a sexual dimorphism. Evidence thatConchopomashed its dentition during growth confirms its closer affinity with the other denticle-shedding dipnoans, such asUranolophusandGriphognathus, than with species bearing organized dental plates in their upper and lower jaws such asDipterus, Chirodipterus, andNeoceratodus.

ISSN:0272-4634    

DOI:10.1080/02724634.1988.10011727

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The vast majority of the abundant fossil sirenian remains from the Bone Valley phosphate mining district (chiefly in Polk and Hillsborough counties, Florida) represent a single species of dugongid,Metaxytherium floridanumHay, 1922. The osteology of this species is described here in detail. Most or all of these specimens apparently come from Units 4–5 of the lower Bone Valley Formation and are late middle Miocene (early Clarendonian) in age.M. ossivallense(Simpson, 1932) is a junior subjective synonym ofM. floridanum. M. calvertenseKellogg, 1966, and “Hesperosiren” Simpson, 1932, are not represented in the Bone Valley Formation. Specimens are also reported here from elsewhere in Florida, mainly Alachua County. Some or all of these are later than the typical Bone Valley form, being of late Clarendonian or early Hemphillian age, and some of them, here termedMetaxytherium, cf.M. floridanum, seem to represent a slightly more advanced stage of evolution.M. floridanumhad a strongly deflected rostrum adapted to bottom-feeding and very small, subconical, enameled tusks. It is practically indistinguishable from the contemporaneousM. mediumof western Europe; however, the recency of their common ancestry remains to be clarified. ApparentlyM. floridanumwas endemic to the West Atlantic and became extinct without issue by the end of the Miocene.

ISSN:0272-4634    

DOI:10.1080/02724634.1988.10011728

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The tridactyl horseHipparion(s.l.) has long attracted the attention of paleontologists and geologists alike for its potential use as a stratigraphic and paleoenvironmental index. A central dogma surrounding this horse's record is that it first occurred abruptly and instantaneously throughout the Old World ca. 12.5 Ma, heralding a general late Miocene environmental shift from forest to savanna ecosystems. We present data on the oldest known Central European hipparions, “Hipparion”primigenium(s.s.), that bear on these issues. Our analysis of the local Vienna Basin stratigraphie sequence and Paratethys geochronology suggests that hipparion's first provincial occurrence was ca. 11.0–11.5 Ma. We falsify the hypotheses of an Old World “HipparionDatum” and the purported initial association of this horse with savanna habitats. An explicit cladistic analysis of “Hipparion”primigenium(s.s.), its North American sister taxonCormohipparion occidentale, and several Old World primitive hipparions (“Group 1”) suggests that several distinct lineages may have been derived from “Hipparion”primigenium(s.s.). We attribute trans-Eurasian and North African speciation of “Group 1” horses to provincial environmental change which fragmented species ranges (environmental vicariance), and adaptations to newly emergent ecosystems.

ISSN:0272-4634    

DOI:10.1080/02724634.1988.10011729

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

ISSN:0272-4634    

DOI:10.1080/02724634.1988.10011730

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

ISSN:0272-4634    

DOI:10.1080/02724634.1988.10011731

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

ISSN:0272-4634    

DOI:10.1080/02724634.1988.10011732

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

ISSN:0272-4634    

DOI:10.1080/02724634.1988.10011733

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor