摘要:

The Paleozoic fin spinePhysonemus falcatusSt. John and Worthen 1883, from the Valmeyeran St. Louis Limestone of St. Louis, Missouri, has been found on sexually mature males of a small, highly sexually dimorphic chondrichthyan from the Chesterian Bear Gulch Limestone of Montana. An amphistylic suspensorium, cladodont teeth and pectoral fin further characterize this species and the group to which it belongs. The first dorsal spine and fin of males are derivable from a form like that ofStethacanthus altonensis. Males also have elongate rostra and dorsal cranial and fin denticles, while females and juveniles lack denticles, first dorsal fin, or spine. The new genusFalcatus(Order Cladodontida, Family Stethacanthidae) is erected for the species and for the relatedF. hamatusandF. proclivus. Aspects of the sexual dimorphism are discussed;Falcatus falcatus, with many more males than females, fits a behavioral model of male display-courtship and female choice. Possible evidence of lek aggregations is presented.

ISSN:0272-4634    

DOI:10.1080/02724634.1985.10011842

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The first specimen of the giant marine snakePterosphenusLucas is recorded from a carbonate platform environment in the Late Eocene (Jackson Age) of the Crystal River Formation of Alachua County, Florida. The great enlargement of the marrow cavities and concomitant thinning of the vertebral walls are interpreted as specializations to a completely aquatic and fully marine habitus. The Florida specimen indicates thatPterosphenuswas not limited to estuarine and low salinity environments as previously proposed.

ISSN:0272-4634    

DOI:10.1080/02724634.1985.10011843

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Egretta subfluvia, n. sp. is described from a nearly complete right tarsometatarsus from the Withlacoochee River 4A local fauna. It is a small species ofEgrettaand is the first paleospecies of this genus. Examination of the fossil mammals from the Withlacoochee River 4A local fauna documents the North American Land Mammal Age of this local fauna as late early Hemphillian. Other specimens from the late Miocene and early Pliocene of Florida show the existence of unidentifiable species ofArdea, Egretta, andArdeola. The coracoid and distal end of tarsometatarsus ofArdea polkensisare reported for the first time.

ISSN:0272-4634    

DOI:10.1080/02724634.1985.10011844

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

A study of the major collections of Siwalik hipparionines has resulted in the recognition of two supra-specific groups that we refer to“Cormohipparion” (Sivalhippus) and ?Hipparions.s. The“Cormohipparion” (Sivalhippus) group is the more abundant one in the Siwaliks, and includes at least three species:“Cormohipparion”(Sivalhippus)theobaldi, “Cormohipparion” (Sivalhippus)sp. and“Cormohipparion” (Sivalhippus) perimense. The ?Hippariongroup is monospecific and includes the species ?Hipparion antelopinum. In attempting to ascertain the phylogenetic relationships of these horses we have found no sound basis for falsifying the hypothesis that Old World hipparionine Groups 1–4 are monsophyletic. We derive both Groups 2 and 3 from Group 1. Group “4” is polyphyletic, with part of the original hypodigm most probably referable to Group 2. The“Cormohipparion” (Sivalhippus)group is distantly related to early Vallesian Group 1 hipparionines of probable south Asian origin, and may in turn include the ancestor of the late Miocene East African species“Hipparion” turkanense. ?Hipparion antelopinumprobably originated from a west Asian species ofHipparions.s. The relatively late first occurrence of hipparionines in the Siwalik Province is discussed, and further testing of the“Hipparion”“Datum” concept is recommended.

ISSN:0272-4634    

DOI:10.1080/02724634.1985.10011845

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Two species of soricid insectivores,Paracryptotis rexandSorex powersi, are the first soricids to be reported from the Ringold Formation. They make up a portion of a new stratigraphically separate local fauna, the Blufftop local fauna, from the upper part of the White Bluffs, Franklin County, Washington. This fauna occurs at a stratigraphic position near a paleomagnetic boundary, which has been interpreted as the Gauss-Gilbert boundary but may be an older boundary within the Gilbert. Compared to other Ringold Formation local faunas, the Blufftop l.f. is older than the Taunton l.f. (which on new evidence is closer in age to the Hagerman l.f. of Idaho) and is similar to the underlying White Bluffs local fauna.

ISSN:0272-4634    

DOI:10.1080/02724634.1985.10011846

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Late Miocene to early Pliocene gomphothere proboscideans (Family Gomphotheriidae: Subfamily Anancinae) from the Middle Awash Valley, Ethiopia, were recovered throughout 350 m of strata, representing some 1½ to 2 my. Specimens referred to the genusAnancusfrom the Adu-Asa and Sagantole Formations are more complete and more extensive than any described previously from sub-Saharan Africa. Three evolutionary stages referable toA. kenyensis, as well as a much more derived new form ofAnancus, are recognizable from dental remains.

ISSN:0272-4634    

DOI:10.1080/02724634.1985.10011847

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor