摘要:

A series of polished slabs, cut vertically through aGrallatorfootprint, proved to be very useful in the reconstruction of the walking dynamics of theropod dinosaurs, and to an understanding of the animal‐substrate interactions. The trampled layer comprises a succession of plastic sediments and elastic cyanobacterial laminites, capped by semiliquid carbonate mud. The sections display records of the different pressures exerted onto the substrate by variable morphologic elements of the foot. Consequently it is possible to reconstruct the way the producing dinosaur walked. A progressive shift of the center of gravity is recorded by the different function of the digits in the different movement phases. The IV digit had a dominant function during the touch‐down and the beginning of the weight‐bearing phase. The II digit appears to have played an unexpected dominant function during the whole touch‐down and weight‐bearing phase, with a marked inward tangential translation and a diagonal penetration into the sediment. In the last phases of weight‐bearing and the kick‐off, the III digit had a functional dominance. In the propelling phase, it penetrated deeper than any other into the substrate. Such a study provides evidence for the correct interpretation, as dinosaur footprints, of deformation structures that crop out in the stratigraphic succession.

ISSN:1042-0940    

DOI:10.1080/10420949809386444

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Studying the trackways of extinct animals is one of the few ways to determine social behaviors, especially herding. We present an analysis of footprint data following the method of Alexander (1989) from theCaririchniumtracksite at Mosquero Creek, New Mexico described by Lockley and Hunt (1995a). This analysis indicates that the distribution of the directions and speeds of the trackmakers is consistent with movement as a group. In addition, there is an anticorrelation (correlation coefficient=‐0.36) between footprint size and relative stride in the sense that the larger animals, were exerting less effort than the smaller animals but moving at approximately the same physical speed. As a test of the technique, a Late Triassic tracksite which was not expected to show organized movement was analyzed. This tracksite, Apache Canyon, New Mexico, had tracks of ichnogeneraPseudotetrasauropusandGrallatorwhich show a large scatter in speed and direction.

ISSN:1042-0940    

DOI:10.1080/10420949809386445

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The ichnogenusPalmiraichnuswas erected by Roselli in 1987 to include his formerly described ich‐nospeciescastellanosi, and a new one,minor, herein considered a junior synonym of the former. Shape, lining and closure clearly show that these traces are fossil bee cells.Celliforma, the other ichnogenus for non‐clustered fossil bee cells, includes two ichnospecies,bedfordi (=septata) (n. syn.)andpinturensis, which share withPalmiraichnus castellanosithe presence of antechambers and hardened cell walls. This combination of features is characteristic of certain groups of short‐tongued bees and justifies the inclusion of these ichnospecies inPalmiraichnus.Microscopic structures of cell walls and closures are adopted here for ichnotaxonomic purposes and for comparing fossil with extant cells revealing that they are useful ichnotaxobases with respect to the problematic fossil bee cell ichnotaxonomy. The micro‐structure of the cell walls and closures of the three ichnospecies ofPalmiraichnusare compared. The presence of antechambers and particularly of the thickened cell rears suggest a relationship betweenPalmiraichnus castellanosiandUruguay, an ichno‐taxon also attributable to bees. However, inUruguayichnospecies. cells are grouped in well‐defined clusters, whereas inPalmiraichnus castellanosi, cells occur isolated in paleosols, and no intermediate morphologies are known between the two ichnogenera.P. castellanosi, the focus of our study, is also compared with oxaeid cells revealing similarities in size and wall microstructure and differences in microstructure of closures and cell rears.

ISSN:1042-0940    

DOI:10.1080/10420949809386446

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Peculiar columnar structures in Permian chert and sandstone beds in western Wyoming, southwestern Montana, northwestern Utah and northeastern Nevada occur in four distinct preservational forms. All represent variously preserved, large vertical burrows, here namedSkolithos grandis, new ichnospe‐cies. The typical burrow cross‐sections are elliptical with dimensions varying but commonly within the range 3×4 cm to 5×7 cm. Form I is basically unaltered, sandstone‐filled specimens with meniscus structure and is present in sandstones in SW Montana. Form II consists of silicified specimens with a surrounding, secondary chert mantle, and occurs in chert rocks in NE Nevada and NW Utah. Form III, occurring in SW Montana and NW Wyoming, is similar to Form II, but the spectacularly abundant and crowded specimens exhibit “knee‐bends” and most of its host rock has been lost. Form IV consists of sandstone filled specimens that experienced some deformation during compaction of the chert host rock. The longest exposed specimens, up to approximately 6 meters tall, belong to the silicified Form III. They likely derived their silica from their original host sediment, which contained a high percentage of sponge spicules. Bed collapse, probably aided by silica loss in the host sediment and by tectonic movements, resulted in the characteristic knee‐bends of Form III columns.

ISSN:1042-0940    

DOI:10.1080/10420949809386447

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A historical survey of the discovery of footprints of iguanodont dinosaurs is presented, from the first reports in 1846 to the present. Reasons are given for considering the ichnogeneraIguanodonichnusandCamptosaurichnusto be problematical and respectively comprising the footprints of sauropods and theropods; consequently, no valid ichnogenus has been available to accommodate those of typical iguanodonts. The desirability of selecting a type series ofIguanodonfootprints from the Early Cretaceous Purbeck Beds of southern England, rather than from the somewhat later Hastings Beds (Weal‐den), is explained. The new ichnogenusIguanodon‐tipusis proposed; its type ichnospecies, I.burreyi, is illustrated and discussed.

ISSN:1042-0940    

DOI:10.1080/10420949809386448

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Nereites(orNeonereites) biserialisis described from the Anyao Formation. It is associated with a suite of facies‐crossing trace fossils which are together characteristic of a relatively deep water environment The status ofVagorichnusis questioned: it may better be referred toGordia, intergrading withHelminthopsis.

ISSN:1042-0940    

DOI:10.1080/10420949809386449

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:1042-0940    

DOI:10.1080/10420949809386450

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The Tracks of Triassic Vertebrates: Fossil Evidence from North‐West England by Geoffrey Tresise with William A.S. Sarjeant, December 1997. The Stationery Office, St. Crispins, Duke Street, Norwich, NR4 6RT, UK. xii+204 pp., UK£65–00.

ISSN:1042-0940    

DOI:10.1080/10420949809386451

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:1042-0940    

DOI:10.1080/10420949809386443

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor