摘要:

Microvertebrate remains are described from five formations (Pacoota Sandstone, Horn Valley Siltstone, Stairway Sandstone, Stokes Formation, Carmichael Sandstone) in the Ordovician sequence of the Amadeus Basin, central Australia. Two new genera and species are erected for scales and other elements with distinctive morphology and histology. Other material is referred to indeterminate species of the agnathan generaArandaspisandPorophoraspispreviously described from central Australia, andSacabambaspispreviously described from the Ordovician of Bolivia. The most common vertebrate from the Stokes Formation is referred toAreyonga oervigi, gen. et sp. nov., a form taxon provisionally assigned to the Chondrichthyes. Scales of this species apparently lack a base, and are made of an atubular laminar surface tissue of uncertain histology. Mode of scale growth was similar to that of the Early Devonian formPolymerolepis. If correctly interpreted, this taxon is the oldest chondrichthyan and/or gnathostome known from the fossil record. The form taxonApedolepis tomlinsonae, gen. et sp. nov. contains scales with possible osteocyte spaces in the basal tissue, and a crown composed of dentine covered with an enamel-like surface layer which also lines chambers of a pore canal system. Affinity to arandaspidid pteraspidomorphs may be indicated by a similar system of pores opening to the surface. A pore-canal system, and bone rather than aspidin, may have been primitively present in agnathans. Indeterminate remains from the early Arenig and Caradoc (Horn Valley Siltstone, Stokes Formation) may include endoskeletal ossification. These new microvertebrate faunas are assigned to four assemblages ranging in age from early Arenigian to Caradocian (Bendigonian-Eastonian). They have biostratigraphic potential for age control in Ordovician marginal marine sediments, and are important in demonstrating new combinations of hard tissue types at the beginning of the vertebrate fossil record.

ISSN:0272-4634    

DOI:10.1080/02724634.1997.10010948

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The ceratodont lungfishMetaceratodus wollastoniis described from new material from central and southern Australia, and three additional species,Metaceratodus ellioti, Metaceratodus bonei, andMetaceratodus palmeriare included in the genus.M. elliotiandM. boneiare new species, andM. palmeri, originally described asCeratodus palmeri, has been reassigned. The current determinations of species are based on morphological characters.M. wollastoniis found in Lower and Upper Cretaceous deposits in southeast and central Australia.M. elliotiis confined to the Upper Cretaceous of southeast and central Australia.M. boneiis found in the Namba and Etadunna formations in central Australia, late Oligocene to middle Miocene in age, as well as a single record from a possible Pleistocene deposit.M. palmericomes from strata belonging to the Pliocene and Pleistocene of eastern Australia. At least one species ofMetaceratodusalso occurs in the Lower Cretaceous Coli-Toro Formation of South America.

ISSN:0272-4634    

DOI:10.1080/02724634.1997.10010949

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Hundreds of bone elements and teeth were recovered between 1990 and 1993 from the late Miocene-Pliocene site of Lothagam, in northern Kenya. One of the fossils found in deposits dated slightly younger than 4 my was the occluded upper and lower jaw ofSindacharax, an extinct characid.Sindacharaxhad previously primarily been known from isolated teeth, and this recovery provides much-needed information on the morphology of the dentaries, premaxillae, and position of teeth. The jaws have been referred to a new species,Sindacharax greenwoodi. Sindacharax greenwoodidiffers primarily from the other two species ofSindacharaxby clearly distinguishable tooth shape and cusp patterns. While cusped ridges on the teeth are the dominant character of the genusSindacharax, the “discovery” of cusped ridges on teeth of a little-known modern species,Alestes stuhlmanni, suggests that eitherSindacharaxbe subsumed underAlestes, or, more likely, thatA. stuhlmannibe transferred toSindacharax.

ISSN:0272-4634    

DOI:10.1080/02724634.1997.10010950

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Reexamination of the dentition ofGrippia longirostris(Ichthyosauria) provides new information, and also reveals errors in the original descriptions. A dental groove is present inG. longirostris, with shallow sockets at the bottom; hence, the implantation is subthecodont, at least in the posterior part of the mandible. There are two rows of maxillary teeth as originally described, but it seems that the lingual row comprises replacement teeth for the labial row, and that each replacement tooth is positioned distolingual of its predecessor. The anterior teeth are not well preserved in any of the specimens. The posterior teeth are blunt but rarely spherical, and are small both absolutely and relative to the skull width. The dentition and the jaw structure suggest a wide range of prey items, rather than strict durophagy as previously proposed. The dentition ofG. longirostrisis similar to that ofUtatsusaurus hataiiin general tooth structure, tooth implantation and replacement, and in relative tooth sizes, in contrast to previous interpretations.

ISSN:0272-4634    

DOI:10.1080/02724634.1997.10010951

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

New sphenodontian material is described from the Early Cretaceous (?Berriasian) of Morocco. Two taxa are recognized. The first is represented by a dentary and, probably, a partial maxilla. Comparison with known Jurassic and Early Cretaceous genera suggests the Moroccan form is sufficiently distinctive in its tooth and jaw morphology to warrant the erection of a new genus and species,Tingitana anoualae. The second taxon, sphenodontian B, is represented by a small dentary which bears a superficial resemblance to that ofTheretairus(Upper Jurassic Morrison Formation, North America) in its simple alternating dentition—a hatchling condition. A fragment of a larger dentary bearing the remains of an anterior caniniform tooth may also be attributable to this form. Sphenodontian B differs fromTingitanain overall size, hatchling tooth number, and in the shape of the coronoid process of the dentary, but cannot be named without more diagnostic material.

ISSN:0272-4634    

DOI:10.1080/02724634.1997.10010952

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The Albian sphenodontianPamizinsaurus tlayuaensis, gen. et sp. nov., from the Tlayua Quarry, Central Mexico, is described. The holotype is a posthatchling characterized by the presence of rows of small rounded osteoderms transversally oriented, relatively few hatchling teeth each with well-developed ridges, and a posteriorly displaced ventral process of the mandibular symphysis at an early ontogenetic stage. A small retroarticular process, long central region of the pterygoid, and the narrowness of the posterior end of the interpterygoid vacuity suggest sister-group relationships with sphenodontines + eilenodontines. The conspicuous dermal skeleton is similar to that of helodermatids, suggesting that it could have served to protect against predation in open environments. This unique structure argues against the idea of low morphological diversity within sphenodontians.Pamizinsaurusis the latest occurring fossil sphenodontian.

ISSN:0272-4634    

DOI:10.1080/02724634.1997.10010953

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A detailed description of the early archosaurSarmatosuchus otscheviSennikov, 1994, from the Middle Triassic Donguz Formation of southern European Russia, is presented. New morphological data forms the basis of a preliminary investigation of the phylogenetic relationships between a selection of the earliest archosaurs. A parsimony analysis based on 9 taxa and 35 characters recovers two most parsimonious trees that support the referral ofSarmatosuchusandFugusuchusto a proterosuchid clade, as well as the paraphyly of the Proterosuchia. Characters from the structure of the braincase are more homoplastic than those from the rest of the skeleton. The presence ofSarmatosuchusin the Middle Triassic affords evidence that the proterosuchids were a more diverse and persistent clade than has been previously envisaged. Evidence suggesting that proterosuchids may have existed with erythrosuchids and early crown-group archosaurs in the Middle Triassic requires a revision of our understanding of the early part of the archosaurian radiation.

ISSN:0272-4634    

DOI:10.1080/02724634.1997.10010954

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The first archosaurs from the Middle Triassic were described unwittingly by Sir Richard Owen in the 1840s. He combined a variety of archosaurian postcranial elements with skull material of temnospondyls, thus producing his image of giant Triassic frogs. Archosaur bones have been collected from Middle Triassic (Anisian) sediments of Warwick and Bromsgrove in the West Midlands, and more recently, from south Devon. Some of the vertebrae and pelvic elements belong to the poposauridBromsgroveia, and other elements and teeth to unidentified archosaurs, one perhaps a dinosaur. The English faunas help fill a gap in knowledge of archosaurs in the early part of the Middle Triassic. IfBromsgroveiais a poposaurid, it is the oldest member of a family known otherwise from the Late Triassic of North America.

ISSN:0272-4634    

DOI:10.1080/02724634.1997.10010955

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A new protosuchian,Sichuanosuchus shuhanensis, sp. nov. from the ?Lower Cretaceous of Sichuan (China), is distinguished from other known basal crocodyliform archosaurs primarily by the subdivision of the small antorbital fenestra into anterior and posterior openings, the presence of a large, caniniform first maxillary tooth, followed by seven teeth with low, chisel-like crowns, and the posterior palpebrai being larger than the anterior one. Phylogenetic analysis using 128 characters for 29 crocodyliform taxa supports the monophyly of Protosuchia.Sichuanosuchusis most closely related toShantungosuchusfrom the Upper Jurassic and Lower Cretaceous of China. These two taxa, together withGobiosuchusfrom the Upper Cretaceous of Mongolia, appear to form a clade of late Mesozoic basal crocodyliform reptiles.

ISSN:0272-4634    

DOI:10.1080/02724634.1997.10010956

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A reconstruction of the terrestrial locomotion of pterosaurs is presented, based onPteraichnustrackways. The pterosaurs that made the trackways were walking quadrupedally with a digitigrade manus and plantigrade pes at approximately 1 m/s. Their posture was erect rather than sprawling or semi-erect. The trackways suggest that bird-like bipedal and sprawling to semi-erect postures, and the restrictive interpretations of limb and girdle joint mobilities upon which they are based, may be incorrect.

ISSN:0272-4634    

DOI:10.1080/02724634.1997.10010957

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor