摘要:

A diverse and well-preserved vertebrate fauna occurs in Early Devonian rocks of the Delorme Formation in the southern Mackenzie Mountains, Northwest Territories, Canada. The osteostracans of this fauna include the new cornuate speciesWaengsjoeaspis nahanniensisand Diademaspis? mackenziensis. Specimens of the latter species had been described in 1976 by Dineley and Loeffler as “Cephalaspissp. indet.” The cornuate originally described as “?Cephalaspis gabrielsei” Dineley and Loeffler, 1976 is here assigned to the new genusSuperciliaspisand more fully described. Other taxa include a possible example ofParameteoraspissp. and several other indeterminate cornuates. Only dermal bone has been preserved, but preservation of its external and internal surfaces is excellent. Conspecific osteostracan specimens demonstrate a wide variety of overall proportions, due to differing amounts and directions of compaction. Some preferential orientation of corpses on bedding planes has been seen and several examples of both single-species and multiple-species mass-death aggregations occur.

ISSN:0272-4634    

DOI:10.1080/02724634.1994.10011561

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The Upper Pennsylvanian sedimentary rocks exposed in the Kinney Brick Company quarry, central New Mexico, contain a diverse megaflora with abundant foliage of the pteridospermSphenopteridium manzanitanum. A few of the frond fragments carry many small (to 2.0 mm in diameter), compressed spherical bodies, which occur as linear or random groups on both foliar rachises and laminae; also present are two compact, isolated aggregates not attached to any organic substrate. The individual bodies are delimited by a thin, amorphous wall that evidently was membranous, flexible, and adhesive, forming flattened areas of mutual contact. These bodies are interpreted as animal eggs. Their association with spirorbid worm tubes and other evidence indicates that the eggs were deposited under water, on floating or suspended vegetation or in compact, unattached masses. Neither terrestrial nor aquatic invertebrates yield satisfactory clues as to the egg source. However, the aquatic or semi-aquatic vertebrates (fishes and amphibians) are both feasible candidates, with the preponderance of evidence of comparative egg morphology and ovipositing strategies weighing in favor of a probably chondrostean origin for the Kinney eggs. They represent the oldest known vertebrate egg masses.

ISSN:0272-4634    

DOI:10.1080/02724634.1994.10011562

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A new sphenodontian lepidosaur referable toClevosaurusSwinton, 1939,C. bairdi, is described from the McCoy Brook Formation (Lower Jurassic: Hettangian) of Nova Scotia, Canada. It is most closely related toC. mcgilliWu, 1994 from the Dark Red Beds of the Lower Lufeng Formation (Lower Jurassic) of Yunnan, China, and differs from the latter mainly in the absence of the hourglass-shaped constriction of the parietals, the shape of the suborbital fenestra, and in features of the marginal dentition. The new taxon is of considerable interest because it represents the first record ofClevosaurusfrom North America. Like many other early Mesozoic continental tetrapods,Clevosaurushad an apparently Pangaean geographic distribution.

ISSN:0272-4634    

DOI:10.1080/02724634.1994.10011563

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The quadrate (incus) bone underwent important evolutionary transformations through the cynodont-mammal transition. The following character transformations played crucial roles in modifying the cynodont quadrate into the mammalian incus: 1) progressively greater rotation of the dorsal plate relative to the trochlea; 2) the contact facet of the dorsal plate becomes concave; 3) development of a constricted neck between the dorsal plate and the trochlea; 4) simplification of the quadrate-cranium joint, resulting in better mobility of the joint; and 5) introduction of a stapedial process (crus longum). The dorsal plate rotation, the concave contact facet, the constricted neck, the mobile joint of the quadrate and the cranium are also present in some advanced non-mammalian cynodonts. Broad phylogenetic distributions of these features suggest that the major features of the incus of early mammals, as represented byMorganucodon, originated much earlier in phylogenetic history among non-mammalian cynodonts. Apomorphies of the quadrate (incus) among the advanced non-mammalian cynodonts favor a sister-group relationship of tritheledontids and mammals. The hypothesis on the postdentary origin of the mammalian tympanic membrane is favored by transformation of the quadrate through the cynodont-mammal transition. Three most important modifications of the quadrate (incus) through the cynodont-mammal transition are: formation of the concave contact facet, progressively greater rotation of the dorsal plate, and decrease in the number of cranial bones articulating with the quadrate. These modifications would simplify the quadrate-cranial joint and increase the mobility of the quadrate (incus) relative to the cranium while a functioning tympanic membrane was maintained on the mandible, improving the sensitivity of the postdentary tympanum.Probainognathusis among the earliest known non-mammalian cynodonts with a concave contact facet and a rotated dorsal plate in the quadrate. Thus we hypothesize that it represents a critical step in the phylogenetic transformation that led to the origin of the modern mammalian middle ear and tympanic membrane.

ISSN:0272-4634    

DOI:10.1080/02724634.1994.10011564

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Remains of a bat,Australonycteris clarkae, gen. et sp. nov., are reported from freshwater clays radiometrically dated at 54.6 million years old in southeastern Queensland, Australia. It is the oldest bat yet recorded for the Southern Hemisphere and one of the world's oldest. Previously, the earliest records for bats came from the Northern Hemisphere and were of Sparnacian age in Europe, Wasatchian in North America, and late early Eocene in North Africa. The North AmericanWyonycteris chalix, originally described as a latest Paleocene bat and as such the world's oldest, is re-examined. Its lack of key bat synapomorphies and overall morphology do not support the claim that it is a bat. Early bats probably entered Australia via Asia rather than South America, although their appearance in Australia predates the final breakup of Gondwana. The Australian fossils described here (a lower molar, upper premolar, edentulous dentary fragment, and part of a periotic) may corroborate the hypothesis that modern bat groups evolved from isolated immigrant archaic bats somewhere in the Southern Hemisphere in the early Eocene.

ISSN:0272-4634    

DOI:10.1080/02724634.1994.10011565

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The earliest Carnivora are known from two families, the Miacidae, which retain M3/m3 and occur first in latest Paleocene (Clarkforkian) rocks, and the Viverravidae, which have lost M3/m3, but are known first in the middle Paleocene (Torrejonian). This paper describes two new genera and species of carnivorans, one (Pristinictis connata) a viverravid and the other (Ravenictis krausei) of uncertain familial affinities, from the early Tiffanian of Alberta and early Puercan of Saskatchewan, respectively; both have a molar structure more primitive than previously known for the order. The new carnivorans allow a reassessment of character state polarities in the early evolution of the Carnivora, thereby providing the opportunity for reexamination of the relationships of carnivorans to other eutherian orders. As a consequence of this study, it appears that carnivorans and creodonts share no uniquely derived character states of the dentition that might indicate they are sister-groups, and that carnivorans evolved from Cretaceous eutherians less specialized dentally than the Palaeoryctidae.

ISSN:0272-4634    

DOI:10.1080/02724634.1994.10011566

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A well preserved, complete skull from the upper part of the Nye Mudstone (early Miocene; late Arikareean or early Hemingfordian correlative) of coastal Oregon is referred to a new species of pinniped,Pinnarctidion rayi, sp. nov. Several additional crania and associated postcranial elements from this same rock unit are referred to cf.Pinnarctidion rayi. Until now,Pinnarctidionwas based on a single species,Pinnarctidion bishopifrom the Pyramid Hill Sand Member of the Jewett Sand in Pyramid Hill, California.Pinnarctidion rayi, sp. nov. is diagnosed by a narrow crest connecting the paroccipital and mastoid process, and a transversely compressed infraorbital foramen.Pinnarctidionis a member of the phocoid clade which includesDesmatophoca, Allodesmus, and the Phocidae.

ISSN:0272-4634    

DOI:10.1080/02724634.1994.10011567

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A new fossil odobenid skull from the late early or early middle Miocene age Moniwa Formation, Miyagi Prefecture, northern Japan, represents a new species of the genusPrototariaTakeyama and Ozawa, 1984.Prototaria planicephala, sp. nov., is distinguished fromP. primigenaTakeyama and Ozawa, 1984, by having a dorsoventrally flattened cranium with a wider rostrum, more derived cheek teeth, and a flattened tympanic bulla. These and other differences indicate thatP. planicephalais a more derived species thanP. primigena. The species ofPrototarialack many of the derived characters seen in the genusNeotheriumKellogg, 1931, which is interpreted as a closely related genus.

ISSN:0272-4634    

DOI:10.1080/02724634.1994.10011568

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Prorastomus sirenoidesis both the oldest and the most primitive sirenian known; it is the only unquestioned sirenian recorded from beds of probable early Eocene age. The unique holotype skull from Jamaica is here redescribed, new material from middle Eocene beds in Jamaica is referred to this species, and two atlases from the late Eocene of Florida are referred to the family Prorastomidae. AlthoughProrastomusappears to have some autapomorphies that exclude it from the direct ancestry of other sirenians, it is the best available approximation to a structural ancestor of the Sirenia. Therefore,Prorastomusis more appropriate than any Recent species as a representative of the order in analyzing the relationships of sirenians to other mammals. Sirenians are cladistically related to some other primitive ungulates as follows: (Arctocyon (Phenacodus (Moeritherium, Sirenia))). The 3.1.5.3 dental formula ofProrastomusand other Eocene sirenians may be a synapomorphy of the order and a reversal of the loss of P5 and M3 postulated by McKenna (1975) to have occurred in early eutherians; or it may be simply a retention of the primitive eutherian formula.Prorastomuswas probably an amphibious but mainly aquatic quadruped that inhabited coastal rivers and embayments. It was probably a selective browser on floating and emergent aquatic plants and, to a minor degree, on seagrasses.

ISSN:0272-4634    

DOI:10.1080/02724634.1994.10011569

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

ISSN:0272-4634    

DOI:10.1080/02724634.1994.10011570

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor