Dentary Morphological Variation in Clevosaurus brasiliensis (Rhynchocephalia,Clevosauridae) from the Upper Triassic of Rio Grande do Sul,Brazil

Clevosaurus was a cosmopolitan rhynchocephalian genus, known from the Late Triassic to the Early Jurassic. In South America this genus is represented by C. brasiliensis, an important component of the Linha São Luiz taphocoenosis, on the top of the Norian Santa Maria 2 Sequence of Southern Brazil. The best preserved and most abundant bone elements of C. brasiliensis are dentaries, in which variations of shape and size are observed. The aim of this study is to describe and evaluate the variation, using geometric morphometrics methods. Geometric morphometric analysis of 10 specimens highlights variations in relative size of the dentary. Most of the variation observed for PC1 (83.3%) is likely related to ontogeny, and PC2 (10.0%) is likely related to taphonomic signatures. The development patterns observed, such as the growth of the dentary, consists of differential growth in length between the posterior portion of the dentary, that grows at a higher rate, regarding the anterior portion of the element. This allometric growth is similar to what is observed in other rhynchocephalians and is accompanied by the allometric skull growth, similar to the trend exhibited by clevosaurs. The taphocoenosis is bimodal (juveniles and adults) with a bias towards adult preservation. Some diagenetic influence is reflected in deformed skulls and this is observed in the tangent-plot. Finally, a strong correlation was detected between the taphonomic signatures and the PC2, regarding specially disarticulation and degree of fragmentation.     

A new sphenodontian (Lepidosauria: Rhynchocephalia) from the Late Triassic of Argentina and the early origin of the herbivore opisthodontians

Sphenodontians were a successful group of rhynchocephalian reptiles that dominated the fossil record of Lepidosauria during the Triassic and Jurassic. Although evidence of extinction is seen at the end of the Laurasian Early Cretaceous, they appeared to remain numerically abundant in South America until the end of the period. Most of the known Late Cretaceous record in South America is composed of opisthodontians, the herbivorous branch of Sphenodontia, whose oldest members were until recently reported to be from the Kimmeridgian–Tithonian (Late Jurassic). Here, we report a new sphenodontian, Sphenotitan leyesi gen. et sp. nov., collected from the Upper Triassic Quebrada del Barro Formation of northwestern Argentina. Phylogenetic analysis identifies Sphenotitan as a basal member of Opisthodontia, extending the known record of opisthodontians and the origin of herbivory in this group by 50 Myr.     

Dinosaurs of France

The French dinosaur record is one of the most extensive in Europe; it ranges stratigraphically from the Late Triassic to the Latest Cretaceous. All major clades of dinosaurs but marginocephalians are known. About 20 species are based on significant material; the theropods are the best represented. Most of these taxa have been described or revised in recent years. Important specimens have been discovered in the Late Triassic of eastern France, the Middle Jurassic of Normandy, and the Late Cretaceous of Provence and Languedoc. The ichnological record is good for the Late Triassic-Early Jurassic, and the Late Cretaceous egg sites are among the richest in the world. To cite this article: R. Allain, X.P. Suberbiola, Palevol 2 (2003) 27–44.     

A systematic overview of fossil osmundalean ferns in China: Diversity variation,distribution pattern,and evolutionary implications

The order Osmundales is a unique fern taxon with extensive fossil records in geological past. Diverse osmundalean fossils have been reported from China, ranging in age from the Late Palaeozoic to the Cenozoic. Most of them are based on leaf impressions/compressions, but permineralized rhizomes are also well documented. In this study, we provide a systematic overview on fossil osmundalean ferns in China with special references on diversity variations, distribution patterns, and evolutionary implications. Fossil evidence indicates that this fern lineage first appeared in the Late Palaeozoic in China. The Late Triassic to Middle Jurassic interval was the radiation stage. From the Late Jurassic onward, fossil diversity declined rapidly. Cenozoic osmundalean taxa are represented by the relict species of Osmunda. Geographically, osmundalean fossils are found from both the Northern and Southern phytoprovinces of China, though variations are documented for geographical ranges. The Chinese fossil records cover almost all important stages for the macroevolution of the Osmundales, and contribute to further understanding of evolutionary processes of this peculiar fern lineage.     

Evidence of osteomyelitis in the dentary of the late Triassic rhynchocephalian Clevosaurus brasiliensis (Lepidosauria: Rhynchocephalia) from southern Brazil and behavioural implications

Clevosaurus was a cosmopolitan Rhynchocephalia genus restricted to the Late Triassic and the Early Jurassic. In Brazil, C. brasiliensis is one of the most conspicuous species collected from the Candelária Sequence (Riograndia Assemblage Zone, Norian age) of the Santa Maria Supersequence. Several jaws of C. brasiliensis are housed in the Laboratório de Paleontologia de Vertebrados of the Instituto de Geociências-UFRGS. Some of these jaws bear a relatively small protuberant bony callus on the anterolateral margin of the dentary, evidenced by a different tissue pattern incorporating small pits and discrete grooves. This pattern closely resembles a common bone infection known in the mandible of the extant Sphenodon punctatus. Although this similarity, the infection may be the result of two possible processes: as consequence of orthal jaw shearing movements during feeding at the moments that the dentary impacts with the enlarged premaxillary tooth or due to injuries produced after fights between conspecific individuals (as is the case for S. punctatus). If the second hypothesis is correct, the same pathological processes probably occurred in the Late Triassic C. brasiliensis indicating that similar ethological conditions were already present at the beginning of the Mesozoic, during the initial radiation of the lepidosaurian clade.     

Liverwort fossils from the Late Triassic of Baiyin City,Gansu Province,and their geological significance

Although liverworts are widely distributed around the world with a large number of extant species, reliable fossil records are relatively rare. Here, we report a new species, Ricciopsis baojishanensis Han and Yan, n. sp. (Ricciaceae) and an unnamed species, Hepaticites sp. from the Late Triassic Nanying’er Formation in Baojishan Basin, Baiyin City, Gansu Province, Northwest China. The generic designation is based on detailed comparison of the gross morphology with related fossil and extant species. The new species is characterized by its rosette-forming thallus, dichotomous branching, ribbon-like segments and entire margins. The current fossils represent the first record of liverwort from the Late Triassic in Baojishan Basin, Gansu Province. Based on the different fossil records of the Ricciaceae, we suggest that these taxa were widely distributed during Late Triassic to Oligocene worldwide, mainly in warm temperate and tropical environments, similar with their current distribution. The discovery of the present fossils indicates that the climate of Baojishan Basin in Late Triassic is warmer and more humid than that of today.     

Rhynchocephalians (Diapsida: Lepidosauria) from the Jurassic Kota Formation of India

Despite their rarity today, rhynchocephalians formed a diverse Early Mesozoic clade with a comparatively good fossil record. They had a Pangaean distribution in the Late Triassic and Early Jurassic, although the Gondwanan record remains more limited than the Laurasian one. We report here on new sphenodontian material from the Jurassic Kota Formation of peninsular India. Two taxa are represented, and both are attributed to new genera. One is a relatively derived sphenodontian with a premaxillary morphology similar to that of the Late Triassic/ Early Jurassic genus Clevosaurus. The other is somewhat more primitive in its morphology, although clearly a crown-group sphenodontian. In addition, three dentary fragments and a partial maxilla signal the presence of a primitive pleurodont lepidosauromorph similar to the basal rhynchocephalians Gephyrosaurus and Diphydonto-saurus from Britain.     

New information on Bobosaurus forojuliensis (Reptilia: Sauropterygia): implications for plesiosaurian evolution

Preparation of the holotype specimen of Bobosaurus forojuliensis, a large sauropterygian from the lower Carnian of northeastern Italy, revealed new morphological data relevant in establishing its phylogenetic affinities among pistosauroid taxa and its relationships with plesiosaurians. Inclusion of B. forojuliensis in two phylogenetic analyses focusing, respectively, on sauropterygians and pistosauroids agreed in placing the Italian taxon as closer to plesiosaurians than to other pistosauroids. The phylogenetic interpretation of Bobosaurus was not biased by assumptions on character weighting, is consistent with its relatively younger age compared to most pistosauroids, extends the fossil record of the plesiosaurian basal lineage back to the Carnian and supports the earliest diversification of the clade during the Late Triassic in agreement with the record of several distinct lineages of rhomaleosaurids, plesiosauroids and pliosauroids in the lowermost Jurassic. Bobosaurus shows that the evolution of the plesiosaurian body plan from the ancestral pistosauroid grade was a step-wise process, and that some of the vertebral and appendicular specialisations of Jurassic and Cretaceous plesiosaurians had already developed in the earliest Late Triassic.     

Diversity variation and tempo-spatial distribution of Otozamites (Bennettitales) in the Mesozoic of China

Otozamites is a representative fossil leaf morphogenus of the extinct Bennettitales, with an extensive distribution during the Mesozoic, especially in China. Understanding the fossil diversity variation and distribution pattern of Otozamites in China will provide information on biodiversity of bennettitalean plants as well as for reconstruction of palaeogeography and palaeoclimate conditions during the Mesozoic. So far, 46 species of this genus have been described in China, excluding unspecified species. The results show that the fossils of Otozamites are extensively recorded in the Late Triassic, and then reach their maximum development in the Early Jurassic, followed by a reduction in diversity in the Middle and Late Jurassic, and finally become extinct at the end of Early Cretaceous. Geographically, they occur in both Northern and Southern Floristic Provinces in the Mesozoic of China, with a relatively higher abundance in the Southern Floristic Province. It implies that the diversity variation and distribution of Otozamites are closely related to the change of the palaeoclimatic conditions. The warm and humid climate prevailed in the Late Triassic and Early Jurassic in South China, propitious to the development of Otozamites. After the Middle Jurassic, dry and hot climate may have caused the lower diversity level and blocked the development of Otozamites; finally at the end of the Early Cretaceous, the frequent arid climate may be a major cause for the extinction of Otozamites.     

The early Triassic rhynchosaur Mesosuchus browni and the interrelationships of basal archosauromorph reptiles

Restudy of the unique diapsid reptile Mesosuchus browni Watson, from the Cynognathus Assemblage Zone (late Early Triassic to early Middle Triassic) of the Burgersdorp Formation (Tarkastad Subgroup; Beaufort Group) of South Africa, confirms that it is the most plesiomorphic known member of the Rhynchosauria. A new phylogenetic analysis of basal taxa of Archosauromorpha indicates that Choristodera falls outside of the Sauria, Prolacertiformes is a paraphyletic taxon with Prolacerta sharing a more recent common ancestor with Archosauriformes than with any other clade, Megalancosaurus and Drepanosaurus are sister taxa in the clade Drepanosauridae within Archosauromorpha, and are the sister group to the clade Tanystropheidae composed of Tanystropheus, Macrocnemus, and Langobardisaurus. Combination of the phylogenetic relationships of basal archosauromorphs and their known stratigraphic ranges reveals significant gaps in the fossil records of Late Permian and Triassic diapsids. Extensions of the temporal ranges of several lineages of diapsids into the Late Permian suggests that more groups of terrestrial reptiles survived the end-Permian mass extinction than thought previously.     

New and little-known grylloblattids of the family Geinitziidae (Insecta: Grylloblattida) from the Triassic and Jurassic of Europe,Asia, and South Africa

The fossil history of the family Geinitziidae is reviewed. New taxa are described in the family: Shurabia hissarica, sp. nov. (Lower Jurassic of Tajikistan), Sh. shartegica, sp. nov. (Upper Jurassic of Mongolia), Sh. serrata, sp. nov. and Ginitzia sagulensis, sp. nov. (both Lower Jurassic of Kyrgyzstan). The subfamily Stegopterinae Sharov, 1961 is synonymized under Geinitziinae Handlirsch, 1906. The genera Minesedes Fujiyama, 1973 and Ominea Fujiyama, 1973 (Upper Triassic of Japan) are synonymized under Shurabia Martynov, 1937 and Geinitzia Handlirsch, 1906, respectively. Geinitzia varia Bode, 1953 (Lower Jurassic of Germany) and Fletchizia picturata Riek, 1976 (Upper Triassic of South Africa) are redescribed from their holotypes. F. kapokraalensis Wappler, 2001 and F. aleda Wappler, 2001 (both Upper Triassic of South Africa) are transferred to the genus Shurabia.     

A New Basal Sauropodomorph Dinosaur from the Lower Jurassic Navajo Sandstone of Southern Utah

Background

Basal sauropodomorphs, or ‘prosauropods,’ are a globally widespread paraphyletic assemblage of terrestrial herbivorous dinosaurs from the Late Triassic and Early Jurassic. In contrast to several other landmasses, the North American record of sauropodomorphs during this time interval remains sparse, limited to Early Jurassic occurrences of a single well-known taxon from eastern North America and several fragmentary specimens from western North America.

Methodology/Principal Findings

On the basis of a partial skeleton, we describe here a new basal sauropodomorph dinosaur from the Lower Jurassic Navajo Sandstone of southern Utah, Seitaad ruessi gen. et sp. nov. The partially articulated skeleton of Seitaad was likely buried post-mortem in the base of a collapsed dune foreset. The new taxon is characterized by a plate-like medial process of the scapula, a prominent proximal expansion of the deltopectoral crest of the humerus, a strongly inclined distal articular surface of the radius, and a proximally and laterally hypertrophied proximal metacarpal I.

Conclusions/Significance

Phylogenetic analysis recovers Seitaad as a derived basal sauropodomorph closely related to plateosaurid or massospondylid ‘prosauropods’ and its presence in western North America is not unexpected for a member of this highly cosmopolitan clade. This occurrence represents one of the most complete vertebrate body fossil specimens yet recovered from the Navajo Sandstone and one of the few basal sauropodomorph taxa currently known from North America.     

QUALITY OF THE TRIASSIC–JURASSIC BIVALVE FOSSIL RECORD IN NORTHWEST EUROPE

Abstract: The quality of the Triassic–Jurassic bivalve fossil record in northwest Europe has been measured using the Simple Completeness Metric (SCM). The SCM has been applied to the fossil record of total bivalve diversity and to the records of different ecological guilds. The Westbury and Lilstock Formations record high SCM values for most ecological groups. The ‘Pre‐Planorbis Beds’ of the lower Lias Group, however, witness a precipitous decline in the completeness of most guilds and emigration of taxa due to localized marine anoxia is a likely cause. Neither variation in lithofacies, shell mineralogy, sedimentary rock outcrop area, nor sequence architecture can convincingly explain the observed patterns of completeness. Our SCM data reveal that the Early Jurassic fossil record of infaunal suspension‐feeding bivalves is significantly poorer than that of epifaunal bivalves. Any differences in the apparent Rhaetian extinction rates between these two guilds should therefore be viewed with caution. Analyses of selectivity during the Late Triassic mass extinction based on studies of global databases appear robust in light of our SCM data. Nevertheless, future investigations of the Triassic–Jurassic benthic marine ecosystem undertaken at a finer‐resolution, may need to account for the poor quality of the Early Jurassic fossil records of certain ecological guilds, such as the infaunal suspension‐feeding taxa.     

First palynological data from the Jurassic South Xiangshan Formation (Nanjing area,China)

The outcrops of the Xiangshan Group have been studied since the beginning of the twentieth century, yielding a rich macroflora (the Xiangshan Flora), mainly from the lower part of the Xiangshan Group (South Xiangshan Formation). Nevertheless, no palynological data have been published so far from the South Xiangshan Formation. The present study provides the first palynostratigraphic data of the South Xiangshan Formation. More than 50 fossil taxa from 30 fossil genera have been identified, allowing for a more accurate dating. The most characteristic taxa are Polycingulatisporites triangularis, Quadraeculina anellaeformis, Manumia delcourtii, Ischyosporites variegatus, Callialasporites turbatus, C. trilobatus, C. minus, and Sestrosporites pseudoalveolatus, suggesting a late Toarcian-late Aalenian age for the South Xiangshan Formation. These results are consistent with previous studies suggesting a middle-late Early Jurassic age for this formation; consequently, the most probable age for the South Xiangshan Formation is late Toarcian (late Early Jurassic).     

New Middle Jurassic record of fern genus Eboracia (Dicksoniaceae,Filicales) and its spatio-temporal distribution in China

As an important component of the Mesozoic flora, the extinct fern genus Eboracia Thomas (Dicksoniaceae, Filicales) is widely reported in China with diverse fossil records. New material of Eboracia lobifolia, represented by a nearly intactly preserved fossil frond, is described herein from the Middle Jurassic Haifanggou Formation in Beipiao of western Liaoning, Northeast China. The frond is lanceolate in gross outline, at least 38.0 cm long, and can be divided into the basal sterile part, the upper fertile part and a transitional part in between. The new discovery confirms for the first time that the frond of E. lobifolia is hemidimorphic rather than holodimorphic. Many in-situ spores were detached from the sori of the fertile pinnae, which are characterized by rounded-tetrahedral shape, smooth surface, distinct border, and a wide, long triradiate crack almost reaching the equator. Comparing with dispersed spores in the same horizon, these in-situ spores seem to be most similar to Cyathidites minor Couper in morphology. A spatio-temporal analysis of Eboracia in China shows that Eboracia with totally four species occurred in a time interval ranging from the Late Triassic to the Early Cretaceous in China, and mostly flourished in the Middle Jurassic; the genus was widely distributed in both the Northern and Southern Phytofloristic Provinces of China, particularly in southern China during the Late Triassic to Early Jurassic, while more abundant and diverse in northern China during the Middle Jurassic to Early Cretaceous.     

Dinosaurs of Switzerland

Until 1960, the record of dinosaurs was rather poor in Switzerland. Between 1960 and 1980, several new localities with plateosaurid remains as well as prosauropod and theropod tracks were found in Late Triassic sabkha and floodplain environments. The discovery of large surfaces with sauropod tracks in the Late Jurassic of the Jura Mountains in 1987 triggered a stream of new data. More than 20 new localities with tracks from both sauropod and theropod dinosaurs in different stratigraphic levels have been found since then. The latest discoveries include trackways of iguanodontids from the Early Cretaceous of the central Swiss Alps and a large Late Jurassic surface with trackways of small sauropods in the northernmost part of the Jura Mountains. The best skeletal record comes from the Late Triassic, with scattered data from the Late Jurassic. The track and trackway record appears to be best in the Late Jurassic. To cite this article: C.A. Meyer, B. Thüring, C. R. Palevol 2 (2003) 103–117.     

Pisanosaurus mertii and the Triassic ornithischian crisis: could phylogeny offer a solution?

Abstract

Two recent studies have independently recovered Pisanosaurus mertii – long thought to represent the oldest known member of Ornithischia – within Silesauridae. These finds are expanded upon here, as are the implications of this hypothesis. Based upon these finds, it now appears that Ornithischia was absent in the Triassic Period entirely, which constitutes a major incongruence between the fossil record and current phylogenetic hypotheses, particularly the traditional model of dinosaur interrelationships in which Ornithischia and Saurischia are sister-taxa. It has been suggested previously that Ornithischia was simply a rare component of Late Triassic faunas, or that perhaps the clade’s ecology or geographic distribution were not conducive to producing a fossil record. Here I propose that phylogeny could hold the solution to this problem. I examine how an alternative position for Ornithischia – nested either within Theropoda or Sauropodomorpha – could be the reason behind their later appearance and relative rarity in the Early Jurassic. An Early Jurassic origin of Ornithischia would force us to consider that the anatomical similarities between ornithischians and Early Jurassic taxa might not be convergences, and to broaden the current datasets of early dinosaurs to test these ideas.     

Tetrapod Footprint Biostratigraphy and Biochronology

Tetrapod footprints have a fossil record in rocks of Devonian-Neogene age. Three principal factors limit their use in biostratigraphy and biochronology (palichnostratigraphy): invalid ichnotaxa based on extramorphological variants, slow apparent evolutionary turnover rates and facies restrictions. The ichnotaxonomy of tetrapod footprints has generally been oversplit, largely due to a failure to appreciate extramorphological variation. Thus, many tetrapod footprint ichnogenera and most ichnospecies are useless phantom taxa that confound biostratigraphic correlation and biochronological subdivision. Tracks rarely allow identification of a genus or species known from the body fossil record. Indeed, almost all tetrapod footprint ichnogenera are equivalent to a family or a higher taxon (order, superorder, etc.) based on body fossils. This means that ichnogenera necessarily have much longer temporal ranges and therefore slower apparent evolutionary turnover rates than do body fossil genera. Because of this, footprints cannot provide as refined a subdivision of geological time as do body fossils. The tetrapod footprint record is much more facies controlled than the tetrapod body fossil record. The relatively narrow facies window for track preservation, and the fact that tracks are almost never transported, redeposited or reworked, limits the facies that can be correlated with any track-based biostratigraphy.

A Devonian-Neogene global biochronology based on tetrapod footprints generally resolves geologic time about 20 to 50 percent as well as does the tetrapod body fossil record. The following globally recognizable time intervals can be based on the track record: (1) Late Devonian; (2) Mississippian; (3) Early-Middle Pennsylvanian; (4) Late Pennsylvanian; (5) Early Permian; (6) Late Permian; (7) Early-Middle Triassic; (8) late Middle Triassic; (9) Late Triassic; (10) Early Jurassic; (11) Middle-Late Jurassic; (12) Early Cretaceous; (13) Late Cretaceous; (14) Paleogene; (15) Neogene. Tetrapod footprints are most valuable in establishing biostratigraphic datum points, and this is their primary value to understanding the stratigraphic (temporal) dimension of tetrapod evolution.     

Sauropod tracks from the Middle Jurassic Chuanjie Formation of Yunnan Province and the pre-Cretaceous sauropodomorph trackways from China

The Xixipo dinosaur tracksite in the Chuanjie Formation of Yunnan Province is one of the 14 Chinese sites yielding sauropod tracks from between the Triassic–Jurassic and Jurassic–Cretaceous boundaries, but is only one of the two that represent the Middle Jurassic. Although it is a small site, it adds incrementally to the overall track record of the region and allows comparison with the body fossil record and classification of the Chuanjie Formation as a Type 3b or Type 4b deposit in which both the body fossil and trace fossil record, in this case representing sauropodomorphs, are similar in composition and frequency of occurrence. We argue that the sauropod trace and body fossil records, while based on different categories of evidence, are very important. Integrating and correlating all available data from both records increases our understanding of sauropod communities, and both are equally valuable for this. In addition, we also discuss narrow to wide gauge, coeval sauropod trackways from China, and the relationship between the potential trackmaker of China's Jurassic Brontopodus-type trackways and mamenchisaurids and, beginning from the Late Jurassic, representatives of this type and titanosauriform sauropods.