Osteology of the Middle Triassic pseudosuchian archosaur Arizonasaurus babbitti

Arizonasaurus babbitti is rediagnosed from a well-preserved partial skeleton from the early Middle Triassic Moenkopi Formation of northern Arizona. The skull, excluding the braincase, is described and compared to other “rauisuchians” and basal archosaurs. Two possible autapomorphies include a deep fossa hidden from lateral and medial views on the posteroventral edge of the ascending process of the maxilla and a tongue (pubic peduncle of the ilium) and groove (proximal portion of the pubis) articulation between the pubis and the ilium.

The postcrania is described in detail. Tall neural spines form a sail that is similar to those of other basal archosaurs with unknown affinities (Ctenosauriscus, Lotosaurus, Bromsgroveia, “Hypselorhachis”). Additional characters in the pelvic girdle in Arizonasaurus unite this taxon with Ctenosauriscus, Lotosaurus, Bromsgroveia, and Hypselorhachus to form a group, the ctenosauriscids. Pelvic characters of the ctenosauriscids are also found in Poposaurus and “Chatterjeea”, suggesting that ctenosauriscids are closely related. A possibly monophyletic group containing Arizonasaurus, other ctenosauriscids, Poposaurus, Sillosuchus, and “Chatterjeea” the exclusions of most other rauisuchians is proposed based on a new understanding of pseudosuchian characters.     

Triassic temnospondyl biostratigraphy, biochronology and correlation of the German Buntsandstein and North American Moenkopi Formation

Based on temnospondyl distributions, we propose a correlation of the non-marine Lower and Middle Triassic strata of Germany and the western United States. This correlation relies principally on the presence of two genera, Nonesian (late Early Triassic) Parotosuchus and Perovkan (early Middle Triassic) Eocyclotosaurus . The distribution of Parotosuchus helgolandicus indicates that the Torrey Member of the Moenkopi Formation in Utah, USA is equivalent to the Volpriehausen Formation of the German Buntsandstein of Nonesian age. Magnetostratigraphy and the distribution of Eocyclotosaurus indicate that the Perovkan Holbrook Member of the Moenkopi Formation in Arizona corresponds to a short interval of Anisian time, as does the German Upper Buntsandstein. The Buntsandstein and Moenkopi biostratigraphic schemes agree with a recently proposed biochronology of Triassic terrestrial tetrapods.     

中国肯氏兽-山西鳄组合带的新发现之三:山西临县的主龙型类

近几十年,华北的二马营组上部地层以产出中国肯氏兽-山西鳄四足动物化石组合而闻名.最近在山西临县白道峪于上覆的铜川组一段发现了中国肯氏兽.本文描述了同一地点同一层位产出的主龙型类化石,包括一具山西鳄的部分骨架以及一些可以归入suchian的主龙类.它们是铜川组一段首次记述的主龙型类.最有鉴定特征的suchian材料包括一个大的髂骨以及一个小的、形状很奇特的、可能是跟骨的骨骼.髂骨可能可以归入一个奇异的波波龙类(poposauroid).因为中国肯氏兽与山西鳄同时出现在白道峪,表明中国肯氏兽-山西鳄组合可以向上延伸到铜川组一段.髂骨与跟骨大小悬殊,可能代表两个从未在中国肯氏兽-山西鳄组合报道过的物种.白道峪发现了特化的波波龙类,支持了波波龙类在中三叠世大量分化的观点.     

Considerations on the age of the Tiouaren Formation (Iullemmeden Basin,Niger, Africa): Implications for Gondwanan Mesozoic terrestrial vertebrate faunas

Pre-Aptian mid-Mesozoic terrestrial vertebrates from the African continent are still very poorly known. In Niger, the Tiouaren Formation in the Iullemmeden Basin has yielded dinosaur and other vertebrate remains, and this unit has been dated as Early Cretaceous, most probably pre-Aptian, on the basis of its fish fauna and geological relations to other units in the basin. A review of the fish fauna and invertebrates from this formation does not provide any evidence for such an age, and the geological relations only help to constrain the upper limit for the age of the formation (Aptian). In contrast, the described dinosaur taxa are phylogenetically nested with late Middle Jurassic to Early Late Jurassic taxa from other localities, and thus indicate a pre-Kimmeridgian, probably late Middle Jurassic age for the Tiouaren Formation. Under the assumption of such an age, the dinosaur fauna of this formation provides new insights into dinosaur faunal provincialism during the latest Middle Jurassic. Northern Gondwanan faunas of that time seem to have been different from southern Gondwanan faunas, and show closer affinities to Eurasian faunas than to the latter. A possible explanation for this might be a climatically controlled geographic barrier due to pronounced arid conditions and thus desert environments in central Gondwana during this time.     

Predator–prey interactions amongst Permo‐Triassic terrestrial vertebrates as a deterministic factor influencing faunal collapse and turnover

Unlike modern mammalian communities, terrestrial Paleozoic and Mesozoic vertebrate systems were characterized by carnivore faunas that were as diverse as their herbivore faunas. The comparatively narrow food base available to carnivores in these paleosystems raises the possibility that predator–prey interactions contributed to unstable ecosystems by driving populations to extinction. Here, we develop a model of predator–prey interactions based on diversity, abundance and body size patterns observed in the Permo‐Triassic vertebrate fossil record of the Karoo Basin, South Africa. Our simulations reflect empirical evidence that despite relatively high carnivore: herbivore species ratios, herbivore abundances were sufficient for carnivores to maintain required intake levels through most of the Karoo sequence. However, high mortality rates amongst herbivore populations, even accounting for birth rates of different‐sized species, are predicted for assemblages immediately preceding the end‐Guadalupian and end‐Permian mass extinctions, as well as in the Middle Triassic when archosaurs replaced therapsids as the dominant terrestrial fauna. These results suggest that high rates of herbivore mortality could have played an important role in biodiversity declines leading up to each of these turnover events. Such declines would have made the systems especially vulnerable to subsequent stochastic events and environmental perturbations, culminating in large‐scale extinctions.     

广西凤山、西林等地中三叠统上部双壳类分带研究*

讨论广西西部中三叠统上部的双壳类生物地层序列,建立5个化石带;并附述黔南和滇东南晚三叠世1个双壳类带.这些带自下而上为:(1) Daonella (Longidaonella) producta-D. americana 带,属晚安尼早中期;(2) D. moussoni 高峰带,属晚安尼晚期;(3) D. rieberi-D. indica 带,属早拉丁期;(4) D. kotoi-D. jilongensis 带,属晚拉丁早期;(5) Halobia subcomata-D. varifurcata带,属晚拉丁晚期;(6) H. rugosoides-H. bifurcata 带,属早卡尼期.文内简要描述了各带的主要标志化石23种.     

Late Triassic (Late Norian) gastropods from the Wallowa Terrane (Idaho,USA)

A diverse Late Triassic (Late Norian) gastropod fauna is described from the Mission Creek Limestone of the Wallowa terrane (Idaho, USA). Sample standardization by rarefaction analysis indicates that the fauna is even more diverse than the Late Triassic gastropod fauna from the Pucara Formation (Peru) which represents the most diverse gastropod fauna from South America. The gastropod fauna consists of 66 species; several genera are reported for the first time from North America. A high percentage of the species are highly ornamented and several have distinct siphonal canals. This suggests that the appearance of truly Mesozoic elements among the gastropods began before the Mesozoic Marine Revolution in other clades. The fauna is dominated by high-spired strongly ornamented procerithiids, a group more characteristic for the Jurassic. Comparison of the present fauna and the Iranian Nayband Formation gastropod fauna show that the procerithiids underwent a first global radiation in the Late Triassic. The high number of new species in this fauna suggests that sampling of Late Triassic gastropod faunas is still incomplete and hinders palaeobiogeographic considerations. Previous suggesions that gastropod faunas from the Wallowa and Wrangellia terranes resemble each other and are distinct from those of Alexander, Chulitna, and Farewell terranes are basically corroborated. The gastropod fauna of the Mission Creek Limestone differs considerably from that of the western and central Tethys but shares several taxa with the Late Triassic gastropod fauna of the Pucara Formation in Peru. Thus, the Hispanic corridor was probably not present in the Norian but opened only in the Early Jurassic. The subfamily Andangulariinae is introduced and placed in the Zygopleuridae. The generaSpiniomphalus, Nodoconus, Gudrunella, Blodgettella, Idahospira, andSiphonilda and the subgenusCryptaulax (Wallowax) are introduced. 27 species are erected. A lectotype is designated forCryptaulax rhabdocolpoides Haas, 1953.      

Taxonomical and palaeoecological investigations of the chondrichthyan and osteichthyan fish remains from the Middle-Late Triassic deposits of the Villány Hills (Southern Hungary)

Two sites in the Villány Hills, Hungary, have yielded rich fish assemblages from Middle to Late Triassic shallow marine deposits. The collected material comes from the Ladinian Templomhegy Dolomite Member and from the Carnian Mészhegy Sandstone Formation. The ichthyofauna is composed of both chondrichthyans (Hybodontidae indet., Palaeobates angustissimus, ‘Polyacrodus’ sp., ?Lissodus sp.) and osteichthyans (Gyrolepis sp., Birgeria sp., and further indeterminate actinopterygians). Despite the large sample size, no remains of neoselachians have been found. The Ladinian Templomhegy Dolomite is dominated by durophagous hybodontiforms (Palaeobates angustissimus, ?Lissodus sp.), but the piscivorous hybodontid and the generalist ‘Polyacrodus’ sp. are missing, while in the fish fauna collected from the Carnian Mészhegy Formation indeterminate piscivorous hybodontids are the most common elements and durophagous forms are much less abundant. The dominance of piscivorous hybodontids in the Carnian Mészhegy Sandstone could be related to the global decrease of diversity of marine fish-eating reptiles (e.g., nothosaurs) or to a change of paleoenvironmental conditions. The present study improves our knowledge on the poorly known Triassic vertebrate faunas of the Tisza Mega-unit, which formed a segment of the passive Neotethys margin of the European Plate and shows an important example of a potential vertebrate faunal shift during the Middle to Late Triassic.     

The Triassic fish faunas of the Cuyana Basin,Western Argentina

Abstract: The continental deposits of the Cuyana Basin, western Argentina, have yielded the most diverse, but so far almost unstudied, Triassic ichthyofaunas of South America. Here, we review these faunas and show that only eight of the 29 named taxa can be considered valid, including the chondrostean Neochallaia, the acrolepid Challaia, Guaymayenia, a taxon of uncertain affinities, and five species of the perleidiform family Pseudobeaconiidae. The first three taxa most probably come from Middle Triassic sediments, while the pseudobeaconiids are of Late Triassic age. Other material, although not diagnostic, probably represents other species, and thus, the diversity of actinopterygians in the Cuyana basin is certainly higher than currently recognized. For the Late Triassic fish fauna, the absence of crown‐group neopterygians and a single record of a sarcopterygian is noteworthy and probably indicates some degree of endemism in this fauna, also supported by the high abundance of pseudobeaconiids, which are unknown from other areas. Furthermore, on the basis of the age indicated by the fishes and the available geological information, we discuss the age of the local fauna of the Cerro Bayo, close to the city of Mendoza, and the Agua de la Zorra Formation, Uspallata.     

Palaeoecological significance of a new Griesbachian (Early Triassic) gastropod assemblage from Oman

A new Early Triassic (Griesbachian) gastropod fauna from the Al Jil Formation of Oman is described. Early Triassic faunas from elsewhere (e.g. the Italian Dolomites and the western USA) are typically of low diversity and high dominance, usually attributed to environmental stress in the immediate aftermath of the end-Permian mass extinction event. The new Oman fauna has, by contrast, relatively high diversity, low dominance and a more even spread of individuals between taxa. It is the most diverse Griesbachian fauna known to date. This is attributed to the favourable (i.e. well-oxygenated) conditions under which the fauna lived. This uncharacteristic Griesbachian gastropod fauna demonstrates that, in the absence of oceanic anoxia, biotic recovery after the end-Permian extinction event may occur surprisingly quickly (within one conodont zone). The fauna is also partially silicified, which has increased its preservation potential relative to other Griesbachian gastropod assemblages. However, only one reappearing Lazarus genus is present in the Oman fauna. This suggests that there was some other control on the abundance of Lazarus genera at this time, other than the absence of silicified faunas as previously suggested.     

FIRST RECORD OF A HETERODONT BIVALVE (MOLLUSCA) FROM THE EARLY TRIASSIC: PALAEOECOLOGICAL SIGNIFICANCE AND IMPLICATIONS FOR THE 'LAZARUS PROBLEM'

Abstract:  The heterodont bivalve Sinbadiella pygmaea gen. et sp. nov. is described from the Sinbad Limestone Member (Olenekian, Smithian) of the Lower Triassic Moenkopi Formation of Utah (USA). The new taxon is tentatively assigned to the Lucinidae on the grounds of its external morphology, larval shell morphology and hinge characters. It is the only definite representative of the Superorder Heterodonta in the Olenekian, removing this major clade of bivalves from the long list of Early Triassic Lazarus taxa. Although at least locally very abundant, the new taxon has been overlooked by earlier workers, probably due to its minute size. Dwarfism is a widespread phenomenon in Early Triassic faunas, which has been attributed to ongoing reduction of primary production. If S .  pygmaea was a lucinid, a chemosymbiotic feeding mode can be inferred, which might explain why it was able to thrive in conditions that suppressed filter feeding heterodonts.     

Biostratinomy and palaeoecology of the cassian formation (Triassic) of the Southern Alps

The sediments forming the Cassian Formation (Middle—Upper Triassic) of the Central Dolomites represent the following environments: back-reef areas, shallow marginal basins, slope, and central basin. In each of these major environments faunal assemblages were found whose composition, mode of preservation and occurrence proved to be characteristics. In the back-reef areas, algal/foraminifera- and calcareous sponge/coral-patch reefs with a highly diverse fauna of frame-builders and reef-dwellers, in some localities excellently preserved, form the most conspicuous feature. In the shallow marginal basins autochthonous algal meadow/soft-bottom associations dominated by gastropods and deposit-feeding bivalves prevail. Slope deposits do not contain any autochthonous associations but either remains of pelagic faunas or transported faunal elements of shallow-water origin in the form of Cipit boulders (subaerially cemented parts from the outer edge of the carbonate platforms), worn Pachycardia rugosa-dominated, or echinoderm debris-dominated assemblages. Sediments of the central basin lack benthic faunas but contains pelagic assemblages of low diversity dominated by Daonella, Posidonia, and some ammonites.     

Paleoanthropology of the Kibish Formation, southern Ethiopia: Introduction

Cranial and skeletal remains of modern humans, Homo sapiens, were discovered in the Kibish Formation in 1967 by a team from the Kenya National Museums directed by Richard Leakey. Omo I, from Kamoya's Hominid Site (KHS), consists of much of a skeleton, including most of the cranial vault, parts of the face and mandible, and many postcranial elements. Omo II, from Paul's Hominid Site (PHS), is a virtually complete calvaria. Only a limited fauna and a few stone artifacts attributed to the Middle Stone Age were recovered in conjunction with the fossil hominids. The available dating techniques suggested a very early age, over 100 ka, for Member I, from which the Omo I and Omo II fossils were recovered. However, in subsequent decades, the reliability of the dates and the provenance of the Kibish hominids were repeatedly questioned. The papers in this volume provide a detailed stratigraphic analysis of the Kibish Formation and a series of new radiometric dates that indicate an age of 196 +/- 2 ka for Member I and 104 +/- 1 for Member III, confirming the antiquity of the lower parts of the Kibish Formation and, in turn, the fossils from Member I. Studies of the postcranial remains of Omo I indicate an overall modern human morphology with a number of primitive features. Studies of an extensive lithic record from Members I and III indicate a Middle Stone Age technology comparable to assemblages of similar age elsewhere in Ethiopia. Studies of the mammalian, avian, and fish faunas indicate overall similarities to those found in the region today, with a few distinctive differences.     

Tetrapod association and palaeoenvironment of the Los Colorados Formation (Argentina): a significant sample from Western Gondwana at the end of the Triassic

The Los Colorados Formation constitutes a continuous continental succession deposited in Western Argentina during the Late Triassic, a time period that is crucial to the record of the faunistic turnover at the Triassic-Jurassic boundary. Many authors have pointed out that its rich tetrapod fauna represents a unique transitional assemblage with elements typical of both Late Triassic and Early Jurassic. However, the possibility that the fauna represented a mixture of Triassic and Jurassic horizons was also proposed. Recently, stratigraphic control of the fossiliferous levels was developed in order to correlate the different localities of the extense Los Colorados outcrops, and a revision of the taxonomic status of most tetrapods recovered is currently undergoing. Preliminary results confirm previous assumptions about the transitional nature of the assemblage where typical Triassic taxa are associated with dinosaur groups known from Early Jurassic levels in other Gondwanan areas. The fossiliferous levels of the upper third of the sequence included several basal archosaurs (aetosaurs, rauisuchids, sphenosuchians), protosuchian crocodiles, dinosaurs (sauropodomorphs, tetanuran theropods), derived therapsids and primitive chelonians. New evidence about tetrapod ichnites of chirotheroid affinities is added to the fossiliferous association.     

First 'Rauisuchian' archosaur (Pseudosuchia,Loricata) for the Middle Triassic Santacruzodon Assemblage Zone (Santa Maria Supersequence), Rio Grande do Sul State,Brazil

The ‘Rauisuchia’ are a group of Triassic pseudosuchian archosaurs that displayed a near worldwide distribution. In Brazil, their fossils are found only in the Santa Maria Formation (Paraná Basin) of the Rio Grande do Sul State, specifically in the Middle Triassic Dinodontosaurus assemblage zone (AZ) and the Late Triassic Hyperodapedon AZ (Rauisuchus tiradentes). Between these two cenozones is the Santacruzodon AZ (Middle Triassic), whose record was, until now, restricted to non-mammalian cynodonts and the proterochampsian Chanaresuchus bonapartei. Here we present the first occurrence of a rauisuchian archosaur for this cenozone, from the Schoenstatt outcrop, located near the city of Santa Cruz do Sul and propose a new species, based on biostratigraphical evidence and a comparative osteological analysis.     

Locomotor structures in the Middle Triassic archosaurs from Los Chañares (La Rioja,Argentina)

A brief anatomical analysis of the pedial adaptations of the archosaurs from Los Chañares is made based on new available data.

The archosaurs from the Los Chañares local fauna show four different patterns in the structure of their hind limbs: (1) crurotarsal asymmetrical (Chanaresuchus and Tropidosuchus) (2) crurotarsal symmetrical (Gracilisuchus) (3) mesotarsal asymmetrical (Lagerpeton) (4) mesotarsal symmetrical (Lagosuchus). Each group has typical features that define “grades”; or morphological sets that were present at the same time in the local fauna, showing more derived characters than previously expected from the Middle Triassic.     

桂西和黔南中三叠世珊瑚

文内描述中三叠世安尼阶(Anisian)珊瑚化石分别采自桂西田阳板纳组和黔南贵阳青岩青岩组。板纳组珊瑚群中建立Pentasmilia guangxiensisgen.etsp.nov.,该新属种有5条第一周期原生隔片甚至有5条第二周期后生隔片,以此不同于有6条第一周期原生隔片和有6条第二周期后生隔片的石珊瑚类(scleractinians)的珊瑚。产于板纳组的另一新属种Radiophyllia astylatusgen.etsp.nov.,其隔片的排列格式与前人归纳的隔片周期插入示意图甚似,但它却发生在中生代最早期(Anisian)珊瑚的骸体内。文中还对青岩组的Pamiroseris silesiaca作了重新描述。     

Biogeography of Triassic tetrapods: evidence for provincialism and driven sympatric cladogenesis in the early evolution of modern tetrapod lineages

Triassic tetrapods are of key importance in understanding their evolutionary history, because several tetrapod clades, including most of their modern lineages, first appeared or experienced their initial evolutionary radiation during this Period. In order to test previous palaeobiogeographical hypotheses of Triassic tetrapod faunas, tree reconciliation analyses (TRA) were performed with the aim of recovering biogeographical patterns based on phylogenetic signals provided by a composite tree of Middle and Late Triassic tetrapods. The TRA found significant evidence for the presence of different palaeobiogeographical patterns during the analysed time spans. First, a Pangaean distribution is observed during the Middle Triassic, in which several cosmopolitan tetrapod groups are found. During the early Late Triassic a strongly palaeolatitudinally influenced pattern is recovered, with some tetrapod lineages restricted to palaeolatitudinal belts. During the latest Triassic, Gondwanan territories were more closely related to each other than to Laurasian ones, with a distinct tetrapod fauna at low palaeolatitudes. Finally, more than 75 per cent of the cladogenetic events recorded in the tetrapod phylogeny occurred as sympatric splits or within-area vicariance, indicating that evolutionary processes at the regional level were the main drivers in the radiation of Middle and Late Triassic tetrapods and the early evolution of several modern tetrapod lineages.