The skull of a large Lower Triassic ichthyosaur from Spitzbergen and its implications for the origin of the Ichthyosauria

An incomplete ichthyosaur skull from the Lower Triassic (Spathian) Sticky Keep Formation of Spitzbergen is one of the earliest ichthyosaurs known and by far the largest of the most basal ichthyosaurs. The specimen shows an extremely plesiomorphic cheek region of the skull and allows for the first time a confident reconstruction of the grundplan condition of the lower cheek region of ichthyosaurs. It unequivocally demonstrates the presence of a deep emargination of the lower cheek, which is bordered dorsally by the quadratojugal, squamosal and jugal, and therefore a plesiomorphic lack of contact between jugal and quadratojugal. The specimen also allows an evaluation of recent skull reconstructions of several Lower Triassic taxa which probably contain severe misinterpretations. The structure of the temporal and cheek region of the specimen can be most parsimoniously explained by the initial presence of a lower temporal fenestra. This provides important new evidence that the ancestry of ichthyosaurs might have lain within the Diapsida or their stem-group.     

Multina from the Late Triassic Luning Formation,Nevada

The discovery of the network trace fossil Multina isp. in the Luning Formation of central Nevada provides new insight into the depositional setting of the Shaly Limestone Member of the Luning Formation. The ichnofossils occur in tabular mudstone beds deposited on a shelf environment or open carbonate platform. Although Multina resembles Paleodictyon, as both share polygonal burrow nets and both frequently occur in deep-water habitats, Multina is less regular and has other morphological traits such as crossing burrow branches not seen in Paleodictyon or Protopaleodictyon.     

Ammonoid biostratigraphy of the Middle Triassic Latemar platform (Dolomites, Italy) and its correlation with Nevada and Canada

An extensive study of the ammonoid fauna occurring in the lagoonal facies of a Middle Triassic isolated carbonate platform (Latemar platform, Dolomites, Italy) has been undertaken, and ammonoids from selected coeval successions (Punta Zonia, Marmolada, Rio Sacuz) have been illustrated. Ammonoids from Latemar have been collected in 20 distinct horizons (storm deposits) within the ca. 500 m thick lagoonal succession of the platform, thus providing a biostratigraphy of a series which is unusually expanded for this time interval, close to the Anisian-Ladinian boundary. Contrary to general opinion, some ammonoids of the Latemar and other coeval carbonate platforms of the Dolomites (Marmolada, Cernera), in particular Aplococeras avisianum, Lecanites misanii, Celtites spp., and Paranevadites sp., are also present in nearby basinal series. The same taxa have been found in North American localities deposited at the opposite margin of Panthalassa. The homotaxis of these ammonoids in North America and Latemar allow to establish a global scale correlation between the Southern Alps and North America with the highest resolution to date possible. In the context of this study, Aplococeras transiens n. sp. and Esinoceras nerinae n. sp are established.     

A new species of Azendohsaurus (Diapsida: Archosauromorpha) from the Triassic Isalo Group of southwestern Madagascar: cranium and mandible

Abstract: Here, we describe a new species of Azendohsaurus from the Middle–Late Triassic of Madagascar, extending the geographical range of a taxon known otherwise only by a single species from Morocco. Although Azendohsaurus has consistently been regarded as an early dinosaur (based on various advanced dental and gnathic features resembling those characterizing certain dinosaur subgroups), the relatively complete skeletal material, now available from Madagascar, argues strongly against its dinosaurian affinities. Rather, the retention of numerous primitive cranial and postcranial features indicates a surprisingly early divergence of Azendohsaurus within Archosauromorpha and an unusual mosaic of characters in this taxon. Features considered diagnostic of Sauropodomorpha thus are inferred to occur homoplastically in at least one clade of nondinosaurian archosauromorphs, indicating a complex evolution and distribution of features traditionally thought to be derived within archosaurs. Azendohsaurus has teeth resembling those of both early sauropodomorph and ornithischian dinosaurs, yet also possesses numerous inarguable basal archosauromorph cranial and postcranial attributes. This highlights the risk of uncritically referring isolated, Middle–Late Triassic (or even later), ‘leaf‐shaped’ teeth with denticles to the Dinosauria. Similarly, the occurrence of such teeth in an early diverging archosauromorph indicates that specializations for herbivory originated more frequently within this clade than conventionally assumed. For example, Azendohsaurus and numerous basal sauropodomorph dinosaur taxa share an array of convergently acquired features associated with herbivory, including tooth denticles, expanded tooth crowns, a downturned dentary and the articular located at the ventral margin of the mandible. Some of these features (denticles, expanded crowns and the ventrally deflected articular) are even more widespread among archosauromorphs, including aetosaurs, silesaurs and ornithischian dinosaurs. A downturned dentary also occurs in Trilophosaurus, a taxon further marked by unique specializations for herbivory, including transversely lophate, tricuspid teeth. An array of features associated with herbivory also occurs in rhynchosaurs and certain crocodilians (e.g. Simosuchus). This distribution suggests that craniodental features associated with herbivory were much more pervasive across the archosauromorph clade than previously recognized, possibly evolving at least six to eight times independently.     

贵州兴义中三叠世拉丁期兴义动物群粪化石

粪化石是重要的遗迹化石,其内含物信息可为讨论生物行为、生理、相互关系、古环境等提供重要证据,进而对恢复和重建地质历史时期的生态系统等有重要意义。本文首次报道了贵州省兴义市泥麦古剖面中三叠世拉丁期兴义动物群化石层第35自然层的7种不同形态的粪化石。通过观察粪化石的内含物情况,发现其主要由贵州龙骨骼和鱼鳞组成,极少含有无脊椎动物碎片,表明粪化石来源于非壳食性的肉食性动物。依据粪化石的尺寸、缺少螺旋结构及相对较小的内含物碎片等信息,排除动物源是无脊椎动物、大型肉食性鱼类及大型鱼龙类的可能。结合兴义动物群下部化石组合海生爬行类实体化石的信息,进一步推断所研究粪化石的动物源应为非鱼龙的海生爬行动物,很可能是幻龙类、鸥龙类或海龙类。本文报道的7种形态的粪化石显示该下部化石层中的海生爬行动物之间至少存在1级营养等级的差异,这为恢复和重建中三叠世拉丁期海洋生态系统提供了重要依据。另外微生物的参与及泥质含量较高的厌氧环境使得该层的粪化石保存完好。     

贵州中三叠世预言鱼目(近鲱形类)一新属种:奇异盘县鱼(Panxianichthys imparilis gen.etsp.nov.)（英文）

预言鱼目是中生代海生近鲱形类的一个绝灭的支系。由于与弓鳍鱼目密切的亲缘关系,预言鱼目在研究近鲱形类的早期演化和生物地理学中具有重要意义。然而,早期预言鱼目的化石证据非常匮乏;直到最近,产于云南中三叠世罗平生物群的强壮鱼是该目中最古老的也是三叠纪唯一的成员。本文根据产于贵州西部中三叠世盘县动物群的两块保存良好的标本命名了预言鱼目一个新的属种,奇异盘县鱼(Panxianichthys imparilis gen.et sp.nov.)。盘县鱼的生存时代略晚于强壮鱼,但它比产于欧洲晚侏罗世和美洲早白垩世的预言鱼目其他成员要早很多。盘县鱼具有预言鱼目的共近裔性状,上颌骨上具有感觉管,但它保留了一些其他预言鱼目鱼类所不具有的原始特征。分支分析的研究结果表明盘县鱼是最原始的预言鱼目鱼类,为揭示预言鱼目的演化提供了新的信息。强壮鱼和盘县鱼的相继发现表明,预言鱼目的早期分异比我们之前想象的要快得多。     

The cranial anatomy of Chinese placodonts and the phylogeny of Placodontia (Diapsida: Sauropterygia)

Placodonts are Triassic marine reptiles that inhabited the eastern and western margins of the Tethys Ocean (modern South China and Europe/Middle East). Although the crania of European taxa are relatively well understood, those of Chinese taxa have not been extensively studied, and most of them have not been incorporated into a comprehensive phylogeny. Here we present the first reconstructions of all known Chinese placodont holotype skulls using micro‐computed tomographic (μCT) scanning and/or detailed anatomical study. We also present the first phylogenetic analyses that incorporate all placodont genera using a general diapsid matrix that includes postcranial characters, and a placodont‐only cranial matrix. Results vary between the matrices; however, both support a monophyletic Placodontia with eastern taxa interspaced throughout, indicating no major separation between the eastern and western Tethyan realms. Support is strong for a western Tethyan origin of Placodontia, although the highly nested Placochelyidae first appear in the upper Middle Triassic of the eastern Tethys. Thus, all placodont clades appear to have originated in a period of intense speciation during the Middle Triassic. © 2015 The Linnean Society of London     

陕西鄂尔多斯盆地中三叠统一离片椎类牙齿化石

陕西省鄂尔多斯盆地渭北油田中三叠统铜川组发现一枚牙齿化石。该枚牙齿具有如下特征:牙齿细长,外形呈圆锥形,齿冠基部横截面为圆形,齿冠整体较直,沿长轴稍微向后缘弯曲,齿冠表面无齿脊和锯齿分布,发育纵向延伸的沟槽状纹饰。通过与鳄型类、蛇颈龙类和离片椎类的牙齿比较,该标本可以归入离片椎类。这枚牙齿化石为这一类群在中三叠统铜川组的首次发现,代表了离片椎类在华北板块最晚的化石记录。     

记云南罗平三叠纪小型始鳍龙类—新属种

根据一保存基本完整的骨架建立了始鳍龙类的一新属、种——纤细滇美龙(Dianmeisaurus gracilis gen.et sp.nov.)。标本采自云南省罗平县中三叠统关岭组Ⅱ段,为体态细长的小型物种。新属种与同产于该地区的利齿滇东龙(Diandongosaurus acutidentatus Shang et al.,2011)和丁氏滇肿龙(Dianopachysaurus dingi Liu et al.,2011a)身体各部位比例和个体大小接近,头骨均具有吻部两侧不收缩、眼眶显著大于上颞孔的特征。但新种眼眶间距要明显小于上颞孔间距,下颌关节与枕髁位于同一水平位置,锁骨前外侧缘的锁骨前突粗大而厚实,尺骨近端明显宽于远端,有比后两种更多的荐前椎(三属种荐前椎数分别为41、38、39枚)。此外,与滇东龙相对比,新种眶前区短于眶后区,前额骨和后额骨不相交。同时,新种下颌联合短,夹板骨参与下颌联合构成。新种前颌和下颌前部齿虽然也为獠齿(犬齿状齿),但未呈显著增大。头后骨骼对比,虽然新种和滇东龙均具有标志性的锁骨前外侧突,但后者的锁骨前外侧突尖细。与滇肿龙相对比,新种尾前部尾肋细长且未见明显加宽肿胀、仅具一个骨化的远侧腕骨、距骨为圆形且不具有近端凹入。去除数据不全的清镇龙、广西龙和三桥龙后的鳍龙类分支系统学分析表明,滇美龙与滇东龙互为姊妹群,同时它们与贵州龙、马家山龙和滇肿龙一起构成了一仅由在中国发现的属种组成的单系类群。这一单系类群与幻龙类的亲缘关系近于它们与欧洲肿肋龙类(Dactylosaurus,Anarosaurus,Serpianosaurus和Neusticosaurus)的亲缘关系。三种小型始鳍龙类的发现,指示云南罗平地区在三叠纪安尼期中晚期时鳍龙类是一类有较高分异度的海生爬行动物。     

Dasycladalean algae distribution in ammonoid-bearing Middle Triassic platforms (Dolomites, Italy)

This paper gives an account of distribution of Dasycladales in ammonoid-bearing Middle Triassic carbonate platforms of the Dolomites. A ca. 600-m-thick section was investigated within the Latemar platform interior and Dasycladales from correlated ammonoid-bearing samples of the Marmolada platform were studied for comparison. At Latemar, the dense sampling allowed, with some confidence, the identification of the first occurrences of Diplopora nodosa and Gyroporella ladinica, and the last occurrences of D. annulatissima and D. comelicana. Their stratigraphic range was found to be in agreement with literature. Other first or last occurrences could not be reconciled with known distributions, and were considered as environmentally or palaeogeographically controlled. All four algal events occur within a narrow interval of two Illyrian (Upper Anisian) ammonoid subzones (avisianum and crassus subzones). This study demonstrates the biostratigraphic potential of Dasycladales in platform settings, and highlights the necessity of detailed stratigraphic studies to determine their distribution.     

Diversity and paleoenvironmental significance of Middle Triassic ostracods (Crustacea) from northern Thailand: Pha Kan Formation (Anisian,Lampang Group)

The Pha Kan Formation that crops out at the Phra That Muang Kham section, south of Lampang city, was measured and sampled for ostracod analysis. We here report the occurrence of 29 species distributed among 14 genera. Four new species are described: Triassocypris phakanella Forel nov. sp., Leviella lampangensis Forel nov. sp., Bektasia yawella Forel nov. sp. and Hungarella poli Chitnarin nov. sp. The present data represent the first detailed report of Middle Triassic (Anisian) ostracods from the Sukhothai terrane and the first insight into diversity dynamics following the end-Permian extinction in this area. The ostracod assemblages of the Phra That Muang Kham section are discussed and document an important shift from siliciclastic to carbonate conditions, from a protected to an open marine environment, followed by a slight regressive trend up-section associated with repeated salinity fluctuations. This fauna illustrates the post-crisis recovery during the Middle Triassic and some hypothesis are issued on the distribution pathways of several taxa.     

云南中三叠世(安尼期)预言鱼目(全骨鱼类:近鲱形类)一新属种

预言鱼目是近鲱形类的一个绝灭支系,被认为是弓鳍鱼目的姐妹群.预言鱼目化石过去主要发现于欧洲的中三叠世拉丁期和晚侏罗世地层以及新大陆的早白垩世地层.近年来,在云南和贵州的中三叠世安尼期地层中分别发现了一种预言鱼目鱼类化石(强壮鱼和盘县鱼),代表了该目在中国的首次发现.根据产于云南罗平中三叠世安尼期(～244 Ma)海相地层中的6块保存良好的鱼化石,命名了预言鱼目一个新的属种,三叠复兴鱼(Subortichthys triassicus gen.et sp.nov.).三叠复兴鱼是罗平生物群中发现的第二种预言鱼目鱼类,代表了预言鱼目最古老的化石记录之一,为研究该目的起源和早期分异提供了重要信息.复兴鱼无疑可以归入近鲱形类,因为它具有近鲱形类两个共近裔性状,续骨与下颌关节以及上颌骨后缘具有凹缺.分支分析结果表明,复兴鱼位于预言鱼目的基部,因为它具有该目的重要鉴定特征,上颌骨具有感觉管,但它不具有其他预言鱼目鱼类的进步特征.特别的是,复兴鱼具有一些独特的性状,如额外肩胛骨3或4对、第三眶下骨特别宽大并与前鳃盖骨前缘相接等.复兴鱼的发现表明预言鱼目鱼类在华南地区(三叠纪时期位于古特提斯洋的东部)的早期分异至少发生在中三叠世早期(安尼期).     

Middle Triassic radiolarians from the Southeastern Pamirs (Republic of Tajikistan)

Triassic radiolarians were studied from a limestone/chert succession of the Dzhangisu and Boztere formations, Southeastern Pamirs, Republic of Tajikistan. The middle part of the Dzhangisu Formation is characterized by a Late Anisian assemblage with Eptingium nakasekoi Kozur and Mostler, Archaeospongoprunum bispinosum Kozur and Mostler, A. mesotriassicum mesotriassicum Kozur and Mostler, Paroertlispongus multispinosus Kozur and Mostler, P. rarispinosus Kozur and Mostler and Hozmadia rotunda (Nakaseko and Nishimura) that belongs either to the upper part of the Tetraspinocyrtis laevis Zone or to the Spongosilicarmiger transitus Zone (Kozur, 2003). The lowermost part of the Boztere Formation is characterized by a Late Ladinian assemblage with Muelleritortis cochleata (Nakaseko and Nishimura), M. expansa (Kozur and Mostler), Spongoserrula rarauana Dumitrica that corresponds to the M. cochleata Zone. Pamirian localities have a transitional position between the Western Tethys (Alpine–Mediterranean region) and the Eastern Tethys–Pacific junction (Southern China and Thailand). The assemblages are Tethyan in affinity.     

A new species of basal rhynchosaur (Diapsida: Archosauromorpha) from the early Middle Triassic of South Africa,and the early evolution of Rhynchosauria

Rhynchosauria was an important clade of herbivorous archosauromorph reptiles during the Triassic, with a worldwide distribution. We describe a new genus and species of early rhynchosaur, E ohyosaurus wolvaardti gen. et sp. nov. , from the early Middle Triassic (early Anisian) Cynognathus Assemblage Zone (Subzone B) of the Karoo Supergroup, South Africa. Eohyosaurus wolvaardti is known from a single skull, and is recovered as the sister taxon of Rhynchosauridae in a new phylogenetic analysis. Cynognathus Subzone B has previously yielded the stratigraphically oldest well‐understood rhynchosaur species, Mesosuchus browni and Howesia browni. Eohyosaurus wolvaardti increases the rhynchosaur diversity within this stratigraphical horizon to three species. Intriguingly, all currently confirmed rhynchosaur occurrences from the Early Triassic to earliest Middle Triassic are from South Africa. This may suggest a relatively restricted palaeogeographical distribution for early rhynchosaurs, followed by a global dispersal of rhynchosaurids during the Middle Triassic. © 2015 The Linnean Society of London     

A new species of Leptocycas(Zamiaceae)from the Upper Triassic sediments of Liaoning Province,China

A new cycad,Leptocycas yangcaogouensis sp.nov.,was found in sediments from the Late Triassic in western Liaoning,China.The pinnately compound leaves(Pseudoctenis type)are screwed in a crown on the stem top.The leaflets are linear,with parallel veins and decurrent bases on the rachis.The leaf bases are persistent.The cataphylls intermix with the leaves.The female cone is ovoid in shape.The characteristics of the new plant are more similar to those of Leptocycas gracilis,a Triassic cycad from North America,but the new species differs from L.gracilis in the size of its stem(7-8 vs.3-5 cm in diameter,respectively),leaves(length × width 100 × 16 vs.30 × 7 cm,respectively)and leaf density along the stem(4-6 vs.1-2 bases/1 cm length,respectively).Both L.gracilis and L.yangcaogouensis,having leaves of the Pseudoctenis type,show a closer relationship to the extant Dioon of Zamiaceae.The present study provides evidence for the origin of the genus Dioon,which may have come from Leptocycas plants of the Triassic.It would be assumed that the extent cycads in Zamiaceae originate from the pteridosperms in the Late Paleozoic and have evolved through the stage of L.gracilis and L.yangcaogouensis in Late Triassic,and reaching the extant Dioon.