A basal thunnosaurian from Iraq reveals disparate phylogenetic origins for Cretaceous ichthyosaurs

Cretaceous ichthyosaurs have typically been considered a small, homogeneous assemblage sharing a common Late Jurassic ancestor. Their low diversity and disparity have been interpreted as indicative of a decline leading to their Cenomanian extinction. We describe the first post-Triassic ichthyosaur from the Middle East, Malawania anachronus gen. et sp. nov. from the Early Cretaceous of Iraq, and re-evaluate the evolutionary history of parvipelvian ichthyosaurs via phylogenetic and cladogenesis rate analyses. Malawania represents a basal grade in thunnosaurian evolution that arose during a major Late Triassic radiation event and was previously thought to have gone extinct during the Early Jurassic. Its pectoral morphology appears surprisingly archaic, retaining a forefin architecture similar to that of its Early Jurassic relatives. After the initial latest Triassic radiation of early thunnosaurians, two subsequent large radiations produced lineages with Cretaceous representatives, but the radiation events themselves are pre-Cretaceous. Cretaceous ichthyosaurs therefore include distantly related lineages, with contrasting evolutionary histories, and appear more diverse and disparate than previously supposed.     

New beetles (Insecta,Coleoptera) from the Lower Triassic of European Russia

Fossil remains of beetles are described from two Lower Triassic localities: Entala (Induan) and Tikhvinskoe (Olenekian). Only one beetle fossil was previously known from the Lower Triassic of Tikhvinskoe. The fossils are rather few and poorly preserved, but they are worth describing as finds rare for the Lower Triassic. Five fossils from Entala most probably belong to beetles of the same species of the formal genus Pseudochrysomelites. Beetles of this genus are especially abundant in deposits close to the Permian–Triassic boundary and can be considered “disaster taxa.” There are no known cases, either in the Permian or in the Middle–Upper Triassic, of a random sample of five specimens belonging to a single species. This suggests that in the Entala oryctocenosis the species diversity of beetles is extremely low. All three beetle fossils found in Tikhvinskoe belong to beetles of different species, showing that diversity had already started to increase. However, it remained low, and all fossils belong to the formal family Schizocoleidae, and two of the three belong to the same genus, Pseudochrysomelites. The Khei-Yaga locality, which immediately follows Tikhvinskoe in time (topmost Olenekian or early Anisian), already contains beetles of the families Asiocoleidae and Permosynidae. In the Lower Anisian of the Buntsandstein, such typical Mesozoic beetles as Cupedidae and Coptoclavidae have been recorded. The appearance of such advanced beetles as early as the Lower Anisian suggests that the famous Permian–Triassic crisis was not as deep as it is usually believed, and many beetles survived it, disappearing, however, from the fossil record in the Early Triassic.     

New thylacocephalans from the Early Triassic Paris Biota (Bear Lake County,Idaho, USA)

Two new genera and species of thylacocephalans (Arthropoda, Thylacocephala), Parisicaris triassica Charbonnier and Ligulacaris parisiana Charbonnier, are described from the early Spathian Paris Biota. These new occurrences are the first reports of thylacocephalans from Triassic rocks in North America. They considerably enlarge the spatiotemporal distribution of these enigmatic arthropods and highlight their relatively high generic richness during the Early Triassic. It also confirms that the Triassic was the taxonomically richest period for Thylacocephala.     

Devonian (Eifelian) disparid crinoids from the Zeravashan range,southern Tien Shan,Uzbekistan

No Devonian disparid crinoids have been described from Uzbekistan, although parahexacrinid thecae and assorted columnals have been described in several papers in the past 50 years. Discovery of a cup of Pisocrinus and a thecae of Haplocrinites are the first of these genera known from Uzbekistan. The stratigraphic range of Haplocrinites is revised to be late Early Devonian (Emsian) to Early Carboniferous (Tournaisian) because Silurian species assigned to the genus are based on loose ossicles that morphologically do not belong to the genus. The paleogeographic ranges of Pisocrinus and Haplocrinites are extended into Uzbekistan. Haplocrinites uzbekistanensis n. sp. is described.     

Late Triassic dinosaur teeth from southern Belgium

Isolated Dinosaur teeth have been discovered in the Upper Triassic locality of Habay-la-Vieille, in southern Belgium. Ornithischia are represented by three dental morphotypes; two of them closely resemble isolated teeth from the Middle or Upper Jurassic of Portugal and England. The presence of sauropods in the Upper Triassic of Europe is confirmed. Sauropods already had a wide geographical distribution during the Latest Triassic, as fossils have been discovered in South Africa, Thailand and western Europe. At Habay-la-Vieille, sauropods and prosauropods co-existed at the end of the Triassic. Two dental morphotypes may tentatively be referred to as theropod dinosaurs. The study of isolated teeth indicates that dinosaurs were already well diversified in the Latest Triassic of western Europe. To cite this article: P. Godefroit, F. Knoll, C. R. Palevol 2 (2003) 3–11.     

A late-surviving Triassic protomonaxonid sponge from the Paris Biota (Bear Lake County,Idaho, USA)

Protomonaxonid sponges are a major group of Cambrian and Ordovician fossils in exceptionally preserved (especially Burgess Shale-type) faunas, but are rare thereafter. Rare examples of apparent surviving lineages are known from the late Palaeozoic and Mesozoic, but by this time more derived groups of sponges have generally displaced them in at least shallow-water (shelf depth) ecosystems. The early Spathian (Early Triassic) Paris Biota includes abundant material of a new leptomitid protomonaxonid, Pseudoleptomitus advenus Botting nov. gen., nov. sp., distinguished by having an unbundled longitudinal skeleton and very weak transverse component. This is the first post-Ordovician leptomitid known, and indicates long-term survival of the group in unknown environments. Its occurrence near storm wave base is similar to the preferred environment of earlier examples of the family, suggesting either ecological rarity or taphonomic reasons for their ∼200-million-year absence from later Palaeozoic rocks.     

NEW CLADID AND FLEXIBLE CRINOIDS FROM THE MISSISSIPPIAN (TOURNAISIAN, IVORIAN) OF ENGLAND AND WALES

Abstract:  The modern study of fossil crinoids began with J. S. Miller who, in 1821, described specimens from southern England, nearby Wales and other regions, and named several common Early Carboniferous genera. Later, in 1950–60, James Wright monographed all known Early Carboniferous crinoids from the British Isles. In spite of such previous scrutiny, we recognize here two new genera among species already described: Glamorganocrinus gen. nov. (type species: Ophiurocrinus gowerensis Wright, 1960) from South Wales and Mendipocrinus gen. nov. (type species: Poteriocrinus latifrons Austin and Austin, 1847) from southern England. These new genera increase the number of advanced cladid genera in the Ivorian Substage of the Tournaisian in western Europe to 18, and the total number of crinoid genera to 36. A review of species assigned to Mespilocrinus has led to the recognition of M. granulifer De Koninck and LeHon, 1854 as a nomen dubium. A new species of Mespilocrinus , M. wrighti sp. nov., is described from the Ivorian of South Wales; this is the most highly derived species of the genus, as based on a phylogenetic analysis including ten species and 13 characters, with Pycnosaccus as the outgroup. A single, well-ordered tree resulted from this analysis. Interpretation of this tree suggests that the centre of evolution for Mespilocrinus was North America, where three species appeared during the Kinderhookian (early Tournaisian), rapidly achieving morphological disparity within the genus. This radiation event was part of the overall explosive radiation of crinoids following the Late Devonian mass extinction event when crinoid diversity was at a global minimum during the Frasnian. Recovery began during the Famennian, followed by an explosive radiation in the Tournaisian.     

Parafurnishius,an Induan (Lower Triassic) conodont new genus from northeastern Sichuan Province,southwest China and its evolutionary implications

A fundamental aspect of taxonomy at the generic level, critical to understand Early Triassic conodont evolution, is the composition of the multielement apparatus. In this paper, we document a platform-bearing new conodont genus, Parafurnishius n. gen., as well as its multielement apparatus from the Griesbachian Feixianguan Formation (Lower Triassic) in Xuanhan County, northeastern Sichuan Province, southwest China. The new conodont genus is characterized by numerous robust and irregularly distributed conical denticles with variable platform morphology that has a possible affinity with the P₁ elements of Furnishius. These genera have apparatuses similar to those of Ellisonia and are classified with the family Ellisoniidae. The strong intraspecific variation of P₁ elements and the growth series within the entire sample population suggest that Parafurnishius may have evolved from the Griesbachian Isarcicella by developing random denticle positioning away from the platform centre, and then possibly evolved into younger Triassic Furnishius by developing a stable blade configuration. This preferred interpretation implies an ellisonid apparatus for Isarcicella. Alternatively, Parafurnishius may have evolved from Ellisonia and developed a homeomorphic P₁ element with Isarcicella. This new taxon has strong intraspecific variation of denticle growth orientation during the Early Triassic.     

Survival and recovery of calcareous foraminifera pursuant to the end-Permian mass extinction

Ninety-one percent of calcareous foraminiferal genera became extinct during the end-Permian mass extinction. The Early Triassic Epoch was a survival phase characterized by a short-lived proliferation of disaster forms and then a prolonged interval of low diversity. The orders Miliolida and Lagenida experienced limited taxonomic re-diversification in Early and Late Anisian time, respectively. All fusulinoidean fusulinides became extinct in Late Permian time, and only two non-fusulinoidean genera persisted into the Early Triassic. Triassic fusulinides diversified to just five genera before the order became entirely extinct in Late Triassic time. Involutinides originated in Olenekian time from an unknown ancestor. They did not significantly diversify until Late Triassic time. To cite this article: J.R. Groves, D. Altiner, C. R. Palevol 4 (2005).     

Paleobiology of the oldest known articulate crinoid

The evolutionary and ecological recovery of benthic marine invertebrate faunas from the devastating Permian-Triassic mass extinction is poorly understood. In particular. Paleozoic crinoids were decimated, creating an evolutionary bottleneck, so that Early Triassic (Scythian) and Anisian representatives of the genus Holocrinus may be considered the stem group for the monophyletic crinoid subclass Articulata, which includes all post-Paleozoic crinoids. Crinoid ossicles in limestones of the Scythian (Spathian) Virgin Limestone Member (Moenkopi Formation) of southern Nevada and southwestern Utah, identified as Holocrinus? smithi, respresent the oldest known Holocrinus. Limestone units of the virgin were deposited in nearshore and inner shelf environments of an arid epeiric seaway. Although these crinoids are generally completely disarticulated and occur commonly in storm-generated deposits. they are interpreted to have been deposited near their living sites in ‘disturbed neighborhood’ assemblages. Counts of ossicles in bulk samples indicate a relatively low number of individuals, suggesting that populations of H.? smithi occurred in scattered clumps or as isolated individuals. attached to hardgrounds or shell beds. Bivalves are the most common associates, and are commonly more numerous than the estimated number of crinoid individuals, although bivalve species richness is never greater than three. Virgin Limestone fossil assemblages probably represent the first redevelopment of relatively complex tiered epifiaunal communities in the Mesozoic. *Echinodermata, mass extinction, Early Triassic, paleoecology, Crinoida, Articulata.     

A new brittle star (Ophiuroidea: Ophiodermatina) from the Early Triassic Paris Biota (Bear Lake County,Idaho, USA)

Knowledge on the morphology of Early Triassic ophiuroids is very limited, in spite of the relatively high number of described species. This hampers attempts to use morphology-based phylogenetic analyses in order to explore the early diversification of the ophiuroid modern clades between the latest Paleozoic and the early Mesozoic. Here, a new ophiuroid from the Early Triassic of southern Idaho (USA) is described and assigned to the new taxon Shoshonura brayardi Thuy nov. gen., nov. sp. It is part of an exceptional Early Triassic faunal assemblage recently described as the Paris Biota. On account of the arm morphology and the shape of the arm spines and arm spine articulations, Shoshonura brayardi nov. gen., nov. sp. is considered a basal member of the suborder Ophiodermatina.     

New trepostome Bryozoa from the Early Triassic (Smithian/Spathian) of Nevada

Two new bryozoan species of the trepostome family Dyscritellidae,Dyscritellopsis thaynesianus n. sp. andDyscritellopsis montelloensis n. sp., are described from the Early Triassic (Smithian/Spathian) Thaynes Limestone, Nevada (USA). The bryozoan fauna documents the survival of Paleozoic lineages into the earliest Triassic on northern open shelves outside the tropics. The fauna holds paleobiogeo-graphic connections to the Early Triassic bryozoan faunas of Spitsbergen.      

Additional thylacocephalans (Arthropoda) from the Lower Triassic (upper Olenekian) Osawa Formation of the South Kitakami Belt,Northeast Japan

The Lower Triassic Osawa Formation in the South Kitakami Belt, Northeast Japan, consisting mostly of mudstone of shallow-marine environment, was deposited during the late Olenekian (ca. 250 Ma), and is an important unit through which to examine the biotic recovery process after the end-Permian mass extinction. The Osawa Formation is the only unit in Japan that yields thylacocephalans (Arthropoda). Three species belonging to three genera have been reported before: Ankitokazocaris bandoi, Kitakamicaris utatsuensis and Ostenocaris sp. In addition to the known species, some thylacocephalans, including one new genus and three new species, are described in the present paper: Ankitokazocaris tatensis n. sp., Concavicaris parva n. sp., Miyagicaris costata n. gen. n. sp. and Ostenocaris? sp. Although Thylacocephala have a rather long stratigraphic range (from Silurian to Cretaceous) and are known from a wide geographical region, there are only about thirty genera in this group. The Osawa thylacocephalan fauna comprises at least five genera, making it one of the most diverse in the world at the generic level. During the Triassic Period, the Thylacocephala diversified and spread widely throughout low-latitude regions.     

Recolonization of the Himerometra robustipinna (Himerometridae, Crinoidea) by macrosymbionts: an in situ experiment

It is generally considered that symbiotic organisms colonize their hosts during their early stages of development. The main goals of the present study were to assess whether post-settled (juvenile and adult) symbionts were able to colonize comatulid crinoids, and whether a hosts’ spatial distribution may influence the colonization pattern through a series of field recolonization experiments. Three series of experiments on recolonization of the comatulid crinoid Himerometra robustipinna were conducted in the Nhatrang Bay, South-China Sea, Vietnam. Ten species of macrosymbiont, 1 polychaetes, 1 gastropods, 1galatheids, 1 ophiurids, and 6 shrimps were found to be associated with H. robustipinna host in the controls and in the 3 experimental series. We found that symbionts rapidly colonized depopulated crinoids in all the experimental series. The prevalence was lower in the experimental series than in the controls butthe abundance, species richness were not significantly different. The presence of post-settled juveniles and adults in experimental series indicated migration from neighboring hosts. Dispersal strategies of symbionts varied: some of them such as the polychaete Paradyte crinoidicola, the gastropod Annulobalcis vinarius, and the galatheid Allogalathea elegans were rapid colonizers. The shrimps Periclimenes commensalis, Pontoniopsis comanthi, and ophiuroid Gymnolophus obscura demonstrated low colonization rate. The 1 and 2 experimental series showed that there was movement of symbionts in dense hosts’ aggregations or over short distances. Unexpectedly, the infestation characteristics of crinoids in the spatially isolated site (series 3) didn’t differ from that of crinoids from aggregations (series 1 and 2), which indicates that long distance (tens meters) migrations of crinoid symbionts also occurs.     

Tetrapod postural shift estimated from Permian and Triassic trackways

Abstract:  The end-Permian mass extinction, 252 million years (myr) ago, marks a major shift in the posture of tetrapods. Before the mass extinction, terrestrial tetrapods were sprawlers, walking with their limbs extended to the sides; after the event, most large tetrapods had adopted an erect posture with their limbs tucked under the body. This shift had been suspected from the study of skeletal fossils, but had been documented as a long process that occupied some 15–20 myr of the Triassic. This study reads posture directly from fossil tracks, using a clear criterion for sprawling vs erect posture. The track record is richer than the skeletal record, especially for the Early and Middle Triassic intervals, the critical 20 myr during which period the postural shift occurred. The shift to erect posture was completed within the 6 myr of the Early Triassic and affected both lineages of medium to large tetrapods of the time, the diapsids and synapsids.     

Palaeobiology of Triassic procolophonids,inferred from bone microstructure

Procolophonoidea represent the most successful radiation of Parareptilia that lived during the Permo-Triassic. They are one of the few vertebrate groups that survived the end-Permian extinction and are thus important for studying the recovery of the post-extinction terrestrial ecosystem. Here, we investigate the palaeobiology of three Triassic procolophonid parareptiles, namely Sauropareion anoplus, Procolophon trigoniceps and Teratophon spinigenis, from the Karoo Basin of South Africa, inferred from histological analyses of their limb bones. Results reveal that all three taxa exhibit parallel-fibered bone tissue. Growth rings are absent in the Early Triassic Sauropareion and Procolophon whereas annuli are present in the Middle Triassic Teratophon, even during early ontogeny, suggesting a difference in life histories. Morphology and bone histology imply fossorial lifestyles for all three taxa, suggesting that burrowing may have played an important role in their survival during the harsh post-extinction Triassic environment.     

Oldest scleractinian coral reefs on the North American craton: Upper Triassic (Carnian), northeastern British Columbia,Canada

Bioclastic accumulations composed of crinoids, brachiopods, molluscs, spongiomorphs and scleractinian corals occur within Upper Triassic strata of the lower Baldonnel Formation at Pardonet Hill in northeastern British Columbia Canada. These small buildups (∼100 to 500 m³) have planar bases and broadly convex tops. These mounds are interpreted as small patch reefs composed of packstone, bioclastic floatstone/rudstone and carbonate breccia intercalated with mixed siliciclastic carbonate sediments deposited in a shallow subtidal setting (i.e. above fairweather wave base). Amalgamated hummocky cross-stratified to current ripple-laminated, quartz-dominated sandstone beds and numerous sharp-based, normally graded bioclastic (commonly encrinitic) packstone/grainstone — quartz–sandstone couplets characterize inter-reef lithologies.Conodont biostratigraphy indicates that the Pardonet Hill patch reefs occur within strata dated as earliest Upper Carnian (lower nodosus zone). The Pardonet Hill patch reefs originated and developed during an interval of regional sea level lowstand. Strata within which these patch reefs occur represent the westernmost migration of the Triassic shoreline in western Canada. Disappearance of coral reefs in the study area may have been affected by rapid marine transgression and failure of reef faunas to recolonize the new shore zone further to the east.The Pardonet Hill locality occurred on the western margin of the North American craton during the Triassic. Prior to their discovery reef-like structures dominated by corals in the western Panthalassa were limited to allochthonous terranes (now part of the Cordillera). The Pardonet Hill patch reefs occur at approximately 30° Triassic paleolatitude. In modern settings, this is at the extreme latitudinal margin of subtropical zooxanthellate reef development. The presence of benthic faunas characteristic of low-paleolatitude settings on the northwestern coast of Pangea has significant implications in paleotectonic and paleoenvironmental reconstructions.     

Chondrichthyan teeth from the Early Triassic Paris Biota (Bear Lake County,Idaho, USA)

A new, diverse and complex Early Triassic assemblage was recently discovered west of the town of Paris, Idaho (Bear Lake County), USA. This assemblage has been coined the Paris Biota. Dated earliest Spathian (i.e., early late Olenekian), the Paris Biota provides further evidence that the biotic recovery from the end-Permian mass extinction was well underway ca. 1.3 million years after the event. This assemblage includes mainly invertebrates, but also vertebrate remains such as ichthyoliths (isolated skeletal remains of fishes). Here we describe first fossils of Chondrichthyes (cartilaginous fishes) from the Paris Biota. The material is composed of isolated teeth (mostly grinding teeth) preserved on two slabs and representing two distinct taxa. Due to incomplete preservation and morphological differences to known taxa, the chondrichthyans from the Paris Biota are provisionally kept in open nomenclature, as Hybodontiformes gen. et sp. indet. A and Hybodontiformes gen. et sp. indet. B, respectively. The present study adds a new occurrence to the chondrichthyan fossil record of the marine Early Triassic western USA Basin, from where other isolated teeth (Omanoselache, other Hybodontiformes) as well as fin spines of Nemacanthus (Neoselachii) and Pyknotylacanthus (Ctenachanthoidea) and denticles have been described previously.     

New species of Thylacocephala (Arthropoda) from the Spathian (Lower Triassic) of Chaohu,Anhui Province of China

We describe a new species of Thylacocephala, Ankitokazocaris chaohuensis sp. nov., from the Upper Spathian (Early Triassic) of Chaohu, Anhui Province, China. It is diagnosed by its unique outline of the carapace, small size, and the narrow and asymmetrical anterior notch. Fine preservation reveals at least 14 posterior appendages, traces of gills and raptorial appendages, and remains of trunk segments and muscles in Ankitokazocaris for the first time. This is the first report of Thylacocephala from the Early Triassic of China, confirming the wide distribution of this group in the Tethys. The new species is closer to the type species of Ankitokazocaris, which is stratigraphically somewhat older, than to a recently described almost coeval species from Japan.