Gary D. Webster

The Permian of Timor: stratigraphy, palaeontology and palaeogeography

The Permian of Timor in the Lesser Sunda Islands has attracted the attention of palaeontologists since the middle of the nineteenth century because of the richness, diversity and excellent state of preservation of its fauna. These abundant fossil data have been compiled and updated for the present account. The Permian rocks of Timor were deposited on the northern margin of Australia. At the present time the northern margin of Australia, in the region of Timor, is involved in a continent–arc collision, where Australia is colliding with the Banda Arcs. As a result of this collision, Permian rocks of the Australian margin have been disrupted by folding and faulting with the generation of mud-matrix melange, and uplifted to form part of the island of Timor. Due to this tectonic disruption, it has proved difficult to establish a reliable stratigraphy for the Permian units on Timor, especially as the classic fossil collections were obtained largely from the melange or purchased from the local people, and do not have adequate stratigraphic control. Detailed systematic, structural, stratigraphic and sedimentological studies since the 1960s have provided a firmer stratigraphic and palaeogeographic background for reconsideration of the significance of the classic fossil collections. Permian rocks on Timor belong either to a volcanic-carbonate sequence (Maubisse Formation), or to a clastic sequence (Atahoc and Cribas formations) in which volcanics are less prominent. The Permian sequences were deposited on Australian continental basement which was undergoing extension with spasmodic volcanic activity. Carbonates of the Maubisse Formation were deposited on horst blocks and volcanic edifices, while clastic sediments of the Atahoc and Cribas formations were deposited in grabens. The clastic sediments are predominantly fine-grained, derived from a distant siliciclastic source, and are interbedded with sediments derived from the volcanics and carbonates of adjacent horst blocks. Bottom conditions in the graben were often anoxic. In the present account, events on Timor during the Permian are related to the regional tectonic context, with the northward movement of Australia leading to the amelioration of the climate from sub-glacial to sub-tropical, together with the separation of crustal blocks from the northern Australian margin to form the Meso-Tethys.

Crinoids and stelleroids (Echinodermata) from the Broken Rib Member, Dyer Formation (Late Devonian, Famennian) of the White River Plateau, Colorado

A crinoid and stelleroid fauna is described from the Famennian (Late Devonian) Broken Rib Member of the Dyer Formation of the White River Plateau, Colorado. The fauna postdates the Late Devonian extinction event. Six new crinoid species described, including the new genus Tarassocrinus, are: Strimplecrinus dyerensis, Catactocrinus? torus, Hypselocrinus? bisonensis, Gilmocrinus? albus, Eireocrinus? coloradoensis, and Tarassocrinus synchlydus. The cladid-dominated crinoid fauna is transitional between earlier Devonian and later Carboniferous faunas. It contains the first report of Cupressocrinites (a Famennian Lazarus taxon) and Eireocrinus? in North America and extends ranges of several Carboniferous genera into the Late Devonian. A preliminary revision of the Rhenocrinidae is recommended. The family Glossocrinidae is recognized, and the Cupressocrinitidae are transferred to the Gasterocomacea. A new stelleroid genus and species, Pleiadeaster inceptus (Asteroidea; family unknown), and an ophiuroid, Ophiopolytretus aethus (Ophiuroidea; Lapworthuridae?) are named. In addition, Hudsonaster (Hudsonasteridae; Asteroidea) and two unassigned asteroids are present, and three further stelleroids cannot be assigned to the class level. Pleiadeaster and Hudsonaster are important because they suggest that the Late Devonian might have been a time of transition for asteroids. Ophiopolytretus aethus is an oegophiurid ophiuroid with distinctive respiratory? pores penetrating the disk plates.

Permian crinoids from the type-section of the Callytharra Formation, Callytharra Springs, Western Australia

An extremely diverse Permian crinoid fauna, one of the largest known from the Australian Palaeozoic, is described from the type section of the Callytharra Formation, west of Callytharra Springs, Western Australia. Forty species are recognized including 14 camerates, 25 inadunates, and 1 flexible. One new genus, Tapinocrinus, and three new species, T. macurdai, T. ingrami and Notiocatillocrinus callytharraensis are recorded. Recognition of Notiocatillocrinus and a dichocrinid in Western Australia establishes additional links with the eastern Australia Early Permian marine faunas. Eleven of the species are known to occur in the Permian of Timor. Recognition of these species suggests that the accepted age of the Callytharra Formation or, more likely, the Timor crinoid-bearing beds should be reconsidered.

A CLADID-DOMINATED EARLY MISSISSIPPIAN CRINOID AND CONODONT FAUNA FROM KERMAN PROVINCE, IRAN AND REVISION OF THE GLOSSOCRINIDS AND RHENOCRINIDS

Abstract A moderately diverse crinoid fauna from the Early Mississippian, Tournaisian, part of the Bahram Formation is reported from exposures in the vicinities of Hutk and Shams Abad, north of Kerman in southeastern Iran. Conodonts from the crinoid-bearing beds represent two faunas and indicate an age of Upper Siphonodella crenulata Biozone to Gnathodus typicus Biozone. Recognition of a Tournaisian age for this part of the Bahram Formation revises the previously assigned Famennian age and indicates that Famennian strata are much thinner, if present, in southeastern Iran. The fauna occurs in thin-bedded marls and limestones at the top of a shaley slope-forming sequence that grades upward into resistant cliff-forming limestones. Most crinoid specimens are crowns (many retaining part of the proximal stem) that have been flattened by compaction. At the genus level the crinoids include five camerates, three cladid dendrocrinids, ten other cladids, three flexibles, and one articulate. In addition, loose arm fragments and occasional cup fragments are common, along with abundant pluricolumnals and columnals in the fauna. Dominance of cladids over camerates probably reflects the argillaceous sediment in the mixed carbonate/siliciclastic platform environment of the fauna. This is the most diverse Tournaisian fauna reported from the northern margin of Gondwana and represents an equatorial fauna living at approximately 20°S latitude. Stronger affinities are with North American and European crinoid faunas than with Chinese and Australian faunas. Shallow-shelf conodonts from the crinoid-bearing beds are dominated by species of Polygnathus. Palaeoniscoid fish remains and shark teeth from the same beds support a shallow-shelf environment. New taxa proposed are Dichocrinus shamsensis new species; D. labyrinthus new species; Springeracrocrinus conicus new species; Atelestocrinus hutkensis new species; Zangucrinus abadensis new genus and species; Glossocrinacea new superfamily; Gelasinocrinus revimentus new genus and species; Amabilicrinidae new family; Amabilicrinus iranensis new genus and species, A. bahramensis new species; Derorhethocrinus elongatus new genus and species; Corematocrinidae new family; Lorocrinus zanguensis new genus and species; Blothrocrinus yazdii new species; Culmicrinus cylindratus new species; Paracosmetocrinus delicatus new species; Taxocrinus quadribrachiatus new species; Meristocrinus ovatus new species; and Hutkocrinus kermanensis new genus and species. Revision of the Glossocrinidae also resulted in designation of two new genera not present in the Iranian fauna: Bufalocrinus new genus (type species Catactocrinus? torus Webster and Hafley, 1999, from the Late Devonian, Famennian, of Colorado) and Nudalocrinus new genus (type species Culmicrinus jeffersonensis Laudon and Severson, 1953, from the Tournaisian of Montana).

BIOSTRATIGRAPHY, PALEOECOLOGY, AND TAXONOMY OF DEVONIAN (EMSIAN AND FAMENNIAN) CRINOIDS FROM SOUTHEASTERN MOROCCO

Abstract An early late Emsian codiacrinid and Frasnian specimens of an indeterminate species of Parapisocrinus, an undesignated new genus of a catillocrinid, and two amabilicrinids are described from the eastern part of the Anti-Atlas Mountains of Morocco. These are the first articulated crinoid specimens reported from the Famennian of Morocco. Specimens occur within ammonoid-rich dysoxic shales, marls, and thin limestones at Ouidane Chebbi, Jebel Mrakib, Lambidia, and Rich Bou Kourazia. Parapisocrinus, the codiacrinid, and the catillocrinid are loose cups that are associated with other megafossils and may have been transported within the pelagic depositional settings. The amabilicrinids occur in three small unitaxial lenses, two of which have associated logs. The problems with and possibility of a pseudoplanktic lifestyle for stemmed crinoids are discussed. These new collections expand the known stratigraphic and geographic distribution of the pisocrinid and amabilicrinids and the early evolutionary history of the catillocrinids. New taxa introduced are the amabilicrinids Mrakibocrinus bockwinkeli, Moroccocrinus ebbighauseni, and the codiacrinid Elicrinus? weyeri.

LATE DEVONIAN AND EARLY MISSISSIPPIAN ECHINODERMS FROM CENTRAL AND NORTHERN IRAN

Abstract New Devonian (Frasnian and Famennian) crinoids are described from central and eastern Iran and a new Mississippian (late Tournaisian) echinoderm fauna is described from the south flank of the Alborz Mountains of northern Iran. Both the Devonian and Mississippian echinoderms were living in a carbonate shelf basin on the northern flank of Gondwana at approximately 30° south latitude. The geographic ranges of Hexacrinites and Eutaxocrinus are extended onto the northern margin of Gondwana and add to the sparsely known Famennian crinoids. The Mississippian fauna is dominated numerically and in diversity by cladids, unlike most late Tournaisian faunas that are dominated by camerates in numbers, if not diversity. The late Tournaisian fauna is most similar to a coeval fauna from southern Iran, both of which have a noted lack of actinocrinitids and rare platycrinitids. It also shows similarity with Tournaisian faunas of western North America with four common genera. New species introduced are: Hexacrinites persiaensis, Eutaxocrinus risehensis, Dichocrinus damghanensis, Amabilicrinus stellatus, Bridgerocrinus alborzensis, Bridgerocrinus semnanensis, Paracosmetocrinus mobarakensis, Decadocrinus clypeus, and Palaechinus iranensis.

A re-evaluation of Famennian echinoderm diversity: implications for patterns of extinction and rebound in the Late Devonian

Abstract Critical to understanding long-term trends in diversity is a dataset that is both worldwide in scope and based on a sound taxonomic foundation. In this paper we re-evaluate the Famennian (Late Devonian) echinoderm dataset, which has changed radically in the past decade, and reinterpret patterns of Late Devonian echinoderm extinction and rebound based on these new data. Historically, Famennian (Late Devonian) and earliest Carboniferous echinoderms have been poorly known on a global basis leading to interpretations of prolonged rebound from the Devonian extinction events. Recent discoveries of abundant and diverse Famennian echinoderm faunas from northwestern China, Colorado, Australia and Iran, together with re-examination of previously known echinoderm faunas from Germany and England, have altered drastically our understanding of the patterns of extinction and rebound of Famennian and earliest Carboniferous echinoderm communities. Overall, Famennian echinoderm diversity at the generic level is nearly five times greater than reported in the 2002 Sepkoski compilation, and familial level diversity is more than seven times greater than previously thought. Despite the increases in diversity, Famennian echinoderm faunas show a reduced diversity of camerate crinoids that typify both Middle Devonian and Lower Mississippian faunas and portend the rise of cladid crinoid diversity later in the Carboniferous. Individual Famennian faunas are numerically dominated by blastoids, which also portends trends seen at various times later in the Palaeozoic. In general, we are able to recognize the following trends. Rebound from the Late Devonian extinction events in echinoderms was more rapid than previously thought, but seems to be concentrated in Asia. Palaeogeographically Famennian echinoderms can be grouped into two broad regions: one includes China, Australia and Iran, all of which bordered the Palaeotethys; the other includes regions from Laurussia (Europe and North America) and northern Africa (Morocco).

Chapter 14 Palaeobiogeography of Ordovician echinoderms

Abstract The palaeobiogeographical distribution of the six major clades of Ordovician echinoderms (asterozoans, blastozoans, crinoids, echinozoans, edrioasteroids and stylophorans) is analysed based on a comprehensive and up-to-date database compiling 3701 occurrences (1938 species recorded from 331 localities) of both complete specimens and isolated ossicles. Although historically biased towards a limited number of regions (Europe, North America, Russia), the resulting dataset makes it possible to identify six main palaeobiogeographical provinces for Ordovician echinoderms: Laurentia, Baltica, West Gondwana, East Gondwana, Avalonia and Siberia. At a global scale, the high endemicity of echinoderms during the Early to Middle Ordovician coincides with the time of maximum dispersal of continental masses. Late Ordovician faunas tend to become more cosmopolitan, possibly as a consequence of changing palaeogeography and/or relatively higher sea-levels in the Sandbian–Katian interval. Regional biodiversity patterns of Ordovician echinoderms confirm that their major diversification during the Ordovician is not a single, universal evolutionary event, but rather results from the complex addition of contrasted local evolutionary trends.

Late Devonian echinoderms from the Hongguleleng Formation of northwestern China

Abstract The Late Devonian, Famennian, Hongguleleng Formation of northwestern China has yielded one of the most diverse echinoderm faunas known from China. New collections and re-evaluation of earlier collections results in recognition of new taxa, increases the known diversity, provides new morphological information on some of the previously reported taxa, and provides new information on the affinity of the Late Devonian echinoderms of the Hongguleleng Formation. New crinoid taxa introduced are Gnarycrinus lanei n. gen., n. sp., Anamesocrinus tieni n. sp., Histocrinus? chenae n. sp., Eumhacrinus tribrachiatus n. gen., n. sp., Sostronocrinus aberratus n. sp. and Labrocrinus granulatus n. gen., n. sp. One new species of blastoid, Hadroblastus liaoi, n. sp. is described. Previous reports listed 46 echinoderms from the Hongguleleng Formation, including 13 blastoids and 33 crinoids. An additional 11 crinoid species bring the total crinoids to 44 species assigned to 32 genera. Similarly, the one additional species of blastoid brings the totals to 14 species assigned to 12 genera. The new echinoderms described herein include the first report of a dimerocrinitid, amphoracrinid, allagacrinid, glossocrinid, histocrinid, cercidiocrinid, dactylocrinid and neoschismatid from the Devonian of northwestern China. Additional morphologic information is provided for three of the previously described taxa and a revision of species assigned to Grabauicrinus is proposed. The crinoids and blastoids suggest closer affinity with Mississippian faunas than with Devonian faunas, and with North American faunas than European faunas. Collectively the blastoid and crinoid faunas from the Hongguleleng indicate that rediversification happened rapidly after extinction in contrast to current suggestions of a long interval of lowered origination following these extinction events.

Paleogeographic significance of Early Permian crinoids and blastoids from Oman

Early Permian crinoids and blastoids from Oman show relationship with Late Paleozoic Tethyan faunas of Timor and Western Australia and support an Early Permian age for part of the Basleo fauna of Timor. The camerate crinoidPlatycrinites omanensis n. sp. and the blastoidsTimoroblastus andDeltoblastus are reported for the first time from Sakmarian strata of northeastern Oman, doubling the known Permian echinoderms from Oman. The blastoids suggest an offshore lower energy shelf environment of deposition.KurzfassungCrinoiden und Blastoideen aus dem Unter-Perm des Oman lassen deutliche Beziehungen zu jungpaläozoischen tethyalen Faunen von Timor und W-Australien erkennen. Diese Beobachtung scheint das unterpermische Alter eines Teils der Basleo-Fauna von Timor zu bestätigen.Platycrinites omanensis n. sp. (Crinoidea, Camerata) sowie die BlastoideenTimoroblastus undDeltoblastus werden erstmals aus Schichten des Sakmarium im NE-Oman beschrieben. Damit verdoppelt sich die bisherige Artenzahl der bekannten permischen Echinodermen des Oman. Die untersuchten Blastoideen lassen auf einen gering-energetischen Lebensraum im offenen Schelfbereich schließen.