42-5 Siluro-Devonian Paleobiogeography of the Order Conulariida (Cnidaria, Medusozoa): the Rise of the Cosmopolitan Conularia-Paraconularia Global Fauna

Session: Paleozoic Events and Processes: Sedimentary Geology, Paleontology, and Geochemistry (Posters)

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During the End Ordovician Mass Extinction Event, the phylogenetic tree of the cnidarian order Conulariida (Ediacaran-Triassic) remained largely intact, with surviving genera collectively recolonizing the cratonic paleoenvironments inhabited by their Ordovician representatives. However, by early-mid Devonian times just two/three genera, Conularia/Tasmanoconularia and Paraconularia, co-dominated nearly all known conulariid faunas, though with Conularia/Tasmanoconularia becoming subordinate to Paraconularia and its nearest relatives following the Frasnian-Famennian Mass Extinction Event. During the Silurian Period, conulariids in at least eight Ordovician genera, namely Archaeoconularia, Conularia, Ctenoconularia, Eoconularia, Galliconularia, Metaconularia, Pseudoconularia, and Tasmanoconularia (= Holoconularia) reappeared in Baltica, Laurentia (cratonic North America plus Scotland), and Gondwana (Paraná Basin and New South Wales), inhabiting both near- and offshore, low-latitude carbonate and high-latitude siliciclastic bottom environments. Metaconularia heymani, which first appears in the lower Katian of cratonic North America (Missouri), is among the pioneering benthic invertebrates preserved in sparsely fossiliferous estuarine sediments (basal Mosalem Formation, Illinois and Iowa) deposited during the final stage of the global Hirnantian-Rhudannian transgression. Along with Archaeoconularia, Eoconularia, Galliconularia, and Pseudoconularia, Metaconularia has yet to be documented from Devonian and younger strata, and therefore these five genera may have gone extinct during the Silurian Period. Conularia/Tasmanoconularia- and/or Paraconularia-dominated faunas of the early-mid Devonian Period have been documented from western Europe, cratonic North America, South America, South Africa, Australia, and, possibly, China. Ctenoconularia (misidentified as Reticulaconularia) survived in the Paraná Basin, and Reticulaconularia, a close relative of Paraconularia, inhabited the widely separated areas of the Paraná Basin, present-day New Jersey and Québec (Gaspé Peninsula), and South China (Hunan Province). Together, Devonian conulariids ranged from tropical to south polar latitudes and from western to eastern Gondwana, inhabiting, again, both carbonate and siliciclastic bottom environments. At the level of genus, then, the well differentiated, low-latitude and south polar conulariid faunas of the mid-late Ordovician world were replaced within 30 million years by a less diverse, cosmopolitan global fauna that came to be dominated by Paraconularia and its nearest relatives, which genera constitute the longest-lived (Ediacaran-Triassic) and most widespread subclade in the history of the order. At the broadest scale, the evolutionary and paleobiogeographical histories of the order Conulariida reflect the closing of early Paleozoic oceans and the amalgamation of formerly independent terranes into the supercontinent of Pangea.

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