Life mode of in situ Conularia in a Middle Devonian epibole

Abstract

Exceptionally abundant specimens of Conularia aff. desiderata Hall occur in multiple marine obrution deposits, in a single sixth-order parasequence composed of argillaceous and silty very fine sandstone, in the Otsego Member of the Mount Marion Formation (Middle Devonian, Givetian) in eastern New York State, USA. Associated fossils consist mostly of rhynchonelliform brachiopods but also include bivalve molluscs, orthoconic nautiloids, linguliform brachiopods and gastropods. Many of the brachiopods, bivalve molluscs and conulariids have been buried in situ. Conulariids buried in situ are oriented with their aperture facing obliquely upward and with their long axis inclined at up to 87 degree to bedding. Most specimens are solitary, but some occur in V-like pairs or in radial clusters consisting of three specimens, with the component specimens being about equally long or (less frequently) substantially different in length. The compacted apical end of Conularia buried in situ generally rests upon argillaceous sandstone. With one possible exception, none of the examined specimens terminates in a schott (apical wall), and internal schotts appear to be absent. The apical ends of specimens in V-like pairs and radial clusters show no direct evidence of interconnection of their periderms. The apical, middle or apertural region of some inclined specimens abuts or is in close lateral proximity to a recumbent conulariid or to one or more spiriferid brachiopods, some of which have been buried in their original life orientation. The azimuthal bearings of Conularia and nautiloid long axes and the directions in which conulariids open are nonrandom, with conulariids being preferentially aligned between 350 and 50 degree and with their apertural end facing north-east, and nautiloids being preferentially aligned between 30 and 70 degree. Otsego Member Conularia were erect or semi-erect, epifaunal or partially infaunal animals, the apical end of which rested upon very fine bottom sediment. The origin of V-like pairs and radial clusters remains enigmatic, but it is probable that production of schotts was not a regular feature of this animal's life history. Finally, conulariids and associated fauna were occasionally smothered by distal storm deposits, under the influence of relatively weak bottom currents.

An evolutionary comparative analysis of the medusozoan (Cnidaria) exoskeleton

“…This trend is preserved in the fossil record. For example, in the Ponta Grossa Formation (Devonian), Paraná Basin, Brazil, sedimentological, stratigraphical, and taphonomic evidence shows the influence of deep‐water currents upon the distribution of some conulariid species (Simões et al ., ; Rodrigues, Simões & Leme, ; Van Iten et al ., ). In these rocks, the simple (without septa or carina) and thin exoskeleton of Conularia quichua Ulrich, 1890, would have been transported and reworked prior to its final deposition (Rodrigues et al ., ; Leme et al ., ).…”

“…Normally, when preserved in situ in the Ponta Grossa Formation, its exoskeleton is three dimensional, completely inflated, with the aperture region turned upward, as in life. These fossils were preserved below fair‐weather wave base (Simões et al ., ; Rodrigues et al ., ; Van Iten et al ., ). By contrast, the exoskeleton of Eoconularia loculata (Wiman, 1895) (Silurian in Sweden) is robust, with strongly mineralized septa and an internally thick corner groove (Jerre, ).…”

Origin and early diversification of the phylum Cnidaria Verrill: major developments in the analysis of the taxon's Proterozoic–Cambrian history

“…; Van Iten et al . ), the preservation potential of conulariids varies along an onshore–offshore bathymetric gradient, with taphonomically enhanced preservation occurring in sedimentary successions deposited under low rates of sedimentation punctuated by abrupt burial at or below storm wave base. Hence, palaeontologists searching for conulariids should target those portions of transgressive systems tracts (Simões et al .…”

Padrões de diversificação de Bougainvilliidae no contexto evolutivo de Medusozoa (Cnidaria)

“…This trend is preserved in the fossil record. For example, in the Ponta Grossa Formation (Devonian), Paraná Basin, Brazil, sedimentological, stratigraphical and taphonomic evidences show the influence of deep water currents in the distribution of some conulariid species (Simões et al, 2000; Rodrigues Simões & Leme, 2003;Van Iten et al, 2013b). In these rocks, the simple (without septa or carina) and thin exoskeleton of Conularia quichua Ulrich, 1890, would have been transported and reworked prior to its final deposition (Rodrigues et al, 2003;Leme et al, 2004).…”

“…Normally, when preserved in situ in the Ponta Grossa Formation, its exoskeleton is three dimensional, completely inflated, with the aperture region turned upward, as in life position. These fossils were preserved below fair-weather wave base (Simões et al, 2000;Rodrigues et al, 2003;Van Iten et al, 2013b). In contrast, the exoskeleton of Eoconularia loculata (Wiman, 1895) (Silurian in Sweden) is robust, with strongly mineralized septa and internally thick corner groove (Jerre, 1994).…”