First report of Silurian crinoid columnals with tetralobate and hexalobate lumen structures

Thomka, James R.; Motz, Gary J.

doi:10.1080/11035897.2013.854271

Cited by 3 publications

(2 citation statements)

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“…Influences on echinoderm palaeoecology, pelamtozoan encrustation of micro-bioherms. (Halleck 1973;Brett 1981Brett , 1984, trilobate lumen-bearing holdfasts are associated with the common hemicosmitid rhombiferan Caryocrinites (Brett 1978(Brett , 1984, and tetralobate lumenbearing holdfasts cannot be definitively associated with a specific pelmatozoan taxon (Thomka & Motz 2014). The density of encrustation by pelmatozoans ( Figs 4C, 7A, B) clearly indicates that micro-bioherms represented favourable substrata.…”

Section: Palaeontological Effectsmentioning

confidence: 96%

“…Micro‐bioherm exteriors are densely encrusted by dendritic radix structures (sensu Brett ; Figs C, A, B) characterized by lumina with trilobate, tetralobate and pentalobate configurations. Pentalobate lumen‐bearing holdfasts are associated with the common monobathrid crinoid Eucalyptocrinites (Halleck ; Brett , ), trilobate lumen‐bearing holdfasts are associated with the common hemicosmitid rhombiferan Caryocrinites (Brett , ), and tetralobate lumen‐bearing holdfasts cannot be definitively associated with a specific pelmatozoan taxon (Thomka & Motz ).…”

Section: Palaeontological Effectsmentioning

confidence: 99%

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Palaeontological and sedimentological effects of micro-bioherms in the Middle Silurian Massie Formation of southeastern Indiana, USA

Thomka

Brett

2015

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Small build‐ups composed primarily of micrite and benthic skeletal remains, termed ‘micro‐bioherms’, have been recognized within Silurian strata of eastern and midcontinental United States for well over 75 years; however, previous research has focused nearly entirely on such structures within the upper Wenlock (Homerian) Waldron Shale. An undolomitized section of the lower Wenlock (Sheinwoodian) Massie Formation in Ripley County, southeastern Indiana, was studied to assess the influence of micro‐bioherms on palaeoecological, taphonomical and sedimentological patterns. Increased baffling of fine‐grained material by organisms composing and/or encrusting build‐ups is evidenced by muddy sediment containing pascichnial traces surrounding micro‐bioherms. Pelmatozoan attachment structures densely encrust micro‐bioherms, but are swollen by secondary stereomic overgrowths reflecting some form of antagonistic interaction or investment in strong affixation to elevated substrates. Clusters of bumastine trilobite material occur in ‘pockets’ related to cavities within build‐ups, and otherwise rare spathacalymenid trilobites, often exceptionally preserved, are found in muds in the vicinity of partially buried micro‐bioherms. Coeval sections nearby are nearly unfossiliferous as result of dolomitization, but contain recognizable skeletal material in greatest abundance in micro‐bioherm flank beds. The occurrence of these bodies within the Massie Formation is genetically linked to a major transgressive episode, but also reflects a mid‐Silurian climatic/palaeoceanographic change.

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Section: Palaeontological Effectsmentioning

confidence: 96%