Late Devonian rugose corals and the Frasnian–Famennian crsis

Abstract

All well-dated occurrences of Upper Devonian septate corals (subclass Rugosa) are analyzed at species and higher taxonomic levels. Platform-dwelling corals are differentiated from the less numerous basin-dwelling corals.Through early and middle Frasnian time, evolution outpaced the extinction of rugose corals, so that late Frasnian faunas were more diverse than the earliest Frasnian faunas. This gradual increase of genera was terminated abruptly by an almost complete extinction of late Frasnian platform-dwelling Rugosa in uppermost gigas to lower Palmatolepis triangularis Zone time. None of the 151 species, and probably as few as two or three, at most five, of the 47 genera of late Frasnian shallow-water corals survived this event. The loss of coral biomass was equally devasting. Very few early Famennian platform-dwelling corals are known, although platform carbonates of this age were deposited in several regions. Platform faunas, comprising 66 species and 27 genera, reappeared in late Famennian time. These faunas were unrelated phylogenetically to known Frasnian faunas but were forerunners of shallow-water Carboniferous faunas.Basin-dwelling Rugosa were affected little by the late Frasnian extinction event: all 12 Frasnian genera survived it.Rugose coral data provide compelling evidence for a major late Frasnian extinction of shallow-marine benthos without suggesting a unique cause of it. The data are consistent with results expected of an asteroid impact or a rapid decline of ocean temperature, especially in regard to the very much higher survival rate among basin-dwelling corals. However, the data are not controlled by a sufficiently refined time scale to prove the geological instantaneity of such an event.

Potyphyllum, a new phillipsastreid genus of rugose corals in the Upper Frasnian of Belgium with precisions about the age of the Petit-Mont Member

“…The genus Potyphyllum is introduced herein for massive pseudocerioid rugose corals akin to Phillipsastrea which have been informally assigned to "Pseudoacervularia" by Rohart & Semenoff-Tian-Chansky (1981, pp. 12, 18), Sorauf & Pedder (1986, p. 1286 and McLean (1989, p. 240). It corresponds to the Phillipsastrea ananas species group of Wrzołek (2011, p. 193) and to Pseudoacervularia Schlüter, 1881 sensu Różkowska (1953, p. 49).…”

Conodonta, Trilobita, and Anthozoa near the Late Frasnian Upper Kellwasser Event of the Geipel Quarry section in Schleiz, Thuringian Mountains (Germany)

“…11, Palmatolepis bogartensis (Stauffer, 1938) Hill 1938: 5-12) remained nearly unknown in the Frasnian (and also in the Givetian). Therefore, Sorauf & Pedder (1986: 1267 speculated about a possible late origin of basinal faunas in the Famennian, but they existed throughout all the Devonian (and Silurian), and were described only exceptionally by very few authors, often of ancient times without modern morphological revisions. The first thorough record for the Early Frasnian (including now late Givetian Pharciceras beds) in ammonoid facies was given, already in the period before use of thin sections, by Ludwig (1865-1866: 9 nearly forgotten, never redescribed coral taxa from the Rhenish Mountains).…”

Palaeoecology of a post‐extinction reef: Famennian (Late Devonian) of the Canning Basin, north‐western Australia

“…This radiation was abruptly curtailed coincident with the F/F boundary: of the 43 Frasnian rugosan genera, only 14 are known from the Famennian. The crisis appears to have had a differential effect on rugosan species, removing nearly all shallow-water but only a few solitary, deep-water forms (Sorauf and Pedder 1986). These rugosans subsequently diversified in the Famennian, mainly from deep-water Frasnian species that invaded vacated shallow environments; colonial taxa had re-appeared by the late Famennian (Pedder 1982) and likewise, Heterocorallia flourished in the Famennian (Scrutton 1998).…”