Lower Famennian (Upper Devonian) rhynchonellide and athyride brachiopods from the South Armenian Block

Abstract

The lower Famennian ‘Cyrtospirifer’ orbelianus brachiopod Zone established in Armenia by Abrahamyan (1957) (coeval to the crepida conodont Zone) contains an abundant and diverse brachiopod fauna that still remains poorly studied. In an effort to revise and update its systematic classification and to assess the brachiopod diversity in this area after the Kellwasser extinction event at the end of the Frasnian, our attention is here focused on rhynchonellides and athyrides. Six rhynchonellide species are described belonging to five genera as well as a single athyride species (Crinisarina pseudoglobularis n. sp.), which is new to science. The genus Crinisarina is reported for the first time in the South Armenian Block (SAB), which was then part of the northern margin of Gondwana. Some of the rhynchonellides identified were previously recognized in this area, but they require modern documentation and taxonomic reassessment. More particularly, it is the first time that the internal structure of Sartenaerus baitalensis (Reed, 1922) is illustrated, taking into account that it is the type species of a biostratigraphically significant Famennian genus. One of the oldest punctate rhynchonellide species, Greira transcaucasica Erlanger, 1993, is described for the first time from Armenia and its intraspecific morphological variability is documented quantitatively. From a paleobiogeographic viewpoint, the studied brachiopod fauna clearly shares affinities with contemporaneous ones from other regions of the Gondwanan northern margin that extend eastwards of the SAB to Afghanistan and Pamir, although there are also some endemic elements. UUID: http://zoobank.org/798eb5f9-ad15-4d90-bc6a-ff22ee936438

New and revised cyrtospiriferid (Spiriferida) brachiopods from the lower Famennian (Upper Devonian) of Armenia

“…However, as shown through the studies of Gaetani (1965, 1968), Brice (1971), and Brice et al (1973, 1999), a single bioprovince may be individualized for the Upper Devonian brachiopod assemblages found along the northern margin of Gondwana. Based on their study of lower Famennian rhynchonellides and athyrides from Armenia, Serobyan et al (2021) concurred recently with this viewpoint and argued for a rather uniform early Famennian brachiopod bioprovince that was developed between Pamir (to the east) and the Anatolide-Tauride microplate (to the west) (Fig. 10).…”

“…They diversified rapidly during the Frasnian and proliferated on tropical/subtropical platforms during the Late Devonian (Ma and Day, 1999) until their extinction at the end of the Famennian, during the Hangenberg event (Carter and Gourvennec, 2006; Mottequin et al, 2014). Thanks to their richness in brachiopods, the Upper Devonian sedimentary sequences of Armenia can provide interesting insights to improve our understanding of brachiopod changes in diversity in relation to well-known extinction events (Abrahamyan, 1957, 1964, 1974; Arakelyan, 1964; Alekseeva et al, 2018a, b; Serobyan et al, 2021). However, although Upper Devonian–lower Carboniferous brachiopods of the Lesser Caucasus (Armenia and Nakhichevan; Fig.…”

“…However, although Upper Devonian–lower Carboniferous brachiopods of the Lesser Caucasus (Armenia and Nakhichevan; Fig. 1) were studied systematically by Abrahamyan (1957, 1964, 1974), Grechishnikova (1986, 1996), and more recently by Alekseeva et al (2018a, b) and Serobyan et al (2019, 2021, 2022), they still remain largely undocumented from taxonomic and biostratigraphic points of view. This is particularly true for the cyrtospiriferids, among which most species were described previously without examination of the most fundamental features in brachiopod taxonomy, such as their internal structure and type of micro-ornament, which are significant for their supraspecific classification.…”

On two cyrtospiriferid brachiopod species from the lower famennian of central Armenia

“…These sequences contain a diverse and abundant brachiopod fauna, among which the spiriferides are the most common. Brachiopods were systematically studied by Abrahamyan (1957Abrahamyan ( , 1964Abrahamyan ( , 1974 and Serobyan et al (2019Serobyan et al ( , 2021Serobyan et al ( , 2022a. Most notably, Serobyan et al (2022a) revised Spirifer orbelianus Abich, 1858 and erected the cyrtospiriferid genus Aramazdospirifer for this biostratigraphically important species for the lower Famennian of the Lesser Caucasus.…”

Frasnian (Upper Devonian) Brachiopods From Armenia: Biostratigraphic and Palaeobiogeographic Implications

“…wrote an article mainly devoted to the Frasnian species, where she described some rhynchonellides and atrypides, which were partly revised by her afterwards (Abrahamyan 1974), in addition to newly studied Frasnian species. However, as shown by some recent papers dealing with the Devonian brachiopods of the Lesser Caucasus (Alekseeva et al 2018a, b;Serobyan et al 2019Serobyan et al , 2021Serobyan et al , 2022a, in contrast to the Famennian brachiopods, the Frasnian ones have received relatively little attention and remain largely undocumented from a taxonomic point of view, not to mention their palaeoecological, palaeobiogeographic, or evolutionary understandings.…”