Cisnerospira(Brachiopoda, Spiriferinida), an atypical Early Jurassic spire bearer from the Subbetic Zone (SE Spain) and its significance

Abstract

The order Spiriferinida represented a significant group whose extinction is linked to the early Toarcian mass extinction event. The genusCisnerospiraManceñido, 2004, conspicuous representative of this group in the Early Jurassic of the western Tethys, is analyzed from a systematic standpoint, grounded mainly on evidence from the Subbetic domain, and its initial diagnosis is revised accordingly. A definitive suprageneric position within the subfamily Paralaballinae is formally proposed in the light of new data herein provided. Both external and internal diagnostic features and the generic and intraspecific variability are described through the analysis of theCisnerospiraspecies recorded in the easternmost Subbetic area, i.e.,Cisnerospira adscendens(Deslongchamps, 1858), C. aff.adscendens, C. angulata(Oppel, 1861), andC.?sylvia(Gemmellaro,1882). In addition, their interrelation with other records from several Tethyan basins is addressed, and the generic spectrum has been extended to include several species with high morphological affinity. This characterization thus contributes to clarify certain ambiguities in the systematics of the spiriferinids, which entails a complex taxonomy mainly based on the external features, where the ribbing pattern was given foremost classificatory value due to the lack of more reliable generic diagnostic criteria. Furthemore, a morphofunctional analysis performed inCisnerospirareveals a presumable epibenthonic libero-sessile way of life, and two alternative adaptive strategies are discussed: resting on and/or sticking in substrates with different degree of consolidation, providing a significant hydrodynamic stability to the shell.

Demise of the last two spire-bearing brachiopod orders (Spiriferinida and Athyridida) at the Toarcian (Early Jurassic) extinction event

“…However, the biconvex shell and the epifaunal mode of life alone cannot fully explain the selective survival of rhynchonellids and terebratulids, because the same characters were also common to the Early Jurassic spiriferinids, even among their very last representatives in the early Toarcian, e.g., Liospiriferina (Comas-Rengifo et al, 2006;García Joral and Goy, 2000) and Cisnerospira (Manceñido, 2004;Baeza-Carratalá, 2013;Baeza-Carratalá et al, 2016). The selective extinction of spiriferinids, together with the other spire-bearing group, the athyridids, is best explained by their internal features: the spiral brachidia and the firmly attached lophophore.…”

“…This dependence proved to be detrimental during the unfavourable environmental conditions in times of biotic crises and resulted in partial or total extinctions. The cyrtiniform genus Cisnerospira, adapted to semiinfaunal mode of life (Baeza-Carratalá et al, 2016), also relied upon the changes in the hydrodynamic regime because of the passive feeding by its fixed lophophore. Finally, all morphotypes of spiriferinids became extinct at the time of the Toarcian anoxic event.…”

“…These morphotypes commonly occurred among the spire-bearing orders (Athyridida and Spiriferinida) in the early Mesozoic, whereas the rhynchonellids and terebratulids maintained their conservative, biconvex shell form. The four morphotypes with their supposed environmental adaptation (Ager, 1967;Rudwick, 1970;Vörös, 2002;Baeza-Carratalá et al, 2016) are illustrated in Fig. 10.…”

Discovery of ventrally directed spiralia in a Permian spiriferellid brachiopod and implications for its feeding system

“…The more obvious evidence could be seen from a spiriferinoid genus, Cisnerospira Manceñido (see also Thomas ; Ager ; Baeza‐Carratalá et al . ). These spiriferinide brachiopods are also morphologically characterized by the strongly convex but weakly transverse ventral valve, which supports our notion that the orientation of spirolophe may have been caused by the spatial limitation of the mantle cavity.…”

Arab-Madagascan brachiopod dispersal along the North-Gondwana paleomargin towards the Western Tethys Ocean during the Early Toarcian (Jurassic)

“…With respect to the internal structure of Calyptoria, it can be deduced that lower Jurassic representatives of the Superfamily Spiriferinoidea Davidson, 1884 show comparable internal architecture, but analyzing the small number of previous works including serial sections with spiralium data, several features can be used as generic diagnostic criteria. Thus, Calyptoria differs from Cisnerospira Manceñido, 2004 because this latter genus displays dental plates slightly divergent dorsally, short hinge plates nearly fused to the socket ridges, crural bases very close (even attached) to the dorsal valve, dorsal median septum absent, and spiralium probably oriented ventrally up to posteriorly(Baeza-Carratalá et al, 2016c). On the other hand, Liospiriferina (probably the genus closest to Calyptoria) shows notably shorter ventral median septum, which instead persists up to 3/4 of shell-length in Calyptoria.…”