Astycoryphe tureki, Mergl & Budil, 2019

Mergl, Michal & Budil, Petr, 2019, Rhynchonelliform Brachiopods And Trilobites Of The ‘ Upper Dark Interval’ In The Koněprusy Area Devonian, Eifelian, Kačák Event; The Czech Republic, Fossil Imprint 75 (1), pp. 92-107 : 99-100

Astycoryphe tureki sp. nov.

Pl. 2, Figs 19–21

H o l o t y p e. Incomplete cranidium with exoskeleton,

PCZCU 2290, figured on Pl. 2, Fig. 21.

P a r a t y p e. Isolated librigena, PCZCU 2289, figured on Pl. 2, Fig. 20.

O t h e r m a t e r i a l. Fragment of thoracic segment ( PCZU 2292 ) from type locality and horizon can be questionably affiliated to this species .

Ty p e l o c a l i t y. Koněprusy, Jirásek’s Quarry, sample

TM 12.

T y p e h o r i z o n. Uppermost part of the Acanthopyge Limestone, UDI (Eifelian/Givetian boundary interval), Polygnathus ensensis Zone with Nowakia ex gr. otomari .

D i a g n o s i s. Astycoryphe , which is closely related to Astycoryphe exilis VAN VIERSEN et PRESCHER, 2010 with respect to these specific characters: marginal rim with three terrace lines sub-parallel with the border; outline of glabella wider (tr.), more pear-like posteriorly; S1–S3 only inconspicuously impressed, perceptible especially by effacing of generally much more prominent sculpture consisting of randomly arranged terrace lines (distinct especially posterolaterally). Fine pits randomly scattered on the preglabellar field are less numerous but more perceptible; these are missing on L1 and L2 and on the adaxial part of the palpebral lobes. Posterior border furrow on librigena is less sharply bent posteriorly.

D e s c r i p t i o n. The cranidium is only moderately vaulted. The anterior contour of the cranidium is broadly rounded. The anterior border is strongly vaulted, narrow, bearing three well-defined, border-parallel terrace ridges. The glabella is well-demarcated anteriorly and laterally by deep furrows, anterior to S0 it broadens slightly between the front and S2, strongly between S2 and S1, and slightly between S1 and deep S0. β is positioned further abaxially than δ; δ is positioned opposite S1. S0 is narrow, deepens abaxially. S1 and S2 are only slightly impressed; L1 and L2 are poorly defined. S3 is almost indiscernible. The entire glabella and palpebral lobes are covered with randomly oriented prominent terrace ridges that are distinctly inflated especially posterolaterally. The occipital ring is not preserved. Preglabellar and librigenal fields are slightly more downward sloped outside of the well-developed tropidium, represented by one ridge only. The lateral and posterior borders are strongly vaulted. The proximal part of genal spine is robust, wide, and the posterior border furrow is arched. The librigenal field is devoid of ornamentation.

R e m a r k s. Astycoryphe tureki sp. nov. appears to be closely related to A. exilis vAN VIERSEN et PRESCHER, 2010 from the upper Eifelian of Ardennes (lower part of the Hanonet Formation). Both species share the general configuration of the cranidium, especially very moderate vaulting of the glabella, characteristic pits on the preglabellar field and its vaulting in sag. cross-section. Both species also share minute dimensions and, furthermore, their stratigraphical occurrence in the uppermost Eifelian. Both species differs by features mentioned in differential diagnosis. Astycoryphe tureki sp. nov. shares, however, some features also with A. jorusi vAN VIERSEN et PRESCHER, 2010 , also from the upper Eifelian of Ardennes (lower part of the Hanonet Formation). These include in particular the glabella outline and less prominent S1–S2, as well as shape of the free cheeks with robust base of genal spine and the course of the anterolateral and posterior border furrows. The two species differ, however, in their different ornamentation and presence of pits on the preglabellar field in the new species. As A. jorusi occurs in the same stratigraphical interval (uppermost Eifelian), it probably forms a group of species including A. exilis and A. tureki – possibly belonging to the latest representatives of the Astycoryphe evolutionary lineage which was terminated by the Taghanic Event (see Feist 2003: 433). The poorly preserved cephalon of the holotype specimen of the type species, Astycoryphe senckenbergiana RICHTER et RICHTER, 1919 (figured by van Viersen and Prescher 2010: fig. 7) does not enable a sufficiently detailed comparison with new species but they appear to share similar sculpture on the glabella but differ especially in the more prominent vaulting of the cranidium, wider preglabellar furrow and more prominent tropidium. Astycoryphe arduinnae VAN VIERSEN, VAN ROSSUM et PRESCHER, 2012 differs from A. tureki sp. nov. in particular in the medially discontinuous tropidium and different ornamentation of the glabella but in common has faintly impressed S1–S3 and wider outline of the glabella. Astycoryphe planifrons FEIST, 2003 differs from the new species in the “the extremely weak relief unique among all hitherto known species of Astycoryphe that have generally upraised border rims and a shorter glabella” ( Feist 2003: 437), by tr. narrower outline of the glabella and by the absence of pits on the preglabellar field.

O c c u r r e n c e. UDI, sample TM 12.