Endemic earliest Lochkovian species ofCaudicriodus(conodont) from southern Laurentia and the Silurian–Devonian boundary

Abstract

Two Caudicriodus species from lowermost Devonian strata in southern Laurentia (Texas-Oklahoma-Western Tennessee), C. anitae sp. nov. and C. murphyi sp. nov., are endemic forms that appeared during the positive d 13 C excursion associated with the Klonk Event. The other Caudicriodus species that occur during the Klonk Event and that are often used to recognize the base of the Devonian, C. hesperius and C. woschmidti, differ in that the I elements of the southern Laurentia species possess a middle row of nodes on the transverse ridges of the spindle. The apparatus of C. murphyi sp. nov. possesses three groups of elements in addition to the I element: F elements (short wide coniforms); D elements (denticles on the posterior margin) and C elements (slender coniforms with basally flaring costae). Strong provinciality in slightly younger Lochkovian Caudicriodus species was demonstrated earlier, and we propose that Caudicriodus species radiated independently into endemic species in different geographic regions just before or during the Klonk Event. A form originally described as C. woschmidti hesperius by Simpson (1998) is reinterpreted as a late Ludlow-Pridoli species of Praeicriodus, P. simpsoni sp. nov., with an I element and apparatus structure probably ancestral to Caudicriodus.

The latest encrinurid trilobites from the Lower Devonian of Xinjiang, Northwest China

“…For example, the supposed Early Devonian Encrinurus sp. from Tien-Shan occurs in the same horizon as the conodont Ozarkodina steinhornensis praeoptima (Biske et al 1977), but using the species of the Ozarkodina eosteinhornensis-steinhornensis group (now Zieglerodina ) to define the Silurian–Devonian boundary is considered unreliable (Barrick et al 2021). The supposed Early Devonian encrinurids from Podolia are from the Tajna Beds, the base of which was once considered to coincide with the Silurian–Devonian boundary.…”

Running across the Silurian/Devonian Boundary along Northern Gondwana: A Conodont Perspective

“…hesperius, togheter with ozarkodinids referable to Zieglerodina sp. However, Barrick et al (2021) [201]…”

Morphologically distinct P1 elements of Zieglerodina (Conodonta) at the Silurian- Devonian boundary: review and correlation

“…Slavík & Hladil (2020) introduced the Icriodus Event that represents the origin and rapid global dispersal of the genus. This should not be mistaken by the often misused Klonk Event by Jeppsson (1998) that has been recently misunderstood by Barrick et al (2021). The origin of the early Devonian taxa of the family Icriodontidae is also uncertain, as is the exact phylogenetic relationships among the youngest Icriodus species [e.g., I. hesperius Klapper & Murphy, 1975;I.…”

“…The origin of the early Devonian taxa of the family Icriodontidae is also uncertain, as is the exact phylogenetic relationships among the youngest Icriodus species [e.g., I. hesperius Klapper & Murphy, 1975;I. woschmidti Ziegler, 1960;and I. postwoschmidti (Mashkova, 1968); Carls et al 2007, and the recently described new taxa from Laurentia by Barrick et al 2021].…”