Taxonomy and biostratigraphy of Middle and Late Triassic elasmobranch ichthyoliths from northeastern British Columbia

Abstract

Diverse and abundant Middle and Late Triassic elasmobranch ichthyoliths (microscopic shark teeth and scales) coexisting with conodonts, ammonoids, and bivalves were recovered from carbonates of the Pardonet, Baldonnel, Ludington, and Liard formations in the Peace River area of British Columbia. These faunas provide an excellent biostratigraphical framework for Triassic strata. Results from this study demonstrate that ichthyoliths can be used in basin analyses to date and correlate strata. The following summarizes the main achievements of this project. 1. Systematic description and illustration of Triassic elasmobranch ichthyoliths include seven species of teeth and nineteen new form genera and fifty-three new form species of scales. 2. Ichthyolith distributions consist of distinct faunal assemblages for the Ladinian, Upper Carnian, and Middle Norian. The Carnian/Norian boundary is marked by the disappearance of many Ladinian and Carnian elasmobranch species. In the Middle Norian, elasmobranch faunas reached a new peak of diversity and abundance. 3. A provisional ichthyolith zonation for the Middle and Upper Triassic is proposed for the Peace River area. The sequence of coeval conodonts and (or) ammonoids indicate that the Coniunctio aequirugosa ichthyolith Zone is Ladinian, the Synechodus multinodosus ichthyolith Zone is Upper Carnian, and the Synechodus incrementum ichthyolith Zone is Lower and Middle Norian. 4. New approaches to ichthyolith identification include recognizing diagnostic characteristics of scale and tooth bases, and using binomial, form, and utilitarian taxonomic systems. 5. Interpretations of histological and morphological features of elasmobranch teeth suggest that more derived neoselachian species than were originally known are present in the Triassic.

Pyknotylacanthus spathianus gen. et sp. nov., a new ctenacanthoid from the Early Triassic of Bear Lake (Idaho, USA)

“…An attempt is made to assess the variation by comparing it to extant and fossil shark species and to the framework of formal taxa introduced by Johns et al (1997).…”

Morphometric Discriminant Analysis of isolated chondrichthyan scales for palaeoecological inferences: the Middle Triassic of the Iberian Chain (Spain) as a case of study

“…Previous studies (Pla et al, 2009;2013) on isolated teeth from the same samples that the scales of this study identified the following tooth based species: Palaeobates angustissimus (Agassiz, 1838), Pseudodalatias henarejensis Botella, Plasencia, Márquez-Aliaga, Cuny and Dorka, 2010; Hybodus bugarensis Pla, Márquez-Aliaga and Botella, in press; Prolatodon bucheri (Cuny, Rieppel and Sander, 2001); Prolatodon contrarius (Johns, Barnes and Orchard, 1997); Hybodus plicatilis Agassiz, 1838; and Lissodus aff. lepagei (Fig.…”

The oldest record of gnathostome fossils from Greece: Chondrichthyes from the Lopingian of Hydra Island

“…The Hydriot denticle compares favorably to the par-agenus Moreyella (Gunnell, 1933;Hansen, 1986), which has been tentatively affiliated with Carboniferous-Permian hybodontiform chondrichthyans (e.g., Derycke-Khatir et al, 2005). The Triassic paragenera Fragilicorona and Labascicorona (Johns et al, 1997) also display very similar, tricuspid distal crowns like the denticle in question, but their systematic affinities beyond the euselachian level have not been discussed (Ivanov et al, 2013). Hybodontiform dermal denticles can exhibit disparous morphologies, even in the same individual, ranging from somewhat stockier and shorter types with more keels and stout or undeveloped necks (Reif, 1978), to more delicate and elongate ones like AMPG 551.…”

“…Remarks. The presence of a slender crown with three keels on its anterior surface and a narrow neck are common features in scales of PaleozoicMesozoic ctenacanthids, but are also common in euselachian chondrichthyans (Reif, 1978;Hansen, 1986;Rieppel et al, 1996;Johns et al, 1997;Derycke-Khatir et al, 2005;Ivanov et al, 2013). The Hydriot denticle compares favorably to the par-agenus Moreyella (Gunnell, 1933;Hansen, 1986), which has been tentatively affiliated with Carboniferous-Permian hybodontiform chondrichthyans (e.g., Derycke-Khatir et al, 2005).…”