Evolutionary relationships among bullhead sharks (Chondrichthyes, Heterodontiformes)

Abstract

The evolution of modern sharks, skates and rays (Elasmobranchii) is largely enigmatic due to their possession of a labile cartilaginous skeleton; consequently, taxonomic assignment often depends on isolated teeth. Bullhead sharks (Heterodontiformes) are a group of basal neoselachians, thus their remains and relationships are integral to understanding elasmobranch evolution. Herein we fully describe †Paracestracion danielia bullhead shark from the Late Jurassic plattenkalks of Eichst€ att, Germany (150-154 Ma)for its inclusion in cladistic analysis (utilizing parsimonious principles) of morphological characters from complete †Paracestracion and Heterodontus fossil specimens as well as extant forms of the latter. The presence of two separate monophyletic clades within Heterodontiformes was confirmed, based on predominantly non-dental characters,

A Synoptic Review of the Cartilaginous Fishes (Chondrichthyes: Holocephali, Elasmobranchii) from the Upper Jurassic Konservat-Lagerstätten of Southern Germany: Taxonomy, Diversity, and Faunal Relationships

“…The placement of the pelvic and first dorsal fins suggests a slow swimming, epibenthic lifestyle [ 224 ]. Another important morphological feature of † Paracestracion is the presence of a root shelf on its teeth and the lack of development of molar teeth in juvenile specimens [ 59 ] and the lack of molariform teeth in pre-Kimmeridgian species [ 220 ].…”

“…However, Hovestadt [ 226 ] considers this species to be a nomen nudum , because the specimen lacks the dentition completely. In a more recent study, Slater et al [ 59 ] nevertheless identified this species as belonging to Heterodontus based on the position of the pelvic girdles between the dorsal fins ( Figure 20B–D ). Pending further revisions of all Late Jurassic heterodontiforms based on skeletal material might provide a better understanding of their taxonomic composition.…”

“…Pending further revisions of all Late Jurassic heterodontiforms based on skeletal material might provide a better understanding of their taxonomic composition. There could be several additional specimens of this species currently identified as † Paracestracion falcifer (e.g., SNSB-BSPG AS VI 505, SNSB-BSPG 1885 I 12a, b, JME SOS 3153, 3577) based on the relationship between first dorsal fin and pelvic girdle [ 59 ].…”

Comment on the letter of the Society of Vertebrate Paleontology (SVP) dated April 21, 2020 regarding “Fossils from conflict zones and reproducibility of fossil-based scientific data”: the importance of private collections

“…-Sharks: René Kindlimann, in Klug and Bolliger 2012;Mollen et al 2012;Kriwet et al 2015;Pollerspöck et al 2018;Jambura et al 2018Jambura et al , 2019Bracher et al 2019;Stumpf et al 2019;Slater et al 2020;…”