Skeletal remains of the oldest known pseudocoracid shark Pseudocorax kindlimanni sp. nov. (Chondrichthyes, Lamniformes) from the Late Cretaceous of Lebanon

Abstract

A new fossil mackerel shark, Pseudocorax kindlimanni sp. nov. (Lamniformes, Pseudocoracidae), is described from the Cenomanian Konservat-Lagerstätte of Haqel, Lebanon. The new species is based on the most complete fossil of this group to date, which comprises an associated tooth set of 70 teeth, six articulated vertebral centra, numerous placoid scales and pieces of unidentifiable mineralized cartilage. The dentition of P . kindlimanni sp. nov. is marked by a high degree of monognathic heterodonty but does not exhibit the characteristic “lamnoid tooth pattern” known from other macrophagous lamniform sharks. In addition, P . kindlimanni sp. nov. shows differences in tooth microstructure and vertebral centrum morphology compared to other lamniform sharks. These variations, however, are also known from other members of this order and do not warrant the assignment of Pseudocorax outside the lamniform sharks. The new fossil is the oldest known pseudocoracid shark and pushes the origin of this group back into the Cenomanian, a time when lamniform sharks underwent a major diversification. This radiation resulted not only in high species diversity, but also in the development of a diverse array of morphological traits and adaptation to different ecological niches. Pseudocorax kindlimanni sp. nov. was a small, active predator capable of fast swimming, and it occupied the lower trophic levels of the marine food web in the Late Cretaceous.

Heterodonty and ontogenetic shift dynamics in the dentition of the tiger shark Galeocerdo cuvier (Chondrichthyes, Galeocerdidae)

“…Due to this diversity and the circumstance that teeth are the predominant remains of this group in the fossil record, teeth are critical for taxonomic identifications (e.g. Cappetta, 2012 ; Guinot et al, 2013 ; Jambura et al, 2021 ) and inference of phylogenetic relationships between extinct and extant taxa (Gates et al, 2019 ; Klug, 2010 ; Landemaine et al, 2018 ). In extant elasmobranchs, conversely, tooth morphologies are rarely used in species descriptions (Guinot et al, 2018 ), and therefore, morphological details sufficient for taxonomic differentiation are often missing.…”