Doctoral thesis

Evolutionary history of tselfatiiforms, a weird group of Cretaceous ray-finned fishes, with a focus on Lebanese taxa

ContributorsEl Hossny, Tamaraorcid
Number of pages336
Imprimatur date2023
Defense date2023

The Actinopterygians, a highly diverse vertebrate group, represent about half of today's vertebrate species. Their diversity during the Cretaceous period mirrored the present scenario, with a significant surge, particularly in the mid-Cretaceous, likely linked to rising sea levels and temperatures. These factors, intricately connected or perhaps even triggering diversity explosions in actinopterygians, notably within teleosts like stem Acanthomorpha and tselfatiiforms.

The 'Tselfatiiformes,' a diverse fish group appearing in the Albian and extending to the Campanian, remains enigmatic in its phylogenetic position within teleosts. Despite numerous studies, their relationships within the group remain unresolved. Recent research by Taverne and Gayet (2005) identified 'Tselfatiiformes' as a basal clupeocephalan, comprising three families: Protobramidae, Plethodidae, and Eoplethodidae. However, further examination of new 'Tselfatiiformes'-like material is needed, and some existing material requires revision.

This thesis aims to explore and resolve the monophyly, phylogenetic position, and relationships within 'Tselfatiiformes.' It involves describing new material, establishing a new phylogenetic framework, mapping their radiation and dispersal, and identifying their niche within the ecosystem.

Lebanese Cenomanian localities, notably Haqel and Hjoula, boast an extensive collection of Mesozoic fish species. Despite their antiquity, their precise age has remained disputed. A collaborative effort using various approaches, including on-site measurements, extensive sampling, and thorough investigations of fossil findings, provided insights. Haqel and Hjoula are confirmed to be early Late Cenomanian, while Nammoura's age determination remains inconclusive.

New material from Haqel, Lebanon, resembling known genera like Abisaadichthys and Araripichthys, shares distinctive traits with both, leading to the establishment of a new genus, Ypsiloichthys sibelleae. Its unique anatomical features place it within Teleostei, further emphasizing the need for a refined phylogenetic framework for precise taxonomic placement.

Additional specimens from Germany and Lebanon, exhibiting fusiform bodies with elongated premaxillae, resemble pelthodids and billfishes. These findings resulted in the identification of a new genus, Rhamphoichthys taxidiotis, with unique characteristics, hinting at a niche similar to extant xiphioids.

Furthermore, the study incorporates 'Tselfatiiformes' into a comprehensive phylogenetic analysis, indicating non-monophyly within the group. It establishes Protobramidae and Plethodidae as stem Acanthomorpha, unveiling their evolutionary timelines, swimming patterns, and geographic distributions during the Cretaceous period.

This thesis elucidates the 'Tselfatiiformes' split into Protobramidae and Plethodidae, showcasing their relationship as stem Acanthomorpha. It achieves its objectives by describing new taxa, constructing a new phylogenetic framework, discussing family phylogenies and characteristics, and analyzing their paleoecology and distribution. The necessity for extensive datasets before naming alternative groups is emphasized.

  • Actinopterygii
  • Tselfatiiforms
  • Teleostei
  • Acanthomorpha
  • Cretaceous
  • Lebanon
  • USA
NoteIn collaboration with the Muséum d'histoire naturelle de la Ville de Genève
Citation (ISO format)
EL HOSSNY, Tamara. Evolutionary history of tselfatiiforms, a weird group of Cretaceous ray-finned fishes, with a focus on Lebanese taxa. 2023. doi: 10.13097/archive-ouverte/unige:173876
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Creation12/19/2023 11:26:57 AM
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