The varasichthyid and other crossognathiform fishes, and the Break-up of Pangaea
Crossognathiforms have been traditionally considered typical marine Cretaceous forms widely represented in the Northern Hemisphere and by a few members in Brazil. During the last 30 years they have been interpreted as Teleostei incertae sedis, clupeocephalans or a non-monophyletic group. New evidence indicates that the Oxfordian taxon Chongichthys (previously considered a Teleostei incertae sedis or a clupeocephalan), the Late Jurassic family Varasichthyidae (interpreted as basal teleosts), and the crossognathoids and pachyrhizodontoids form a clade here recognized as the Crossognathiformes. Varasichthyids are the sister group of a clade including Chongichthys (at the base) and crossognathoids+pachyrhizodontoids. The Crossognathiformes (including Varasichthyidae and Chongichthys) are basal teleosts placed between the Late Jurassic basal genera Tharsis and Ascalabos in one tree or between Ascalabos and the ichthyodectiforms in the second tree. The position of elopomorphs as the most basal extant teleosts is confirmed. A new interpretation of the phylogenetic position of the clade [Humbertia+[Erichalcis+[Leptolepides+Orthogonikleithrum]]], at the base of clupeocephalans, is suggested.
The presence of the Late Jurassic varasichthyids (e.g. Domeykos) in South America (Chile) and Central America (Cuba; Luisichthys), and Chongichthys (Chile), and of the Late Jurassic genera Ascalabos and Tharsis and the ichthyodectiforms (e.g. Allothrissops) in Europe (e.g. Germany) allows the proposal of a sister-area relationship between Chile and Cuba, which was the sister area of Germany during the Late Jurassic. The Late Jurassic connection between the Palaeopacific (Chilean region) and the Tethys Sea (southern Germany) was through the newly formed Central Atlantic Ocean (Cuban region) as a result of the break up of Pangaea and separation of North America, South America and Africa.
Figures & Tables
This volume, in honour of Peter L. Forey, is about fishes as palaeobiogeographic indicators in the Mesozoic and Cenozoic. The last 250 million years in the history of Earth have witnessed the break-up of Pangaea, affecting the biogeography of organisms. Fishes occupy almost all freshwater and marine environments, making them a good tool to assess palaeogeographic models.
The volume begins with studies of Triassic chondrichthyans and lungfishes, with reflections on Triassic palaeogeography. Phylogeny and distribution of Late Jurassic neoselachians and basal teleosts are broached, and are followed by five papers about the Cretaceous, dealing with SE Asian sharks, South American ray-finned fishes and coelacanths, European characiforms, and global fish palaeogeography. Then six papers cover Tertiary subjects, such as bony tongues, eels, cypriniforms and coelacanths.
There is generally a good fit between fish phylogenies and the evolution of the palaeogeographical pattern, although a few discrepancies question details of current palaeogeographic models and/or some aspects of fish phylogeny.