Geological Society of London
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The varasichthyid and other crossognathiform fishes, and the Break-up of Pangaea

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journal contribution
posted on 2016-06-21, 12:11 authored by Gloria Arratia

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.