The oldest ionoscopiform from China sheds new light on the early evolution of halecomorph fishes

Abstract

The Halecomorphi are a major subdivision of the ray-finned fishes. Although living halecomorphs are represented solely by the freshwater bowfin, Amia calva, this clade has a rich fossil history, and the resolution of interrelationships among extinct members is central to the problem of understanding the origin of the Teleostei, the largest clade of extant vertebrates. The Ionoscopiformes are extinct marine halecomorphs that were inferred to have originated in the Late Jurassic of Europe, and subsequently dispersed to the Early Cretaceous of the New World. Here, we report the discovery of a new ionoscopiform, Robustichthys luopingensis gen. et sp. nov., based on eight well-preserved specimens from the Anisian (242-247 Ma), Middle Triassic marine deposits of Luoping, eastern Yunnan Province, China. The new species documents the oldest known ionoscopiform, extending the stratigraphic range of this group by approximately 90 Ma, and the geographical distribution of this group into the Middle Triassic of South China, a part of eastern Palaeotethys Ocean. These new data provide a minimum estimate for the split of Ionoscopiformes from its sister clade Amiiformes and shed new light on the origin of ionoscopiform fishes.

Phylogenetic Relationships of the Triassic Archaeosemionotus Deecke (Halecomorphi, Ionoscopiformes) from the ‘Perledo Fauna’

“…These relationships are in agreement with previous phylogenetic analyses [15] , [16] , [42] , although these studies do not include Archaeosemionotus or Robustichthys . In the cladistic analysis of Xu et al [18] , the relationships of R. luopingensis remain unresolved in a polytomy with a clade equivalent to our Ophiopsidae and a clade ( Quetzalichthys + Oschunia brevis + Ionoscopus ). The relationships within these two clades remain also unresolved [18] .…”

“…In the cladistic analysis of Xu et al [18] , the relationships of R. luopingensis remain unresolved in a polytomy with a clade equivalent to our Ophiopsidae and a clade ( Quetzalichthys + Oschunia brevis + Ionoscopus ). The relationships within these two clades remain also unresolved [18] . Neither Furo nor Archaeosemionotus are included in the analysis of Xu et al [18] and, thus, the incorporation of these two taxa in our analysis made the phylogenetic relationships of Robustichthys clear.…”

“…For the analysis we assembled a data matrix of 57 characters and 21 taxa using Mesquite Version 2.75 [14] . This data matrix is a subsample of a larger matrix compiled by merging the data matrices for amiiforms of Grande and Bemis [15] , the data matrix for ophiopsids of Alvarado-Ortega and Espinosa-Arrubarrena [16] , and by adding Archaeosemionotus connectens and Furo muensteri [17] from the Late Jurassic of southern Germany, and the recently described Robustichthys luopingensis [18] , from the Middle Triassic of southern China ( Text S1 ). Character scores for the latter taxa are based on Lane and Ebert [19] and Xu et al [18] , respectively.…”

A new species ofPlatysiagumfrom the Luoping Biota (Anisian, Middle Triassic, Yunnan, South China) reveals the relationship between Platysiagidae and Neopterygii

“…Of these, the crown-group Neopterygii includes most taxa in the Luoping fish assemblage, making up nearly 55% of the total, based on counts of the collected specimens. Common elements include the fusiform Sangiorgioichthys and Robustichthys, naked Marcopoloichthys and Gymnoichthys, and deep-bodied Luoxiongichthys and Kyphosichthys Tintori et al 2010;López-Arbarello et al 2011;Wen et al 2012;Xu & Wu, 2012;Xu et al 2014a). This assemblage of taxa provides an excellent example of the radiation of neopterygian fishes, a key part of the biotic recovery in the sea after the Permian-Triassic mass extinction Lombardo et al 2011;Chen & Benton, 2012;Benton et al 2013;Tintori et al 2014;Romano et al 2016).…”

Guelb el Ahmar (Bathonian, Anoual Syncline, eastern Morocco): First continental flora and fauna including mammals from the Middle Jurassic of Africa

“…The ionoscopiform fishes are also widely distributed in Europe, Africa, and North and South America from the Middle Triassic to the Late Cretaceous (e.g., Vullo and Courville, 2014;Xu et al, 2014). The Mawsoniidae had a Triassic Pangean distribution (Miguel et al, 2014).…”