Osteoglossomorpha: phylogeny, biogeography, and fossil record and the significance of key African and Chinese fossil taxa

Abstract

The Osteoglossomorpha are a clade of primitive teleostean fishes with modern representatives in five biogeogeographic regions and fossil representatives on six continents. The centre of modern diversity is in Africa but the centre of fossil diversity is in E Asia. Key fossil taxa include: †Phareodus, †Joffrichthys, and †Ostariostoma in N America; †Lycoptera, †Paralycoptera, and †Huashia among others in E Asia; †Brychaetus and possibly †Thaumaturus in Europe; †Palaeonotopterus, †Singida, and †Chauliopareion in Africa; †Tavernichthys in India; and †Musperia in SE Asia.Morphological phylogenies to date have disagreed on three main points: the relationships of †Lycoptera, of Pantodon, and of Notopterids and Mormyrids. Molecular phylogenies have similarly differed on the last two points. In this study a combined set of morphological data was generated from previous studies, including data from three recently described or redescribed taxa (the African †Singida and †Chauliopareion and the Chinese †Xixiaichthys) and maximum parsimony was used to generate a revised hypothesis of relationships. Our analysis recovered †Lycoptera, †Paralycoptera+ †Tanolepis, and †Xixiaichthys as stem-group osteoglossomorphs, †Singida as sister to Pantodon within Osteoglossidae, †Chauliopareion as a stem osteoglossid, †Ostariostoma as a stem osteoglossiform, and Notopteridae as sister to Mormyroidea and †Palaeonotopterus.These results do not lend themselves to easy explanations of osteoglossomorph biogeography involving either dispersal from a centre of origin or vicariant division of a widely distributed ancestor. Recent suggestions of an ancient (Palaeozoic) origin for osteoglossomorphs are flawed. The evidence, instead, is consistent with an origin within the Mesozoic and the biogeographic explanation involves extensive extinction of clades from continents where they occurred in the past.

Paleocene fishes from Palenque, Chiapas, southeastern Mexico

“…Remarks and comparison. Recent phylogenetic analyses published by Wilson and Murray (2008), Zhang (2006), andHilton (2003), have proved that Osteoglossomorpha and Osteoglossiformes are natural groups. Osteoglossomorpha is a teleostean group with a diagnostic relatively low number of principal caudal fin rays (18); a trend in the reduction in the number of rays in this group is present even in the most derived groups.…”

“…Unfortunately, IGM 4549 does not appear to present them. The family Osteoglossidae sensu Wilson and Murray (2008) is partially defined by the position of the lower jaw-quadrate articulation, behind the posterior level of the orbit. Among osteoglossomorphs, this condition is present exclusively in the Chinese genus Xixiaichthys Zhang, 2004.…”

A specimen of Paralycoptera Chang & Chou 1977 (Teleostei: Osteoglossoidei) from Hong Kong (China) with a potential Late Jurassic age that extends the temporal and geographical range of the genus

“…3) between the anterior part of the dorsal and anal fins and the caudal fin, with the anteriormost preserved one being an abdominal vertebra, and the rest (19) -caudal vertebrae. The number of caudal vertebrae is comparable to many stem osteoglossomorphs, like Huashia gracilis and Jinanichthys longicephalus (Wilson & Murray 2008). Most of the vertebral centra are dorsoventrally deeper than anteroposteriorly long, which may allow easier lateral movements during propulsion, as in most fish.…”

“…The specimen was then compared by standard methods with other Chinese Mesozoic osteoglossomorph fish from the collections of the Institute Vertebrate Paleontology and Paleoanthropology (IVPP; Beijing, China) and the Stephen Hui Geological Museum (SHGM (HKU), Hong Kong) (see Supplemental Table S1 in the Supplementary Information). The specimen's features were then coded against character lists from osteoglossomorph-specific phylogenetic analyses (Shen 1996;Zhang 2006;Li & Wilson 1996;Wilson & Murray 2008;Xu & Chang 2009). The review of the osteoglossoid osteoglossomorph Paralycoptera by Xu & Chang (2009) was particularly important towards the referral of SHGM L275 to this genus because of its details on anatomical variation.…”

“…In addition, Singida has a falcate anal fin instead of the triangular one in Paralycoptera (Murray & Wilson 2005) and SHGM L275. Shen (1996), Zhang (2006), Wilson & Murray (2008) and Xu & Chang (2009) Shen (1996) In comparing SHGM L275 and Paralycoptera based on the above analyses ( Tables 1, S2-S5), there were a few character state discrepancies. These unmatched characters include: (1) the condition of the neural spine on ural centrum 1 -whether the neural spine is complete or rudimentary, and (2) the number of epurals.…”