New taxonomic synopses and revision of the scombroid fishes (Scombroidei, Perciformes), including billfishes, from the Cenozoic of territories of the former USSR

Abstract

ABSTRACT:We present an overview of all known fossil scombroid fishes (Scombroidei, Perciformes) of the former USSR, many taxa of which are described in a language other than Russian for the first time. Also new is the application of a cladistic framework for these taxa. For each taxon, short taxonomic synopses with the most relevant characteristics (synapomorphies, meristic counts) are presented in a form useful for future cladistic analysis. As an exception, we present an extensive systematic description of the billfish †Hemingwaya sarissa Sytchevskaya & Prokofiev, because we disagree with earlier interpretations. The ‘gempylid’ †Hemithyrsites maicopicus Daniltshenko retains its generic name, which is considered the valid name of what is also known as Promethichthys Gill. A new tribe, †Eocoelopomini, is erected to contain the genera †Eocoelopoma Woodward, †Palaeothunnus Bannikov, and †Micrornatus Monsch. It is questioned whether species previously described as belonging to Thunnus South should be classified in that genus. A new species of tribe Scomberomorini, †Neocybium parvidentatum, is described from the Bartonian of W Kazakhstan. A specimen of †Auxides (questionably Maastrichthian, Iran), also reported here, possibly extends the radiation of †Auxides, and scombroids as a whole, further back in time. The fossil record of the Blochiidae is probably extended downwards to the Thanetian.

The one that got away from Smith Woodward: cranial anatomy of Micrornatus (Acanthomorpha: Scombridae) revealed using computed microtomography

“…69, pl. 21) shows diagnostic features of Eocoelopomini (Monsch & Bannikov 2012). The frontals as reconstructed by these authors are more similar to those of Micrornatus than Eocoelopoma, and appear to be concave anterior to the pineal region (Darteville & Casier 1949, fig.…”

“…Eocoelopoma has fused of upper and lower hypural plates (Collette et al 1984, character 34;Johnson 1986, character 39; Palaeothunnus retains separate dorsal and ventral plates), which has been interpreted as either a synapomorphy of a subset of Scombridae (Collette et al 1984) or of some scombrids plus billfishes (Johnson 1986). Additional features of the caudal skeleton of Eocoelopoma that support this placement include preural centra 2-4 shortened, and a bony caudal keel (Bannikov 1985;Monsch & Bannikov 2012). On these grounds, Monsch & Bannikov (2012, p. 278) tentatively propose that Eocoelopomini is the extinct sister lineage of Sardini + Thunnini.…”

“…Discord with respect to the relationships of Scombridae is particularly relevant to interpreting the phylogenetic affinities of Micrornatus because it has consistently been identified as a scombrid for the past century (Woodward 1901;Casier 1966;Bannikov 1985;Monsch & Bannikov 2012; but see Monsch 2005). We review the evidence for the phylogenetic placement of Micrornatus here, with the obvious caveats that must accompany such an exercise given the uncertainty surrounding the relationships of scombroids sensu lato.…”

“…Monsch & Bannikov (2012) recognize these three genera as a clade they call Eocoelopomini, united by two cranial features present in all putative members: postero-superior fossae extending to mid-orbit combined with thickenings of the frontals located anterior to these fossae and ornamented with radiating ridges (such features are also common to Landanichthys from Angola; Darteville & Casier 1949, fig. 69).…”

“…Evolutionary timescales for diversification in this group, variously called Pelagia or Scombriformes, vary by tens of millions of years (Betancur-R et al 2013;Miya et al 2013;Near et al 2013;Santini et al 2013). Part of this ambiguity stems from difficulties in applying fossil-based calibrations in molecular clock studies of scombroids and their immediate relatives, as no extinct member of these groups has ever been placed in a formal, published cladistic analysis (informal or adapted trees are found in Bannikov (1985) and Monsch & Bannikov (2012); a formal, but unpublished, cladistic analysis is presented by Monsch (2000)). A re-evaluation of the relationships of scombroids both fossil and modern is desperately needed, but well beyond the scope of this contribution.…”