“Paradox Lost”: Skeletal Ontogeny of Indostomus paradoxus and Its Significance for the Phylogenetic Relationships of Indostomidae (Teleostei, Gasterosteiformes)

A long-bodied centriscoid fish from the basal Eocene of Kabardino-Balkaria, northern Caucasus, Russia

“…Pietsch 1978;Johnson and Patterson 1993;Britz and Johnson 2002;Keivany and Nelson 2006;Kawahara et al 2008;Wilson and Orr 2011). A comprehensive morphological and phylogenetic survey of the group, primarily based on osteology was conducted by Orr (1995) in a sadly underused thesis of considerable insight and breadth.…”

“…According to Orr (1995), the Macroramphosa includes a pair of sister groups, the Centriscoidea (centriscids and macroramphosids) and Syngnathoidea (pegasids, solenostomids and syngnathids). He proposed 13 unique centriscoid characters, of which three (sphenotic articulating with hyomandibula through a ventral Britz and Johnson (2002) process; neural spine of the second preural centrum fully developed; anterior body encased by interconnected dermal plates; Figs. 2b, 3 and 4) have been observed in Gerpegezhus.…”

“…Such a condition is unique within centriscoids given that macroramphosids possess an additional series of unpaired ventromedian plates extending from the isthmus to the anus (see Fig. 4c; Jurgensen 1908;Britz and Johnson 2002).…”

Branchial structures in the Gasterosteiformes, with special reference to myology and phylogenetic implications

“…Based upon seven derived characters, monophyly of the Gasterosteiformes was proposed cladistically by Johnson and Patterson (1993), Britz and Johnson (2002) later adding the unique development of the pectoral girdle as further support. Although molecular data (Miya et al, 2003) subsequently showed the gasterosteiforms to be nonmonophyletic, the traditional framework of the order (i.e., Nelson, 1994) is followed here, because only three taxa (Gasterosteus, Hypoptychus, and Indostomus) were sampled in the molecular study.…”

“…A composite nature of "obliquus ventralis 1" and "rectus ventralis 1" is suggested for Solenostomus. Britz and Johnson (2002) argued that Indostomidae should be included in the Gasterosteoidei (sensu Pietsch, 1978), rejecting a close affinity between that family and the syngnathoid Pegasidae, as proposed by Pietsch (1978) and Johnson and Patterson (1993). Although Indostomus and Pegasus are unique in Gasterosteiformes in having a large epibranchial 4 and pharyngobranchial 3, the associated muscles and their arrangements are generally basic in Indostomus (see Tables 2,3), but specialized in Pegasus (as in syngnathoids, having well-developed recti ventrales interni and externi).…”