PANXIOSTEIDAE WANG, 1979

Carr, Robert K. & Hlavin, William J., 2010, Two new species of Dunkleosteus Lehman, 1956, from the Ohio Shale Formation (USA, Famennian) and the Kettle Point Formation (Canada, Upper Devonian), and a cladistic analysis of the Eubrachythoraci (Placodermi, Arthrodira), Zoological Journal of the Linnean Society 159 (1), pp. 195-222 : 214-215

FAMILY PANXIOSTEIDAE WANG, 1979

The analyses ( Fig. 9 ) of the phylogenetic positions of Pa. ocullus and J. timanicus suggest that they are closely related and members of the sister group of the Dunkleosteidae (node 12; Fig. 9B ), contra Long (1995). Supporting a relationship between Pa. ocullus and J. timanicus are: (1) loss of the central–marginal plate contact (character 23, state 0; see also Vézina, 1990: character 25) (2) loss of the postorbital dermal process (character 30, state 0); and (3) the confluence of the supraorbital and central sensory line grooves (character 76, state 1; the latter two character transformations represent unambiguous changes). A preliminary analysis of Plourdosteus canadensis ( Woodward, 1892) (based solely on published material and needing a more thorough review) suggests that Plourdosteus may also be a member of Panxiosteidae (supported by K. Trinajstic & K. Dennis-Bryan, unpubl. data). Vézina (1990) erected the family Plourdosteidae (Pachyosteomorphi) , which contained Eldenosteus arizonensis ( Hussakof, 1942) , Harrytoombsia elegans , J. timanicus , Kimberleyichthys (Kimberia Dennis-Bryan & Miles, 1983a) heintzi Dennis-Bryan & Miles, 1983b, Pa. ocullus , and Plourdosteus ; however, based on the current analysis, the Plourdosteidae ( sensu Vézina, 1990 ) represent a polyphyletic group. Vézina (1990) additionally united the Plourdosteidae with the Dunkleosteidae within the superfamily Dunkleosteoidea Vézina, 1990 (node 12; Fig. 9B ; we assume that Vézina followed Stensiö, 1963, who referred only Dunkleosteus to Dunkleosteidae , thereby removing Dunkleosteus from a larger dinichthyid group, and uniting it as the sister taxon to Plourdosteidae ). Later on, Gardiner & Miles (1994) considered a number of genera as members of the Plourdosteidae within the Coccosteomorphi [ Compagopiscis Gardiner & Miles, 1994 , Gogopiscis Gardiner & Miles, 1994 , Harrytoombsia , Kimberleyichthys (Kimberia) Dennis-Bryan & Miles, 1983b , Plourdosteus , and Torosteus Gardiner & Miles, 1990 (= Goujetosteus, Dennis-Bryan, 1995)]. Likewise, Long (1995; see Table 1) considered Plourdosteus as a coccosteomorph arthrodire, and also united Pa. ocullus and J. timanicus within the Plourdosteidae . A detailed analysis of the Plourdosteidae is beyond the scope of the present analysis. However, it is worth noting that the diagnostic features of the Plourdosteidae ( sensu Long, 1995 ) represent either ambiguous or missing characters in Pa. ocullus and J. timanicus .

Retaining the familial distinction noted by Wang (1979), we refer Pa. ocullus and J. timanicus to the family Panxiosteidae (node 10; Fig. 9 ), and note the possible assignment of Plourdosteus to this family (supported by K. Trinajstic & K. Dennis-Bryan, unpubl. data, based on a consideration of polymorphisms and their effects on phylogenetic analyses, although the relationships of the Panxiosteidae , among the Pachyosteomorphi , differs from the current study). Additionally, we retain the Dunkleosteoidea (node 12; Fig. 9B ), but emend its membership to include only the Dunkleosteidae (node 11; Fig. 9B ), as outlined above, and the Panxiosteidae (node 10; Fig. 9B ). This still leaves the differing opinions concerning the Plourdosteidae unresolved: (1) a pachyosteomorph sister group to Dunkleosteidae ( Vézina, 1990) ; (2) a pachyosteomorph sister group, in part, to Dunkleosteidae (= Panxiosteidae , as used here), with some members more closely related to Coccosteus cuspidatus Miller, 1841 ; or (3) a coccosteomorph family not closely related to the Dunkleosteidae ( Gardiner & Miles, 1994; Long, 1995; that also includes panxiosteids within the Plourdosteidae ).

Figures

Figure 9. A, strict consensus tree based on 98 characters and 23 taxa derived from PAUP* (consensus tree length, TL = 246; consistency index, CI = 0.498; retention index, RI = 0.502; and Rohlf’s CI = 0.708; consensus based on six trees, TL = 237, CI = 0.498, and RI = 0.537). B, strict consensus tree based on 98 characters and 22 taxa (excluding Kiangyousteus yohii, consensus TL = 237, CI = 0.498, RI = 0.535, and Rohlf’s CI = 0.993; consensus based on three trees, TL = 237, CI = 0.498, and RI = 0.535). Named nodes: node 1, Brachythoraci; node 4, Eubrachythoraci; node 5, Pachyosteomorphi; node 6, Coccosteomorphi; node 8, Aspinothoracidi; node 9, Dunkleosteus; node 10, Panxiosteidae; node 11, Dunkleosteidae; node 12, Dunkleosteoidea; and node 13, Dinichthyidae. *Character scores for Homostius compiled for the Baltic species sensu Heintz, 1934. **Scores based on Camuropiscis concinnus and Camuropiscis laidlawi.