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

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http://doi.org/ 10.1111/j.1096-3642.2009.00578.x

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http://treatment.plazi.org/id/2B52681A-FFBD-FFAB-FC6B-FB7314D7BADE

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PANXIOSTEIDAE WANG, 1979
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FAMILY PANXIOSTEIDAE WANG, 1979  

The analyses ( Fig. 9 View Figure 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 View Figure 9 ), 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 View Figure 9 ; 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 View Figure 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 View Figure 9 ), but emend its membership to include only the Dunkleosteidae   (node 11; Fig. 9B View Figure 9 ), as outlined above, and the Panxiosteidae   (node 10; Fig. 9B View Figure 9 ). 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   ).