Paxtoninae new subfamily Fraser, 2014

Mabuchi, Kohji, Fraser, Thomas H., Song, Hayeun, Azuma, Yoichiro & Nishida, Mutsumi, 2014, Revision of the systematics of the cardinalfishes (Percomorpha: Apogonidae) based on molecular analyses and comparative reevaluation of morphological characters, Zootaxa 3846 (2), pp. 151-203 : 176

Paxtoninae new subfamily Fraser & Mabuchi

Type genus Paxton Baldwin & Johnson 1999

Diagnosis. One continuous dorsal fin, VI,19; anal fin I,15–16; internal support of spines by serial proximal-middle radials in near articulation with gaps between each spine, similar distance between 6th and 7th elements; sixth proximal-middle radial without serial spine or ray; fifth and seventh proximal-middle radials with serial spine and ray respectively; one supernumerary dorsal spine; supraneurals absent; first anal proximal-middle radial curved; 9+8 branched principal caudal fin-rays; caudal fin truncate or slightly rounded; vertebrae 10+14; epineurals on first two vertebrae; rod-like ribs on 3rd to 10th vertebrae; epineurals present on ribs of 3rd to 9th vertebrae; supramaxilla and basisphenoid absent; six infraorbitals, without shelf on third, only first and second in contact, third sixth not in contact and all small; medial and lateral extrascapular absent; preopercle ridge smooth and edge with single large spine at angle, preopercle, including spine, covered by skin; prootic excluded along internal orbit ring by pterosphenoids and parasphenoid; parietal separated by supraoccipital; a unique postfrontal bone; uroneurals absent; two epurals; haemal spines for PU3 and PU4 each fused to centra; parhypural fused to hypurals 1+2; terminal centrum fused with hypurals 3+4; hypural 5 absent; second epibranchial articulating with third pharyngobranchial; anterior and posterior ceratohyals sutured together by a few interdigitating struts medially; anterior ceratohyal not perforated; seven branchiostegals, anterior three ventrally followed by two on distal side of anterior ceratohyal, two on distal side of posterior ceratohyal; single postcleithrum.

Distribution. This monotypic subfamily is known only from northwestern Western Australia, collected by trawls in 40– 80 m. Only six specimens known ( Baldwin & Johnson 1999; Atlas of Living Australia http:// www.ala.org.au/australias-species/).

Remarks. This subfamily contains one genus, one species: Paxton concilians Baldwin & Johnson 1999 . Because the species was absent from the present molecular analyses, this tribe is proposed based only on morphology. Paxton is characterized by a series of morphological apomorphies not found in any other apogonid ( Baldwin & Johnson 1999; Fraser 2013b ). These apomorphies include: VI dorsal spines; a continuous dorsal fin as VI,19 without a notched division or expanded pterygiophores at the transition from spines to branched, segmented fin-rays (all other apogonids have deeply divided dorsal fins and unbranched segmented first fin-ray); sixth pterygiophore without a serial spine or ray or subdermal remnants (unique for a continuous dorsal fin?); dorsal spines IV–VI subequal, longer than spines I–II (all other apogonids have unequal first dorsal-spines); anal fin with I,15–16, the spine in supernumerary position, with the first branched, segmented ray in series and supported by the first pterygiophore (all other apogonids have 2 anal spines); entire margin of preopercle covered by skin (all other apogonids have exposed preopercular edges); third epibranchial toothplate lacking (all other apogonids have a toothplate); fifth hypural absent (all other apogonid have a splint-like fifth hypural); anterior and posterior pelvicgirdle processes lacking; an autogenous wishbone-shaped cartilage present between proximal bases of left and right pelvic fins; medial and lateral extrascapular absent (all other apogonids have a lateral extrascapular and Gymnapogon has both); principal caudal fin-rays 9+8, all branched (all other apogonids have the upper-most and lower-most principal caudal fin-rays unbranched and some Gymnapogon species have additional unbranched principal caudal fin-rays); and postfrontal bones. Bergman's (2004) figures and descriptive text shows that Paxton has a much reduced number of cephalic pores associated with canals compared with Gymnapogon , Pseudamiops , Cercamia or Lachneratus . She followed up with ..."The cephalic lateralis of Paxton , despite its simple canal structure, few perforations and, lack of secondary canal development, is characterized by an extensive network of sensory papillae. This characteristic, in combination with the lack of perforation, distinguishes Paxton from all other apogonids." Baldwin & Johnson's analysis provided a convincing list of synapomorphic characters with other pseudamine fishes and therefore did not to recognize a separate family or subfamily. They hypothesized that Gymnapogon and Paxton are sister genera. Paxton , Cercamia and Gymnapogon share a fused parhypural with fused hypurals 1 and 2 (see these publications for characters among these genera: Fraser 1972 ; Hayashi 1991; Baldwin & Johnson 1999). Larval stages may prove useful in determining if there is more than one sequence of fusing these elements. Gymnapogon has a single preopercular spine and Cercamia has 2–3 serrations near the angle and a single serration on the ridge. The preopercle of Paxton is unexposed, covered by skin with a single, unexposed spine. An infraorbital shelf is present in Gymnapogon and Cercamia and all six infraorbitals have contiguous relationships, whereas only the first two infraorbitals are contiguous for Paxton . Cercamia has some weak ctenoid scales but no pored or pitted lateral line. We conclude that Gymnapogon and Cercamia are sister genera (see remarks for the tribe Gymnapogonini ) and that the fusion of the parhypural with fused hypurals 1 and 2, preopercular spine and other shared reductive characters occurred independently in Paxton . Paxton is given subfamily recognition.