Proscyllium ” magnificum, Last & Vongpanich, 2004

3.1 | Generic allocation of “ Proscyllium ” magnificum View in CoL

The main characters distinguishing Proscyllium (based on P. habereri only) from Ctenacis (based on C. fehlmanni ) are head narrower and shorter (length 16% – 18% TL vs. 23% in C. fehlmanni ), fifth gill opening about half length of third (vs. more than half length of third); anterior nasal flaps very large, reaching nearly to upper symphysis (vs. small, with edges well anterior to upper symphysis); internarial space very narrow (nostril width 1.7 – 2.2 vs. 1.1 times internarial space); head and trunk very short (precloacal length 39 – 41 vs. 46% TL); distance between paired fins greater than head length (vs. less than head length); first dorsal origin well posterior to pectoral-fin free rear tips (vs. over pectoral-fin inner margins); anal origin slightly anterior to second dorsal origin (vs. slightly posterior to second dorsal fin-origin); edge of sphenopterotic ridge nearly parallel to longitudinal axis of cranium in dorsal view (vs. diagonal to longitudinal axis of cranium, Figure 1e,f vs. Figure 1a,b); anterior fontanelle relatively narrow, about as wide as long (vs. broad, wider than long, Figure 1e,f vs. Figure 1a,b); tooth files less numerous (upper jaw with 46 – 62 vs. 86 files); more vertebrae (total centra 146 – 168 vs. 136) ( Compagno, 1973, 1988).

When comparing to the above key differences, “ Proscyllium ” magnificum agrees with Ctenacis in having: broad and long head (head length 21 – 23% TL, see Table 1); fifth gill slit more than half length of third slit; nostril width 1.1 – 1.2 in internarial space; precloacal length 44 – 45% TL; distance between paired fins less than head length; anal-fin origin slightly posterior to second dorsal-fin origin; edge of sphenopterotic ridge diagonal to longitudinal axis of cranium; anterior fontanelle wider than long (Figure 1c,d); 80 upper tooth files. Several characters of “ Proscyllium ” magnificum were intermediate between Proscyllium and Ctenacis : anterior nasal flaps moderately large but not edges reaching to upper symphysis; first dorsal fin origin slightly posterior to pectoral-fin free rear tips; total centra 140 – 143.

The CT scan of Proscyllium habereri revealed that the internal carotid foramina are located close together, with the distance between them less than twice the distance between each foramen and their adjacent stapedial foramen. In comparison, the CT scans of Ctenacis fehlmanni and “ Proscyllium ” magnificum revealed that the internal carotid foramina are located closer together, the distance between them more than four times the distance between each foramen and their adjacent stapedial foramen.

Based on the strong alignment of internal and external morphological characters and meristics, “ Proscyllium ” magnificum is reassigned to the genus Ctenacis .