Premaxillary and dentary teeth small, well developed, curving backwards into mouth.
A 2 Premaxilla symphysis bullous, premaxillary teeth distribution unique (Rosen, 1964).
Dietary adaptation of some extinct ruminants determined by premaxillary
Discussion: the morplometrics of the single specimen (one more in aquarium) agree with the common form; however, the slightly different humeral colour-pattern, the high number of outer premaxillary teeth (5-6 cf usually 4) and chiefly the incompleteness of the lateral line making it technically a Hyphessobrycon, suggests that we are dealing with a distinct, possibly endemic, form.
66 in SL; dorsal fin anterior to midbody; pectoral and pelvic fins relatively developed, each reaching the next respective fin; trunk scales 5/(5)33/3; anal fin iv,19; great suborbital developed, not quite reaching the suborbital canal; teeth relatively broad, broadest with 7 cusps in the front part of the mandible and in the second premaxillary series, 3 tri-to pentacuspid teeth in the first series, which is external, with the lips not developed, black coloured between the teeth; maxilla with 1 or 2 teeth, long, reaching pupil; mandible with 4 front teeth and about 8 much smaller ones on sides.
augmentation, a sublabial incision was made, and then a periosteal plane was elevated up to the anterior maxillary spine.
Radiography indicates absence of left lacrimal, left 1st, 2nd, 3rd subocular, dentary, premaxillary
, and maxillary bones.
Measurements from the anterior end of the snout were taken from the front of the premaxillary
symphysis; those involving the orbit (snout length, orbit diameter and interorbital width) are of the bony orbit; orbit diameter is the horizontal diameter.
These included right alveolar toothrows of the mandible and maxillary, greatest skull length, greatest zygomatic breadth, least interorbital breadth, greatest width of nasals, basal width of rostrum, greatest occipital breadth, and greatest lengths of the premaxillary, maxillary, and palatine bones from along the medial suture as viewed from the ventral perspective (Figure 1).
Significant age variation exists for all characters but premaxillary length.
Dorsal head profile almost straight, premaxillary
pedicel not prominent.
With an admittedly small sample (71 skulls and 63 skins), their diagnoses of what they considered valid taxa were based on pelage color, skull contour (sagittal and occipital crests, bulging or swelling of frontals, depression of frontal-parietal region), nasal shape, and premaxillary