. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. Marine Hatchetfishes • Baud 81. 30 SL so Figure 62. Regression of lower jaw length (JL) on standard length (SL) in S. diaphana (A) and S. pseudobscura (B) from the Tropical Atlantic. ridged folds; die posterior section diin walled and extensible, six to ten pyloric caecae, short straight intestine, and a rel- atively large well-developed liver. Gonads, when mature, lie horizontally and laterally in the body cavity; cavity lined with pig- mented membrane; nepliritic tissue is not as well developed as in other genera. S
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. Marine Hatchetfishes • Baud 81. 30 SL so Figure 62. Regression of lower jaw length (JL) on standard length (SL) in S. diaphana (A) and S. pseudobscura (B) from the Tropical Atlantic. ridged folds; die posterior section diin walled and extensible, six to ten pyloric caecae, short straight intestine, and a rel- atively large well-developed liver. Gonads, when mature, lie horizontally and laterally in the body cavity; cavity lined with pig- mented membrane; nepliritic tissue is not as well developed as in other genera. Species complexes: As with Arfiyropele- ciis, there has been considerable radiation within the genus. There are three distinct species complexes, two closely related. The third complex, P. spinosiis, is quite distinct. The latter appears more primiti\e in terms of axial and caudal skeleton characteristics. The P. spinosws complex differs from the other two groups as follows: greater de- velopment of the post-temporal spine complex; otoliths (Weitzman, personal con- versation); four hypural elements in the upper caudal lobe; serrate lower jaw mar- gin; spine-bearing abdominal keel plates; the second and tliird pretenninal neural spines wedge shaped; extension of the cleithrum below the pectoral relati\ely more broadened; and the anal pterygio- phore gap is reduced. Within the P. spinosus complex there is a further dichotomy. P. nuttingi, P. oJiiohis, and P. indicus with peculiar reductions in post-temporal spine characteristics, fomi one group; P. spinosus, P. sterope, and P. tridentifer with a well-developed, post- temporal complex, fonn the other. The P. asteroides and P. htenwtus spe- cies complexes are more closely related. They differ primarily in post-temporal spine characteristics, body shape and size, photophore number and pattern, and den- tition. Both complexes have similar otoliths and resemble each other osteologically. The species P. laternatiis—P. omphiis. Pleas
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