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Loliolus has six species placed into two subgenera.

Type species.-- Loliolus hardwickei (Gray) [Note: according to Lu et al. (1985), Steenstrup's originally designated type species, L. typus Steenstrup 1856 = Loligo hardwickei Gray 1849].

Containing group: Loliginidae

Introduction

These are generally small squids with heart-shaped fins.

Diagnosis

A loliginid ...

• with short mantle, rounded posteriorly; fins wider than long but without posterior lobes.
• with ventral crest on hectocotylus formed by fusion of the protective membrane with the ventral row of papillae.
• with an Indo-Pacific distribution.

Characteristics

1. Arms
   1. Arm sucker rings with square plate-like teeth on margin.
      image info

      Figure. Oral view of large arm III suckers of L. hardwickei, 33 mm ML, male. The left sucker is from the dorsal series and the right sucker from its pair in the ventral series. Drawings from Lu, et al. (1985).

   2. Hectocotylus:
      1. Ventral crest present, formed by fusion of protective membrane with ventral row of papillae such that original form of conical papillae is completely obscured (see below).
      image info
      image info

      Figure. Top - Aboral-medial view of the hectocotylus of Loliolus (Loliolus) hardwickei showing the crest that reaches the full length of the arm, male, off Madras, India, preserved. Photograph by R. Young. Bottom - Oral-lateral view of the hectocotylus of L. (L.) hardwickei showing the crest, male, 33 mm ML, Indian Ocean south of Calcutta. Drawing from Lu et al. (1985).

2. Tentacles
   1. Tentacular clubs expanded, suckers in four series.
      
      
3. Mantle
   1. Mantle rounded posteriorly; without tail-like elongation.
      
      
4. Fins
   1. Fins extend to posterior tip of mantle.
      image info

      Figure. Dorsal view of L. (L.) hardwickei, 33 mm ML, male. Drawing from Lu, et al. (1985).

5. Photophores
   1. Photophores absent.
      
      
6. Viscera
   1. Eggs small.
   2. Spermatophore cement body short.

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Hectocotylization includes a crest along a portion of the ventral surface of the arm and a modification of part of the dorsal row of suckers into papillae. Modification of the proximal portion of the hectocotylus varies between subgenera. In Loliolus (Loliolus) the modified portion of the hectocotylus occupies the entire length of the arm whereas in Loliolus (Nipponololigo) some proximal suckers are unmodified.

Nomenclature

Steenstrup (1856) erected the genus Loliolus for his new species typus. Lu et al. (1985) showed that L. typus is a junior synonym for Loligo hardwickei Gray, 1849, making the latter species the type for the genus Loliolus.

Because the percentage of the arm hectocotylized is considered to be a cline within this group of species with otherwise similar hectocotyli and arm-sucker dentition, Loliolus and Nipponololigo were combined by Vecchione et al. (1998) into a single genus that, by priority, is named Loliolus.

Discussion of Phylogenetic Relationships

Loliolus was originally erected to include species of small loliginids with heart-shaped fins in which the entire left ventral arm of the males is modified. However, as discussed by Brakoniecki (1986), clines exist in the percentage of the arm hectocotylized within species groups with similar hectocotyli. Thus, this character state is not sufficient for generic status. The presence, though, of a distinctive character, a ventral crest on the hectocotylus formed by fusion of the protective membrane with the ventral row of papillae such that the original form of the conical papillae is completely obscured, indicates a close relationship among these species (Natsukari, 1983).

Distribution

The species in this genus are all found in the Indo-West Pacific.

References

Brakoniecki, T.F. 1986. A Generic Revision of the Family Loliginidae (Cephalopoda; Myopsida) Based Primarily on the Comparative Morphology of the Hectocotylus. Ph.D. Dissertation, University of Miami, Miami, FL, USA. 163 pages.

Lu, C.C., C.F.E. Roper, and R.W. Tait. 1985. A Revision of Loliolus (Cephalopoda; Loliginidae), including L. noctiluca, a new species of squid from Australian waters. Proceedings of the Royal Society of Victoria, 97(2):59-85.

Natsukari, Y. 1983. Taxonomical and morphological studies on the loliginid squids--III. Nipponololigo, a new subgenus of the genus Loligo. Venus, The Japanese Journal of Malacology, 42(4):313-318.

Vecchione, M., T. F. Brakoniecki, Y. Natsukari and R. T. Hanlon. 1998. A provisional generic classification of the family Loliginidae. Smithson. Contr. Zool., 586.

Vecchione, M., E. Shea, S. Bussarawit, F. Anderson, D. Alexeyev, C.-C. Lu, T. Okutani, M. Roeleveld, C. Chotiyaputta, C. Roper, E. Jorgensen and N. Sukramongkol. 2005. Systematics of Indo-West Pacific loliginids. Phuket Mar. Biol. Cent. Res. Bull. 66: 23-26.