Archaeoscinidae Barnard 1930

Family ARCHAEOSCINIDAE Barnard, 1930

Diagnosis

Body length less than 10.0 mm, with extreme sexual dimorphism in body shape. Females with spherically inflated pereon because of enlarged pereonites 1–5, slightly longer than deep, more than twice as long as pleon and urosome combined; head immersed in first pereonite; pereonites 6 & 7 and pleon slender. Males with slender pereon (sciniform), equal in length to, or slightly shorter than, pleon and urosome combined; head as long as first pereonite. Pereonites all separate. Coxae separate from pereonites. Antennae 1 of females as long as head and first pereonite combined; of males as long as head and first 1.5–3 pereonites combined; peduncle 3­articulate in females, 2­articulate in males. Antennae 2; length 0.5–0.7x A1. Mandibles with slender palp, length of third article 1.2–2.0x length of first two combined; incisor very narrow; left mandible with lacinia mobilis. Maxillae 1 with slender palp, comparatively narrow outer lobe and short inner lobe. Maxillae 2 with relatively slender lobes, the inner slightly shorter than the outer one. Maxilliped with oval, unarmed outer lobes; inner lobes about 0.2–0.8x length of outer, fused proximally, separate distally. Gnathopods 1 & 2 simple; carpus not especially broadened distally; dactylus inserted subterminally in G1, sometimes also in G2. Pereopods 3–7 simple. Pereopods 5–7 without (Archaeosina) or with retractile dactyls which may be hooded (Paralanceola). Urosomite 2–3 with partial suture ventrally. Uropods slender, with articulated exopods and endopods. Telson shorter than peduncle of U3, triangular with rounded or pointed apex. Gills on pereonites 3–6. Oostegites on pereonites 2–5.

Two genera: Archaeoscina and Paralanceola.

Remarks

In the above diagnosis, reference to female characters is restricted to Archaeoscina because females of Paralanceola are not known.

Woltereck (1909) attempted to rationalise the systematics of some of the families and genera now included in the infraorder Physosomata and provisionally included the genera Archaeoscina Stebbing, 1904, Micromimonectes Woltereck, 1906, Mimonecteola Woltereck, 1909 and Microphasma Woltereck, 1909 in the family Pygmaeidae. However, because this group did not include the genus Pygmaeus, from which the family name could be derived, Barnard (1930) proposed the family name Archaeoscinidae to accommodate this group of genera, derived from the oldest available generic name in the group, Archaeoscina.

Stephensen and Pirlot (1931), in a study of this group and related genera, proposed the family Microphasmidae for Microphasma and noted that Archaeoscina was only known from males and Micromimonectes only from adult females. Subsequently, Pirlot (1939), followed by Vinogradov (1956), synonymised Micromimonectes with Archaeoscina, and when Vinogradov (1957) also removed Mimonecteola to the family Microphasmidae, the family Archaeoscinidae consisted of only one genus, Archaeoscina.

Paralanceola Barnard, 1930 is known only by the unique type of P. anomala, which Barnard tentatively placed in the family Lanceolidae, based on the hooded, retractile dactyls of pereopods 5–7. However, this character is not unique to this family and is also found in the Chuneolidae, Proscinidae (Mimoscina) and Scinidae (Ctenoscina). Pirlot (1939) suggested that Paralanceola might belong with Archaeoscina and Vinogradov et al. (1982) finally concluded that this genus is best placed in the family Archaeoscinidae, based on the structure of the mouthparts, particularly the narrow mandibular incisor, mandibular palp and also the morphology of the antennae. This is supported by the present study which includes a re­examination of the remains of the unique type of P. anomala and five additional specimens attributed to this genus.

In all specimens of this family, that I have examined, I found a partial suture between urosomites 2 and 3, but only ventrally. It is present in all other members of the Physosomata examined and I have also found it in the family Vibiliidae. This character has not been recorded for the Physosomata previously and may be a remnant of a primitive lineage to the Gammaridea.