Stichopilida Haeckel, 1882: 439 [as a tribe]; Haeckel, 1887: 1435, 1436 [as a subfamily].
Artopilida Haeckel, 1882: 437 [as a tribe].
Stichopilinae [sic] – Campbell & Clark 1944b: 36 (= Stichopiliinae). — Frizzell & Middour 1951: 31. — Chediya 1959: 226.
Stichopiliidae – Frizzell & Middour 1951: 31. — Petrushevskaya 1986: 133.
Triacartidae Campbell, 1954: D136.
Triacartinae Campbell, 1954: D136.
TYPE GENUS. — Stichopilium Haeckel, 1882: 439 [type species by subsequent designation (Frizzell & Middour 1951: 32): Stichopilium bicorne Haeckel, 1887: 1437].
INCLUDED GENERA. — Artopilium Haeckel, 1882: 437 (= Trictenartus with the same type species). — Ectotoxon Sugiyama, 1994: 6. — Lophoconus Haeckel, 1887: 1403. — Stichopilium Haeckel, 1882: 439 (= Triacartus with the same type species).
HOMONYM. — Pterocorythium Haeckel, 1887 (= Artopilium, synonymized by Campbell 1954: D136) nec Haeckel, 1882.
DIAGNOSIS. — Stichopiliidae consist of two or three segments, with or without discrete wings. An additional undulated extension might be present in some members. The shell wall is thin, fragile and consists of a very fine grid-like structure. Two significant apical horns with a similar development and three wings are observed. Two of the three wings extend parallelly to these two significant horns and the remaining wing extends vertically. The cephalic initial spicular system consists of MB, A-, V-, D- and double L-rods. The double l-rod and cephalic basal ring absent. These rods are so robust and straight that MB, A- and V-rods are well visible under light microscopy. The MB is generally parallel to the segment boundary. The small endoplasm is located in the cephalon-thoracic part. A single, very long pseudopodium (axial projection) extends more than eight times the total length of the shell. A bundle of pseudopodia forms a cone shape. No algal symbionts are reported.
STRATIGRAPHIC OCCURRENCE. — Late Oligocene-Living.
REMARKS
The cephalic initial spicular system was illustrated for Artopilium (Nishimura 1990: figs 18.1, 18.2; Sugiyama 1994: pl. 3, fig. 5), Ectotoxon (Sugiyama 1994: pl. 3, fig. 4, pl. 4, figs 1, 2) and Stichopilium (Nishimura & Yamauchi 1984: pl. 35, fig. 14; Sugiyama 1998: pl. 6, fig. 2). All genera belonging to the Stichopiliidae were not treated by De Wever et al. (2001). The arches of the cephalic initial spicular system seem to be different at the genus or species level. The Mesozoic families Foremanellinidae Dumitrica 1982a and Cuniculiformidae De Wever 1982a are similar to the Stichopiliidae except for the presence of double l-rods in the Mesozoic families. These families both have two significant apical horns related to the A- and V-rods and also share a similarity in the segmentation or undulation patterns associated with Stichopiliidae. If these families are phylogenetically connected to the Stichopiliidae, fossil records from the Berriasian (Early Cretaceous) to the early Oligocene are missing. A “Living” image has been illustrated for “ Dictyocodon ” prometheus by Sugiyama et al. (2008: figs 2, 8) but no appropriate genus name currently exists for this species. The evolution of the Stichopiliidae has not been studied, probably due to many undescribed species (e.g., Lazarus 1992: pl. 9, figs 9-17).
VALIDITY OF GENERA
Artopilium
Campbell (1954: D136) incorrectly validated Trictenartus as an objective synonym of Artopilium. Nigrini (pers. comm.) left notes indicating that Campbell (1954: D136) had designated Artopilium elegans Haeckel, 1887 as the type species of Trictenartus solely by the inference of Artopilium. Therefore, we consider the type species designation of Artopilium to date from Chediya (1959: 226).
Stichopilium
Campbell (1954: D136) validated Triacartus as an objective synonym of Stichopilium. However, Frizzell & Middour (1951: 31-32) had already validated Stichopilium, but not Triacartus. Therefore, following the first reviser rule, Stichopilium is the valid genus name.