Order PLATYCOPIDA Sars, 1866

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Introduction

Platcyopida are defined by having a large exopod on the second antenna, compared to the very reduced exopod in Podocopida. They also have a large (not reduced) furca with stout claws. Living species are in the family Cytherellidae. There are three Australian species.

Diagnosis

Carapace mostly 1 mm long or less, shape quadrate to ovate. Valves smooth or ornamented with pits, reticulation and ribs. Valve marginal zone with narrow calcified inner lamella with selvage forming accommodation groove in larger valve. Hinge adont, or with single tooth. Valve overlap often strong, usually RV larger than LV. Adductor muscle scar: two vertical rows, each with 5–9 scars, side-by-side, usually with centrally positioned scar at top and bottom. Normal pores simple. Female with expanded posterior cavities for brood care (eggs only). Female with 6 pairs of appendages and caudal ramus. Antennula 7-segmented. Endopod of antenna 3-segmented; exopod 2-segmented. Mandibular branchial plate small, with up to 6 rays; basis bearing filter comb with many long flattened setae. Maxillula with large branchial plate and filter comb of long, flattened setae. Male brush-shaped organ absent. First thoracopod sexually dimorphic: in males clasping organ with 2-segmented endopod; in female endopod reduced to single seta; protopod with large branchial plate. Second thoracopod in male also a clasping organ, with 2-segmented endopod, protopod bearing small branchial plate with 5–7 rays; reduced in female to only branchial plate. Third and fourth thoracopods absent. Male copulatory appendage external, not enclosed by peniferal sheath; Zenker's organ absent. Caudal ramus well developed, lamellar, each ramus with about 10 terminal or marginal claws; separated from male copulatory appendage by at least 3 abdominal segments.

Diagnosis References

Horne, D.J., Cohen, A. & Martens, K. 2002. Taxonomy, morphology and biology of Quaternary and living Ostracoda. Geophysical Monograph 131: 5-36 [32]

History of changes