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Hysteraster
Taxonomy
Hysteraster was named by McNamara (1992) [Sepkoski's age data: T Mi-l-u Sepkoski's reference number: 1242]. Its type is Hysteraster paragrapsimus.
It was assigned to Brissidae by McNamara (1992); and to Spatangoida by Sepkoski (2002).
It was assigned to Brissidae by McNamara (1992); and to Spatangoida by Sepkoski (2002).
Species
H. paragrapsimus (type species)
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If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.
Diagnosis
| Reference | Diagnosis | |
|---|---|---|
| K. J. McNamara 1992 | Test moderately large, relatively narrow and with
slight anterior notch. Apical system set well anterior ofcentre; deeplydepressedinfemales.Petalsshort, broad and deeply depressed in females, only slightly depressed in males; do not extend to peripetalous fasciole; pore pairs very reduced in size in anterior rows of anterior petals; in all petals pore pairs absent in vicinity of apical system. Apical system ethmolytic with fourgonopores. Peripetalous andsubanal fascioles present. Aboral tubercles much larger within peripetalous fasciole than outside of it; those in interambulacra 2b and 3a are the largest and most sparsely distributed. Peristome subcentral. Plastron small, with prominent posterior keel. Periplastronal area wide. |