Freyastera Downey, 1986

Genus Freyastera Downey, 1986 View in CoL

Type species.

Freyella sexradiata Perrier, 1885 .

Diagnosis.

Arms six. Papulae absent. One pair of gonads on each arm. Disk very small, arms extremely long and slender. The first pair of inferomarginal plates appears later on arm, not in contact with the odontophore. Inferomarginal plates and lateral spines generally correspond to every adambulacral plate beyond genital area. Abactinal arm in genital region covered with pavement of spinate plates. Adambulacral plates elongated.

Remarks.

Freyastera and Freyella were redefined by Zhang et al. (2024), with the number of arms and the arrangement of inferomarginal plates as key diagnostic characters. The genus Freyastera currently contains seven species ( Mah 2025): Freyastera basketa Zhang et al., 2019 ; Freyastera delicata Zhang et al., 2019 ; Freyastera digitata McKnight, 2006 ; Freyastera mexicana (A. H. Clark 1939) ; Freyastera mortenseni ( Madsen 1956) ; Freyastera sexradiata ( Perrier 1885) ; and Freyastera tuberculata ( Sladen 1889) . A new species, Freyastera jiaolongi sp. nov., is described in the present study. Two species previously belonged to Freyella , F. giardi Koehler, 1907 , and F. loricata Korovchinsky & Galkin, 1984 , are reassigned here to Freyastera as new species combinations. The genus is hence composed of 10 species in total. Furthermore, seven unnamed species are included in the molecular analyses: Freyastera sp. 2 , Freyastera sp. 3 , Freyastera sp. 5 , Freyastera sp. 6 , Freyastera sp. 7 , Freyastera sp. Yap, and Freyastera cf. tuberculata . Among them, precise identification of Freyastera sp. 2 , Freyastera sp. 7 , and Freyastera cf. tuberculata was not feasible, as they were morphologically similar to Freyastera tuberculata , Freyastera giardi comb. nov., and Freyastera loricata comb. nov. (see Freyastera tuberculata species complex). Freyastera sp. Yap ( RSIOAST 0041 ) was reported based on one broken arm ( Zhang et al. 2019), whereas specimens of Freyastera sp. 3 ( RSIOAST 0057 ), Freyastera sp. 5 ( RSIOAST 0107 , RSIOAST 0116 , RSIOAST 0138 ) (Fig. 14 F – G View Figure 14 ), and Freyastera sp. 6 ( RSIOAST 0124 , RSIOAST 0125 ) (Fig. 14 H, I View Figure 14 ) were severely damaged during collection, with only arm fragments available, or kept frozen after collection, which hinders proper morphological identification and description. However, genetic information from these specimens showed high diversity, and species delimitation tools set them as seven species units, distinguishable from other known species with genetic data available. They were therefore included in the present study to discuss the phylogeny and diversity of Freyastera . Proper definition and description of these species units need to be done with more specimens in good condition in the future.

The following systematic accounts include a key, diagnoses, illustrations, and remarks on each known Freyastera species or species complex based on specimens or photos examined, except one species, Freyastera digitata McKnight, 2006 . F. digitata was described to have an inferomarginal plate corresponding to every 2–3 adambulacral plates ( McKnight 2006), but the holotype was broken with only 22 mm of arm left, thus the arrangement of inferomarginal plates beyond the genital area is largely unknown. This species greatly resembles Freyella benthophila in the absence of a furrow spine and abactinal plates with several short spinelets. The taxonomic position of F. digitata needs to be re-evaluated with further examination of the holotype and other complete specimens. It is thus not included in the diagnostic key of the genus for the time being.