Ordovician Petraster Billings, 1858 (Asteroidea: Echinodermata) and early asteroid skeletal differentiation Author Blake, Daniel B. Departement of Earth Sciences and Environmental Change, University of Illinois, 3081 NHB, 1301 West Green Street, 61801 Urbana, IL (United States) dblake@illinois.edu Author Lefebvre, Bertrand Université Claude Bernard Lyon 1, ENSL, CNRS, LGL-TPE, 43 boulevard du 11 Novembre, F- 69622 Villeurbanne (France) bertrand.lefebvre@univ-lyon1.fr text Comptes Rendus Palevol 2024 2024-05-29 23 17 217 239 http://dx.doi.org/10.5852/cr-palevol2024v23a17 journal article 305499 10.5852/cr-palevol2024v23a17 8fc26efa-4ffb-4993-bf58-7fb38916b793 1777-571X 11387624 urn:lsid:zoobank.org:pub:C0E27E25-6719-40FD-A2B8-829B484D6C13 Petraster ? ramseyensis ( Hicks, 1873 ) ( Fig. 1B ) Palasterina ramseyensis Hicks, 1873: 51 , pl. 4, figs 21-23. Palasterina ? ramseyensis – Schuchert 1915: 154 . Uranaster ramseyensis – Spencer 1918: 109 , pl. 4, figs 1-4; text figs 64-66. — Owen 1965: 567 . Petraster ramseyensis – Blake 2018: 24 . “ Petraster ” ramseyensis – Blake 2018 : pl. 4, figs 3, 4. DIAGNOSIS . — Petraster ? with clearly differentiated carinal and adradial series, the latter rectangular and variously oriented, oblique to carinals. MATERIAL EXAMINED . — Two specimens in the collections of the Manchester Museum; London NHM casts reviewed. Spencer (1918: 109) proposed the syntype Manchester L. 11037 = NHM E.13705 as “holotype”. TYPE LOCALITY AND HORIZON . — Ramsey Island , Wales ; early Arenig (early Floian). DESCRIPTION Petraster ? size uncertain, interpretation based on distorted available specimens, R c. 15 mm . Aboral disk unknown; arm abactinals robust, clearly differentiated into series. Carinals elliptical, subconical, appear to have a small accessory pustule. Adradialia appearing to be in a single series on each side of carinals series; adradials irregular, rectangular, oriented both nearly parallel as well as oblique to arm axis; series possibly not reaching arm tips. Madreporite? on aboral disk. Superomarginals of arms similar in overall appearance to carinals but larger, arrangement and orientation appearing somewhat irregular. Intermarginals unknown. Inferomarginals incompletely known, robust, in aboral aspect appearing rectangular in outline on arms, more nearly equidimensional in oral aspect; any enlargement of inferomarginals on disk unclear. One incomplete interbrachium suggests presence of axillary nearly reaching disk margin; actinal field small. Axials appearing approximately bilateral at transverse ridge, abutted, not overlapping.Mouth frame unknown.Adaxials equidimensional. REMARKS At the time of description, ramseyensis was assigned to Palasterina , the species subsequently transferred to Uranaster based on perceived strong similarities with ‘ Uranaster ’ kinahani ( Spencer 1918 ) . Uranaster was synonymized with Petraster ( Spencer & Wright 1966 ) , but ramseyensis later was left unassigned at the generic level ( Blake 2018 ). The Spencer (1918) generic interpretation is tentatively followed here, in part based on some aboral similarities with P . caidramiensis n. sp. and of the distal arm interval of P. crozonensis .