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Journal of Paleontology 92(2):196–206


been recognized, the relatively species-rich Pentasteria Valette, 1929 and monospecific Advenaster Hess, 1955. Pentasteria has been discussed by a number of authors, most notably by H. Hess, whose many papers provide perspective on both this genus and Advenaster (Hess, 1955, 1960a, 1960b, 1968, 1970, 1972, 1987; Enay and Hess, 1970). Another Jurassic genus, Archastropecten Hess, 1955, was later relegated to a subgeneric status within Pentasteria (Hess, 1960a). Indiaster, sourced from Pachham Island (Kutch, Gujarat,


India), was based on two specimens and a fragment thought derived from one of the larger specimens. The specimens unfortunately “are not traceable” and “probably misplaced” (personal communication, D. Srivastava, 2009), and available morphologic data are limited. Published photographs of Rao show both surfaces but only a single surface of each specimen, that in ventral aspect later reproduced by Spencer and Wright (1966, fig. 56.2). Five ossicular outline drawings accompanied the original photographs. The specimens appear abraded, limi- ting potential information. Specimen sizes appear to approxi- mate those of Betelgeusia brezinai. When described, Indiaster was assigned to the Goniasteridae whereas here, following Blake and Reboul (2011), it is transferred to the Radiasteridae. Betelgeusia currently is known only from Cretaceous


occurrences. The type species, B. reidi, is represented by many specimens from several formations of the complex middle Cretaceous (Albian, Cenomanian) of Texas; B. exposita is known from a single incomplete Late Cretaceous (Maastrichtian) specimen from Europe; and B. orientalis is known from numerous Early Cretaceous (Barremian) speci- mens from Morocco. Overall form and ossicular morphologies of Mesozoic


abutted marginal series would have defined the ambitus and separated an abactinal field of uniform, relatively robust paxilliform abactinals from the more or less enlarged field of actinals, these abutted and aligned in series. Except for


fossils together with those of extant astropectinids and pseu- darchasterids (Fisher, 1911, 1919; Hess, 1955, 1968, 1972, 1987; Blake and Jagt, 2005; Blake and Reboul, 2011) suggest a hypothetical configuration for a primordial paxillosidan species, although no species is considered adequately documented as to serve as an outgroup exemplar for phylogenetic analyses. The posited basal paxillosidan species would have been low-arched with a relatively large disk, broadly curved interbrachia, and triangular, comparatively abruptly tapering arms. A differ- entiated dorsal midarm series of abactinals together with a differentiated ring or primary circlet of dorsal disk ossicles are typical of most crown-group asteroid clades, but lacking from radiasterids and astropectinids, and generally only weakly differentiated in Pseudarchaster. Interpretation of carinal or primary circlet presence in fossils and even some modern specimens can be difficult because specimen symmetry and sediment compaction can elevate the midarm series as to suggest carinals, and the eye can interpret disk ossicles as con- centric in arrangement, suggesting a circlet. Accepting the Paxillosida as a sister group of a part of the terminologically traditional Valvatida (Mah and Foltz, 2011a), abactinal differ- entiation was likely plesiomorphic within early paxillosidans, and retained in Pseudarchaster. In the hypothetical basal paxillosidan, two robust, similar,


B. reidi, available data for ambulacral and adambulacral internal morphology of Mesozoic radiasterids are limited, but adambu- lacrals likely were rectangular in the basal paxillosidan and bore well-developed spines; granules or small spinelets were common on other ossicles. If pedicellariae were differentiated, blades were simple and spinelet-like. The strong but generically distinctive marginal


differentiation seen in Astropecten and Luidia did not occur in Jurassic Indiaster or Pentasteria whereas complex marginals, ambulacrals, and delicate paxillae suggestive of Astropecten occur in middle Cretaceous B. reidi but not in younger Cretac- eous B. brezinai (Blake and Reid, 1998, fig. 8.17; Fig. 5.7 herein), the latter then an inferred more stemward configuration surviving in similar form today not only in Pseudarchaster but also in some astropectinids (Plutonaster Sladen, 1889; Tethya- ster Sladen, 1889), goniasterids (Mediaster Stimpson, 1857; Ceramaster Verrill, 1899), and other valvatidan families (Ganeriidae, Odontasteridae). Expressions of B. reidi might be either basal among those paxillosidans that led to Astropecten and Luidia, or homoplastic. Strongly imbricate actinals of Betelgeusia (Fig. 5.10, 5.11) and Radiaster are not known among the Jurassic paxillosidans. Expression of the termini of the tube feet might have been


emergent within early paxillosidans, but fossilized tube feet are unavailable. Traditionally, termini of the tube feet of all taxa assigned to the Paxillosida are pointed whereas in the remainder of the crown-group Asteroidea, termini are expanded and suckered or disk-like; expressions, however, likely were more complex than the simple two-fold terminology would suggest (Vickery and McClintock, 2000; Santos et al., 2005). Unlike other paxillosidans, Gephyreaster, Radiaster, and Pseudarchaster have disk-like tube feet. In separating Radiaster (=Mimaster Sladen, 1882) from the astropectinids Plutonaster and Leptychaster Smith, 1876, the essential difference in the structure of the tube feet was thought to be “a more important barrier [to combining taxa] than is commonly supposed,” the large sucking disks of Pseudarchaster found to ally this genus with Radiaster and Gephyreaster (Fisher, 1911, p. 175). It was, however, also pointed out, “In passing,” that presence of “conical tube feet with a little button (as in the Astropectinidae) at the tip” occur in Radiaster cognatus (Fisher, 1911, p. 175). However, as discussed in some detail by Clark (1962, p. 11), even familial assignment of this species and genus (under Mimastrella Fisher, 1916) is unclear, Clark including Mimastrella in the Astropectinidae but also finding aspects that “strongly suggest an affinity with the family Solasteridae.” Regardless of ultimate species disposition, complimenting Fisher’s observation on tube feet of ‘R. cognatus,’ occurrence of expanded termini were reported in the early ontogeny of a species of Astropecten (Oguro et al., 1976). Modern expressions together with the phylogeny of Mah and Foltz (2011a) and the complexities noted by Vickery and McClintock (2000) and Santos et al. (2005) suggest an emergent status for tube foot differentiation in early paxillosidans, rather than a single simple ordinal-level apomorphy. Actinal ossicular alignment immediately adjacent to the


mouth frame of B. brezinai appears to have been somewhat irregular, reminiscent of corresponding expressions in both Triassic Trichasteropsis Eck, 1879 (Blake and Hagdorn, 2003)


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