Blake et al.—Cretaceous seep asteroid
Etymology.—The species is named for Jamie Brezina, who discovered all but one of the available specimens, made them available for research, and donated them to the collections of the American Museum of Natural History.
Remarks.—Known species of Betelgeusia are generally similar in overall form, expressions of the abactinal, actinal, and, insofar as is known, ambulacral skeletons, including the mouth frame; they differ largely in marginal ossicular form and accessory development. Betelgeusia brezinai n. sp. is most similar to B. exposita, the latter known from a single incomplete specimen exposed in ventral view. The holotype of B. exposita is not significantly distorted or disrupted, and internal morphology is not available. Marginal ossicles of B. brezinai are more robust and fascioles less sharply defined than in B. exposita; although data are limited, actinals appear to be fewer in B. exposita and the first actinal does not overlap onto the adambulacral; the first adambulacral is proportionately smaller in B. exposita. Superomarginal accessories of B. brezinai are granules rather than spinelets as in B. exposita,and although exposure is limited, superomarginals do not appear to be inset in B. exposita. Marginals and proximal actinals of B. orientalis are similar to those of B. exposita rather than like those of B. brezinai, and MAO pair of B. orientalis are com- paratively narrow and keel-like.Overall ossicular formof B. reidi is more delicate than that of B. brezinai, and spines of the former are much elongate and slender whereas those of B. orientalis are intermediate between those of B. reidi and B. exposita.
Superorder Forcipulatacea
Subfamily Pedicellasterinae? Perrier, 1884 Genus indeterminate species indeterminate Fig. 5.14–5.15
Material.—Locality AMNH 3529, one small arm fragment, hypotype AMNH-FI 111853.
Remarks.—In a traditional arrangement of the Forcipulatacea (Spencer and Wright, 1966), the Pedicellasterinae is separated from the Asteriinae by absence of an adoral carina (the proximal-most adambulacrals abutting across the interbrachium immediately distal to the mouth-angle pair to form the ‘adoral carina’), and podial arrangement is biserial at least distally, rather than quadriserial throughout. The molecular phylogeny of Mah and Foltz (2011b) introduced significant changes to
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forcipulate classification, the pedicellasterids separating into a more basal cluster, and a six-armed cluster that was imbedded among more derived forcipulates. In the Pierre Shale fragment, the cross-shaped body wall
ossicles with overlapping articular flanges are typical of Forcipulatacea. The shape of the single available ambulacral (Fig. 5.14), exposed in dorsal aspect, documents an arm that had only two rows of tube feet, a generalized configuration nevertheless typical of pedicellasterids in the traditional sense. Adambulacral form is typical of pedicellasterids, although not diagnostic. Familial assignment is traditional; available data are not sufficient for familial assignment following Mah and Foltz (2011b) or for generic and species assignments.
Diversification of the Paxillosida
The extant Radiasteridae based on morphologic data and represented by Radiaster is assigned to the order Paxillosida (Blake, 1987; Gale, 2011); in the literature, the Paxillosida traditionally has been envisioned as a major subdivision of the extant Asteroidea (Spencer and Wright, 1966), the order including the comparatively familiar fossil and extant Luidia Forbes, 1839 and Astropecten Gray, 1840. The molecular analysis of Mah and Foltz (2011a) recognized paxillosidan affinities for both the second known extant radiasterid genus, Gephyreaster,and Pseudarchaster Sladen, 1889, the latter traditionally considered to be a goniasterid valvatidan rather than a paxillosidan (Spencer and Wright, 1966). Drawing on these results, Radiaster here is aligned with Gephyreaster, and together with Pseudarchaster, the three are accepted as a monophyletic paxillosidan cluster. Mah and Foltz (2011a) argued for a broadly sister-group status between the Paxillosida plus the Notomyotida (monofamilial, Benthopectinidae), and the bulk of the traditional Valvatida including the Goniasteridae plus many extant members of the Spinulosida sensu Spencer and Wright (1966). Goniasterids and Pseudarchaster are widely distributed in modern oceans, and in part because of a comparatively robust construction, goniasterids predominate in the Cretaceous chalk asteroid faunas of Europe. Although a number of Triassic crown-group asteroids are
known, the Paxillosida has not been recorded from pre-Jurassic rocks (Gale, 2011, familial summary, p. 57) whereas Hess (1987, p. 907) found that the paxillosidan astropectinids radi- ated in the Middle Jurassic. Two Jurassic astropectinids have
Figure 5. (1–13) Betelgeusia brezinai n. gen. n. sp. (1) Paratype AMNH-FI 111852, disk in ventral aspect, aligned series of imbricate actinals separating two mouth angle ossicle (MAO) pairs (upper left) from inferomarginal series (far right); compare (10, 11). (2, 3) Paratype AMNH-FI 111825, arm tip in dorsal and ventral aspect; (2) the terminal is large, as is common among paxillosidans (including the Radiasteridae) with attenuated arm tips; (3) arm tip upturned as is common in life, an orientation enabling extension of sensory distal tube feet into the environment; marginals with aligned, transverse accessory pustules; marginals abut spinose adambulacrals. (4–6) Paratype AMNH-FI 111826, marginal series and associated ossicles in dorsal, lateral, and ventral views; (4) ossicular debris including few abactinals and actinals that were displaced dorsally; (5) angular openings at abradial edge of superomarginals suggest pedicellariae openings, these otherwise unknown among radiasterids; (6) inferomarginal pustule configuration and a few remaining accessories; actinals largely disrupted. (7–9) Paratype AMNH-FI 111827; (7) superomarginals and displaced small paxilliform abactinals; (8) both marginal series, lateral surfaces showing fasciolar ridges; (9) inferomarginals above with spinelet pustules; displaced actinals below. (10, 11) Paratype AMNH-FI 111828, actinal and marginal series in ventral and inclined ventral views; the strongly imbricating and aligned actinals are characteristic of radiasterids, here potentially partially displaced taphonomically, but of overall orientation likely similar to those assumed during normal body flexure. (12) Paratype AMNH 111829, dorsal aspect near juncture of arm and disk, compare (1); superomarginal form, inferomarginals extending laterally beyond superomarginals; abactinal form. (13) Paratype AMNH-FI
111830, fragment in ventral aspect, shingled actinal rows (arrows) extend adradially from two inferomarginals. (14, 15) Pedicellasterinae? gen. indet. sp. indet., figured specimen AMNH-FI 111853, two views of the single available fragment; (14) dorsal ossicular views, cross-shaped body-wall ossicles are characteristic of forcipulates; a single ambulacral (arrow) is comparatively large, the figure ‘8’ or wasp-shape indicates a single row of podia rather than offset podial series of the Asteriidae; (15) dominantly ventral ossicular views, adambulacral (arrows) form is consistent with a pedicellasterid assignment. (1–13) Scale bars=1.0mm; (14, 15) scale bars=2.0mm.
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