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Authors who wish to publish figures that require costly special paper or color reproduction must make prior arrangements with the Scientific Editor. Page Proofs: Fieldiana employs a two-step correction system. The corresponding author will normally receive a copy of the edited manuscript on which deletions, additions, and changes can be made and queries answered. Only one set of page proofs will be sent. All desired corrections of type must be made on the single set of page proofs. Changes in page proofs (as opposed to corrections) are very expensive. Author-generated changes in page proofs can only be made if the author agrees in advance to pay for them. THIS PUBLICATION IS PRINTED ON ACID-FREE PAPER. | GEOLOGY LIBRARY FIELDIANA Geology NEW SERIES, NO. 29 Revised Phylogeny and Functional Interpretation of the Edrioasteroidea Based on New Taxa from the Early and Middle Ordovician of Western Utah Thomas E. Guensburg Research Associate Department of Geology Field Museum of Natural History Roosevelt Road at Lake Shore Drive Chicago, Illinois 60605-2496 Physical Science Division Rock Valley College Rockford, Illinois 61 1 14 James Sprinkle Department of Geological Sciences University of Texas Austin, Texas 78712 Accepted May 27, 1994 Published December 30, 1994 Publication 1463 PUBLISHED BY FIELD MUSEUM OF NATURAL HISTORY © 1994 Field Museum of Natural History Library of Congress Catalog Card Number: 94-61793 ISSN 0096-2651 PRINTED IN THE UNITED STATES OF AMERICA Table of Contents Abstract 1 Introduction 1 Geologic and Stratigraphic Setting and Paleoenvironments 2 Edrioasteroid Phylogeny 3 Function and Evolution 10 Revised Classification 12 Systematic Paleontology 13 Acknowledgments 38 Literature Cited 38 Appendix 42 List of Illustrations 1 . Data matrix for the edrioasteroid parsi- mony analysis 4 2. Cladograms generated by the edrioaster- oid parsimony analysis 5 3. Comparison of floor plate arrangement and morphology between Stromatocys- tites pentangularis and "5." walcotti .... 7 4. Paredriophns elongatus, n. gen. and sp. . 15 5. Paredriophus elongatus, n. gen. and sp., plating arrangement 16 6. Lateral reconstructed view of Paredrio- phus elongatus, n. gen. and sp 17 7. Edrioasteroid spp. indet 19 8. Lampteroblastus hintzei, n. gen. and sp., and Deltadiscus superbus, n. gen. and sp. . 23 9. Lampteroblastus hintzei, n. gen. and sp. . . 24 10. Deltadiscus superbus, n. gen. and sp. ... 26 1 1. Archaepyrgus anitae, n. gen. and sp 30 12. Archaepyrgus anitae, n. gen. and sp., and Pyrgocystis sp 31 13. Ambulacral morphology of Archaepyr- gus anitae, n. gen. and sp 32 1 4. Reconstructed ambulacral segment of Archaepyrgus anitae, n. gen. and sp 33 15. Reconstructed oral view of Archaepyr- gus anitae, n. gen. and sp 34 16. Reconstruction of Archaepyrgus anitae, n. gen. and sp 35 17. Fanulodiscus crystalensis, n. gen. and sp., Archaepyrgus anitae, n. gen. and sp., Cyathocystis sp., and Pyrgocystis sp 36 18. Oral surface of Fanulodiscus crystalen- sis, n. gen. and sp 37 List of Tables 1 . Characters used in the cladistic analysis of edrioasteroids 6 Back cover: Lampteroblastus hintzei, n. gen. and sp. Revised Phylogeny and Functional Interpretation of the Edrioasteroidea Based on New Taxa from the Early and Middle Ordovician of Western Utah Thomas E. Guensburg James Sprinkle Abstract Five new edrioasteroid genera from the Early and Middle Ordovician of western Utah greatly enlarge the record of this scarce echinoderm class during its early diversification. Data from a diversity of taxa were used to generate a new phylogeny and classification of the edrioasteroids. New and reinterpreted morphology, particularly for the aboral surface, is introduced. Forty- two characters were scored for 15 taxa and subjected to a PAUP 3.0 parsimony analysis. This analysis identified two major edrioasteroid clades with subsequent subbranchings. One major clade is the isorophids, whose ancestry can be traced to the Early Cambrian; the second major clade includes edrioasterids and the former class Edrioblastoidea, dating to the Middle Cam- brian. Edrioblastoids, rhenopyrgids, and cyathocystids mapped as specialized branches of the edrioasterid clade, while pyrgocystinids mapped as highly derived lebetodiscid isorophids. The cladistic analysis supported our hypothesis for analogous thecal elongation structures among edrioasterids and isorophids. The fauna contains the edrioasterid Paredriophus elongatus, n. gen. and sp., the edrioblastoid Lampteroblastus hintzei, n. gen. and sp., the agelacrinitid Deltadiscus superbus, n. gen. and sp., and the pyrgocystinid lebetodiscids Archaepyrgus anitae, n. gen. and sp., and Fanulodiscus crystalensis, n. gen. and sp. Several unassigned edrioasterids are also described that provide the first information concerning edrioasterid ontogeny. All are more similar to Middle Ordovician relatives than to those of the Middle to Late Cambrian, even though the faunas are approximately equally spaced by age. The new edrioasteroids adhered to firm substrates, including hardgrounds, mounds, or bioclastic debris. Lampteroblastus has an elongate bud-shaped theca with short ambulacra and triangular deltoids that resemble and could be homologous with those of cyath- ocystid edrioasteroids. Thecal plates of Lampteroblastus also have heavy ridges reminiscent of certain camerate crinoids. Archaepyrgus, n. gen., and Fanulodiscus, n. gen., provide the first detailed pyrgocystinid morphology; unique aspects of their construction include the presence of lateral hood plates and loss of ambulacral floor plates. Deltadiscus has extremely narrow ambulacra and a short elongation zone. Introduction Edrioasteroids are sparsely and sporadically dis- tributed throughout their stratigraphic range. Few- er than 60 genera are known worldwide, even though their history spans over 300 million years, from the Early Cambrian to the Late Pennsylva- nian. Such taphonomic and ecologic factors as the need for rapid, intact burial and the availability of suitable attachment sites naturally contributed to the sparse record of these complex multielement fossils. Edrioasteroids typically inhabited firm or hard substrates, where they lived in concentrations of many individuals representing just one to a few species (see Bell, 1 980; Kammer et al., 1 987; Mey- er, 1990; Smith, 1983; others). These would seem to be best viewed as low-diversity survival strat- egies (Sprinkle & Bell, 1978). FIELDIANA: GEOLOGY, N.S., NO. 29, DECEMBER 30, 1994, PP. 1^*3 Edrioasteroids were among the first echino- derms to have diversified during the Early Cam- brian metazoan radiation. The earliest taxa have been cited as the stem group to extant classes, particularly the asterozoans (Bather, 1915b; Paul & Smith, 1984; Smith, 1984, 1988; Smith & Jell, 1990), as well as lying near the base of both blas- tozoan and later edrioasteroid radiations (Derst- ler, 1981; Paul & Smith, 1984). Unlike the fossil record of most other Paleozoic echinoderms, the edrioasteroid fossil record includes a variety of Cambrian as well as later Paleozoic taxa. Knowledge of edrioasteroids has advanced con- siderably in recent years, and the contributions of Bruce Bell and Andrew Smith are most significant. Bell (1976a) published the definitive monograph on North American edrioasteroids that for the first time clarified many features of internal and ex- ternal skeletal construction and implemented con- sistent morphologic terminology. Revised descrip- tions and exhaustive systematics are provided for most Middle to Late Paleozoic isorophids and ed- rioasterids. Bell (1976a,b) also contributed sub- stantially to our understanding of edrioasteroid ontogeny and its bearing on phylogeny. The works of Smith and co-authors (Paul & Smith, 1984; Smith, 1984, 1985, 1988; Smith & Arbizu, 1987; Smith & Jell, 1990) in many ways complement those of Bell, stressing (although not limited to) Cambrian genera and lesser-known edrioasteroid groups. These studies also include the first cladistic treatment of all major clades within the edrioas- teroids and discussions of their relationships to other echinoderms. Although we disagree with some findings, these publications established a ba- sis for comparisons with our analyses. We describe five new genera and species of ed- rioasteroids from Early to Middle Ordovician rocks from the classic Ibex area of western Utah. Four named species and two undesignated taxa are from the Early Ordovician and represent the first large collection of edrioasteroids of this age. They rep- resent the hard-won products of field work con- ducted over four summers by the authors and their assistants. A Middle Ordovician occurrence was discovered by a field party from Brigham Young University while measuring a section in the area. In addition to formal descriptions, excellent in- place preservation of the fossils has enabled de- tailed life mode and paleoecologic assessments. Widely divergent clades within the edrioasteroids are represented in the Ibex fauna, including one isorophid, multiple edrioasterids, two pyrgocys- tids, and one edrioblastoid. This relatively diverse assemblage from an underrepresented part of the section served as an impetus for a revised com- prehensive phylogeny of the class Edrioasteroidea based on cladistic analysis and reinterpretation of functional morphology. We collected edrioasteroids from several local- ities on or more commonly near published strati- graphic sections (see Hintze, 1973). Close corre- lation to measured sections was usually possible by sighting along strike using a Brunton compass. Good exposure with distinctive beds, low-angle dips, and few faults made this process relatively easy. In some cases where exposure was discon- tinuous, correlations were checked by measuring up- or down-section to distinctive stratigraphic horizons and by noting associated fossils. Detailed facies, stratigraphic, and locality data accompany each taxon described below. Specimens described here are deposited in the type collection at the Field Museum of Natural History (fmnh), Chicago, Illinois, indicated by the prefix pe, and in the United States National Mu- seum, Washington, D.C., indicated by the prefix usnm. These specimens were prepared for study by cleaning with needles under a binocular micro- scope, and then were photographed with a thin coating of ammonium chloride sublimate, or un- der water. Geologic and Stratigraphic Setting and Paleoenvironments The Ibex area is approximately 97 km (60 mi) southwest of the town of Delta, Millard County, Utah, in the eastern portion of the Great Basin. Lower Paleozoic rocks are superbly exposed there in the House and Confusion ranges. The Lower to Middle Ordovician section is a thick depositional sequence of fossiliferous shallow- water carbonates and shales. An excellent stratigraphic and bio- stratigraphic framework has been established by Hintze (1951, 1952, 1973, 1987), Braithwaite (1976), Ethington and Clark (1981), Ross et al. (1982), Ross and Ethington (1991), and others. Conodont and trilobite zonations have proved most useful for age correlation with strata beyond the Ibex area. Associated biostratigraphically im- portant zonations are reported with occurrence in- formation below. Nearly all of the edrioasteroids were collected from four horizons in the Lower FIELDIANA: GEOLOGY Ordovician Fillmore Formation (see Sprinkle & Guensburg, 1993). This unit is wholly contained within the Ibexian Series, and it correlates with the Late Tremadocian through the Middle Arenig stages of British usage (Hintze, 1973, 1979). One edrioasteroid species occurs in the overlying Leh- man Formation of the Whiterockian Series, and it correlates with the Llanvirnian Stage of Britain (see Ross & Ethington, 1991). The Fillmore Formation is a 550-m-thick se- quence of limestones and lesser amounts of shales interpreted to have formed on a shallow tropical ramp of the Cordilleran passive margin (Hintze, 1973; Ross et al., 1991). It has been subdivided into six informal lithostratigraphic members, each characterized by a distinctive weathering style (Hintze, 1973). Clear cyclical stacking of lithofa- cies is present in this section (Hintze, 1973; Da- tillo, 1993; pers. obs.). Most Fillmore edrioaster- oids occur in close association with coarse-grained limestones and sponge-algal mounds, both of which accumulated in shallow agitated water (Church, 1974; Datillo, 1993). Coarse-grained strata in- clude well-sorted grainstones, often developed into megaripples, and abundant intraformational con- glomerates; both are interpreted to have been storm-generated (Datillo, 1993: Guensburg & Sprinkle, 1992). Pyrgocystinids were associated with fine-grained bioclastic limestones (wacke- stones) except for one specimen found on an in- traformational conglomerate. In several cases, ed- rioasteroids remain attached to firm or hard substrates such as hardgrounds (former lithified seafloors) developed on the grainstones, intrafor- mational conglomerates, or mounds, or to bio- clasts such as cephalopod conchs that lay on soft, fine-grained seafloors. The Lehman Formation is an approximately 65- m-thick sequence of limestone together with lesser amounts of quartzarenite (Hintze, 1 973). This unit was not specifically studied by us; however, the single edrioasteroid-bearing slab from this unit provided to us for study is an intraformational conglomerate. The attachment mode of the ed- rioasteroids and staining of the slab surface indi- cate that this was also a hardground. Detailed de- scriptions of occurrences are provided for each taxon described below. Attachment of these edrioasteroids to firm or hard substrates typifies the class as a whole. Di- versification of edrioasteroids and other echino- derms during the Early Ordovician has been at- tributed to the widespread availability of habit- able sites (Guensburg & Sprinkle, 1992). Edrioasteroid Phylogeny This revised phylogeny of the edrioasteroids contains a cladistic analysis with discussion. Con- clusions differ from those of previous authors pri- marily in (a) the placement of pyrgocystinids, for which we also introduce new morphologic ter- minology, and (b) the interpretation of homology and analogy for the aboral surface and thecal elon- gation morphology. Differing usages of terminol- ogy among various authors complicate the second point, and we provide clarification where needed. We discuss several smaller points of contention regarding other aspects of edrioasteroid morphol- ogy, as well. We include in this study only those groups traditionally assigned to edrioasteroids and edrioblastoids. Among the data is the first com- prehensive set for pyrgocystinids. Relationships of the edrioblastoids to other echinoderm classes have long been debated. Bas- sler (1935) classified them as a family within the edrioasteroids, but other workers hypothesized a closer relationship to blastoids (Fay, 1962; Hud- son, 1925; others). Fay (1962) elevated the then- monospecific clade to class level, comparing them to both edrioasteroids and blastoids. Recently, Smith and Jell ( 1 990) described an early edrioblas- toid that provided much new morphologic evi- dence linking edrioblastoids with edrioasteroids. Our findings further support this relationship. We have not included cyclocystoids or astero- zoans in the parsimony analysis even though in the past they were presented as having been de- rived from edrioasteroids (Bather, 1 9 1 5b; Guens- burg, 1988; Paul & Smith, 1984; Smith, 1985; Smith & Jell, 1990; others). The relationship of either group to edrioasteroids is obscure and ham- pered by the lack of clearly diagnostic fossils. Ar- guments pro and con have been set forth in pre- vious works, and the fossils described here provide no additional evidence (see Blake, 1 994; Blake & Guensburg, 1993; Guensburg, 1988; Smith, 1985; Smith & Jell, 1990). This parsimony analysis includes data from 1 5 taxa that we feel sample a wide morphologic and taxonomic diversity of the class (Fig. 1). Charac- ters were selected based on a thorough review of edrioasteroid morphology, and all portions of the theca were included. We have attempted to code characters conservatively and avoid general fea- tures that could readily be subject to convergence, such as thecal shape. Several nested or uninform- ative characters were deleted during trial runs. Reasonably complete data sets were available, ex- GUENSBURG AND SPRINKLE: EDRIOASTEROIDEA Taxa 1 0 1 . 1 1 1 •Si | 1 1 1 .S I £ i CO c '§ 1 1 3 1 •2 -5 c 1 J •a ■a J 1 'S 8 1 h i 1 c B 3 •c s 0 1 B a "S3 | 3 8 f 1 a; B 'C B 8 B 1 1 B 2. 1 1 1 i 1 i 1 1 1 1 1 1 8 3. 1 1 1 i 1 7 1 1 1 1 1 1 8 4. B 8 1 i 1 1 1 1 1 1 1 1 8 5. 8 1 7 7 1 B 1 1 1 1 1 7 B 6. 8 1 1 1 1 1 8 B 8 B 8 B B 7. B 8 B 7 1 a 8 B B B B B 8 8. 8 8 1 7 1 7 B 8 8 B B B B 8 9. 8 1 1 1 1 B B B B B B 8 8 1 B. B B B 1 1 8 B B B B B B B 1 1. B 8 1 7 1 7 B B 8 8 B 8 B 12. 8 B 7 7 1 B 7 1 7 7 7 7 B 13. 8 1 7 1 1 7 B B 8 B B 7 B 14. B 8 B 1 1 B 7 7 1 1 1 1 7 B 15. 8 8 B B B B 7 1 8 B B a 7 B 16. B 8 8 1 1 7 B 7 a B B B 8 B B 17. B 8 B 1 1 7 B B B a B B B B 18. B 8 1 7 1 1 8 B B B 8 B B B 19. B 8 8 7 1 7 B B B 8 8 8 8 8 28. B 8 B 1 1 1 1 B B 8 7 8 B B 21. B 8 B 1 1 7 B 7 B B B B B B 8 22. 8 B 8 B B 7 7 B B B B B 8 B 23. B B B B B B B B 8 8 8 B 8 8 24. 8 B B 1 1 B B B 8 B B B 8 8 25. B B B 8 B B 8 B B B B B B 8 26. B 8 B 1 B B B B B B B 8 B B B 27. 8 B B 1 1 7 B B 8 8 8 B B B 8 28. B 8 B 1 B B B B B B B B B B 8 29. B 8 B 1 8 8 B 8 B B B B B B 8 38. 8 8 B 1 1 B B B B B 8 8 8 8 B 31. B 1 7 7 B 7 B B 1 1 1 1 7 B 32. 8 8 7 B B B B 7 1 7 7 7 7 B 33. B B B 8 B 8 B B 1 7 7 1 B 34. B B B B B B B B 1 B 8 35. 8 B B B B 8 8 B B 7 B 36. 8 8 B 8 B 8 B B 8 B 7 8 37. B 8 B 8 B B B B B B 8 B 38. B 8 B 8 8 8 B B 8 B B 8 39. 8 8 B B 8 B B 8 B B 7 8 B 48. 8 B B 8 B 8 B 8 B 8 a B B 8 41. 8 8 B B 8 B B 8 8 B 7 7 7 B 42. 8 B B B 8 B B 8 B 8 B 1 B 8 B Explanation of symbols B = primitive 1 = derived ? = unknown or lost. Fig. 1 . Data matrix for the edrioasteroid parsimony analysis. Explanation of the characters along with polarities is provided in Table 1 . One of the two preferred maximum parsimony trees is included below for comparison. cept for those of a few Cambrian taxa (Fig. 1). They constitute the best current information for early edrioasteroid morphology. Forty-two char- acters were polarized and assembled into a data matrix (Table 1); these data were then subjected to a maximum parsimony analysis using PAUP version 3.0n (Swofford, 1991). Characters were unweighted. Eighteen most-parsimonious trees of 54 steps were obtained using a branch-and-bound search, which guarantees maximum parsimony tree discovery. Consistency indices (CIs) for the trees were 0.778 with uninformative characters includ- ed and 0.721 with uninformative characters de- leted. The skewness measure (g,) of the tree length FIELDIANA: GEOLOGY rC m Stromatocystites Cambraster Edriodiscus Pyrgocystinae Lebetodiscinae Chatsworthia Agelacrinitidae 'S. ' walcotti Totiglobus Edrioasteridae Astrocystitidae Rhenopyrgus Cyathocystis T. lloydi Camptostroma Stromatocystites Cambraster Edriodiscus Pyrgocystinae Lebetodiscinae Chatsworthia Agelacrinitidae Totiglobus Edrioasteridae — | I — Astrocystitidae — Rhenopyrgus — Cyathocystis — 'T. lloydi — 'S. ' walcotti — Camptostroma r€ Stromatocystites Cambraster Edriodiscus rC Pyrgocystinae Lebetodiscinae 1 Agelacrinitdae Chatsworthia 'S. ' walcotti Totiglobus Edrioasteridae Astrocystitidae Rhenopyrgus Cyathocystis 7". lloydi Camptostroma LC B rt Stromatocystites Cambraster Edriodiscus Pyrgocystinae Lebetodiscinae Chatsworthia Agelacrinitidae '5. ' walcotti Totiglobus Edrioasteridae — | | — Astrocystitidae — Rhenopyrgus ' — Cyathocystis — 'T.'lloydi — Camptostroma Fig. 2. Cladograms generated by the edrioasteroid parsimony analysis. A, B, Two preferred trees; C, D, Adams and strict consensus trees, respectively. distribution was — 1.01, indicating a high level of phylogenetic signal (Huelsenbeck, 1991). We il- lustrate two preferred trees along with Adams and strict consensus trees (Fig. 2), and one preferred tree is combined with the data matrix for com- parison (Fig. 1). The consensus trees each contain three polytomies at similar locations where data are sparse. Stratigraphic occurrences of the taxa agree well with the preferred trees. Like Paul and Smith ( 1 984), we use Camptostro- ma of the Early Cambrian as the outgroup for edrioasteroid parsimony. Derstler (1981) and Paul and Smith (1984) reinterpreted the morphology and phylogenetic position of Camptostroma in slightly different ways. Both restored the oral sur- face with the basic edrioasteroid morphology, in- cluding an upward-oriented domal surface incor- porating five ambulacra arrayed in a 2-1-2 pattern and lacking skeletized appendages, a central mouth with unfused mouth frame, food grooves with bi- GUENSBURG AND SPRINKLE: EDRIOASTEROIDEA Table 1 . Characters used in the cladistic analysis of edrioasteroids. Table 1. Continued. Derived Primitive Derived Primitive 1 . Attachment surface expanded beyond bas- al disc 2. Thecal plating uni- laminate 3. Primary cover plates 4. Epispires lacking 5. Oral frame of com- pound plates 6. Marginal ring 7. Basal disc decalcified 8. Aboral ribbing 9. Peripheral rim 10. Interambulacrals im- bricate 1 1 . Floor plates hidden 12. Oral frame with five compound radial plates 13. Hydropore slit with hydropore oral plate 14. Cover plates a uni- form biseries 15. Cover plates a uni- form triseries or greater 16. Intrathecal cover plate passageways 17. Intrathecal cover plate extensions 18. Trough-shaped food groove 19. Uniserial floor plates 20. Sutural passageways lacking 2 1 . Three primary differ- entiated oral cover plates 22. Four or more primary differentiated oral cover plates 23. Valvular periproct of uniform wedge- shaped plates 24. Pedunculate zone 25. Recumbent zone 26. Floor plates lacking 27. Prismatic cover plates 28. Hood plates 29. Articulated spines 30. Petalloid ambulacra 3 1 . Oral frame with five compound interradial plates Attachment surface a bas- al disc Thecal plating multilami- nate Primary cover plates lack- ing Epispires present Frame plates not fused Marginal ring lacking Basal disc plated Ribbing lacking Rim lacking Interambulacrals tesellate Floor plates exposed Compound radial orals lacking Hydropore a pore bound- ed by several interam- bulacrals Cover plates an irregular biseries Cover plates an irregular multiseries Passageways lacking Extensions lacking Notched food groove Biserial floor plates Sutural passageways Oral cover plates nondif- ferentiated Oral cover plates nondif- ferentiated Periproct with irregular platelets Pedunculate zone lacking Recumbent zone lacking Floor plates Tabular cover plates Hood plates lacking Spines lacking Ambulacra straight-sided or with distal taper Compound interradial plates lacking 32. Hydropore a fixed pore or slit, shared across two interambu- lacrals 33. Ambulacra with broad lateral floor plate extensions 34. Basal disc plate ring above substrate 35. Collar 36. All interradial cover plates meet over mouth 37. Deltoids 38. Hydropore lost or fixed pore through deltoid 39. Sutural passageways small, shifted abradi- ally 40. Interambulacrals in uniform circlets 41. Stalk with plate mo- saic or columniform plates 42. Coriaceous sac Hydropore a pore bound- ed by several interam- bulacrals Broad lateral floor plate extensions lacking Plate ring contacting sub- strate Collar lacking Lateral interradial plates separated from others Deltoids lacking Hydropore a pore bound- ed by several interam- bulacrals Passageways relatively large adradial Interambulacrals irregular Stalk lacking Sac lacking serial laterally exposed floor plates with sutural pores below, articulating cover plate sheets above, and hydropore and periproct in a broad CD in- terray. However, Paul and Smith (1984, Fig. 5) depicted Camptostroma with a wide conical ab- oral surface that was unattached and presumably inserted into soft substrata. In this respect, Camp- tostroma would have been more like helicopla- coids, from earlier in the Cambrian. This is con- sistent with the hypothesis of these authors that Camptostroma was the stem group to all other pentaradiate echinoderms. Derstler (1981) consid- ered Camptostroma to be an edrioasteroid not far removed from the ancestry of blastozoan echi- noderms. He illustrated the aboral surface of Camptostroma with a convex zone surrounding a flat central platform (Derstler, 1981, Fig. 1). (See Durham, 1967, Fig. 396, for an excellent illustra- tion of a specimen showing this feature.) We ex- amined specimens in our possession and believe the Derstler restoration to be accurate. We inter- pret the central platform to be the basal disc (see Function and Evolution, below) generally like that of other early edrioasteroids, further reinforcing the view that Camptostroma was an edrioasteroid. The term basal disc was used by Bell and Sprinkle FIELDIANA: GEOLOGY (1978) for the attachment structure of Totiglobus, and we apply this term universally to edrioasteroid aboral structures capable of maintaining suction for clinging. Two initial branching patterns were generated by the parsimony analysis (Fig. 1 ). In some trees, Stromatocystites of the Early to Middle Cambrian was the sister group to Camptostroma. An analysis by Smith (1985) produced similar findings. Stro- matocystites was the stem taxon of the isorophid edrioasteroids in other trees. The discoidal theca of this taxon is reminiscent of isorophids. The oral surface of Stromatocystites is much like that of Camptostroma, but the aboral surface is broad and flat (Smith, 1985; Smith & Jell, 1990). The basal disc has a plate ring inside (aboral to) the thecal margin. In our opinion, other workers have mis- taken this structure for the marginal ring in certain derived taxa (for instance in Bell, 1980; Smith, 1985; Smith & Jell, 1990) (see below). Internally, the basal disc of S. reduncus is distinguished by a series of ridges radiating outward from the plate ring (Smith & Jell, 1990). The parsimony analysis supports observations of Smith and Jell (1990, pp. 726-727), who re- garded "Stromatocystites" walcotti as having iso- rophid synapomorphies. This taxon represents a new genus, but its redescription would require much further study, so we refer to it as "5." wal- cotti. It has an ill-defined marginal ring bordering the lateral thecal margin (Smith, 1985, text Figs. 4, 7) and the aboral surface had a basal disc with plate ring, providing evidence that these two struc- tures are separate and independently derived. The plate ring is the older and more widely distributed of the two. The floor plates, although biserially plated, have a narrow trough shape and lack su- tural pores; these are both isorophid synapomor- phies (Fig. 3). The main body of these plates is adradial and proximodistally elongate. Each floor plate commonly bears two (sometimes one) lateral projections that articulate with similar projections from interambulacral plates. Cambr aster plotted as the sister group to "S." walcotti (Figs. 1 , 2). It is a problematic fossil from the Middle Cambrian (Fig. 1) (Smith, 1985; Jell et al., 1985). Biserial floor plates, sutural pores, and full aboral plating are plesiomorphous. A bas- al disc with plate ring is present. There is a large marginal ring and a peripheral rim forming the thecal margin. This, together with the presence of an articulated hydropore plate, are isorophid syn- apomorphies. The oral frame consists of five in- terradially positioned elements that appear to be Fig. 3. Comparison of floor plate arrangement and morphology between Stromatocystites pentangularis and "S." walcotti. A, Reconstructed floor plate series of 5. pentangularis in exterior oral view based on drawings of individual floor plates in Smith (1985, text Fig. 6); cover plates with sutural passageways typical of primitive ed- rioasteroids and edrioasterids, much enlarged. B, Floor plate series of "S." walcotti in interior oral view taken from usnm 376690 and modified from Smith (1985, text Fig. 7); floor plates elongated with lateral prongs, no sutural passageways. apomorphous because radially positioned plates form the oral frame of typical isorophids. Edriodiscus, also of the Middle Cambrian, plot- ted as the sister group to Cambraster in the par- simony analysis. Its morphology is incompletely known but appears to have been intermediate be- tween that of "S." walcotti and typical isorophids (see Smith, 1985, text Fig. 12, for a similar find- ing). Synapomorphies with typical isorophids in- clude a marginal plate ring with uniserial plate circlets beyond forming the thecal margin, aboral ribbing, and trough-shaped floor plates. Plesio- morphies with Stromatocystites include a fully plated aboral surface, calcified basal disc with plate ring, and perhaps biserial floor plates. Smith and Jell (1990, p. 771 and Fig. 51) gen- erated a phylogenetic analysis in which Edriodis- cus, Cambraster, and "S." walcotti mapped as branching toward ancestral sea stars prior to the edrioasterid-isorophid dichotomy. Few synapo- morphies among these three taxa and traditional isorophids were discovered by their analysis. We feel their results were spurious, for the following reasons. Only 1 6 characters were provided in the full analysis. Oral surface convexity (their char- acter 7) and ambulacral curvature (character 4) are GUENSBURG AND SPRINKLE: EDRIOASTEROIDEA not significant at high phylogenetic level. For in- stance, we use convexity as a generic taxobasis to separate the edrioasterids Paredriophus and Ed- riophus, genera that numerous synapomorphies suggest were closely related. Smith and Jell (1990, p. 720) themselves applied ambulacral curvature as a specific taxobasis for Stromatocystites. Final- ly, the hypotheses for homology of some mor- phologies used by Smith and Jell cannot be sub- stantiated, and in our opinion these authors did not provide a balanced treatment of the evidence. They homologized the marginal ring of Edriodis- cus with marginals of the early sea star Archae- gonaster and applied this hypothesis (characters 1 2 and 1 5) to their cladogram (Smith & Jell, 1 990, Table D) (see Blake & Guensburg, 1993; Blake, 1 994, for critiques). In conjunction, they expressed doubt as to the homology of marginal ring plates with the proximal circlet of the peripheral rim of typical isorophids. They contrasted the two, stat- ing that the marginal ring plates of Edriodiscus were "stout barrel-shaped ossicles that abut" whereas those of isorophids were "thin imbricate plates that overlap" (Smith & Jell, 1990, p. 771). However, much evidence supporting the case for homology was not discussed. The marginal ring of Edriodiscus contacts the theca below and bounds the thecal margin in exactly the same manner as the proximal circlet, and there is aboral ribbing in both cases. The isorophids Savagella and Hystri- chopsydrax have abutting proximal circlet plates similar in size to those of Edriodiscus (Guensburg, 1988), and the imbricate proximal circlet of typical isorophids is usually not thin but thick. Smith (1985, p. 729, 753) previously recognized the sim- ilarities between the peripheral rims of Savagella and Edriodiscus and the aboral ribbing of agela- crinitid isorophids and Edriodiscus. The Late Cambrian Chatsworthia is poorly known but appears to have achieved the typical isorophid design that persisted for much of the remainder of the Paleozoic (Smith & Jell, 1 990) (Fig. 1). The theca is discoidal and the marginal ring consists of imbricate plates integrated into the peripheral rim as the proximal circlet. Central ab- oral plating is apparently lacking, and we presume the basal disc was decalcified. Cover plating in- cluded uniform primary plates, and floor plates are entirely internal. The branching order of Chat- sworthia, lebetodiscinids, and agelacrinitids was unresolved by the parsimony analysis (Fig. 2). The various trees depict Chatsworthia as the sister group to all post-Cambrian isorophids or as the sister group to lebetodiscids. Details of the oral area and ambulacral construction for Chatsworthia, if known, would likely resolve this uncertainty. Le- betodiscid and agelacrinitid isorophids were the most diverse and long-ranging edrioasteroids. They are distinguished by details of the ambulacra, oral plating, and periproct (Fig. 1) (see also Bell, 1 976a, 1980, for thorough discussions). Oral cover plates of both groups are distinct from ambulacral cover plating and included articulated hydropore plates. Ambulacral cover plates of agelacrinitids often form a complex uniform multiseries, and there is a valvular periproct with distinctive uniform plat- ing (Bell, 1 976a). Pyrgocystinids plotted as the sis- ter group to the lebetodiscinids in the parsimony analysis (Figs. 1, 2). (See Kesling, 1967, p. 201, and Bell, 1980, pp. 160, 165, for supportive statements.) They have unique ambulacral construction among edrioasteroids in which the floor plates are lost and hood plates are present (see pyrgocystinid dis- cussion under Systematic Paleontology). The clearest evidence for the origin of thecal elongation structures in edrioasteroids is the pe- dunculate zone found in two isorophid clades, pyr- gocystinid lebetodiscids and clavate agelacrinitids. Elongation was achieved in both cases by the ad- dition of plates from the interambulacrals that ex- tend the theca beyond the ambulacra, but proxi- mal to the peripheral rim (including the marginal ring). In pyrgocystinids, the pedunculate zone is cylindrical and composed of squamose plates sim- ilar to interambulacrals. In clavate agelacrinitids, there is further elaboration with a distinctive re- cumbent zone proximal to well-ordered columns of squamose plates of the pedunculate zone (Sum- rail, 1992). The pedunculate zone of both pyrgo- cystinid lebetodiscids and clavate agelacrinitids does not frame the theca but bounds the basal attachment area beneath the theca. Several ex- amples of incipient thecal elongation are also found in isorophids (Cystaster, Stalticodiscus, Ulrichi- discus, and Deltadiscus; see also Sumrall & Sprin- kle [ 1 990]), and therefore it is a subjective matter as to what qualifies as a pedunculate zone. The parsimony analysis mapped edrioasterids, edrioblastoids, and cyathocystids (Figs. 1 , 2) as a sister group to the isorophids. These taxa had glob- ular, clavate, bud-shaped, and cylindrical thecae (see Sprinkle & Bell, 1978; Bell, 1982; Smith, 1985). They retained plesiomorphic ambulacra with lat- erally exposed floor plates and sutural passage- ways, although the floor plates were fused, forming deltoids in some species. The parsimony analysis supports our assertion that the peripheral rim and FIELDIANA: GEOLOGY marginal ring were lacking in this clade (Fig. 1). "Totiglobus" lloydi and Totiglobus, both Middle Cambrian, were early branches (Figs. 1 , 2). Toti- globus is particularly well known. The aboral sur- face has a small basal disc bordered by a plate ring (termed "marginal plates" by Bell & Sprinkle, 1978, p. 254, and "marginal ring" by Smith, 1985) bear- ing internal septate radiating ridges. Ridges con- verge from the plate ring toward the center of the basal disc (there is no smooth central platform as found in Stromatocystites reduncus; see above) (Bell & Sprinkle, 1978, text Fig. 4). The broad ambu- lacra are arranged in the plesiomorphic 2-1-2 pat- tern but are roofed by derived uniform biserial cover plates. Oral cover plates, in contrast to those in isorophids, are not differentiated from ambu- lacral cover plates. "Totiglobus" lloydi was pro- visionally assigned to genus at the time of its de- scription because of poor preservation (Sprinkle, 1985). The theca is bud-shaped, and the oral sur- face appears to be similar to Totiglobus, but there is a short conical tesselate-plated elongation of the theca distal to the ambulacra. The basal disc is unknown. Walcottidiscus from the Middle Cam- brian has been presented as the sister group to the edrioasterids (Smith & Jell, 1990, p. 771). The specimens are all poorly preserved and lack most data, so we omitted this taxon from the parsimony analysis. There appear to have been imbricate plate circlets distal to the ambulacral tips and surround- ing a noncalcified central area (see Smith, 1985, PI. 89), vaguely similar to a plate collar (see below). The edrioasterids branched as the sister group to Totiglobus in the parsimony analysis (see Paul & Smith, 1984, p. 468, for a supportive view). Along with those features of the oral surface men- tioned above for Totiglobus, edrioasterids have a fixed hydropore slit through the interambulacral plates. The distal theca has a short, stalk-like collar of small, partly imbricate plates or platelets (Bell, 1976a). The collar joins the theca abruptly at a flange (part of the "resting zone" of Bell, 1976a). We interpret flange plates as probably homologous to the basal disc plate ring; the collar would then have been derived from the basal disc. Less likely, both collar and plate ring were derived by modi- fication of the theca between the ambulacra and the basal disc. Whichever case is correct, this con- struction differs from isorophids, in which the marginal ring/peripheral rim contacts the sub- strate beyond the basal disc and the elongate pe- dunculate zone, if present, is above. Cyathocystids and edrioblastoids branched from edrioasterids, but their interrelationships were un- resolved by the parsimony analysis (Fig. 1). Syn- apomorphies linking these two disparate groups and typical edrioasterids are a globular or elon- gated theca, typically with tesselate plating; a fixed hydropore (not bordered by articulated plates); broad ambulacra elevated by inclined lateral floor plate extensions; nonporous uniform biserial cov- er plates (edrioasterids such as Edrioaster have tiny accessory plates along the perradial suture); and a basal disc plate ring and collar or stalk. Bell (1980, p. 169) commented that edrioblas- toids and cyathocystids share similarities of con- struction, and they were linked as sister groups in a parsimony analysis by Smith and Jell ( 1 990, p. 745). These authors acknowledged the tenuous connection resulting from the great morphologic disparity among the few known taxa. The cladistic analysis, including data from new taxa, produced similar findings (Figs. 1 , 2). The most convincing synapomorphies are the oral cover plate arrange- ment and the nature of the floor plates. Both cyath- ocystids and edrioblastoids have five elongate oral cover plates ("primordial orals" of Smith, 1985; Smith & Jell, 1 990) occupying the interradial po- sition and meeting centrally above the mouth. There is, in effect, a nearly pentaradiate symmetry in both groups. This arrangement differs from ed- rioasterids in that the lateral interradial cover plates ("lateral bifurcation plates" of Bell, 1 976a) are not separated from the other three interradial cover plates. The floor plates in both cases consist of deltoids, each of which is formed of adjacent half ambulacra pairs bordering interambulacra. Bell (1982) and Bockelie and Paul (1983) interpreted the deltoids in cyathocystids as being interam- bulacral or interradial (and both therefore also concluded that cyathocystids lacked floor plates), whereas Smith and Jell (1990) argued that they were modified floor plates homologous with those of edrioblastoids. We agree with Smith and Jell because the deltoids in cyathocystids, despite their expanded size and lateral position, still support and articulate with the cover plates in the usual manner found in almost all other edrioasteroids. The deltoids of the Early Ordovician edrioblastoid Lampteroblastus described here are reminiscent of those in cyathocystids. They are triangular, level with adjacent interambulacral thecal plates, and fill the interambulacra. Smith and Jell (1990, pp. 745-746) stated that the deltoid plates of the advanced edrioblastoid Astrocystites represent the expanded "first ambu- lacral flooring plates," therefore implying the elim- ination of all other flooring plates. These authors GUENSBURG AND SPRINKLE: EDRIOASTEROIDEA did not suggest how this could have occurred in relation to other features, such as the deltoid pore system, or the effects on the overlying cover plates, and they cited no intermediates to support their case. We hypothesize that deltoids formed by fu- sion of all the floor plates from two adjacent am- bulacra and the connecting oral frame plate. In support of our interpretation, we note that (a) there is no loss of contact between existing floor plates and cover plates or wholesale shifting of contacts as would be required in the expanded flooring plate scenario; (b) the system of through-going pores of each deltoid in edrioblastoids and cyathocystids consists of reduced sutural pores analogous to those of other edrioasterids (one of us [T.E.G.] has re- cently collected a specimen of Cyathocystis that preserves sutural pores like those found in ed- rioblastoids such as Astrocystites [Fig. 17D]; (c) the distal floor plates taper with diminishing abra- dial exposure, which would produce a shape sim- ilar to deltoids if fused; and (d) fusion of floor plates, at least around the oral area, was a universal feature among all but the most primitive edrioas- teroids and therefore is consistent with other clades. Suggested homologies for the aboral morphol- ogies of the cyathocystid Rhenopyrgus and the ed- rioblastoids Cambroblastus and Astrocystites were provided by Smith and Jell (1990, text Fig. 34). We accept this interpretation as a strong possibil- ity, but we believe different terminology should be used: plate ring rather than "marginal" zone, again reflecting our finding that marginal ring plates are found only in isorophids. Smith and Jell (1990, p. 745) interpreted the Late Cambrian edrioblastoid Cambroblastus as too specialized to have been a suitable ancestor to cyathocystids because of de- rived features, including the narrow stalk and stan- dardization of thecal plates into distinct circlets. On the other hand, Cambroblastus has no deltoids (Smith & Jell, 1990, p. 749), a critical synapo- morphy with cyathocystids; instead, it apparently has plesiomorphous biserial floor plates. The Early Ordovician Lampteroblastus, n. gen., has trian- gular deltoids without raised margins, very rem- iniscent of the deltoids found in cyathocystids, but the lower theca and stalk morphologies are of typ- ical edrioblastoid construction. Aboral and elongation structures of cyathocys- tids are unique among edrioasteroids: a solid fused cuplike element of Cyathocystis or distal imbricate zone and coriaceous sac of Rhenopyrgus. These are so different that we use them as a subfamilial tax- obasis within the Cyathocystidae. Both could have evolved by extensive modification of the basal disc, but there are as yet no fossils providing interme- diate morphologies. Features of the ambulacra/ oral area and intrambulacra for the two genera are remarkably similar. Rhenopyrgus grayae and Cyathocystis spp. have a plate ring surrounding the oral area proximal to the distal fused cup. Bockelie and Paul (1983, Fig. 4) homologized these structures with the "marginal ring" or "pedun- culate zone" of isorophids, but this is incorrect in our opinion. The situation of cyathocystids is like that of edrioasterids, where a plate ring is followed by the elongation structure (collar or cup). Considering edrioblastoids separately, we be- lieve they were the sister group to edrioasterids, whose origin can perhaps be traced back through Cambroblastus to the Middle Cambrian "Totiglo- bus" lloydi. Cambroblastus (Smith & Jell, 1990), with its much elongated polyplated stalk or short ambulacra with persistently plesiomorphic biser- ial floor plates, is a morphologic intermediate be- tween "T." lloydi and the Ordovician Lamptero- blastus and Astrocystites. The stalk and theca of the latter two advanced edrioblastoids presumably evolved through the plate reduction and unifor- mity that typified many lineages after the Cam- brian (Guensburg & Sprinkle, 1992). The theca of edrioblastoids is remarkably convergent with the theca of parablastoids and blastoids. The edrio- blastoid stalk appears to have evolved through a series of steps similar to that of blastozoans and crinoids (see Paul & Smith, 1984, Fig. 15). Function and Evolution Previous authors generally agree that edrioas- teroids were sessile low-level suspension-feeding organisms (Bell, 1976a; Smith, 1985; Sumrall & Sprinkle, 1992; others). Psolid holothurians (Reg- nell, 1966; Derstler, 1985; Guensburg, 1988) and balanimorph barnacles (Sumrall & Sprinkle, 1 992) have been suggested as general modern analogues for isorophid edrioasteroids. Details must be re- constructed from morphologies and associated pa- leoenvironments, and contention over aspects of edrioasteroid paleobiology remains. The following discussion outlines temporal changes in the func- tional morphology of feeding, respiration, posi- tioning, and posturing for edrioasteroids. Edrioasteroids were presumably ciliated mucus feeders (Smith, 1985, p. 727). If so, cilia likely 10 FIELDIANA: GEOLOGY covered the epithelial lining of the ambulacral tun- nels, creating feeding currents and transporting food particles along a mucous train to the mouth. Most Early and Middle Cambrian and later edrioasterid edrioasteroids had sutural pores through the floor plates that presumably housed ducts leading to internal ampullae (Bell, 1976a; Smith, 1985). This suggests the presence of extensible tube feet that could have supplemented food gathering or pro- vided a mechanism to open the cover plates (Smith, 1985, pp. 726-727). Competing interpretations depict the radial canal as either external (Bather, 1915a; Paul & Smith, 1984; Smith, 1985) or in- ternal beneath the floor plates (Bell, 1976a). We prefer the former interpretation for the reasons given by Smith (1985, p. 725, text Fig. 8) and the fact that there is a secondary groove along the perradial suture in edrioasterids such as Edriophus that could have held the radial canal (see Bell, 1 976, text Fig. 2B). As pointed out by Smith (1985, p. 725), the ambulacral construction of isorophids is highly derived. Sutural pores have been lost, and the floor plates form a smooth trough along the base of the ambulacra. We cannot identify any specific structures that housed ampullae, or the radial canal, and we hypothesize that they and tube feet were lacking. If so, opening and closing the cover plates was accomplished by connective tis- sues, and food gathering was by the ciliated epi- thelial lining. Isorophid cover plates articulated with interambulacrals laterally (rather than with inclined lateral floor plates) and floor plates below (rather than floor plates only). The gap between interambulacrals and floor plates was occupied by cover plate extensions that projected into the the- cal interior, presumably providing the mechanism to fully operate the cover plates without exposing the connective tissues (see Bell, 1976a, text Fig. IB). Smaller secondary cover plates composed uniform multiseries for agelacrinitid isorophids. The most elaborate patterns of these occur in Car- boniferous discocystid agelacrinitids, for which there is a complex oscillating perradial suture that can span nearly the entire ambulacral width (e.g., Sumrall, 1992). This presumably facilitated feed- ing with slight gaping of the cover plates (similar to the development of plications in certain artic- ulate brachiopods), reducing exposure of the food groove. Ambulacra of discocystids were converse- ly very narrow. Specialized respiratory structures were present in all edrioasteroids. Early to Middle Cambrian taxa often had epispires between interambulacrals, and the Ordovician edhoblastoid Astrocystites had thin stereom and channelways at interambulacral plate corners. A hydropore is found in all edrioas- teroids but appears to be more elaborate in iso- rophids, in which there was an articulated and often large hydropore oral plate. Edrioasterids and derivatives had a small fixed hydropore slit or pore. Respiration for agelacrinitid isorophids was apparently supplemented by anal pumping using the valvular periproct, similar to holothurians or comatulid crinoids (Williams, 1918; Bell, 1976a; Sumrall & Sprinkle, 1991). Lebetodiscid isoro- phids had specialized pores or thin stereom be- tween adjacent cover plates (intrathecal passage- ways) (Bell, 1976a, p. 38). Additional pores are found between hood plates of pyrgocystinids (see pyrgocystinid discussion under Systematic Pale- ontology). Early and Middle Cambrian edrioasteroids had fully plated aboral surfaces incorporating basal discs. The basal disc in all these taxa except Camp- tostroma was strengthened by one or sometimes two plate rings. The interior disc surface has been described in detail for Stromatocystites reduncus (Smith & Jell, 1990) and Totiglobus nimius (Bell & Sprinkle, 1978). In both species, ridges radiating from ring plates onto other disc plates presumably served as attachment sites for connective tissues and are interpreted to have enabled clinging by suction (Bell & Sprinkle, 1978; Smith, 1985; Smith & Jell, 1990). These organisms presumably re- leased after death or when under duress, and not surprisingly, few of the fossils are preserved ad- hering to any recognizable surface. A Totiglobus- like specimen in our possession is affixed to a trilobite free cheek. Smith (1985) previously hy- pothesized that two of the genera, Stromatocystites and Cambraster, lay unattached on the seafloor. Yet it seems reasonable to assume that some sort of firm surface would have been necessary for suc- tion to have been effective. Perhaps adhesion sites had low preservation potential (see Guensburg, 1988, for a similar discussion on unusual isoro- phid edrioasteroids). The marginal ring of the early edrioasteroids "Stromatocystites'''' walcotti and Cambraster did not contact the substrate and pre- sumably stiffened the theca, but later this structure was incorporated into the peripheral rim of all isorophids and participated in sealing the thecal margin, as well. Isorophid edrioasteroids beginning with the Middle Cambrian Edriodiscus had a uniserially plated peripheral rim contacting the substrate be GUENSBURG AND SPRINKLE: EDRIOASTEROIDEA 11 yond the basal disc. Lower plate surfaces were radially ribbed, presumably enabling more effec- tive gripping (Caster, in Bell, 1976a, p. 30). The basal disc area was decalcified in most taxa by the Late Cambrian. The peripheral rim, like the basal disc, was not skeletally attached, but the vast ma- jority of isorophids are preserved adhering to hard calcareous surfaces. Sites included several types of bioclastic or mound hardgrounds and a variety of "shelly" surfaces: bivalves, cephalopods, gastro- pods, rugose corals, brachiopods, bryozoans, cri- noids, blastozoans, and trilobites. Many fossils preserve only the peripheral rim or a partial pe- ripheral rim, with the remainder of the theca high- ly disrupted or even missing. Therefore, this struc- ture must have sealed the thecal margin with some sort of durable biochemical adhesive or tissue (Bell, 1976a). The aboral surface of many edrioasterid ed- rioasteroids is not well known, but presumably they adhered by suction as well. The substrate- contacting surface of Paredriophus was apparently fully plated (Fig. 4D) but that of Edrioaster was apparently decalcified (Bell, 1976b, PI. 58, Fig. 4). Most edrioasterids occur on hardgrounds. Cyath- ocystids had unusual aboral morphologies for ed- rioasteroids. Cyathocystis was skeletally cemented without a basal disc (Bockelie & Paul, 1983, p. 258). Rhenopyrgus presumably lived partly em- bedded in soft substrata, anchored by a coriaceous sac (Smith, 1985). The evidence as to whether most edrioasteroids could move is contentious (see Bell, 1 976a; Meyer, 1 990; Smith, 1 983; Sumrall & Sprinkle, 1 992), but it would seem that adhesion by suction would have provided ample opportunity to do so. All modern organisms using this type of attachment of which we are aware, such as psoloid holothurians, poly- placophorans, limpets, and anemones, have this capability. Holdfasts of fixed echinoderms (cyath- ocystid edrioasteroids, some crinoids) skeletally attach to hard surfaces. Even limited movement potential for edrioasteroids could have provided versatility by enabling repositioning and reattach- ment. Elongation of the theca among isorophids was accomplished by an extensible pedunculate zone of highly imbricate plates. This construction pro- vided the means to extend the theca to advanta- geous feeding or gamete broadcasting levels but required an extensive supporting system of liga- mentous tissues. Some pyrgocystinids and clavate agelacrinitids had exaggerated pedunculate zones that could not have been withdrawn into the area within the peripheral rim but were still capable of considerable contraction (Sumrall, 1992, Figs. 3, 11D). The distal collar of edrioasterids was composed of nonimbricate or only slightly imbricate plates that we hypothesize had limited contraction ca- pabilities and therefore functioned more as a short stalk than a pedunculate zone. The stalk of ed- rioblastoids was presumably derived from the dis- tal collar or interambulacrals and initially con- sisted of a rigid plate mosaic, but was modified in more derived forms to columniform plates. Thecal elongation in Rhenopyrgus was accomplished with an extensible collar closely convergent on the iso- rophid pedunculate zone. The distal cup of Cyath- ocystis can be considerably elongated. Many Cyathocystis specimens recently discovered by the senior author in original position are inverted or laterally oriented in reef cavities or overhangs, similar to occurrences of the extant crinoid Hol- opus. Revised Classification A revised Linnaean classification of the class Edrioasteroidea is offered below. The extensive new material described here has reinforced our belief that edrioasteroid clades form a close phy- logenetic unit; in this respect our basic philosophy more closely resembles that of Smith (1985) and Smith and Jell (1990) than that of Bell (1976a, 1 980). We make the following observations as jus- tification for taking this approach. Many wide- spread plesiomorphies are apparent in the char- acter matrix developed for the cladistic analysis, indicating that the basic construction of the taxa studied is quite uniform (Fig. 1). Many traditional familial level taxa are "defined," at least in large part, not on shared derived characters but rather on unique character combinations; individual characters themselves are often plesiomorphic at some higher level; in fact, there are often few de- fining apomorphic characters (see Edrioasteroid Phylogeny). We have reduced most traditional families to subfamilial rank and reduced higher- level taxa accordingly. In addition to philosophical considerations, our classification differs from that of Bell (1980) in that the parsimony analysis mapped cyathocystids as derived from edrioas- 12 FIELDIANA: GEOLOGY tends rather than isorophids, and edrioblastoids were specialized edrioasterids rather than a sep- arate class. The classification offered by Smith is an abbreviated phylogenetic version. It differs most significantly from ours in combining pyrgocystids and cyathocystids as an order, in its inclusion of the cyclocystoids as a family within the isorophids, and in placing lebetodiscids as a subfamily within the Agelacrinitidae. A compilation of edrioaster- oid genera included within families of the tradi- tional classification is listed in the Appendix. (A few genera listed in the Appendix fall outside of the existing familial nomenclature listed below, but we have not erected a new classification scheme to receive them because this exceeded the focus of this paper.) The Linnaean systematic classification adopted here is as follows: Class EDRIOASTEROIDEA Billings, 1858 Order CAMPTOSTROMATOIDA Durham, 1966 Family CAMPTOSTROMATIDAE Dur- ham, 1968 Order STROMATOCYSTITIDA Bell, 1980 Family STROMATOCYSTITIDAE Bas- sler, 1935 Order ISOROPHIDA BELL, 1976 Family AGELACRINITIDAE Chapman, 1860 (emend.) Family LEBETODISCIDAE Bell, 1976 (nomen transl., emend.) Subfamily LEBETODISCINAE Bell, 1 976 (nomen transl.) Subfamily CARNEYELLINAE Bell, 1976 (nomen transl.) Subfamily PYRGOCYSTINAE Kesling, 1967 (nomen transl., emend.) Order EDRIOASTERIDA Bell, 1976 (emend.) Suborder EDRIOASTERINA Bather, 1898 (nomen transl., emend.) Family TOTIGLOBIDAE Bell and Sprin- kle, 1978 Family EDRIOASTERIDAE Bather, 1 898 Suborder EDRIOBLASTOIDINA Fay, 1962 (nomen transl., emend.) Family ASTROCYSTITIDAE Bassler, 1935 (emend.) Family CYATHOCYSTIDAE Bather, 1899 (emend.) Subfamily CYATHOCYSTINAE Bather, 1 899 (nomen transl., emend.) Subfamily RHENOPYRGINAE Hollo- way and Jell, 1983 (nomen transl., emend.) Systematic Paleontology Subphylum ECHINOZOA Matsumoto, 1929 Class EDRIOASTEROIDEA Billings, 1858 Order EDRIOASTERIDA Bell, 1976 (emend.) Diagnosis— Edrioasteroids with globular, bud- shaped, or turret-shaped theca; oral frame con- taining five compound interradial elements, hy- dropore a fixed slit or pore through a single plate or shared by two plates immediately below the oral area in the posterior interray, ambulacra with alternating plate biseries, cover plates without in- ternal extensions, oral plating nondifferentiated except five interradial orals extended to meet per- radially in some taxa, biserial floor plates separate or fused, with sutural passageways; poorly orga- nized periproct, plate ring and collar derived from adhesion disc. Discussion— The Edrioasterida comprise a di- verse assemblage of taxa, including edrioasterids, edrioblastoids, and cyathocystids. They range in age from Middle Cambrian through Late Ordo- vician. Suborder EDRIOASTERINA Bather, 1898 (nomen transl., emend.) diagnosis— Edrioasterids with globular or bud- shaped theca, oral frame with five compound in- terradial plates and usually five compound radial plates, hydropore a slit shared across two plates; floor plates biserial with sutural pores, lower theca incurved toward adhesion disc with stout plate ring or, later, modified to distal plate ring and collar with interior attachment surface nonplated, collar can be elongated into stalk. discussion— This taxon is essentially equiva- lent to Bather's family Edrioasteridae as defined by Bell (1976a, 1980) but is expanded to include their progenitors, the family Totiglobidae. The group ranges from Middle Cambrian to Middle Ordovician in age. GUENSBURG AND SPRINKLE: EDRIOASTEROIDEA 13 Family EDRIOASTERIDAE Bather, 1898 Discussion— See revised diagnosis in Bell (1976a, p. 291). Genus Paredriophus Guensburg and Sprinkle, new genus Type Species— Paredriophus elongatus Guens- burg and Sprinkle, new species. Diagnosis— Theca elongate, bud-shaped; am- bulacra long, apparently straight, raised, only one set of cover plates; interambulacra flat to slightly concave with fairly large tesselate plates, periproct low on CD interray; short attachment collar of tiny imbricate plates at base of theca; oral cover plates similar to those of Edriophus. Occurrence— Early Ordovician, western Utah, USA. Etymology— Far- meaning similar to the genus Edriophus from the Middle Ordovician. Discussion— Paredriophus is intermediate be- tween Middle Ordovician edrioasterids, including Edrioaster and Edriophus, and the Middle Cam- brian Totiglobus. It is closest to the former genera but differs from these in having a more elongate thecal shape with straight ambulacra and a short recurved lower theca ("resting zone" of Bell, 1976a). Paredriophus has a similar thecal shape and ambulacral distribution to Totiglobus, but the latter taxon has slightly imbricate interambulacral plating and small secondary cover plates and is attached by a small button-shaped adhesion disc rather than an attachment collar. It is not known if Paredriophus had a differentiated basal plate ring above the collar, but judging from related taxa we suspect that it did. Paredriophus elongatus, new species Figures 4-6 Diagnosis— Edrioasterids with elongate theca having L/W value about 1.33; ambulacra appar- ently straight, extending nearly down sides of theca for most of their length; thecal plates finely pitted; attachment collar fairly short with tiny imbricate plates, not hidden by theca above. Material and Description— Eight specimens available for study; five nearly complete thecae on one slab, most of these about same size, four up- right and vertically distorted, one on its side (ho- lotype) with part of collar exposed; whereas some thecal areas well preserved, exposed surfaces (downward-facing originally?) extensively corrod- ed. Two small poorly preserved specimens, orig- inally associated on small slab but now separate, are tentatively referred to this species. One isolated larger theca crushed with oral surface jumbled, aboral ambulacra and collar on opposite side bet- ter preserved. Theca bud-shaped, holotype thecal length about 20 mm without attachment collar, width about 1 5 mm (distorted by partial crushing), L/W value now about 1.33, original value perhaps 1.4-1.5, max- imum diameter about % way down theca; separate paratype pe 52683 approximately 50% larger, pre- served width now 34 mm (badly crushed). Most thecal plates of moderate thickness (not as thick as those of Edrioaster and Edriophus) except for attachment collar, fine-pitted ornament preserved only in few areas. Ambulacra long, wide, raised; straight in holo- type and paratype pe 52686, curved slightly clock- wise in crushed paratypes pe 52682-52685; con- stant width of about 4.0 mm in holotype for most of length, bluntly tapering near tips. Oral area poorly preserved on most specimens except paratype pe 52682; oral plates nondiffer- entiated, similar to and continuous with cover plates, shape and arrangement essentially that of Edriophus levis (see Bell, 1976a, text Fig. 2a). Hy- dropore poorly exposed in paratype pe 52683, ap- parently an elongate slit shared and bisected by CD interradial frame plate and right posterior hy- dropore plate; secondary oral cover plate separat- ed from oral area by lateral floor plate extension; second paratype pe 52682 apparently lacking sec- ondary hydropore plate, instead hydropore slit shared by CD interradial frame plate and adjacent floor plate, well separated from oral area. Cover plates arranged in simple alternating bi- Fig. 4. Paredriophus elongatus, n. gen. and sp. A, Paratype pe 52682, oral area, compare to drawing in Figure 5. Scale bar = 1 mm. B, C, Holotype pe 5268 1 , showing portion of plate collar (B) and ambulacrum and interambulacrum immersed in water (C). Scale bars = 1 mm. D, Paratype pe 52686, crushed lower surface, large specimen showing attachment surface of plate collar, straight ambulacra. Scale bar = 5 mm. E, Holotype pe 52681 (right center) and paratypes pe 52682-52685 cluster in near life position. Scale bar = 5 mm. 14 FIELDIANA: GEOLOGY GUENSBURG AND SPRINKLE: EDRIOASTEROIDEA 15 Fig. 5. Paredriophus elongatus, n. gen. and sp., oral area of paratype pe 52682 showing that basic plating ar- rangement is similar to that of the Middle Ordovician Edrioaster and Edriophus; shifting of plates has disrupted plating patterns around the A ambulacrum, cover plates have shifted over floor plate lateral extensions, and the hydropore is not preserved; dashed lines are inferred plate boundaries. Scale bar = 1 mm. series, nearly fiat, quadrangular, nearly twice as long as wide over most of ambulacral length, gent- ly sinuous perradial suture, numerous small gran- ular ossicles along well-preserved perradial suture and extending to oral area of holotype. Only exterior abradial portions of floor plates exposed, concave, leading up to cover plates above in one-to-one arrangement, exposed portion vary- ing in width, averaging about half width of adja- cent cover plates. Periproct poorly known, exposed only in para- type pe 52683, located about halfway down theca near center of posterior interray, preserved as ra- diating lath-shaped plates approximately 2 mm in diameter. Interambulacral regions relatively narrow com- pared to Edriophus, flat to slightly concave in slightly distorted holotype, approximately 2.5 times longer than wide, containing approximately 45 tesselate plates on best side of holotype. Lower theca below ambulacra not exposed in most specimens but no evidence of plate ring ob- served; holotype and largest paratype showing short collar of numerous, small, thin, squamose plates, diameter of collar approximately % of thecal di- ameter above, in holotype, collar about 12 mm wide with an exposed length of about 6 mm, basal disc apparently fully plated in largest paratype. Occurrence— Five of the eight specimens as- signed to this species, pe 52681-52685, are clus- 16 FIELDIANA: GEOLOGY Fig. 6. Lateral reconstructed view of Paredriophus elongatus, n. gen. and sp., based primarily on holotype pe 52681 and paratype pe 52683, showing elongate bud-shaped theca and straight ambulacra, thecal shape is similar to Totiglobus from the Middle Cambrian; attachment collar length and shape are uncertain, but collar was likely short as shown. Scale bar = 1.5 mm. tered together on a thin calcarenite bed found by Colin Sumrall. Shale covers the calcarenite sur- face, obscuring the exact nature of attachment, but four of the specimens remain erect and in their original position. The single large loose specimen was found separately and preserves the basal disc and collar. The two smaller specimens add little, if any, additional information. The stratigraphic horizon for these fossils is the uppermost trilobite zone E, probably in the beds immediately over- lying "Hintze's Reef" in the basal ledge-forming limestone member of the Fillmore Formation, Middle Ibexian (latest Tremadocian), Lower Or- dovician (Hintze, 1973). Most specimens were found in fill dumped along the south side of U.S. Routes 6 and 50 just east of largest roadcut (col- lection locality 4 of Braithwaite, 1976) where "Hintze's Reef" is exposed at Skull Rock Pass; GUENSBURG AND SPRINKLE: EDRIOASTEROIDEA 17 two fragmentary specimens were found on a small slab from similar dumped fill along the north side of Routes 6 and 50 to the west of the roadcuts. The 6-50 east locality is in the SW SW, sec. 29 (unsurveyed), T20S, R13W, about 86 km (54 mi) southwest of Delta, Millard County, western Utah, USA. Specimens Studied— Holotype fmnh pe 5268 1 , paratypes pe 52682-52689. Etymology— From the Latin elongatus, mean- ing prolonged or elongate, in reference to the thecal shape. Discussion— See Discussion under Genus Par- edriophus. Edrioasterid Species Indeterminate Discussion— A number of partial edrioasterid specimens were recovered from three horizons in the middle Fillmore Formation. Disarticulated edrioasterid debris is also common throughout much of this part of the section but can be rec- ognized only with close inspection (Fig. 7G). None of the partial specimens can be assigned to genus with confidence. Specimens from each of the three productive horizons differ in details, and multiple species appear to be represented. Despite the poor preservation, the specimens provide important in- formation regarding edrioasterid morphology, on- togeny, and paleoecology. Each of the three oc- currences are described and discussed separately below. "Giza Peak" Megaripple Group Figures 7A, D Material and Description— This group is represented by three partial specimens, two of which provide significant information. One is a large flattened individual with much of the oral surface preserved, but only parts of two ambulacra and one interambulacrum are well exposed; the second specimen is a well-preserved interior of the oral and adjacent areas. Theca large, flattened, par- tial specimen 43 mm wide, plates relatively thin (as compared to Edrioaster or Edriophus) with coarse pustulose ornament, ambulacra long, wide, nearly parallel-sided in midsection, curved coun- terclockwise in one example; oral frame a rigid raised ovoid funnel as viewed from interior, ap- parently composed of five radial and five inter- radial elements, posterior lip opening a low notch, stone canal passageway a small elliptical opening along the right posterior margin of the oral frame, ambulacral cover plates arranged in single alter- nating biseries, approximately 1 .8 times wider than long over midsection of ambulacrum, tiny gran- ular plates along perradial suture, floor plate ex- tensions forming inclined surfaces abradial to cov- er plates, approximately xh width of adjacent cover plates, biserial floor plates forming inverted low V shape as viewed from below, sutural pores large, elliptical. Discussion— The large size of these fossils sug- gests they were adults. The counterclockwise am- bulacral curvature and coarse pustulose ornament are suggestive of Edrioaster, but the relatively thin thecal plates and tiny granular plates along the perradial suture are more like those of Paredrio- phus. The stone canal passageway is proportion- ally smaller than that of Edriophus (see Bell, 1976a, PI. 61). Occurrence— All three specimens were asso- ciated on the surface of a megaripple bed. None are attached, nor are any of the associated crinoids, suggesting transportation prior to burial. The col- lecting horizon is designated the "Giza Peak" megaripple bed and is in the lower part of the light gray ledge-forming member about 251 m above the base of the Fillmore Formation, trilobite zone G-2, Middle Ibexian (basal Arenigian), Lower Or- dovician. The collecting locality is in the NW NE NW, sec. 25 (unsurveyed), T20S, R14W, northern Ibex area, House Range, Millard Co., western Utah, USA. This horizon has also produced the Lam- Fig. 7. Edrioasterid spp. indet. Scale bars = 2 mm. A, D, "Giza Peak" megaripple group. A, pe 52690, interior oral surface; D, pe 5269 1 , partial specimen showing counterclockwise ambulacral curvature, adjacent interambulacrals, and pustulose ornament. B, C, E, F, "Windy Point" hardground group. B, pe 52693, oral surface of poorly preserved large specimen. C, pe 52694, interior of lower theca. Note central opening for plate collar. E, pe 52695, extensively corroded juvenile showing rapidly tapering ambulacra and oral frame plates. F, pe 52696, relatively well-preserved juvenile showing large interradial oral frame plate, rapidly tapering ambulacra, and (?)pustulose ornament. G, pe 52717, isolated interradial oral frame plate, Pyramid Section of Datillo (1993). FIELDIANA: GEOLOGY GUENSBURG AND SPRINKLE: EDRIOASTEROIDEA 19 pteroblastus specimen at the "Windy Point North" locality nearby. Specimens Studied— The three specimens are fmnh pe 52690-52692. "Windy Point" Hardground Group Figures 7B, C, E, F Material and Description— Hypodigm rep- resented by 1 1 partial to nearly complete speci- mens; 4 are poorly preserved adults with upper parts of thecae mostly to completely stripped away, the remaining specimens are juveniles, most of which remain partly to nearly completely buried in indurated matrix; preservation of all specimens is typically poor because of calcite overgrowths and/or etching. Theca up to 19 mm in diameter in largest partial specimen, juveniles with mini- mum diameter of 5 mm; plates apparently thick, with pustulose ornament on interambulacrals, partial ambulacra in one specimen straight or slightly curved, parallel-sided in midsection; floor plates biserial with sutural pores; recurved lower theca beyond ambulacra consists of numerous small, tightly sutured plates, sutures slightly in- clined, basal ring with raised lip surrounding non- plated circular central opening; juveniles with nearly hemispherical upper surfaces, oral area large, oral frame with both radial and interradial ele- ments, much larger than adjacent floor plates, oral cover plates apparently thin, arranged as in adult edrioasterids, ambulacra rapidly tapering, con- sisting of as few as six or seven floor plate pairs; interambulacra triangular, with few plates, prox- imal interambulacra very large, contacting inter- radial frame plate and several floor plates. Discussion— These edrioasterids provide the first information regarding edrioasterid ontogeny. The specimens remain attached to a hardground even though upper surfaces of larger individuals were removed prior to burial (see Brett & Liddell, 1978, for a similar occurrence). The ontogeny of juvenile edrioasterids followed a progression sim- ilar to that of isorophids (Bell, 1976b): few plates, a large oral area, and rapidly tapering ambulacra. The morphologic information available in these specimens is scant and could be referable to any Early or Middle Ordovician edrioasterid genus. Occurrence— All specimens were found by Guensburg in close association over a total area of less than 0.5 m2 on a hardground designated the "Windy Point" hardground. A few crinoid fragments also occur in association with the ed- rioasteroids. The horizon and age are as follows: just above the base of the brown slope and ledge member (Hintze, 1973), about 314 m above the base of the Fillmore Formation, in trilobite zone G-2, Middle Ibexian (lower Arenigian), Lower Or- Ordovician. The "Windy Point" hardground lo- cality is on a steep ridge in the SW SE NE, sec. 25 (unsurveyed), T20S, R14W, northern Ibex area, House Range, Millard Co., western Utah, USA. Specimens Studied— The specimens are cata- logued as fmnh pe 52693-52703. "Giza Peak" Mound Specimen Material and Discussion— This single partial specimen preserves articulated interambulacral plates and adjacent parts of one ambulacrum. It differs from other edrioasterids from the middle part of the Fillmore in having smooth plates. It is preserved on a localized, high-relief, Calathium- stromatolitic mound (see Church, 1974). Occurrence— The single specimen is from "Church's Reef"; discontinuous mounds extend across most of the Ibex area at this horizon. Sev- eral partial iocrinid fragments were found in as- sociation with this specimen. "Church's Reef" is in the upper part of the slope-forming shaly silt- stone member (Hintze, 1973) about 240 m above the base of the Fillmore Formation, trilobite zone G-2, Middle Ibexian (lowest Arenigian), Lower Ordovician. The "Giza Peak" locality is in the NW NE NW, sec. 25 (unsurveyed), T20S, R14W, northern Ibex area, House Range, Millard Co., western Utah, USA. Specimen Studied— The single specimen is cat- alogued as fmnh pe 52704. Suborder EDRIOBLASTOIDINA Fay, 1962 (nomen trans I., emend.) Diagnosis— Edrioasterid edrioasteroids with bud-shaped to turret-shaped theca, interradial oral frame plates usually fused to floor plates forming deltoids, five interradial oral cover plates expand- ed meeting centrally over the mouth, hydropore 20 FIELDIANA: GEOLOGY not identified with certainty, possibly pore through deltoid, sutural pores between floor plates shifted abradially. Discussion— This suborder is emended to re- ceive both traditional edrioblastoids and cyatho- cystids. It ranges in age from Late Cambrian to Early Devonian. Family CYATHOCYSTIDAE Bather, 1899 (emend.) Diagnosis— Edrioblastoids with turret-shaped theca and nearly flat to slightly domal oral surface, oral plating reduced with deltoids occupying entire interambulacra, oral cover plates cover much of oral surface, ambulacra rapidly tapering, collar ex- panded to form cylindrical sides and bottom of theca, basal ring surrounds margin of oral surface of certain species. Discussion— Cyathocystids are remarkably widespread, particularly given their low diversity of only Cyathocystis and Rhenopyrgus. These two genera differ considerably in construction of the elongate thecal structures and consequently we have assigned them to separate subfamilies. Cyatho- cystis is characterized by fusion of the entire side and bottom portion of the theca into a solid cup, whereas in Rhenopyrgus the sides of the theca con- sist of imbricate plates and the base of the theca is expanded to form a coriaceous sac. Cyathotheca Jaekel, 1927, is closely related to or more likely a junior synonym of Cyathocystis, differing from the latter only in lacking a basal ring. This apparent difference could be purely preservational (Fig. 17D). This group ranges in age from Middle Or- dovician to Early Devonian. Subfamily CYATHOCYSTINAE Bather, 1899 (nomen transl., emend.) Diagnosis— Cyathocystids with fused sides and bottom of the turret-shaped theca. Discussion— Cyathocystinids as defined here are equivalent to the family Cyathocystidae of Bather, 1 898, and the order Cyathocystida, Bell, 1 975 (see Bockelie & Paul, 1983). The group ranges in age from Middle to Late Ordovician. Subfamily RHENOPYRGINAE Holloway and Jell, 1983 (nomen transl., emend.) Diagnosis— Cyathocystids with imbricate sides of theca and a distal coriaceous sac. Discussion— Rhenopyrginids are as yet repre- sented only by Rhenopyrgus itself. This subfamily has been discussed at length by Holloway and Jell (1983, pp. 1002-1004) as their family Rhenopyr- gidae. The group ranges from the Late Ordovician to Early Devonian in age. Family ASTROCYSTITIDAE Bassler, 1935 (emend.) Diagnosis— Edrioblastoids with a bud-shaped theca, ambulacra raised above level of surround- ing theca, interambulacral plates arranged in cir- clets with five basals below, theca elevated by a stalk with plate mosaic or columnals. Discussion— Only three genera of edrioblas- toids are known: Astrocystites, Cambraster, and Lampteroblastus. Rosznov (written comm., Jan- uary 1 993) has reported two other genera from the Early Ordovician, but to our knowledge these are not described. "Totiglobus" lloydi from the Mid- dle Cambrian of Utah could be a primitive ed- rioblastoid, but we prefer not to assign it at this time because of poor preservation and nonspe- cialized construction. Aside from this genus, ed- rioblastoids range in age from Late Cambrian to Late Ordovician. Genus Lampteroblastus Guensburg and Sprinkle, new genus Type Species— Lampteroblastus hintzei Guens- burg and Sprinkle, new species. Diagnosis— Astrocystitid edrioblastoid with elongate, cylindrical theca; ambulacra straight, short, rapidly tapering, tips curled a short distance down from summit; cover plates biserial, oral cov- er plates nondifferentiated; interambulacra occu- pied by single triangular deltoid; six alternating plate circlets in mid-to-distal theca; no respiratory pores visible; stalk well defined, narrow, tapering, composed of cuneate plates forming a chevron pattern. GUENSBURG AND SPRINKLE: EDRIOASTEROIDEA 21 Occurrence— Early Ordovician, western Utah, USA. Etymology— From the Greek lampteros, torch, lamp, and the Greek blastos, bud, for the elongate bud-shaped theca. Discussion— La mpteroblastus can easily be dis- tinguished from other edrioblastoids. The Middle Ordovician Astrocystites has a more rounded bud shape with ambulacra extending well down the sides of the theca, expanded interradial oral cover plates, parabolic deltoids, multiplated interam- bulacra, fewer theca plates with only two plate circlets below the ambulacra, and respiratory pores at triple junctures of interambulacral plates. The apomorphies of Lampteroblastus such as highly elongate theca, triangular deltoids, and short am- bulacra differ greatly from Astrocystites, and we conclude these two genera are not closely related within the astrocystitids. The Late Cambrian Cambroblastus is far more primitive than Lamp- teroblastus and can be identified by its longer am- bulacra extending well down the thecal sides, bi- serial nonfused ambulacral floor plates, multi- plated interambulacra, three plate circlets below the ambulacra, and irregularly plated stalk. Cam- broblastus is a plausible progenitor of both Astro- cystites and Lampteroblastus. The nonspecialized cover plate arrangement of Lampteroblastus is most like that of Cambroblastus. Beyond the edrioblas- toids proper, cyathocystids also have large trian- gular deltoids generally similar to those of La mpteroblastus. Lampteroblastus hintzei, new species Figures 8A-D, 9 Diagnosis— Same as that of genus. Material and Description— The only speci- men available for study is the complete and well- preserved holotype; it is preserved on its side on a small slab with the CD interray, two ambulacra and part of the oral surface buried in hard matrix. Holotype theca 16 mm in length and maximum 9 mm wide 3 mm below summit; theca nearly cylindrical, pentagonal in oral view, oral region large, nearly as wide as each ambulacrum, distal theca conical, stem facet small; all plates tesselate, lower thecal plates heavily ridged. Ambulacra five, short, 7 mm long, straight, raised above deltoids, arranged in 2-1-2 pattern, rapidly tapering away from oral area, confined to near thecal summit; oral cover plates not differentiated, five interradial orals apparently meet centrally over mouth, approximately 20 cover plates per am- bulacrum, arranged in single alternating biseries, meeting at sinuous perradial suture, approximate- ly 4 times wider than long proximally, becoming longer than wide at ambulacral tips; ambulacral groove exposed along broken ambulacrum tip only, apparently deep, V-shaped. Large triangular deltoids fill interambulacral ar- eas, 3.0 mm long and 4.3 mm wide in two exposed areas, nearly flat except for medial indentation; medial and lower theca of six alternating plate circlets in radial and interradial positions, appar- ently five plates per circlet; three circlets in radial position stacked, proximal radial circlet small trapezoidal plates immediately below ambulacra in open circlet, followed distally by larger octag- onal to heptagonal plates in complete to slightly open circlet, and then larger heptagonal plates in open circlet; three interradial plate circlets sepa- rated (orally-aborally), adoral circlet open, of in- verted triangular or pentagonal plates, next aboral circlet open, of slightly larger quadrangular plates with prominent X-ridges, aboralmost circlet of large, tall, pentagonal plates (basals), forming con- ical thecal base; hydropore and periproct not ex- posed. Only short proximal stem segment preserved, of small smooth wedge-shaped plates arranged in crude chevrons. Occurrence— The single specimen found by Guensburg is from the top of the "Giza Peak" megaripple bed at the "Windy Point North" lo- cality of our field notes. This bed occurs locally 25 1 m above the base of the Fillmore in the lower Fig. 8. A-D, Lampteroblastus hintzei, n. gen. and sp., holotype pe 52705. A, Complete specimen in lateral view, compare to drawing in Figure 9A. Scale bar = 1 mm. B, Oblique view of summit; compare to drawing in Figure 6B. Scale bar = 1 mm. C, Proximal stem segment with chevron-shaped plates. Scale bar = 0.5 mm. D, Complete specimen immersed in water. Note triangular deltoids. Scale bar = 2 mm. E, F, Deltadiscus superbus, n. gen. and sp., holotype pe 52706. E, Entire specimen, periproct just below oral area (see Fig. 10A for details). Scale bar = 2 mm. F, Detail of ambulacrum (see Fig. 10B for details). Scale bar = 1 mm. 22 FIELDIANA: GEOLOGY GUENSBURG AND SPRINKLE: EDRIOASTEROIDEA 23 part of the light gray ledge-forming member of the Fillmore Formation, trilobite zone G-2, Middle Ibexian (basal Arenigian), Lower Ordovician (see Hintze, 1973). This locality is in the SE NW NE, sec. 25 (unsurveyed), T20S, R14W, Millard Co., western Utah, USA. Specimen Studied— The holotype is catalogued as fmnh pe 52705. Etymology— Named for Lehi F. Hintze, who studied and recognized the importance of Early Ordovician rocks and their faunas in western Utah. The stratigraphic framework erected by Dr. Hintze was of invaluable help in this research. Discussion — See Discussion under Genus Lampteroblastus. Order ISOROPHIDA Bell, 1976 Family AGELACRINITIDAE Chapman, 1860 (emend.) Diagnosis— Isorophida with domal or clavate theca, several (minimum of four) differentiated oral cover plates, hydropore bordered by few to several plates, ambulacra nearly always thin, slightly raised above or even with adjacent interambulacra, am- bulacral cover plates rarely forming simple alter- nating biseries, or nearly always a double alter- nating biseries or more complex cyclic biseries, cover plates with internal extensions, no intrathe- cal cover plate passageways, ambulacral floor plates usually abutting along vertical suture, periproct valvular or semivalvular. Discussion — The family Agelacrinitidae (Chapman, 1860) is the oldest family group name proposed for the included genera and was defined originally on all known edrioasteroids. Later au- thors have conserved the name but restricted the scope of this taxon to Agelacrinites and its close relatives. As conceived here, the Agelacrinitidae Fig. 9. Lampteroblastus hintzei, n. gen. and sp., ho- lotype pe 52705, plate cracks indicated by stippling. Scale bar = 1 mm. A, Lateral view, triangular deltoids filling interambulacra, lower theca dominated by plate circlets with trusswork of prominent ridges superficially resem- bling the pattern found on certain camerate crinoids such as Lampterocrinus, proximal stem with wedge-shaped plates. B, Oblique view of thecal summit and oral area. Note primary orals meeting centrally over mouth and simple cover plating. 24 FIELDIANA: GEOLOGY is essentially equivalent to the suborder Isoro- phina Bell, 1976, or the subfamily Isorophinae Bell, 1976, of Smith (1985). We prefer this no- menclature because it conserves existing termi- nology and most reflects the close relationship of all included species (see Edrioasteroid Phylogeny). The agelacrinitids are by far the most successful of edrioasteroid clades and range in age from the Early Ordovician to Late Pennsylvanian. Genus Deltadiscus Guensburg and Sprinkle, new genus Type Species— Deltadiscus superbus Guensburg and Sprinkle, new species. Diagnosis— Agelacrinitid edrioasteroid with flat-topped domal theca, small oral area with close 2-1-2 pattern, thin, straight ambulacra, cover plates irregular-shaped but arranged in simple al- ternating biseries; periproct with elongate plates in semivalvular arrangement; interambulacra broad, with numerous thin squamose plates, high- ly imbricate zone extending short distance beyond ambulacral tips, covering attachment structure. Occurrence— Early Ordovician, western Utah, USA. Etymology— Named for the town of Delta, Utah, our base of operations for our field work in the Ibex area. Discussion— The new genus is provisionally as- signed to and arguably the most primitive taxon of agelacrinitids. Difficulties in evaluating this tax- on result from the lack of or poor information regarding oral cover plate, hydropore, and periph- eral rim construction and the fact that it retains primitive features lost by more advanced agela- crinitids such as nonuniform cover plates and semivalvular periproct. Alternatively, the thin ambulacra with no indication of intrathecal cover plate passageways suggest agelacrinitid affinities. The imbricate interambulacrals and thecal elon- gation zone beyond the ambulacra are derived and contrast sharply with the ambulacral construc- tion. Consequently, we are unsure as to what later taxa, if any, Deltadiscus could have been ancestral to. The general size and distribution of the am- bulacra of Deltadiscus are similar to primitive ed- rioasteroids such as Stromatocystites or Edrio- discus, but these taxa differ in many details, in- cluding low domal shape, irregular cover plates, and tesselate interambulacra. The Late Cambrian iso- rophids Chatsworthia and Hadrodiscus differ sub- stantially in having erect ambulacra with thick biserial cover plates like those of lebetodiscids. Among advanced agelacrinitids, Cooperidiscus from the Devonian has extremely narrow ambu- lacra like Deltadiscus, but this taxon is also poorly known and has curved ambulacra, and even the cover plate arrangement cannot be discerned, so comparison is very limited. Typical agelacrinitids such as Isorophusella from the Middle Ordovician differ from Deltadiscus in having a low domal shape, much wider ambulacra and larger oral area, uniform cover plates arranged in a double biseries, and a valvular periproct. Deltadiscus superbus, new species Figures 8E, F, 10 Diagnosis— Same as that of genus. Material and Description— Only holotype known; thecal diameter 18 mm, slightly etched and flattened but complete and remarkably well preserved; theca subpentagonal in outline, domal with raised sides and slightly convex top in life; ambulacra long, thin, 1 mm wide just beyond oral area, straight, slowly tapering, slightly arched (pushed down distally to below level of interambs by flattening), oral area small so that 2-1-2 pattern of ambulacral juncture only vaguely defined, oral plating obscure, number and distribution of plates uncertain, hydropore oral probably small, oral frame not exposed; ambulacral cover plates form single alternating but nonuniform biseries, sharply oscillating perradial suture extends nearly full width of ambulacra, floor plates and features of ambu- lacral groove interior unexposed, assumed to be solid without cover plate passageways; periproct small, centrally situated in posterior interambu- lacrum, 1.8 mm in diameter, composed of ap- proximately 15 irregular lath-shaped plates with elongate axes radiating from center; interambu- lacral areas large, formed by numerous small, thin imbricate plates (overlapping in oral direction), approximately 30 plates across interambulacrum at tips of ambulacra, similar plates continuing dis- tally well beyond tips of ambulacra and curling over the thecal edge as preserved, forming short extendable pedunculate zone in life; attachment structure unexposed but presumably included a peripheral rim. Occurrence— The single specimen collected by Sprinkle is from 9 m above the base of the cal- GUENSBURG AND SPRINKLE: EDRIOASTEROIDEA 25 Fig. 10. Deltadiscus superbus, n. gen. and sp., ho- lotype pe 52706. Scale bar = 1 mm. A, Periproct with numerous irregular lath-shaped plates and surrounding interambulacrals. B, Cover plate arrangement of distal B ambulacrum showing poorly organized alternating bi- series, perradial suture with strong zigzag pattern. carenite member, trilobite zone H, Fillmore For- mation, Upper Ibexian (Lower Arenigian), Lower Ordovician. It occurs on a moderately well-sorted calcarenite (grainstone) that appears to be largely composed of echinoderm debris. Well-sorted cross- bedded grainstones dominate this part of the Fillmore section. No other well-preserved macro- fossils were associated with this specimen. The locality is on the measured section designated as Square Top (Hintze, 1973) along the west flank of the southern House Range, in the NW SE SE, sec. 3 1 , T2 1 S, R 1 3W, approximately 80 km southwest of Delta, Millard Co., western Utah, USA. Specimen Studied— The holotype is fmnh pe 52706. Etymology— Superbus refers to the outstand- ing preservation of the only known specimen, par- ticularly given the highly agitated conditions that characterized paleoenvironments through the as- sociated interval of the Fillmore Foundation. Discussion— See Discussion under Genus Del- tadiscus* Family LEBETODISCIDAE Bell, 1976 (nomen. transl., emend.) Diagnosis— Isorophid edrioasteroids with domal to turret-shaped theca, three primary oral cover plates, hydropore structure typically bound- ed by few plates, thick ambulacral cover plates arranged in a single alternating biseries with in- trathecal and interthecal extensions, sutural pas- sageways between cover plates, ambulacral floor plates imbricate or lost, periproct with poorly or- ganized plating. Discussion— The family Lebetodiscidae as de- fined here is essentially equivalent to the suborder Lebetodiscina Bell, 1976, and defined in Bell (1980), where pyrgocystids were incorporated. The definition is modified slightly to include new find- ings regarding pyrgocystid morphology. Lebeto- discids range from the Late Cambrian to the Late Devonian. * A second specimen referable to this taxon was dis- covered by Colin Sumrall while this paper was in press. It is 30 mm in diameter, and portions of four interam- bulacra, the distal tips of two ambulacra, and much of the peripheral rim are preserved intact. The thecal mar- gin is ragged though well preserved, suggesting this con- figuration in life. The peripheral rim consists of six or seven imbricate plate rows. Peripheral rim plates merge with and are difficult to distinguish from adjacent inter- ambulacrals. The proximal circlet is not significantly thickened, unlike most isorophids. It occurred higher in the section than the holotype, on a hardground 3 cm above the Calathium reef, Calathium calcisiltite mem- ber, trilobite zone I, Fillmore Formation. The locality is in the NW, sec. 29, T21S, R13W, Millard Co., Utah. The specimen is designated as para type fmnh pe 527 19. 26 FIELDIANA: GEOLOGY Subfamily LEBETODISCINAE Bell, 1976 (nomen transl.. emend.) Diagnosis— Lebetodiscids with domal theca, projecting and usually rounded ambulacra, usually two pairs of lateral shared cover plates and sec- ondary orals, hydropore structure opening along adradial suture line of proximal part of ambula- crum V, composed of both interambulacral and ambulacral plates, cover plates thick, floor plates present, periproct flush or slightly raised, narrow peripheral rim, sometimes spinose oral surface. Discussion— The subfamily Lebetodiscinae is equivalent to the Lebetodiscidae Bell, 1976, but it is emended to allow for separation of pyrgocys- tinids (see below). Subfamily CARNEYELLINAE Bell, 1976 (nomen transl.) Diagnosis— Lebetodiscids with domal theca, slightly raised ambulacra, oral area lacking sec- ondary oral plates or shared cover plates, plates covering ambulacral and hydropore areas mod- erate thickness, hydropore in right posterior oral region, large hydropore oral, periproct even with thecal surface. Discussion— This subfamily is equivalent to the family Carneyellidae Bell, 1 976, and is again mod- ified to distinguish the pyrgocystinids. Subfamily PYRGOCYSTINAE Kesling, 1967 (nomen transl., emend.) Diagnosis— Lebetodiscids with domal to tur- ret-shaped theca; elongated pedunculate zone in some taxa, reduced oral area and short petalloid ambulacra, hydropore structure along adradial su- ture line of ambulacrum V, with single thick mas- sive hydropore oral, ambulacral cover plates erect, thick, taller than wide with summits flattened, club- shaped, lateral hood plates, ambulacral floor plates lacking, periproct conical, and oral surface often spinose. Discussion— General similarity between pyr- gocystinids and the lebetodiscinid Cystaster was first noted by Kesling (1967, p. 201); later both Bell (1980, p. 160) and Holloway and Jell (1983, p. 1012) independently made similar observations linking pyrgocystinids with lebetodiscids. We agree; the parsimony analysis mapped pyrgocystinids branching from a lebetodiscid ancestor (Figs. 1, 2). They were in many ways the most specialized of lebetodiscids. Unique characteristics of the sub- family include the shape of the cover plates, lack of floor plates, and the addition of lateral hood plates; however, not all pyrgocystinids are turret- shaped, and this readily recognized characteristic is not diagnostic. Pyrgocystinids share similarities with lebetodiscinids such as Cystaster or Strept- aster, including the elevated ambulacra with great- ly thickened spine-bearing cover plates, tall nar- row ambulacral tunnel, and diminutive oral area. The ambulacral floor plates of Streptaster are greatly reduced, and this trend is carried to its extreme in pyrgocystids, where they are lost en- tirely (see Bell, 1976, pi. 9). Belochthos, another lebetodiscinid, has short petalloid ambulacra gen- erally similar to those of pyrgocystinids. Chats- worthia, from the Late Cambrian, branched as the sister group to lebetodiscinids in many trees in the parsimony analysis. It has greatly thickened cover plates arranged in an alternating biseries reminis- cent of pyrgocystinids. Smith and Jell ( 1 990, p. 741) noted the similarity of the cover plate plating of the lebetodiscinid Foerstediscus to that of Chat s- worthia. The extraordinarily revealing specimens of Ar- chaepyrgus and to a lesser extent Fanulodiscus provide the first opportunity to interpret pyrgo- cystinid functional morphology based on nearly complete and well-exposed oral morphology. Pre- vious descriptions of Pyrgocystis species published over the past 80 years were based on poorly pre- served material that resulted in sketchy definition of pyrgocystid characteristics and entanglement with the superficially similar but only distantly related Rhenopyrgus (see Regnell, 1 966; Holloway & Jell, 1983; Smith, 1985). Rhenopyrgus mor- phology has recently been used as the basis for defining pyrgocystinid morphology and relation- ships (Smith, 1985, p. 731). Holloway and Jell (1983) recognized the disparate nature of pyrgo- cystids and rhenopyrgids and placed them in sep- arate families. The parsimony analysis supports this finding and placed these two groups in iso- rophid and edrioasterid clades, respectively (Figs. 1 , 2). Pyrgocystis specimens often consist of the pedunculate zone only, and those preserving the GUENSBURG AND SPRINKLE: EDRIOASTEROIDEA 27 oral surface often have a dense covering of pro- tective spines or are moldic; consequently, this taxon remains poorly known (see Fig. 12C). Ar- chaepyrgus specimens not only provide a detailed external morphology but also many details of the thecal interior. The oral surface of pyrgocystinids is unique among edrioasteroids. It is dominated by short petalloid ambulacra (Figs. 1 1 A, B, 1 2C) in a com- pact configuration. This trend is fully developed in Pyrgocystis, where the exterior oral area is de- pressed and tiny so that each ambulacrum is es- sentially a separate disjunct structure in some ways reminiscent of the condition found in certain ad- vanced fissiculate blastoids (Fig. 12C). The am- bulacra in pyrgocystinids are constructed of tall, slab-like, biserial cover plates with planar cover plate crests that project well above the surrounding interambulacral areas. Internal cover plate pas- sageways form gaps between successive cover plates, extend upward to near the cover plate sur- faces, and presumably housed ciliated tissues en- hancing feeding capacity and/or respiration (Bell, 1976a) (Fig. 12D). Cover plate extensions are ex- panded below (internally) both abradially and ad- radially. They meet perradially along a short su- ture, completely encircling the food groove. Presumably, rotation of cover plates through only a few degrees of arc facilitated feeding. Hood plates articulate with and support cover plates (Fig. 1 3); they are expanded at either end, and the resulting gaps could have enhanced respiration. In Fanu- lodiscus and Pyrgocystis^) petalus, hood plates are preserved in their original position and form a channelway surrounding the ambulacra (Hollo- way & Jell, 1983, Fig. 5, Fig. 18). Striations are found on the hydropore oral plate of Archaepyrgus and Pyrgocystis specimens (Figs. 1 7C, E). They are apparently a diagenetic artifact but, if not, indicate this plate was porous. Lebetodiscids, including most pyrgocystinids, possessed articulating spines. Spines are largely concentrated atop cover plate crests in Archaepyrgus, some Pyrgocystis species, and Epipaston. They attached to interambulacral/ pedunculate zone and peripheral rim plates in cer- tain taxa (see Holloway & Jell, 1983, Fig. 3; Guensburg, 1988, Fig. 8.3). Their function seems to have been primarily protective, but Holloway and Jell (1983) suggested they could also conceiv- ably have enhanced or directed feeding currents. Pyrgocystinids attached by a peripheral rim to hard surfaces, including skeletal fragments such as nau- tiloid conchs (Archaepyrgus, Epipaston), trilobite exuvae (Archaepyrgus, Pyrgocystis), brachiopod valves (Epipaston), or hardgrounds (Fanulodiscus, Archaepyrgus). Of the four genera included as pyrgocystinids, Pyrgocystis Bather and Archaepyrgus, n. gen., are cylindrical turret-shaped forms with a highly ex- tensible pedunculate zone. These forms were ca- pable of contracting to a considerable degree (Figs. 11D, 18). Fanulodiscus, n. gen., and Epipaston Holloway and Jell were domal forms capable of moderate shape change. As in other edrioasteroid clades, elongation potential among pyrgocystinids developed independently in a portion of the mem- ber taxa. Genus Archaepyrgus Guensburg and Sprinkle, new genus Type Species— Archaepyrgus anitae Guensburg and Sprinkle, new species. Diagnosis— Pyrgocystinid edrioasteroids with ambulacra relatively narrow and oral area large, anal pyramid a protruding cone of lath-shaped plates, and (?)sparse spine covering on oral surface; theca low, turret-shaped when contracted. Occurrence— Early Ordovician, western Utah, USA. Etymology— Archae from Latin meaning old or ancient and pyrgos from Greek meaning tower. Discussion— The genus most closely resem- bling Archaepyrgus is Pyrgocystis, whose mor- phology, as previously stated, is poorly known. Pyrgocystis has distinctly more petalloid ambu- lacra and a diminutive oral area (see Figs. 11,1 2C; Holloway & Jell, 1990, Fig. 5, for comparison), a smaller periproct, and more dense spination in some cases than Archaepyrgus. The oral area in Pyrgocystis has virtually been lost, so that the am- bulacra are in effect disjunct. The relatively narrow ambulacra and large oral area of Archaepyrgus are plesiomorphic. Among other pyrgocystids, Fan- ulodiscus, n. gen., and Epipaston Holloway and Jell can easily be distinguished from Archaepyrgus by their domal rather than turret shape and pro- portionately large peripheral rims. Archaepyrgus anitae, new species Figures 11, 12A,B, 13-16 Diagnosis— Same as that of genus. 28 FIELDIANA: GEOLOGY Material and Description— Description based on 10 specimens in varying stages of preservation, several remain attached; theca small, low, turret- shaped, ranging from 8 to 14 mm and averaging 1 1 .2 mm in width among five measurable speci- mens; partly collapsed holotype is 7 mm high and 8 mm wide, slightly contracted but undistorted paratype is 3 mm high, oral surface outline sub- pentagonal; ambulacra short with blunt rounded tips, meet centrally over mouth in pentameral symmetry (no obvious 2-1-2 pattern); oral area small, apparently with three primary cover plates; spines poorly preserved, attached to upper cover plate surfaces, apparently single spine per cover plate, no obvious spine bosses preserved, spines long, approximately 1.3 mm in largest partial ex- ample; hydropore with single large, extremely thick plate larger posterior to and bordering adradial suture line of proximal part of ambulacrum V, transverse striations preserved in weathered spec- imens, particularly paratype pe 52708, hydropore slit bordered by four cover plates of ambulacrum IV; ambulacral cover plates arranged in single al- ternating biseries, perradial suture forming narrow zigzag pattern, cover plates erect, slab-like, much wider than long, thick, approximately twice as high as wide, with club-shaped, flat-topped, vertical ex- tensions, slightly constricted medially, lower por- tion expanded transversely in both abradial and adradial directions, sutural passageways appar- ently opening below plate tops along sides of pro- jecting ambulacra, cover plates mutually articulate adradially across floor of ambulacral groove along short flat sutures, each cover plate articulates abra- dially with hood plates, ambulacral tunnel tall, narrow; hood plates articulate along abradial mar- gins of cover plates, elongate, medially constricted, hollow, apparently housing suspensory structures; interambulacral areas small, triangular, each with several thin squamose plates, seven or eight plates between ambulacral tips, merging distally into pe- dunculate zone plates; periproct large, conical, projecting well above thecal surface, of approxi- mately 20 elongate lath-shaped plates; peduncu- late zone of 23-30 rows of thin, wide, squamose, highly imbricate plates, obscuring and covering peripheral rim in contracted paratype pe 52717, peripheral rim best exposed in holotype, low (slightly inclined proximally) narrow peripheral rim, composed of three or four (?)imbricating cir- clets of tiny plates, proximal circlet not differen- tiated or enlarged. Occurrence— Ten specimens were available for study, all but two collected by Guensburg. The holotype and seven paratypes all remain attached to original sites; two to poorly preserved nautiloid steinkerns, one to a fragment of trilobite exuvae, and one to an intraclast in a hardground; other paratypes are attached to indeterminate surfaces on a light brownish gray wackestone with numer- ous trilobite fragments and a few graptolites. All but one specimen were found on or near a thin limestone bed in a predominantly shaly interval of the Calathium calcisiltite member, Fillmore Formation, 23 m below the top of the Fillmore, trilobite zone I; paratype pe 52717 was found ap- proximately 34 m below the top of the Fillmore in a more limestone-rich interval also in the Cal- athium calcisiltite member. Both occurrences are Upper Ibexian (Middle Arenigian), Early Ordo- vician in age. All specimens were collected near measured section H (Hintze, 1973) in the NW SW Fig. 11. Archaepyrgus anitae, n. gen. and sp. A, Holotype pe 52707, oblique view of partly extended specimen. Peripheral rim is attached to cephalopod steinkern. Scale bar = 2 mm. B, Paratype pe 52708, large, vertically crushed specimen. Scale bar = 2 mm. C, Paratype pe 52710, partly disrupted specimen showing many features of thecal interior. Scale bar = 1 mm. D, F, Paratype pe 52717, poorly preserved contracted specimen. D, Entire specimen attached to hardground; compare with reconstruction in Figure 1 5. Scale bar = 2 mm. F, End of much weathered ambulacrum showing cover plates that meet adradially. Scale bar = 0.5 mm. E, Paratype pe 527 1 2, complete specimen left largely unprepared to show spines (faint) in matrix. Scale bar = 2 mm. (page 30) Fio. 12. A, B, Archaepyrgus anitae, n. gen. and sp. A, Holotype pe 52707, oral surface showing large hydropore oral (upper center) and periproct above. Well-preserved ambulacrum at left is drawn in Figure 1 3A. Scale bar = 1 mm. B, Paratype 52710, disrupted specimen showing interior of one side of an ambulacrum at left, cover plate extensions broken. Ambulacrum is drawn in Figure 13B. Scale bar = 1 mm. C, D, Pyrgocystis sp., referred specimen 1221 TX30, Bromide Formation (Middle Ordovician) of Oklahoma. C, Specimen with spines partly removed showing short, strongly petalloid ambulacra. Scale bar = 1 mm. D, Enlarged oral view immersed in water showing sutural pores between cover plates. Scale bar = 0.5 mm. {page 31) GUENSBURG AND SPRINKLE: EDRIOASTEROIDEA 29 30 FIELDIANA: GEOLOGY GUENSBURG AND SPRINKLE: EDRIOASTEROIDEA 31 Fig. 13. Ambulacral morphology of Archaepyrgus anitae, n. gen. and sp. Scale bar = 1 mm. A, Holotype pe 52707, oblique view of C ambulacrum. Note erect ambulacral cover plates and articulating lateral hood plates. B, Paratype pe 527 1 0, interior view of ambulacrum showing cover plates, flat perradial articular facets with faint ligament pits above, followed by concave cover plate extensions with club-shaped summits. Note gaps between extensions forming cover plate passageways. 32 FIELDIANA: GEOLOGY Fig. 14. Reconstructed ambulacral segment of Archaepyrgus anitae, n. gen. and sp., in oblique view, primarily based on holotype pe 52707 and paratype pe 527 10. Note shape of ambulacral tunnel and relationship of hood plates to cover plates. Scale bar = 0.5 mm. NE, sec. 6, T23S, R14W, southwestern Ibex area in the southern Confusion Range, Millard Co., western Utah, USA. Specimens Studied— The holotype is pe 52707, and nine paratypes are pe 52708-52717. Etymology— Named for Anita Brosius of Cleveland, Ohio, for her assistance and good cheer in the field. Discussion— See Discussion under Genus Ar- chaepyrgus. Genus Fanulodiscus Guensburg and Sprinkle, new genus Type Species — Fanulodiscus crystalensis Guensburg and Sprinkle, new species. Diagnosis— Pyrgocystinid with small domal theca, ambulacra short, nearly straight-sided, not extending to peripheral rim, periproct small, cone- shaped with lath-shaped plates, well-differentiated wide peripheral rim. Occurrence— Middle Ordovician, Utah, USA. Etymology— Fan ulo from Latin meaning little temple, in reference to the flat-topped projecting ambulacra, and diskos from Greek meaning disc, for the general thecal shape. Discussion— Fa n ulodiscus is assigned to the pyrgocystinids based on the following character- istics: short petalloid ambulacra, small oral area, thick slab-like flat-topped cover plates, and the presence of lateral hood plates. The holotype of Fanulodiscus shows well the nature of the oral plating and the original positioning of the lateral hood plates. Virtually nothing is known of the interior construction. The obvious difference of Fanulodiscus from traditional pyrgocystinids is the lack of a pedunculate zone. The only other domal edrioasteroid that we assign to the pyrgocystinids is Epipaston Holloway and Jell, 1983, from the Silurian of Australia. This genus can readily be distinguished from Fanulodiscus by its wider, con- GUENSBURG AND SPRINKLE: EDRIOASTEROIDEA 33 Fig. 15. Reconstructed oral view of Archaepyrgus anitae, n. gen. and sp., with theca contracted, based primarily on paratype pe 52717. Plating at center of oral area is poorly known and indicated with dashed lines. Darkened depressed areas adjacent to ambulacra mark positions of hood plates that are largely obscured in this orientation. Scale bar = 2 mm. vex-sided petalloid ambulacra and heavy spines on the proximal circlet of the peripheral rim. Fanulodiscus crystalensis, new species Figures 17 A, B, 18 Diagnosis— Same as that of genus. Material and Description— The four speci- mens available occur on a small slab, and only the holotype preserves detail of the ambulacra, oral area, and periproct; theca small, diameter ranging from 7 to 10 mm, averaging 7.9 mm, theca prob- ably highly domal with projecting ambulacra in life but now collapsed; ambulacra five, petalloid, short, relatively narrow, straight-sided, with blunt tips; oral area small, with three primary oral cover plates, posterior primary oral largest; hydropore oral, situated in proximal posterior interambula- crum, thick, massive, with adradial plate margin 34 FIELDIANA: GEOLOGY ■1 S a 11 a g, X c = 42 4J . 3 d g C .S 00 C . O ? en ! = So <« IT* ♦-' ?< « ^ -s <3 Ci, ■8 i_ 55 3 O e ° ^ JO £ oo •B-£ 9 JS 5 o. 11 a: | c o GUENSBURG AND SPRINKLE: EDRIOASTEROIDEA 35 M 36 FIELDIANA: GEOLOGY Fig. 18. Oral surface of Fanulodiscus crystalensis, n. gen. and sp., holotype usnm 172048. Lateral hood plates are visible beside cover plates. Scale bar = 1 mm. Fig. 17. A, B, Fanulodiscus crystalensis, n. gen. and sp. A, Holotype usnm 172048 (left) and paratypes usnm 172049-172050 attached to hardground. Scale bar = 2 mm. B, Holotype. Note well-preserved oral surface with slab- like cover plates, lateral hood plates, and large hydropore oral plate. Drawing of this specimen appears in Figure 18. Scale bar = 1 mm. C, Archaepyrgus anitae, n. gen. and sp., paratype pe 52708, hydropore oral with striations (above) and periproct (below). Scale bar = 1 mm. D, Cyathocystis sp., pe 527 18, Kimmswick Limestone (Middle Ordovician) of Missouri. Cover plates are largely missing, revealing intrathecal passageways through deltoids. Scale bar = 1 mm. E, Pyrgocystis sp., referred specimen 1279TX333, Bromide Formation (Middle Ordovician) of Oklahoma, disartic- ulated, showing hydropore oral with striations (lower center). Scale bar = 0.5 mm. GUENSBURG AND SPRINKLE: EDRIOASTEROIDEA 37 contacting cover plates proximal ambulacrum V; ambulacral cover plates forming simple alternat- ing biseries, narrow zigzag perradial suture; cover plates thick, slab-like, with club-like external pro- jections, upper surfaces flattened, lateral abradial margins nearly vertical; single hood plate abradial to and articulating with adjacent cover plate, high- ly convex and medially constricted, apparently housing suspensory structures, gaps between hood plates at medial constrictions apparently com- municate with thecal interior; interambulacral ar- eas small, of 10-13 plate rows, interambulacral plates small, thin, imbricate, except for adoral- most plate, which is thick, with single central node; interambulacrals continue distally from ambula- cra in series of highly squamose plates and form short extensible thecal elongation zone; peripheral rim large, prominent in collapsed fossils, of five to six imbricate plate circlets, proximal circlet grading into distalmost interambulacrals. Occurrence— The four small specimens are at- tached to a small slab of intraformational con- glomerate that was apparently also a hardground. No other attached fossils are represented. The ed- rioasteroids were collected by Lehi Hintze and as- sociates along the Crystal Peak measured section (Hintze, 1973) approximately 1 1 m above the base of the Lehman Formation, Lower Whiterockian Stage (Llanvirnian), Lower Middle Ordovician. The collecting locality is in the SE NW, sec. 24, T23N, R16W, southwestern Ibex area in the southern Confusion Range, Millard Co., western Utah, USA. Specimens Studied— The holotype is usnm 172048, and the three associated paratypes are usnm 172049-172051. Etymology— Named for Crystal Peak, a prom- inent landmark just south of the collecting locality. Discussion— See Discussion under Genus Fan- ulodiscus. Acknowledgments We thank Anita Brosius, Cleveland, Ohio; Ron- ald Johns and Colin Sumrall, University of Texas, Austin; Fred Siewers, University of Illinois, Ur- bana; and Mike Slattery, University of Nevada, Las Vegas, for assistance in the field. Lehi Hintze, Brigham Young University, Provo, Utah, and Bruce Bell, Post Oak Oil Company, Oklahoma City, loaned specimens. Jennifer Logothetti, Northern Illinois University, Dekalb, drew and inked the figures. Eileen Dean, Rock Valley Col- lege, Rockford, Illinois, assisted in manuscript preparation. Raymond Ethington, University of Missouri, Columbia, identified conodonts for age determinations. Funding was provided by National Science Foundation grant BSR-8906568 and the Geology Foundation, University of Texas, Austin (J.S.), and by the Petroleum Research Fund of the American Chemical Society (grant of Mark Wilson, College of Wooster, Ohio) and the Graduate School, Southern Illinois University, Edwardsville (T.E.G.). 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Concerning the structure of the using parsimony. Version 3.0n. Computer program Agelacrinites and Streptaster, Edrioasteroidea of the distributed by Illinois Natural History Survey, Cham- Richmond and Maysville Divisions of the Ordovician. paign. Ohio Journal of Science, 19: 59-86. Whiteaves, J. F. 1 897. Description of a new genus and GUENSBURG AND SPRINKLE: EDRIOASTEROIDEA 41 Appendix Following is a compilation of edrioasteroid gen- era placed in our classification scheme, expanded and modified from Bell (1980). The agelacrinitids are easily the most diverse of edrioasteroid fam- ilies; several subfamilies are likely present, but these are not treated here, pending revision of the group. Limitations of time prevented a complete litera- ture search, and the list is not exhaustive. Class EDRIOASTEROIDEA Billings, 1858 Order CAMPTOSTROMATOIDA Durham, 1966 Family CAMPTOSTROMATIDAE Dur- ham, 1968 Camptostroma Ruedemann, 1933 Order STROMATOCYSTITIDA Bell, 1980 Family STROMATOCYSTITIDAE Bas- sler, 1935 Stromatocystites Pompeckj, 1896 Order and Family Uncertain Cambraster Cabibel, Termier, and Ter- mier, 1958 Walcottidiscus Bassler, 1935 Order ISOROPHIDA Bell, 1976 Family Uncertain Edriodiscus Smith, 1985 "Stromatocystites'''' walcotti Schuchert, 1919 Family AGELACRINITIDAE Chapman, 1860 Agelacrinites Vanuxem, 1842 Cooperidiscus Bassler, 1935 Curvitriordo Bell, 1976 Deltadiscus, n. gen. Dinocystis Bather, 1898 Discocystis Gregory, 1897 Hadrochthus Bell, 1976 Hemicystites Hall, 1 842 Hystrichopsydrax Guensburg, 1988 Isorophus Foerste, 1917 Isorophusella Bassler, 1935 Krama Bell, 1976 Lepidodiscus Meek and Worthen, 1 868 Lispidecodus Kesling, 1967 Neoisorophusella Kammer, Tissue and Wilson, 1987 Postibulla Bell, 1976 Rectitriordo Bell, 1976 Savagella Foerste, 1920 Spiraclavus Sumrall, 1992 Stalticodiscus Smith, 1983 Thresherodiscus Foerste, 1914 Timeischytes Ehlers and Kesling, 1958 Ulrichidiscus Bassler, 1935 Family LEBETODISCIDAE Bell, 1976 Subfamily LEBETODISCINAE Bell, 1 976 Argodiscus Prokop, 1965 Belochthos Bell, 1976 Chatsworthia Smith and Jell, 1990 Cystaster Hall, 1871 Euhydrodiskos Guensburg, 1988 Floridiscus Smith, 1980 Foerstediscus Bassler, 1935 Hadrodiscus Smith and Jell, 1990 Lebetodiscus Bather, 1908 Streptaster Hall, 1872 Subfamily CARNEYELLINAE Bell, 1976 Carneyella Foerste, 1917 Cryptogoleus Bell, 1976 Subfamily PYRGOCYSTINAE Kesling, 1967 Archaepyrgus, n. gen. Epipaston Holloway and Jell, 1983 Fanulodiscus, n. gen. Pyrgocystis Bather, 1915 Order EDRIOASTERIDA Bell, 1976 Suborder EDRIOASTERINA Bather, 1898 Family TOTIGLOBIDAE Bell and Sprin- kle, 1978 Totiglobus Bell and Sprinkle, 1978 "Totiglobus" lloydi Sprinkle, 1985 Family EDRIOASTERIDAE Bather, 1898 Edrioaster Billings, 1858 Edriophus Bell, 1976 Paredriophus, n. gen. Suborder EDRIOBLASTOIDINA Fay, 1962 Family ASTROCYSTITIDAE Bassler, 1935 Astrocystites Whiteaves, 1897 42 FIELDIANA: GEOLOGY Cambroblastus Smith and Jell, 1 990 Lampteroblastus, n. gen. Family CYATHOCYSTIDAE Bather, 1 899 Subfamily CYATHOCYSTINAE Bather, 1899 Cyathocystis Schmidt, 1879 Subfamily RHENOPYRGINAE Hollo- way and Jell, 1983 Rhenopyrgus Dehm, 1 96 1 GUENSBURG AND SPRINKLE: EDRIOASTEROIDEA 43 A Selected Listing of Other Fieldiana: Geology Titles Available A Preliminary Survey of Fossil Leaves and Well- Preserved Reproductive Structures from the Sentinel Butte Formation (Paleocene) near Almont, North Dakota. 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