Paleontological Contributions

THE UNIVERSITY OF KANSAS PALEONTOLOGICAL CONTRIBUTIONS July 14, 1988 Paper 120 HOMALOZOAN ECHINODERMS OF THE WHEELER FORMATION (MIDDLE CAMBRIAN) OF WESTERN UTAH' Georges Ubaghs and R. A. Robison Laboratoire de Paléontologie Animale, Université de Liége, B-4000, Liége, Belgium Department of Geology, The University of Kansas, Lawrence, Kansas 66045 Abstract. —Three new species, representing three of the four homalozoan classes, are described from the upper Wheeler Formation of middle Middle Cambrian age in west- central Utah. Ctenocystis colodon n. sp. is only the fifth species of Ctenocystoidea to be described. The new order Ctenocystida is defined. The solutan Castericystis? sprinklei n. sp. is the fifth species of Homoiostelea to be reported from Cambrian strata. The cornute Cothurnocystis? bifida n. sp. is the fifth species of Stylophora to be reported from Middle Cambrian strata worldwide and only the second from North America. This homalozoan fauna is among the most diverse known from any Cambrian formation. AMONG ECHINODERMS, homalozoans are un House Range, and the stylophoran Cothur- usual in their complete lack of radial symmetry. nocystis? bifida from the House Range. Representatives are relatively rare, especially in Each homalozoan species in the Wheeler Cambrian strata. Three new Cambrian spe- Formation is from a different locality. Such low cies, which represent three of the four homa- diversity is typical of most Cambrian echi- lozoan classes, are described here. All are noderm faunas, although locally each species from the upper Wheeler Formation of west- may be represented by numerous individuals. central Utah and include the ctenocystoid For several years, knowledge of the class Ctenocystis colodon from the Drum Mountains, Ctenocystoidea was limited to the single species the homoiostelean Castericystis? sprinklei from the Ctenocystis utahensis Robison and Sprinkle, 1969, which is locally abundant in the Spence Shale of Manuscript received 15 November 1987. northern Utah and southern Idaho. The 2 The University of Kansas Paleontological Contributions—Paper 120 Spence fauna is of early Middle Cambrian age. Jaekel, 1901, from the middle Middle Recently, the observed geographic distribution Cambrian of Czechoslovakia (Jaekel, 1901; of ctenocystoids was vastly broadened by the Bather, 1913; Ubaghs, 1967; Jefferies, 1969), description of the new species Etoctenocystis C. vizcainoi Ubaghs, 1987, from the upper bohemica Fatka and Kordule, 1985, from Czecho- Middle Cambrian of France, and Protocystites slovakia, Ctenocystis jagoi Jell, Burrett, and menevenis Hicks, 1872, from the middle Middle Banks, 1985, from Australia, and Ctenocystis Cambrian of Wales (Jefferies, Lewis, and Don- smithi Ubaghs, 1987, from France. Of these ovan, 1987). Additionally, Ceratocystis probably latter three species, C. smithi is the youngest, is represented in the lower Middle Cambrian of and it extends the observed stratigraphic range Sweden (Christina Franzén-Bengtson, cited by of the class to the upper Middle Cambrian. The Berg-Madsen, 1986:67), and dissociated plates description here of C. colodon n. sp. demon- of an unidentified cornute have been reported strates that ctenocystoids have a modest strat- from the Middle Cambrian of Bornholm, igraphic range and some diversity in the Denmark (Berg-Madsen, 1981:223; 1985:23; Middle Cambrian of western North America. 1986:73). Thus, the new cornute Cothurnocystis? Discovery of more representatives is to be bifida, described here, is a significant addition to expected. the meager record of Cambrian stylophorans. Cambrian representatives of the class Ho- Repository. —All homalozoan specimens de- moiostelea are known only from the United scribed in this paper are deposited with collec- States. Moreover, the only well-known species tions of the U.S. National Museum of Natural is the solutan Castericystis vali Ubaghs and History (USNM) in Washington, D.C. Illus- Robison, 1985, which is from the Marjum trated specimens have separate USNM num- Formation of late Middle Cambrian age and, bers (see figure captions). The remaining like most of the specimens described here, is ctenocystoids have been assigned USNM cata- from the House Range of Utah. Two fragmen- log number 432875a-j, the remaining homoio- tary specimens of an unnamed solutan have steleans are cataloged under USNM accession been described from the Weeks Formation of number 369516, and the remaining stylopho- latest Middle Cambrian age, also from the rans and associated fossils are cataloged under House Range (Ubaghs and Robison, 1985), USNM accession number 368342. and a single unnamed solutan stele has been Terminology. —Morphological terms used in described from the Whipple Cave Formation of this paper are defined in parts S (Ubaghs, 1968; late Late Cambrian age in Nevada (Ubaghs, Caster, 1968) and T (Sprinkle and Robison, 1963; Parsley and Caster, 1965). Additionally, 1978) of the Treatise on Invertebrate Paleontology. undescribed solutans have been reported from Acknowledgments. —This study would not the Lower Cambrian of Pennsylvania (Derstler, have been possible without the generous contri- 1975, 1981; Paul and Smith, 1984) and the butions and aid of others. We are especially lower Upper Cambrian of Alabama (Bell and indebted to Lloyd and Val Gunther, who dis- Sprinkle, 1980). Solutan specimens described covered all of the homalozoa-bearing beds on here from the Wheeler Formation add signifi- which the study is based and who made the cantly to this meager record of Cambrian ho- initial collections. Subsequently, Lloyd Gun- moiosteleans. ther, Metta Gunther, Frieda Gunther, Val Stylophora are equally rare in Cambrian Gunther, and Phillip Reese worked long and strata. In North America, an undescribed cor- hard to collect many more specimens. Funds to nute species has been reported from the Spence defray costs of collecting at the homoiostelean Shale of Utah (Robison and Sprinkle, 1969; and stylophoran localities were provided by the Sprinkle, 1976; Sprinkle and Robison, 1978) Smithsonian Institution through arrangements and two cornutes, Nevadaecystis americana made by I. G. Macintyre and F. J. Collier. Ubaghs, 1963, and Phyllocystis sp., have been Murielle Demaret-Fairon and Roger Fontaine described from the Whipple Cave Formation did most of the photography, and Marie Mas- (upper Upper Cambrian) of Nevada (Ubaghs, son aided in preparation of the line drawings. A 1963, 1968). In Europe, only three cornute preliminary draft of this paper was improved by species have been described: Ceratocystis perneri helpful suggestions from R. L. Kaesler and Ubaghs & Robison—Homalozoan Echinoderms of Utah 3 1 2 3 Fig. I. Ctenocyslis colodon n. sp. from upper Wheeler Formation, Drum Mountains.—/. Latex cast of superior surface, USNM 423872, X 12. 2. Inferior surface, USNM 423873, X 11.-3. Holotype, inferior surface, USNM 423874, X 10. James Sprinkle. Additional support was pro- upper Wheeler Formation. They are preserved vided by the National Science Foundation un- in a thin-bedded limestone and shale litho- der grant number EAR-8519324. facies, which has been interpreted to represent mostly pelagic settling of fine-grained sediment GEOLOGY AND PALEONTOLOGY in a deep-ramp environment (Rees, 1986:1060- 1061). Rare beds with common to abundant The Wheeler Formation in the House homalozoans suggest that these animals were Range and Drum Mountains of west-central gregarious and lived in small, discrete patches Utah is composed of an upward-shallowing on the seafloor. Little evidence of decay and sequence of marine shale and limestone. Thick- disarticulation prior to burial suggests that they ness of the formation ranges from as little as 128 were overwhelmed and buried alive, perhaps by m in the House Range to as much as 304 m in episodic storm deposits. the Drum Mountains. Rocks of the Wheeler Formation record the early infilling of the The Wheeler Formation contains a diverse House Range embayment, which was a broad biota. Trilobites are the most commonly pre- asymmetrical trough that deepened and wid- served fossils (Robison, 1964, 1971, 1984), but ened as it extended westward for some 400 km rare noncalcareous algae and soft-bodied ani- across the Middle Cambrian shelf of western mals (e.g., Conway Morris and Robison, in North America (Rees, 1986). Evidence that the press) indicate the original presence of a com- embayment was produced by a northeastward- munity much like that of the celebrated Burgess striking, high-angle fault has been presented by shale (Conway Morris, 1979, 1986; Whit- Rees (1986), who also described the lithofacies tington, 1985). Agnostoid trilobites of the up- of the embayment and interpreted their deposi- per Wheeler Formation are characteristic of the tional environments. upper Ptychagnostus atavus Interval-zone of mid- Homalozoans have been found only in the dle Middle Cambrian age (Robison, 1984). 4 The University of Kansas Paleontological Contributions—Paper 120 SYSTEMATIC DESCRIPTIONS Subphylum HOMALOZOA Whitehouse, 1941 Class CTENOCYSTOIDEA Robison and Sprinkle, 1969 Order CTENOCYSTIDA Ubaghs and Robison, new Description. —Characters of class (Sprinkle and Robison, 1978:T998-T1001). Discussion. —This taxon is established to complete the taxonomic hierarchy to which described ctenocystoid species are assigned. Family CTENOCYSTIDAE Sprinkle and Robison, 1978 Genus CTENOCYSTIS Robison and Sprinkle, 1969 1 2 CTENOCYSTIS COLODON new species Fig. 2. Shape of anterolateral inframarginal plates in two Figures 1, 2 species

Load more