Praepholidocidaris, a New Echinoid from the Pella Formation (Mississippian) of Iowa

Proceedings of the Iowa Academy of Science

Volume 84 Number Article 4

1977

T. J. Frest University of Iowa

H. L. Strimple University of Iowa

Let us know how access to this document benefits ouy

Recommended Citation Frest, T. J. and Strimple, H. L. (1977) "Praepholidocidaris, a New Echinoid from the Pella Formation (Mississippian) of Iowa," Proceedings of the Iowa Academy of Science, 84(3), 98-105. Available at: https://scholarworks.uni.edu/pias/vol84/iss3/4

This Research is brought to you for free and open access by the Iowa Academy of Science at UNI ScholarWorks. It has been accepted for inclusion in Proceedings of the Iowa Academy of Science by an authorized editor of UNI ScholarWorks. For more information, please contact [email protected]. Frest and Strimple: Praepholidocidaris, a New Echinoid from the Pella Formation (Miss 98

Praepholidocidaris, a New Echinoid from the Pella Formation (Mississippian) of Iowa

T. J. FREST and H. L. STRIMPLE 1

FREST, T. J. and H. L. STRIMPLE (Department of Geology , The University adradial plate columns. Age relati onships of the Pell a Formation and the of Iow a, Iowa City, Iowa 52242). Praepholidocidaris, a new Echinoid from the paleoecology of it s echinoderm fa una are reviewed . It is concluded that the Pella Formation (Mi ssissippian) of Iowa . echinoderms represent an opportunistic assemblage and the bulk of the Praepholidocidaris pellaensis, n. gen., n. sp., is described from basal Chester echinoderm fa una support s assignment of unit C of the fo rmation to the Talaro ian rocks in the vicinity of Oskaloosa and Gi vin , Mahaska County, Iowa. The crinus Zone (of Horowitz and Strimple, 1974 ), basal Chesteri an. new genus is characteri zed by its small number of ambulacral and interambulac INDEX D ESCRIPTORS: Late Mi ssissippian; Chesterian; Ta larocrinus Zone; ral plate columns, adorall y expanded ambulacra, unequal ambulacrals with Pell a Formati on; Mahaska Count y, Iowa; Echinodermata; Echinoidea; perforate primary spines, and interambulacrals with primary spines only on Echinocystitidae; Praepholidocidaris pellaensis; Pholidocidaris ; paleoecol ogy.

The prolificall y foss ili fe rous Mississ ippian Pella Formati on has been substrates for those species which were sessile. There is little deviation a subject of paleontological investigations for more than a century from typical abundance of these groups in the echinoderm layer (in fact (Hall , 1858). However relatively little modem work has been done on some are commoner th an at other levels); however hold fas ts and the the invertebrates, and some groups have been almost totally neglected. certainly sessile edrioasteroids are more than usuall y common, but are This is particularly true of the Ec hinodermata: though long known as a still rather rare as compared to the number of crown s recovered. The so urce of exceptionally preserved bl astoids other echinoderm classes lithology of the echinoderm zone, rarity of many- pl ated camerates(e.g. wi th the exception of the Edrioasteroidea (Strimple, 1968; Bell , 1976) Batocrinus), abundance of flexibles, and presence of free-li ving genera and two crinoids (Strimple, 1974) have not been previously re ported. such as Camptocrinus indicate that the echinoderm s were either Collecting in recent years has yielded a variety of crinoids, edri oas broadl y tolerant species or were adapted to soft bottoms. The latter teroids, and starfish as well as the echinoid described below: these will alternati ve is most probable: the commonest edri oasteroid (Lepidodis be the subject of future report s. Unlike the rather ubiquitous bl astoids cus laudoni; see Bell , 1976 , pp. 557-567) has a claveate theca with the (Pentremites conoideus, Diploblastus glaber ) nearl y all of the other oral face in the adult elevated considerably above the original point of echinoderm s have been fo und onl y at a single locality, the abandoned attachment of the theca. It seems likely that the majority of the Pell a county quarry , north of Oskaloosa, Iowa, although a single echinoid crinoids, as we ll as the echinoid and starfis h, were effectively was collected at the Banzee quarry, near Givin , Iowa (detailed eleutherozoic ( sensu Kirk , 19 11 ) due to the nature of the substrate and localities cited below). Most of the echinoderms are restricted to a probable comparatively high rate of sediment acc umulation. si ngle thin layer in the upper third of the formati on. None of the Precise age relati onships of the Pell a are uncertain. The hi story of the echinoids were fo und in pl ace though crinoids and blastoids have been fo rmation has been reviewed by Rexroad and Furni sh ( 1964 ), who also recovered in situ . The majority of specimens are loose on dump piles provide a secti on of the Oskaloosa exposure (their text-figure I). On the where shale discarded from the echinoderm-bearing layer happened to basis of the conodont fa una these authors place the fo rm ation within the have been the last materi al discarded: hence the distribution of the Gnathodus bilineatus - Cavusgnathus characta Assemblage Zone and echinoderm s as coll ected is extremely spotty. correlate it with the Ste. Genevieve (Rexroad and Furnish, p. 669). Most of the crinoids occur as crown s, often retaining part of the Series assignment of the Ste . Genevieve has been either to the Merame column , despite the poorly indurated nature of the enclosing rock, can , the Yalmeyeran, a separate series between the Yalmeyeran and which in pl aces approaches a mudstone. Many bl astoids retain the Chesterian (e.g . Swann , 1963), or the Chesterian. On thi s po in t Rex brachi oles and covering pl ates, and several of the echinoid s and starfish road and Fumish(op. cit.) comment that ' 'the Ste . Genevieve conodont have spines still articul ated , probably indicating an autochthonous fa una is sharply different from the conodonts of the underl ying fo rma assemblage. In most echinoids the interambulacral plates have shifted tions of the Valmeyer series but is closely simil ar to, if not ident ical and become telescoped or are otherwise disrupted; this is likely due to with, the conodont s of the overl ying Chester series" (p . 669). Wi th sediment compacti on aro und origin all y intact specimens. The crinoid regard to the Pell a echinoderm zone (included in unit C of Rexroad and fa una is peculi ar in th at it is dominated in terms of abundance by the Furnish, op. cit .) we prefer the Chesteri an assignment fo r the forma flexible Taxocrinus shumardianus whereas the majority of species are tion. Talarocrin us, a common constituent of Chesteri an fa un as, is in adunate s. The camerates are mostl y simple types (Dichocrinus, present in the Pell a while Platycrinites appears to be unrepresented Camptocrinus, Talarocrinus). For many crinoid species fe w adult or even by stems. ve ry yo ung indi viduals are encountered, and most (e xcluding the fl exi Other echinoderm s present in the Pell a (i.e. Taxocrinus shumar bles) have not been recovered even as isolated plates outside of the dianus, Diploblastus glaber) could support ei ther a Late Meramecan or echinoderm zone though Praepholidocidaris, blastoids, edrioas Early Chesteri an age fo r the top of the fo rmati on. On the whole the teroids, and stems do occur at other levels in the Pella. The fauna seems preponderance of species indicates the likelihood of Early Chesteri an to represent an opportunisti c assemblage that was able to populate a age (Talarocrinus Zone as defin ed by Horowitz and Strimple, op. cit ., small area of the Pella-age sea bottom for an extremely short period of pp. 207 , 213) for unit C of the Pella. time, perhaps during an interval of slightly decreased sedimentation , but was abruptly wiped out by an influx of mud. Sedimentation rate was PALEOECOLOG Y most likely the determinant factor in establishing fauna) composition and in the eventual terminati on of the assemblage since other inverte Praepholidocidaris (new genus) was an integral member of the Pella brates, especiall y brachiopods and corals, could have provided hard echinoderm fauna. Despite the generally fragil e nature of echinoid tests it is represented by over thirty specimens. The occurrence is unusual in !Geology Department , The University of Iowa, Iowa City, Iowa, 52242. that the echinoids were not fo und in a· ' nest' ' but are scattered sparsely

Published by UNI ScholarWorks, 1977 1 Proceedings of the Iowa Academy of Science, Vol. 84 [1977], No. 3, Art. 4 A NEW ECHINOID FROM IOWA 99

throughout the echinoderm-bearing layer. Other echinoids are virtually this paper relate to these three species collectively. absent: a few plates and spines of an archaeocidarid were the only other The finding of a genus which when dissociated would yield plates echinoid remains encountered despite intensive search. The seeming and spines virtually indistinguishable from those of Pholidocidaris paucity of echinoid species supports the inference of an opportunistic suggests that the acription of such material to a definite genus, as was assemblage. Praepholidocidaris seems to have been more tolerant of commonly done in the past, is unjustified unless a very large number of silty conditions than many of the Pella species: isolated plates and isolated parts, allowing a virtual reconstruction in full, is available. spines have been observed at other levels in the Pella and as mentioned This point has been made previously by Kier ( 1958, p. 11) in connec above it is one of the few species to be found outside of the Oskaloosa tion with the Archaeocidaridae. Erection by Kier (op . cit.) of the locality. Probably this greater ecological tolerance is related more to the Mississippian genus Polytaxicidaris, which differs from Ar echinoid's feeding habits than its motility. The echinoid's feeding chaeocidaris almost solely in the number of ambulacral columns, has system, unlike that of crinoids, is not prone to fouling by fine sediment made it untenable to refer isolated archaeocidarid interambulacrals to particles. Like many Paleozoic echinoids the rather short and acicular Archaeocidaris; the majority of nominal species are based only on such spines of Praepholidocidaris may have functioned more as protection material. According to Kier ( 1965 , p. 456) only 8 of the 42 " species" than as a means of locomotion. Durham (in Durham et al., 1966) has of Archaeocidaris are recognizable on these grounds. Subsequent de interpreted the living position of similarly shaped (depressed, with flat scription by Kier of another Polytaxicidaris (Kier, op. cit.) strengthens oral surface) lepidocentrids to be with the oral surface submerged in the the argument, and an undescribed Pennsylvanian echinoid in the Uni substrate and only the apical surface projecting above the sea floor. The versity of Iowa collections that is apparently also referable to suggestion is plausible although it is also likely that echinoids living on Polytaxicidaris greatly increases the range overlap of the two genera. a fine mud bottom would need to retain some ability to adjust their The widespread geographic distribution of Pholidocidaris (sensu lato) position unless the sedimentation rate were extremely low. The closely makes it probable that the same situation could recur unless echinoid related genus Pholidocidaris has primary spines on all the interam taxonomists exercise more parsimony. Paleozoic echinoids are rare bulacral plates of the oral surface: Praepholidocidaris interambulacrals fossils, and evolutionary trends within the Paleozoic are still poorly bear primary spines only on those plate columns bordering the am understood (Kier, op cit., p. 437): consequently even fragmentary bulacra. These spines in Echinocystitoida typically are the longest and material may be of interest. The fact that significant contributions to our most sturdy set and have the best developed articulation; hence the knowledge of Paleozoic echinoids can be made while following Kier's primaries are most likely to have served a locomotory function in suggestion in regard to taxonomy has been demonstrated by Hoare and addition to being protective. The small number of oral face interam Sturgeon (1976) . bulacrals with primaries in Praepholidocidaris may indicate that the Among the evolutionary trends within the Echinocystitoida de genus was less active than Pholidocidaris. lineated by Kier (op . cit.) may be noted the following: I . Adoral expansion of ambulacra. PHYLOGENETIC RELATIONS 2. Increase in number of ambulacral columns in some families (including the Echinocystitidae). Praepholidocidaris is morphologically similar to Pholidocidaris in 3. Development of regularity in shape of interambulacral several respects. The test shape of Praepholidocidaris pellaensis (new plates. genus) appears to be identical to that of Pholidocidaris irregularis, the 4. Flattening of the test. type species of Pholidocidaris. Like the latter Praepholidocidaris has 5. Increase in the number of plates. ambulacra that are adorally much wider and are composed of larger 6. Increase in the size of the test. plates. In both genera the adapical adradial interambulacrals are larger 7. Differentiation of spines and development of tubercles. than the other interambulacrals while all adoral interambulacrals are of In all of these respects Pholidocidaris is a relatively advanced genus, similar size. Overall the spines and plates of both genera strongly which is not altogether surprising in view of its stratigraphic occurrence resemble each other. Differences in numbers of ambulacral and in (Mississippian). The monotypic Praepholidocidaris, though younger terambulacral plate columns, the presence of primary spines on at least than most Pholidocidaris species, is oddly primitive. Its shape and some ambulacrals of Praepholidocidaris, and the lack of primary ambulacral development are close to those of Pholidocidaris but the spines on the median interambulacral plate columns on both test number of plate columns, both ambulacral and interambulacral, is less, surfaces in Praepholidocidaris readily distinguish the two. These dif and the primary tubercles, while evolutionarily advanced in structure, ferences are detailed below, and only a few points concerning are fewer in number on the interambulacrals. Since little evidence taxonomic and phylogenetic implications of the genus need to be contradicts Kier's evolutionary scheme it is likely that much older discussed here. species of Praepholidocidaris remain to be discovered. The close relationship between Praepholidocidaris and Pholidocidaris necessitates discussion of the latter at some length in the SYSTEMATIC DESCRIPTION systematic description . Our concept of Pholidocidaris is derived Class ECHINOIDEA Leske, 1778 largely from the work of R. T. Jackson, who in two papers (Jackson, Subclass PERISCHOECHINOIDEA M'Coy, 1849 1912, 1929) described or reviewed essentially all the known material of Order ECHINOCYSTITOIDA Jackson, 1912 the genus. The more recent treatment of the genus in the echinoid section of the Treatise on Invertebrate Paleontology by Kier ( 1966) is Diagnosis. - Perischoechinoidea with strongly imbricate plates; am largely derivative but Kier's format for generic descriptions, and the bulacral plates beveling under interambulacra, imbricating adorally; phylogenetic assumptions on which it is based, are accepted and fol interambulacral plates reaching peristome, imbricating adapically; gen lowed herein. In an earlier paper Kier (1965) ascribed five species to ital plates present, perignathic girdle absent (after Kier, in Durham et Pholidocidaris, although other fragmentary material consisting only of al., 1966, p. U301). isolated elements, not described to the specific level, has also been placed in the genus by other authors. Abandonment of this practice is Family ECHINOCYSTITIDAE Gregory, 1897 advocated herein (next paragraph). Of the nominate species only three Diagnosis. - Echinocystitoida with ambulacra enlarged adorally in (P. irregularis, P. tenuis, and P. tournacensis) are represented by Mississippian and younger genera; more than two columns in each good material: otherwise unspecified references to Pholidocidaris in ambulacrum (after Kier in Durham et al., 1966, p. 301). https://scholarworks.uni.edu/pias/vol84/iss3/4 2 Frest and Strimple: Praepholidocidaris, a New Echinoid from the Pella Formation (Miss

100 PROC. IOWA ACAD. SCI. 84 (1977)

'f"f'Xt -Fig11ff I . Came ra lu c ida sketc hes of plates of Praepholidociduris spines, and brace. Sec also Pl ate 2 . fi gure 7. c. lntcrambulacrum /!f'liu1'11.1i s. n .g .. n. , p. Black areas indicate matrix or places where showing plate a rrangement . Adoral portion at hottom . SUI 39482 : for plate arrange ment cannot he deciphe red . comparison with Pl ate I . fi g ure 3 & 4. d . Apical surface of small e ntire a. Adoral , urface of holoty pe (SUI 3949 1) sho w in g inte rambulacral paraty pe (SU I 39485 ). showi ng ambulacral plate arrangeme nt and plate, and tuberc le,. Compare w ith Plate 2 . fi g ure 6 . b. Adapical s pines; compare w ith Plate 2 . fi g ure 4 . , urface of holotype . Note gcnitab . inte ramhulacral plates, secondary

l< l'lllllrks . - In th e Treati ,e (Kier, in Durham l'l lll . , 1966, p . U308) chodromus) do displ ay a similar trend to adoral e nlargeme nt of the Ph11/id11cidaris i, included in the Lepidocentridac, a famil y c harac ambulacra. However the much g reater arnhulacral expansion adorally terized hy invariable possession of only two columns of plates pe r in such M issi ssippia n cch i nocys t it id s as Prot 1' rocid11ris and amhulacrum (op . cit ., p . U304) . This is probably an oversig ht because Pholidocidaris is distinctive. Enlargeme nt of a111hulacra obviously is th e amhulacra of Plwlidocidaris arc well known and the genus has been rendered more easily possihlc in cchinoids which possess a large a,sociatcd with th e othe r genera of th e Echinocystitidae since at least number of plate columns in each a!llhulacrurn . Both Pl111/id1wid11ris th e time of Jac bon ( 19 12). Ki er ( 1965, tex t-figure 9 and in passing) and Praeph11/id11cid11ris arc accepted as !lle rnhc rs of thc 1:chinocystiti earlie r accepted the echinocystitid as,ignment of the genus . The Mi s dac in the prcsc nt papcr. In order to facilitat e di ,c uss io n , i.,., ippian rn emhe r, of hoth famili..:, can have similar test sha pes and of Pra 1' ph11/id11 cid11ris ( new ge nus) a ge ne ri c d escription o f co!llparahlc di,trihution of primary , pine tuhercul es (e .g. Perisch11d Ph11/id11cidaris follows. The ho lot ype of the type ., pCL· ies of th e genus rn11111 s). and two M i.,., i.,.,ippian lcpidoccntrids (Hv a11,,chi11us a nd Pnis- (P . irreg 11/11ris) is illu,trated o n Plate I . fi gures I & 2.

Published by UNI ScholarWorks, 1977 3 Proceedings of the Iowa Academy of Science, Vol. 84 [1977], No. 3, Art. 4 A NEW ECHINOID FROM low A IOI

Text-Figure 2. Camera lucid a sketches of Praepholidocidaris pellaen pores, and ambulacral plate tubercles, X 3. c. Two large primary spines sis, n. gen., n. sp. Black areas represent matrix or are indecipherable. showin g straight and curved shafts, X 7.5. d . Cluster of secondary a. Paratype SUI 39490 showing apical system, X 5. b. Adora) surface spines from holotype (SUI 3949 1) illustrating morphology. X 20. of SUI 39502 showing large adoral ambulacrals, peripodia and peri-

Genus PHOLIDOCIDARIS Meek & Worthen, 1869 plates much larger than other interambulacrals; adorall y all interam Type Species. - Pholidocidaris irregularis (Meek & Worthen) . bulacral plates of same size; single large perforate primary tubercle on Diagnosis. - Ambulacra adorally much more developed than abor adapical and all adoral interambulacral plates; secondary tubercles, ally; five or more commonly , six or more columns of plates per probably imperforate, on other plates: basal terrace and scrobicul e ambulacrum, imbricating adorally; adoral ambulacral plates larger than present but scrobicular ring and parapet lacking around primary tuber adapical, with distinct peripodia on adoral plates onl y; ambulacrals cles with scrobicular circle and low boss but no scrobi cule or basal wi th secondary tubercles only: interambulacrals imbricating adapi terrace . Primary spines stout , straight , enlarged at base, longitudinally call y, six or more columns per interambulacrum; adapically adradial striated, terete. https://scholarworks.uni.edu/pias/vol84/iss3/4 4 Frest and Strimple: Praepholidocidaris, a New Echinoid from the Pella Formation (Miss

102 PROC. IOWA ACAD. SCI. 84 (1977)

Remarks. - The above generic diagnosis is taken largely from Ki er specimens (e.g. SUI 39485; text fi gure Id, Plate 2, fi gures 4 & 5). Test (op . cit ., p. U308), supplemented in some detail s from the more much wider than hi gh, discoid al, with fl at oral surface and gently extended diagnosis and descriptions in Jackson ( 19 12, pp. 433-442; rounded ap ical surface; profil e probably similar to those of 1929, pp. 64-67). As defined above the genus includes the fo ll owing Pholidocidaris and Perischodromus (Ki er, 1965, text-fi gure 5), out species: P . irregularis (Meek & Worthen), P . tenuis Tornquist, P . lined as viewed from above rounded. tournacensis Jackson; all are from the Mississippian (Lower Car Size: small , widest measured interambulacrum width 12.7 mm at boni ferous) of England, Ireland, Germany, Belgium , and the United ambitus, largest ambulacrum measured 5 .0 mm at ambitus; estimated States. The fo ll owing species are very imperfectl y kn own , could be diameter or largest specimen 30 mm. Isolated adapical face interam long to Praepholidocidaris, Pholidocidaris, or other genera, and bulacrals indicate a maximum diameter of abo ut 50 mm. should probabl y not be retained in a definite genus: P . acuaria (Whid Apical system: some genitals preserved in holotype (SUI 39491; borne) [onl y Devonian species], P . anceps (Austin) [see Mortensen Text-figure I b, Plate 2 , fi gure 7); a more complete example is illus ( 1935), pp. 74-75], P . gaudryi Julian ,? . sp. Jackson ( 19 12, p. 440), P . trated as Text-figure 2a (SUI 39490). Genitals large: one pl ate (pre sp. Jackson ( 1929, p. 67), P. sp. Schmidt (1930, p. 72) . sumably including madreporite) larger than others, with six large pores Genus PRAEPHOLIDOCIDARIS, new genus which tend to be occluded by secondary cal cite, no madreporite pores obvious; remaining genitals with abo ut 60% of area of largest, three to Type species. - Praepholidocidaris pellaensis, new species. fo ur large pores on each arranged in an arc with apex directed adapi Diagnosis. - Ambulacra adorally much more developed than abor cally. All genitals with numerous secondary spine tubercles, large all y; typicall y fo ur columns of plates per ambulacrum, imbricating pores tending to be disposed in crescent on adapi cal half of plate. Some adorally; adoral ambulacral plates much larger than adapical , with small plates with secondary spine tubercles near center of Text-fi gure peripodia only on adoral ambulacrals; all ambulacrals with both perfo 2a are though to be oculars; they are non-porous and approximately one rate primary and occasional imperforate secondary tubercles; four third the size of the genitals. Ocul ars and genitals thick, outer surface columns of plates in each interambulacrum; interambulacrals imbricat broadly convex . ing adapicall y; adradial plate columns on both surfaces of test slightly lnterambulacra: fo ur columns of thick plates in each area, imbricat larger than plates of median columns, with sin gle perforate primary ing adapicall y (Pl ate 2, fi gure 4 ; Text-fi gure Id), laterally from center tubercles developed as in Pholidocidaris; all interambulacrals with to adradials . Plate shape and origin of columns as indicated in Text nonperforate secondary tubercles much like those of Pholidocidaris. fi gure I c, a nearly complete interambulacrum lacking only the most Primary spines include both straight and proximall y curved types, adapical plate (see also Plate I , fi gures 3 & 4). Interambulacrals of otherwise similar to those of P . irregularis. adapical surface forming an almost equi alteral tri angle, rapidly reach Horizon. - Pell a Formati on, basal Chesteri an (Mississippian), Iowa. in g full complement of columns; adoral interambulacrals fo rming elon D ifferences bet ween and R emarks . - Praepholidocidaris gate triangle with concave lateral edges, fo urth column appearing Pholidocidaris have been outlined above and require little additional immediately before ambitus. Adradial interambulacrals onl y with pri comment. Since the former genus is at present monotypic assessments mary tubercles, all interambulacrals with numerous secondaries. A of the relationships between the two necessarily have limited value. scrobicular ring of tubercles is most noticeable in young individuals The generi c characters as a whole indicate that Praepholidocidaris is (Plate I , fig ures 3, 9; Plate 2, fi gures I , 5) but less distinct on largest archaic in some respects as compared to other Mississippian echinoids, specimens (Plate 2, fi gures 6, 7). Adradial pl ates only sli ghtly larger particularly Pholidocidaris, despite its apparent Chesterian age. The than more central ones, at most I 'h times length of central interam pattern of spination of the interambulacrals is strikingly reminiscent of bulacrals. lnterambulacrals of both faces abo ut equal in area, moder th e lepidocentrid Perischodromus (see Jackson , 1912, p. 401) and is ately imbricate, mostly hexagonal in shape, but adradials with adam most closely paralleled among the Echinocystitidae in Proterocidaris. bulacral sutures scalloped , extending partly over fi rst ambulacral col The presence of peripodia and primary spines on the ambulacrals are umns. Tubercle morphology as in generi c description. probably advanced characters; but the restricti on of primaries to onl y the adradial interambulacrals is decidedly primitive. Several of the more unusual aspects of the genus' morphology that run counter to the Plate I . Echinoids from Iowa and Illinois. I . Adora! surface of general trends of evoluti on within the Echinocystitoida are noteworthy holotype of Pholidocidaris irregularis (Meek & Worthen) , Field in that they are paralleled most closely amo ng contemporary Museum UC 10522, Hamilton or Nauvoo, Illinois, X 1.5. Note large Echinoidea by the cidaroids. Among these may be mentioned the small ambulacral plates with peripodia, small interambulacrals each bearing number of ambulacral and interambulacral columns and the extremely a primary spine tubercle . 2. Adapical surface of Pholidocidaris ir depressed test shape. As compared to Pholidocidaris the interambulac regularis (Meek & Worthen), holotype , showing small ambulacrals ral plates are more nearl y equal in area in all columns and the amount of near center of fi gure and large scal e-like interambulacrals; onl y en imbrication (as j udged from the proportion of plate area without larged ad radial plates with primary tubercles. 3. Adora! portion of two secondary tuberc les) is reduced . It is thus possible that ambulacra and interambulacrum of Praepholidocidaris pellaensis, n. Praepholidocidaris represents a specialized offshoot from the gen., n. sp., sho wing large hexagonal ambulacrals, ambulacral spines, Echinocystitoida that is evolutionaril y convergent in some ways with and interambulacral pl ate arrangement. Paratype SUI 39489, X 5.5. 4 . the earl y Cidaroidea rather than a persistent member of the ancestral Adapical surface of same specimen as 3 to show interambulacral pl ate stock which gave ri se to Pholidocidaris, but present evidence is hardly arrangement and secondary spines; note size of pl ates, tubercle mor conclusive. phology, and weak scrobicular ring of secondaries on thi s and preceed PRAEPHOLIDOCIDARIS PELLAENSIS , new species ing figure .· X 5 .2 5 . Side view of lantern showing outer surfaces of Plate I , fi gures 3-9; Pl ate 2; Text-figures I & 2 demipyramids. SUI 39484 , X 5.6. 6 & 7. Ad api cal and adoral si des Diagnosis. - Same as that of genus. respectively of Praepholidocidaris pellaensis, SUI 39487, showing size and shape of ambulacrals, relative widths and shape of ambula Material. - About thirty specimens, mostly fragmented flattened tests crum on each side . X 6 . 7 . 8 & 9. Adapical and adoral views of another with pl ates di sarranged , preserved in a soft shaley matrix. paratype (SUI 39488). This specimen shows good secondary spines on Description . - Shape: although all specimens are probably somewhat adapical face and primary ambulacral spines in place, scrobicul ar ring flattened, the ori ginal shape can be inferred from relatively complete on interambulacral primary tubercles of adoral face . X 4 . 7.

Published by UNI ScholarWorks, 1977 5 Proceedings of the Iowa Academy of Science, Vol. 84 [1977], No. 3, Art. 4 A NEW ECHINOID FROM lowA 103

https://scholarworks.uni.edu/pias/vol84/iss3/4 6 Frest and Strimple: Praepholidocidaris, a New Echinoid from the Pella Formation (Miss 104 PROC. IOWA ACAD. SCI. 84 (1977)

, , .._ , . ,,.. 1··

Plate 2. Praepholidocidaris pellaensis, n. gen., n. sp. I. Adapical viewed from above. Large genital plate (possibl y madreporite) at rop of surface of moderate-sized whole specimen, showing edges of disrupted fi gure. X 5.5.4. Adapi cal face of a small whole specimen illustrating interambulacral pl ates. SUI 39483, X 5.3. 2. View of adoral surface of imbrication of ambulacral and interambulacral pl ate columns, plate same specimen. Note ~grooved l ooth , ambulacral peripodia, and pri tubercles, and primary spines in pl ace on both pl ate types. Peristome mary spines. X 5.3. 3. Fragment of large speci men showing lantern as obscured by spines. X 4.3. 5. Oral face of same specimen as (4)above

Published by UNI ScholarWorks, 1977 7 Proceedings of the Iowa Academy of Science, Vol. 84 [1977], No. 3, Art. 4 A N EW ECHINOID FROM IOWA 105

Ambulacra: four columns of une4ual plates in each ray on both faces. Pholidocidaris. lik e many oth er echinoid s. acq uires it s distinctive ambul acra much wider on aboral race. petaloid in shape wi th maximum characteri sti cs at an earl y stage of growth . Many of the differences width reached at a point less th an half radi al distance to ambitus (Plate between the two genera have been noted previously, but a few supple I. fig ure 7); ambul ac ra of adapical face narrow. gradually in creasin g in mental compari sons can be appended. Adradial int erambulacrals in width approachin g am bitus but less than half greatest adoral width at Ph olidocidaris are two to three times th e length of the median column ambitus. Adora! ambulacrum of one specimen (Tex t-fi gure 2b) may plates, and the interambulacrals of the adapical face are distinctl y large have fi ve co lu mns. Most ambulacrals regularl y hexagonal in shape in size. The genitals of Pholidocidaris have six to ten ge nital pores and (Plate I. fig ures 3. 9) but some adapical plates diamond-shaped (Plate are proportionately small er than those of Praepholidocidaris. Addi 2. fi gure 4). Adora! ambulacrals large r in average size than adapical ti ona ll y, th e poorl y known oc ul ars of Pholidocidaris may be perforate (compare Plate I. fi gures 6 & 7. 8 & 9); adoral plates also with (J ac kson, 19 12, p. 435). pore-pairs su rrounded by dee p peripodia (text-figure 2b; Pl ate 2. fi gure 5) and bearin g both primary and secondary spines. Adapical plates with ACKNOWLEDGEMENTS primary spi nes and probably second ari es al so; peripodia not developed. Ambulac ral s beveling orall y. latera ll y beveling under interambulacra . Besides th ose specim ens coll ected by th e authors several individuals th ick. Colu mns adjace nt to interambu lacra laterall y elongate and large r generously contributed materi al to this paper. Chri stina Strimple do on both faces. Pore pairs eccentric. not oblique. situated closer to side nated nearl y half of the avai lable specim ens; oth er important speci mens or plate facin g nearest intcrambul ac rum . Ambulacrals near peri stome were coll ected by Douglas and Cheryl DeRosear and W. M. Furnish . and adjace nt to apical system rapidl y dec reasin g in size; origin s of Mr. & Mrs. A. Banzee, of Pell a, Iowa graciously all owed th e senior columns not seen but all four arc present very close to test apices. author access to their propert y. We also thank Dr. M. H. itecki and Peri stome: not we ll preserved on available material , likely very Ms . Katherine Kreuger, Fi eld Museum , fo r the loan of th e holotype of small ; int erambulacra not reaching pcristome. Pholidocidaris irregularis. R. G. Baker and T. W. Broadhead (U ni ve r Spines: primaries of two types, straight and curved (Text-figure 2c; sity of Iowa) revi ewed and improved this final draft. Plate 2, fi gures 4 & 6); longitudinall y fin ely striate, 40-50 striations on largest spines. Primari es wi th swoll en bases: we ll -developed mill ed rin g and coll ar, knurl ed annulus; shaft tapering, rather stout; cross sect ion ro und ; longest int crambulacral primary observed (in complete) LITERATURE CITED 11 .5 111111 long. Am bul acral primari es small er (Plate 2, fi gures 2, 4, 6) onl y strai ght type observed, oth erwise similar to interambul acral BELL. B. M. 1976 . A stud y of orth Ame ri ca n Edrioasteroidea . N . Y. Stare Museum and Sci. Ser .. primaries; longest observed spi ne (complete) 8.0 111111 long. Secon Mem. 21. 447 p. . 64 pis. daries very small , stout tapering abruptly, bases swoll en, shaft or DURHAM. J. WYATT. 1966. Eco logy and Paleoecology. in Durh am. J. Wyatt . et al .. Ec hinoid s. Trea ti se on In vertebrate Paleontology. Part U. namented by a few longitudinal stri ae (Test-figure 2d; Plate I, fi gure 4; Ech inoderm ata 3 ( I): U257-U265. Pl ate 2, fi gure 7). Ambulacral secondaries sli ghtl y small er, more terete HALL. J. 1858. Geology of Iowa . v. I. pt. 2. Paleo nt ology. pp. 473-724. 29 (Plate I, fi gure 9), otherwise lik e th eir interambulacral counterparts. pi s. Lantern: in completely known . represented by demipyramids (Plate HOAR E. R. D .. & M. T. STU RG EON. 1976. Ec hinoid remains from the I, figure 5; Pl ate 2, fi gure 3), a single brace on the hol otype (Plate 2, Penn sy lva ni an Vanport Limestone (A ll egheny Gro up) . Jo11r . Paleo1110/ogr fi gure 7), and a tooth (Pl ate 2, fi gure 2). Lantern small, similar to that of 50: 13-24 . 2 pis. Pholidocidaris in morphology, with wide-angled demipyramids each HOROWITZ. A. S .. & H. L. STRIMPL E. 1974. Chesterian Ec hinoderm with deep foram en magnum; teeth wide, grooved on outer surface. Zonal ion in Eastern United States. Seve nth Intern ati onal Congress on Car Types. - All type specim ens in the Repos itory of th e Geology bonifero us Strati gra ph y and Geology. 3: 207 -219 . JACKSON. R. T .. 1912 . Ph yloge ny of the Ec hini. with a re vision of Pal eozo ic Department, The Uni versit y of Iowa. Holotype SUI 39491 ; figured spec ies. Boston Soc. Nat. Hist .. Memoirs. 7. 490 pp .. 76 pis. paratypcs SU I 39483-39490, 39501 -39502; unfigured paratypes SUI _ _ . 1929. Palaeozo ic Echini of Belgiu m. Must' <' Rora/ Hisr. Nat. 39483. 39492-39500. Beli:iq11 e. Memoirs. 38. 96 pp .. IO pis . Horizon and locali1ies. - Pella Formation. Mi ssissippian (basal KI ER. P. S. 1958. New American Paleozo ic echinoids . S111i1hso11 il/11 Misc. Chesterian), abandoned county 4uarry N. of Oskaloosa, near center of Coll .. 135 (9): 1-2 6. 8 pis. N. line of section 30, T. 76 N .. R. 15 W .. Oskaloosa 7 1/2' quadrangle; _ ___ . 1965. Evol uti onary !rends in Paleozo ic ec hinoid s. Jo11 r. Pl/leon inactivc 4uarry NEofGivin , SW '.4 NW 1/i sec. 12, T. 74 N. , R. 16 W. , wlogy. 39 (3): 436-465 . pis. 55-60 . Eddyvill e 71/i' quadrangle, Mahaska County , Iowa. __ . 1966. Noncidaro id Paleozo ic ec hinoids. i11 Durham. J. Wyatt. er Remarks. - The close simil arities between Praepholidocidaris and al .. Echi noid s. Trea ti se on In ve rtebrate Paleontology. pt. U. Ec hinodermata 3 ( I): U298-U3 12. Pholidocidaris. plu s the small test size, ori gin all y led us to believe that KIRK . E. 1911 . The Structure and Relati ons hips of ce rt ain Eleutherozo ic the Pell a specim ens might be immature Pholidocidaris; however, Pelmatozoa. U.S. National Museum. Proc .. 4 1: 1-13 7. pis. 1- 11 . com pari sons with th e two j uve nil es of the type species of MORTENSEN . Th . 1935. A Mon og raph of the Ec hinoid ea . 11 . Bo Pholidocidaris described by Jackson ( 191 2. pp. 436-437), both within thri oc idaroida. Melonech inoid a. Lepidoce ntroida . and Stirodonl a. 647 pp .. th e size range of Praepholidocidaris. revealed numerous differences. 89 pis. REX ROA D. C. B.. and W. M. FU RNISH . 1964 . Conodonts from the Pella Formati on (Mi ss iss ippi an). So uth-ce nt ra l Iowa. Jo11r . Pl//c,,m10/ogr. 38 (4): 667-675. pl. 111 . showin g large ambulacrals with pore pairs surrounded by raised SCHMIDT. W. E. 1930. Die Echinoderm en das deulschen Untcrkarbon s. Preuss. Geo/. La11dem11sta/1 . Jahrh .. 92 pp .. 3 pis. pcripodia. Plates somewhat jumbled. X 4.3. 6. Holotypc (SU I 3949 1); STRIMPLE. H. L. 1968. A New Edri oastero id. Im\'{/ Arnd. Sci. Proc .. 73: adoral su rface of large spec imen. showin g well -preserved ambulacrals 260-262 . with both primary and second ary spi ne s. most or adoral half of one 1974. A Prel imin ary Stud y of Ec hinoderms wit h the Ai d of a intcrambulacrum . X 4.5. 7. Adapical surface or holotype illustrating Scann in g Electro n Mi croscope. Iowa Acad. Sci. Proc .. 81: 51 -55 . plate arrange ment or adapical half of an ambulacrum (left half or SWANN. D. H. 1963. Class ifi cati on of Ge neviev ian and Chesterian (Lale fi gure). several perforate ge nital plates (ri ght half) . exposed pm1ion of Mi ss iss ippi an) rocks of Illinois. Rep/.\". 111,·es. l//i11ois Geo/. Sur .. 216. 91 p. . a brace. and numerous tin y secondary spines. X 4 .5. I pl. https://scholarworks.uni.edu/pias/vol84/iss3/4 8