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Curator of Fossil Invertebrates FIELDIANA: GEOLOGY VOLUME 12, NUMBER 3 Published by CHICAGO NATURAL HISTORY MUSEUM JANUARY 25, 1956 PRINTED IN THE UNITED STATES OF AMERICA BY CHICAGO NATURAL HISTORY MUSEUM PRESS Marine Fauna INTRODUCTION The occurrence of fossil invertebrates in the Middle Penn- sylvanian Francis Creek shale of Will and Grundy counties, Illinois, has been discussed (this volume, no. 1). The fauna is composed almost entirely of land and fresh-water forms, inhabiting a vegetated delta plain during submergence of a-coastal plain. There they were associated with the famous Mazon Creek flora. A very few fossils of marine animals are found in the spoil heaps of the strip mines, where the overburden of concretion-bearing Francis Creek shale has been piled, in mining for the underlying Number 2 (Wilmington) coal. Fossils of the plants and terrestrial invertebrates are common in the concretions. Marine forms known to me include a serpulid worm, an amphi- neuran, and a pectinoid clam, all described below; a trilobite, which Professor J. Marvin Weller once saw in a private collection but which I have not seen; a few teeth of xenacanth sharks and one fragment of shark cartilage; and one coiled cephalopod. As the cephalopod came to my attention while this paper was in press, I cannot include a description of it here. The marine fossils described below are excellently preserved; the pelecypod is represented by a fine impression of a single valve, scarcely worn, and the amphineuran is fully articulated. Such preservation indicates deposition under quiet conditions, with little or no transportation after death. This may be taken to indicate that a tongue of the invading sea advanced across the Mazon Creek deltaic plain briefly during Francis Creek time. The stratigraphic relations of the fossils have been obscured by the dumping of the entire thickness of the shale in spoil heaps during the mining, so it is not possible to determine whether the marine invasion occurred early or late in Francis Creek time. Since the marine fossils are very scarce in the fauna as a whole, it was probably a brief invasion, represented by only a thin bed of shale. ~The pelecypod specimen was found slightly south of the east- west road from Coal City to Wilmington (see map, fig. 3, this volume, 59 60 FIELDIANA: GEOLOGY, VOLUME 12 no. 1). The worm came from about two miles farther north, at about the point where the Santa Fe Railroad track crosses the Grundy-Will County line. It is probable that the marine tongue covered the entire strip-mining area. SYSTEMATIC DESCRIPTIONS Phylum ANNELIDA Class CHAETOPODA Family SERPULIDAE Howellitubus, new genus Straight or slightly bowed shell, composed of many layers ar- ranged as cones one within the other, circular or subcircular in cross section; tapering, with increasing flare at apertural end; shell thick apically, thin aperturally. Genotype.—Howellitubus whitfieldorum, new species. Remarks.—This genus is apparently very similar to the Cre- taceous genus Longitubus Howell (Howell, 1943, p. 161), from which, however, it differs in its definitely tapering form. Some specimens of Longitubus from the Merchantville clay (Upper Cretaceous of New Jersey) are also distinctly tapering (see fig. 32), but as these specimens are in the form of steinkerns, it is not unlikely that the tapering is caused by thickening of the shell apically, and that the outside of the tube may have been nearly parallel-sided. Two specimens of Serpula antiqua Sowerby from the Gault (Lower Creta- ceous) of England, CNHM nos. P3312 and P3318, show this con- dition, as does the specimen of Howellitubus described below. The new genus is distinguished from Serpula by its nearly straight form. The genus is named for Professor B. F. Howell, of Princeton University, in recognition of his work on fossil worms and his long encouragement of my work. Howellitubus whitfieldorum, new species Figure 33 Aside from the characters noted above as being probably of generic value, other characters of the species are: outer surface unornamented, inner surface with fine growth rings. The growth rings are not strictly transverse to the length of the tube, but rise in a low lobe on one side. The spaces between them are occupied by very fine longitudinal striae. RICHARDSON: MARINE FAUNA 61 Holotype.—Two halves of a concretion, with parts of the shell and the steinkern adhering to each. CNHM no. PE150. Collected in 1953 by Dr. and Mrs. Robert H. Whitfield and Mr. Jon S. Whit- field, and presented by them to the Museum. On or near the Will- Grundy County line, about 24% miles north of Braidwood, Illinois. Fig. 32. Longitubus lin- earis Howell, X 1.4; Upper Cre- taceous, New Jersey. CNHM no. PE3426. Fic. 33. Howellitubus whitfieldorum, new species, holotype. The specimen on the right, the counterpart of the other, is illu- minated from the right. Xx 1.1. CNHM no. PE150. (Coordinates F2.1, e4.3 on map, fig. 3, this volume, no. 1.) Length, as preserved, 38 mm.; greatest width, 4 mm.; width at narrow end, 2.3 mm. Remarks.—The trivial name is given in recognition of the contri- bution of the Whitfield family to our knowledge of the Mazon Creek fauna, through their tireless collecting in the strip-mine dumps, and through their generously donating their most significant specimens to the Museum. Phylum MOLLUSCA Class AMPHINEURA Order POL YPLACOPHORA Suborder EOPLACOPHORA Dall (1882) has reviewed the fossil genera of chitons; Quenstedt (1932a and b) has discussed some of them. The Paleozoic genera 62 FIELDIANA: GEOLOGY, VOLUME 12 are not adequately monographed, except for certain ones not rele- vant to the present discussion that were treated by Bergenhayn about ten years ago. As Iam not prepared to revise the diagnoses, I accept the classification used by Dechaseaux (1952) and the de- scriptions of Salter (1846) and Dall (1882). Helminthochiton Salter 1846 appears to be the genus to which the two known Illinois Penn- sylvanian chitons should be referred. Genus Helminthochiton Salter 1846 Helminthochiton was based on a Silurian species, griffithii Salter, described (Salter, 1846, p. 51) as follows: “‘... elongate; plates as long as wide, subquadrate, thin; apex of anal plate remote from its front edge; sustentacula [sutural laminae] widely separated; shell but very little covered by the mantle (mantle expanded, smooth, thin). Tropical?”’ Dall’s definition (1882, p. 280), from the manuscript of P. P. Carpenter, is essentially the same, with the addition of a note distinguishing the genus from Gryphochiton Dall. Dechaseaux (1952, p. 214), who places Gryphochiton in the synonymy of Helmin- thochiton, describes the genus as follows (translated): ‘‘Form slender —certain species have a length of 10 to 12 em. and a width of 24% cm.—-; plates thin, quadrangular; two small sutural laminae.” Quenstedt (1932a, p. 555), in defining his order Helminthochi- tonida, includes as a character, ‘‘Middle and lateral fields not yet differentiated.”” However, in our specimen and in those figured by de Koninck (1844, pl. 283) and Dechaseaux (1952, fig. 3) there is a faint differentiation due to a gentle fold radiating from the beak and not accompanied by a change of ornamentation. Salter (1846) noted that H. priscus (Miinster) was common in the Mississippian of Tournay, but as separated plates. _Articulated specimens, though rare, are occasionally found in marine sediments. Helminthochiton concinnus, new species Figures 34-36 This is the second Helminthochiton to be reported from the Pennsylvanian of Illinois, the first being Chiton carbonarius Stevens (Stevens, 1858, p. 264; Meek and Worthen, 1878, p. 608, pl. 29, fig. 15, a-h; Shimer and Shrock, 1944, p. 527, pl. 216, figs. 27-34). The ornamentation is apparently much the same in the two species, though Meek’s detail drawing is rather obscure. Stevens’ specimens RICHARDSON: MARINE FAUNA 63 (of dissociated valves) imply a chiton about twice as large as the single specimen here described. Description.—Shell about 434 times as long as wide, omitting the girdle. Anterior valve broadly rounded in front, longer than wide, shortest medially, overlapping the next valve. Anterior and body valves with elevated triangular areas probably overlying small Fic. 34. Helminthochiton concinnus, new species, holotype. Left, impression of under side of shell. Right, impression of upper surface of shell. Both xX 1.5. In collection of Mr. and Mrs. John M. McLuckie. sutural laminae of the valves behind; the sutural laminae not known. Tail valve about semicircular, with prominent keel termi- nating behind the center in a blunt mucro. Ornamentation of all valves consisting of concentric rows of fine tubercles and irregular fine concentric growth lines; no differentiation of ornament on lateral areas. Girdle unknown. Remarks.—The size difference between H. carbonarius and H. concinnus is not, of course, important, as we know nothing about individual growth in these species. The median valves of carbonarius are projected dorsally in an acute apex overlapping the next valve; the corresponding parts of the valves of concinnus are broken off, 64 FIELDIANA: GEOLOGY, VOLUME 12 Fic. 35. Helminthochiton concinnus, new species, holotype; detail, showing ornamentation; X 3.8. Fic. 86. Helminthochiton concinnus, new species, holotype; impression of radula on steinkern; X 4.5. but the position of the apex was probably anterior to the outer edge of each valve, to judge from the position of the folds bounding the lateral fields. The keel of the tail valve of concinnus extends farther back and is more bluntly terminated. The head valve of concinnus is perhaps slightly narrower. A groove in the anterior part of the impression of the under side of the shell is taken as representing the radula (fig. 36), the first known occurrence, so far as I am aware, of a radula in a Paleozoic mollusk. Under the microscope, it is seen to consist of parts of eight rows of small conical teeth. The radula is undoubtedly in- complete, so that we cannot say that this Helminthochiton had fewer than the seventeen rows of radular teeth typical of modern chitons. The radula is folded lengthwise and measures about 13 mm. in length and about 114 mm. in greatest width. The absence of a girdle in a specimen so well preserved—as in the entire specimens of H. priscus from Belgium—is_ probably RICHARDSON: MARINE FAUNA 65 related to the absence in this genus of insertion plates securing the girdle to the valves. S. S. Berry (1922, pp. 399-400) has remarked: ‘‘Chitons are not considered as having much importance as fossils, and, taking the world as a field, surprisingly few fossil species or even specimens have been brought to light and recorded. Yet there are reasons for believing that the members of this group, when they do occur, have an intrinsic value as paleontological criteria rather above that of most groups of Mollusca. At any rate, it is not altogether well to neglect them. . . . Both individually and in associations of species, these animals are remarkably definite in their latitudinal distri- bution; and... this definiteness of geographical area inhabited extends even more sharply to station as well. The bathymetric range of most chitons is curiously narrow.”’ 7 Holotype.—The type and only known specimen is in the personal collection of Mr. and Mrs. John M. McLuckie, in Coal City, Illinois, where it bears the number 3000-1.1. I am indebted to Mr. and Mrs. McLuckie for an extended loan of the specimen. Plaster casts are deposited in the fossil collections of Chicago Natural History Museum and Princeton University. The specimen is 55 mm. in length, measured along the slightly curved axis. Class PELECYPODA Order DYSODONTA Suborder PECTINACEA Aviculopecten mazonensis Worthen Figure 37 Aviculopecten mazonensis Worthen, 1890, Illinois Geol. Surv., 8, p. 117, pl. 22, fig. 9; N. D. Newell, 1937, State Geol. Surv. Kans., 10, p. 56, pl. 4, figs. 19-22. Both Mr. George Langford and Mr. John McLuckie have in- formed me that shells of pectinoid clams were formerly common in the small underground mine dumps south of the road from Coal City to Wilmington (see map, fig. 3, this volume, no. 1). The only specimen available to me, however, is an impression of a single right valve in the collection of Mr. and Mrs. John M. MecLuckie, in Coal City. It matches the figures and description in Newell’s paper (Newell, 1987) and is figured here simply to complete the record of the marine fauna of this deposit. 66 FIELDIANA: GEOLOGY, VOLUME 12 Newell cites fifteen specimens of this species, apparently from the Mazon Creek locality in Grundy County, but since specimens from the strip-mine dumps are commonly recorded as being from Mazon Creek, it is possible that some or many of those specimens are from the general vicinity of the one here figured. Fic. 37. Aviculopecten. mazonensis Worthen; two halves of a concretion bearing the impression of a right valve; approximately x 1. The figured specimen is in the McLuckie collection, Coal City. It was found in an underground mine dump at Diamond. (Co- ordinates F'1.0, g6.5, of map, fig. 3, this volume, no. 1.) REFERENCES BERRY, S. STILLMAN 1922. Fossil chitons of western North America. Proc. Calif. Acad. Sci., (4), 11, no. 18, pp. 399-526, pls. 1-16, figs. 1-11. DALL, WILLIAM HEALEY 1882. On the genera of chitons. Proc. U. S. Nat. Mus., 4, pp. 279-291. DECHASEAUX, COLETTE 1952. Classe des Amphineures, in PIVETEAU, J. (ed.), Traité de Paléont., 2, pp. 210-215, figs. 1-5. Paris. HOWELL, BENJAMIN F. 1948. Hamulus, “Falcula,’”’ and other Cretaceous Tubicola of New Jersey. Proc. Acad. Nat. Sci. Phila., 95, pp. 189-166. RICHARDSON: MARINE FAUNA 67 KONINCK, LAURENT G. DE 1844. Description des animaux fossiles qui se trouvent dans le terrain carbo- nifére de Belgique. iv + 650 pp., 55 pls. in Atlas. Liége. MEEK, FIELDING B., and WORTHEN, AMos H. 1873. Fossils of the Coal Measures. Geol. Surv. Illinois, 5, Geology and Paleontology, pt. 2, sec. 5, pp. 560-619, pls. 24-32. NEWELL, NORMAN D. 1937. Late Paleozoic pelecypods: Pectinacea. State Geol. Surv. Kansas, 10, 123 pp., 20 pls. in Atlas (1938). QUENSTEDT, WERNER 1932a. Loricata (Paliontologie). Handwéorterb. Naturwiss., 2nd ed., 6, pp. 552-555, figs. 1-3. 1932b. Die Geschichte der Chitonen und ihre allgemeine Bedeutung. Paleont. Zeitschr., 14, pp. 77-96, fig. 1. SALTER, JOHN W. 1846. Description of a fossil chiton from the Silurian rocks, with remarks on Se Sage species of the genus. Quart. Jour. Geol. Soc. (London), 3, pp. 48- » NYS. SHIMER, HERVEY W., and SHROCK, ROBERT R. 1944. Index fossils of North America. ix + 8387 pp., 303 pls. New York. STEVENS, R. P. 1858. Description of new Carboniferous fossils from the Appalachian, Illinois, and Michigan coal-fields. Amer. Jour. Sci. Arts, (2), 25, no. 74, pp. 258-265. WORTHEN, Amos H. 1890. Description of fossil invertebrates. Geol. Surv. Illinois, 8, Geology and Paleontology, pt. 2, sec. 1, pp. 69-154, pls. 9-28 in Atlas. fea 550.55 | co01 Peter FIELDIANA, GEOLOGY CHGO pera 12 1956/69 UNIVERSITY OF ILLINOIS-URBANA Huu 6 IMAM | 3 0112 026 Tra ee er a eT es “wikte sg hava TRINA Le iesah ovale ae Y