A Ground Sloth, Megalonyx, from a Pleistocene Site in Darke Co., Ohio1

A GROUND SLOTH, MEGALONYX, FROM A PLEISTOCENE SITE IN DARKE CO., OHIO1 RICHARD S. MILLS The Dayton Museum of Natural History, 2629 Ridge Ave., Dayton, Ohio MILLS, RICHARD s. A Ground Sloth, Mega- Missing parts of the skeleton have been lonyx, from a Pleistocene Site in Darke Co., Ohio. Ohio J. Sci. 75(3): 147, 1975. reproduced in plaster, and the entire Bones of a ground sloth, Megalonyx jeffersonii, skeleton has been painted black so it is were found by Mr. Lowell Carter on his farm difficult to determine the genuine from in Darke County, Ohio and reported to the reconstructed bones. Three "leg bones", Dayton Museum of Natural History. Sub- sequent digging by Dayton Museum personnel thought to be Megalonyx, were obtained resulted in recovery of 93 Megalonyx bones and from the Muddy Prairie Bog section 26, fragments. Comparison of this specimen with Amanda Township, Fairfield County, in other Megalonyx skeletons from Henderson, 1949. The present location of these Kentucky, and Powers County Idaho indicates that the Darke County Megalonyx is larger than bones is unknown to the author. Some any other Megalonyx yet reported. In addition scattered Megalonyx bones were found in this specimen contains bones that are not rep- a hackberry swamp near North Fairfield, resented in previously reported skeletons of M. Huron County. These specimens are in jeffersonii. A radiocarbon date of 12,190 ±215 years B.P. was determined for a wood fragment the collections of the Norwalk Historical (Picea) collected from marl containing sloth Museum (personal communication with bones. Jane Forsyth, 1974). During the summer of 1966 Mr. Fossil remains of the ground sloth, Lowell Carter of Ansonia, Darke County, Megalonyx, have been reported from Ohio dredged along the edge of one of the several Pleistocene sites in North Amer- kettle bogs on his property to obtain marl ica. At least ten species have been re- lime for his fields. While spreading marl ported (Leidy, 1855; Lindahl, 1893; on his fields one of the large leg bones of Cope, 1899; Lyon, 1938; Stovall, 1940; a ground sloth became wedged in his Stovall and McAnalty, 1950) most de- spreading machinery. This accident led scribed from fragmentary material. The to Mr. Carter's recovery of several other extent of variation within each species Megalonyx bones. Later in the same remains unknown (Scott, 1937). How- year Mr. Carter was dredging another ever, Bryan Patterson of Harvard Uni- kettle in the process of constructing a versity and David Webb of the Univer- fishing pond, when he uncovered the sity of Florida currently believe that M. skull of an adult female mastadon. He jeffersonii is the only valid post-Blancan contacted the Dayton Museum of Na- species (pers. comm. with Elaine Ander- tural History concerning the finds, and a son, 1974). party from the museum visited both sites. The museum began excavations there Three partial Megalonyx jeffersonii in the summer of 1970. A report of the (Desmarest) skeletons have been re- Carter mastadon site is in preparation. ported from Ohio. A partial skeleton was found on the farm of Abraham Museum personnel and volunteers dug Drushell in Berlin Township, Holmes through dredged up marl using hand County, in shell marl beneath six feet of tools. In addition the Mannix Con- black peaty soil. This skeleton was re- struction Co. was employed to redredge ported by Claypole (1891) and later de- the portion of the bog from which sloth scribed by Hay (1912). It was recon- bones had been recovered. A femur, a structed by the Ward Establishment, patella, a fibula, a fifth metatarsal, two Rochester, New York. The mounted first phlanges, one second phlange, one specimen is on display at Orton Hall, third phlange, a complete rib, a rib mid- Department of Geology and Mineralogy, section, a piece of vertebra, and one un- The Ohio State University, Columbus. identifiable bone fragment were found following the dredging. Although Mr. Manuscript received June 13, 1974 (74-22). Carter reported that approximately two 148 RICHARD S. MILLS Vol. 75 feet of organic peat covered the marl, all approximate the age of the skeleton. A Megalonyx bones and spruce (Picea) wood fragment (Picea) was carefully re- were found in dredged up chunks of marl. moved from the dredged marl and sent to A total of 93 Megalonyx bones and the University of Georgia Geochronology fragments were recovered from the site Laboratory. A date of 12,190 ± 215 along with the bones of muskrat (Ondatra years B. P. was determined for this zibethica), Canada beaver (Castor cana- specimen (Uga-666). This date approxi- densis), and white-tailed deer (Odocoileus mates the true age of the skeleton, since virginianus). These specimens are in the both the wood and the skeleton were re- geological collection of the Dayton Mu- moved from marl. seum of Natural History. The Mega- lonyx jejfersonii skeleton was exception- DESCRIPTION OF THE FAUNA ally well preserved and is one of the most Mr. Carter recovered only the largest complete skeletons reported of this spe- sloth bones while spreading marl on his cies. In addition, some of the sloth bones fields. Probably some of the smaller in this collection are not represented in bones were broken up and spread with other Megalonyx skeletons. the marl. Several additional bones were found by the museum field crew in the SITE DESCRIPTION marl. These included ribs, vertebrae, The site from which the sloth bones both scapulae, both patellae, a portion of were dredged is a kettle, or ice-block pelvis, both femora, both tibiae, and depression, formed in ground moraine several metapodials. A complete list of (personal communication with Jane For- Megalonyx bones recovered from the syth who visited the site in 1971) two site, including those collected by Mr. miles southwest of the Bloomer end Carter, follows: partial skull and lower moraine and five miles northeast of the jaw, one cervical vertebra, nine dorsal Union City end moraine. It is located vertebae, one lumbar vertebrae, one at 40° 12' north latitude, 84° 41' west caudal vertebra, both scapulae, left hu- longitude, in the S.W. l/i section 20, merus, left radius, left ulna, left clavical, Brown Township, Darke Co., Ohio seven complete ribs, 13 proximal rib (U.S.G.S. Ansonia 73^ minute quadran- ends, eight distal rib ends, nine rib mid- gle). An area of open water is bordered sections, both acetabulae and part of the on the east, south and west by bog vege- ilium of the pelvis, both femora, both tation. According to Mr. Carter the patellae, both tibiae, left fibula, one north bank of the pond was boggy but is calcanium, one scaphoid, one cuniform, now solid due to the construction in 1964 third, fourth, and fifth metatarsals, of a dirt road along this edge. The New scapho-trapezium, unciform, magnum, York Central railway line crosses the lunare, pisiform, index and auricular south edge of the pond; and Ohio Route metacarpals, four first phlanges, three 49 crosses it near the west edge. second phlanges, and four third or ungual Sloth bones were first discovered in phlanges. Measurements of the Darke 1966 the second time Mr. Carter dredged County sloth bones are compared with the north edge of the pond. Due to re- measurements of other Megalonyx skele- peated dredging the north bank of the tons from American Falls, Powers pond has been so disturbed that recogni- County, Idaho and Henderson, Kentucky tion of the original stratigraphy is impos- in table 1. sible. Bones found by the field crew of The partial skull appears to have been the Dayton Museum of Natural History damaged by the dredge just behind the were in marl, even though they had been cuniform aveolii. The skull was missing displaced from their original deposition teeth but the second right cheek tooth site. (M2) was later recovered from the marl. The premaxilla, nasals, palatine, jugal RADIOCARBON DATE and zygomatic arch of the right side are When sloth bones were located by the missing. Measurements for this partial 1973 dredging, it was thought that a skull are in table 1, and drawings appear radiocarbon date from the marl would in figures 1 and 2. No. 3 MEGALONYX FROM DARKE CO. OHIO 149 TABLE 1 Comparison of the Darke County, Ohio Megalonyx jeffersonii with M. jeffersonii from American Falls, Powers County, Idaho {personal communication with Elaine Anderson, 1973); and Henderson, Kentucky {Leidy, 1855). skull D.M.N.H.* I.S.U.M.** Henderson, Ky G-25699 23034 total length 340+ 290+ 355+ length from temporal fossa to postorbital protuberance 215 219 197 length of sagittal crest 140 109 127 breadth of inion at paramastoid 176 167 159 height of inion from foramen magnum 118 103 110 breadth of face at postorbital protuberance 150 137 127 breadth of cranium at narrowest part of temporal ridge 112 96 90 mandible D.M.N.H. I.S.U.M. Henderson, Ky G-25700 23034 total length 316 320 317 diastema length 43 46.6 42 depth of 1st alveolus 85 88 length of tooth row 154 146 width across diastema 60 55 — length 1st cheek tooth (Mi) 19 17.3 18 width 1st cheek tooth 26 23.6 24 length 2nd cheek tooth (M2) 18 17.4 width 2nd cheek tooth 26 25 length 3rd cheek tooth (M2) 20 18.3 18 width 3rd cheek tooth 27 26.3 24 femur D.M.N.H. I.S.U.M. Henderson, Ky G-25696 23043 total length 615 495 546 diameter of head 130 120 proximal width 210 212 — least shaft width 180 158 — width at middle of shaft 205 180 breadth at middle of shaft 61 62 distal width 275 255 260 humerus D.M.N.H.

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