TULANE STUDIES TN GEOLOGY AND PALEONTOLOGY Volu me 22, Number 2 Sepl<'mber 20. l!J8~) PLIOCENE THREE-TOED HORSES FROM LOUISIANA. WITH COMMENTS ON THE CITRONELLE FORMATION EAHL M. MANNING MUSP.UM OF'GEOSCIF:NCE. LOUISJJ\NA STATE UNIVF:RSlTY. JJATO.\I ROI.JG/<. LOL'/S//\;\':1 and llRUCE J. MACFADDlrn DEJ>ARTM/<:NTOF NATUH/\LSCIENCES. F'LORJD/\ MUSf:UM Of<'NJ\TUIV\/, lllSTOUY UNIVERSITY OF FLOH!IJJ\. GJ\/NESVlU.E. Fl.OH/DA CONTENTS Page T. ABSTRACT 3.5 II INTRODUCTION :l5 Ill. ACKNOWLEDGMENTS :rn TV . ABBREVIATIONS :l7 V. SYSTEMATIC PALEONTOLOGY ;37 VI. AGE OF THE TUNICA HILLS HIPPARIONINES 38 VIL STRATIGRAPHIC PROVENIENCE 38 Vlll. PLIOCENE TERRESTRIAL VERTEBRATES OF THE GULF AND ATLANTIC COASTAL PLAIN .JO IX. COMMENTS ON THE CITRONELLE FORMATION .JI X. AGE OF THE CITRONELLE 42 XL TH E CITRONELLE FORMATION IN nm TUNICA HILLS .t:1 XII. LITERATURE CITED l.J January of 1985, the senior author was L ABSTRACT shown a large collection of late Pleistocene Teeth and metacarpals of early Pliocene (Rancholabrean land-mammal agel ver­ (latest Hemphillian land-mammal age) tebrate fossils from the Tunica Hills of three-toed (hipparionine) horses are de­ Louisiana (Fig. I) by Dr. A. Bradley scribed from the Tunica Hills of West McPherson of Centenary College, Feliciana Parish in east-central Louisiana. Shreveport. McPherson and Mr. Bill Lee An upper molar perta ins to Nannippus of Balon Rouge had collected fossils from minor, known from the Hcmphillian of that area since about 1981. Among the Central and North America, and two teeth standard assemblage of Rancholabrean and two distal metacarpals pertain to a re­ taxa (e.g. mastodon, horse, ground sloth, cenlly described species of Cormohippar­ tapir and bison) were an upper molar and ion, C. emsliei, known only from Pliocene distal metacarpal of very small horses col (latest Hemphil\ian and Blancan land \ected by them in 1983, which were quite mammal ages) sites in peninsular Florida. different from the common large Equus of T he material represents the first record of the fauna. In 1986 Mc Pherson and Lel:- col Pliocen e non-marine fossils from Louisi­ lectcd two more teeth and anolhPr distal ana as well as the first record of' a fossil metacarpal of a small. primitive' horse. hor~e from the sta te oth er than Pleistocene These fi\'l' spt•cimens arL', thus for th<.• Equus. Found in sur face stream gravels, only record of a pre-lat<.• Pk•istoeenc fauna the horses proba bly were derived from the among the hundreds of verU_•bratc fossils otherwise a lmost nonvertcbrate-bcaring that havt• been found m tfw Tunica Hills Citronelle Forma tion. area. Thev indicate the presence of ter restnal or. near-shore early Pliocene de posits in Louisiana. The purpose of' the II. INTRODUCTION present study is to describ<.• this matt.•nal Fossil land mammals of pre-Pleistocene and to discuss its irnplications for Louisiana age a rc exceedingly rare in Louisiana. In biochron(Jlogy and stratigrapl1y 35 36 Tulane Studies in Geology cmd Paleontology Vol. 22 e1°3o'w 90°W {( • P1nckneyv1lle MISS. LA. Bluff LOCALITIES 30°45'N 0-- - 6 KM e1 °3o'w Figure 1. Location of the Pliocene horse sites a nd the Tunica Hills, West F eliciana Parish, Louisiana and Wilkinson County, Mississippi. Modified from Givens and Givens (1987, fig. ! ) and Alford et al. (1983, fig. l ). III. ACKNOWLEDGMENTS Tunica Hills, the mate ria l would never have come to light. Dr. R ichard C. Hul­ The authors a re e specially grateful to bert, Jr. (U niversity of Florida , Gaines­ Dr. A. Bradley McPherson of Shreveport ville) k indly allowed us the use of a the n and Mr. Bill L ee of Baton Rouge for per· unpublished manuscript on Coastal P lain mission to describe these specimens. With­ horses that was critical to the present study out their persistanl collecting efforts in the a nd also provided useful discussion of o ur No. 2 Louisiana Pliocene Horses 37 identifications. Dr. Frank Whitm ore (U.S. Feliciana Parish. east-central Louisiana (Fig. lJ. Geological Survey, Washington, D. C.) gra­ From surface stream gravel, probably derived ciously permitted one of u s (EMM) to from the Citronelle Formation (see discussion examine the fascinating Mauvilla fauna of below). Alabama. Dr. Richard Kese l (L SU Depart­ Age. Early Pliocene (latest Hemphillianl. ment of Geography and Anthropology, Discussion: The dental pattern in the Baton Rouge) examined the sites where Louisiana specimens exhibits the diagnos­ the specimens were found, and provided tic characters listed in Hulbert (19871. The useful information on the stratigraphy of parastyle and mesostyles are grooved on the area. Dr. Whitney J. Autin (Louisiana the anterior side. The fossette borders are Geological Survey, Baton Rouge) re­ richly plicated with a count of 4-5 + 4-1. viewed the manuscript, and provided The pli caballin consists of a large fold with many helpful comments . T he manuscript five secondary folds. The hypoconal was also reviewed by Dr . Judith A. groove is moderately deep. The protocone Schiebout (LSU Museum of Geoscience, is elongate with a concave lingual side. Baton Rouge). This is University of Florida The tooth is in middle wear and seems Contribution to Paleobiology number 321. moderately hypsodont (Table 1 ). The lower tooth, a right P 2 , exhibits a IV. ABBREVIATIONS diagnostic anterior extension of the Fossil collections refe rred to in the text metaconid that connects to the posterior are: CCVC - Centenary College Vertebrate portion of the paraconid. The protoconid Collection, Biology De partment, Cente­ and hypoconid are flattened and there is a nary College, Shreve port LA; UF - Ver­ prominent pli caballinid. Although the size tebrate Paleontology Collection, Florida of the Louisiana sample is smaller than the State Museum, University of Florida, type from the Blancan, it falls within the Gainesville, Florida. size range published by Hulbert (19871 for the large sample from the late Hemphillian upper Bone Valley Formation. V. SYSTEMATIC P ALEONTOLOGY There are two distal metacarpals, CCVP 86 (Fig. 3) and 535, from the Tunica Hills Class MAMMALIA L innaeus, 1758 that seem to be referable to Cormohippar­ Order PERISSODACTYLA Owen, 1848 ion emsliei based on the primitive (hip­ Family EQUIDAE Gray, 1821 parionine) aspect of the distal tuberosities Subfamily EQUINAE Gray, 1821 (26.9 and 28.9 mm) being greater than the Genus CORMOHIPPARION width of the distal articular keel (26.4 and Skinner & Ma c F adden, 1977 27.3 mm; see Hussain, 1975) and similar CoRMOIIIPPARION F:MSLH:I Hulbert, 1987 proportions to that of probable C. emsliei Figures 2 c-f, 3, Table 1 metapodials from the Bone Valley. Distribution: Early P li ocene {latest Hemphil­ Because North American horse species lian land-mammal age) of the upper Bone Valley are generally widespread in geographic Formation, Polk Co. , central peninsular distribution, the occurrence of C. emsliei Florida; late Pliocene (late Blancan land mam­ in only Florida and Louisiana suggests that mal age), of the Pine crest beds, Macasphalt it is an unusual, regional endemic species Shel! Pit, 3 km N of F ruitvill e (type localiiy), of the late Cenozoic Gulf Coastal savanna. Sarasota Co., west-centra l peninsular Florida; and the Tunica Hills area, West Feliciana Genus NANNIPPUS Matthew, 1926 Parish, east-central Louisiana. NANNIPPUS >!!NOH (Sellards, 1916) Referred Louisiana specimens: CCVC 1628, Figures 2 a-b, Table 1 right P 3 or P 4 ; CCVC 1627 , right P:,:; CCVC 86 and CCVC 535, distal ends of MC III. <Casts of Distribution. Earlv Pliocene liate Hemphil­ the first three specimens are deposited in the lianl of Central and s~uthern North Amei·ica UF and LSU Museum of Geosciencc collec­ Referred Louisiana specimen. CCVC 585. Jett tions.) M". Site. age and strntmn: See description above Site location: South border of sect. 62 and for Cornwhipparion emsliei northern half of sect. 78 (irregula r sections), TIS, R4W, Tunica 7 112 min. Quad., Tunica Discussion: The tooth (Fig. 2, Table 1) is Bayou, Tunica Hills area, NW par t of West too small to be allocated to Cormohipparion 38 Tu lane Studies in Geology and Paleontology Vol. 22 TABLE 1 Measurements (in mm) of the teeth of Pliocene three-toed horses from the Tunica Hills. Greatest antero- Greatest transverse Height posterior length width (excluding (upper-mesostyle; Specimen No. Element (excluding cement) cement) lower-paraconid) Cormohipparion emsliei ccvc 1628 RP' or P 4 18.8 17.0 37 .5 ccvc 1627 RP2 20.6 9.0 30.4 Nannippus minor ccvc 585 LM 2 16.5 15.0 35.7 emsliei. Although broken on the occlusal reviews in Domning, 1969 and Lowery, surface, the parastyle and metastyle seem 1974). Recent work has shown that nearly unconstricted. The fossettes are moder­ all of the vertebrates have derived from ately plicated (3-3-4-2). There is a well de­ low level (Tl) terrace deposits of late Pleis­ veloped pli caballin. The protoconc is elon­ tocene age (Givens and Givens, 1987). No gate with a concave lingual border. This older vertebrates have previously been re­ tooth, which is in middle wear stage, ported from the area. seems too low-crowned to be referable to The fossil horse material described here Nannippus peninsulatus (senior synonym was found loose in the surface stream of N. phlegon). It falls within the large end gravel along Tunica Bayou (Fig. 1), as are of the observed range and has a dental pat­ most vertebrate fossils from the Tunica tern consistent with that of Nannippus Hills. In situ recovery of vertebrates is un­ minor (MacFadden, 1984; Hulbert, 1987). common and the discovery of even par­ tially articulated material (such as the par­ VI.