— — _‘ — = - — .— — — .— — — —. — — rwfiSis MWHI lllJlllllllHlllllllllllllllllllllllllllll 300903 1026 ll This is to certify that the thesis entitled HERPETOFAUNA OF THE ALBERT AHRENS LOCAL FAUNA (PLEISTOCENE:IRVINGTONIAN), NEBRASKA presented by Kenneth M. Ford III has been accepted towards fulfillment of the requirements for _uaster_5_- ' degree in _Genlnq¥__. //%% rofessor [hue Navember, 1992 0-7639 MS U is an Affirmative Action/Equal Opportunity Institution - W — .m— LIBRARY Mlchlgan State University PLACE IN RETURN BOX to remove this checkout from your record. TO AVOID FINES return on or before date due. DATE DUE DATE DUE DATE DUE l MSU to An Affirmdive Action/Equal Opportunity Institution ommflt HERPETOFAUNA OF THE ALBERT AHRENS LOCAL FAUNA (PLEISTOCENE:IRVINGTONIAN), NEBRASKA BY Kenneth M. Ford III A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Geological Sciences 1992 ABSTRACT HERPETOFAUNA OF THE ALBERT AHRENS LOCAL FAUNA (PLEISTOCENE:IRVINGTONIAN), NEBRASKA By Kenneth M. Ford III A fossil herpetofauna from the Albert Ahrens local fauna in south-central Nebraska is the most diverse Irvingtonian herpetofauna known from the Great Plains. The fauna is from deposits thought to be derived from Kansan glaciations and contains a total of thirty-one species, including two salamanders, ten anurans, two turtles, one lizard, and sixteen snakes. Bang blaizi is reported for the first time in the fossil record. Anbxgtgma lateralg, Bang gylggtiga, and Elana; gulpina occured south of their modern ranges, but Egggggggig glgzki occurs north of its modern range. These fossil distributions suggest that the Albert Ahrens climate was milder than the modern one and thus support the Pleistocene Climatic Equability Model. The herpetofauna suggests that the site of deposition was a wooded stream with some nearby grassland. To my grandparents iii ACKNOWLEDGEMENTS I would first like to acknowledge the assistance of my chairman, Dr. J. Alan Holman, with editing several drafts of this thesis. He and Drs. Ralph Taggert and Graham Larson read the final draft of the thesis and were very patient and helpful in other aspects of the program. Dr. Micheal Voorhies and Mr. George Corner are extended thanks for allowing me the opportunity to study this very interesting fauna and to join them at the Albert Ahrens site during the 1991 field season. I also thank Albert and Helen Ahrens and David, Lavena, and TaeRee Sellers for their hospitality during the summer of 1991. I appreciate the assistance of Dan Brinkman and Ken Andrews in accessing the comparative collection at The Michigan State University Museum. Mr. Andrews also assisted with the identification of turtle fossils. The talents of Kathleen Ford and Paula Lomnicki provided the figures of fossils in this thesis. They and my other academic cohorts, Greg Wasserman, Jeff Berntsen, Jamie DeWitt, Laura Abraczinskas, Lisa Hallock, Nancy Stevens, and John-Paul Zonneveld, are also thanked for making this process enjoyable. iv V I would finally like to thank my parents for their support, understanding, and love. TABLE OF CONTENTS LIST OF TABI‘ES O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O Vii LIST OF FIGURES O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O Viii INTRODUflION. O O O O O O O O O O O O O O O O O O C O O O O O O O O O O O O O O O O O O O O O O O O O O O 1 The Albert Ahrens local fauna...........................1 Pleistocene stratigraphy................................2 Checklist of the Amphibians and Reptiles................3 SYSTEMATIC PAIDEONTOWYOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOS Class Amphibia Order Caudata Family Ambystomatidae........ ........ ..............5 Order Anura Family Pelobatidae.................................8 Family Bufonidae...................................8 Family Hylidae........................... ...... ...10 Family Ranidae................. ....... . ..... ......11 Class Reptilia Order Testudines Family Chelydridae................................13 Family Emydidae...................................15 Order Squamata Family Scincidae..................................17 Family Colubridae Subfamily Colubrinae............................17 Subfamily Natricinae............................19 Subfamily Xenodontinae..........................23 Family Viperidae................ ......... .........24 DISCIJSSIONOO0.0...OOOOOOOOOOOOOOOOOOOOO ......... 0.0.0.0...27 Paleoclimatic interpretations..........................29 Ranid Taphonomy. O O O O O O O O O O O O I O O O O O O O ....... O ....... O O I O 34 Depositional Environment...............................35 CONCIDSIONOOOOOOOOOOOOOOOOOOOOOOOOOO OOOOOOOOOOOOO 000......38 LIST OF REFERENCESOOOOOOOOOOOOOOOO0.0.0.0000...0.0.0.0....39 vi LIST OF TABLES Table 1 Herpetofauna from caves in the eastern united stateBOOOOOOOOOOOOOOOOOI.00.0.0000000000028 Table 2 Geographic breakdown of extralimital amphibian and reptile species in the Albert Ahrens local fauna.......................32 Table 3 Habitat preferences and abundances of amphibian and reptile species in the Albert Ahrens local fauna.......................37 vii Figure Figure Figure Figure Figure Figure LIST OF FIGURES Left ilium of Maori: cf. 2. 91:11:31 (MSU VP 1365) in lateral view...................14 Left ilium of Rana gylyatigg (MSU VP 1369) in lateral view.................................14 Entoplastron of Chryggmys plot; of. C. p. belli (UNSM 76416) in ventral view..............16 Trunk vertebra of Regina grangmi (UNSM 76424) in lateral view................... ....... 21 Trunk vertebra of Elaphg yulpina (UNSM 76420) in lateral view..........................21 Area of sympatry for the Albert Ahrens herpetOfaunaOOOOOOOOOOOOOOOOOOOOOOOOOO ..... 0.00.33 viii INTRODUCTION The Irvingtonian herpetofauna is known mainly from several cave faunas in the eastern and south-central United States. These assemblages tend to reflect the modern fauna of the locality more closely than do associated mammalian faunas (Holman and Grady, 1989) and suggest that the Irvingtonian climate may have been more equable than originally thought (Holman, 1980). A large, recently discovered Irvingtonian herpetofauna from Nuckolls County in south-central Nebraska provides an opportunity to compare the herpetofauna with the mammalian fauna of the Central Plains and is the subject of this thesis. The Albert Ahrens local fauna.-The Albert Ahrens fossil locality (University of Nebraska, State Museum site No 104) is located within the E8 SEA Sec. 14 T3N R6W on the Oak, Nebraska 7% minute quadrangle. The site was discovered in a gully by Mr. Albert Ahrens of Angus, Nebraska, after whom the fauna is named. Fossils were collected by crews from the University of Nebraska State Museum during the summers of 1990 and 1991 using standard micro-vertebrate collecting techniques (Hibbard, 1949). Fish, bird, and mammal fossils were recovered as well as the fossil amphibians and reptiles 2 of this report. Mammal fossils are being studied by M.R. Voorhies and R.G. Corner of the University of Nebraska State Museum. Sediment from the skull of a juvenile mammoth provided a pollen sample now being studied by M.R. Bolick, also of the University of Nebraska State Museum. Most micro-vertebrate fossils were recovered from the base of a white to grayish silt bounded above and below by unfossiliferous red loess deposits. The upper loess/silt contact is conformable, but the lower loess was cut by channels approximately one meter deep. The fossils, yellow, red, and black clay nodules, and carbonate concretions, occurred in lenticular, gravel crossbeds 2-10 cm thick that terminated at or near the base of the channel deposits. Macro-vertebrate fossils were found in the channels as well as higher in the silt. Pleistocene etretigraphy.-The lower loess overlies a thick volcanic ash deposit which is thought to be the Pearlette type 0 volcanic ash. The type 0 ash has been dated at 610 ka by fission track dating (Izett, 1981). The fauna is thus thought to be at about 500 ka (Voorhies, pers. comm.). Preliminary study of the mammalian fauna suggests that the Albert Ahrens local fauna is similar to the Cudahy fauna (Voorhies and Corner, 1991). Hibbard (1970) considered the Cudahy fauna, which occurs below the type 0 ash, as representing the Kansan glacial stage, but for the reasons discussed below, the traditional Pleistocene stage names will be used only informally. Differing and inconsistent use of stratigraphic names has caused the traditional North American glacial and interglacial nomenclature to be abandoned (for review see Aber, 1991). Schultz et a1. (1978) attempted to divide the Irvingtonian Land Mammal Age into two substages, the Sheridanian and Sappan, and a third Sheridanian and Sap was later added for the medial Irvingtonian (Lundelius et al., 1987). None of these names are in current use. A till stratigraphy has been developed for the lower and middle (pre-Illinoian) Pleistocene of the Central Plains (Hallberg, 1986). Based on relative stratigraphic position to the Pearlette type 0, the Albert Ahrens fossil beds are equivalent to the type A1 till which is the classic "Kansas till" of Iowa (Hallberg, 1986). The type "Kansas till” of Kansas is found below the type 0 (Aber, 1991). Checklist of the Amphibians and Reptiles.-Species identified in this thesis are listed below. Common names of species follow Collins (1990). The basis for species identifications is given below in the Systematic Paleontology. Ampystgma cf. A. lateral: Blue-spotted Salamander Ambxstoma tisrinnm Tiger Salamander Ambxstoma sp- aceshignus bombifrons Plains Spadefoot fluid ameriganus American Toad figfig goggatgs Great Plains Toad Bufo goodhousii soodhonsii Woodhouse's Toad 5219 SP- Efigggggzis cf. 2. glgzki Spotted Chorus Frog Hxla xersisglor Gray Treefrog or H. srxsosselis Bans satesheiana Bullfrog Rana clamitans Green Frog Plains Leopard Frog Wood Frog Snapping Turtle Western Painted Turtle Great Plains Skink Racer Rat or Corn Snake Fox Snake Milk Snake Northern Water Snake Graham's Crawfish Snake Brown or Redbelly Snake Western Ribbon Snake Plains Garter Snake Common Garter Snake Eastern Hognose Snake Western Hognose Snake Copperhead or Cottonmouth Timber Rattlesnake Western Rattlesnake Massasauga SYSTEMATIC PALEONTOLOGY Fossils collected in the 1990 field season are in the collections of the University of Nebraska State Museum (UNSM). Fossils collected in 1991 are housed at the Michigan State University Museum (MSU VP). Class Amphibia Order Caudata Family Ambystomatidae Ambystoma cf. A. laterals Meterinl.~13 vertebrae (UNSM 76400), 1 vertebra (MSU VP 1356). Remarks.-The vertebrae of the A. mggulgtgm-group of Ambystgmg are the most elongate of the genus (see ratios in Tihen, 1958:19) and have a depressed neural arch (Rogers, 1984). Holman and Grady (1987) and Rogers (1984) separate the A- ietfersonianum-complex (A. ieffersonianum. A. laterals. A- nlatineum. A. tremblxi) from A- masulatum (the other member of the A. magulatgm-group) based on two characters: in A. magglatgm the neural arch often extends past the zygapophyses and the area of the postzygapophyses is wide, while in the A. jgffiersgniang-complex the neural arch ends anterior to the most posterior extent of the 6 postzygapophyses and the postzygapophyseal area is narrow. 0f the species in the A. jaffiaxagnlannm-complex, vertebrae of seven recent A. lagazala are identical in size to the Ahrens vertebrae. None of the members of the A. jafjazagnlannn-complex presently occur in Nebraska. The western border of the ranges of Ambyatgma iaffiazaanlannm and A. latazala runs from central Minnesota through Wisconsin, northern Illinois, and Indiana to north-central Kentucky, with an isolated colony of A. latazala in eastern Iowa, about 600 km to the north- east of Nuckolls County (Conant and Collins, 1991). maximum Material.-1 right dentary, 1 left dentary, 32 vertebrae (UNSM 76401), 4 vertebrae (UNSM 76402), 13 vertebrae (MSU VP 1357), 5 vertebrae (MSU VP 1358). Remarks.-The dentaries of adults of the subgenus Ambyaggma have a flange on the lingual edge (Tihen, 1958:33). As the Ahrens dentaries have these flanges and are of similar size to recent dentaries of A. tlgrlnnm, they are assigned to A. tlgzlnam. The vertebrae of A. glgzlnan are distinguished by their short, wide shape, large size, and upswept neural arch extending past the centrum (Tihen, 1958; Holman, 1969). Nine vertebrae from this locality (UNSM 76402 and MSU VP 1358) have a perforate centrum which Tihen (1942) found characteristic of larvae and recently metamorphosed adults. Some fossil and recent populations of neotenic A. tlgalnam 7 also fail to develop a septum in the centrum (Holman, 1975; Rogers, 1985). While this appeared to be age independent in a recent sample from Colorado (Rogers, 1985), Tihen (1942, 1958) found this to be an unreliable character in some recent skeletons as older neotenes in his sample had developed septa (Tihen, 1942). These eight vertebrae are similar in size to recent A. tlgxlnan and to all other A. glazingn vertebrae thus far collected from the site. Since neotenic vertebrae are usually larger than those of normal adults (Tihen, 1942, 1958; Holman, 1975), it is questionable that neotenic A. tlgzlnam were present in the Albert Ahrens fauna. Tiger Salamanders occur throughout Nebraska today as both normal and neotenic adults (Lynch, 1985). Lynch (1985) reports the species in Nuckolls County, and a normal adult was spotted in a pump house at the UNSM campsite in Oak. They are commonly found under rocks or in burrows and may be seen on rainy spring nights during their breeding season (Lynch, 1985). Ambyatgma sp. indet. Materiel.-14 vertebrae (UNSM 76403), 12 vertebrae (MSU VP 1359). Remarks.-This material is too fragmentary to assign to the specific level. 8 Order Anura Family Pelobatidae Seanhienns hombifrens Materiel.-2 left ilia (UNSM 76404), 4 left and 4 right ilia (MSU VP 1360). Remarks.-The ilia of the subgenus Saga can be distinguished from the subgenus Sgapnlgpaa by a weak or absent dorsal rim on the acetabulum and a wide ventral acetabular expansion (Chantell, 1971). The Ahrens ilia are similar to Saga and especially those of recent agapnlgpaa bgnhlfzana in that the dorsal prominance is reduced or absent (Holman, 1987c). Lynch (1985) reports Sgaphlapaa hamblfrana from Nuckolls County. Family Bufonidae bnfo amerieanus Mmteriel.-6 left and 5 right ilia (UNSM 76405), 8 left and 2 right ilia (MSU VP 1361). Remerks.-The dorsal protuberence of the ilium of 3319 anaglganna has a long base compared to that of E. gaggnggall figglazl (Holman, 1967; Wilson, 1975). Both are otherwise similar in having a much lower protuberence than either 5- u. noodhonsii or B. cognates (Tihen. 1962)- Bufo emerisanns is today found in Sharpy County, Nebraska approximately 175 km northeast of Nuckolls County (Lynch, 1985). The species tolerates a wide range of habitats but requires moist hiding places and shallow bodies of water for breeding (Conant and Collins, 1991). 9 buts segnatus Msteriel.-13 left and 9 right ilia, 1 sacrum (UNSM 76406), 19 left and 17 right ilia (MSU VP 1362). Remerks.-While indistinguishable from each other based on ilial characteristics (Holman, 1964, 1969), £319 QQQDAIHE and B. apaglgaaa can be separated from other members of 33:9 on the great height of the dorsal protrbence (Holman, 1969). Holman (1971) found that the sacral condyles of n. aggnatga end only slight posterior to the neural arch, whereas those of 3. w. gagghgaall and B. apaglgaaa extend well past the neural arch. The Ahrens fossils are similar in these respects to B. gagnataa. fiafg ggqnataa is not reported as occurring in Nuckolls County, but its wide range in Nebraska and Kansas suggests that it should be found there (Collins, 1974, Lynch, 1985). Conant and Collins (1991:313) refer to this toad as '...an accomplished burrower...often found... in river bottoms or floodplains." Bufo gogdhonsii floodhossii Meterie1.-2 left and 11 right ilia (UNSM 76407), 22 left and 15 right ilia (MSU VP 1363). Ra-arkI--The ilia of 92:9 neodhonsii soodhonsii have a dorsal protuberence which is intermediate in height between Ania gagnatna and a. apaalgaaa on one hand and B. amarlganaa and B. y. fgwlari on the other (Tihen, 1962; Holman, 1971). Also, the anterior angle of the dorsal protuberence is, in general, steeper than the posterior angle, whereas the two angles of the dorsal protuberence are generally subequal in 10 B. QQQDASQE (Tihen, 1962). The fossil ilia are identical to 3. g. yagdhggall in these respects. This toad is found today in Nuckolls county (Lynch, 1985). This species.can tolerate many a wide range of conditions, preferring lowlands and sandy habitats (Collins, 1974, Conant and Collins, 1991). ‘ Ania sp. indet. Meteriel.-6 left and 5 right ilia (UNSM 76408), 3 left and 5 right ilia (MSU VP 1364). Remarks.-This material is too fragmentary to assign to the specific level. Family Hylidae WOLF-9.12231 (Figure 1) Material.-1 left ilium (MSU VP 1365). Remerk.-This ilium is most similar to 2. glankl in having a wide, convex ventral actabular expansion (Chantell, 1968) which meets the ilial shaft at a near right angle. The dorsal protruberence is bulbous (Chantell, 1964) and directed slightly laterally in this fossil. Eaanaaazla glarkl is today found as far north as central Kansas, about 110 km to the south of Nuckolls County, inhabiting open grasslands and the edges of woodlands (Collins, 1974). Human-malls Materiel.-2 right and 1 left ilia (UNSM 76409). Remarks.-The ilia of both Hyla glaaraa and n. yazalgglg: have a low, smooth dorsal prominence and a wide 11 ventral acetabular expansion which forms an obtuse angle with the ilial shaft (Chantell, 1964; Wilson, 1968). The fossils are similar to recent H. yaralggla; in that the dorsal prominence is slightly anterior to the anterior border of the acetabulum, but in n. glnazaa, the dorsal prominence is about even with the acetabulum. Kyla yazalgglaz and H. gryagagalla are cryptic species and are distinguished primarily by ploidy and mating call. Both species inhabit trees and low shrubs in woodland areas. nyla ghryaaaaaalla is found about 45 km east of Nuckolls County today (Lynch, 1985). Family Ranidae mm Msterial.-66 left and 67 right ilia (UNSM 76410), 44 left and 28 right ilia (MSU VP 1366). Remarks.-The ilia of the Rana gataabalana have a precipitous slope on the posterodorsal border of the ilial crest and a porous area near the acetabular border which is most notable in smaller specimens (Holman, 1965a, 1984). Rana gataahalana is currently found in Nuckolls County (Lynch, 1985). This species is aquatic with a preference for deep, permanent water. Ranaslamitans Meterial.—12 left and 18 right ilia (UNSM 76411), 41 left and 45 right ilia (MSU VP 1367). Remarks.-The ilia of R. glamltana are similar to B. gagaabalana in having a preciptious slope to the 12 posterodorsal border of the ilial crest. Rana glamltang can be distinguished by its less rugged vastus prominence, lack of a porous acetabular expansion, and smaller size (Holman, 1967; Holman and Grady, 1987). The upper portion of the vastus prominence is flattened and proximally folded in mature B. glamltana. In small 3. Qataahalana, the vastus prominence is flattened but upright. Rana glanlnana is currently found about 370 km east of Nuckolls County. It is common in streams and other shallow fresh waters (Conant and Collins, 1991). Banacf. 8- mm Material.-135 left and 158 right ilia (UNSM 76412), 464 left and 443 right ilia (MSU VP 1368). Remarks.-The ilia of the Rana plplana-complex have a gentle slope to the posterodorsal border of the ilial crest (Holman, 19653). Two species from the B. plplana-complex, Rana plalzl and B. plplana, are currently found in Nebraska with 3. plalzl reported from Nuckolls County (Lynch, 1985). Though the species in the Raga plplana-complex are cosmopolitan in habitat, the distribution of modern 3. hlalxl is linked to loess soils in their Nebraska range (Lynch, 1978). As the sediments within and underlying the fossil horizon are silt, it is possible to tentatively refer the fossils to B. blalrl. This is the first report of Rana hlalzl in the fossil record. 13 Bans exlxatica (Figure 2) Meterial.-42 left and 45 right ilia (UNSM 76413), 20 left and 20 right ilia (MSU VP 1369). Remarks.-A member of the Rana plplana-group (sensu Holman, 1965a), Rana aylyatlga can be distinguished by the dorsal prominence which develops on the lateral surface of the ilium (Holman, 1984). This extralimital frog is. found today over a wide range to the north and east of the Albert Ahrens site, about 600 km at it closest. It is principally a frog of moist woodlands and can travel some distance from water (Conant and Collins, 1991). Rana sp. indet. Material.-345 left and 460 right ilia (UNSM 76414), (usu VP 1370). Remarks.-This material is too fragmentary to assign to the specific level. Class Reptilia Order Testudines Family Chelydridae shelxdra serpentine Material.- 1 hyiod, 1 left tibia, 1 left fibula, 1 left femur, and 2 tail vertebra (UNSM 76415), 1 neck vertebra, 1 right humerus, 1 right hypoplastron, and 3 costal fragments (MSU VP 1371). Remarks.-The skeleton of this species is very distinct (Holman and Schloeder, 1991). The fossils are l4 '—."‘ 2mm Figure 1 Left ilium of Eseudacris cf. 2. Clark; (MSU VP 1365) in lateral view. k———4 2mm Figure 2 Left ilium of Rana svlvatica (MSU VP 1369) in lateral view. 15 indistinguishable from recent gnalygza gargantlna and are assigned to this species. ghalygra aarpanfilna is known from Nuckolls County and is found throughout Nebraska in most permanent bodies of water (Lynch, 1985). Family Emydidae Qhrxsemxs Piste cf. Q-n- belli (Figure 3) Material.- 1 entoplastron (UNSM 76416), 1 peripheral (MSU VP 1372). Remarks.-The fossil turtle shell elements lack sculpturing as in Baaaamya or Ixagnamya (Holman and Sullivan, 1981; Holman, 1990). The entoplastron (Figure 3) has a bell shape similar to gzapgamya, but the pattern of the gular and hemeral scutes run towards the skirt of the bell in fizaptamya, whereas the trace of these scutes on the Ahrens fossil extends to the anterior corners. The latter pattern is found in Chryaamya plata. The smaller subspecies of Q. pigga have entoplastra that are subtriangular in shape, but the entoplastron of Q. n. balll is bell-shaped similar to the fossil. The peripheral is similar to C. pigta in having a straight border to the marginal scute with only a slight dimple at its junction with the pleural scute border. ghzyaamya plaga halll is distributed throughout Nebraska and Kansas (Collins, 1974; Lynch, 1985). They prefer heavily vegetated and shallow waters with muddy bottoms (Conant and Collins, 1991). 16 )——-l lcm Figure 3 Entoplastron of gngyaamya plgga cf. 9. p. balll (UNSM 76416) in ventral view. 17 Order Squamata Family Scincidae Eumeses obsoletus Material.-4 maxilla fragments (UNSM 76417), 2 dentaries (MSU VP 1373). Remarks.-The teeth of Eamagaa ghaglataa are robust and taper to a pigmented tip (Etheridge, 1958; Holman and Schloeder, 1991). These fossils are similar to E. abaglagna in these characters and in size. Nuckolls County is at the northern-most tip of this species’ modern range (Lynch, 1985). It inhabits grasslands with fine soils and some rocky cover (Conant and Collins, 1991). Family Colubridae Subfamily Colubrinae cf. goluher constrister Meterial.-10 vertebrae (UNSM 76418), 3 vertebrae (MSU VP 1374). Remarks.-The vertebrae of Cglaba; and naaglagpnla can be separated from other colubrids based on their more elongate shape and well developed epizygaphophyseal spines (Auffenberg, 1963), but to many authors, they are indistingishable from each other (for discussion see Holman, 1981). galaga; agnagzlggg; is currently found in Nuckolls County, while the closest any species of Maatlaanhla (naaglaaphla flagallam) is found, is about 150 km from the site (Lynch, 1985). Based on these ranges, the fossils are tentatively refered to C. QQDSLIiELQI- Diverse in habitat, 18 the various subspecies tend to occur in open areas (Conant and Collins, 1991). Elaphe guttata or B. obsolete Material.-10 vertebrae (UNSM 76419), 9 vertebrae (MSU VP.l375). Remarks.-Vertebrae from the genus Elapna have more vaulted neural arches, less developed hemal keels, and straighter subcentral ridges than those of Lamnzgpaltla (Brattstrom, 1955; Auffenberg, 1963; Holman, 1965b). 3. ODEQLEEQ and B. gattata have higher neural spines than E. yglplna (Holman, 1965b). Elapna QDSQIELQ inhabits forested regions of southeastern Nebraska and eastern Kansas, about 20 km east of the site (Collins, 1974; Lynch, 1985). Elapha gustata is at the northern most part of its range in southern Nebraska, including Nuckolls County (Lynch, 1985). Both prefer open woodlands (Collins, 1974). Elaphe xulnina (Figure 5) Material.-7 vertebrae (UNSM 76420), 8 vertebrae (MSU VP 1376). Remarks.-Characters used to identify 3. yalplna are discussed above. Elapna yalplna is found as far south as Lincoln, Nebraska which is about 85 km north of Nuckolls County (Lynch, 1985), but its prehistoric range was much greater (Holman, 1981). In Nebraksa, E. yalplna inhabits varied habitats, including prairies, stream valleys, woods, and dunes (Conant and Collins, 1991). 19 Alanna sp. indet. Material.-17 vertebrae (UNSM 76421), 17 vertebrae (MSU VP 1377). Remarks.-This material is too fragmentary to assign to the specific level. WW Material.-12 vertebrae (UNSM 76422), 18 vertebrae (MSU VP 1378). Remarks.-The vertebrae of Lamprgpaltla triangalnm can be separated from other species of the genus and Anlagna alagana by its shorter, laterally-directed accessory processes, depressed neural arches, and rounder prezygapophyseal faces (Holman, 1963; Hill, 1971). Moreover, the neural spine of L. triangulam is shorter than other Lamprgpalgla species and the subcentral ridges are straight (Brattstrom, 1955; Parmley, 1986). The wide range of L. tzlangalam in Nebraska and Kansas would suggest that it may occur in Nuckolls County (Collins, 1974: Lynch, 1985). (Lamprgpaltla triangulam requires rocky, open hillsides (Collins, 1974). Subfamily Natricinae Nerodia sineden Material.-102 vertebrae (UNSM 76423), 25 vertebrae (MSU VP 1379). Remarks.-Vertebrae of the species of Nazgala tend to be squarish in shape with long, wide, ventrally directed hypaphyses (Brattstrom, 1967; Parmley, 1988). Nazagla 20 alpadan is distinctive from other species in the genus due to its low neural arch (Holman, 1967). Nuckolls County is within the modern range of N. alpafign which occurs along streams, rivers, and marshes (Lynch, 1985). Regina grahami (Figure 4) Material.-15 vertebrae (UNSM 76424), 9 vertebrae (MSU VP 1380). Remarks.-The vertebrae of Baglna gzanaml are similar in shape to Nazggla, but are distinguished by the concave anterior border of the neural spine and short, trucated hypaphyses (Holman, 1972). This snake now occurs about 110 km east of Nuckolls County (Lynch, 1985). Baglna grananl frequents ponds, stream margins, and swamps (Conant and Collins, 1991). figazazla sp. indet. Material.-157 vertebrae (UNSM 76425), 6 vertebrae (MSU VP 1381). Remarks.-The vertebrae of both angrala fiakayl and a. ggalplggmaaalaga are identical in being small and elongate with very low neural spines which overhang the neural arch (Holman, 1962; Auffenberg, 1963; Holman and Grady, 1987). As both species occur within Nebraska today (Lynch, 1985), the fossils are refered to the genus only. figggazla agglplggmagalata is rare, and fi. dakayl is found only in the mesic woods in the southeastern corner of the state (Lynch, 1985). Figure 4 Figure 5 21 Trunk vertebra of Regina grahami (UNSM 76424) in lateral view. 1mm Trunk vertebra of Elaphe vulpina (UNSM 76420) in lateral View. 22 Thamnanhis Proximaa Msterial.-59 vertebrae (UNSM 76426), 10 vertebrae (MSU VP 1382). Remarks.-Vertebrae of the genus Thamnaphla are elongate with short hypaphyses which are directed posteriorally (Brattstrom, 1967; Parmley, 1988). Ibamngphla prgxlmna and I. alrralla have higher neural spines with less pronounced overhanging corners and are longer and more gracile than I. radix (Holman, 1962, 1984; Rogers, 1982). Large vertebrae of I. praxlmag have less well developed epizygapophyseal spines and straighter anterior borders of the neural spine than I. alrralla (Holman, 1987a). Smaller vertebrae of I. praxlmaa have accessory processes which are oblique to the axis of the centrum and oblong prezygapophyses (Holman, 1962; Rogers, 1984). Frequenting most aquatic habitats, T. prgxlmga is found in eastern Nebraska about 85 km from Nuckolls County (Lynch, 1985) Thamnaphia radix Material.-37 vertebrae (UNSM 76427), 12 vertebrae (MSU VP 1383). Remarks.-Based on the characters discussed above, these fossils are assigned to Thamngpnla radix. Thamngpnlajraglx occurs in Nuckolls County today and is found in wet grassland along marshes and ponds, avoiding rivers where I. alrralga is common (Collins, 1974; Lynch, 1985). 23 Thamnanhia airtalia Material.-42 vertebrae (UNSM 76428), 36 vertebrae (MSU VP 1384). Remarks.-Large fossils are assigned to I. alrralla based on characters discussed under I. prgxlnna. Smaller vertebrae of I. sirtalls have accessory processes which are nearly perpendicular to the long axis of the centrum and round prezygapophyses (Holman, 1962; Rogers, 1984). Ihamnapnla alrralla is common throughout Nebraska and is found in waters associated with streams (Lynch, 1985). Thamagpnla sp. indet. Material.-131 vertebrae (UNSM 76429), 77 vertebrae (MSU VP 1385) Remarks.-This material is too fragmentary to assign to the specific level. Subfamily Xenodontinae Heterodan Platirhinaa . Material.-3 vertebrae (UNSM 76430), 8 vertebrae (MSU VP 1386). Remarks.-Vertebrae of Hararaaan have depressed neural arches, extemely flattened or indistinct hemal keels, and are wider through the zygapophyses than long (Auffenberg, 1963; Parmley, 1986). Harargagn plarlrnlnga vertebrae are elongate compared to H. naalaaa and have longer prezygapophyseal faces with flattened anterior borders (Auffenberg, 1963; Holman, 1963). Range maps suggest that H. plarlrhlnaa should occur in Nuckolls County (Conant and 24 Collins, 1991). This species has varied habitats (open woodlands, river shores, or dunes) but requires dry, sandy conditions (Holman, 1971). Hataradan nasiaus Material.-4 vertebrae (UNSM 76431), 13 vertebrae (MSU VP 1387). Remarks.-Based on the characters discussed above the listed fossils are assigned to Harargdgn naalana. This species prefers dry, sandy prairie or grassland. Range maps suggest that n. naglgag should occur in Nuckolls County (Conant and Collins, 1991). Hararggga sp. indet. Material.-3 vertebrae (UNSM 76432). Remarks.—This material is too fragmentary to assign to the specific level. Family Viperidae Aqklgrrgggn sp indet. Material.-2 vertebrae (UNSM 76433), 1 vertebrae (MSU VP 1388). Remarks.-Vertebrae of Agklarrgggn have a single large foramen within deep pits on either side of the cotyle (Holman, 1963). This material is too fragmentary to identify to species. Askistradan ganrgrgrlx is found 85 km to the east of Nuckolls County (Conant and Collins, 1991). QIQEQLBE DQIIiQBE Material.-3 vertebrae (UNSM 76434), 3 vertebrae (MSU VP 1389). 25 Remarks.-grgralaa vertebrae have indistinct pits on either side of the cotyle which often contain multiple small foramina and have a depressed neural arch (Holman, 1963, 1982). Both 9. harrldna and C. ylrlnna have relatively low neural spines (Holman, 1967: LaDuke, 1991). grgralaa harrlgaa tends to have a neural spine longer than high whereas 9. yirldaa has a neural spine about as long as high (Holman and Winkler, 1987). grgralna harrlgna is now found 110 km from Nuckoll's County in eastern Nebraska (Lynch, 1985). Qrgtalua xiridia Material.-2 vertebrae (UNSM 76435). Remarks.-Based on the characters discussed above, these fossils are assigned to g. ylrlgla. This species occurs 110 km west of Nuckolls County and is found in areas with rocky outcrops or dissected pature land (Lynch, 1985). Qrgralag sp. indet. Material.-7 vertebrae (UNSM 76436), 7 vertebrae (MSU VP 1390). Remarks.-This material is too fragmentary to assign to the specific level. .Siatraraa aatanataa Material.-2 vertebrae (UNSM 76437), 3 vertebrae (MSU VP 1391). Remarks.-These fossils are similar in size to vertebrae of modern alsrruras garanarag and have a similarly vaulted neural arch (Holman, 1982). This snake prefers wet 26 grassland, bogs, and swamps early in the year and later move to drier woodland in the summer. Once common in eastern Nebraska, 5. garanaraa agricultural development has apperantly resulted in a restriction of it range to isolated occurences in eastern Nebraska (Lynch, 1985). DISCUSSION The herpetofauna of the Albert Ahrens local fauna is the most diverse Irvingtonian herpetofauna known from the Great Plains. It contains at least thirty-one species, including two salamanders, ten anurans, two turtles, one lizard, and sixteen snakes. None of these species is extinct. Only four other herpetofaunas with greater than twenty species have been described from the Irvingtonian. Three of these are from cave deposits in the eastern United States, and the fourth is from a Texas cave deposit (Fyllan Cave: Holman and Winkler, 1987). The eastern cave faunas are all similar to the modern local herpetofauna (Holman and Grady, 1989). Each has between four and five extralimital species (see Table 1), but many of the extralimital species occur relatively near the site. Their absence in the area today may reflect pressures in the recent environment or the difficulty of taking census of modern amphibian and reptile populations (Holman and Grady, 1989). Cryprgpraagnaa gnllfiayl, an extinct species from Cumberland Cave described by Holman (1977), may represent the living Hellbender, g. alleganianais (Holman. 1991) - 27 28 Table 1 Herpetofauna from caves in the eastern United States. Extralimital forms are marked by an x. Possible extinct froms are marked with a ?. Hamilton Cave Trout Cave New Trout Cave West. Virginia Maryland West Virginia Species (Holman and Grady, 1989) (Bel-an, 1982) (Holman and Grady. 19‘7) 79mm: 19mm ‘ X ' W sp. indet. . X - X mm W complex * - * mus-29; male}! * ' * mm spasm X * * mam marina X X ' hamster.- fame. * ' * mm W * - * W vlrldescens * - - 211219.422 W ' * - W Winona _ * - - 791mm sp. (neotenic form) mm mm 9319 Ml 12212;; m sp. indet. - - * Ills 212119912: or B- Muslin his main: m 9.4m in mm m 111mm Bans Planes-coupler 31911213421 W11 M9292». mam Ems mm m 1:312:21 92m mm m malaise m sp. indet. mm: mm mm mm Wis mum [nails mm m sp. indet. W wall: Inmates mm W sp. indet. mm mm; mm mum mm mm: - fl-fl-N 3‘. I ux-ai-ai-x-x-ab-x-xx-x-ux-a-x-ai-x-u- ai-un x-ai-uxx-nx-x-ux-x-un ae-aiu-x-a-xsa-vai-xs- . x- :- Nit-3636' at-atat-X' 29 In contrast, the mammalian fauna of the Pleistocene was less stable than the herpetofauna both in terms of extinction and in range adjustment (Holman, 1991). Due to the differences between climates indicated by reptilian faunas and models of Pleistocene climates based on boreal mammals, Hibbard (1960) proposed what later became known as the ”Pleistocene Climatic Equability Model.” Under this model, disharmonious biotas are thought to represent climates with reduced seasonal variability that allowed individual species to adjust according to their own individual climatic tolerances (Lundelius et al., 1983; Graham and Mead, 1987). Paleoclimatic interpretations.-Based partially on the limited adjustments of some amphibian and reptile species, Holman (1980) found that the Irvingtonian herpetofauna would suggest warmer winters. Minimum mean summer temperatures above those in boreal environments would also be necessary for turtle eggs to successfully develop (Stuart, 1979; Holman, 1987b). Fay (1988:190), however, questioned the use of eastern herpetofaunas to reconstruct climates. He suggested the stability of amphibians and reptiles through the Pleistocene implied either that a proper model had yet to be developed to account for the response of individual herpetological species to climatic change or that the herpetofauna was insensitive to change within the macroclimate. 30 One explanation for this apparent stability is the lack of a distinctive, identifiable boreal herpetofauna in the eastern United States (Pay, 1988). In other words, northern amphibians and reptiles that would have been displaced into the southern portion of their ranges would be indistinguishable from southern species-complexes (la. Rana aaparanrrlgnalla). A strictly boreal mammalian fauna, however, is distinguishable from a modern temperate fauna, as a number of mammal species are restricted to boreal habitats. The Albert Ahrens herpetofauna provides an opportunity to examine the adjustment of amphibians and reptiles to early Pleistocene glaciations. Much of the modern herpetofauna of the Great Plains occurs in grasslands, thus amphibians and reptiles from intruding boreal woodland would be easily recognizable in a Great Plains locality. In particular, the three modern species that occur a great distance north of the Great Plains (Ambyarama lararala, BRIO hamlgphrya, and Rana aylyarlaa) are of considerable interpretive importance. These factors allow Great Plains amphibians and reptiles to better reflect Pleistocene climatic changes than those in the east where woodlands dominate. In a preliminary report on the mammalian fauna (Voorhies and Corner, 1991), small mammals showed a strong boreal trend. Initial pollen analysis, which mainly indicated boreal conifers, substantiated this assessment 31 (Bolick, 1991). This initial data suggested to Voorhies and Corner (1991) that the fauna may represent the last of the Kansan glaciations in southern Nebraska. Voorhies (pers. comm.) felt that the deposit might have been concurrent with the maximum glacial advance into the Great Plains, as the mammals indicated a climate similar to the area around The Lake of the Woods in Ontario and Minnesota. In the herpetofauna, at least eleven species are extralimital in the Albert Ahrens local fauna (based on range maps in Conant and Collins, 1991). filarryrna garanaraa appears to be locally extirpated due to human activity and is therefore excluded as extralimital. These species are broken down into geographic groups in Table 2. While no single area of sympatry for the complete Albert Ahrens herpetofauna exists, twenty-six species (all species now found in Nuckolls County and seven extralimital species) can be found 220 km to the east in the northeastern corner of Missouri near the Nebraska border (Figure 6). Several species outside of this area of sympatry are within 200 km of Nuckolls County. Ambyargma lararala and Rana aylyarlga, however, have suffered a much more dramatic range adjustment of at least 600 km. The occurrences of B. aylyarlaa and Elapha ynlplna in Illinoian deposits in Kansas suggested to Holman (1984, 1987a) a cooler, wetter climate than Recent. While a full boreal climate is not indicated by the Albert Ahrens herpetofauna, the presence of the boreal A. laterale as well as B- exlxatiea and E. 1mm 32 Table 2 Geographic breakdown of extralimital amphibian and reptile species in the Albert Ahrens local fauna. Species extralimital to the area of sympatry in Figure 6 are marked by an asterisk (*). *Ambxetemalaterale *Banaexlxatiea Blathenlnina Eaters Intern *Qrotalaexiridaa Bareamerieanua mummfllehxsamlia Figure 6 Area of sympatry for the Albert Ahrens herpetofauna. The black dot is the location of the Albert Ahrens fauna. The oval, black mark indicates the area of sympatry. 34 would suggest at least a cooler summer climate during the time of deposition of the fossils. The absence of turtles other than ghyryaamya plgra and ghalygra garganrlna may also indicate cooler summer temperatures (Holman and Richards, 1993). These "boreal" species contrast with the presence of Paaagagrla glarkl, a southern extralimital species. An equable climate may have been capable of supporting temperate species (such as Panagagrla glarkl) and boreal species (such as Ambyargma lararala and Rana aylyarlga) in what would have been a mosaic community (Holman, 1976). Other Irvingtonian herpetofaunas from the Great Plains have produced species which would be ecologically incompatible today. In particular, £319 namlgphyra has been found in three faunas, the Cudahy, Courtland Canal, and Hall Ash (Tihen, 1962: Rogers, 1982). Of these, only Courtland Canal has greater than ten species with a total of twelve. This fauna also has the species Paaagamya agrlpra and Agklarrggan agargrrrlx which caused Rogers (1982) to suggest that the Courtland Canal climate was more equitable. This and the occurrence of BRIO hamlgphrya in the other faunas agree with the reconstruction proposed for the Albert Ahrens herpetofauna. Ranid Taphonomy.-Gravel appearing to be continuous with the stream deposits was found in a deep depression along one channel. This gravel pocket contained mostly disarticulated anuran fossils including cranial elements. Anuran cranial elements are not typically found as fossils (Holman, 1965a). 35 Ilia from this pocket belonged almost entirely to Rana alplana-complex (referred to BL 213111: see remarks on page 12). This depression is thought here to represent a quiet area along the bank of the stream where these frogs may have been living. Freezing of the latter pond may have caused mass death of frogs hibernating within the mud along the margins. This mechanism may have also caused the concentration discussed above and/or other concentrations (Holman, pers. comm.). The presence of an as yet unidentified articulated anuran (UNSM uncatalogued) from the upper silt could also be interpreted in this manner. It should be noted that Fay (1984) attributed high numbers of the species BRIE anarlaanna in the St. Elzear l.f. to hibernaculum mortality. Depositional anironment.-Sedimentary evidence suggests that micro-vertebrates from the lower gray silt were deposited on point bars within a system of small, shallow streams. Fossils, along with gravel, would have accumulated during periods of rapid run off. The clay nodules appear to be soil which fell into the streams at out banks during these periods. Otherwise, the stream appears to have had a weak current. As dicussed above, ranids are by far the most common fossils in the entire Albert Ahrens herpetofauna and are found as scapulae, humeri, and sacra as well as ilia (see individual species accounts). Numerous indeterminate anuran elements are most likely ranid, as well. The amount and 36 variety of ranid fossils suggests that very little transport occurred prior to their deposition as Rana species shun rapid flowing water; the in situ or near in situ deposition of these fossils suggest a low energy environment. The upper portion of the gray silt appears to be paludal in origin. This deposit is thought to indicate the presence of‘a beaver dam which blocked the flow of the Albert Ahrens stream system (Voorhies, pers. comm.). It is undoubtedly aquatic as a humerus from gnalygra garganrina was recovered from the lower portions of the deposit. Other aquatic species are also suggestive of pond or marsh habitats. In particular, Thamngpnia radix may be associated with the marshland (see remarks on page 22). A breakdown of the habitat preferences of the entire Albert Ahrens herpetofauna is given in Table 3. The most common fossils in terms of minimum number of individuals appear to be those associated with woodland edge or open woodlands. Thirteen species belong to a group which Holman (1992) considered conifer woodland tolerant. Remaining woodland species belong to a group more adapted for mixed conifer-deciduous woodland. Almost all appear to be at least semi-aquatic. Grassland species are much less numerous. Fossils of grassland species that are not seasonally dependent on aquatic habitats tend to show more wear than those of aquatic, woodland species, most likely due to a greater amount of transport to the site. 37 Grassland woodland Woodland Forest preferences from Holman Number of salamander and snake vertebrae Abbreviations are as follows: (C)-conifer (B)-species or F(C) F(C) Minimum number of individuals 1(16) 1(45) 1(9) 6 15 31 36 1(13) 1(19) 1(15) 1(30) 1(127) 1(2‘) 1(163) 1(60) 1(49) 1(78) 1(15) 1(17) 1(3) 1(6) 1(2) Table 3 Habitat preferences and abundances of amphibian and reptile species in the Albert Ahrens local fauna. Infered habitats are from Collins (1974) and Lynch (1985). (1992). are in parathesis. S-seasonal, F-frequent, I-infrequent, tolerant, (D)-mixed forest, subspecies in both grous. Pond or Fund or Open Species stream stream edge unmannruuau. S S - F «manslaugh- adult S S F F larva F' - - - WM - S F - Marriages S S - F(C) auaaummu - F F I later-2229192111 S F F ' WM 5 S F F lflsmuflflaflflmd S F ' F flieuuuuua Mantegna: F F - - man-4m S F - - Bmuhhml S S I - Bluaflflfifla ' ' ' ' ghglzdra ISIRIBELBS F' S - - QEBQMLMflahflM; F S - - Immaadmflmms - - F - MW - - F F(D) magnesium - - F F l-flmfium mm - - I F(B) WW - - F F mm P F - - Marshal F F ' ' manna-n - - F nmmmmuJummMs - F - - nmmmmusmur ' F F ' mama: - F - F WW - I F F(D) Wanna: - ' F ' We. - F - - mm - - - F mums - - F - aummnu£MHMMn - - F ' 1(5) CONCLUSION The Albert Ahrens local fauna has produced a large herpetofauna of thirty—one species. Like many eastern cave faunas from the Irvingtonian, the majority of the Albert Ahrens herpetofauna is similar to the modern fauna: however two distinct northeastern species, Ambyargma lararala and Rana aylyariaa, as well as Elapha yulpina show that there was some amount of range adjustment to possible Irvingtonian glaciation. In contrast to Fay's (1988) comments based on eastern Rancholabren cave faunas, the Great Plains herpetofauna from the Irvingtonian appears consistent with the ”Pleistocene Climatic Equability Model.” The depositional environment appears to have been a slow stream system bordered by a mixed conifer-deciduous forest. Later blockage of the streams resulted in a pond which developed into a marsh. Some amount of grassland was present within the drainage basin. Grassland species appear to be a mix of amphibian species which would have made seasonal use of the stream system and of remains washed into the depositional site from varying distances. 38 LIST OF REFERENCES LIST OF REFERENCES Aber, J.S. 1991. The glaciation of northeastern Kansas. Boreas 20(4):297-314. Auffenberg, W. 1963. The fossil snakes of Florida. Tulane Studies in Zoology 10(3):131-216. Bolick, M.R. 1991. 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