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Reconstructing the mass and thermal ecology of North American Pleistocene tortoises

  • Donald A. Esker (a1), Steve L. Forman (a1) and Dava K. Butler (a2)


Researchers often interpret the presence of tortoises in Pleistocene assemblages as evidence of an interglacial age, based on an assumption that these fossils indicate thermic climates, as modern giant tortoises require. Since the Paleocene, tortoises have been common components of terrestrial fossil assemblages and have repeatedly evolved species of giant size. Whereas extant giant tortoises are found only on islands off the coasts of South America and Africa, at least two species persisted in North America until the terminal Pleistocene. These tortoises, Hesperotestudo crassiscutata and Gopherushexagonatus,” both of which reached carapace lengths of >1 m, were distributed across the southern United States. This study provides new metrics to derive quantitative weight estimates from measurements of the tortoise shell. The linear measurements of 69 anatomical features of the shells of 108 live tortoises indicate that the regression between straight carapace length and weight is most significant, with a maximum r2 > 0.99. This regression is useful for tortoises that weigh between 1.8 and 339 kg. This mass estimate, coupled with a heat dissipation rate derived from thermoregulation modeling, provides estimates of how long tortoises can maintain a viable body temperature at low ambient temperatures. Depending on size, a tortoise can survive a maximum of 2.3 to 33 hours of freezing temperatures, which corresponds to a mean annual temperature ≥22°C and a mean winter low temperature ≥7.5°C. This analysis infers warmer temperatures at Pleistocene sites with fossil tortoise occurrences than previous qualitative estimates.



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Agusti, J., Oms, O., and Pares, J. M.. 1999. Calibration of the Early-Middle Pleistocene transition in the continental beds of the Guadix-Baza Basin (SE Spain). Quaternary Science Reviews 18:14091417.
Amani, F., and Geraads, D.. 1993. The Mousterian site of Jebel-Irhoud, Morocco—new data on the fauna and biochronology, and description of a new human fossil. Comptes Rendus de l'Académie des Sciences, Paris, série II 316:847852.
Angielczyk, K. D., Burroughs, R. W., and Feldman, C. R.. 2015. Do turtles follow the rules? Latitudinal gradients in species richness, body size, and geographic range area of the world's turtles. Journal of Experimental Zoology B Molecular and Developmental Evolution 324:270294.
Auffenberg, W. 1958. Fossil turtles of the genus Terrapene in Florida. Bulletin of the Florida State Museum, Biological Sciences 3.
Auffenberg, W. 1962. A new species of Geochelone from the Pleistocene of Texas. Copeia 1962:627636.
Bachmayer, F. 1975. Pleistozane Schildkroten aus Hohlen der Insel Kreta. Annales Geologiques des Pays Helleniques Athena 27:110122.
Bachmayer, F., and Symeonidis, N.. 1975. Schildkrötenreste (Testudo marginata Schoepff) aus der Höhle ‘Charkadio’ auf der Insel Tilos (Dodekanes, Griechenland). Annales Géologiques des Pays Helléniques 26:324327.
Bailey, S. J. 1992. Hibernacula use and home range of the desert tortoise (Gopherus agassizii) in the San Pedro Valley, Arizona. M.S. thesis University of Arizona, Tucson.
Barbato, L. C., and Gliozzi, E.. 1995. Biochronological and palaeogeographical implications of a well-balanced late Middle Pleistocene fauna from Quisisana-Certosa (Capri, Southern Italy). Bollettino-Societa Paleontologica Italiana 34:235261.
Behrensmeyer, A. K., and Turner, A.. 2017. Fossilworks: gateway to the Paleobiology Database., accessed 20 December 2017.
Bennett, S. C. 1996. Aerodynamics and thermoregulatory function of the dorsal sail of Edaphosaurus. Paleobiology 22:496506.
Bianucci, G., and Landini, W.. 2005. I paleositi a vertebrati fossili della Provincia di Pisa. Atti della Società Toscana di Scienze Naturali, Memorie, serie A 110:122.
Biewer, J., Sankey, J., Hutchison, H., and Garber, D.. 2016. A fossil giant tortoise from the Mehrten Formation of northern California. PaleoBios 33:113.
Blake, S., Yackulic, C. B., Cabrera, F., Tapia, W., Gibbs, J. P., Kümmeth, F., and Wikelski, M.. 2013. Vegetation dynamics drive segregation by body size in Galapagos tortoises migrating across altitudinal gradients. Journal of Animal Ecology 82:310321.
Bon, P., and Sala, B.. 1991. I giacimenti quaternari di vertebrati fossili nell Italia Nord Orientale. Memorie di scienze geologiche 43:185231.
Bonifay, E. 1991. Les premières industries du Sud-est de la France et du Massif Central. Actes du… Congrès National des Sociétés Savantes. Commission de Pré-et Protohistoire 114:6380.
Bonifay, M.-F. 1973. Principaux gisements paléontologiques français du Pléistocène moyen: essai de classification. Le Quaternaire 97:4149.
Bonifay, M. F., and Bonifay, E.. 1963. Paleontolofie-un gisement a faune epi-Villafranchienne a Saint-Esteve-Janson (Bouches-de-Rhone). Comptes Rendus Hebdomadaires des Séances de l'Académie des Sciences 256:1136.
Bramble, D. M., and Hutchison, J. H.. 2014. Morphology, taxonomy, and distribution of North American tortoises; an evolutionary perspective. Pp. 112 in McCoy, E. D. and Mushinsky, H. R., eds. Biology and conservation of North American tortoises. Johns Hopkins University Press, Baltimore, Md.
Brattstrom, B. 1954. Amphibians and reptiles from Gypsum Cave, Nevada. Bulletin of the Southern California Academy of Sciences 53:812.
Brattstrom, B. H. 1961. Some new fossil tortoises from western North America with remarks on the zoogeography and paleoecology of tortoises. Journal of Paleontology 35:543560.
Brinkman, D. B., Li, J. L., Ye, X. K., Wu, X. C., and Zhang, F. C.. 2008. Order Testudines. Pp. 35103 in The Chinese fossil reptiles and their kin. Science Press, Beijing, China.
Cantalamessa, G., Di Celma, C., Bianucci, G., Carnevale, G., Coltorti, M., Delfino, M., Ficcarelli, G., Espinosa, M. M., Naldini, D., and Pieruccini, P.. 2001. A new vertebrate fossiliferous site from the Late Quaternary at San José on the north coast of Ecuador: preliminary note. Journal of South American Earth Sciences 14:331334.
Cassini, G. H., Vizcaíno, S. F., and Bargo, M. S.. 2012. Body mass estimation in early Miocene native South American ungulates: a predictive equation based on 3D landmarks. Journal of Zoology 287:5364.
Chiari, Y., Hyseni, C., Fritts, T. H., Glaberman, S., Marquez, C., Gibbs, J. P., Claude, J., and Caccone, A.. 2009. Morphometrics parallel genetics in a newly discovered and endangered taxon of Galápagos tortoise. PLoS ONE 4:e6272.
Cisneros, J. C. 2005. New Pleistocene vertebrate fauna from El Salvador. Revista Brasileira de Paleontologia 8:239255.
Clarke, A., Angilletta, A. E. M., and Bronstein, E. J. L.. 2013. Dinosaur energetics: setting the bounds on feasible physiologies and ecologies. American Naturalist 182:283297.
Converse, H. H. 1973. A Pleistocene vertebrate fauna from Palm Beach County, Florida. The Plaster Jacket 21:112.
Cope, E. D., and Drinker, E.. 1895. The fossil vertebrata from the fissure at Port Kennedy, Pa. Proceedings of the Academy of Natural Sciences of Philadelphia 47:446450.
Crook, W. W., and Harris, R. K.. 1958. A Pleistocene campsite near Lewisville, Texas. American Antiquity 23:233246.
Crumly, C. R. 1984. The evolution of land tortoises (family Testudinidae). Ph.D. dissertation. Rutgers, Newark, N.J.
Curry, B. B., and Baker, R. G.. 2000. Palaeohydrology, vegetation, and climate since the late Illinois Episode (~130 ka) in south-central Illinois. Palaeogeography, Palaeoclimatology, Palaeoecology 155:5981.
Czaplewski, N. J., Farlow, J. O., and Argast, A.. 2013. A fossil shrew (Mammalia, Soricidae) from the Pipe Creek Sinkhole (Late Neogene: Hemphillian), Indiana. Proceedings of the Indiana Academy of Science 121:7986.
Dalquest, W. W. 1962. The Good Creek Formation, Pleistocene of Texas, and its fauna. Journal of Paleontology 36:568582.
de Broin, F. 1991. Fossil turtles from Bolivia. Fósiles y facies de Bolivia 12:509527.
Dundas, R. G. 2013. The mid-Irvingtonian Fairmead Landfill fossil site, Madera County Paleontology Collection, and Fossil Discovery Center of Madera County, California. In Putirka, K., ed. Geologic Excursions from Fresno, California, and the Central Valley: a tour of California's iconic geology. Geological Society of America Field Guide 32:63.
Dundas, R. G., Smith, R. B., and Verosub, K. L.. 1996. The Fairmead Landfill locality (Pleistocene, Irvingtonian), Madera County, California: preliminary report and significance. PaleoBios 17:5058.
Eberle, J., Fricke, H., and Humphrey, J.. 2009. Lower-latitude mammals as year-round residents in Eocene Arctic forests. Geology 37:499502.
Edmund, A. G. 1965. Late Pleistocene fauna from the Santa Elena Peninsula, Ecuador. Vol. 63. Governors of the University of Toronto, Toronto, Canada, p.
Emslie, S. D. 1995. Taphonomy of a late Pleistocene carnivore den, Dade County, Florida. Pp. 6583 in Late Quaternary environments and deep history: a tribute to Paul S. Martin. The Mammoth Site of Hot Springs, SD, Hot Springs, SD.
Fritz, U., Alcalde, L., Vargas-Ramírez, M., Goode, E. V., Fabius-Turoblin, D. U., and Praschag, P.. 2012. Northern genetic richness and southern purity, but just one species in the Chelonoidis chilensis complex. Zoologica Scripta 41:220232.
Fritz, U., and Bininda-Emonds, O. R. P.. 2007. When genes meet nomenclature: tortoise phylogeny and the shifting generic concepts of Testudo and Geochelone. Zoology 110:298307.
Gidley, J. W., and Gazin, C. L.. 1938. The Pleistocene vertebrate fauna from Cumberland Cave, Maryland. Journal of Mammalogy 14:343357.
Gut, H. J., and Ray, C. E.. 1963. The Pleistocene vertebrate fauna of Reddick, Florida. Quarterly Journal of the Florida Academy of Sciences 26:315328.
Harvati, K., Darlas, A., Bailey, S. E., Rein, T. R., El Zaatari, S., Fiorenza, L., Kullmer, O., and Psathi, E.. 2013. New Neanderthal remains from Mani peninsula, southern Greece: the Kalamakia middle Paleolithic cave site. Journal of Human Evolution 64:486499.
Hashemi, N., Ashouri, A., and Aliabadian, M.. 2015. Using of microvertebrate remains in reconstruction of late Quaternary (Holocene) paleoclimate, eastern Iran. Journal of Stratigraphy and Sedimentology Researches 31:8394.
Hay, O. P. 1917. Vertebrata mostly from stratum no. 3, at Vero, Florida: together with descriptions of new species. Florida Geological Survey, Annual Report. Florida Geological Survey, Tallahassee, Fla. Pp. 43–68.
Hay, O. P. 1926. A collection of Pleistocene vertebrates from southwestern Texas. Proceedings of the United States National Museum 68:118.
Head, J. J., Bloch, J. I., Hastings, A. K., Bourque, J. R., Cadena, E. A., Herrera, F. A., Polly, P. D., and Jaramillo, C. A.. 2009. Giant boid snake from the Palaeocene neotropics reveals hotter past equatorial temperatures. Nature 457:715717.
Hervet, S., and Salotti, M.. 2000. Les tortues pléistocènes de Castiglione (Oletta, Haute-Corse) et la preuve de leur indigénat en Corse. Comptes Rendus de l'Académie des Sciences, Paris, série IIA (Science de la Terre et des Planètes) 330:645651.
Hibbard, C. W. 1960. An interpretation of Pliocene and Pleistocene climates in North America. Annual Report of the Michigan Academy of Science, Arts and Letters 62:530.
Holman, J. A. 1958. The Pleistocene herpetofauna of Saber-tooth Cave, Citrus County, Florida. Copeia 1958:276280.
Holman, J. A. 1959a. Amphibians and reptiles from the Pleistocene (Illinoian) of Williston, Florida. Copeia 1959:96102.
Holman, J. A. 1959b. A Pleistocene herpetofauna near Orange Lake, Florida. Herpetologica 15:121125.
Holman, J. A. 1962. A Texas Pleistocene herpetofauna. Copeia 1962:255261.
Holman, J. A. 1980. Paleoclimatic implications of Pleistocene herpetofaunas of eastern and central North America. Transactions of the Nebraska Academy of Sciences and Affiliated Societies 8:131140.
Holman, J. A., and Winkler, A. J.. 1987. A mid-Pleistocene (Irvingtonian) herpetofauna from a cave in south central Texas. Pearce-Sellards series. Texas Memorial Museum, University of Texas at Austin, Austin, Tex. Pp. 1–17.
[IUCN] International Union for the Conservation of Nature. 2018. Gopherus search results. IUCN Redlist., accessed 14 February 2018.
Jackson, C. G., and Kaye, J. M.. 1975. Giant tortoises in the late Pleistocene of Mississippi. Herpetologica 31:421421.
Jackson, F. D., Varricchio, D. J., Jackson, R. A., Walde, A. D., and Bishop, G. A.. 2015. Taphonomy of extant desert tortoise (Gopherus agassizii) and loggerhead sea turtle (Caretta caretta) nesting sites: implications for interpreting the fossil record. Palaios 30:207223.
Kazmaier, R. T., Hellgren, E. C., and Synatzske, D. R.. 2001. Patterns of behavior in the Texas tortoise, Gopherus berlandieri: a multivariate ordination approach. Canadian Journal of Zoology 79:13631371.
Kraus, M. J., and Riggins, S.. 2007. Transient drying during the Paleocene–Eocene Thermal Maximum (PETM): analysis of paleosols in the Bighorn Basin, Wyoming. Palaeogeography, Palaeoclimatology, Palaeoecology 245:444461.
Lagarde, F., Bonnet, X., Nagy, K., Henen, B., Corbin, J., and Naulleau, G.. 2002. A short spring before a long jump: the ecological challenge to the steppe tortoise (Testudo horsfieldi). Canadian Journal of Zoology 80:493502.
Laloë, J.-O., Cozens, J., Renom, B., Taxonera, A., and Hays, G. C.. 2017. Climate change and temperature-linked hatchling mortality at a globally important sea turtle nesting site. Global Change Biology 23:49224931.
Le, M., Raxworthy, C. J., McCord, W. P., and Mertz, L.. 2006. A molecular phylogeny of tortoises (Testudines: Testudinidae) based on mitochondrial and nuclear genes. Molecular Phylogenetics and Evolution 40:517531.
Leidy, J. 1868. Notice of some vertebrate remains from the West Indian islands. Proceedings of the Academy of Natural Sciences of Philadelphia 20:178180.
Malatesta, A. 1980. Dwarf deer and other late Pleistocene fauna of the “Simonelli” Cave in Crete. Quaderno Accademia Nazionale dei Lincei, Roma 249:1128.
Mangili, G. 1980. Fossils reptiles of Simonelli cave. Quaderni della Accademia Nazionale dei Lincei 249:121122.
McRae, W. A., Landers, J. L., and Cleveland, G. D.. 1981. Sexual dimorphism in the gopher tortoise (Gopherus polyphemus). Herpetologica 37:4652.
Mecham, J. S. 1958. Some Pleistocene amphibians and reptiles from Friesenhahn cave, Texas. Southwestern Naturalist 3:1727.
Meers, M., and Hulbert, R. C.. 2002. A new middle Pleistocene local fauna from southwestern Florida. Journal of Vertebrate Paleontology 22:87A.
Meylan, P. A. 1995. Pleistocene amphibians and reptiles from the Leisey Shell Pit, Hillsborough County, Florida. Bulletin of the Florida Museum of Natural History 37:273297.
Moll, D., and Brown, L. E.. 2017. Reinterpretation of the climatic adaptation of giant fossil tortoises in North America. Herpetological Journal 27:276286.
Morales Pérez, J. V., and Serra, A. S.. 2009. The Quaternary fossil record of the genus Testudo in the Iberian Peninsula. Archaeological implications and diachronic distribution in the western Mediterranean. Journal of Archaeological Science 36:11521162.
Morgan, G. S., and Hulbert, R. C. Jr. 1995. Overview of the geology and vertebrate biochronology of the Leisey Shell Pit local fauna, Hillsborough County, Florida. Bulletin of the Florida Museum of Natural History 37:192.
National Centers for Environmental Information. 2018. Climate Data Online. National Oceanic and Atmospheric Administration.
National Climatic Data Center. 2010. 1981–2010 normals. Climate Data Online., accessed 21 March 2018.
National Weather Service. 2017. San Antonio climatology. U.S. Cities Climate Data. U.S. Department of Commerce, San Antonio, Tex.
Nordt, L., Bongino, J., Forman, S., Esker, D., and Benedict, A.. 2015. Late Quaternary environments of the Waco Mammoth Site, Texas USA. Quaternary Research 84:423438.
Nussear, K., Esque, T., Haines, D., and Tracy, R.. 2007. Desert tortoise hibernation: temperatures, timing, and environment. Copeia 2007:378386.
Oerter, E. J., Sharp, W. D., Oster, J. L., and Ebeling, A.. 2016. Pedothem carbonates reveal anomalous North American atmospheric circulation 70,000–55,000 years ago. Proceedings of the National Academy of Sciences USA 113:919.
Pajak, A. F., III, E. Scott, and Bell, C. J.. 1996. A review of the biostratigraphy of Pliocene and Pleistocene sediments in the Elsinore Fault Zone, Riverside County, California. The uses of vertebrate fossils in biostratigraphic correlation. PaleoBios 17:2849.
Parmley, D. 1986. Herpetofauna of the Rancholabrean Schulze Cave local fauna of Texas. Journal of Herpetology 20:110.
Parris, D. C., and Daeschler, E.. 1995. Pleistocene turtles of Port Kennedy Cave (late Irvingtonian), Montgomery County, Pennsylvania. Journal of Paleontology 69:563568.
Raynal, J.-P., Geraads, D., Magoga, L., El Hajraoui, A., Texier, J.-P., Lefevre, D., and Sbihi-Alaoui, F.-Z.. 1993. La grotte des Rhinocéros (Carrière Oulad Hamida 1, anciennement Thomas III, Casablanca), nouveau site acheuléen du Maroc atlantique. Comptes Rendus de l'Académie des Sciences, Paris, série II (Mécanique, Physique, Chimie, Sciences de la Terre et de l'Univers) 316:14771483.
Regis, K. W., and Meik, J. M.. 2017. Allometry of sexual size dimorphism in turtles: a comparison of mass and length data. PeerJ 5:e2914.
Reynoso, V.-H. and Montellano-Ballesteros, M.. 2004. A new giant turtle of the genus Gopherus (Chelonia: Testudinidae) from the Pleistocene of Tamaulipas, Mexico, and a review of the phylogeny and biogeography of gopher tortoises. Journal of Vertebrate Paleontology 24:822837.
Rhodes, E. J. 1994. Premières dates RPE pour l'Acheuléen du Maroc atlantique (Grotte des Rhinocéros, Casablanca). Comptes Rendus de l'Académie des Sciences, Paris, série II (Mécanique, Physique, Chimie, Sciences de la Terre et de l'Univers) 319:1109.
Rostal, D. C., McCoy, E. D., and Mushinsky, H. R.. 2014. Biology and conservation of North American tortoises. Johns Hopkins University Press, Baltimore, Md.
Roth, J. A., and Laerm, J.. 1980. A late Pleistocene vertebrate assemblage from Edisto Island, South Carolina. Brimleyana 3:129.
Sadeghayobi, E., Blake, S., Wikelski, M., Gibbs, J., Mackie, R., and Cabrera, F.. 2011. Digesta retention time in the Galápagos tortoise (Chelonoidis nigra). Comparative Biochemistry and Physiology A 160:493497.
Salotti, M., Baiion, S., Bonifay, M.-F., Courtois, J.-Y., Dubois, J.-N., Ferrandini, J., Ferrandini, M., La Milza, J.-C., Mourer-Chauviré, C., and Popelard, J.-B.. 1997. Castiglione 3, un nouveau remplissage fossilifère d’âge Pléistocène mojendans le karst de la région d'Oletta (Haute-Corse). Comptes Rendus de l'Académie des Sciences 1997:6774.
Sander, P. M., Christian, A., Clauss, M., Fechner, R., Gee, C. T., Griebeler, E.-M., Gunga, H.-C., Hummel, J., Mallison, H., Perry, S. F., Preuschoft, H., Rauhut, O. W. M., Remes, K., Tütken, T., Wings, O., and Witzel, U.. 2011. Biology of the sauropod dinosaurs: the evolution of gigantism. Biological Reviews 86:117155.
Schultz, G. E. 1969. Geology and paleontology of a late Pleistocene basin in southwest Kansas. Vol. 105. Geological Society of America, p.
Sellards, E. H. 1916. Human remains and associated fossils from the Pleistocene of Florida. Florida State Geological Survey, Tallahassee, Fla. Pp. 121206.
Sellards, E. H. 1917. Review of the evidence on which the human remains found at Vero, Florida, are referred to the Pleistocene. Florida State Geological Survey, Tallahassee, Fla. Pp. 6982.
Serefiddin, F., Schwarcz, H. P., Ford, D. C., and Baldwin, S.. 2004. Late Pleistocene paleoclimate in the Black Hills of South Dakota from isotope records in speleothems. Palaeogeography, Palaeoclimatology, Palaeoecology 203:117.
Servicios Climáticos Argentina. 2017. Climate Services., accessed 21 December 2017.
Seymour, R. S. 2013. Maximal aerobic and anaerobic power generation in large crocodiles versus mammals: implications for dinosaur gigantothermy. PLoS ONE 8:e69361.
Simpson, G. G. 1930. Additions to the Pleistocene of Florida. American Museum Novitates 406:114.
Spotila, J. R., Radzio, T., and O'Connor, M. P.. 2014. Thermoregulation and Energetics of North American Tortoises. P. 190 in Rostal, D. C., McCoy, E. D., and Mushinsky, H. R., eds. Biology and conservation of North American tortoises, Vol. 1. Johns Hopkins University Press, Baltimore, Md.
Steadman, D. W., Franz, R., Morgan, G. S., Albury, N. A., Kakuk, B., Broad, K., Franz, S. E., Tinker, K., Pateman, M. P., and Lott, T. A.. 2007. Exceptionally well preserved late Quaternary plant and vertebrate fossils from a blue hole on Abaco, The Bahamas. Proceedings of the National Academy of Sciences USA 104:1989719902.
Thomas, T. M., Granatosky, M. C., Bourque, J. R., Krysko, K. L., Moler, P. E., Gamble, T., Suarez, E., Leone, E., Enge, K. M., and Roman, J.. 2014. Taxonomic assessment of alligator snapping turtles (Chelydridae: Macrochelys), with the description of two new species from the southeastern United States. Zootaxa 3786:141165.
Tripsanas, E. K., Bryant, W. R., Slowey, N. C., and Bouma, A. H.. 2007. Sedimentological history of Bryant Canyon area, northwest Gulf of Mexico, during the last 135 kyr (Marine Isotope Stages 1–6): a proxy record of Mississippi River discharge. Palaeogeography, Palaeoclimatology, Palaeoecology 246:137161.
U.S. Department of Commerce, N. 2019a. DFW—freeze summary. Freeze summary for Dallas/Fort Worth., accessed 12 January 2019.
U.S. Department of Commerce 2019b. Waco—Freeze Summary. Freeze summary for Waco., accessed 12 January 2019.
Wagner, H. M., and Prothero, D. R.. 2001. Magnetic stratigraphy of the late Pliocene mammal-bearing deposits from Gypsum Ridge, San Bernardino County, California. Pacific Section SEPM Special Publication 91:369376.
Westgate, J. W. 1989. Mass occurrence of the giant gopher tortoise (Gopherus hexagonatus) in the late Pleistocene Beaumont Foundation, Willacy County, Texas. Journal of Vertebrate Paleontology 9:44a.
Wolfe, J. A. 1994. Tertiary climatic changes at middle latitudes of western North America. Palaeogeography, Palaeoclimatology, Palaeoecology 108:195205.

Reconstructing the mass and thermal ecology of North American Pleistocene tortoises

  • Donald A. Esker (a1), Steve L. Forman (a1) and Dava K. Butler (a2)


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