From tree to shining sea: taphonomy of the arboreal lizard Geiseltaliellus maarius from Messel, Germany

Palaeobiodiversity and Palaeoenvironments - Tập 92 - Trang 45-65 - 2012
Krister T. Smith1, Michael Wuttke2
1Department of Paleoanthropology and Messel Research, Senckenberg Research Institute, Frankfurt am Main, Germany
2Referat Erdgeschichte, Generaldirektion Kulturelles Erbe Rheinland-Pfalz, Mainz, Germany

Tóm tắt

Much has been written about the palaeoenvironment of the middle Eocene fossil Lagerstätte of Messel, Germany, and of the taphonomy of the vertebrates found in it, but taphonomic phenomena among the reptiles in this locality are virtually unstudied. The iguanid Geiseltaliellus maarius is the most common lizard species in Messel. We present taphonomic data for this species and analyse it. Specimens of G. maarius can be divided into three preservation classes, one of which is distinguished purely by decompositional phenomena. Most specimens sank quickly to the bottom of Lake Messel after entering it, but one floated for some time prior to emplacement. In theory, overlying pressure should not preclude the accumulation of gases of decay in submerged carcasses. In one specimen, such gases appear to have built up intracoelomically for many weeks, but did not cause the carcass to rise because of overlying water pressure. Eruption of the gases through the oral and cloacal openings, possibly initiated by a coincident turbidity current, scattered the bones of the skull, the pelvic region, and the proximal part of the tail. G. maarius had evolved a form of intervertebral urotomy (pseudoautotomy), which is indicative of arboreal habits. The waxy substance adipocere, formed after breakdown of fat, has been neglected in discussions of taphonomy, but may constitute an important factor in stabilising carcasses and enabling three-dimensional preservation before diagensis.

Tài liệu tham khảo

Ackermann M, Habersetzer J, Schaarschmidt F (1988) From excavation to exhibition piece. In: Schaal S, Ziegler W (eds) Messel: An Insight into the History of Life and of the Earth. Clarendon Press, Oxford, pp 277–284 Allison PA (1988) Konservat-Lagerstätten: cause and classification. Paleobiology 14(4):331–344 Allison PA, Smith CR, Kukert H, Deming JW, Bennett BA (1991) Deep-water taphonomy of vertebrate carcasses: a whale skeleton in the bathyal Santa Catalina Basin. Paleobiology 17(1):78–89 Arnold EN (1984) Evolutionary aspects of tail shedding in lizards and their relatives. J Nat Hist 18(1):127–169 Arnold EN (1988) Caudal autotomy as a defense. In: Gans C, Huey RB (eds) Biology of the Reptilia, vol 16, Ecology B. Liss, New York, pp 235–273 Bartels C, Poschmann M, Schindler T, Wuttke M (2002) Palaeontology and palaeoecology of the Kaub Formation (Lower Emsian, Lower Devonian) at Bundenbach (Hunsrück, SW Germany). In: Bartels C, Wuttke M, Briggs DEG (eds) The Nahecaris Project: realising the marine life of the Devonian from the Hunsrück Slate of Bundenbach (Metalla vol. 9, nr. 2). Deutsches Bergbau-Museum, Bochum, pp 105–122 Bennett AF (1980) The thermal dependence of lizard behaviour. Anim Behav 28:752–762 Berg S, Doring G, Suchenwirth H, Weiner K-L (1969) Beobachtungen über das Verhalten von Fettwachsleichen in grösserer Wassertiefe. Arch Kriminol 143:148–162 Berner RA (1968) Calcium carbonate concretions formed by the decomposition of organic matter. Science 159:195–197 Böttcher R (1989) Über die Nahrung eines Leptopterygius (Ichthyosauria, Reptilia) aus dem süddeutschen Posidonienschiefer (Unterer Jura) mit Bemerkungen über den Magen der Ichthyosaurier. Stuttg Beitr Naturk Ser B 155:1–19 Brand LR, Hussey M, Taylor J (2003) Decay and disarticulation of small vertebrates in controlled experiments. J Taphon 1(2):69–95 Brett CE, Baird GC (1986) Comparative taphonomy: a key to palaeoenvironmental interpretation based on fossil preservation. Palaios 1(3):207–227 Buisonjé PH (1985) Climatological conditions during deposiiton of the Solnhofen limestones. In: Hecht MK, Ostrom JH, Viohl G, Wellnhofer P (eds) The Beginnings of Birds: Proceedings of the International Archaeopteryx Conference Eichstätt. Freunde des Jura-Museums, Eichstätt, Germany, pp 45–65 Coard R (1999) One bone, two bones, wet bones, dry bones: transport potentials under experimental conditions. J Arch Sci 26(11):1369–1375 Cott HB (1926) Observations on the life-habits of some Batrachians and Reptiles from the Lower Amazon: and a Note on some Mammals from Marajó Island. Proc Zool Soc Lond 1926:1159-1178, pls. I-VI Dathe H (1960) Schwanz-regeneration beim Brillenkaiman. Natur u Volk 90:289–292 Dubost G, Gasc J-P (1987) The process of total tail autotomy in the South American rodent, Proechimys. J Zool, Lond 212(3):563–572 Dunham AE, Miles DB, Reznick DN (1984) Life history patterns in squamate reptiles. In: Gans C, Huey RB (eds) Biology of the Reptilia, vol 16, Ecology B (Defense and Life History). Branta Books, Ann Arbor, pp 441–511 Elder RL, Smith GR (1984) Fish taphonomy and paleoecology. Geobios, Mém spéc 8:287–291 Etheridge R (1967) Lizard caudal vertebrae. Copeia 1967(4):699–721 Felder M, Harms F-J, Liebig V (2001) Lithologische Beschreibung der Forschungsbohrungen Groß-Zimmern, Prinz von Hessen und Offenthal sowie zweier Lagerstättenbohrungen bei Epperthshausen (Sprendlinger Horst, Eozän, Messel-Formation, Süd-Hessen). Geol Jb Hessen 128:29–82 Fiedler S, Buegger F, Klaubert B, Zipp K, Dohrmann R, Witteyer M, Zarei M, Graw M (2009) Adipocere withstands 1600 years of fluctuating groundwater levels in soil. J Arch Sci 36:1328–1333 Forbes SL, Stuart BH, Dent BB (2005) The effect of the burial environment on adipocere formation. Forensic Sci Int 154(1):24–34 Franzen JL (1977) Urpferdchen und Krokodile: Messel vor 50 Millionen Jahren (Kleine Senckenberg-Reihe Nr. 7). Waldemar Kramer, Frankfurt am Main Franzen JL (1978) Senckenberg-Grabungen in der Grube Messel bei Darmstadt. 1. Probleme, Methoden, Ergebnisse 1976-1977. Cour Forsch-Inst Senckenberg 27:1–135 Franzen JL (1985) Exceptional preservation of Eocene vertebrates in the lake deposit of Grube Messel (West Germany). Philos Trans R Soc Lond B 311:181–186 Franzen JL (2007) Eozäne Equoidea (Mammalia, Perissodactyla) aus der Grube Messel bei Darmstadt (Deutschland): Funde der Jahre 1969-2000. Schweiz Paläont Abh 127:1–245 Franzen JL, Köster A (1994) Die eozänen Tiere von Messel - ertrunken, erstickt oder vergiftet? Nat u Mus 124:91–97 Franzen JL, Weber J, Wuttke M (1982) Senckenberg-Grabungen in der Grube Messel bei Darmstadt - 3. Ergebnisse 1979-1981. Cour Forsch-Inst Senckenberg 54:1–118 Franzen JL, Gingerich PD, Habersetzer J, Hurum JH, Koenigswald Wv, Smith BH (2009) Complete primate skeleton from the middle Eocene of Messel in Germany: morphology and paleobiology. PLoS One 4(5):e5723–e5727 Frazzetta TH (1962) A functional consideration of cranial kinesis in lizards. J Morph 111:287–319 Frey E (1988) Anatomie des Körperstammes von Alligator mississippiensis Daudin. Stuttg Beitr Naturk Ser A 424:1–106 Fründ H-C, Schoenen D (2009) Quantification of adipocere degradation with and without access to oxygen and to the living soil. Forensic Sci Int 188(1–3):18–22 Gillis GB, Bonvini LA, Irschick DJ (2009) Losing stability: tail loss and jumping in the arboreal lizard Anolis carolinensis. J Exp Biol 212(5):604–609 Glasheen JW, McMahon TA (1996) Size-dependence of water-running ability in basilisk lizards (Basiliscus basiliscus). J Exp Biol 199:2611–2618 Goth K (1990) Der Messeler Ölschiefer - ein Algenlaminit. Cour Forsch-Inst Senckenberg 131:1–141 Grein M, Konrad W, Wilde V, Utescher T, Roth-Nebelsick A (2011a) Reconstruction of atmospheric CO2 during the early middle Eocene by application of a gas exchange model to fossil plants from the Messel Formation, Germany. Palaeogeogr Palaeoclimatol Palaeoecol 309:383–391 Grein M, Utescher T, Wilde V, Roth-Nebelsick A (2011b) Reconstruction of the middle Eocene climate of Messel using palaeobotanical data. N Jb Geol Paläont Abh 260(3):305–318 Habersetzer J, Richter G, Storch G (1988) Bats - already highly specialised insect predators. In: Schaal S, Ziegler W (eds) Messel: an insight into the history of life and of the earth. Clarendon Press, Oxford, pp 181–191 Haglund WD (1993) Disappearance of soft tissue and the disarticulation of human remains from aqueous environments. J Forensic Sci 38(4):806–815 Harms F-J (1999) Erläuterungen zur Grube Messel bei Darmstadt, Südhessen. Schriftenr d geol Ges 8 (A. Hoppe and F. F. Steininger, eds. Exkursionen zu Geotopen in Hessen und Rheinland-Pfalz sowei zu naturwissenschaftlichen Beobachtungspunkten Johann Wolfgang von Goethes in Böhmen; Kleine Senckenberg-Reihe Nr. 31):181-222 Joyce WG, Scheyer TM (2011) The taphonomic settings of the Eocene Messel Pit, Germany: insights from the turtle fauna. In: Lehmann T, Schaal SFK (eds) The World at the Time of Messel: Puzzles in Palaeobiology, Palaeoenvironment, and the History of Early Primates (Conference Volume, 22nd International Senckenberg Conference). Senckenberg Gesellschaft für Naturforschung, Frankfurt am Main, pp 87–88 Keller T (1976) Magen- und Darminhalte von Ichthyosauriern des süddeutschen Posidonienschiefers. N Jb Geol Paläont Mh 1976(3):266–283 Keller T (2009) Beiträge zur Kenntnis von Placosauriops abderhaldeni KUHN, 1940 (Anguidae, Glyptosaurinae MARSH, 1872) aus dem Mitteleozän der Grube Messel - Skelettanatomie, Taphonomie und Biomechanik. Kaupia 16:3–145 Keller T, Schaal S (1988) Lizards: reptiles en route to success. In: Schaal S, Ziegler W (eds) Messel: an insight into the history of life and of the earth. Clarendon Press, Oxford, pp 119–134 Kielan-Jaworowska Z, Hurum JH (2006) Limb posture in early mammals: sprawling or parasagittal. Acta Palaeont Pol 51(3):393–406 Lenz OK, Wilde V, Riegel W (2010) A 600 k.y. record of El Niño-Southern Oscillation (ENSO): evidence for persisting teleconnections during the middle Eocene greenhouse climate of Central Europe. Geology 38:627–630 Lenz OK, Wilde V, Riegel W (2011) Short-term fluctuations in vegetation and phytoplankton during the middle Eocene greenhouse climate: a 640-kyr record from the Messel oil shale (Germany). Int J Earth Sci 100(8):1851–1879 Lillywhite HB, Maderson PFA (1982) Skin structure and permeability. In: Gans C, Pough FH (eds) Biology of the Reptilia, vol 12, Physiology C. Academic Press, New York, pp 397–442 Littke R, Rullkötter J (1987) Mikroskopische und makroskopische Unterschiede zwischen Profilen unreifen und reifen Posidonienschiefers aus der Hilsmulde. Facies 17:171–180 Littke R, Rotzal H, Leythaeuser D, Baker DR (1991) Lower Toarcian Posidonia Shale in southern Germany (Schwäbische Alb). Erdöl Kohle 44:407–414 Losos JB (1990) The evolution of form and function: morphology and locomotor performance in West Indian Anolis lizards. Evolution 44(5):1189–1203 Mai HD (1995) Tertiäre Vegetationsgeschichte Europas: Methoden und Ergebnisse. Gustav Fischer, Jena Manhein MH, ListiGA LM (2006) The application of geographic information systems and spatial analysis to assess dumped and subsequently scattered human remains. J Forensic Sci 51:469–474 Mant AK, Furbank R (1957) Adipocere: a review. J Forensic Med 4:18–35 Marshall Faux C, Padian K (2007) The opisthotonic posture of vertebrate skeletons: postmortem contraction or death throes? Paleobiology 33(2):201–226 Martill DM (1993) Soupy substrates: a medium for the exceptional preservation of ichthyosaurs of the Posidonia Shale (Lower Jurassic) of Germany. Kaupia 2:77–97 Mellen PF, Lowry MA, Micozzi MS (1993) Experimental observations on adipocere formation. J Forensic Sci 38(1):91–93 Mertz DF, Renne PR (2005) A numerical age for the Messel fossil deposit (UNESCO World Heritage Site) derived from 40Ar/39Ar dating on a basaltic rock fragment. Cour Forsch-Inst Senckenberg 255:67–75 Minnich JE (1982) The use of water. In: Gans C, Pough FH (eds) Biology of the Reptilia, vol 12, Physiology C. Academic Press, New York, pp 325–395 Mohr E (1941) Schwanzverlust und Schwanzregeneration bei Nagetieren. Zool Anz 135:49–65 Moussalli A, Moritz C, Williams SE, Carnaval AC (2009) Variable responses of skinks to a common history of rainforest fluctuation: concordance btween phylogeography and palaeo-distribution models. Mol Ecol 18:483–499 Neubert E (1999) The Mollusca of the Eocene Lake of Messel. Cour Forsch-Inst Senckenberg 216:167–181 Peterson JA (1984) The locomotion of Chamaeleo (Reptilia: Sauria) with particular reference to the forelimb. J Zool 202(1):1–42 Pfeiffer S, Milne S, Stevenson RM (1998) The natural decomposition of adipocere. J Forensic Sci 43:368–370 Poe S (2004) Phylogeny of anoles. Herp Monogr 18:37–89 Rabenstein R, Usman R, Schaal S (2004) Suche nach rezenten Seen als Modelle für den eozänen Lebensraum von Messel. Cour Forsch-Inst Senckenberg 252:115–138 Rabl W, Ambach E, Tributsch W (1991) Leichenveränderungen nach 50 Jahren Wasserzeit (Erweiterter Suizid im Jahre 1939). Beitr Gerichtl Med 49:85–89 Reisdorf AG, Wuttke M (2012) Re-evaluating Moodie’s Opisthotonic-Posture Hypothesis in fossil vertebrates. Part I. Reptiles – The taphonomy of the bipedal dinosaurs Compsognathus longipes and Juravenator starki from the Solnhofen Archipelago (Jurassic, Germany). In: Wuttke M, Reisdorf A (eds) Taphonomic processes in terrestrial and marine environments. Palaeobio Palaeoenv 92(1). doi:10.1007/s12549-011-0068-y Richter A (1994) Lacertilia aus der Unteren Kreide von Uña und Galve (Spanien) und Anoual (Marokko). Berliner Geowiss Abh E 14:1–147 Richter G, Clausing A (2004) Süßwasser-Dinoflagellaten aus der Grube Messel. Nat u Mus 134(4):129–130 Richter G, Storch G (1980) Beiträge zur Ernährungsbiologie eozäner Fledermäuse aus der „Grube Messel“. Nat u Mus 110:353–367 Richter A, Wuttke M (2012) Analysing the taphonomy of Mesozoic lizard aggregates from Uña (Eastern Spain) by X-ray controlled decay experiments. In: Wuttke M, Reisdorf A (eds) Taphonomic processes in terrestrial and marine environments. Palaeobio Palaeoenv 92(1). doi:10.1007/s12549-011-0065-1 Rossmann T (2000) Osteologische Beschreibung von Geiseltaliellus longicaudus Kuhn, 1944 (Squamata: Iguanoidea) aus dem Mittleren Eozän der Fossillagerstätten Geiseltal und Grube Messel (Deutschland), mit einer Revision der Gattung Geiseltaliellus. Palaeontographica A 258:117–158 Ruttan RF, Marshall MJ (1917) The composition of adipocere. J Biol Chem 29(2):319–327 Sakata M, Miki A, Kazama H, Morita M, Yasoshima S (1980) Studies on the composition of gases in the post-mortem body: Animal experiments and two autopsy cases. Forensic Sci Int 15:19–29 Schaal S, Ziegler T (eds) (1988) Messel: an insight into the history of life and of the earth. Clarendon Press, Oxford Schaal S, Schmitz-Münker M, Wolf H-G (1987) Neue Korrelationsmöglichkeiten von Grabungsstellen in der eozänen Fossillagerstätte Grube Messel. Cour Forsch-Inst Senckenberg 91:203–211 Schäfer W (1972 [1962]) Ecology and Paleoecology of Marine Environments. University of Chicago Press, Chicago Schoener A, Schoener TW (1984) Experiments on dispersal: short-term floatation of insular anoles, with a review of similar abilities in other terrestrial animals. Oecologia 63:289–294 Schulz R, Harms F-J, Felder M (2002) Die Forschungsbohrung Messel 2001: Ein Beitrag zur Entschlüsselung der Genese einer Ölschieferlagerstätte. Zs angew Geol 4:9–17 Schwermann AH, Wuttke M, Schulz J (2012) Virtopsy of the controlled decomposition of a dormouse Eliomys quercinus as a tool to analyse the taphonomy of Heterohyus nanus from Messel (Eocene, Germany). In: Wuttke M, Reisdorf A (eds) Taphonomic processes in terrestrial and marine environments. Palaeobio Palaeoenv 92(1). doi:10.1007/s12549-011-0063-3 Seilacher A (1970) Begriff und Bedeutung der Fossil-Lagerstätten. N Jb Geol Paläont Mh 1970:34–39 Seilacher A, Reif WE, Westphal F (1985) Sedimentological, ecological and temporal patterns of fossil Lagerstätten. Philos Trans R Soc Lond B 311(1148):5 Shargal E, Rath-Wolfson L, Kronfeld N, Dayan T (1999) Ecological and histological aspects of tail loss in spiny mice (Rodentia: Muridae, Acomys) with a review of its occurrence in rodents. J Zool, Lond 249:187–193 Slowinski JB, Savage JM (1995) Urotomy in Scaphiodontophis: evidence for the multiple tail break hypothesis in snakes. Herpetology 51(3):338–341 Smith KT (2009a) Eocene lizards of the clade Geiseltaliellus from Messel and Geiseltal, Germany, and the early radiation of Iguanidae (Squamata: Iguania). Bull Peabody Mus Nat Hist 50(2):219–306 Smith KT (2009b) A new lizard assemblage from the earliest Eocene (zone Wa0) of the Bighorn Basin, Wyoming, USA: Biogeography during the warmest interval of the Cenozoic. J Syst Palaeont 7(3):299–358 Smith GR, Elder RL (1985) Environmental interpretation of burial and preservation of Clarkia fishes. In: Smiley CJ (ed) Late Cenozoic History of the Pacific Northwest: Interdisciplinary Studies on the Clarkia Fossil Beds of Northern Idaho. Pacific Division of the American Association for the Advancement of Science, San Francisco, pp 85–94 Snyder RC (1949) Bipedal locomotion of the lizard Basiliscus basiliscus. Copeia 1949(2):129–137 Snyder RC (1952) Quadrupedal and bipedal locomotion of lizards. Copeia 1952(2):64–70 Spellerberg IF, Hoffmann K (1972) Circadian rhythm in lizard critical minimum temperature. Naturwiss 59(11):517–518 Stewart TD (1979) Essentials of Forensic Anthropology. Especially as Developed in the United States. Charles C, Thomas, Springfield, Illinois Sullivan RM, Keller T, Habersetzer J (1999) Middle Eocene (Geiseltalian) anguid lizards from Geiseltal and Messel, Germany. I. Ophisauriscus quadrupes Kuhn 1940. Cour Forsch-Inst Senckenberg 216:97–129 Sumner FB, Collins HH (1918) Autotomy of the tail in rodents. Biol Bull 34(1):1–6 Takatori T (2001) The mechanism of human adipocere formation. Legal Med 3(4):193–204 Tinkle DW (1967) The life and demography of the Side-Blotched Lizard, Uta stansburiana. Misc Publ, Mus Zool, Univ Mich 132:1–182 Todd J, Wassersug R (2010) Caudal pseudoautotomy in the Eastern Ribbon Snake Thamnophis sauritus. Amphib-Rept 31:213–215 Tomita K (1975) On putrefactions and refloatations of dead bodies under water. Hiroshima J Med Sci 24:117–152 Tomita K (1976) On putrefactions and refloatations of dead bodies under water (Supplement). Hiroshima J Med Sci 25(4):155–174 Tütken T (2011) Exceptional geochemical preservation of vertebrate remains from the Eocene Messel Pit, Germany – Paleoenvironmental and paleoecological implications of the stable isotope signatures. In: Lehmann T, Schaal SFK (eds) The World at the Time of Messel: Puzzles in Palaeobiology, Palaeoenvironment, and the History of Early Primates (Conference Volume, 22nd International Senckenberg Conference). Senckenberg Gesellschaft für Naturforschung, Frankfurt am Main, pp 164–165 Ubelaker DH, Zarenko KM (2011) Adipocere: what is known after over two centuries of research. Forensic Sci Int 208(1–3):167–172 Vague J, Fenasse R (1965) Comparative anatomy of adipose tissue. In: Renold AE, Cahill GF Jr (eds) Handbook of Physiology, Section 5: Adipose Tissue. American Physiological Society, Washington, pp 25–36 van Devender RW (1982) Comparative demography of the lizard Basiliscus basiliscus. Herpetologica 38(1):189–208 Vass AA (2001) Beyond the grave - understanding human decomposition. Microbiol Today 28:190–192 von Koenigswald W, Schierning H-P (1987) The ecological niche of an extinct group of mammals, the early Tertiary apatemyids. Nature 326:595–597 von Koenigswald W, Braun A, Pfeiffer T (2004) Cyanobacteria and seasonal death: a new taphonomic model for the Eocene Messel lake. Paläont Zs 78(2):417–424 Wagner M (2009) Die "manuelle Therapie" der Hand. Praxis Ergother 22(1):4–10 Wake DB, Dresner IG (1967) Functional morphology and evolution of tail autotomy in salamanders. J Morph 122(4):265–305 Wasmund E (1935) Die Bildung von anabituminösem Leichenwachs unter Wasser 10:1–70 Weber J (1991) Untersuchungen zur Tonmineralführung der Messel-Formation in der Fundstätte Messel (Mittel-Eozän). Cour Forsch-Inst Senckenberg 139:71–82 Weber S (2004) Ornatocephalus metzleri gen. et spec. nov. (Lacertilia, Scincoidea) – taxonomy and paleobiology of a basal scincoid lizard from the Messel Formation (middle Eocene: basal Lutetian, Geiseltalium), Germany. Abh Senckenberg Naturforsch Ges 561:1–159 Weber J, Hofmann U (1982) Kernbohrungen in der eozänen Fossilienlagerstätte Grube Messel. Geol Abh Hessen 83:1–58 Weigelt J (1989 [1927]) Recent Vertebrate Carcasses and their Paleobiological Implications [trans. J. Schaefer]. University of Chicago Press, Chicago Weitzel K (1949) Neue Wirbeltiere (Rodentia, Insectivora, Testudinata) aus dem Mitteleozän von Messel bei Darmstadt. Abh Senckenberg Naturforsch Ges 480:1–24 Werner YL (1968) Regeneration frequencies in geckoes of two ecological types (Reptilia: Gekkonidae). Vie Milieu 19:199–221 Wetherill CM (1860) On adipocere, and its formation. Trans Am Philos Soc (NS) 11:1–25 Wuttke M (1983a) Aktuopaläontologische Studien über den Zerfall von Wirbeltieren. Teil I: Anura. Senck leth 64(5/6):529–560 Wuttke M (1983b) Weichteilerhaltung durch lithifizierte Mikroorganismen bei mitteleozänen Vertebraten aus den Ölschiefern der Grube Messel bei Darmstadt. Senck leth 64(5/6):509–527 Yan F, McNally R, Kontanis EJ, Sadik OA (2001) Preliminary quantitative investigation of postmortem adipocere formation. J Forensic Sci 46(3):609–614 Zangerl R, Richardson ES Jr (1963) The paleoecological history of two Pennsylvanian black shales. Fieldiana Geol Mem 4:365–438 Zani PA (1996) Patterns of caudal-autotomy evolution in lizards. J Zool 240:201–220