Where do turtles hail from? Why and how did they acquire shells? These questions have spurred heated debate and intense research for more than two hundred years. Brilliantly weaving evidence from the latest paleontological discoveries with an accessible, incisive look at different theories of biological evolution and their proponents, Turtles as Hopeful Monsters tells the fascinating evolutionary story of the shelled reptiles. Paleontologist Olivier Rieppel traces the evolution of turtles from over 220 million years ago, examining closely the relationship of turtles to other reptiles and charting the development of the shell. Turtle issues fuel a debate between proponents of gradual evolutionary change and authors favoring change through bursts and leaps of macromutation. The first book-length popular history of its type, this indispensable resource is an engaging read for all those fascinated by this ubiquitous and uniquely shaped reptile.
About the Author
Olivier Rieppel is Rowe Family Curator of Evolutionary Biology at the Field Museum in Chicago. He is on the editorial board of several peer-reviewed scientific journals, and has himself published more than 350 scientific papers and eight books.
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Turtles As Hopeful Monsters
Origins and Evolutions
By Olivier Rieppel
Indiana University PressCopyright © 2017 Olivier Rieppel
All rights reserved.
OFF WE WERE ON A PLANE TO LONDON, OUR SPIRITS RISING HIGH in anticipation. It must have been the fall of 1972. I was an undergraduate student in zoology at the University of Basel in Switzerland, my companion a graduate student in zoology at the University of Zurich. We had both dedicated ourselves to the study of amphibians and reptiles, a branch of zoological science called herpetology. Othmar Stemmler, son of local celebrity Carl Stemmler, informally tutored us both (Honegger and Obst, 2014). Othmar's father was a keeper at the Basel Zoological Garden responsible for the great apes, who had acquired some prominence through his popular and engaging books and radio shows about zoo animals and African safaris. Othmar was an elementary school teacher, spending most of his free time working as a volunteer in the herpetological section at the Basel Natural History Museum. Herpetology had had a long and famous history at the museum, which had resulted in a large and historically significant collection of amphibians and reptiles, with numerous rare and important specimens from all over the world. However, herpetological research at the Basel museum, once of international reputation, tapered off and came to a halt toward the mid-twentieth century, the collections left orphaned. Heini Hediger, a renowned pioneer in the field of animal psychology and director of the Basel zoo from 1944 through 1953, was the last scientist of international reputation who, again as a volunteer, had worked in the herpetological collections of the Basel museum before Othmar's time (Honegger, 2015).
Although he was self-trained, Othmar Stemmler was in the early 1970s one of only two or three experts in Switzerland who specialized in the study of species-level taxonomy of amphibians and reptiles. He took me under his tutelage at the Basel Natural History Museum while I was still a high school student in the late 1960s and introduced me to the art and science of species-level taxonomy. Ernst Mayr's (1904–2005) then brand-new textbook, Principles of Systematic Zoology (1969), was never far from reach. Mayr, originally of German extraction, was the undisputed preeminent evolutionary biologist of the day, professor at Harvard's Museum of Comparative Zoology, and author of the then-current standard text on evolutionary theory, his 1963 Animal Species and Evolution. Mayr's systematics was heavily based on his own field studies of population biology and patterns of speciation, i.e., modes of species origination in birds, especially those of New Guinea. After graduating from the University of Berlin, Mayr accepted appointment as a curator at the American Museum of Natural History (amnh) in New York in 1931 — an employment that offered a most welcome escape from the troubled economy and politics of the Weimar Republic. He vacated his New York position in 1953 when he moved to the Museum of Comparative Zoology. After the collapse of the Third Reich in his home country, Mayr was instrumental in organizing, with the help of the American Ornithologists' Union, the mailing of care packages to needy German ornithologists, drawing on his old contacts to make sure that no Nazi fellow travelers would profit from these efforts (Rieppel, 2013a).
At the Basel museum, with Mayr's book at hand, Othmar and I measured size, recorded colors, and counted scales until we had convinced ourselves that some local population of lizards or snakes in some corner of this world was sufficiently distinct from its neighbors so as to be recognized as a new species, or subspecies. Together with like-minded reptile aficionados, all of them older and more experienced than me, Othmar loved to put together collecting expeditions that ventured out to places around the Mediterranean, though with a preference for the Atlas Mountains in Morocco. Back at the museum, the collected animals had to be properly pickled, identified, tagged, and cataloged, tasks I went about in the customary white lab coat but without latex gloves (the carcinogenic properties of formalin had not yet been recognized). Some gecko lizards of the genus Tarentola brought back from localities ranging along the northern margins of the Sahara desert seemed to not quite fit any of the diagnoses of the species then known and formally recognized in the genus. But the number of specimens at our disposal was too small to build a solid taxonomic case for the description of a new species. So off we went to London, my fellow student from Zurich and I, where we had arranged for an appointment in the section of amphibians and reptiles at what was then called the British Museum of Natural History in South Kensington.
The friendly and helpful staff at the museum put all we needed at our disposal: specimens, work space, calipers, and microscopes. But we did not seize this great opportunity after all. Instead, we enjoyed Carnaby Street and King's Road, bookstores and record stores, curries and fish and chips for dinner, and of course Guinness at the pub. London was still affordable at the time. The new species, if it was one, remained undescribed. Perhaps scale counting and calculating limb proportions was not my thing after all. Indeed, as unlikely as this may sound, while sitting in the plane to London, I was studying a classic textbook on the anatomy and embryonic development of vertebrates — that is, animals with a backbone — published by Goodrich in 1930. Edwin S. Goodrich (1868-1946) was an eminent zoologist at Oxford University, specializing in comparative anatomy, embryology, paleontology (the study of fossils), and phylogeny, i.e., the reconstruction of evolutionary relationships based on the insights generated by the aforementioned disciplines. Pages sporting complex drawings of snake skulls with their many teeth and fangs were followed by no less hard-to-understand illustrations of toothless turtle skulls: the massive skull of a sea turtle, the more delicately built skull of a soft-shelled turtle, and the skull of the oldest fossil turtle then known, from the Late Triassic of Germany, adorned with bumps and encrustations some 220 million years old. The text around those illustrations rambled on about the "temporal roofing" that in snakes had "almost entirely disappeared," quite in contrast to turtles, where, at least in the pictured sea turtle and in the fossil one, the cheek region of the skull located behind the eye socket was entirely closed. But this, Goodrich claimed, was not the primitive, ancestral condition for turtles; it was instead "a secondary covering of the temporal region by dermal scutes" (Goodrich, 1930:354). What was I to make of that? With such verbiage still difficult for me to grasp, Goodrich's account and illustrations of embryonic reptile skulls, of blood vessels and nerves snaking their way through a cartilaginous labyrinth, and the significance of all this for the understanding of reptile evolution completely evaded me. I marveled at the illustrations, underlined text I thought I could make sense of, and asked myself if Goodrich's rich, strange, and fascinating world would ever become fully intelligible to me. The intellectual challenge certainly seemed bigger and more attractive than that of counting scales and measuring limbs.
My search for Goodrich's 1930 textbook, Studies on the Structure and Development of Vertebrates, which I found in a famous secondhand bookstore located at the south head of the Mittlere Brücke in Basel, had been motivated by Georg Haas (1905–1981), the Herr Professor, as everybody called him, at the University of Basel (and later the University of Zurich) (Werner, 1965, 1982; Gans, 1983; Adler, 1989:101). He frequented that store whenever he was in town, as did every foreign visitor to the Zoological Institute, the latter located just a few steps from the store up a steep and narrow alley into the historic center of the town clustered around the Basel Minster. Haas, who was born into a Jewish family in Vienna on January 19, 1905, obtained the foundation for a classical, broad-based education at the Humanistisches Gymnasium (classical grammar school) before enrolling at the University of Vienna to study zoology and paleontology under herpetologists Franz Werner (1867–1939) and Otto von Wettstein (1892–1967), and Dutch functional anatomist Jan Versluys (1873–1939), the latter as of 1925 director of the Second Zoological Institute (Salvini-Plawen and Mizzaro, 1999:30). Versulys — a protégé of the politically compromised paleobiologist Othenio Abel (Ehrenberg, 1975:101; Svojtka, 2011:63^6; Taschwer, 2012) — was the principal advisor for his PhD thesis, which he completed in 1928, and which dealt with the functional anatomy of the head skeleton in primitive and poisonous snakes. Explaining the highly complex jaw mechanics of the burrowing blind snakes in the genus Typhlops in the courses he taught later, Haas would provoke incredulous stares from his students when he exclaimed, "Imagine myself being the skull of Typhlops, my arms its upper jaws," all the while moving about his angled arms in no clearly discernible pattern. Indeed, these snakes use their upper jaws in alternating movements that create a unique raking mechanism when feasting on termite and ant eggs and larvae, although they would not spurn adults as prey either.
The Herr Professor also reminisced about taking courses from eccentric paleontologist Franz Baron Nopcsa (1877–1933), of aristocratic Transylvanian extraction, who in the years immediately before the Great War lobbied for an independent kingdom of Albania. He thought that the Habsburg government of Austria-Hungary should install him as king of Albania, which would then allow him to instigate a guerrilla war against the Turks (Elsie, 1999; Weishampel and Kerscher, 2013:404). Haas pictured Nopcsa sitting at his desk, leafing through an enormous folio-sized sketch book featuring illustrations of all kinds of reptile skulls in an attempt to decipher possible evolutionary, i.e., phylogenetic, relationships among them. He also recounted an episode from a seminar on paleobiology offered by Othenio Abel, the founder of said discipline, which aims to reconstruct the biology of extinct plants and animals (Rieppel, 2013b). Could she deduce the direction from which the wind was blowing on the basis of ripple marks manifest on Paleozoic sedimentary rock from Morocco, Abel had asked a baffled student? Nopcsa, who sat in as well, quickly responded in the student's stead: "Could it be that the wind blew once from the West, once from the East, once from the North, and once from the South, just as it does today?"
In the years 1931–1932, Haas was a postdoctoral fellow at the Kaiser Wilhelm Institute for Biology in Berlin-Dahlem, where he studied the microscopic structure of unicellular organisms called protozoans under its director, zoologist and natural philosopher Max Hartmann (1876–1962). Dark, or rather brown, clouds were rising ever faster on the horizon, however. News reached him from Vienna of the growing antisemitism at the university, which increasingly turned violent (e.g., Pauley, 1992:192). Othenio Abel, president of the University of Vienna during the academic year 1932–1933, has been implicated in pulling strings behind the scene to stir up antisemitic sentiments and was accused of using his influence to prevent Jews from pursuing an academic career at the university (Taschwer, 2012). Later, effective with the beginning of the academic year 1934–1935, Abel would be sent into early retirement because of his political, indeed National Socialist, activities, which he pursued when he was president of the University of Vienna (Deichmann, 1996:71; see also Rieppel, 2013b). In anticipation of such developments, and advised by faculty from the University of Vienna, Haas decided in 1932 to heed the invitation to join the fledging Hebrew University of Jerusalem in the British Mandate of Palestine (Werner, 1982:491). The department of zoology was located in an old, picturesque building on the Russian Compound, with Mount Scopus in sight across the valley.
Haas was an expansive personality — a bachelor gourmet cook, lover of classical music, and avid reader of history. At least in his older age he had trouble enduring the summer heat in the Levant, and he looked for opportunities to teach as a guest lecturer at the University of Basel, where I first met him, and later at the University of Zurich, where I met him again. A course he offered on the origin of mammals set me on the track to study Goodrich's monograph. The platypus: here is a "duckbilled, beaver-tailed, otter-footed" mammal that lays eggs — Wikipedia facts well known to anybody only remotely interested in natural history (https://en.wikipedia.org/wiki/Platypus, accessed June 21, 2016). What I did not know, and what is also not recounted in Wikipedia, is the fact, pointed out in great detail by Herr Professor, that the pectoral girdle of the platypus more closely resembles that of a reptile than that of a mammal. Herr Professor got so excited in his account of such bony structures and their evolutionary significance that he almost crushed the precious mounted skeleton.
Herr Professor's scientific interests were wide ranging. A major part of his research was spent on the head anatomy of scaly reptiles (squamates), in particular the many forms of burrowing lizards and primitive snakes, hoping to discover an evolutionary link between those. But he was equally at home in systematic and biogeographic studies of the reptile fauna of the Levant, and Israel in particular. Biogeographers study the historical distribution of plant and animal species, as this provides one more key to an understanding of their evolutionary relationships. The Levant is of particular biogeographic interest, as it lies on the intersection between the Arabian Peninsula and Africa. And as if this were not enough, exposures of Triassic rocks at Makhtesh Ramon, a large ancient meteor crater in the Negev Desert, allowed Haas and his students to collect marine reptiles some 240 million years old, such as nothosaurs and placodonts (of which more later).
An unexpected but important door opened in the wake of the SixDay War of 1967. As the Suk in Eastern Jerusalem became accessible to Israelis, Haas rushed to get highly praised Arab tobacco for his pipe. Surprisingly, he found fossils for sale on the doorsteps of a tobacco store. As he inquired about their provenance, he found them to come from 'Ein Yabrud on the West Bank, approximately 20 kilometers north of Jerusalem, where limestone of mid-Cretaceous age was being quarried for building stone and facing. The delicate, fine-grained, and flat-cleaving limestone had to be quarried by hand, which is how the fossils were found in these marine deposits, roughly 95 million years old. Haas befriended the quarry owners, asking them to show him their fossil finds first. He purchased the scientifically important specimens for the National Natural History Collections kept at Hebrew University, and the remainder could go to the tobacco stores in the Suk. This is how Haas built an impressive collection of mid-Cretaceous (Cenomanian) marine reptiles for the Hebrew University — a collection that included lots of turtles, but most prominently simoliophid snakes with well-developed hind limbs, destined to become the objects of a heated debate about snake origins that erupted twenty years after Haas's death.
Over in London, with Goodrich in hand, I took time out from fooling around and set out to find the University College, and within it the department of zoology, where vertebrate paleontology was taught, a subject that had no representative at the University of Basel. Kenneth Kermack (1919-2000) was an expert in the study of the earliest mammals from the uppermost Triassic, fossil remains some 205 million years old, which he studied in collaboration with his wife, Doris, and his assistant, Frances Mussett. He taught a master's course in vertebrate paleontology and offered support for my application to the British Council for a scholarship that would allow me to study in London for one year. I passed my diploma examinations in the spring of 1974 and got ready to leave for London in the late summer with scholarship in hand. Haas again taught at Basel University that summer semester and was thrilled to send me off: "Go to the British Museum (Natural History)," he urged. "They have a fully disarticulated skull of an ichthyosaur [a dolphinlike marine reptile from the Jurassic, some 190 million years old] there, where all the bones have been separated from one another for closer inspection, a specimen well worth of analysis and description. And don't forget to have a good look at the skeletal collection of primitive snakes they have in the section of amphibians and reptiles!" Would I be allowed back, after the fiasco with the gecko lizards just a couple of years ago?
Excerpted from Turtles As Hopeful Monsters by Olivier Rieppel. Copyright © 2017 Olivier Rieppel. Excerpted by permission of Indiana University Press.
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Table of Contents
AcknowledgementsIntroduction1. Misplaced Turtles2. Reptile Classification and Evolution3. Levels of Evolution4. Hopeful Monsters5. The Turtle Shell6. Fossil Hunting in ChinaBibliographyIndex
What People are Saying About This
Here they are still with us, boxed up in a shell, seeming survivors of the distant geological past: prehistoric creatures, which both predated and outlived the dinosaurs. A symbol in Hindu and Chinese mythology, the turtle supports the earthbut what supports the turtle?
Turtles as Hopeful Monsters is a beautifully written and compelling book. Rieppel knows his subject inside out and has produced an authoritative work. But it is so much more than thatit belies a more far-reaching subject areathe practice of evolutionary biology itself. . . . The interplay of diverse disciplines including genetics, developmental biology, paleontology and, of course philosophy, are all set out alongside delightful personal insights. From Mendel to Hennig, Darwin to Mayr or Goodrich, Goldschmidt and Gould, Rieppel brilliantly analyses the practitioners and the giants of evolutionary theory.