The Great Fossil Enigma (4 page)

His father having died two years earlier, in 1844 Pander returned to the capital to pursue a career in the scientific section of the Russian Department of Mines. Now he began to prepare his great paleontological work – eventually published in four volumes –
Monograph of the Fossil Fishes of the Silurian System of the Russian Baltic Provinces.
Meticulous and pioneering in its use of the microscope to reveal the histology – the microscopic anatomy – of these fossils, the first volume, published in 1856, gained international attention. It did so because it revealed something that had remained unseen by the thousands of eyes that had looked intently at rocks over the previous half century. It was here that Pander first described those strange, tiny, tooth-like objects, the only evidence of “Lower Silurian” fishes. To come across such fossils, in rocks that had no right to possess them, was – to say the least – surprising. With intense curiosity and excitement, Pander peered down his microscope. But he did so for too long and contracted an eye infection that nearly blinded him. For almost two years he kept his microscope covered; the moment of revelation simply had to wait.

By the early 1850s, paleontology was a science vastly different from that Pander had known in the 1820s. It was now intellectually mature: rigorous in method and rich in theory. A vast network of European museums recorded the history of life in all its variety and with a great consistency of understanding. Naturalists had become connoisseurs of this variety, and so when sorting material under his microscope, Pander would have possessed a rich mental database of things previously seen that he could use to understand the new things he found. But this was no dry mechanistic exercise. It could so easily become a journey of exploration producing feelings of excitement and puzzlement, bizarre imaginings, and hopeful ambitions. As Stephen Jay Gould once noted, in typically picturesque fashion, “The legends of fieldwork locate all important sites deep in inaccessible jungles inhabited by fierce beasts and restless natives, and surrounded by miasmas of putrefaction and swarms of tsetse flies. (Alternative models include the hundredth dune after the death of all camels, or the thousandth crevasse following the demise of all sled dogs.) But in fact, many of the finest discoveries…are made in museum drawers.” Gould would undoubtedly have known, however, that the camel's death and thousandth crevasse had their equivalents for those who made their discoveries in museum drawers or looking down a microscope tube. Pander's exile from St. Petersburg, his eye disease, and his extraordinary difficulties finding an illustrator to draw his fish discoveries show that he too had moments when he felt the sled dogs had deserted him. He did, however, overcome these difficulties, and in Trutnev
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he found a gifted artist willing to painstakingly draw the microscopic details of his fish just as he wanted.

Panders' new fossils were quite remarkable: objects that were translucent, colorful, and beautiful, that were unexpected yet evocative.
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Naked and mute, these things needed to be clothed in the arcane and specific language of science so that others could appreciate the discovery and discuss it using the same terms. By these means, science as a whole could then seek the objects' meaning and truth. Here Pander had to make decisions about what descriptions to use to distinguish these fossils from others. He believed, from his connoisseurship of nature's objects, that he understood their language; making sense of them was thus a kind of mental conversation. The objects may have remained silent, but to him they seemed to speak. At the time, he was studying fossil fishes, and it was inevitable that he would look at these objects through eyes accustomed to looking at fish: They looked like fish teeth and he would see, name, investigate, conceive, and understand these objects as he would fish teeth.

He tested his ideas by looking at every facet of each object. If all the different aspects of a tooth said the same thing, he could be assured that his initial interpretation was probably correct. He soon found, however, that there was much to contradict the idea that these fossils were teeth. Chemical investigation suggested that they were made of lime (calcium carbonate) and not, like every other vertebrate tooth, apatite (calcium phosphate). A hollow internal “pulp cavity” seemed to support the tooth theory, but, unusually, it did not mirror the external form of the tooth. Indeed, unlike vertebrate teeth, which grow by the addition of layers to the surface, these microscopic teeth appeared to have grown by the addition of layers to the inside of the pulp cavity. Cone shaped in form, they grew cone
in
cone. Grinding the teeth down to make translucent slithers or thin sections that could be viewed under the microscope, he searched the fossils' interior structures for further clues. Color seemed to be important. In the “yellowish, transparent, flexible, hornlike teeth,” he found layers, or lamellae, which showed this cone-in-cone growth. The “snow white, opaque” teeth seemed to be immature forms of the yellow kind. He noted every recurring feature from small cells or bubbles arranged side-by-side, which lay between the lamellae, to large cavities randomly placed. Some pinkish teeth, made up of multiple “points” or cusps – “compound teeth” – showed a puzzling structure of “alternating light and dark cross-striped areas,” the dark stripes apparently formed of small cells. He thought these pink ones “different in every respect” from the yellow and white teeth.

Pander also detected what would become mysteriously known as “white matter” – parts of the conodont fossil lacking laminations that appear white in reflected light and an opaque black when light is transmitted through the fossil in thin section. White matter formed a distinctive feature of these new fossils.

These strange tooth-like objects were not like any known fish teeth, but Pander still considered them teeth: “Not only are we completely ignorant of the animals that possessed the lower Silurian teeth but also there are no descendants or living animals that have a similar type of tooth structure. We do not know what kind of teeth we are investigating, whether they belong to a jaw-bone, the palate or the tongue…or whether the various forms originated from the same animal.” He concluded that they could not have been attached to a jaw and fell upon the only possible modern analogy: “We can maintain, however, with reasonable certainty, that these teeth were inserted into the mucous membrane of the throat, similar to the teeth of the cyclostomes and the squalids.” Cyclostomes include the jawless hagfish and lamprey, while the squalids are a family of sharks that includes the humble dogfish.

As no one had ever seen teeth like these before, it was logical for Pander to imagine they came from a previously unseen type of fish. In his lifetime he had seen many inexplicably strange fossil fishes come to light, so why not stretch the boundaries a little further? Strange teeth demanded strange fish. Living cyclostomes were strange enough; they lacked jaws, true teeth, scales, bones, and a bony spine. Who could say how much stranger vertebrate life had been in the distant past? Pander's Conodonta, named after their cone-shaped teeth, were simply a new group of fishes no less exotic than others that appeared at this early stage of vertebrate life.

In everyday language, the name of these fishes became simplified to “conodonts,” but in the process the name lost the precision of its original meaning. Soon, if one found one of these fossil teeth, one found a “conodont”; the fossil became a conodont rather than the animal. In time scientists came to forget Pander's original usage, and so ingrained did this thinking become that much later still it became necessary to refer to the “conodont animal.” When this happened, some conodont workers complained that this was like talking of the “lion animal” or the “giraffe animal.” The word “conodont” is thus always a little ambiguous, and one has to ask, is this referring to a tooth-like fossil or to an animal? As much as possible I shall use the terms the scientists themselves used.

Having described the teeth in extraordinary detail, Pander then had to divide them into species so that each type could be given a scientific name. He admitted that he did not know whether the different types of teeth came from one mouth and thus were all the same species or whether each belonged to a different species of fish. This deficiency in his knowledge was not as important as it might at first appear, as paleontologists were used to naming parts of things knowing that they could correct any errors later on. This permitted Pander to opt for a pragmatic solution to the problem, and so he divided them into fifty-six species on the basis of their shape. He knew he was not creating true species but attempting to precisely define the different kinds of these objects. Armed with this knowledge and these names, others could also find conodont fossils and build upon what Pander had discovered.

What Pander had not foreseen was that by claiming his fossils to be the remains of the earliest vertebrates, he would unknowingly create an El Dorado myth. For like the lost city of gold, his fish relied on evocative yet contestable evidence. Just as many found in the lost city an irresistible draw, so science would not rest until it had finally resolved the truth of these anomalously old fishes. It was this controversial aspect that brought Pander's book international attention, and this in turn began to write the animal's mythology. Some would now go in search of the animal, while others would attempt to impose their more conservative views and deny Pander his fish. Indeed, the doubters began to take the high ground even before Pander's book hit the presses.

There has been much speculation about when Pander discovered his fossils. It may have been as early as 1848 or as late as 1850. News of the discovery first escaped Russia in January 1851, in a letter written to Murchison by Pander's friend and colleague, Gregor von Helmersen.
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That letter said little other than that Pander had found a new fauna in the older rocks. Murchison told his French disciple, Joachim Barrande, and he in turn wrote to Pander, who responded immediately, enclosing sketches of the rock succession and even examples of the fossils themselves. Pander's ideas about the conodont fishes were already well formed and it was with Barrande's reading of his letter to the Sociéte Géologique de France that Pander announced his discovery of “an immense quantity of teeth of fishes, the first traces of vertebrates” to the world. “These teeth, though similar in form to those of certain Placoids, Ganoides, and even fish now alive, are distinguished completely by their microscopic structure,” he told its members. “If one wanted absolutely to classify these fish among the forms nowadays, they would show analogy only with Cyclostomes.”
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Complimenting the Russian on the remarkably attentive and meticulous work that must have been required to find fossils no one else had seen, Barrande refrained from expressing his own opinion about them. Rather, he saw them as a welcome and timely arrival, for in Britain an argument had recently raged as to where in Murchison's Silurian rocks the oldest fish occur. That argument ended with the denial of fish as ancient as those Pander now believed he possessed. But if Barrande was only too willing to bow to Pander's superior knowledge of these fossils, he was somewhat disturbed by Pander's claim that this discovery provided evidence for Russian rocks older than the Silurian. Barrande thought Pander wanted to use his tiny fishes to insert a new geological system beneath the Silurian, and on this point he predictably objected.

Pander soon discovered that he had been a little naïve in permitting examples of his fossils to circulate in the jealous scientific communities of Paris and London before his detailed analysis was published. It left him exposed to a preemptive strike – one his friend, Murchison, was already primed to make. Murchison was then preparing his
Siluria: A History of the Oldest Known Rocks Containing Organic Remains
, a book he aspired to make definitive. Pander's teeth were something of a problem, and particularly so if they might be used to claim a fossil-bearing system older than the Silurian. Were this to succeed, Murchison's book and his Silurian would be seriously challenged. So he called upon the expertise of Barrande and William Carpenter, professor of physiology at the Royal Institution in London, and the superior technology of their “powerful microscopes,” in the hopes of causing a little tooth decay. He was in luck. With no evidence of bone, Pander's fish teeth, “not larger than pin heads,” could be dismissed as mere fragments of trilobites.
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