The Great Fossil Enigma (29 page)

Rhodes was given the role of diplomatic envoy and charged with drawing up and circulating the “Marburg Proposals,” which would, of course, reach those who were not there to witness this surprising outcome. Inevitably, there was little agreement among the forty-one responses he received, but Rhodes pressed on, editing these together into what became the third version and final agreement. The aim of the document, as he explained, was not to legislate for others but to provide “useful guidelines for those who choose to follow them.” It stressed the need for “great care, constraint and consultation.” It also required Rhodes to cook up a little linguistic spaghetti to cover all eventualities.
³⁵

Having taken this giant leap without the outbreak of civil war, it must have been with a sense of irony that conodont workers read of the intention of the International Commission on Zoological Nomenclature to introduce a scheme of parataxa at the end of that decade. The scheme was proposed by
ICZN
secretary Richard Melville in 1978 and sought to resolve the same difficulties that had troubled conodont workers in the 1950s.
³⁶
To prepare his case, Melville had reviewed those earlier arguments and alighted upon the conodonts as perhaps the strongest cause with which to garner support. By doing so, he unleashed a hornets' nest of often sharply worded and deeply argued criticism. Jeppsson, for example, felt compelled to send copious letters documenting in detail all that had happened since the 1950s and why the proposed scheme would damage conodont science. Dick Aldridge, who also fundamentally opposed the scheme, took a more dispassionate view. He told Jeppsson how “greatly impressed” he was that Melville, “who has to deal with ‘all' systematic zoologists in the world, has involved himself so deeply and thoroughly to bring about a solution of these problems.” Aldridge corresponded with Melville, hoping to school him in the niceties of conodont taxonomy, but Melville tenaciously held his ground. While admitting that conodonts were no longer the group in his sights, Melville felt duty bound to serve others who would benefit from the scheme. Aldridge pressed on – and not without effect. The arguments became increasingly refined and arcane. “I am gradually educating myself,” Melville told him encouragingly, but then warned, “and must ask you to accept that an old dog has difficulty with new tricks.”
³⁷

When Aldridge attended the Pander Society meeting in Vienna and Prague in August 1980, he feared he was still losing. Among the seventy-one conodont workers from twenty-five countries, parataxa once again became a hot topic, but now it produced absolute opposition. Those present drafted a petition – known as the Wolayer Resolution – which read, “We unequivocally reject these amendments to the Code and urge you in the strongest possible terms to vote against them…. As a nomenclature for parataxa would legalise a dual system of names, paranomenclature is antithetical to the purpose of the Code.”
³⁸
Aldridge wrote to Melville to warn him, explaining that he did not know if this was the right way to go about things but that it was now so late in the day that they felt compelled to try anything.

Melville was still willing to learn and asked Aldridge to give him a practical demonstration of the problem that October in London. When the two met, Aldridge found the
ICZN
secretary amiable and helpful. But as they were discussing the finer points of the proposed scheme, Melville's secretary entered the room with a letter from Walt Sweet. In seven neatly typed pages, Sweet set out a closely argued case against Melville's proposal. In fact, Sweet laid it on rather thick. This was not a letter seeking to forward science so much as win the argument and rebuff an unwelcome intrusion into a field that had so recently emerged from a difficult past. Sweet was manning the barricades again and ready for another civil war. He ended by warning, “Should the Commission approve the amendments involving ‘parataxonomy' and ‘paranomenclature,' you can expect a somewhat more extensive and more carefully composed response from me in the literature. I hope it will not come to that.”
³⁹
Sweet saw in the scheme the potential to undo all that had been achieved.

Melville thought Sweet's letter “magnificent,” and he responded at length using a well-honed style that must have seen him through many such arguments.
⁴⁰
It was smooth and diplomatic, cleverly and no doubt wittily using abstraction and generality to throw a thin veil over his criticisms of Sweet and his other detractors. He told Sweet that conodont workers had made themselves remote from the
ICZN
, and as a result “the structure of current conodont nomenclature suffers from severe logical weaknesses and is highly vulnerable.” Rather pointedly he observed, “If conodont workers in the mid-60's had taken the trouble to keep us informed of the exciting developments in taxonomy that were then taking place, we could have proceeded on a better basis of mutual understanding.”

Melville remained resistant to the last, and the commission pressed on and won the vote, but there were enough abstentions to prevent the proposal being integrated into the code. By little more than a technicality, the conodont workers had won the day. Melville reflected, “I was astonished at the strong feeling against the proposal and the – to me – cogent arguments that were advanced…. They pooh-poohed the idea of chaos. They believed that approval of dual nomenclature would cause neglect of, and even inhibit, solid zoological studies. Conodonts were used as an example of a group in which advancing knowledge had overtaken earlier and vaguer knowledge and the group is being put on an even firmer footing, without resort to parataxa.”
⁴¹
Clearly, the conodont workers were turncoats and they had now won their first battle fighting for the other side.

By 1982, the conodont workers considered themselves fortunate to have failed to establish parataxa in the 1950s, for during the following decade the assemblage asserted itself on all fronts. It could not be ignored, and it is very likely that Bergström, Sweet, and Webers would have taken their stand regardless. But with a firm system of parataxa in place there may well have been the fratricide Rhodes so feared. Now the conodont workers had the Marburg Proposals – a kind of peace treaty – which would enable the future to be negotiated with care. In time this shift of language and practice would throw up every expected problem and error, but the mountain did not collapse. It did not do so because despite Sweet and Bergström believing, in 1969, that all conodont workers would be using the language of apparatuses in just five years, thirty-two years later, Sweet and Phil Donoghue had to admit that only a third of genera had been reinterpreted in this way. The mountain remained unmoved because, for the most part, its makeup remained unchanged.
⁴²

 

PANDER'S ANIMAL WAS AS MYSTERIOUS AS EVER, BUT DURING
the 1960s it had begun to take possession of its skeleton. Fossils once considered teeth were no longer to be seen in isolation. For conodont workers this was a move toward biological truth and the only course if their science was to be considered rigorous and legitimate. Nevertheless, many worried about chaos, and some questioned the benefits. It had been the study of isolated fossils – which they were now abandoning – that had made this science so useful and effective. And it was this that had also given the animal a history, or rather, an evolutionary genealogy. Of course, this wasn't really how conodont workers saw it; most were interested only in acquiring a more refined tool. But out of this necessity emerged glimpses of the biological flesh of the animal itself, and it would do so repeatedly as the conodont workers acquired new methods and new ways of seeing.

The adoption of acids had produced a revolution in the study of these fossils, making them infinitely more numerous. Blessed with a wealth of data from different parts of the world, conodont workers began to ask spatial questions such as “Were some of these animals restricted to particular environments or parts of the globe?” and “Did populations of these animals move across the surface of the planet as conditions changed?” And as geology as a whole reached for a grand theory of the earth in the 1970s, so this kind of thinking was swept up into models imagining the global ecology of the planet. It became increasingly possible to imagine millions of these ghost-like animals living quite particular lives. There were, however, very practical reasons for this thinking; the science remained wedded to its stratigraphic goals. But, once again, the animal itself could not be suppressed. Indeed, the practical science needed to better know this animal if it was to progress.

In the 1960s, many workers believed that the conodont animal was unaffected by water depth or sediment type; its fossils were not indicative of a particular past environment. For Willi Ziegler, with his ambitions for a global stratigraphic standard, this was a matter for rejoicing: “Conodonts are like God – they are everywhere.” This view had been consolidated in the 1950s, as the Germans began to see American fossils in their own sections. Indeed, the wide geographical distribution of species, and their frequently reported association with fish and cephalopod remains, suggested that conodonts were swimming or possibly floating animals. Klaus Müller, however, was rather less convinced. Finding them less associated with corals, sea lilies, brachiopods, and reefs, he suggested that the animals
were
susceptible to environmental control and that they did not like strongly oxygenated bottom waters. But in another study in which the distribution of other groups of animals seemed to be controlled by environmental conditions, he found the conodonts immune. Frank Rhodes, Walter Youngquist, and A. K. Miller had reported finding conodonts in shallow-water deposits. Similarly, Reinhold Huckriede had found that his Triassic conodonts were most common in shallow-water limestones rich in cephalopods, sea lilies, and sponges, and that rocks formed in other environments often contained none at all. Maurits Lindström, on the other hand, had no difficulty in finding contradictory examples: conodonts with shallow-water corals and brachiopods, and in deep-water deposits. Müller, however, remained the doubter, and in the 1962
Treatise
he suspected that Branson and Mehl's most useful
Icriodus
was ecologically controlled.
¹

These discussions in the 1950s and early 1960s took place as the study of the ecology of the deep past, or paleoecology, finally gained a firm foothold in paleontology. The subject's scant coverage in the 1962
Treatise on Invertebrate Paleontology
conceals this change; Ray Moore was an enthusiast but felt the effort to include it redundant in the light of the publication, in 1957, of the 1,296-page first volume of the
Treatise on Marine Ecology and Paleoecology.
With its integration of both ecology and paleoecology, this new ecological series demonstrated the intellectual necessity of pairing the past with the present but also signaled in its title the relationship between the two, with paleoecology always following, and drawing analogies from, the present.
²

Among those advocating this new approach was Preston Cloud at the
USGS
. In the late 1950s, he saw paleoecology as the Promised Land, offering deeper understanding of life in the past: “Some of the most obdurate strongholds of ignorance in geology and paleontology await new or renewed assault by palaeoecological methods.” There was no shortage of methodological ideas, but, rather appropriately for a Promised Land, the subject's potential was as much an act of faith as of proven utility. As Cloud admitted, the field was “still groping toward a coherent body of critical observations and specific principles by means of which the evidence can be winnowed and refined, its applicability established, and durable inference reached where data are adequate.” British paleontologist Derek Ager saw paleoecology as lifting paleontology out of the realm of “stamp collecting” and extending the scope of the paleontologist to include “the whole world of living nature.” Others, however, would look on and worry about the rise of “impractical theorizers.”
³

So as paleontology crossed the 1950s borderland into the swinging 1960s, it was paleoecology that was hip, a new territory that could draw in those who wished to lay down its principles and philosophies. But those who pursued these opportunities did not believe all fossils held equal promise. Of particular interest to them were those that held utilitarian potential or could draw upon modern analogies in order to achieve ecological understanding. In the mid-1950s, for example, paleoecology had already proven its importance to oil and gas prospecting in the Permian reefs of western Texas and New Mexico, and oilfield geologists working with fairly recent strata – of Miocene age or younger – soon found single-celled benthic (seafloor-dwelling) foraminifera to be an almost perfect means to assess paleoenvironmental conditions, because these fossils were similar to living forms. Conodont workers could, by contrast, only mourn the biological ambiguity of their subject: “Determining the ecologic factors that influenced a group of organisms that has been extinct for 180 million years and whose biologic affinities are uncertain is a problem that still challenges students of conodonts. The fact that conodonts were widespread for 400 million years and are superb tools of biostra-tigraphy during this Cambrian to Triassic interval has compounded the problem.”
⁴

However, the problem of the conodont's ecology wasn't entirely insoluble; it was simply a matter of finding the appropriate tools, and these were easily located in practices that went back to the early years of the nineteenth century. Paleontologists, like epidemiologists, had adopted the habit of studying patterns in the relationships between two distinct things. The epidemiologist can by these means locate a link between smoking and cancer. Conodont workers such as Bergström and Sweet used this concept to help them construct assemblages from discrete parts, and geologists before them had used it to establish the principles by which fossils can be used to give rocks a relative age. If a mudstone is repeatedly found to contain a particular species of conodont, which is not found in neighboring limestones, then the conodont worker might presume environmental control since the mudstone was produced in an environment very unlike that which generated the limestone. It is a reading little different from that of the ecologist who links eagle to hare and both to an upland habitat.
⁵
And one extraordinary advantage of the conodont animal in this kind of study is that its elements were resistant to destruction and could be preserved in a range of rock types.

Paleontologists and geologists could now ask questions of rocks and fossils with the aim of understanding environmental conditions and ecological niche. One simply needed to identify and correlate consistent changes in rock and fauna.

In 1957, a number of workers on both sides of the Atlantic began to believe that some conodont animals had restricted distributions. At the Illinois State Geological Survey, Iowa-educated Carl Rexroad decided to test this idea in his local Mississippian rocks, but he found that while the limestones contained more conodont fossils than the shales, they held essentially the same kinds. The animals were not controlled by environmental conditions. But then Rexroad noticed that two genera,
Cavusgnathus
and
Gnathodus
, showed opposing abundances; when one was numerous, the other was not, and vice versa. He hypothesized the presence of two distinct provinces and then collected from a spread of sites to test the idea. The results seemed to confirm his suspicions, encouraging him to imagine an Illinois fauna being replaced by, or mixing with, southern immigrants known from rocks in Texas and Oklahoma.
⁶
The idea that faunal provinces could be recorded in the rock record was, however, not new. It had been demonstrated many times previously using macrofossils, so it was not surprising that Rexroad interpreted his rocks in this way.

Huckriede became convinced that his Triassic conodonts were also affected by fairly strong provincialism. Lindström too felt he had found a discrete Ordovician faunal province. This had occurred on his honeymoon trip to Scotland. He had left his wife, Ulla, knitting while he went in search of conodonts in John Smith's old collecting haunt of Morroch Bay, but it was she who found them. The fossils were slightly different from those Lindström knew in Sweden, and in a few years similar forms would be found in New England. He wrote these finds up in what he jokingly referred to as his “Rosetta Stone paper,” for here he had found conodonts in the hard shales that commonly preserve graptolites but no trilobites.
⁷
Trilobites and graptolites provided two distinct fossil-based timescales. Now the ubiquitous conodont connected them and threatened to surpass them both. It was this paper that caused Ziegler to joyously exclaim on the godlike omnipresence of his favorite fossil.

There were, then, a number individuals suggesting for the first time that different species of the conodont animal may have been separated geographically. These were, however, little more than footnotes in research that had other goals. A more forceful argument for conodont provinces originated in Walt Sweet's collaborations with a succession of his students and with Stig Bergström. It was in 1957 that Sweet began his long assault on the Ordovician. He had three of his master's degree students – Caroline Turco, Earl Warner, and Lorna Wilkie – undertake a stratigraphic study of the conodonts of the lowermost horizons of the Upper Ordovician where it outcrops along the Ohio River. In all, these newcomers collected and processed some ten thousand conodonts from shale samples. Sweet, who had promised to bring their work together in a joint paper, was not deterred by the large number of long-ranging, and thus stratigraphically useless, conodonts in the samples. Instead, he saw in these long-ranging species a phenomenon that greatly interested him: two distinct and interacting faunas.
⁸
Drawing on recent work on climate change in the Ordovician, he painted a picture of a mass migration of these unknown animals. The period opened with a north-westward invasion into the area of cold-temperate forms that belonged to an “Anglo-Scandinavian-Appalachian province” known to have existed from studies of other fossils. These conodonts diluted, or coincided with an emigration of, a presumably warm-temperate “mid-continent fauna” from the area. This invasion of coldwater forms was, however, apparently short lived and soon reversed, bringing back that midcontinent fauna that had occupied the area in the Middle Ordovician. To this he could add his own data, which suggested a later “invasion of even warmer tropical or subtropical forms probably from the north-west or north.” Sweet's compass directions here refer to the modern-day positions of the rocks. The North American continent has rotated and moved since the Ordovician, when these rocks were laid down. Consequently, Sweet's migration of tropical forms at the time came from what was then the west or southwest. Nevertheless, the varying abundance of different species and their intermixing preserved these dynamic shifts in populations of the animal nearly five hundred million years ago.