The Great Fossil Enigma (13 page)

The conodont fish that had been so often denied now began to swim freely in American minds. For example, when Frank Gunnell discovered that a Mesozoic hagfish fossil was intermediate in form between the modern hagfish and the ancient conodont, he could not help but apply a naïve evolutionary determinism then prevalent in U.S. paleontology to connect the dots. He thought it likely that conodonts would one day be found in quite recent rocks, and knowing that the hagfish was considered a primitive vertebrate, he was sure that conodonts would “aid in establishing many heretofore unknown evolutionary relations among the vertebrates.”
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To later scientists such views might seem prophetic, but like his restatement of the fish-petroleum theory, they simply reflected a contemporary moment when these ideas floated unauthored and available for application in that broad church of the new and practically minded micropaleontology.

In America at this time, what might be considered true or known could so easily get mixed up with mere conjecture. Thus when Stauffer and Plummer immersed bar conodonts in hydrochloric acid and discovered that the tooth-like points (denticles) fell out, they could not help but imagine them as tiny jaws with vertebrate-like teeth set in them. Stauffer had visualized such jaws even before he could induce his “teeth” to fall out. The fish that swam through American minds placed expectations into the way these scientists looked. They imagined the fish. Indeed, the enigmatic nature of the animal was once again permitting science to dream and believe, as Macfarlane did, that one day the animal would be found: “It may be hoped however, either that more definite light will be shed by further study of conodonts, or that some layer of subaquatic volcanic ash may yet be discovered, in which as with the medusae, the annelids, and the skates of the Solenhofen slates, fossilized cyclostomes may be discovered.”
¹³

These confident assertions about the conodont fish traveled across the Atlantic to Germany. There, in 1928, near Osterode in the Harz Mountains, work began on a dam, the Sösetalsperre, which was to produce the country's largest water reservoir. It was along the forest road built for the construction traffic that Wilhelm Eichenberg, of the Geological Institute at the nearby University of Göttingen, found great numbers of conodonts on the surfaces of Lower Carboniferous shales.
¹⁴
His first inclination was to use this material to emulate the detailed microscopic analysis of Pander, Zittel, and Rohon, but his conodonts were extraordinarily brittle and simply shattered when he attempted to expose them. He was familiar with the work of Ulrich and Bassler, Kirk, Hinde, and others, and accepted unquestioningly the American position; conodonts were the remains of fish.

Fortunately for Eichenberg, his university possessed an important expert in these animals; zoologist Franz Stadtmüller was then busy investigating the gill apparatus of living fishes. Stadtmüller gave Eichenberg access to the zoological collections but also advised him on his finds. Eichenberg could now see that conodonts were “skin teeth, plate teeth, plates,” and – a new interpretation – “filter extensions of the gillarches.” In other words, each type of conodont performed a particular function in a single animal and in so doing formed complex respiratory and feeding apparatuses. Following the suggestion of another Göttingen colleague, Hermann Schmidt, Eichenberg introduced the collective term Conodontophorida, or “carriers of the Conodonts,” to refer to this group of animals. By implication, then, “conodonts” were now the “elements” (a zoological term he borrowed from Stadtmüller) making up these apparatuses. For Pander, “conodonts” were fish, but now Eichenberg made the term apply to the individual fossils. In doing so, he adopted what was already becoming common practice in the United States. His final piece of rethinking involved the naming of the animal itself. Since the elements came from the same stratum and were components in a single animal, as he imagined it, he grouped them together and called the animal that possessed them
Prioniodus hercynicus.
This name came from just one of the elements, and Eichenberg's use of it in this way was simply an application of the rules of zoological nomenclature, which said that when once separately named fossils are found to belong to a single animal, the longest-established name in that group of fossils should become the name for the animal and thus for all the fossils of which it is composed.

Although based on the importation of American ideas, Eichenberg's analysis meant that Ulrich and Bassler's simple taxonomy, which had yet to take hold, was merely an abstraction, and he called for it to be abandoned. Optimistically, Eichenberg felt the answer to the long-contemplated question of the conodont animal's identity was almost in sight: “All that remains still to be wanting is into which order of fossil fish are the Conodontophorida…to be arranged.”

The fossils making up Hinde's
Polygnathus
had been found in close association, but that animal proved unacceptable. What chance of survival had Eichenberg's complicated
Prioniodus?
His animal was even less certain and, being published in German, had other obstacles to overcome before it could penetrate American circles. Now two radically different fish swam in the minds of paleontologists – one separated from the other by the Atlantic. They could coexist because they were separated by numerous physical, linguistic, ideological, and cultural barriers.

Eichenberg's fish acquired more flesh four years later when forty-one-year-old paleontologist Hermann Schmidt acquired some quite remarkable fossils. Schmidt had actually found his first example of these new fossils a few years before, in a brickyard near Hemer in Westphalia. It showed conodont elements in close association, but the specimen was so poor that he thought no more about it. Then a collector showed up with a similar fossil. It had come from the same rock at the base of the Upper Carboniferous, but from Arnsberg, more than fifteen kilometers distant from Hemer. Perhaps these were not chance occurrences? Schmidt returned to the quarry in the spring of 1933, doubtless looking a strange sight as he systematically examined the bedding planes with a magnifying glass. The effort paid off, and in time he located nine specimens showing conodont elements in groups. In some of these the elements themselves were preserved, but in others all that remained were impressions of them in the rock. Most of these groups of fossils were surrounded by a dark patch of bitumen enrichment that he interpreted as decayed tissues of the animal. This meant, of course, that the association was natural; these elements had once occurred together in the body of a single animal.
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On closer examination, Schmidt discovered that there was a consistency to the grouping of the different element types; some groups were in complete disarray, but others showed a repeated arrangement, which gave a clue to their relative positions in the living animal. Schmidt attempted a reconstruction – the first time anyone had tried to do this – by interpreting the arrangement he saw on the bedding planes but always with Eichenberg's functional arrangement of the different parts in mind. His was not to be an original interpretation but an extension of the German model. This suggested that a pair of strong, bladelike conodonts acted as mandibles, each showing signs of having grown in close relationship with the other. Behind the mandibles, which “seized and cut,” sat a pair of “spiky” elements that pointed forward as if to cause mortal injury to the prey. Behind these were the most numerous group of elements – slender, comb-like forms Schmidt interpreted as components of the gill apparatus (
figure 3.1
). For Schmidt the conodont animal was a fish even before he began his reconstruction. Of this he was already sure. He even considered the possibility that a fish fossil found in the same bed might actually be the owner of this assemblage. The head of that fish, however, had not been preserved.

3.1.
Schmidt's fish. Schmidt's reconstruction of the conodont apparatus closely mirrored the arrangement of the fossils in his fine natural assemblages. So perfectly did this seem to fit the anatomy of Eichenberg's conodont fish, he had no difficulty producing this three-dimensional model. In this drawing, the jaws are on the left and the gills on the right. From H. Schmidt,
Paläontologische Zeitschrift
16 (1934). © Verlag von Gebruder Borntraeger.

Schmidt reported his finds to a meeting of the German Palaeontological Society, the Paläontologische Gesellschaft, in September 1933, publishing a fully illustrated account the following year. Like Eichenberg, he gave his assemblage of conodont elements a single name drawn from one component,
Gnathodus integer.
In doing so, he claimed that there were far fewer true species of conodont than the Americans believed. His findings added weight to the German call for Americans to abandon their simplistic taxonomy and group together conodonts from the same stratigraphic horizon, giving them one name and recording the frequency of each type found. It was not simply Eichenberg's anatomical model that suggested this but also Schmidt's photographs, which spoke convincingly of the natural association of the different parts. Anyone picking up the paper would have seen this; it required no proficiency in German. The animal itself had left its own visual argument, and one just as powerful as those constructed by Hinde, Rohon and Zittel, and Macfarlane. Schmidt's associations preserved exactly the same mix of forms Eichenberg had found, and while they demonstrated that Hinde's
Polygnathus dubius
possessed too many conodont elements to be the remains of a single animal, that specimen did contain elements in the same proportions as Schmidt and Eichenberg had found. What none of these associations possessed, however, were those simple teeth Pander had discovered in such profusion in the older rocks. Now Schmidt wondered if these had come from an entirely different animal.

In a few short pages, and some remarkably convincing figures and plates, Schmidt proposed a revolution in the way conodont workers should consider their subject. To German eyes, at least, progress was being made: The American fish had now been given a German apparatus and had become rather more biological. The results were in many respects conclusive, but was it already too late to change the American way of doing things? In 1933–34, the American conodont machine – Branson and Mehl, Stauffer, Cooper, and Huddle – acquired a head of steam and was moving forward at a tremendous pace. Had Schmidt published in English in the United States, would it really have stopped this machine in its practical tracks?

On this possibility we can do rather more than speculate, for when Schmidt published his finds, twenty-eight-year-old Harold Scott of the University of Montana's School of Mines in Butte was making a similar discovery.
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The remarkable coincidence of these events has fascinated conodont workers, but Schmidt and Scott were not the only workers finding these “natural assemblages” at this time. As we have seen already, the conodont fossils only came to light when people started studying fossils with microscopes. By the early 1930s, micropaleontology was the new fashion and an increasing number of graduates were engaged in looking at rock surfaces in search of tiny fossils. In a few years most would turn to those mass processing techniques Branson and Mehl so favored, and in doing so lose any hope of understanding how the different conodonts are associated in the rock. But of all the microfossils being used in the new science, only conodonts were affected in this way by this change of practice. In the early 1930s, however, workers were not set in their ways and there were still doubts about the boiling and sieving of sediments. So, for a few years, there was a much higher probability that associations would be found: More people were looking and fewer were boiling samples.