The Great Fossil Enigma (5 page)

It was Pander's reading of these objections, two years before his own book was published, that spurred him on to develop a fully argued case for the fish. But Pander was perhaps too open in even this analysis as his unsympathetic colleague in St. Petersburg, Karl Eichwald, turned Pander's own doubts about the conodont's peculiar construction against him and suggested that the conodont fossils came from the skin covering of that sausage-shaped relative of the sea urchin, the sea cucumber.
¹²

The debate concerning the identity of the fossils took a new turn, however, when, in the late 1850s, some English analysts discovered that conodont fossils contained traces of calcium phosphate, the material which makes up vertebrate bone and teeth. Pander now felt even more confident about his conclusions. Murchison, the self-proclaimed historian of the oldest fossiliferous rocks, was once again on the back foot and now called upon the distinguished British anatomist Richard Owen to provide a definitive diagnosis. Owen, who had taken charge of the natural history departments of the British Museum in the year Pander's book was published, was a human encyclopedia of animal physiognomy, expert in both vertebrates and invertebrates, living and fossil, and a student of teeth. It was reasonable to believe that he was the man in all Europe most capable of solving the riddle.
¹³
Pander himself had used Owen's work to interpret these tooth-like fossils.

Owen approached the problem with an open mind. He knew that recent decades had brought to light “every type of invertebrate animal” in the older rocks and that the development of life appeared to follow a non-evolutionary progressive and branching course. At first this growing list of very ancient animals had caused surprise, but now Owen was willing to consider the possibility of vertebrates also being present in these older rocks. At the time, the earliest fishes came from the Upper Silurian. Pander's discovery pushed them back into the Lower Silurian, or what we would now know today as the Lower Ordovician (a term introduced later in the century to resolve the disputed overlap between Sedgwick's Cambrian and Murchison's Silurian).

Owen examined Pander's “minute, glistening, slender, conical bodies” under his microscope and published essentially the same report three times between 1858 and 1861, making only minor alterations with each new revision.
¹⁴
In 1860, for example, and perhaps in deference to Murchison, Owen described Pander as an “accomplished naturalist and acute observer” and his book as “an important work.” But in 1861 he found no place for these compliments. In 1860, he raised the possibility that a few of Pander's fossils might have claim to “vertebrate rank” but then admitted “that the parts referred to jaws and teeth may be but remains of the dentated claws of
Crustacea.”
The recent recognition of calcium phosphate caused Owen to give greater consideration to the vertebrate origin of conodonts in that year. Here, Owen alighted upon a new analogue, the whale shark (
Rhinodon
), which although typically nine meters in length has rows of thousands of two-millimeter-long teeth. But Owen agreed with Pander that these teeth were never attached to bone. So he considered Pander's hagfish theory but here felt the conodonts were “much smaller, slenderer and far more varied” than the teeth of that group of fishes. Then he asked, if they did need to be attached to a “soft substance,” then why not a “soft Invertebrate genus”? Certainly they seemed not to belong to an animal with a shell (because no shells had been found), and by a process of deduction, and not finding any perfect solution himself, he concluded that “they have most analogy with the spines, or hooklets, or denticles” of the slug-like naked mollusks or worms. Owen offered these as the least problematic and contradictory possibilities. He certainly saw no grounds for Pander's more narrow interpretation: “The formal publication of these minute ambiguous bodies of the oldest fossiliferous rocks, as proved evidences of fishes, is much to be deprecated.”

For some, Owen's verdict was definitive, his scientific indecision concealed behind his clear preference for an unproblematic invertebrate. Beyond the inner circles of metropolitan science, Owen's self-styled greatness was received wholesale, even if many in the city, such as the young Thomas Huxley, “feared and hated” him: “He can only work in the concrete from bone to bone, in abstract reasoning he becomes lost.”
¹⁵
Pander's fish had relied upon Pander's imaginative capabilities, and in Huxley's view this was a facility Owen lacked.

In June 1861, when Owen's most recent opinion was published, Huxley was engaged in the Panderian act of studying the embryology of the chick's skull. He, too, would soon be called upon to ponder the conodonts. As secretary of the Geological Society of London, he presented a paper on these fossils written by his associate, John Harley of Kings College, a Ludlow fossil collector who had earlier provided fossils for Huxley's investigation of giant fossil “sea scorpions,” or eurypterids. Believing Murchison's Silurian to be “the Crustacean Age,” Harley had gone in search of crustaceans in the Ludlow Bone-Bed, a deposit made famous by Murchison, who described it as “a matted mass of bony fragments, some of which are of a mahogany hue, but others of so brilliant a black, that, they conveyed the impression that the bed was a heap of broken beetles.”
¹⁶
Murchison interpreted these fossils as the remains of primitive fish and thus possibly the earliest record of vertebrate life, but he could not get any good specimens of these fish and so could say little about them.

Harley's solution was to break and wash pieces of the bed. It was by a similar technique that Pander found his first conodonts. Now Harley found “minute bodies,” too, and looking at them through his microscope, he thought they were like those described by Pander, a fact that seemed to be confirmed when Huxley gave Harley two of Pander's own specimens. But Harley, who looked with crustacean eyes, could see nothing piscine in his specimens or in Pander's, only the spiny protection of the modern horseshoe (or king) crab (
Limulus
). He concluded that all his finds, including the conodonts, came from crustaceans and in all probability from the shrimp
Ceratiocaris
, on which the conodonts performed as “minute spines which were attached to the tail-spines.” He convinced himself that this was the case by examining specimens of mantis shrimp in the collections of the Museum of Comparative Anatomy at King's College in London. Sure in his conclusions, Harley set up a new genus to accept all his material:
“Astacoderma
is a name I would give this genus, in which I would also include the whole of the so-called Conodonts, and thus give them at once a natural association, and a more appropriate name.”

By coincidence Dr. Alexander von Volborth of St. Petersburg was making a short visit to London at the time. In conversation with Murchison and Huxley at the Museum of Practical Geology, he told them that he was convinced that the conodont was no limited phenomenon but was to be found wherever the Silurian occurred. Huxley told Volborth of Harley's discovery, and this sent Volborth in search of the author. On viewing Harley's collection, Volborth was convinced that a small tooth was indeed one of Pander's conodonts. Making the long trip up to Ludlow, he too found conodonts in the rock, hundreds of them, he said. But these were quite unlike those he knew in St. Petersburg: They were white, opaque, dull, and brittle. Nevertheless, when Pander saw them, he felt he could confirm the conodont's peculiar internal structure. Volborth also found conodonts on the Swedish Baltic island of öland, though these were of the familiar kind.
¹⁷
Whether Harley's rather odd fossils really were conodonts was, however, not beyond doubt. Certainly those he figured looked nothing like them, but then no one was quite sure how varied these new fossils could be.

By the end of 1861, the conodont had at least six possible identities: fish, sea slug, marine worm, sea cucumber, trilobite, and now crustacean. Each was the product of a rather different outlook. Pander had unquestioningly been rather narrow in the kinds of animal he considered but had been very open and imaginative about the anatomical possibilities of vertebrate life. One might expect a fish paleontologist who had in his lifetime seen the discovery of the most remarkable and unexpected fossil fishes to have this open mind. Owen was by comparison an encyclopedist. If this permitted him to admit a huge diversity of animals into his analysis, it by implication made him rather more the generalist and content to work within the known categories of life. He was not one to think very far beyond the apparent natural order of things. Harley was an entirely different kind of naturalist: an enthusiast, rather less informed and as a result having a tendency to naïve assumptions and conclusions. To these we might add Carpenter and Eichwald. With the mythologizing of the animal, the varying capabilities, scientific status, and outlook of these authors would be overlooked; all views would be considered equally valid. By 1861, the extraordinary riddle of the animal's identity was becoming the fossil's most important feature. The conodont was acquiring the mantle of perpetual uncertainty, which others would recognize and develop. As its mythological status developed, so it acquired a long tail of speculation. It became the very portrait of puzzlement.

Nevertheless, each actor who confronted the problem thought he possessed the solution. In the 1867 edition of
Siluria
, for example, Murchison published Owen's 1858 opinion and stated with satisfaction that “the question [of the conodont] is completely set at rest.”
¹⁸
It wasn't that Murchison believed the issue of affinity settled – he knew Owen was tentative on that point – but that science could now be sure that these were not the remains of vertebrates. This was the critical point for both Owen and Murchison. It was a rather secondary concern to know what the conodont actually was.

However, even if paleontologists like Owen had grown accustomed to the strangeness of the fossil past, the conodont could not easily be pushed into the shadows, for whenever these evocative little things came to light, usually as unexpected and chance finds, they astonished the finder. Throughout the nineteenth century conodont fossils were sufficiently rare to produce in collectors those same feelings of wonder and amazement that had once affected Pander. These were precisely what Bath amateur geologist and fossil collector Charles Moore felt when he found them.

Moore had long collected from the Carboniferous Limestone and had, by washing debris found in fissures in the rock and sorting them under his microscope, made the sensational discovery of Triassic mammalian teeth.
¹⁹
Nevertheless, he was not prepared for the sight of conodonts when this same technique turned them up in the late 1860s. These were quite unlike those Pander had seen: “Their forms are about as eccentric as can be imagined.”
²⁰
Rather than illustrate these fossils, he painted a word picture that began with teeth that were remarkable for their scale and imitation of a larger form. It ended with forms that to this seasoned collector seemed utterly bizarre: “a minute conical fish-tooth”; another “not unlike the central cusp of a hyboid tooth”; another with “teeth arranged on an irregular or waved platform…too eccentric for description”; “nine curved teeth, arranged somewhat symmetrically, graduating in height from the centre, but with a much larger fang at one end”; “a long curved tooth at one end, throwing off a semicircular spur, which passes under a base-line, on the top of which follow numerous small depressed regular teeth”; “some instances with serrations as close-set and minute as are the bristles on an insect's limbs”; like “an old-fashioned rat-trap.”

Moore had discovered an Aladdin's cave of organic wonders, and it was to Murchison's
Siluria
, and particularly to Owen's diagnosis of Pander's “curious fossils,” that Moore now turned in an attempt to explain his own finds. He believed that he was the first to find these fossils above the “Lower Silurian.” Certainly the 1867 edition of Murchison's
Siluria
recorded that Pander and others had found them from the Upper Silurian, Devonian, and Carboniferous Limestone. As to what the fossils were, Moore agreed with Owen but added, “One objection to it is the variety of forms they present, and that we have no existing analogues.” Moore's bizarre specimens seemed to remake the imagined animal. It now appeared even less certain.