The Great Fossil Enigma: The Search for the Conodont Animal

4: Another Fine Mess

81 81 Another Fine Mess There were three ways to solve the riddle of the conodont. The first was to think differently about things known, but if anything too many people were thinking differently. The second was to find better material but this seemed only to deepen the problem. The third–taking advantage of the kind of technological change Zittel and Rohon thought empowering–was to journey into the object itself, and no one had attempted that since the late nineteenth century. An unexplored trail down which progress might be found, in the late 1930s it called to a number of those who had recently become fascinated by the fossil. Among them was Clinton Stauffer, who was perplexed by that simple paradox that now seemed to be at the heart of the problem: an animal with a wormlike arrangement of teeth composed of material indicative of a vertebrate. It prompted him to ask, was the phosphate truly part of the tooth or mere contamination? If simply contamination, then the mystery was solved: The animal was a worm. He asked his technically mindedMinneapoliscolleague,DuncanMcConnell,toresolvethe matter. McConnell examined the fossil’s chemistry and crystallography and reported that the conodont was indeed composed of material structurally and chemically similar to that making up vertebrate teeth. Stauffer could only conclude, “It becomes evident that the only way to relate conodonts to the worms is to postulate an entirely new group of extinct forms with vertebrate-like teeth.” He continued, “Which might be equivalent to suggesting that they are primitive vertebrates.” Stauffer had been on this vertebrate track for some time, but just as McConnell seemed to give him the confirmation he needed, Bill Furnish, supported four 82 The Great Fossil Enigma by Branson and Mehl, debunked his earlier suggestion that the bar-like conodonts were jaws with teeth inserted in them.1 Furnish, who was looking very closely at his fossils too, also believed he had examples of conodont fossils in his own collections showing breakage and repair but not abrasion or wear. This suggested to him that conodonts were perhaps used for grasping rather than mastication. Stauffer’s interpretation of the bar conodonts as jaws indicates how little the Americans knew of the interior structure of conodont fossils even in 1940. Up until then, every internal investigation had been undertaken in German-speaking Europe. This, however, was about to change. TheyoungWilbertHasswasconvincedthattoomuchfaithhadbeenput in the simple analogies that might be drawn from an examination of the fossils’ external morphology. He was not the first of this new generation who aspired to look into the interior structure of fossil, but those before him had been prevented from doing so by the poor quality of the fossils they found. Situated in Washington, at the heart of the U.S. Geological Survey, Hass was undoubtedly in a privileged position as he could call upon some of the best conodont fossils in the country, and among these he found translucent specimens collected from the Mississippian by Roundy and Chalmer Cooper.2 By grinding these down, he could produce thin sections for the microscope. Recognizing that he must compare his findings with Pander’s original descriptions, Hass had Pander’s book translated. Armed with those descriptions in one hand and “beautiful sections” in the other, he began themostdetailedexaminationofthestructureoftheconodontinnearly a century and in doing so called upon technologies far better than those available to Pander. Hass also had the advantage of large systematic collections ,whichevenfromacasualsurveyseemedtosuggestthattheanimal ’sevolutionhadledtoanincreaseinthesurfaceareasoftheelements, culminating in plate-like forms. He also concluded that conodonts grew coneonconebytheadditionofmaterialtothesurfaceandnot,asPander had suggested, by internal secretion. Hass’s biggest contribution, however, concerned the more complex compound conodonts, which grew like the simple cones but did so from a number of points and in various directions (figure 4.1). Some of these Another Fine Mess 83 conodonts became progressively simpler in form as the animal matured and as some growth points were suppressed. In other words, some of Pander’s teeth–unlike vertebrate teeth–actually changed shape markedlyastheygrew .Ifthesereallywereteeth,thenthissuggestedthattheir functionchangedovertime.Thisdiscoveryitselfseemedremarkable,yet it raised a rather more pressing issue: how to distinguish a mature specimen from a growth stage. There was simply no way to tell from the exterior morphology, as two quite different fossils might simply be growth stages of the same species. For Hass this too was a revelation because it meant one could not identify species on the basis of an additional bump or ridge, as had...