Conodont Animal

 Conodont body fossils are extremely rare but the tooth like elements are common. Complete element apparatuses also rare but they are known from several localities, even the best  are preserved in a somewhat distorted mash.  Complicated elements of the mouth collapse during decay leaving a confusing jumble of elements. Conodonts are abundant in the fossil record for about 340 million years varying in shape and assemblage. Conodonts were so diverse as a group that they are the ruling fossil group of the late Cambrian to the late Triassic marine environments. The diversity is in the elements also, there are literally thousands of element shapes representing many variations of the animal thought itís history.

All the known apparatuses are made up of several kinds of up to 20 elements, coniform, ramiform and pectiniform blade and platform elements.  Coniform elements were dominant in the Cambrian to Early Ordovician and common until the Devonian. Ramiforms were comb-like elements, and pentiniform elements were with straight or arched blades, some expanding laterally to form a platform. Conodont elements are calcium phosphate laminations covering a basal cavity. The basal cavity is capped by a large tooth-like projection termed the cusp, the cusp or cusps make up the elements. Conodont elements grew through the external addition of layers of apatite around the basal cavity, which suggests that the elements may have grown throughout the life of the animal. Since fossil localities containing complete apparatuses are rare, understanding of how they functioned is limited to available material.

Conodont elements were first described in 1856 by Heinz Christian Pander and it wasn't until 1982 that Euan N. K. Clarkson noticed the first conodont animal fossil while examining an old collection from the Granton Shrimp Beds. Conodont body fossils are extremely rare, there are only 4 localities known to preserve any soft tissue. Almost 10 complete body specimens are known from Scotland's Granton Shrimp Bed, still not much more than a dozen soft body fossils are known world wide. The best  is Clydagnathus windsorensis from Scotland's Carboniferous, it has large eyes, a notochord and muscle bands running along a thin eel like body of about 1.5 inches or 4 cm. Specific structures of the mouth and the placement of the commonly found tooth like elements in the animal are open for debate and at best scientific speculation. Complete conodont element apparatus are mostly preserved in a somewhat distorted mash, and through scientific analysis we can interpret them.

The conodont animal Clydagnathus windsorensis from Scotland, with a close
up of the elements that made up its dentition.  

Conodont elements were likely placed in groupings on cartilaginous pairs much like modern hagfish. In the hagfish cartilage  tooth plates are pushed out of the mouth and placed on the food item, as  the plates are pulled back inside they automatically  position themselves, in the case of hagfish tearing out chunks of dead flesh.  Close examination of the some pentiniform elements shows scratched and chipped points of contact from grinding against one another, and some elements show sheering or abrasive wear. This suggests that conodonts were specialized hunters and actively feeding on a variety of pray items, the simple act of closing its mouth would make escape improbable.

Conodonts were actively hunted as well, elements have been found in a coprolite of  conodontophagous, as stomach contents of the enigmatic Typhloesus wellsi,  and in fish such as Gogosardina a little sardine. Evidence suggests the Gogosardina likely choked to death swallowing a conodont, and the majority of over 50 specimens of Typhloesus wellsi have at least some conodont elements in there gut. The problem with Typhloesus is the elements very in number and kind so each specimen is different; perhaps this site is an example of scavenging, not predation at all. The Lamprey, a modern Agnathan dies in great numbers after mating, it's cloaca (reproductive opening) stays open after reproduction allowing killing bacteria to enter; at least some teeth will fall out in the early stages of water decay.

Conodonts were chordates belonging to the superclass of Agnatha, a group of mostly extinct jawless fish. Modern Agnathans cannot regulate their own body temperature and they have metabolisms that are slow in cold water.  They have no distinct stomach and do not have to eat very much, a hagfish may not eat for weeks.  Conodonts are not a direct lineage as Hagfish have representatives in the fossil record from the same time period. Conodonts have been found in a variety of marine environments, shallow or nearshore to open water.

The largest known conodont animal is Promissum pulcrum from the Ordovician Soom shale in South AfricaPromissum follows the standard body plan though it is significantly bigger,  unfortunately only the front half was found.  A total body length estimate of 40 cm  was made by taking a 10 mm ramiform element from a Promissum and comparing it to a .76 mm ramiform element from a complete Granton body fossil.

 Conodonts only have a posterior tail and caudal fin much like a modern lamprey, and there mouth shape is undetermined with no direct fossil evidence, they had large eyes for there size. Even though Promissum had a larger body its eyes were proportionally smaller than other conodonts. This suggests that the conodont eye design reached it's maximum size before the body size of  Promissum pulcrum.  

It is likely that the conodont animals  550 or so known genera, would have gone through many changes in there 340 million years of dominance, so we only have a small widow into there history. Due to there size conodonts most likely were hunting  in the planktonic column. Plankton was reduced several times in histories extinctions, possibly also contributing to the conodonts final demise much like the other fossil great the ammonite. 




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