Conodont microfossils are very small structures
looking like spiky teeth, combs and other weird things. Their enigmatic nature was constantly exciting generations of paleontologists since their
initial discovery: it was not clear which part
of which animals these things do represent. Conodont elements were many, but they
were found without association with any other fossils.
This situation continued
for many years while researchers were proposing all possible, sometimes
absolutely crazy ideas. The answer came relatively recently, when lucky scientists
finally dug out the entire animals containing conodont elements in their mouths.
It turned out that these animals were primitive eel-like soft-bodied chordates,
which were using conodont elements to bite and retain the prey.
Here is a link to the paper in PNAS by Nicolas
Goudemand with coauthors that describes the reconstruction of a conodont mouth
apparatus: “Synchrotron-aided reconstruction of the conodont feeding apparatus
and implications for the mouth of the first vertebrates”.
http://www.pnas.org/content/108/21/8720.full
Conodonts are specifically interesting since
they represent first really solid tissues in the body of early chordates. Based
on everything we know today about evolution of the head, it seems that conodonts
must be derived from the neural crest stem cells. If true, this might mean that
first genetic regulatory network controlling scale formation, making teeth and
all other skeletal elements in the body was developed in the neural crest
lineage and only later was “borrowed” by the mesoderm. Thus, there is a high
chance that all parts of our skeleton are the consequences and, in a way,
derivatives of these ancient tooth-like structures called conodont elements.
Isn’t it funny to think that the genetic program for making bones in our arms was
born to make tiny teeth originating from neuroepithelial tissue?
P.S. Some scientists still doubt that conodonts are true chordates.
No comments:
Post a Comment