Mm. Smith et Mi. Coates, EVOLUTIONARY ORIGINS OF THE VERTEBRATE DENTITION - PHYLOGENETIC PATTERNS AND DEVELOPMENTAL EVOLUTION, European journal of oral sciences, 106, 1998, pp. 482-500
The theory that teeth evolved from dermal denticles linked with the or
igin of jaws no longer accounts for the diversity of new data emerging
from the fossil record. We have reviewed oropharyngeal dental pattern
s in all fossil groups of early vertebrates to establish the primitive
condition, in order to understand the polarity of change. The evoluti
onary procedence of dermal denticles before teeth now seems less likel
y; both may be alternative manifestations of a common morphogenetic sy
stem. This developmental system involves regulatory changes affecting
the odontode, a fundamental exoskeletal unit, and can explain skeletal
diversity. However, tooth and denticle differences may have diverged
at loci deep within vertebrate phylogeny, as real differences exist be
tween them. Teeth were conceived as evolving from non-growing odontode
s with regulation of precise increase in size, position, sequence of t
ime of development, and polarity of shape. A characteristic feature of
teeth is the ability to replace from a developing sequence, programme
d with these parameters, prior to demand. Tooth whorls, a feature of d
enticles in the oropharyngeal region, may be regarded as a preadaptati
on of this tooth replacement mechanism. The new fossil evidence sugges
ts that teeth may have evolved from these more specialised oropharynge
al denticles in agnathan vertebrates.