Page 80 - The Transitional Form Dilemma

THE TRANSITIONAL-FORM DILEMMA

ists err in thinking that animals with similar skeletons also possess sim-
ilar soft tissues. Michael Denton makes the following comment on this
error by evolutionists:
Further, there is always the possibility that groups, such as the mammal-like
reptiles which have left no living representative, might have possessed features
in their soft biology completely different from any known reptile or mammal
which would eliminate them completely as potential mammalian ancestors,
just as the discovery of the living coelacanth revealed features in its soft
anatomy which were unexpected and cast doubt on the ancestral status of its
rhipidistian relatives. 39

After studying the skulls brains of so-called mammal-like reptiles,
scientists concluded that these creatures did not possess mammalian
features, but entirely resembled reptiles. Mammals are distinguished
from all reptiles (including mammal-like reptiles) by the size of their
brains:
Similar considerations cloud the status of other classic intermediate groups
such as the mammal-like reptiles, a group of extinct reptiles in which the mor-
phology of the skull and jaw was very close to the mammalian condition. The
possibility that the mammal-like reptiles were completely reptilian in terms of
their anatomy and physiology cannot be excluded. The only evidence we have
regarding their soft biology is their cranial endocasts, and these suggest that, as
far as their central nervous systems were concerned, they were entirely reptil-
ian. Jerison, who has probably had more experience studying the cranial endo-
casts of fossil species than any other authority in the field, comments on the
mammal-like reptile brains: “. . . these animals had brains of typical lower ver-
tebrate size. . .” Since their endocasts were all very near the volume of the ex-
pected brain sizes and since the endocasts present maximum limits on their
brain sizes, the mammal-like reptiles could not have had brains that approached
a mammalian size. . . . The mammal-like reptiles, in short, were reptilian and
not mammalian with respect to the evolution of their brains. . . . The earliest
mammal for which there is reasonable evidence, Triconodon of the upper
Jurassic period, was apparently already at or near the level of living “primi-
tive” mammals such as the insectivores or the Virginia opossum. 40
Actually, mammal-like reptiles were described as such merely on the basis of

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