The Origin and Evolution of Mammals - Moodle

(Fig. 3.2(f)), is actually an ophiacodontid. It is a small
pelycosaur with a skull about 9 cm long and a body
length of around 50 cm including the tail, that was
discovered in fossilised lycopod tree stumps of
Florence, Nova Scotia, in Pennsylvanian deposits
dated at about 315 Ma. Its long, slender snout bears a
row of little, sharply pointed teeth, one of which is
distinctly caniniform. The postcranial skeleton of
(a)
(d)
Edaphosaurus
(e)
(b)
EVOLUTION OF MAMMAL-LIKE REPTILES 23
Archaeothyris is not yet very well known. The generally
similar, but relatively much larger and longer
snouted Ophiacodon (Fig. 3.5(a)) is one of the best
known of all pelycosaurs. It appears in the latest
Upper Carboniferous Stephanian of North America
and remains common throughout the Early Permian,
when some species achieved a very large size, up to
about 300 cm in length. There are several indications
(c)
Edaphosaurus
Ophiacodon
Glaucosaurus
Ianthasaurus
Figure 3.5 Ophiacodontid and edaphosaurid pelycosaurs. (a) reconstructed skeleton of Ophiacodon retroversus (Romer and Price 1940).
(b) Incomplete skull of Glaucosaurus megalops (Modesto 1994). (c) Specimen of Ianthasaurus hardestii showing cross-pieces on neural spines, and
simple dentition (Reisz and Berman 1986). (d) Reconstructed skeleton of Edaphosaurus boanerges (Romer and Price 1940). (e) Skull of
Edaphosaurus boanerges in dorsal, ventral and lateral views, and internal view of lower jaw (Modesto 1995).