American Museum of Natural History

OSBORN, THE REPTILIAN SUBCLASSES DIAPSIDA AND SYNAPSIDA. 48I
with typical primitive reptilian arrangement, namely, pterygoids (surrounding interpterygoid space
and median vomers), uniting anteriorly with the prevomers, palatines short and transverse, premaxille
with three teeth. Molars with broad, flattened crowns, in lower jaws anchylosed to dentary,
teeth also on prevomers and pterygoids.
This survival of Cotylosaurian characters, in (a) palate, (b) auditory notch, (c) epiotics, (d)
sinuous sutures in the skull, together with the Cotylosaurian separation of the coracoids and procoracoids
renders it not at all surprising that this animal should have been previously placed with
the Anomodontia. Certain of the following characters, however, enumerated principally from
Broom's paper, demonstrate that it is one of the Diapsida.
VERTEBR&.-Amphiccelous, traversed by persistent notochord. Hypocentra double or paired
between atlas and axis, also between axis and cervical 3; large single or median hypocentra between
the succeeding cervicals and dorsals; hypocentra also between anterior caudals. Atlas
composed of " an arch [neurocentra] and an inferior element," also of " a distinct, well-developed
pro-atlas." Caudal chevrons beginning with the fourth caudal.
RIBs.-Apparently at sides of axis and on each succeeding vertebra, including the anterior
caudals.
ABDOMINAL RIBS.-" An inner bifurcated series, with at least three additional splint bones
passing outward from the presumed innermost element."
GIRDLEs.-Coracoid and procoracoid separate; procoracoid large, quadrate in form, but not
extending in advance of scapula. Distinct clavicles, and very long interclavicle. Ischia and
pubes continuous, that is, no puboischiadic (thyroid) foramen; pubis with large obturator foramen.
LIMBS.-Short, equal-sized; humerus with ulno- (entepi-) condylar foramen, no ectepicondylar
foramen. Carpus including intermedium, ulnare, pisiforme, carpalia 1-4 only, and apparently
two centralia carpi (bone figured as radiale by Broom [pl. I, fig. 4] appears to be a second
centrale; the true radiale was undoubtedly present). Phalangeal formula of manus 2, 3, 4, 5, 4;
the presence of 4 phalanges on D V is noteworthy (Broom, p. 23). The pes includes a tibiale
uniting with intermedium, a large fibulare, and tarsalia 1-4 only; tarsalia 4 and 5 are undoubtedly
represented in tarsale 4. The phalangeal formula of the pes was 2, 3, 4, 5,?.
AFFINITIES.-We must await the publication of Broom's memoir before the nearer affinities of
Procolophon can be determined. The chief interest lies in its primitive transitional or annectant
character between the Cotylosauria (compare pp. 456, 457) and Diapsida, especially in the skull and
shoulder girdle. In the manus and pes it is typically Diapsidan and even somewhat specialized.
V.-ORDER PROGANOSAURIA BAUR.
Mesosauria SEELEY in part.
The type of the order PROGANOSAURIA Baur' is the genus Stereoslernum
Cope2 (Figs. I5, i6a, I7, I7a, 17b, i8, i9, and PI. XL) from the Permian of Brazil;
the chief ordinal character assigned was the possession of five separate distal
tarsalia. The MESOSAURIA Seeley3 was proposed to include both the Proganosauria
of Baur and the Neusticosauria (= primitive Plesiosauria) of Seeley on
the supposition that these animals were related. This name has been adopted
by Boulenger, Furbringer and others, as well as the theory advanced by Seeley
that these animals are ancestral to the Sauropterygia. This theory is found to
' On the Pbylogenetic Arrangement of the Sauropsida. Journ. Morph., Vol I, I887, p. 103.
'A Contribution to the Vertebrate Palaeontology of Brazil. Pal. Bull. No. 40, July 30, I885; Proc. Amer. Philos.
Soc., Vol. XXIII, No. 121, 1885.
' The Mesosauria of South Africa. Quar. Journ. Geol. Soc., Vol. XLVIII, I892, pp. 586-604.