Samuel Wendell Williston.

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Paleozoic genera included under the above definition. Nor can we
hope to reach a very satisfactory solution of the numerous problems
till much more is known of them and especially of the later Permian
and Triassic forms included here in the same subclass.

The above definition will distinguish fairly well the Lower Permian
forms from the Middle and Upper ones, and the order Theromorpha
may be therefore accepted for the present with these limitations.
Originally the name was proposed by Cope to include not only the
Cotylosauria but all of the African genera of the order Therapsida as

Fig. 165. Skeleton and life restoration oi Dimetrodon (Theromorpha). About eight feet long.




well, and is still used often in that original sense or with the exclusion
of the Cotylosauria.

There is greater diversity among the Theromorpha as thus dis-
tinguished than among the Cotylosauria, the only constant differ-
ences from which are the perforated temporal roof, the longer neck,
and usually longer legs. Doubtless they were more active and agile
animals, and their adaptive radiation was greater. But the primitive
characters were less constant. The intertemporal bone is never

Fig. i66. Skeleton o( Edaphosaurus (Theromorpha).

present; the interparietals, tabulars, and supratemporals are always
smaller; some may be wanting, and the two former are always con-
fined to the occipital surface when present. The quadratojugal is
smaller; the lacrimal seldom extends to the nares. The teeth are
often wanting on the prevomers; the postsplenial is never present in
the mandible though there is a possibility of an additional coronoid,
the posterior one of which is always present. The humerus has an
ectepicondylar foramen only in the Edaphosauridae; the entepicon-
dylar foramen is always present. The plate-like pelvis never has a
large pubo-ischiatic or a true thyroid foramen. There are two or three
sacral vertebrae. The fifth tarsale is rarely unossified. No dermal
bones have been discovered in any member of the order, and para-
sternal ribs are known only in the PoHosauridae and Ophiacodon-





tidae. Permocarboniferous (Uppermost Carboniferous and Lower-
most Permian).


Family Sphenacodontidae (Pelycosauria). Carnivorous reptiles
of from four to eight feet in length, with long, often very long, dor-
sal spines; three sacral vertebrae.

Sphenacodon Marsh, New Mexico. Dimetrodon Cope, Texas.
Clepsydrops Cope, Illinois, Texas. Tetraceratops Matthew, Texas.
Bathygnathus Leidy, Prince Edward Island.

B. Suborder Edaphosauria

Family Edaphosauridae (Edaphosauria) . Subaquatic or terres-
trial invertebrate feeding reptiles, from six to eight feet in length.
Spines of dorsal vertebrae very long, each with transverse processes.
Skull small, short, high, with numerous palatal and coronoid conical

Edaphosaurus Cope, Texas, New Mexico. Naosaurus Cope, Texas,
New Mexico, Ohio, Germany, Russia.

C. Suborder Poliosauria

Family Poliosauridae. Lizard-like, insectivorous, four or five
feet in length. Teeth conical; spines of vertebrae short; two sacral
vertebrae. Texas and New Mexico.

Varanops Williston, Varanosaurus Broili, Poliosaurus Case,
Poecilospondylus Case, Arribasaurus Williston, Scoliomus Williston
and Case.

Family Ophiacodontidae. About six feet in length, carnivorous.
Skull narrow; teeth slender and conical or flattened; temporal open-
ing small, an upper one also in Ophiacodon; ribs holocephalous;
limbs short and stout; two sacral vertebrae. Texas and New Mexico.

Ophiacodon Marsh, Theropleura Cope, Diopeus Cope, Secodonto-
saurus Williston.

D. Suborder Caseasauria

Family Caseidae (Caseasauria) . Thickset, crawHng and probably
burrowing, invertebrate-feeding reptiles about four feet long. Skull

Fig. 169. Skeleton of Theropleura (Theromorpha), from below. One sixth natural size.







broad, short, with large pineal opening, and palate and coronoids
covered with conical teeth. Three sacral vertebrae. Texas.
Casea Williston, ? Trichasaurus Williston.

E. SUBORDER Uncertain

Family Paleohatteriidae. Small, slender reptiles. Twenty-
seven presacral vertebrae; three sacrals. Parasternal ribs present.
Intimate structure of skull unknown. Skeleton feebly ossified, prob-
ably young animals, the metacoracoids not ossified. Vertebrae
notochordal, ribs holocephalous. Lower Permian.

Paleohatteria Credner, Germany. Haptodus Gaudry, France.
? Callihrachion Boule, France.

Incertae Sedis. Mycterosaurus Williston, Glaucosaurus Williston,
Tomicosaurus Case, Metamosaurus Cope, Emholophorus Cope, Texas.
Archaeoholis Cope, Illinois. Aphelosaurus Gervais, Autun, France.
Stereorhachis Gaudry (? Sphenacodontidae) , Autun, France.

Doubtfully members of the order: Ammosaurus Huene (Triassic).
Datheosaurus .


Less primitive, more upright-walking reptiles, the propodials more
or less inclined in locomotion. Vertebrae amphicoelous, rarely noto-
chordal, dorsal intercentra unknown. Palate and Kmbs less primitive;
pelvis with larger pubo-ischiatic vacuity or thyroid opening.

As stated on a previous page, sharp distinctions between the mem-
bers of this order and the preceding one cannot be made. The primi-
tive characters common to both orders are largely included in the
Synapsida. But the very great differences presented by the later,
Triassic, forms, especially those included under the Cynodontia, dif-
ferences as great as those between any other two orders of reptiles,
render a division or divisions imperative, even though it may result,
as is so often the case in other groups of animal and vegetable life,
in the structural differences between members of the same group
being greater than those Hmiting the groups themselves. This
division, it seems to the writer, may be best made at the present
time between the Lower and Middle Permian t3rpes, that is, based
upon the stages of evolution chiefly. Perhaps when more is known


of the various and diverse forms included in both orders, a better
and more scientific division may be made on genealogical char-
acters. But such are not available at present.

The characters, as a whole, of the Therapsida are primitive, but
less so than those of the Theromorpha, and they are increasingly in-
constant. The vertebrae are known to be notochordal only in the
Dromasauria and Dinocephalia, and the intercentra are seldom if
ever persistent throughout the column; there may be as many as
seven sacral vertebrae; the boundaries of the temporal opening are
less constant; in a few words, no characters seem to be more primi-
tive than in the Theromorpha. The interparietals, when present, are
fused into a single bone, which is rarely the case in the Theromorpha.
The supratemporals are always, the postfrontals often, the quadrato-
jugals usually, absent.^ The palate and teeth undergo many changes;
the pterygoids are less free, palatal teeth are less constant. The
cleithrum is seldom present and always small, etc.

But to divide the various groups into orders seems not to solve
but rather to add to the difficulties. For that reason, perhaps it is
better at present to consider the whole group as one order, as Broom
has suggested, clearly differentiated from all others save the Thero-
morpha by the skull and pectoral girdle, and to treat its characters
under the chief divisions. Of course the distribution of some, perhaps
many, of the genera is more or less provisional, as must be the case in
any order of reptiles or other organisms until everything about them
is fully known, a result greatly to be wished, but never within the
limits of human endeavor. The classification adopted is that of
Broom and Watson in numerous publications and in Uteris, with but
few modifications.

A. Suborder Dinocephalia

Powerful reptiles from the size of a boar to that of a rhinoceros.
Skull very massive, especially in the cranial region. Temporal open-
ing bounded by the postorbital and squamosal, the jugal sometimes
intervening below. Lacrimals and quadratojugals small, the inter-
parietal and tabulars large. No dermal bones fused in midline.
Parietal opening large, opening in a protuberance or boss. Teeth

1 [The quadratojugal has recently been identified in anomodonts, gorgonopsians,
and cynodonts, by Watson. — Ed.]



more or less flattened and denticulated along their border/ not more
than eighteen in either jaw, subisodont or with a large caniniform
tooth; no teeth on palate. Prevomers, palatines, and pterygoids
united in midline, concealing the parasphenoid. Quadrate large.
Vertebrae deeply concave or notochordal. Atlanto-axis as in Dime-
trodon (Theromorpha) ; four sacral vertebrae. Ribs dichocephalous,
probably no parasternals. Shoulder girdle massive; procoracoid
barely entering glenoid fossa; a feeble clei thrum sometimes, if not

Fig. 170. Skeleton of MojcAo/>j (Dinocephalia). After Gregory. One twenty-second natural
size. Skeleton in American Museum.

always, present. Large clavicles and inter clavicle. No acromion.
Pelvis with small pubo-ischiatic vacuity. An entepicondylar fora-
men. Legs stout; epipodials and digits short; phalangeal formula
unknown, probably primitive.

Family Tapinocephalidae. Middle and Upper Permian. Del-
phinognathus Seeley, Lamiasaurus'^ Watson, Moschognathus Broom,
Mormosaurus Watson, Moschops Broom, Moschosaurus Haughton,
Phocosaurus Seeley, Pnigalion Watson, Struthiocephalus Haughton,

1 [This statement refers only to the cheek teeth; the premaxillary teeth and the first
three or four in the dentary have a long conical crown, greatly expanded posteriorly
at the base, and long roots. — Ed.]

2 [Cranium, Fig. 170. — Ed.]


Tapinocephalus Owen, Taurops Broom, Archaeosuchus Broom,
Scapanodon Broom, Eccasaurus Broom, South Africa.

Family Deuterosauridae. Upper Permian. Deuterosaurus,
Eichwald, Ural Mts.

Family Rhopalodontidae. Upper Permian. Rhopalodon, Eich-
wald, Ural Mts.

Family Titanosuchidae.^ Upper Permian. Titanosuchus Owen ,
South Africa. ''Lamiasaurus'^ [snout].

B. Suborder dromasauria

About the size of a rat. Skull short; orbits large; lacrimals con-
tinuous to septomaxilla ; temporal opening bounded by postorbital,
squamosal, and jugal; possibly the preparietal, and probably the in-
terparietal, present; parietal foramen large ; teeth isodont,subisodont,
or absent; quadra tojugals obsolete or absent; vertebrae notochordal,
intercentra unknown; two or three sacrals, probably twenty-eight
presacrals; parasternals present; no acromion and no clei thrum;
pelvis plate-like, pubic foramen large; carpus primitive, tarsus with
or without a fifth tarsale; phalangeal formula 2, 3, 3, 3, 3.

Family Galechiridae. A single row of subisodont teeth.
Middle Permian. Galechirus Broom, Galesphyrus Broom, Galepus
Broom, South Africa.

Family Galeopidae. Edentulous.

Middle Permian. Galeops Broom, South Africa.

Family Macroscelesauridae. Macroscelesaurus Haughton.

C. Suborder Anomodontia

From the size of a mouse to that of a tapir, vegetable or inver-
tebrate feeders. Large temporal opening bounded by postorbital,
squamosal, and jugal. Skull typically short and wide, the face short;
quadrates and squamosals large; lacrimals small; quadratojugals
small or obsolete.^ Preparietal usually present, in front of, or sur-

1 [A number of new genera of South African Titanosuchidae were described by Broom
in 1923 {Proc. Zool. Soc, London). — Ed.]

2 [See page 243, below. — Ed.]


rounding, parietal foramen. An interparietal and small tabulars.
Premaxillae fused and always toothless, and in life covered with
horny beak. Maxilla usually with an enlarged, permanently growing
canine, which, however, is absent in the females of some genera, and
generally with a number of small molars often irregularly arranged
in more than one series. Molars are always present on the mandible
if in the maxilla, but there is never any canine present. Prevomers
fused. A rudimentary false palate, no teeth on palatal bones.
Stapes large. Occipital condyle tripartite. Dentary, angular, and
surangular large; no coronoid. A mandibular foramen. Sclerotic
plates in orbits. Vertebrae amphicoelous; no intercentra back of
atlas; four to seven sacrals. No parasternals. Legs short and stout,,
hands and feet short; an entepicondylar foramen. Phalangeal for-
mula 2, 3, 3, 3, 3. A thyroid foramen in pelvis; ilium projecting in.
front of acetabulum. An ossified sternum. The shoulder girdle has
the coracoid and precoracoid well developed, and a distinct but short
acromion. There is a small cleithrum known in Dicynodon and
Cistecephalus , and possibly present in most other genera.

Family Dicynodontidae. Middle Permian. Dicynodon Owen,.
Pristerodon Huxley, South Africa.

Upper Permian. Tropidostoma Seeley, Diaelurodon Broom, Pro-
dicynodon Broom, Eocydops Broom, Emydops Broom, Diictodon
Broom, Emydorhynchus Broom, Emyduranus Broom, Taognathus
Broom, Cryptocynodon Seeley, Endothiodon Owen, Cistecephalus
Owen, Chelyrhynchus Haughton, South Africa, Dicynodon Owen,
South Africa and Russia.

Lower and Middle Triassic. Dicynodon Owen, Lystrosaurus Cope,.
Prolystrosaurus Haughton, Myosaurus Haughton, South Africa.

Upper Triassic. Kannemeyeria Seeley, Gordonia Newton, Geikia
Newton, Scotland. Placerias Lucas, Brachybrachium Williston,,

D. Suborder Theriodontia

Carnivorous Therapsida with more or less differentiated dentition,
including at least one pair of upper caniniform teeth; a prominent
coronoid. Vertebrae never notochordal; few or no teeth on palate
bones. No cleithrum. Manus and pes, so far as known, rarely



I. Tribe Gorgonopsia

Prefrontals and large postfrontals contiguous over orbit. A dis-
tinct preparietal in front of small parietal foramen. Temporal open-
ing bounded above by united postorbital and squamosal, below by
squamosal and jugal or squamosal only. Parietal region wide. A
single vomer (? fused prevomers). No secondary palate; an ecto-
pterygoid. No acromion on scapula; no cleithrum; coracoids rela-
tively small; a large proatlas. Phalangeal formula primitive 2, 3,

4, 5, 3-

A group intermediate, according to Broom, between the Thero-
cephalia and Anomodontia.

Middle and Upper Permian.

Family Gorgonopsidae. Gorgonops Owen, Scymnognathus Broom,
Cyniscodon Broom, Cerdognathus Broom, Scymnosaurus Broom,
Gorgonognathus Haughton, Scylacognathus Broom, Scylacops Broom,
Galesuchus Haughton, Ictidomorphus Broom, Aloposaurus Broom,
Aelurosaurus Owen, Cynodraco Owen, Tigrisuchus Owen, Arctosu-
chus Broom, Ardognathus Broom, Arc tops Watson, Theriodesmus
Seeley, Asthenognathus Broom, South Africa. Inostrancevia Ama-
litsky, Russia.

Family Ictidorhinidae. Middle and Upper Permian. Ictido-
rhinus Broom, South Africa.

Family Burnetidae. Lower Triassic. Burnetia Broom,^ South

2. Tribe Bauriasauria

A well-formed secondary palate; a median, unpaired vomer; single
occipital condyle; the pterygoids extend to quadrates; no post-
frontals; squamosal small; quadrate large; parietal foramen present
or absent; strong incisors and grinding molars; large posterior pala-
tine vacuities. No acromion on scapula.

Upper Triassic. Bauria Broom, Micro gomphodon Seeley, Melino-
don Broom, Sesamodon Broom, Aelurosuchus Broom, South Africa.

1 [Made the type of a new suborder, Burnetiamorpha, by Broom, 1923. — Ed.]


3. Tribe Therocephalia

Temporal opening large, bounded below by squamosal and jugal,
above by the parietal or the connected postorbital and squamosal.^
No quadratojugals^; quadrates small; a parietal foramen; squa-
mosals large; no preparietal. Teeth conical, four or five in pre-
maxilla; one or two large upper caniniform teeth, and five to nine
smaller ones posteriorly; no secondary palate, or a rudimentary one
(? Scaloposaurus) ; prevomers separated or fused {Scaloposaurus) ; an
interpterygoidal opening; large posterior palatine vacuities; palate
with few or no teeth; postfrontals small or absent; parietal region
usually narrow. Mandible with loose symphysis, long dentary, and
large coronoid; posterior elements not reduced. Postcranial skeleton
largely unknown.

Family Scylacosauridae. Middle and Upper Permian. Alope-
codon Broom, Pardosuchus Broom, Glanosuchus Broom, Scylacosau-
rus Broom, Pristerognathus Seeley, Ididosaurus Broom, Alopecogna-
thus Broom, Scylacorhinus Broom, South Africa.

Family Ictidosuchidae. Middle and Upper Permian. Ictido-
suchus Broom, Arnognathus Broom, Cerdodon Broom, South Africa.

Family Lycosuchidae. Middle and Upper Permian. Lycosuchus
Broom, Trochosuchus Broom, Hyaenasuchus Broom, South Africa.

Family ScALOPOSAURiDAE. Middle and Upper Permian. Scalopo-
saurus Owen, Ictidognathus Broom, Simorhinella Broom, Idicephalus
Broom, Akidnognathus Haughton, South Africa.

Family Alopecopsidae. Middle and Upper Permian. Alopecop-
sis Broom, Scymnopsis Broom, South Africa.

Family Whaitsidae. Whaitsia Haughton, South Africa.

Family doubtful. Middle and Upper Permian. Lycosaurus
Owen, Eriphostoma Broom, Lycorhinus Broom, Scymnorhinus Broom,
Alopecorhinus Broom, Scylacoides Broom, South Africa.

1 [In typical Therocephalia, as described by Broom, the postorbital and squamosal
do not connect with each other. — Ed.]

2 [See page 239, above. — Ed.]




4. Tribe Cynodontia

Especially characterized by a heter-
odont dentition, a secondary palate,
reduced posterior mandibular bones,
and two occipital condyles. Dentition
composed of from three to five incisors,
■P^ a canine, and seven to nine, rarely thir-
2 teen, molars, secodont or gompho-
g gnath or cuspidate. Temporal opening
c bounded by parietal and postorbital
t above, usually by squamosal and post-
^ orbital only below; frontals small, ex-

eluded from orbital margin by the
£? union of the prefrontal and postorbital ;
^ postf rentals absent; parietals narrow;
^ a small parietal foramen, but no pre-
< parietal bone ; tabular large ; quadrate
^ small; stapes long, stout or slender; the
S, pterygoids do not reach the quadrate;
i probably a small ectopterygoid; vomer
::^ large, unpaired. Coronoid large. A

1 small acromion on scapula; scapula
1° with reflected anterior border; no clei-
j" thrum. Fifth carpale unossified; pha-
c langeal formula 2, 3, 3, 3, 3, so far as
^ known. A thyroid foramen in pelvis.
'^ Feet imperfectly known, the digits
^ short. Vertebrae amphicoelous; no
i dorsal intercentra. Twenty-eight pre-

sacrals, four sacrals.

Family Nythosauridae. Septo-
maxillae on face; molars less cuspidate;
ft# posterior mandibular bones less re-

Middle Triassic. Nythosaurus Owen, Ictidopsis Broom, Gale-
saurus Owen, Platycraniellus v. Hoepen, South Africa.


Family Cynosuchidae. ? Middle Triassic. Cynosuchus Owen,
South Africa.

Family Cynognathidae. Septomaxillae within nares; molars
cuspidate; [posterior] mandibular bones more reduced.

Upper Triassic. Cynognathus Seeley, Lycochampsa Broom, South

Family Diademodontidae. Upper Triassic. Diademodon Seeley,
Gomphognathus Seeley, Trirachodon Seeley, South Africa. ? Upper
Triassic Cynochampsa Owen, South Africa.

5. Theriodontia (?) Incertae Sedis

Upper Triassic. ? Dromotherium Emmons, North Carolina. Tri-
holodon Seeley, Karoomys Broom, South Africa.

Lower Jurassic. Tritheledon Broom, Pachygenelus Watson, South

[May be either primitive mammals or cynodonts — too imper-
fectly known to enable one to decide. Probably each is the type of
a distinct family. — R. Broom.]




A SINGLE, large temporal opening, bounded above by the parietal,
below by the postorbital and squamosal. No dermosupraoccipitals,
tabulars, or quadratojugals. Quadrate fixed. A parietal foramen.
Neck elongated, the tail never long. Vertebrae platycoelous. Cer-
vical ribs attached exclusively to the centrum, the dorsal ribs ex-
clusively to the arch by a single head. A single, large coracoid on
each side. Girdles stout. Pelvis with large pubo-ischiatic opening,
or secondarily a thyroid foramen. No sternum. Parasternals stout.

There is still much doubt as to the derivation and genealogical
relationships of this order of reptiles, chiefly because of the structure
of the temporal region. The general characters of the skeleton are
more or less modified by aquatic adaptations. The boundaries of
the temporal region seem to be those of the upper opening of the
diapsid reptiles; and there are many who believe that it really is
the upper one, and that the order is nearest related to the Progano-
sauria. The opening, it is seen, is bounded quite like that of some
members of the Therapsida, especially the Cynodontia; and these
reptiles are confidently believed to have descended from theromor-
phous reptiles with a typical lower opening. The more general
opinion is that the Sauropterygia are related to the anomodont-Hke
reptiles. Some, however, would trace their descent directly from the
Cotylosauria; others from the Diapsida, by the loss of the lower arch.
The author believes that the first of these views is the correct one,
but in the present uncertainty they may be left in an independent

Whatever has been their origin, we must await the discovery of
their more terrestrial ancestors in the early Trias. The modifica-
tions of structure in adaptation to aquatic life are very pronounced,
even in the Nothosauria. The order is clearly divisible into two
chief groups, the Nothosauria and the Plesiosauria.


A. Suborder Nothosauria

Crawling or swimming reptiles from three to seven feet in length,
of exclusively Triassic age. Skull depressed, more or less elongate,
the orbits situated far forward, looking upward. Nares about mid-
way between the orbits and extremity. Lacrimals possibly absent.
Palate without openings, except the large internal nares, the vomers
and pterygoids meeting in the middle hne throughout. From twenty
to twenty-five cervical, twenty-five to thirty dorsal, two to five
sacral, vertebrae, and a moderately long tail. Clavicles stout, the
interclavicle vestigial. The elongated coracoids meet in the middle
line. Epipodials much shorter than propodials. Phalangeal formula
primitive, or with the loss of one phalanx in the fourth finger. Digits
probably webbed in life.

The Nothosauria were all aquatic in habit, but not exclusively so
like the plesiosaurs, the feet still retaining terrestrial characters, with
but minor aquatic adaptations. The. parasternals, like those of the
Plesiosauria, are very stout, apparently also an aquatic adaptation.
The body was never slender, though less broad than that of the
plesiosaurs, and it is not probable that they were rapid swimmers.
They doubtless lived in the shallow waters, as do the crocodiles, com-
ing frequently to land, and subsisted chiefly upon fishes and inverte-
brates, for the capture of which their slender, curved teeth were well
fitted. A pecuhar parallel adaptation to that of the contemporary
aquatic Labyrinthodontia is seen in the forward position of the eyes
in the flat skull, and also in the unusually stout clavicular girdle of

Several famiUes have been proposed, based upon minor characters
of the skull chiefly. For the present they may all be placed in a single
family, the Nothosauridae.

Family NoTHOSAURiDAE. Upper and Middle Trias. Anarosaurus
Dames, Cymatosaurus Fritsch, Dactylosaurus Glirich, Doliovertebra
Huene, Lamprosaurus Meyer, Lariosaurus Curioni, Microleptosaurus
Scuphos, Neusticosaurus Seeley, Nothosaurus Miinster, Parthano-
saurus Scuphos, Pistosaurus Meyer, Proneusticosaurus Volz, Simo-
saurus Meyer.



Marine reptiles from eight to about fifty feet in length, with
paddle-like, hyperphalangic limbs. Skull moderately broad to very
slender. Nares small, situated remote from the extremity and near
the orbits. Orbits with sclerotic plates. No distinct nasals. Internal
nares small, situated in front of the external. A pair of posterior in-
terpterygoidal openings divided by the parasphenoid always present;
other openings variable on the palate. The squamosals meet in the

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Online LibrarySamuel Wendell WillistonThe osteology of the reptiles → online text (page 14 of 18)