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AP PE N DIX.

ART. LIII.-PrinC'lpal OAaracters Qf American .fnrassic

J)inosaUl'Sj by O. C. MARSH. Part V. With seven Plates.

IN previous articles, the writer has described the main

characters of lJ:[orosaurus, Apatosaurus, J)iplodocus, and

Atlantosaurus, the best known genera of the Sa~tropoda

hitherto found in American deposits.* The fortunate dis-

covery of a nearly complete skeleton of B1'ontosaurus has

added lIlany new points to our knowledge of this group, and

some of these are given in the present comlllunication. A

second species, equally gigantic in size, has since been found,

and its distinguishing features al'e also here recorded.

Two new genera from the same formation are noticed, and an

outline of classification of the best known American Jurassic

Dinosaurs is proposed.

Brontosaw'tts emcelsus Marsh. t

The present genus may readily be distinguished from all the

other Stt'ltropod(t by the sacrum, which is composed of five

ankylosed vertebral, none of the other genera in this group

having lllore than four. The sternum, moreover, consists of

two separate bones, which are parial, and were united to each

other on the median line apparently by cartilage only. In

many other respects the genus resembles )J£orosaurus.

The present species, aside from its immense size, is distin-

guished by the peculiar lightness of its vertebral column, the

cervical, dorsal, and sacral vertebral all having very large cavi-

ties in their centra. The first three cauda]s, also, are lightened

by excavations in their sides, a feature not before seen in this

group, and one not shared by the other species of this genus.

* This Journal, xvi, 411, Nov., 18~8, and xvii, 86, ,Tan., 1879,

t 'L'his Journal, xviii, 503, Dec., 18~9, and xix, 395, May, 1880.

418

O. O ..Alarsh-AlIle'l'lcUIt Jwrass':c DhlOsaurs.

THE SCAI'ULAR A IWll.

The scapular arch in the present species is fortunately better

known than that of any other Dinosanr hitherto discovered.

In Plates XII and XIII the various bones are represented

separately, and in figure 1 of the latter plate they are in

position. Tho scapula resembles in general form the corre-

sponding bone in MO'f'osaurus, but the shaft is longer, and the

upper end less expanded. The coracoid, 011 the other hand,

differs materially from that of KO'f'osau'f'us, and approaches

more nearly that of Apatosau'f'us, which is sub-quadrate ill

outline. In Plate XII the scapula and coracoid of the present

species are placed nearly in the same plane, and the space

between them probably represents about the amount of car-

tilage which originally separated them. Both scapulre were

found in apposition with their respective coracoids.

The two sternal bones lay side hy side between the two

coracoids, and in Plate XIII they aloe represented nearly as

found. They are sub-oval in outline, concave above, and

convex below. They are parial, and when in positioll nearly

or quite meet on the median line. Each bone is considerably

thickened in front, and shows a distinct facet for union with

the coracoid. The posterior end is thin and irregular.

THE PRESACltAL V ERTEBR.lE.

The cervical vertebrre of the present species are quite num-

erous, thirteen at least belonging in this part of the colulllll.

All are strongly opisthocrelian. The anterior cervicals are

very small in eomparison with those near the dorsal region.

From the third vertebra to the middle of the neck, the centra

increase in length and especially in bulk, but the posterior

cervicals gradually become shorter. In Plate XIV the sixth

cervical is represented, and this is typical for the anterior half

of the neck. All the anterior cervicals have coossified ribs, as

in Birds. In the posterior cervicals, the ribs become free.

The articular facet for the head of the rib rises gradually on

the side of the centrulll, the tubercular articulation remaining

on the diapophysis. None of the cervicals have a neural spine.

The neural canal is comparatively small. The centra of all

the cervicals have deep excavations ill the sides, and the trans-

verse processes are more 01' less cavernous. The posterior

cervicals which bear free ribs are remarkable for the great size

of the zygapophyses, which are here much larger than elsewhere

in the series. The anterior cervicals have several lateral cavi-

ties, while those farther back have only one lal'ge foramen in

each side of the centrum, as in the dorsals.

O. (!, Marsh-·J.IJlericClIt .Jui'assic D1~nOSallTs.

4111

The dors~tl vOI·tehne of tltis species have sllOrt centra, more

or less opisthocrelian. There is a very large cavity ill each

side which is separated from the one opposite by a thin verti-

cal partition. The neural canal is much larger than in the

cm'vicals. The anterior dorsals are distinctly opisthocreJian.

The neural spine has no prominence in. this region, bnt

rises rapidly further back. In Plate XV, figures 1 and 2, a

posterior dorsal is represented which shows the peculiar char-

acter of the vertebrfe in this part of the series. The neural

spine is greatly developed and has its summit transversely

expanded. The vertebral in this region, as in all the known

Sa1lropocla, have the peculiar diplosphenal articulation. This

is shown in figure 2. In the vertebra figured, at the base

of the neural spine, there is a strong anterior projection,

which was iuserted into the cavity between and above the

posterior zygapophyses of the vertebra in front. There appear

to be no true lumbar vertebral, as those neal' the sacrum sup-

ported free rihs of Illoderate size. These vertebral have both

faces of the centrum nearly flat or biconcave.*

THE SACRU~I.

The saCl'll1ll in the present species consists of five well

coossified vertebl'fe, and in the type specimen the centrum of

the last lumhar is firmly united with it, as shown in Plate XVI.

The striking featll1'e about this sacrum is the large general

cavity it contained. This was divided in part hy a median

longitudinal partition, as shown in Plate XV, figure 3. This

septum, however, was not continuous the whole length of the

sacrum, so that the two lateral cavities were virtually one.

This extended even into the lateral processes. The transverse

partitions formed by the ends of the respective centra were

also perforate, so that the sacrum proper was essentiaUy a

hollow cylinder. This cavernous character of the sacrum is

one of the peculiar features of the suhorder Sauropoda, and

was descrihed hy the writer, when the first species of this

group was discovered in this country.t The statement that

any of the group have the sacrum solid, like the caudals, is

evidently based on erroneous observation.

Another peculiar character of the sacmHl in the present

genus is its lofty nemal spine. This is a thin vertical plate of

bone with a thick massive summit, evidently formed by the

* Prof. Cope. mistaking the character of these vertebral in an allied foml,

described them as representing a new genus, Amphicrolias, and even a new

family, Amphicroliidro.

(Proc. Am. Phil. Soc., xvii, 24:l.) All the known

Sauropoda. however, have similar vertebral, with opisthocoolian centra in the

cervical and anterior dorsal reg-ions.

l' This Journul, xiv, 87, July, 1877.

420

O. C. Marsh-American Jurassic Dinosaurs.

union of the spines of several vertebral. In front, it shows

rugosities for the ligament uniting it to the adjoinillg vertebra,

and its posterior margin likewise mdicates a similar union with

the first caudal. In this genus, as in all the Sauropoda, each

vertebra of the sacrum supports its own transverse processes.

As shown in Plate XVI, the articulatio~l for the ilium is formed

by the coossification of the distal ends of the transverse

processes. The neural canal is much enlarged in the sacrum,

but proportionally less than in Stegosaur1ls.

THE CAUDAL Vmt'l'EllR..eE.

In tllC present species, the tln'ee vertebral next behind the

sacrulll have moderate siz:ed cavities between the base of the

nemal arch and the transverse processes. These shallow pock-

ets extend into the base of the processes, but the centra propel'

are solid. All the other caudals have the centra, processes, and

spines composed of dense bone. The fourth caudal vertebra,

represented in Plate XVII, fignres 1 and 2, is solid through-

out, and the same is true of the chevron, figl1l'es 3 and 4. The

neural spines of the anterior caudal vertebral are elevated and

massive. The summit is crllcifol'lIl in outline, due to the fonr

strong hntresses which ullite to f01'111 it.

The median caudals all have low weak spines, alld no

transverse processes. The posterior caudals are elongate, and

without spines or zygapophyses.

THE PELVIC ARCH.

The pelvic hones in the present species are shown in Plate

XVIII. The ilium represented is not perfect on its upper

margin, which extended higher originally than shown in the

fignre. Its anterior process for the support of the pubis is

llluch larger than the posterior Olle which meets the ischium.

The pubis is elongate and massive. It sends down a strong

wing for union with the iEchimn, and has in front of this the

nsual foramen. The distal end is expanded, and has on the

ilUler smface a rugose facet for union with its fellow by carti-

lage. The ischium is more slende]' than the pubis, and has its

lower end expanded for symphysial llnion with the one on the

other side. This pelvis is more like that of Atlantosaul>us

than allY other of the known genera of the Sa1wojJoda. The

three bones shown in Plate XVIII were found nearly in the

position represented.

O. 0. Marsh-American Jurassic Dinosaurs.

421

BrontosaU9'US amphts, sp. nov.

A second species of this genus is from the same hOlizon, and

is represented by the greater portion of the skeleton. In size,

the two were very nearly equal, but they may be distinguished

readily by the vertebral. In the present species, the dorsal

vertebral are less massive, the differences being especially

noticeable in the zygapophyses. The anterior caudals, more-

over, are without the cavities noticed in the type species, and

are likewise proportionally longer. The single sternal bone

found near its coracoid is thinner, and has its anterior border

less developed than the corresponding part in Brontosaurus

exoelsus. The metacarpals of the present species are more

elongate than in the other known members of the group.

I}iracodon laticeps, gen. et sp. nov.

A new Jurassic Dinosaur of moderate size is indicated by

various remains, among which are the two maxillary bones.

These are unusually slender, and peculiar in the large number

of teeth they contained. These teeth resemble in form those

of Eohinodon, Owen. They have compressed serrated crowns,

sculptured on both sides. The base of the crown is expanded,

and below this is a distinct neck, which will readily distin-

guish these teeth from any hitherto found in this country. The

teeth are implanted in distinct sockets, and there were twenty-

two in each maxillary. There is a foramen on the inner

side, just below each tooth, and some large cavities on the

outer 'side of each jaw. The teeth are very small.

The front of these jaws is edentulous, and this part curves

inward so far that the snout must have been a broad one,

almost batrachoid in form.

The following measurements indicate the size of these speci-

mens:

Entire length of maxillary bone. _ _ _ _ _ _ _ _ _ _ _ _ _ _ 170·mm

Space occupied by teeth. _____ . ___________ . _ _ _ 104'

Space occupied by eleven anterior teeth .. __ . _ _ _ 50'

Length of anterior edentulons portion ________ . _ 62'

Vertical diameter of jaw, above eleventh tooth _ _ 27'

The present species was probably ten or twelve feet in

length. The vertebral referred to this animal are biconcave,

and the other characters Imown make it probable that the

genus is most nearly related to Laosaur1J,s. The known

remains are from the Atlantosanrus beds of Wyoming.

422

O. 0. Marsh-American .Jurassic Dinosml1·s.

Hallopus, gen. nov.

The specimen described by the writei' as Nano8auru8 victor, *

proves, on investigation, to be qistinct from the type of the

genus to which it was referred, and presents some peculiar

characters. Some of these characters are as follows:

(1) There are but two vertebral in the sacrum.

(2) The femur is shorter than the tibia.

(3) The metatarsals are one-half the length of the tibia.

(4) The calcaneum is much produced backward.

The last character has not before been seen in Dinosaurs, and

indicates a foot especially adapted for leaping. The species

representing this group may be called IIallopu8 victor. The

animal was about as large as a fox. The geological horizon of

this specimen is near the base of the Atlantosaurus beus, in

Colorado, and perhaps below them.

The collection of American J Ul'assic Dinosaurs now in the

museum of Yale College includes the remains of several hU11-

dred individuals, many of them in excellent preservation. The

completeness of this series renders it valuable as a basis of

claSsification for the known American forms, and an outline of

this classification may appropriately be presented in the present

article. Most of the many genera and species represented in

this series can be readily grouped in five suborders, as given

below, two of which have already been defined by the writer.

The details of the present classification, and its application to

the Dinosauria from other formations in this country, as well

as to those of Enrope, will be reserved for a future communica-

tion. The outline of classification now proposed is as follows:

* This Journal, xiv, 255, Sept. Isn.

(1.)

(2.)

(:1. )

(4.)

(5.)

(6.)

O. 0. Marsh-American ,Furassic IJinosau1·s.

423

Order DINOSAURIA, Owen.

Suborder SAUROPODA (Lizard foot.)

Herbivorous.

Feet plantigrade, ungulate; five digits in manus and pes.

Pubes united in front by cartilage. No post-pubis.

P.·ecaudal vertebral bollow. Umb bones solid.

Family Atlalltosaurid(J3.

Genera A tlantosaurus, Apatosaurus, BrontosauJ'us, Dip-

lodocus, and Morosa1wus.

Suborder STEGOSAURIA (Plated lizard.)

Herbivorous.

Feet plantigrade, ungulate; fi ve digits in manns and peR.

Pubes free in front. Post-pubis present.

Vertebral and limb bones solid.

Family Stegosaurid(J3.

Genus Stegosaurus.

Suborder ORNITHOPOD A (Bird foot.)

Herbivorous.

Feet digitigrade; four functional digits in manns and

three in pes.

Pubes free in front. Post-pubis present.

Vertebral solid; limb bones hollow.

Family Oamptonotid(J3.

Genera Uamptonotus, Di1'acodon, Laosaurus, and Nltno-

.~attrus.

Suborder THEROPODA (Beast foot.)

Carnivorolls.

Feet digitigrade; digits with prehensile claws.

Pubes coossified in front. Post-pubis present.

Vertebral more or less cavernous; limb bones hollow.

Family Allosattrid(J3.

Genera AllosauN6s, Oreosaurus, and Labrosattffis.

S\lborder HALLOPODA (Leaping foot.)

Carnivorous?

Feet digitigrade, unguiculate; three digits in pes.

Metatarsals much elongated j calcaneum much produced

backward.

Two vertebral in sacrum. I~imb bones hollow.

Family Hallopodid(J3.

Genus Hallopus.

DINOSAURIA?

Suborder C<ELURIA (Hollow tail.)

Family Ocelurid(J3.

Genus UceluN6S.

Carnivorous?

Yale Oollege, New Haven, April 15, 1881.

AM. JOUR. SCI., Vol. XXI, ,88,.

Plate XII.

Left scapula and coracoid of Brontosaurus excelBus, Marsh; one-twelfth

natural size. n, scapJlar face of glenoid cavity; b, rugose surface for

union with coracoid; a', coracoidean part of glenoid cavity.

AM. JOUR. SCI.. Vol. XXI, 1881.

Plate XIII.

FlGURll l.-Scapular al'ch of Bronwsaul'u5 exceisus, Marsh, front view; one-

sixteenth natural size; 8, scapula; c, coracoid; g, glenoid cavity; 08,

right sternal bone; 08', left sternal bone; ct. cartilage.

FIGURE 2,-Left sternal bone, one-eighth natural Rize; a, supel'iar view; b,

inferior view; c, fnce for coracoid; d, margin next to median line:J'

e,

inner front margin; p, posterior end,

FIGURE 3.-Scapular arch of young Rhea Americana, Lath; (after Parker);

three-fonrths nntlll'al size; seen from below. Letters as above.

AM. JOU R. SCI., Vol. XXI', ,881.

Plate XIV.

1.

3.

2.

4.

FIGUlU; I. -Sixth cervical vert cura of Brontosaurus excelsus, Marsh, ~ide view.

FIGURE 2.-'£he same vertebra, fl'Ont view.

FIGURE :l.-The same, bottom view.

FIGURE 4.-Tbe same, back view.

The signification of the letters is the same in all the figures, viz: b, uall:

c, cup; d, diapophysis; j, lateral foramen; n, neural ranal: p. paJ'apophysis;

1', cervical rib; z. anterior zyg'l,popbyRis; z', posterior zygapophysis.

All the figures are one-twelfth natma! size.

AM. JOUR. SCI., Vol. XXI, 1881.

Plate XV.

a.

I.

2.

FIGURE I.-Dorsal vertebra of Brontosaurus excelsus, Marsh, side view.

FIGURE 2.-The same, back view. Both olle-twelfth natural size.

The signification of the letters in both figures is as follows: b, ball; c,

cup; d, diapophysis; j, foramen in centrum; n, neural canal; p, parapophy-

sis; s, neural spine; z. anterior zygapophysis; z', posterior zygapophysis.

FIGURE a.-Section through second vertebra of sac,'um of Brontosaw/'us

exce/sus, one-tenth natural size; c, cavity; g, surface for union with

ilium; nc, neural canal.

AM. JOUR. sel., Vol. XXI, 1881.

Plate XVI.

Sacrum of Brontnsa,ut'Us l'Xcelsus, Marsh, seen from below; one-tenth

natural size; a, first sacral vertebra; b, trallsvel'se process of fir~t vertebra;

c, transverse process of seeom] vertebra; d, transverse process of third

vertebra; e, transverse process' of fOl1l'th vertebra: j, f. f', f", foramina

between processes of sacral vertebrm: g, sl1l'face for union with ilium; I, last

lumbar vertebra: p, last sacral vertebra.

AM. JOUR. sel., Vol. XXI, ,88,.

Plate XVII.

1.

3.

4.

2.

FIGURE I.-Fourth candal verteh"a of Bmntosaurus excelsus, Marsh, side

view.

FlGURE ~.-The same, front view.

In both figures the slg'nification of the leiters is as follows: c, face for

chevron; n, neural canal; s, nenrnl spine; t, transverse process; Z, anterior

zygapopbysis; z', posterior zygapophysis,

FIGURE 3.-Chevron of Brontosaurus excelsus, side view.

FIGURE 4.-The same, front view; h, hremal canal.

All the figures are one.eighth natural size.

AM. JOUR. SCI., Vol. XXI, ,88,.

Plate XVIII.

Pelvis of Brontosau,ous excelsus, Marsh, seen from the left; one-sixteenth

natural size; a, acetabulum: j, foramen in pubis j it, ilium j is, ischium;

p, pubiso

In this diagram, the three pelvic bones are represented nearly in the

same plane.