ON THE SINUS PARANASALES OF TWO EARLY TERTIARY MAMMALS

ROY L. MOODIE Department of Anatomy, University of Illinois, Chicago

FIVE FIGURES

It is generally supposed that the accessory nasal cavities of mammals have had a long history, since they develop relatively early in the embryo (Schaeffer, '10). It will be interesting to note, in one of the two very early mammals described below, the enormous development of these cavities. Fortunate casts of t'he sinus paranasales of an oreodont (Merycochoerus) and an early bear-dog (Daphaenus) came into my possession some time sjnce. In view of the active discussion jn regard to the morphology of these cavities in the vertebrate head, it is thought that a discussion and illustration of these, the oldest known paranasal sinuses, would be of interest. One of the casts is so perfectly formed that the small bloodvessels (rami A. ethmoid- alis anterior) of the mucous membrane (mucosa sinus paranasali) lining the sinuses, are as sharp and distinct as if the sinuses were of a recently dissected animal, in which the arteries had been injected (fig. 1).

A review of the literature of the sinus paranasales is not necessary in this place, since this has been fully done by Kallius ('05), who lists titles of four hundred and twenty-one studies (1562-1905) dealing with this question. He has given further the best pictures of the casts of these cavities, as they occur in man, which have so far been published. The work of Schaeffer (,lo), Read ('OS), Dieulaf6 ('06), Osborn ('12), and the writer ('15), should be noted in this connection. So far as the writer is aware, there has never been an attempt to study systemati- cally the casts of the paranasal cavities of fossil mammals, mate- rial for which is very abundant in the various paleontological collections. It is a part of the purpose of this paper to call

135

136 ROY L. MOODIE

attention to this phase of paleontological work, which offers considerable interest in vertebrate morphology, as well as to describe the two casts above referred to. A comparison of the

Fig. 1 A photograph 01 thc sinus frontales and a part of the sinus maxillaris superior of the orrodont, Meryrochoerus, to show the rich blood supply, as intli- rated by the molds of the arteries. X 2.

results of paleontology and embryology, in regard to these cavi- ties, would be of great importance.

The casts made by von Brunn and Kallius ('05; figs. 35 and 36) of the sinuses of the human head, beautiful and completr

SINUS PARANASALES-EARLY TERTIARY MAMMALS 137

as they are, are surpassed by the casts of these cavities made by nature and preserved in fossil form. They show us the com- plete form of the cavities, the blood supply, the thickness of the limiting walls, and the relations of the sinuses to the nasal cavity and to the brain (fig. 2).

Fig. 2 Dorsal view of the casts of the h a i n and the sinus paranasales of the oreodont, Merycochoerus, from the White River Oligocene. The position of the cycs and the location of the external auditory canal renders i t probable that this aninin1 was aquatic. x :.

The oreodont cast shown in figures 1, 2, and 3, represents a member of an extinct group of artiodactyls which was so abun- dant and so characteristically American in Oligocene and Mio- cene times.

The Oreodontidae was one of the rnost characteristic of North Alrnerican artiodactyl families, and its members were exceedingly ahun-

Scott ('13) says of these animals:

138 ROY L. MOODIE

dant throughout the Upper Eocene, the wholc Oligocene and Miocene. ending their long career in the Pliocene. In distribution the fainily was exclusively North American and no trace of it has been found in any other continent. . . . . Dr. Leidy, who first discovered and named most of the genera, spoke of them as combining the characters of camel, deer and pig, and called them 'ruminating hogs' . . . .

The writer has already ('15) figured an imperfect brain cast of one species (Merycoidodon) of this group, and with the pres- ent nasal casts there is associated a splendid brain cast, which will be described at another time, in conjunction with other brain casts of Tertiary mammals.

Stnus maxilloris s u p e r s o r Stnus maxilloris s u p e r s o r

Sinus :, Sinus mnxiIIoris #nfcrlc-

0511um nlcce55orlum

i [Pors anterlorl Medul lo bblangata

Fig. 3 Lateral view of the casts of the brain and accessory nasal sinuses of Merycochocrus. X :.

The species represented by the present cast is a member of the genus Merycochoerus.' The position of the sinuses (fig. 4) is indicated in an outline of a skull figured by Matthew. The skull was slightly distorted by pressure and the brain and sinuses do not fit in an exact manner; but sufficiently well to show their location. The elongate nature of the maxillary sinus is evident, having a most unusual posterior extent.

Although the sagittal crest is fairly well developed in this species there are no sacculations of the frontal sinus in this animal, such as occurs in the pig (Sisson '14, fig. 1S0)7 and the ox (Sisson, fig. 135); although the diploic air-spaces were en-

'Matthew, W. D. 1901 Mem. Amer. Museum. Natl. Hist., vol. I , pt,. VII, p. 405.

SINUS PARANASALES-EARLY TERTL4RY MAMMALS 139

larged to diameters of three to four millimeters. Perhaps in some of the oreodonts, such as Promerycochoerus, which had a much more highly developed sagittal crest, the sagittal saccu- latjons were more highly devel.oped. The sinuses, as they are developed in the present specimen, more nearly resemble those of the sheep than those of the pig, with which the oredonts have

Fig. 4 Outline of the skull of Merycochoerus (Xftcr Alatthew) superimposed on the dranings of the casts of the accessory nasal sinuses, to s h o ~ t h r locn- tion of these cavities in the head. X +.

some affinity. A skull showing the accessory sinuses of the sheep was used for comparison with the oreodont.

The group of small cavities (figs. 1, 2 and 4) just anterior to the brain, are, doubtless, all divisions of the frontal sinus. In the frontal region of a calf, Mjhalkovics ('99; Taf. 5, fig. 24) has figured a saccuhtion of the frontal sinus, which in this fossil form has taken the shape of separate cavities. This condit,ion of the sinuses, however, is, in t,he human skull, subject to such

140 ROY L. MOODIE

an enormous range of variation that it cannot be said at present whether the small sinuses in Merycochoerus are primitive or are simply peculiar to this individual form. An extended study of casts of these animals would settle this point. None of the cavities in the fossil seem to be due to infoldings of the ethmo- turbinal, but are either divisions of the frontal or maxillary sinuses. The smaller posterior, or frontal sinuses, are sepa- rated from each other by rather thick partitions of bone (alae ossi frontzli). It is quite evident that the large cavities just anterior t o the small posterior ones, are sacculations of the maxillary sinus, which have been named (fig. 2) the sinus maxillzris superior, as in the sheep and horse. The relatively great distznce, thirty millimeters, between the most anterior one of the sinus maxillaris superior and the base of the sinus maxilleris inferior is traversed by a canal which is possibly homologous to the ostium maxillzre. This condition is particu- larly pzrdlel in the sheep, but whether it is proper to speak of this opening as the ostium mexillare, or not, is uncertain.

The divisions of the frontal sinus are small, slender, and irregulzrly developed (figs. 1 and 2), exhibiting characters which are, so fzr zs I am aware, unparalleled in modern mammals. The descending wings of the frontal bone, which separate the sinus frontales from the sinus maxillaris superior, are relatively thick as in the sheep, and from the anterior surfaces of these alae in the oreodont, as in the sheep, doubtless sprang the ethmo turbinals.

There are five sacculations of the sinus maxillaris superior. Thcy are much larger than the sincls frontalis, and their sur- faces are richly supplied with blood vessels (fig. l), which are, I suppose, branches of the A. ethmoidalis anterior. The most posterior division of this group of sinuses, is quite slender supe- riorly and deep posteriorly, forming a cavity which was flattened by the anterior part of the jugal arch. A lateral inferior divi- sion is pea-shaped. It is quite prominent and projects sharply into the maxillary bohe.

The sinus maxillaris inferior is enormously deevloped, and in the cast, takes the form of two backwardly projecting horns.

SINUS PARANASALES-EARLY TERTIARY MAMMALS 141

These sinuses occupied the entire cavity of the maxillary bone, as in the sheep, and projected posteriorly into the zygomatic arch, to a point below the orbit. The maxillary sinuses are not so many nor so complex as in the sheep, but the posterior divi- sion of the inferior group extends much further into the zygo- iiietic arch. There are several minor sacculations of the sinus maxjllaris inferior, one below the horn-like projection, Anteri- orly there is a rather large accessory sinus. Leading backward from this cavity is a canal which is possibly homologous to the ostiuin zccessorium of humm znatomy. The accessory sinus is not very prominent lzterally, but has a large expanee antero- posteriorly, extending beyond the premaxillo-maxillary suture.

The two cmals, which have been designated ostium maxillare and ostium accessorium, connect the two great divisions of the sinus maxillaris (inferior and superior) with the sinus frontalis, and for this reason I have supposed they have been properly designated. The surfaces of all the casts are richly supplied with blood vessels.

The brain cast (fig. 2) is very similar to that of the sheep, with which it has been compared in naming the gyri and sulci. The various divisions of the encephalon will be fully described later.

The other cast (fig. 5) is that of a bear-dog (Daphaenus) from the White River Oligocene of South Dakota. This cast is nct so well preserved as the oreodont, and not so much detail can be discerned, but sufficient is present to warrant a description. In order that the nature of the species may be understood, it will be necessary to say that Dz’phaenus felinus is the ancestral form of a group of bear-dogs, members of the family Canidae, which appeared in well-developed form in North America during the Oligocene and Miocene times. Their ancestors are prob- ably to be found in the Creodont family, the Miacidae, of the Uinta Eocene.

Through the Oligocene the phylum (Canidae) was carried back by the several species of Daphaenus, assuredly the ancestor of Daphaeno- don and decidedly inorc primitive in many respects. The Oligocene genus was a much smaller animal than its lower Miocene successor,

142 ROT L. MOODIE

tlic larger species hardly equalliiig a coyote; the teeth were smaller and more closely sct, but the molars were proportionately large, while the carnassials were less finished and effective shearing blades. The skull was less distinctively dog-like and had a smaller brain-case, with wry proinirient sagittal and occipital crests, a 1ongc.r cranium and shorter face; the tympanic bones wcre very sriiall and so loosely at- tached to the skull that they are rarely found, a vcry striking differ- ence from all existing dogs. The 1)aekt)one was reinarkable for the unusually large size of the luiiibar vortcbrae, ,z point of resemblance to the cats and suggesting that Daphacnus had great powers of leaping;

Fig. 5 h dorsal view of the cast of the 1)r;Lin and nas:tl cavity of Daphaenus felinus, a bear-dog from the Oligocene.

there was a long, heavy, leopard-like tail, and the caudal vertebrae were very like those of the long-tailed cats. The limbs and feet were similar in character and proportions to those of Daphaenodon, but the astragalus was less grooved for the tibia, the claws were rather more retractile and the gait was probably more plantigrade. There were so riiany cat-like features in the skeleton of Daphaenus, that the ob- server cannot but suspect that thesc resemblances indicate a community of origin, but, until the Eocene ancestors of the cats arc found, thc question of relationship must remain an opcn one (Scott, '13, p. 526-7).

The sinus frontales are present (fig. 6) in well-developed form, and are singularly like the frontal sinuses of the modern dog

X 3.

ISisson, '14, fig. 212), although the posterior superior portion of the cavities has been lost in thc fossil form. Compared to the modern dog, these cavities are smaller, measuring in the present specimen fifteen niillimetcrs in length by seven in breadth. The cavities are, however, more numerous and more elongate. There ;'re three of them to each side of the median septum, the medial one of which is the larger and longer, while that on the lateral surface is about half the size. Thin plates of bone sepa- rated these cavities. There are no evidences of the blood sup- ply, since the cast had been somewhat eroded before collection.

The sinus maxillaris is not completely preserved, since the portion of the cast which projected into the maxilla is lost. The base of this projection, which lies well forward, is present and it indicetes a more extensively developed sinus than occurs in modern dogs. There arc no superior divisions of this sinus. The impressions of the fluting of the ethmoturbirials are pre- qerved very clearly. These impressions indicate a cavum nasi of larger capacity than the modern dog possesses, and likewisc apparently \vould indicate a niuch keener sense of smell, akhough the cavum nasi is greatly narrowed a t the point c;f entrance of the olfactory nerves.

The brain cast is very well preserved, especially the ccrebellar portion. The form of the brnin is essentially dog-like, though not so richly convoluted as in the modern dog. The cat-like characters, evident in its skeletal m eke-up, have made little impress on the form of the brain. I ts form is quite distinct from that of the cats of the same period.

A study of these two casts lecds us to believe that the origin of the sinus paranzsales is to be found, not in the early mammsls but in their ancestors, and probably their remote ancestors. .Just OM- far back we would have to go to get the phylogenetic beginning of these interesting cavities is uncertain. Their na- ture in the early reptiles and amphibians is unknown. Descrip- tive paleontologv has, so far, p d no attention t o these intcr- esting phases o f the morphology o f extinct forms, 2nd it is ccr- tainly well xwrth developing. I t will not only give new life to thr wiencc itself. btit will iis-i\t in thc interpretation of many features of \-c~rtc4)rntc iiiorphoI(gy u-hic\ are r i m - obwire.

144 ROY L. MOODIE

BIBLIOGRAPHY

KALLIIJ~ , E. 1905 Sinnesorganc: Erste Abtheilung, Geruchsorgan (Organon olfactus) und Geschmacksorgan. In ‘Handbuch der dnatoniie des Menschen,’ von Karl von Bardeleben.

1910 The sinus maxillaris and its relations in the embryo, child, and adult man. See also: vol. 13, p. 183, 1912; vol. 13, p. I, 1912.

READ, EFFIE A. 1908 A contribution to the knowledge of the olfactory appa- ratus in dog, cat and man. Am. Jour. Anat., vol. 8.

DIEULAFE, LEON 1906 Morphology and embryology of the nasal fossae of vertebrates. Translated by H. W. Loeb in: Annals of Otology, Rhin- ology and Laryngology, March, June and Sept., 1908.

OSBORN, H. F. 1912 Crania of Tyrannosaurus and Allosaurus. Mein. hmer. Mus. Natl. Hist., N. S., vol. 1.

MOODIE, ROY L. 1915 A sphenoidal sinus in the Dinosaurs. Sriencc, N. S., vol. 41.

*SCOTT, W. B. 1913 A history of land mammals in the Western Hcrnisphere,

MOODIE, ROY L. 1915 A new fish brain from the coal measures of Kansas,

MIHALKOVICS, VICTOR VON 1899 Nasenhohle und Jacobson’aches Organ. Eine

SISSON, SEPTIMUS 1914 The anatomy of the domestic animals. Philadelphia.

&SCHAEFFER, J. P. Am. Jour. Anat., vol. 10.

pp. 372-382.

with a review of other fossil brains.

morphologische Studie.

p. 171, fig. 180; p. 138, fig. 135.

Jour. Comp. Neur., vol. 25.

Anat. Hefte, Bd. 11.