3 



Osteologij and the Mammalian 



Head Skeleton 



OSTEOLOGY AND HUMAN ANATOMY 



A study of the skeleton of vertebrates must necessarily 

 form the core of a comparative investigation having as one 

 of its goals an understanding of the phylogeny of these ani- 

 mals. This is so because the fossil record is made up almost 

 entirely of skeletal remains. One might argue that the study 

 of fossils is properly paleontology; this, however, would be 

 begging the point. A study of the history of structure is 

 most meaningful in terms of what can be directly observed, 

 and both fossils and living forms can be dissected. Specula- 

 tion on hypothetical stages leading to the kinds now living, 

 without proper evaluation of the fossil record, leads to the 

 same sort of meaningless esoterism that characterized the 

 Naturphilosophie of the early nineteenth century. 



Fossils are usually mere fragments of animals and are, 

 therefore, not the most satisfactory sources of information, 

 nor are they easily studied. Many students will wonder 

 what of value can be learned from them. Examination of 

 what is described as a "good" fossil vertebrate, crushed flat 

 and scattered on a slab of rock, does not arouse a feeling of 

 faith in the "scientist's" interpretation and restoration. One 

 might wonder whether the restoration is more real than the 

 idealist's theoretical "ancestral form." A detailed study of 

 skeletal anatomy will reveal to the student that much can 

 be learned from fossils and that this information is quite 

 reliable. 



Unlike the paleontologist, the comparative morphologist 

 can limit his discussion to those fossil forms which are known 

 from numerous good specimens. Such selection removes 

 much of the guesswork and supplies a relatively firm foot- 

 ing of morphological detail. Futhermore, this footing is as 

 secure as that involved in a discussion of many living forms, 

 which at present are only poorly known, because accounts 

 of them are lost in a vast and scattered literature or because 

 specimens are unavailable for consultation. Even when the 

 forms are well known, divergence of opinion and the con- 

 fusion of terminology frequently conceals the salient points. 

 Of all the parts of the skeleton, the head offers the greatest 

 rewards for study because of the many features capable of in- 



dependent variation. Despite the vast array of information 

 on the head skeleton, much of it is contradictory and con- 

 fused. The difficulties center around the concept of homo- 

 logy, which determines the terminology— homologs bear the 

 same name, homoplasts or analogs have differentiating 

 names. It is not our purpose to argue for or against any par- 

 ticular system of terminology or to evaluate the lengthy 

 arguments supporting the divergent opinions — it is enough to 

 recognize where the difficulty lies. To make meaningful 

 comparisons, it is necessary to start from a fixed set of 

 anatomical terms and to work from this to the points of 

 conflict. It is generally agreed that the basis of anatomical 

 terminology should be that applied to the human, the best 

 known chordate. 



Consistency in terminology for man is still being sought. 

 The first step in this direction began with the meeting of 

 several German anatomists in Basel in 1895. From this 

 meeting came a list of anatomical terms known as the "Basle 

 Nomina Anatomica," which was quickly adopted by many 

 countries, including the United States. This terminolo.gy 

 was refined in a revision of the list published by the Ana- 

 tomical Society of Great Britain in 1933, and in a German 

 revision, the "Jena Nomina Anatomica," issued the same 

 year. The Fifth International Congress of Anatomists, held 

 at Oxford in 1950, voted to authorize another revision, 

 which was submitted by a committee to the Sixth Congress 

 in Paris, 1955, and was accepted. This "Nomina Anatomica" 

 forms the base for present anatomical studies of man. 



In comparative study, use of the "Nomina Anatomica," 

 or N.A., has two serious drawbacks. The first is the neces- 

 sity of knowing human anatomy sufficiently well to com- 

 pare the structures of other animals with this base. Cer- 

 tainly the study of human anatomy is a large task in itself 

 and we can only propose to make a start in this direction. 

 The second problem stems from the fact that some struc- 

 tures of man are not really comparable to those of lower 

 forms. Further, the orientation terms of human anatomy 

 are hardly applicable to lower forms, i.e. posterior in the 

 human is dorsal in the tetrapods. As a result, the N.A. 

 needs to be modified, and a compromise Nomina Anatomica 

 Comparate (N.A.C.) is needed. As a beginning in this di- 



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