Wiley

The prehallux is a sesamoid bone occurring in the region of the hallucial tarso‐metatarsal joint in a number of metatherian and eutherian orders and in some nonmammalian tetrapods. Within the order Primates, it occurs invariably in ceboids and Hylobates, with extreme infrequency in pongids and Homo, and is absent in other primates groups.

It has been suggested that, first, the prehallux is homologous both within and across the infraclasses Metatheria and Eutheria; second, it has functional significance in that it contributes to joint stability and is an adaptation to arboreality; third, its presence results in diagnostic features on the entocuneiform and hallucial metatarsal, so that original presence or absence can be unambiguously assessed in instances when the bone itself is not preserved; and fourth, because of presumed homology, it may be employed in the reconstruction of phylogenetic relationships.

The present study concludes that the homologous nature of the bone is open to reasonable doubt, the assumption of homology does not yield significantly more parsimonious phylogeny reconstructions than does the assumption of analogy, there are no invariant diagnostic features associated with its presence, and functional explanations currently offered are of questionable validity. Thus, the prehallux is at present of little utility in either establishing or precluding phylogenetic relationships among primates.

Recently we noted the effects of experimental diets on microscopic dental wear in the American opossum and concluded that it might prove difficult to distinguish the microwear produced by an insectivorous diet from that produced by some kinds of herbivorous ones. We also noted that wear caused by gritty diets and those containing plant opal, although they might be confused with one another, are easily distinguished from other sorts of dietary wear. Our conclusions have been challenged on the basis that possibly we did not allow sufficient time in the experiments for diagnostic wear patterns to emerge. Additional data reported here show that this is not so. Even in our n “control” animals, fed a relatively soft unabrasive diet, enough time elapsed to produce significant dental wear.

A new technique is described which for the first time allows the study of changing patterns of microscopic wear in a living animal over a period of time, thus allowing each animal to serve as its own control. A solution containing a broad‐spectrum proteolytic enzyme when applied to the teeth of an anesthetized animal removes the proteinaceous coat (pellicle) which will otherwise obscure wear scratches. Precision dental impressions can then be made which reveal the details of the pattern of microwear on the teeth.

Dental microwear is of special interest for two reasons. First, it has been proposed that specific dental microwear patterns are associated with specific diets and therefore that the diets of extinct forms may be deduced by analysis of microwear. Second, it has been suggested that the geometry of wear striations indicates the direction of masticatory movement. We tested these ideas by analyzing microwear of laboratory animals fed different diets. Twelve American opossums (Didelphis marsupialis) were fed soft cat food for 90 days. Two control animals were fed only this base diet, five animals had plant fiber added to their diet, four animals had chitin added to their diet, and one animal had fine ground pumice added to its diet (for the last 30 days of the feeding period). We examined the wear surface below the paracristid on the M₃ and M₄ of each animal by SEM. No microwear pattern differences were observed on the plant fiber‐fed, chitin‐fed, or control animal's molars. The pumice‐fed opossum had a distinct microwear pattern with many parallel striations, resembling those found on the teeth of grass‐eating hyraxes (Walker et al., 1978). These results suggest that (1) exogenous grit (this study) or plant parts containing opaline phytoliths (Walker et al., 1978) produce similar microwear patterns, and (2) the diets of extinct forms cannot always be deduced by the analysis of dental microwear. The absence of fine parallel striations on teeth of Sivapithecus examined by us suggests that grass parts were not an important part of its diet and that it avoided dietary fine grit. Furthermore, we found striations on opossum molars with deep, broad heads and shallow, narrow tails oriented in opposite directions on the the same Phase I wear facet. This suggests that the geometry of striations on Phase I wear facets does not allow one to determine the direction of masticatory movement.

Since 1930 the approach to fossil primates has undergone a twofold revolution, in more advanced taxonomic thinking, and in the growth of studies relating living primates to the interpretation of past forms. Great strides have also been made in discovering primate fossils–in 1930 there were some 58 genera of extinct primates known, and since then more than 65 new genera have been named. A major aspect of paleoprimatological research today is multidisciplinary field projects, which have accounted for a fuller understanding of dating and context. The application of functional morphology to aspects of primate evolution has allowed better understanding of primate locomotion, diet, and behavior.

The prehallux is a sesamoid bone occurring in the region of the hallucial tarso‐metatarsal joint in a number of metatherian and eutherian orders and in some nonmammalian tetrapods. Within the order Primates, it occurs invariably in ceboids and Hylobates, with extreme infrequency in pongids and Homo, and is absent in other primates groups.

It has been suggested that, first, the prehallux is homologous both within and across the infraclasses Metatheria and Eutheria; second, it has functional significance in that it contributes to joint stability and is an adaptation to arboreality; third, its presence results in diagnostic features on the entocuneiform and hallucial metatarsal, so that original presence or absence can be unambiguously assessed in instances when the bone itself is not preserved; and fourth, because of presumed homology, it may be employed in the reconstruction of phylogenetic relationships.

The present study concludes that the homologous nature of the bone is open to reasonable doubt, the assumption of homology does not yield significantly more parsimonious phylogeny reconstructions than does the assumption of analogy, there are no invariant diagnostic features associated with its presence, and functional explanations currently offered are of questionable validity. Thus, the prehallux is at present of little utility in either establishing or precluding phylogenetic relationships among primates.

Study of over 1,000 specimens representing all notharctine genera and species leads to the conclusion that current concepts about the relationships of genera within the Notharctinae are incorrect. The following describes the more probable relationships among these genera. 1) Smilodectes and Notharctus are more closely related to each other than either is to any known early Eocene notharctine. Synapomorphies linking these genera include relatively narrow upper and lower molars, a relatively low‐crowned P₄, and paraconid size reduction on M_1–3. 2) Among known Wasatchian notharctines, a clade consisting of Copelemur tutus and Cop. praetutus shares several lower molar synapomorphies with the Notharctus–Smilodectes clade, and therefore appears to form the Wasatchian sister group of Bridgerian notharctines. Synapomorphies documenting this relationship include well‐developed entoconid notches on P₄–M_2, an anteriorly placed paraconid on M_2, and a long premetacristid on M_2. 3) Copelemur and Pelycodus are independently derived from early North American Cantius.

Recent suggestions that the European adapine taxa Leptadapis priscus and Microadapis sciureus share special phylogenetic relationships with Smilodectes are rejected. The reduced (or lack of a) paraconid and morphology of the paracristid and other features identified as synapomorphies linking these adapines with Smilodectes are also characteristic of most other adapines as well (e.g., other species of Leptadapis, Adapis, Europolemur, and Anchomomys). Such traits developed independently in Smilodectes, which is clearly a notharctine on the basis of many synapomorphies and thus are not evidence of a close phylogenetic relationship between Smilodectes and L. priscus or M. sciureus.

An analysis of the relationship between oral pathology and degenerative change at the temporomandibular joint (TMJ) was undertaken on an archaeological sample of 122 adult crania from the Medieval site of Kulubnarti in Sudanese Nubia. The crania were sorted into 2 groups: those demonstrating clearly visible bony changes at the joint (TMJ+) and those without visible change (TMJ−). These groups were compared according to 1) age; 2) sex; 3) active dental pathologies (abscesses, caries, partial socket resorption); 4) tooth loss with complete socket resorption; and 5) dental attrition.

No statistically significant association was evident between degenerative change at the TMJ and age, active dental pathologes, or dental attrition; however, sex differences and posterior tooth loss with complete socket resorption revealed a significant correspondence to degenerative TMJ changes. Both of these factors agree with the clinical literature and with biomechanical models (most notably that of Hylander) based upon modern populations. Furthermore, the results support the contention that paleopathological conditions can be analyzed from a clinical and functional biomechanical perspective.