Times of crown completion and initial eruption of the same tooth do not necessarily coincide. In addition, an eruption period may be notably longer than the period within which a given tooth crown mineralized. This apparent decoupling of crown mineralization schedules and root formation and tooth eruption schedules is curious, and does not fail to contribute additional complexity to understanding the mechanisms that underlie crown mineralization schedules.
Bowen and Koch (1970) reported that the premolars, canines, and second molars all emerged at about 44 weeks in the crab-eating macaque. This monkey and the rhesus macaque shared similar emergence sequences for both the primary and adult dentitions (Bowen & Koch 1970). The time of emergence was also similar between the two macaques, and occurred later in these monkeys than it did in Chlorocebus aethiops. (Bowen & Koch 1970). Baume and Becks (1950) found that the developmental sequence of M. mulatta was consistent except for occasional “deviation in eruption order” of the premolars in a limited number of individuals. As discussed earlier, the premolars exhibit higher levels of developmental variability than do the other permanent teeth in Old World monkeys and apes. It appears that such levels of high variability remain throughout emergence as well.
Although somewhat similar between the macaques, emergence sequences differed between the deciduous and permanent dentitions of the squirrel monkey, S. sciureus (Galliari & Colillas 1985). Compared to its position in the deciduous tooth emergence sequence, the emergence of the permanent canine is delayed (Galliari & Colillas 1985). The sequence of emergence of the adult premolars is also inverted (Galliari & Colillas 1985).
Permanent dental emergence sequences of S. sciureus drawn by Schultz (1935), Serra (1952), and Long and Cooper (1968) showed that M l, M2, Hand 12 emerged first, in this order (Long & Cooper 1968). M^ emerged at least two teeth later in sequence than M3, typically after and P^ (Long &
Cooper 1968), or additionally, after P2 and C^ (Schultz 1935). In all cases
(Serra 1952, Long & Cooper 1968) in the maxilla, the canines emerged last, or, according to Schultz (1935), second last. Long and Cooper (1968) noted that "all mandibular teeth precede their maxillary counterparts in mean eruption time from as little as 1 week...to as much as 7 months”. The exception to this was P"^, which emerged two months earlier than its lower counterpart (Long & Cooper 1968). The complete sequence provided by Long and Cooper (1968) was M l M2 II 12 P^/Ms P4 P2 M^/Ps C l. Work by Galliari and Colillas (1985) supported a general permanent tooth emergence sequence of M l, M2, II, P4, P3, P2. While 12 consistently emerged after II in the mandible, the position of this tooth was quite varied in the maxilla (Galliari & Colillas 1985). M3 and C
were the last teeth to emerge, and both varied considerably in their sequence of emergence (Galliari & Colillas 1985).
In their study of the gelada (T. gelada), Swindler and Beynon (1993) determined the sequence of permanent tooth emergence as M l, II, 12, M2, [PS, P4, 0], MS, a pattern common to other cercopithecid monkeys and some fossil Theropithecus species. Swindler and Beynon’s (199S) estimates of permanent tooth emergence ages in Theropithecus based on histological data were, in years, M1=1.7; II, 12=3.0-3.2; M2=3.5-4.0; PS, P4, C=4.2-5.3; M3=6.0-6.5. Dirks and colleagues (2002) summarised that wild baboons had later emergence times (Kahumba & Eley, 1991, Phillips-Conroy & Jolly 1988, and Reed 1965, all in Dirks et al. 2002). Emergence schedules may well be varied between wild and lab-reared animals, as well (Dirks et al. 2002).
Interestingly, in Papio cynocephalus, the male canine may begin to erupt prior to any root formation (Swindler & Beynon 1993). However, root formation must occur before the canine can function at the occlusal level (Swindler & Beynon 1993).
In their studies of tooth emergence in the gibbon, both Krogman (1930) and Schultz (1935) observed an emergence sequence of M l II 12 M2 PS P4 0 MS. Schultz (1935) noted that the lower teeth typically emerged before their maxillary counterparts for all teeth except the upper and lower central incisors, which emerged simultaneously. Interestingly, although both sexes have canines of approximately equal size, these teeth tended to emerge somewhat earlier in females than in males (Schultz 1935).
Kuykendall and colleagues’ (1992) comparative study of tooth emergence of humans and chimpanzees found that emergence ages were quite variable for all tooth types in both species. Ranges of variability in Pan were 12 to 49 months for permanent teeth (Nissen & Riesen 1964) and 62 to 220 days for primary teeth (Nissen & Riesen 1945). Sequence of tooth emergence was also considerably varied. Emergence sequences provided by Nissen and Riesen (1964) were, for the maxilla. M l II [12 P3 M2] P4 C M3 and, for the mandible. M l II 12 M2 P4 P3 C M3. Dean and Wood (1981) provided identical
emergence sequences for both upper and lower jaws which were M1 11 [12 M2] P3 P4 C M3. Selenka’s (1899) emergence sequence also showed M2 and 12 emerging simultaneously. Similarly, the most common sequence found by Kuykendall et al. (1992) was M l II 12 M2 [P3 P4] C. Using mean emergence ages, these workers (Kuykendall et al. 1992) arrived at slightly different emergence sequences. These sequences for upper and lower permanent teeth were M l II 12 P4 P3 M2 C and M l II 12 M2 P4 P3 C, respectively (Kuykendall et al. 1992). In all cases. M l emerged first (Nissen & Riesen 1964, Dean & Wood 1981, Kuykendall et al. 1992). Kuykendall et al. (1992) found an associative pattern between canines and premolars, where, uniformly, the canine either emerged last or was "tied with" the emergence of a premolar. The authors suggested that the mandibular (C M2) sequence was potentially diagnostic of chimpanzees (Kuykendall et al. 1992); in humans, the canine typically emerges after M2. However, the authors conceded that “consistent pattern differences are difficult to identify” as there was much variation in sequences among individuals (Kuykendall e tal. (1992).