Dietary adaptations of two goat ancestors and evolutionary considerations

DIETARY ADAPTATIONS OF TWO GOAT ANCESTORS AND EVOLUTIONARY CONSIDERATIONS NIKOS SOLOUNIAS ffaeJohns Hopkins Universily School of Medicine, 725 North WolfeStr#et, Baltimore,Maryland 21205, U.SA. PresentAddress : Department of Anatomy, New York Coflegeof OstaopatbicMedicine, New YorkInstitute of Technology,Old Westbury,AT 11568, U.SM.

SONJA M.C. MOELLEKEN 7beJohns Hopkins UniversitySchoolof Medicine, 725 Nor~ wolfeStreet, Baltimore,Maryland21205, U.S.A.

ABSTRACT A comparative tooth microwear data base of twenty extant ungulates (eight browsing species, four mixed feeding species, and eight grazing species) was established and analyzed. The three dietary categories are reflected by the tooth microwear results, as browsers have more pits and fewer total scratches, and grazers have fewer pits and more total scratches. The data of the mixed feeders form bimodal distributions, consisting of a browsing group and a grazing group, which indicates that they either graze or browse. Based on the tooth microwear results, Pachytragus crassicornis, one of the extinct ancestors of modem Caprini (goats and sheep) found on the Miocene localities of Samos in Greece (7.2 - 8.5 Ma), was most likely a mixed feeder. Pachytragus laticeps was a grazer. The masticatory morphology of both Pachytragus species are similar to a few mixed feeders, such as Tragelaphus scriptus and Gazella granti. According to the local biostratigraphy at Samos, the horn core morphology of several species, and the tooth micowear data, P. laticeps most likely evolved from 1". crassicornis. In P. crassicornis, the masticatory morphology was synchronized with the dietary adaptation, in P. laticeps, which evolved rapidly, it was not. The origin of Capra may be best related to Pachytragus solignaci, which is 17 Ma. Sheep and goats may have had distinct origins prior to 17 Ma. The tribe Pseudotmgini is revived and includes Protoryx carolinae, Protoryx enanus, Pseudotragus capricornis,

Caprotragoides potwaricus, Sporadotragus parvidens, Pachytragus solignaci, Pachytragus laticeps arid Pachytragus crassicornis. ADAPTATIONSTROPHIQUESDE DRUXC H ~ S ANCESTRALESBT CONSIDI~RATIONSSUR L'I~'VOLUTION.

RI~SUMI~ Une base de donn6es comparant les micro-usures des dents de vingt et un ongul6s actuels (huit esp~ces des brouteurs, quatre esp~ces de mangeurs mixtes, et neuf esp~ces de paisseurs) a 6t6 6tablie et analys6e. Les r6sultats de la micro-usure des dents refl&ent ces trois cat6gories trophiques. Les dents des brouteurs ont plus de trouset peu de rayures longitudinales ; tandis que celles des paisseurs out peu de trous et plus de rayures longitudinales. Les donn6es sur les mangeurs mixtes m~nent/t une r6partition en deux groupes, les brouteurs et les paisseurs. D'apr~s les r6sultats de la micro-usure des dents on pent deduire que, Pachytragus crassicornis, une esp~ce anc~tre des Caprini d6couverte dam les localit6s mioc6nes de Samos en Grace (7.2-8.5 Ma), 6tait un mangeur mixte. Pachytmgus laticeps, 6tait tr~s vraisemblablement paisseur. La morphologie de mastication de deux esp~ces de Pachytragus est semblable it ceUe des mangeurs mixtes tels que Tragelapous sc@tus et Gazella granti. D'apr~s les donn6es biostrat!graphiques de Samos, 6tudes des comes de la micro-usure nous pensous que Pachytragus laticeps d6rive de Pachytragus crassicornis. La morphologie de l'appareil dentaire de Pachytragus crassicomis est adapt6e au r6gime alimentaire alors que chez Pachytragus laticeps, ~ 6volution rapide, cUe ne Pest pas. L'origine de Capra dolt 6tre cherch6e chez Pachytragus solignaci il y a 17 Ma. La brebis et la ch~we peuvent avoir des origines distinctes, ant6rieures/i 17 Ma. La tribu des Pseudotragini est r6tablie et comprend Pseudotragus capricornis, Caprotragoides potwaricus, Protoryx carolinae, Sporadotragus parvidens, Pachytragus solignac~ Pachytragus laticeps, Protoryx enanus et Pachytragus crassicomis. KEY-WORDS : TOOTH MICROWEAR, BOVIDAE, CAPRINI, MASTICATORY MORPHOLOGY, EVOLUTION, SAMOS, MIOCENE. MOTS-CL]~.S : MICRO.USURES DES DENTS, BOVIDAE, MORPHOLOGIE MASTICATOIRE, I~VOLUTION, SAMOS, MIOCI~NE.

Manuscrit d6pos6 le 14.08.1991 Manuscrit accept6 d6finitivcment le 21.10.1992

~;eobios, 1992~ n° 25, fasc. 6 | ~. 797-809 y

798

INTRODUCTION The present study will attempt to achieve two objectives. The first is to analyze tooth microwear data in order to determine the dietary adaptation of Pachytragus crassicornis and Pachytragus laticeps, which are especially interesting species since they are ancestors of the modern goats (Capra). The second is to examine the relative synchronization of masticatory morphology and behavior in terms of dietary adaptation. A general evaluation of the masticatory morphology is attempted through cranial restorations of these two Samos Pachytragus species. Since examination of tooth morphology and analysis of masticatory morphology do not result in accurate predictions of dietary adaptations on their own, tooth microwear analysis is necessary for dietary adaptation determination of an extinct species (Hayek eta/. 1992 ; Solounias & Moelleken 1992 ; Solounias & Moelleken, in press ; Solounias & Hayek, in press ; Solounias & Moelleken, in review ; Solounias et al. 1988). Scanning electron microscopy studies of microscopic tooth scars (tooth microwear analysis) shows that a correlation exists between differences in dietary adaptation and the quantity and morphology of scars on the enamel surface (Grine 1986 ; Hayek et al. 1992 ; Robson & Young 1990; Solounias et al. 1988 ; Solounias & Moelleken 1992 ; Solounias & Moelleken, in press ; Solounias & Moelleken, in review ; Teaford 1991 ; Teaford & Walker, 1984 ; Walker et al. 1978 ; Van Valkenburgh

1990).

It was necessary to use a comparative data base of tooth microwear of extant species in order to accomplish the microwear study of Pachytragus. Based on differences in vegetation consumed by ruminants, three dietary categories have been shown to exist in a natural environment browsers, mixed feeders, and grazers. Bovid browsers feed on fruit and dicotyledon foliage or tree and shrub foliage, grazers are primarily bulk and grass roughage feeders, and mixed feeders or intermediate feeders include species which consume both browsing and grazing vegetation, alternating diets seasonally or regionally (Bell 1971 ; Hofmann 1973, 1989). Morphologic. and behavioral alterations occur during the evolution of species. The relationship between behavioral and morphologic changes is not necessarily consistent, since evolution is an ongoing process. Therefore, one must realize that modern ~nimals are still evolving and consequently not all current adaptations are synchronized with environmental demands, which are constantly chan~ng as well. This also applies to extinct species. In some cases, behavior and morphology are congruent, while in others they are not. Behavior may precede morphologic change, in a classic Darwinian sense, or morphologic change may precede

behavior, as in quantum evolution. It is difficult to determine how evolution takes place through time, since not all stages of the fossil record have been preserved and discovered, and even those that have been do not record behavior directly. In order to determine the temporal relationship between behavior and morphology we have selected two extinct species of Pachytragus, of which many specimens have been found on Samos Island, Greece (Gentry 1971 ; Solounias 1981% 1981b). By analyzing the dietary adaptations of two closely related spedes from more than two different localities, more reliable results can be achieved for the dietary adaptation of Pachytragus as a genus.

METHODS For details regarding materials and methods of tooth microwear analysis, please see the previous studies : Hayek et al. 1992 ; Solounias & Hayek, in press ; Solounias & Moelleken 1992 ; Solounias & Moelleken, in press ; Solounias & MoeUeken, in review ; Solonnla.q et al. 1988. The tooth microwear data of the following extant species were used for comparisons with Pachytragus : browsers : Tragelaphus euryceros (bongo), Tragelaphus imberbis (lesser kudu), Tragelaphus strepsiceros (greater kudu), Litocranius walleri (gerenuk), Cephalophus niger (black duiker), Cephalophus dorsalis (bay duiker) ; mixed feeders : Tragelaphus scriptus (bushbuck), Capricornis sumatraensis (serow), Gazella granti (Grant's gazelle), Taurotragus oryx (eland) ; grazers : Tetracerus quadricomis (chousingaha), Connochaetes taurinus (wildebeest), Bison bison (American bison), Hippotragus niger (sable antelope), Ax/s ax~ (chital), Cervus duvauceli (swamp deer), Equus burchelli (Burchers zebra) (Table 1 and 2). We also used some unpublished microwear data for the bighorn sheep, the moose, the North American elk, and the African bush pig in general comparisons, but the final numbers cannot be included with the rest of the extant species because more data are needed before the tooth microwear analysis is complete.

P. laticeps is a species known from numerous specimens, many of which have been found at Ouarry 1 by Barnum Brown for the AMNH 1921-1924. P. laticeps does not occur in Quarry 5. P. crassicornis occurs less frequently and is primarily known from Brown's Ouarry 5, although it has been sampled elsewhere by Schlosser's excavators (Gentry 1971 ; Schlosser 1904 ; Solounias 1981% 1981b). The specimens were found within a three kilometer radius and ranged from 8.5 to 6.9 million (Weidmnnn et al. 1984). Although more than one hundred Pachytragus dentitions are known from Samos, only those attached to fairly

799

Pachytragus SPECIES

number ecar of Imqumlcy ndlvlduela

Irec~,ency sem

minimal frecFmncy

maximal frequency

average number of p4ts

pit number sam

] minimum number o1 p#tt

maldmum number otplt s

percent of pits

average number of scratches

scratch number ~ml

minimum nla~mum percent number el numbersctatcbesofscmlcbes°t s~mchos

BROWSERS

Giraffa camolopardalis Okapia johstoni Tragelaphus euryceros Tragelaphus imberbis Tragelaphosstropslceros Litocranius walled Cephalophus roger Cephalophus dorsa#s

31 14 15 21 11 24 7 6

17.9 40.1 35.1 36.7 38.4 40,8 40.1 48.3

2.0 6.7 4.8 3.2 4,6 3.9 6,2 6,6

2 6 5 15 18 17 24 29

39 53 68 66 69 66 73 64

4.1 J6.2 20.0 20.0 17.0 27.0 20.0 23.0

0.8 5.0 4.1 2.5 3,1 4.3 4,5 3.2

0 0 4 1 5 1 2 10

17 65 57 52 37 84 35 31

22.3 37.8 52.3 54.6 41.2 58.6 49.2 49.1

13.6 23.9 16,0 17.0 22.0 14.0 20.0 25.0

1,8 5.0 3.0 3.2 2.6 1,6 4.3 8,6

2 5 1 3 13 0 8 12

46 57 46 59 35 34 38 44

77.7 62.2 47.7 42.0 58.8 41.4 50.8 50.9

32 11 40 23

48.8 6O.5 52,4 61 6

3.3 6.8 3.6 4.6

2 29 I 24

89 95 40 107

14.0 24.0 200 26.0

2.1 6.9 2.7 5,1

0 0 2 O

366 70 56 97

27.0 40.6 37.0 42.8

35.0 36.0 32,0 36.0

3,4 7,9 3.2 5.3

2 9 7 3

78 95 119 80

72.2 59.2 63.0 57.5

6 26 19 4 18 18 5 27

51,3 53.5 69,2 61.3 68.2 57,1 60,0 59.6

10.1 4,2 3.9 13.4 5.3 5,3 10.7 3.9

21 22 39

82 106 107

22 31 42 62 18

110 94

103

1

33

10.0 3.9 3.9 10.5 4.7 5.6 10.2 3,6

20 12

29

42.0 43,0 55.0 55,0 41.9 54.0 58.0 49.0

74 98 96

2 0

19.7 20.0 19.7 7.5 37.6 7.0 4.3 18.2

20 13 33

135 95

3.1 1.7 3.4 35 39 1,2 1.7 1.7

1 0 0

38 13

10,0 10.0 15.0 6.0 26.3 3.0 3.0 11.0

21

101

80.3 80.0 80.3 92.5 62.4 93,0 95.7 81.6

17 10 5 2 20

68,0 553 758 119.5 467

8.7 7.7

27 34

149 90

21.8 13.2 26.4 64,0 12.7

6.5 2.3

I 1

83 26

27.1 26.0 31.2 38.9 27.3

46.2 42.1 47.4 65.5 34.0

4.6 7.4

16 16

88 89

2

935

MIXED FEEDERS

Tragelaphos scriptus Capricornissumatf aensis Gaze#a granE Taurotragos oryx GRAZERS

Tatracerus quadrioornis Connochaotes taurinLis Bison bison H~otragus n~er Kobus ellipsiryrnnus 4xis axis Corvus duvsuceli Equus burche#i EXTINCT UNKNOWNS Samos Greece

Pachytragus laticeps Q I Pachytragus crassicomis Q5 Pachytragus ? laticeps CH Pachyttagus sp, QX ~'achytragusmixed PIM sample Lower Beglia (locality 17) Tunisia Pachvtraous solionaci

72.9 74.0 68.8 61.1 72.7

Table 1 - Summary of the microwear data for extant ungulate species and Pachytragus species and populations from the Miocene of Samos in Greece. S.e.m. refers to standard error of the mean. Sommaire des donndes concernant los mi*ro-usures des dents des ongulds existants, de l'esp~ce Pachytrag, us at des populations de la IMriode Mioc#ae en Samos Grace. S.e.m. est rafdrde ~ "standard error of the mean".

MIXED FEEDERS

Number of individuals

Pits

Scratches

Tragelaphus scriptus

32

56.5 23.6

5.6 17.9

browsing grazing

Capricornis sumatraensis

ll

34.6

20.0

browsing

13.0

64.3

grazing

aazella granti

40

23.1 12.0

23.7 57.3

browsing grazing

Taurolragus oryx

23

37.1 9.1

t8.5 61.9

browsing grazing

Pachytragus crassicornis

IO

13.6

20.3

browsing

13.0

51.4

grazing

Table 2 - Summary of the mierowear data for extant mixed feeder species and Pachytragus crass~omLs from the Miocene of Samos in Greece. $ommatre des donndes concarnant lee micro-usuros des dante des e~t~¢es exirtantes des mangeurs mtxtes at du Pachytragus crassicorn~ de la pdrtode Miocene an Samos Grdce.

complete crania with horn cores cottld be used in the tooth microwear study, since P. crassicornis and P. laticeps have indistinguishable dentitions (Gentry 1971) and differentiation was necessary for the study. In order to increase our sample size, we used specimens from

two AMNH quarries within which it was known which species of Pachytragus was sampled. Table 1 includes data from all of the Pachytragus specimens studied, however, only those from Quarry 1 and Quarry 5 are figured, since the species were known in these cases. All specimens from Quarry 5 were assumed to belong to t'. crassicomis, while all specimens from Quarry 1 were assumed to belong to P. laticeps. In addition, we studied specimens from European museums, whose specific determination was possible, and a large number of isolated dentitions from PIM, SMF, MGL, and NHMW, which were only determined as Pachytragus sp. Two small samples, one from AMNH Quarry 4 and one from Quarry X, were also analyzed. We assume that the Quarry 4 sample, which is older than Quarry 1 and 5, is most likely P. laticeps. The Quarry X sample is the oldest at Samos (approximately 8.5 Ma). P. solignaci (older than 17 Ma) from the lower Beglia Formation of Tunisia (Robinson, 1972) has also been sampled from two specimens, and a preliminary dietary evaluation is attempted. Microwear scar data for each individual were categorized into fourteen variables : frequency of scars; average number of pits and scratches ; percentages of pits and scratches ; minima and maxima of the frequency of scars ; minima and maxima of the average number of pits and scratches ; standard error of the mean of frequency of scars ; standard error of the mean

800 Figure 1 - Restoration of the cranium of P a c b y t r a ~ cras$ic e r n ~ (Bovidae, Pseudotragini) from Samos Island in Greece. Restoration based on specimens A M N H 20569 from Quarry 5 and N H M W A 4780 I1 2, 1913. Scale bar is 100 millimeters. Restau-

ration du cr[tne do Pacbytraglts crasacornts (Bovidaa, Pseudotragini) de l'fla da Samos (Gr~c#). La restauration a dM basdo sur las sp4¢imens AMNH 20569 de Quarry 5 at sur NHMWA 4780 112, 1913.

/~I ~

Figure 2 - Restoration of the cranium of Yarbytragtts lattceps (Bovidae, Pseudotragini) from Samos Island in Greece. Restoration based on specimens A M N H 20609, PIM 6, PIM 15, M G L 40220 and NHMBa Samos 4. Mandible A M N H 23073 was used to determine shape of incisors and the length of the diastema. Mandibles A M N H 22883 and 22886 were used for the mandibular angle and the ascending ramus. Scale bar is 100 millimeters. Reslauration du cr~me

~

'

-~ ~

~

-

""

de Pachytragus laticeps (Bovidae, PsaudotragtnO de l'ile de Samos (ar~ca). La restauration a dM basle sur les spdamens AMHN20609, PIM 5, PIM 15, MGL 40220 at NttMBa Samos 4. Pour la ddtermination do la form, des inci.ffons at da la longuour du

',_..

I

~ .

- -~

of the average number of pits and scratches. The term scar has been been introduced by Hayek et al. (1992) to include both pits and scratches. The values for some species distribute into two discrete clusters, one group fails within the browsing domain domain, while the other distn'bntes within the grazing region of values. This concept of bimodality is exemplified in figure 4, which shows the bimodal distribution of values for G. grant/(Fig. 4). This bimodal distribution of values is characteristic of a mixed feeder, in contrast to other species classified as browsing or grazing feeders, for which the majority of individuals

~

AMNII23073. LOS mandtbules AMNIt 22883 et 22886 out dM utilisds pour ka'angle mandibtdaire at le ramus ascendanL

distribute either into the browsing or grazing regions (Solounias & Moelleken, in press). An arbitrary point of division was wade (average number of scratches 30) which differentiated the two groups into browsers and grazer, and means of each of the individual values belonging to the two groups were calcalutated and are presented in figures 5 and 6. As tables 1 and 2 show, each extant species can be identified by its unique combination of values for each variable. The data computed for Pachytragus from the AMNH Quarries 1 and 5 could, therefore, be compared visually to the respective values of the extant species of

801

tables 1 and 2. We have assumed that the extant species with values most similar to the values of the extinct species most closely approximate the dietary adaptation of the extinct species. Comparison of the values of extinct species with unknown dietary adaptation to the extant data base has resulted in satisfactory determination of the extinct species diet (Solounias & MoeUeken 1992 ; Solouniss & Moelleken, in press ; Solounias & MoeUeken, in review). Pachytragus from Samos is known from more than ten almost complete crania, over thirty partial crania, more than one hundred horn cores, maxillae, mandibles, and postcranial fragments, totalling approximately two hundred-and fifty specimens.

The cranial restoration of P. crassicomis was achieved using primarily the cranium AMNH 20569 Quarry 5 and NHMW A 4780 II 2, 1913. Numerous maxillae from Samos were also used for the masseteric restoration and evaluation. The Samos partial cranium figured by Schlosser (1904, pl. 8, fig. 11) and several mandibles were analyzed as well. Drawings of the previously mentioned specimens were superimposed and the composite was produced (Fig. 1). The P. laticeps cranial restoration was modeled mainly after cranium AMNH 20609, PIM 6, PIM 15, MGL 40220, and NHMBa Samos 4. Numerous maxillae from Samos, the Samos cranium figured by Schlosser (1904, pl. 6, fig. 8), and several AMNH mandibles were examined for masseteric restoration and evaluation. Mandible AMNH 23073 was used to determine shape of incisors and the length of the diastema. Mandibles AMNH 22883 and 22886 were used for the mandibular angle and the ascending ramus. The composite was again produced from superimposed drawings (Fig. 2). RESULTS TOOTH MICROWEAR Tooth microwear results of the extant ruminants have been presented previously, however revised data are given in tables 1 and 2 (Hayek et al. 1992 ; Solounias et al. 1988 ; Solounias & Moelleken 1992 ; Solotmias & Moelleken, in press ; Solounias & MoeUeken, in review ; Solounias & Hayek, in press). Combination of the fourteen variables and their ranges reveals that each species is unique based on these values (Table 1). Comparisons of the values of tooth microwear of Pachytragus from Samos with the twenty extant species showed that P. crassicornis (from Quarry 5) is most similar to T. quadn'cornis and C. taurinus, which are both grazers (Table 1). If a single mean were to be used for P. crassicornis, it would have been closest to the grazing

feeder values (Table 1, Fig. 3). However, examination of individual values for P. crassicornis suggests that it can best be interpreted as a mixed feeder, since values distribute (can be subdivided) into both a browsing group and a grazing group (Table 2 ; Fig. 5, 6). Thus, the values of P. orassicomis have been plotted with the mixed feeders in fig. 5 and 6. Both browsing and grazing means are plotted for each sample. The browsing individuals have a mean number of scratches of 203 and a mean number of pits of 13.6. The grazing individuals have a mean number of scratches of 51.4 and a mean number of pits of 13.0. If we consider the mixed feeder microwear data subdivided as in table 2, the grazing component of P. crassicornis is most similar to G. granti (Fig. 6) but the browsing component is unique and 03 F-

30

,

I

Ill rn

I

I1 I2

4 3ii5

20

I

r~9

Q. Ii

0 cc

I

[]

P. laticeps 6 Ii7

10 []

z LU 0 < n" LM > <

[]

P. c r a s s i c o r n i s 10

11 []

12~ 13

14 []

I8 I

I

10

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l(

15[] I

20

I

I

30

I

I

40

I

I

50

[]

I

60

A V E R A G E N U M B E R OF S C R A T C H E S Figure 3 - Tooth microwear of extant and extinct ruminants and the Burchelt's zebra summarized as two variables. Plot of the mean n u m b e r s of pits and the m e a n n u m b e r of scratches showing that they separate into two clusters with the exception of the giraffe and the c o m m o n waterbuck. T h e dark squares represent the browsers and the open squares the grazers. T h e standard errors of the m e a n s of these variables are not shown but are small. Browsers : 1

litocrantus wal!ert, 2 Cephalophus dorsalis, 3 Boocercus (Tragelaphus) euryc~us, 4 Tragelaphus imberbis, 5 Cepltalophus niger, 6 Tragelaphus Mrepsiceros, 7 0 k a p i a Johnstoni, 8 Giraffa canwlopardalis. Grazers : 9 Kobus ellipsiprymnus, 10 Bison bison, 11 Equus burchelli, 12 Tetracerus quadricornis, 13 Connochaetes taurtmts, 14 lttppolragus niger, 15 Ax/a ax/s, and 16 Cerm~ duva~wel£ The extinct species Pacbytragua latt~eps falls near Kobus ellipsitwymnu~ The plotted average is representative of individual specimens. T h e extinct species Pacbytrugus crasstcornis falls near the cluster of grazers. T h e plotted average is not representative of all the individual specimens. Micro-usuras do dents dos ruminants

axLffants on dtsparus at du z~bre de BurcheU abrdgdes an deux variables. Dtagramme du nombra moyen des trous et du nombre moyen des rayures indiquant qu'ils sont separtts en deux groupes ~ l'exeption de la girafb et du botw de l'eau commun. Les carrds ombragds reprdsentant les broutenrs at las carrd$ blancs le$ paiaseurs. Le pourcentaga des fautes de les moyennes n'est pas indtqud, mais il est ndgligeable. L'esl~ce disparue Pachytragus laticeps tombe prds da Kobus ellipsiprymnu~ La raeyenne figurant sur le diagramrae est reprdsentativa dos ~cimen$ indtvidue& L'esp~ce dispanw de Pachytragus crassicornis tombe prds du groupe des paisseurs. La raoyenne flgurant sur le dtagramme n'est pas raprdsentattve de tousles spdamens lndtvtduelL

802

120

r,,,o ILl

I

[] GRAZERS

BROWSERS I

iii

60

I

CO I"--

100

I

'

I

'

I

'

I

50 40

[]

,,=,

'

13.. 80

t,,,O

I

• T. s c r i p t u s

F,

O

60

[] O[] 0 0 0

T. s c r l p t u s [] IG. grant! C. sumatraensls

2o

2o

.i I iiIIII

iiiII

t

|I" i .

I|I

III I

i

40 G R A N T ' S G A Z E L L E INDIVIDUALS

0

'

0

10

t

I

20

i"

I

30

ml

m

oran.

P. crasslcornls

I

<

[]

\

LU i

sumatraensls

3o

0 0 0 O0[]O

40

0

T. oryx ..mC"

"

T. oryx I

,

I

I

I

40

50

60

,

70

AVERAGE NUMBER OF SCRATCHES Figure 4 - Forty specimens of Gazella granti showing the distribution of this mixed feeder into a browsing and grazing group, based on 30 scratches as a point of division. Quarante sp#cimens de Gazelle granti repr~santatif de la distribution de mangeurs mixte avec un groupe brouteurs at un groupe de paissanrs, basde sur la division de trente rayures

would fall near the giraffe (G. camelopardalis). Although the sample of extant mixed feeders is small (four species), bimodal distributions are consistently formed (Figs. 5, 6). P. crassicornis individuals differ from the four extant mixed feeders for which we have calculated tooth microwear data. While the grazing individuals clearly fall within the g r a t i n g domain, the browsing individuals fall slightly outside of the browsing domain, as the browsing P. crassicornis individuals have a lower average number of pits than one would expect for a typical browsing species.

P. laticeps (from Quarry 1) is most similar to /~ ellipsiprymnus (Table 1, Fig. 3, 7). The single mean point has been plotted in fig. 3. Unlike P. crassicornis, P. laticeps individuals cannot be separated into a browsing and a gazing group. They have a mean number of scratches of 46.2 and a mean number of pits of 21.8. Thus, they fall within the grazing cluster and are, therefore, most likely grazing feeders (Fig. 3). In figure 7, the extant species form two clusters ; a browsing cluster to the left and a gazing cluster to the fight. The sample from Quarry X, which is the oldest bone horizon at Samos (8.5 Ma), yielded more pits and scratches than any extant species. In this respect, it is more similar to the African bush pig Potarnochoems porcus (unpublished microwear data). In terms of pits, the Quarry X sample also resembles modem bighorn

Figure 5 - Tooth microwear of four extant mixed feeder ruminants can be subdivised into two domains. The pit and scratch means show two means for each species : a browsing mean represented by a dark square and a grazing mean represented by an open square. The extinct species Pacbytragus crassieornts (Bovidae, Pseudotraginae) from Samos follows this pattern with a browsing and a grazing sample. Micro-usuras de dents des ruminants existants, qui sont des mangeurs mtxCesj sa divisent an deux parties. Les donnds des It•us at des rayures tndiquant deux moyannes pour chaque asp~ce. Une moyannes de brouteurs avac un carrd ornbragd et una moyanna des paisseurs avec un carrd blanc. L "esp$ce disparue Pacbytragua crasstcornis (Bovidae, Psandotraginae) de Samos suit ce module de deux dchantillons.

sheep and the moose, which also have numerous pits (unpublished data). The moose, however, has very few scratches, unlike the Quarry X sample. In terms of scratches, the Quarry X sample is also similar to the North American elk (unpublished data). However, the elk has few pits, unlike the Quarry X sample. The sample from Quarry 4, which almost certainly consists of P. laticeps, yielded microwear similar to that of P. laticeps from Quarry 1. Although Quarry 4 is older than Quarry 1, the microwear is similar, suggesting the presence of a constant diet for at least half a million years (Q1 approximately 7.3 Ma ; Q4 definitely older than 7.5 Ma and approximately 7.7 ; Weidmarm et aL 1984, fig. 4). The mixed Pachytragus sample from PIM of Miinster has the tooth microwear of some individuals resembling P. crassicornis and others resembling 1,.. laticeps. There are crania of both species in PIM, and, thus, we almost certainly have a mixed sample which cannot be separated because the dentitions of the two species are identical. Thus, the mean number of pits and scratches falls between the browsers and the grazers as would be expected. If the averaged means of mixed feeders were

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Figure 6 - Histogram of pit and scratch means of four ruminant mixed feeders. Data show two means for each species ; a browsing mean represented by a black bar (A) and a grazing mean represented by a white bar (B). 1 Tragelaphus scriptus, 2 Taurotragus eryx, 3 Capriaornis stmsatraensis, 4 Gazelle grantL The extinct species Pachytragua crassicornts (Bovidae, Pseudotragini) from Samos follows this pattern with a browsing and a grazing group. The grazing group of P. crassiaornis is most similar to a. grantt ; its browsing group is unique. Histogramme des moyennes des trous at des rayures de quatre ruminant~ existants, qui sent des mangeurs mixtes. Les donnds monlrent deux moyennes pour chaque esp~ce : une moyenne da brotaours, reprdsenMe par une barre noire (A) at une moyenne de paisseurs reprdsentde par une barre blanc (B). L'espdce disparue Pachytragus crasstcornis (Bovkiae, Pseudolragtnae) de Samos suit ce mod~le auec un groupe brouteurs at un groupe paissours. Le groupe des paisseurs P. crasateornta est fort semblable ~ G. granti ; le groupe de brouteurs est unique.

Figure 7 - Histogram of pit and scratch means of the extant ungulate species. Data show the average number of pits (black bar) and the average number of scratches (white bar). Browsers : 1 Litocratms walleri, 2 Cephalophus dorsalis, 3 Boocemus (Tragelaphus) euryceros, 4 Tragelaphus imberbis, 5 Cephalophus niger, 6 Tragelaphus strepsiceros, 70kapia Johnstoni, 8 Giraffe camelopardali& Grazers : 9 Kobus elltpsiprymm~, 10 B/son b/son, 11 Equus burcheHi, 12 Telracerus quadricomis, 13 ¢onnochaetes taurinus , 14 Hlppotragus niger, 15 Ax/s exits and 16 Cervus duvaucel£ The extinct species Pachytragus lattceps (Bovidae, Pseudotragini) from Samos is interpreted to be a gazer and is most similar to g ellipstprynm~ The number of scratches of P. laticeps is most similar to other grazers. Histogramme dos m~annes des trous at des rayuras des ongu!ds axistants. Los donndes montrent le nombre moyen des trous (barre noire) at le nombre moyen des rayures (barre blanche). L "esp~ae disparua Pachytragus laticeps do Samos se dasse avoc los patsseurs et il est fort semblable de aelui d'autres pai~eurs.

804

plotted in fig. 3, they would also fall between the means of the browsing and grazing domains. The microwear of two P. solignaci specimens falls between the moose and the African bush pig. However the sample is small and, therefore, conclusions cannot be made about the microwear results. The diversity of the tooth microwear results within

relatively infrequently, when compared to occurrences in other gazing species. We noted no difference in bump morphology, location, or frequency between P. crassicornis and P. laticeps individuals. The mandibles of both Pachytragus characteristic of browsing individuals.

species are

Pachytragus shows that substantial differences are

DISCUSSION

detectable between and within species which can be used to determine diets of extinct populations and species and for evolutionary considerations.

THE NOMENCLATORIAL AND SYSTEMATIC PROBLEMS OF PACHYTRAGUS.

CRANIAL RESTORATION AND MASTICATORY MORPHOLOGY

Pachytragus is cranially unique, and comparisons of individual features result in similarities with Caprini, Hippotra~ni~ and other trt"oes. The restoration of P. crassicornis and P. laticeps shows crania which are in general similar to modern Capra and Hippotragus (Fig. 1, 2). In lateral view, Pachytragus most closely resembles Hippotragus niger (the sable antelope). The dentition, however, is most similar to Caprini, although sl,g~nificantly more brachydont. Pachytragus have small (reduced) premolars and simple central cavities like Caprini and Antilopini. However, the premolars of Caprini are more reduced than those of Pachytragus. Hippotra~ni have large premolars and molars with more complex enamel bands and complex central cavities, unlike Pachytragus, Caprini, and Antilopini. Although the premolars of Pachytragus are more reduced than those of Hippotra~ni~ their occlusal outlines resemble more closely those of Hippotragini t h~n Caprini, whose premolars and outlines are strongly reduced and simplified. The supraorbital foramlna are small in Pachytragus, Caprini, and Hippotragini, but large and located within depressions in Antilopini. It is also interesting to note that variations of individual crania exist within the two Pachytragus species. We have also noted that all P. laticeps specimens have similar snout shapes, while witlfm 1'. c;Tssicornis, some individuals have more massive snouts while others are more slender. The width of the brain case posterior to the horn cores varies within both of the Pachytragus species from a very narrow to a rather broad variety. The masseteric fossae of both species of Pachytragus are smooth and resemble browsing feeders and T. scriptus, which is a mixed feeder. A bump at the origin of masseter superficialis is never present, however, bumps are present at the origin of masseter profundus in some Pachytragus individuals. The bumps are somewhat elongated and cover most of the inferior border of the masseter profundus origin near the vestibule of the mouth (Fig. 1, 2). The bumps of Pachytragus occur

Gentry (1971) has discussed the nomenclatorial complexity of the Samos and Pikermi specimens assigned to Protoryx, Pachytragus and Palaeoryx. More than 14 species and 7 genera have been introduced in the literature by Andree, Gaudry, Hopwood, Major, Andree, Mecquenem, Pilgrim, Schlosser, and Wagner. The purpose of the present study, however, is not to resolve these nomenclatorial problems. Gentry (1971) suggested the presence of three distinct species (Prototyx carolinae, Pachytragus laticeps, and Pachytragus crassicornis), thereby effectively simplifying the issues. Reading Gentry (1971), it becomes clear that there is a large amount of variation within these three species. A more in depth study of these species might uncover that more species do in fact exist.

Pachytragus crassicomis (Schlosser 1904) and Pachytragus laticeps (Andree, in Pilgrim & Hopwood, 1928) are very similar to each other and to Prototyx carolinae (Major 1891), which was found at Pikermi near Athens on the Attiki Peninsula, before the discovery of the Samos bone beds. Prototyx, however, has nomenclatorial priority over Pachytragus. Solounias (1981a) synonomized the two. Thomas (1981, 1984) considers them as distinct genera. KShler (1987) confiders them congeneric. Although Protoryx and Pachytragus are very similar, we recognize them as distinct genera for the time being, in order to avoid further complicating their systematics. Additional work is necessary to elucidate the relationships of the two genera. The tribal association of Pachytragus ANDRe, 1926 placed Pachytragus in the Hippotragini on the basis of plesiomorphic characters. Gentry (1971) was the first to review these species and clearly show that the Pachytragus species were dentally most similar to modern Caprini (sheep and goats) and suggested a closer link to Caprini than to any other tribe. Solounias (1981a) suggested that Pachytragus species may be ancestral to both Caprini and I-Iippotra#ni. However, we believe, as Gentry (1971) demonstrated, that a stronger tie exists to Caprini than to Hippotra#ni. K6hler (1987) also considers Pachytragus as a close relative to the Caprini.

805 We presently believe that although ancestral to Caprini, Pachytragus should not be placed in Caprini, since Pachytragus has long metapodials, non-hollowed corn cores, narrow braincases, and brachydont dentition, ,nlike Caprini. The subfamily Pseudotraginae was suggested by Schlosser (1904) for this and other Miocene species (Pilgrim & Hopwood 1928). Although not all species listed in Pilgrim and Hopwood (1928) are valid and not all belong to such a group, it may be reasonable to keep this higher category and convert it into a tribe Pseudotragini. Such a tribe would include : Pseudotragus capricornis, Caprotragoides potwaricus, Protoryx carolinae, Sporadotragus parvidens, Pachytragus solignaci, Pachytragus laticeps and Pachytragus crassicorn/s. We propose to remove Palaeoryx pallasi and Tragoreas oryxoides from Pseudotra~ni. We believe that these two species are true ancestors of Hippotragini. We also remove the entire "Tragocems" complex of species which are Boselaphlnl. TOOTH MICROWEAR AND PALEOECOLOGY We have previously discussed the tooth microwear of extant n~minants and will, therefore, not elaborate in this paper (Hayek eta/. 1992 ; Solounias & Moelleken 1992 ; Solounias & Moelleken, in press ; Solounias & Hayek, in press ; Solounias & Moelleken, in review ; Solounlas et al. 1988). Comparisons of the tooth microwear variables with the extant species showed that P. crassicomis is most similar to mixed feeders. We assume that P. crassicomis was a special type of mixed feeder with low pit values due to certain aspects of the vegetation not sampled in modern browsers except for the giraffe. Such vegetation could be available in a forested or a woodland environment, which is in agreement with evidence from vegetation of the Miocene of Greece (Ioakim & Solounias 1985 ; Solounias & Dawson-Saunders 1988). We have shown through tooth microwear that it is possible for a Miocene r , minant species to have a low number of pits, despite consumption of food at ground level (about i to 1.50 meters from the ground), as would be the case with the medium-sized P. crassicomis. Whether or not a modern r-minant exists, which feeds near the ground and has tooth microwear similar to those obtained from P. crassicomis, remains to be seen.

P. laticeps was a grazer most similar to K. ellipsiprymnus (Fig. 3)./~ ellipsipryrnnus and the big horn sheep are the only grazers with large numbers of pits. P. laticeps clearly resembles these species and has a dietary adaptation similar to that of the sheep. The similarity in tooth microwear between the older sample from Quarry 4 and the younger one from Quarry i shows a uniform diet for several hundred thousand years. This observation suggests that some components of the

ecology at Samos were also constant for several hundred thousand years. The difference in tooth microwear between P. crassicornis and P. laticeps reinforces the assumption that they are two distinct species. In addition, the fact that P. crassicornis has a few pits while P. laticeps has many pits is interesting, since both may have either co-existed or inhabited very similar environments. If they indeed co-existed, perhaps dietary differentiation enabled coexistence without competition, in a classic ecological sense. Both species are of the same general size which suggests that different vegetations were available and eaten within the same general ecology. The results also suggest a highly variable vegetational milieu at the lower levels, which is in agreement with the chaparal model of undergrowth of the Miocene sclerophylous evergreen woodland (Axelrod 1975 ; Ioakim & Solounias, 1985 ; Solounias & DawsonSaunders, 1988). This chaparal needs to be investigated further because the majority of the Turolian herbivores and hominoids were probably exploiting it for daily sustenance. The vegetation of these Miocene woodlands must have been rich and variable because it could sustain more herbivore species than those of the modern African savannas (Quade & Solounlas, in progress). The dietary differences between P. laticeps and P. crassicornis are interesting in terms of evolution as well, since two species with identical tooth morphology consumed different types of vegetation. It becomes evident again that tooth microwear analysis is necessary to determine the dietary adaptation of other extinct species, as analysis of tooth morphology alone can be misleading. Similar situations of dietary differentiation with morphologically identical dentitions can be found among the extant deer, the gazelles, the duikers, the tragelaphines, the alcelaphines, Sus, Genetta, Cercocebus, Cercopithecus and Colobus monkeys, as well as many other species. CRANIAL RESTORATION AND MASTICATORY MORPHOLOGY While P. crassicornis and P. laticeps have very similar crania, P. crassicornis has a smaller cranium (see Gentry 1971 for more details). The restoration of the two Pachytragus species shows crania which resemble in general structure those of Capra and Hippotragus, primarily because of the shape of the horn cores and the downward bending of the braincase. Pachytragus is most similar to Hippotragus niger at the region between the orbits, horn pedicles, and posterior nasal region. Pachytragus crassicornis has shorter and more divergent horn cores with more pronounced anterior keels (Gentry 1971). Both species have dentitions which are indistinguishable from one another in morphology and size, and

806

consequently Pachytragus crassicomis has a larger dentition in relation to its cranial size (Gentry, 1971). The sample of Pachytragus is large, and individual crania show variations. Gentry (1971) pointed out that there are two varieties within each of the two Samos species: a short brained and a long brained variety. In addition, variation exists in cranial width, foramina, orbital rims, orientation of horns, and other erani~_l features. The unusual absence of females in the Samos bone beds is peculiar. These issues are pn~ling and require further explanation, since the fossils have sampled natural attritional and catastrophic events over a million years and cover a considerable ff;ographic distance. Perhaps the known specimens represent examples of male segregation (an event which happened at least six times, once for each of the six Samos bone beds). Another possibility includes the absence of sexual dimorphism, A third alternative is that P. crassicornis are the females and P. laticeps the males of a .~inglespecies. Since modern species do not show such variation, one might question whether there are in fact four or five species of Pachytragus, rather than two. At the present, separating these species would be difficult, since nomenclature is controversial and several names have been proposed for different specimens from Samos (for further details regarding nomenclatorial problems see Gentry 1971). We concur with Gentry (1971) that the variation found within the Pachytragus species is most likely due to sampling of many populations from different times and geographic locations which intercepted at Samos. The Andrianos region at Samos may have been a cross road for migrating species.

AMNH individuals of T. scriptus, L. walleri, GazeUa dama and T. eurycems. They may occur in other species as well and have been found to be more common in zoo specimens. DIETARY ADAPTATION AND MASTICATORY MORPHOLOGY Results from both tooth microwear analysis and masticatory morphology analysis show that two different adaptational strategies existed for the Samos Pachytragus species. P. crassicomis was a mixed feeder based on tooth microwear analysis and had the masticatory morphology characteristic of a mixed feeder. Thus, dietary behavior was synchronized with masticatory morphology. P. laticeps, on the other hand, was a grazing feeder with mastieatory morphology representative of a mixed fe&ler. In this case, the dietary behavior preceded the masticatory morphology. /~ ellipsiptymnus, which is ~imilar to P. laticeps in terms of tooth microwear, has extreme grazing masticatory morphology, i.e. hypsodont dentition, large masseteric fossae, and very large bumps for the masseter superficialis. P. laticeps must, therefore, have been quite stressed as a grazing feeder with mixed feeder masticatory morphology. EVOLUTION WITHIN PACHFTRAGUS AND THE ORIGIN OF CAPRINI

The details of the masseteric fossae are unlike Capra and Hippotragus but resemble Tragelaphus scdptus, Gazella granti and Gazella gutturosa, all of which are mixed feeders.

The evolutionary relationships of P. crassicornis to P. laticeps are presently unknown. According to Gentry (1971), P. laticeps probably evolved into P. crassicomis. P. crassiconis had larger teeth relative to its smaller cranium and thus was adapting to a progressively more arrid ecology (Gentry 1971). The horn cores became more keeled with progression from P. laticeps to P. crassicornis, with increasing resemblance to modern Capra (Gentry 1971). Gentry (1971) and Sondaar (1971) used the geologic age of the Samos quarries as a supporting argument, citing primary information from John Van Couvering who also worked at Samos and reported that Quarry 5 was younger thanQuarry 1 (Van Couvering & Miller 1971). However, Solounias has shown that Quarry 5 is the same age as Quarry 1 (Weidmann et al. 1984).

The bumps noted in the region of the masseter profundus origin, inferiorly and posteriorly on the maxilla, are probably the result of masseterie musculature pulling on the maxilla during feeding. It would be expected that a more pronounced bump exists when feeding on hard objects like grass. The bumps which regularly occur in grazers, such as Kobus, Bison, Capra and Hippotragus, are due to the presence of a powerful masseter superficialis (Solounias & Dawson-Saunders 1988) and are located more anteriorly and higher on the maxilla. We have found some masseter profundus bumps in a few

The oldest known Pachytragus, P. solignaci, is from the Beglia of Tunisia (17 Ma) (Robinson 1972). P. solignaci has compressed and keeled horn cores, whereas P. laticeps has more rounded and unkeeled horn cores. Using the known biostratigraphic evidence, it would be most reasonable to assume that P. solignaci evolved into P. crassicornis, which then evolved into P. laticeps. Thus, witlfm the Pachytragus lineage, there is a progressive increase in the size of the cranium, a decrease in the size of the dentition, and a reduction of keels of the horn cores. Under the new phylogeny it is unlikely that

The ma.~ticatory morphology of ruminants needs to be quantified. Solounias & Dawson-Saunders (1988) used a qualitative data base and showed by discriminant analysis that most ruminants from Pikermi and Samos had a browsing morphology. In that study, both species of Pachytragus were interpreted to be mixed feeders.

807

the Pachytragus lineage evolved directly into Capra. However, it is more likely that Capra evolved as a side branch either from P. crassicornis or from P. solignaci. At the present time, it is not possible to know the details concerning the origin of C.apra~ The fact remaln~ that P. solignaci's horn cores, which are fiat and keeled, resemble those of modern Capra more than any other Pachytragus species do. The keeled and large tooth morphology of P. soh'gnaci also resembles the horn cores and dentitions of archaic bovids such as Tragoportax; Miotragocerus and Protragocerus, probably representing the phylogenetie connection between Boselaphlnl and Pseudotra~ni-Caprinl during the early Miocene (17

Ma). The two Pachytragus species of the "Main Bone Beds Member~ of Samos may not have co-existed, but they are definitely the same relative age. Schiosser's collectors found the type of P. crassicornis at Smakia (region G figs. 5 and 6,/n Weidmann et al. 1984) which is a locality below quarries 4, 2, 1, and 5 and within the Old Mill Beds. Thus, P. crassicomis was found stratigraphically at the same levels with P. laticeps as well as below. However, the stratigraphic distribution of the two species becomes more complex since Gentry (1971) reports P. laticeps at Quarry X, which Solounias has shown to be the oldest at Samos (8.5 Ma). The differences in the faunas between Quarry 1 and 5 (both around 7.2 Ma) and between other Samos quarries are probably due to sampling rather than age. Each quarry represents accumulations during different events (e.g. flash floods after prolonged droughts or random aeeumulatious near water holes in open depressions), and, thus, not all living species may be represented in such bonebeds. The fact that no appreciable time difference has been shown to exist between P. crassicornis and P. laticeps increases the speed of evolutionary change if one of these species did in fact evolve into the other. Since this transition occurred relatively rapidly (i.e. less than 0.5 Ma) within the Main Bone Beds of the 3amos region, P. laticeps could not evolve a grazing masticatory morphology to accommodate its grazing dietary adaptation. P. crassicornis has morphology synchronized with dietary adapation perhaps because thin species has existed for a longer period of time (Old Mill Beds through Main Bone Beds) than P. laticeps (Main Bone Beds), allowing sufficient time for morphology to synchronize with dietary adaptation. These complicated issues can be elucidated somewhat upon examination of the tooth microwear analysis results. In terms of evolutionary change, it is reasonable to assume that P. crassicornis, which was a mixed feeder, gave rise to P. laticeps, which was a grazer. The evolutionary transition from a mixed feeder to a gazer agrees better with the general trends in Bovidae. Our findings show how useful tooth microwear analysis can be in providing answers to

questions regarding the direction of evolution at the specific level. Tooth mierowear analysis is indeed a new methodology in speeiation and microevolution. If the newly proposed scenario is true, some interesting observations may be made about the Pikermi species Protoo,x carolinae. The exact age of Pikermi is not known, although it has been assumed by many that it may be slightly older than the Samos bone beds (both localities are of Turolian age). It may be poss~le, however, that Pikermi is actually younger than Samos. The less abundant ungulates at Pikermi may suggest a modernization of the fauna as we approach the Pliocene. P. carolinae could be interpreted as a species which evolved from P. laticeps and as such it may be the most modern of the lineage of these species. More research is needed to explore such hypotheses. The origin of true Caprini from Pseudotragini cannot be investigated at the present because more data are needed. Pseudotragini are primitive and their degree of hypsodonty and masticatory morphology do not resemble modern Caprini. Unlike Caprini, which have short metapodials, Pseudotra~nl have long metapodials, a primitive state which suggests that Pseudotra~ni could not inhabit mountainous regions (we assume that short metapodials are an adaptation either of graviportality as in Ovibovini, Bovini and Sivatheriini, or for ascending and descending steep mountains as in Rupicaprini and Caprini). The geology at Samos and Pikermi, where the bone beds were formed, shows the presence of hilly but not mountainous terrains. However, mountains (the pre-Penteli at Pikermi and the Pre-Ambelos and Kerkis at Samos) did exist near the depositional basins (Ioakim & Solounias 1985). The horn cores of Pseudotra~ni are also solid indicating that the caprine mode of fighting had not yet evolved. The brain cases of Pseudotra~nl are not as wide as those of Caprini. Thus, the true ecologic zone of Caprini (short metapodials, hypsodont dentition, major masseteric enlargement, bumps of masseter superficialis, hollow horn cores, wide brain case) was not approached by Pseudotraglni~ In retrospect, the name Pseudotra~ni is rather appropriate because it means false goats in Greek. In our opinion, Sporadotragus parvidens and P. solignaci resemble Caprini more than the other species of Pseudotra~ni do. One of these species is older than the other and of entirely different morphology. It is possible that Caprini evolved polyphyletically. This assertion is substantiated further by the fact that Oioceros, Turcocerus, Sinotragus (=Samotragus) and Prosinotragus (=Samodorkas) may be ancestral to Ovt~ and other sheep. Pachytragus may be ancestral to Capra. These obervatious suggest that sheep and goats are not as closely related to each other as has previously been thought. They may have diverged during the early Miocene (17 Ma). If these hypotheses are valid, a

808

polyphyletic origin of Caprini is poss~le and many of the similarities between sheep and goats could be

of Miinster, SMF Seckenberg Museum of Natural History.

convergence.

Before the Pleistocene, there are n o Species which resemble modem Capra, since they reached modern levels of mastieatory morphology during the Pleistocene. The modem Cwpra has hypsodont molars, deep mandibles, very pronounced ori#n.~ and insertions of the masseter muscles on the maxilla and mandible, and a premaxillary shape which is anteriorly flattened as in mixed feeders and grazers, relative to the pointed shape found in browsers (Solouni_as et al. 1988). Goats diversified in the Pleistocene and Recent time into several species that live primarily in Eurasia and inhnbit

mountainous regions(Schaller1977). SUMMARY AND CONCLUSION

Based upon a study of cranialrestoration,masticatory morphology, and tooth microwear analysis,we propose that P. crassicomis may have evolved into P. laticeps. P. crassicomis was a mixed feeder both by tooth microwear analysis and by examination of cranial and masticatory morphology, wide P. laticeps was a grazer based upon tooth microwear analysis with morphologic features characteristic of mixed feeding individuals. Modem Capra may have arisen from P. solignaci or P. crassicomis, while modern sheep have likely arisen from entirely different species. We empha.qiTe the importance of tooth microwear analysis as an accurate methodology not only in determlnation of dietary adaptation, but also in spedation and evolutionary direction. When information is available exclusively from eranlal and masticatory morpholofty, incorrect conclusions can be made regarding an individual's dietary adaptation and consequently evolutionary direction. Results from tooth mierowear analysis complement information obtained from ernnlal restoration and mastieatory morphology and enable more accurate evolutionary statements to be made. Upon discussion of the historical and evolutionary issues, we suggest the presence of an extinct tribe of Bovidae, Pseudotragini ("false goats"), which should include the following species : Protoryx caralinae, Protogx enanus, Pseudotragus capricomis, Caprotragoides potwwicus, Sporadotragus parvidens, Pachytragus solignaci, Pachytragus laticeps and Pachytragus crassicomis. ABBREVIATIONS

Admowledgements - This study was suported by NSF grant BSR 8605172. We thank the following people for their help : P. Andrews, Th. Daflos, J. Franzen, A.W. Gentry, L. Ginsburg, E. Heizmann, G.G. Musser, MJ. Novaeek, K1. Oekentorp, G. Plodowski, P~ Robinson, F. Von R6gls M.E. Rutzmozer, F. Steininger, H. Thomas, IL Thorington, 1LH. Tedford, A. Walker and M. Weidmann.

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