Anatomical

ac anterior crest (tibia)

ap adductor process (femur)

apl abductor pollicis longus m. (insertion)

BL buccolingual

BM body size

br brachialis m. (insertion)

brf brachialis flange

bt bicipital tuberosity

CC craniocaudal

cf coronoid fossa

cp coronoid process

cpt capitulum

ctf cotylar fossa (talus)

df dorsal epitrochlear fossa

DP distal phalanx

dpe deltopectoral eminence

DR digital ray (unspecified)

DR1 digital ray of thumb or big toe

DR2–5 other digital rays (manus or pes)

DV dorsoventral

ef entepicondylar foramen

ff fabellar facet (femur)

fdp flexor digitorum profundus m. (origin)

ftp fossa for tibialis posterior m. (origin)

gt greater tubercle (humerus)

gtr greater trochanter

ib interosseous border

if iliac fossa

ig intertubercular groove (sulcus)

ip iliac planum

is ischial spine

it ischial tuberosity

lc lateral condyle (femur)

le lateral epicondyle

lsr lateral supracondylar ridge

lt lesser tubercle (humerus)

ltc lateral cuneiform

ltr lesser trochanter

lw lateral “wing” of the olecranon surface of the trochlear notch (ulna)

m., mm.muscle, muscles

m1, 2mandibular molar + locus

me medial epicondyle

MC metacarpal (with or without digital ray specified)

ML mediolateral(ly)

mltr medial lip of trochlea (humerus)

mm medial malleolus

msr medial supracondylar ridge

MT metatarsal (with or without digital ray specified)

mw medial “wing” of the olecranon surface of the trochlear notch (ulna)

nv navicular

ol olecranon

olf olecranon fossa

OSTN olecranon surface of trochlear notch

PP proximal phalanx

ps patellar surface

pt peroneal trochlea (talus)

rf radial fossa

rn radial notch

sc supinator crest

scf semicondylar facet (tibia)

srp superior ramus (pubis)

st sustentaculum tali

tcj talocrural joint surface

tm teres major m. (insertion)

tn trochlear notch

tp triceps process (ulnar)

tro trochlea

Measurements

AdjMDW adjusted maximum distal width (of long bone)

APW anteroposterior

DR2L total length of second digital ray (including MC2)

DVW dorsoventral width

MaxL maximum length (of limb bone)

MLW mediolateral width (of limb bone)

MC2L maximum length of second metacarpal

MEPD posterior deviation of medial epicondyle (of humerus)

TPL total phalangeal length (i.e., finger/toe length)

Other

asl above sea level

bp before present (i.e., before radiocarbon datum, AD 1500)

L left side

PCA principal components analysis

R right side

rev. sides photographically reversed (in figures)

UF Florida Museum of Natural History, Gainesville, FL

MNHNCu Museo Nacional de Historia Natural, La Habana, Cuba

AMNHM American Museum of Natural History (Mammalogy)

USNMM United States National Museum of Natural History (Division of Mammals)

Xenothrix Amnhm 268002, 268005, and 268008

The humerus is the best represented long bone in the Xenothrix hypodigm (N  =  6; figs. 5, 6; table 4). In 1991, the only known examples of this element were immature or highly incomplete, and none seemed conclusively primate (as opposed to large rodent). Now that several humeri of the same type have been recovered, including one nearly intact specimen, allocation is no longer in doubt. AMNHM 268008, an adult right humerus lacking only the proximal articular surface (fig. 5), is obviously primatelike and can be immediately distinguished from that of the Jamaican coney (Geocapromys brownii) and most other caviomorphs by the lack of a large, flaring deltopectoral crest. The less complete specimens (fig. 6A–D) clearly represent the same species. Like AMNHM 268008, AMNHM 268002 was found at Drum Cave, but in another area (Molehole Passage). AMNHM 268005 is an unexpected addition to the hypodigm: it was found serendipitously while examining Jamaican faunal collections housed in the AMNH's Department of Mammalogy. The specimen was retrieved from a small box containing an assortment of rodent bones and and a note reading “South Side New Cave, Jamaica—Karl Koopman, Max Hecht, 1950”. All of the rest of the material in the box was found to belong to Geocapromys. As the location of the cave and its local name are not recorded in any of Koopman's notes, the only course available is to accept the box's labeling and identify the site as “New Cave”, location currently unknown.

Considering these specimens as a group, among New World monkeys the humerus of Xenothrix mcgregori may be said to have roughly the size and proportions of the equivalent element of a small individual of Cebus apella (fig. 11A–C). There are, however, notable differences. Compared to the brown capuchin, in X. mcgregori (1) the diaphysis is more robust overall and more concave posteriorly, (2) the deltopectoral eminence is larger and more projecting, (3) the crest for insertion of teres major m. is more projecting, (4) the medial epicondyle is smaller, and (5) the lateral border of the intertubercular sulcus is much less distinct. In many other regards they are similar, such as in (1) the relative size and conformation of proximal and distal articular surfaces, (2) the presence of the entepicondylar foramen, (3) the size and disposition of the tubercles, and (4) the moderate development of the brachialis flange. Several of these contrasts, which hold for other similar-sized platyrrhines such as Chiropotes satanas and Pithecia pithecia (Fleagle and Meldrum, 1988), are discussed further under Functional Considerations.

The proximal articular end, not well preserved on AMNHM 268008, is complete in AMNHM 268002 and 268005 (fig. 6A–D; see also AMNHM 259901 in MacPhee and Fleagle, 1991). In proximal aspect, the articular end appears ovate rather than rounded, much as in Cebus, and in posterior aspect its distal margin appears rather tapered, as in Cacajao and Saimiri. It is also less hemispherical overall (cf. ratio A, table 4) than that of Lagothrix or Brachyteles. The new material also helps to clarify the height relationship between the proximal articular surface and the tubercles (the scapular articulation rises above the level of the tubercles, but only slightly; fig. 6C). The tubercles themselves are as described previously, being moderately prominent and separated by the broad intertubercular groove. These features of the proximal end of the humerus are correlated in other anthropoids with limited shoulder movement outside of the extension–flexion plane (cf. Rose, 1997). The deltopectoral eminence is broad, V-shaped, and somewhat laterally displaced, so that in anterior view the lateral margin of the shaft bows slightly outward (fig. 5A), as in arboreal quadrupedal primates generally (cf. fig. 11). The specimen is robust for its length (ratios C and D, table 4), and there is no torsion of the head.

The distal articular surface (fig. 5C) bears a relatively broad capitulum; it is quasispherical and distolaterally extensive, indicating a large range of extension and rotation at the elbow joint (Meldrum et al., 1990). The capitulum and lateral epicondyle are only moderately rolled ventrally, relative to the long axis of the diaphysis, and the broad, shallow radial fossa is distinctly separated from the coronoid fossa (fig. 5A). Quadrupedal primates in which the elbow is habitually held in a semiflexed position usually exhibit this complex of features (Napier and Davis, 1959).

The lateral lip of the trochlea is indistinct in Xenothrix, and the medial lip is likewise only moderately prominent in both distal and anterior directions. A prominent medial lip is characteristic of arboreal quadrupeds such as Saimiri and Cebus, in which it functions to resist adducting torques generated by the digital and carpal flexors when the forearm is pronated during quadrupedal progression (Jenkins, 1973; Fleagle and Simons 1978). Platyrrhines employing greater frequencies of suspensory and clinging positional behaviors, such as Ateles or Pithecia (Fleagle and Meldrum, 1988), exhibit a trochlea that is more cylindrical, with a less prominent medial lip.

The medial epicondyle is relatively short, tapered, and posteriorly (dorsally) directed (~54°; see table 6). Platyrrhines with posteriorly directed medial epicondyles (e.g., Cebus, fig. 11A–C) are more quadrupedal in behavior than those in which the epicondyle projects directly medially. Functionally, posterior inclination redirects the line of pull of the digital and carpal flexors toward the dorsal trochlea (Jolly, 1967; Jenkins, 1973).

The olecranon fossa is moderately deep but is unfenestrated, whereas it often is in Cebus apella (fig. 11A). The depth and shape of the olecranon fossa are determined by the interaction of several factors, primarily the depth of the trochlear notch and the prominence of its posterior border.

As already noted, AMNHM 259906 (fig. 6E) from Long Mile Cave is clearly subadult because there is evidence that the proximal epiphysis was unfused at the time of death (MacPhee and Fleagle, 1991). However, the individual must have been close to adulthood because the distal epiphysis is completely fused in the other small humerus of similar size, AMNHM 259905 (fig. 6F).

Because of the generally poor condition of the Long Mile specimens, it is difficult to define measurements that permit useful size comparisons with the single complete humerus, AMNHM 268008. However, one comparison of relevance can be managed by reference to the entepicondylar foramen, permitting measurement of “partial shaft length” (edge of proximal epiphyseal line on diaphysis to proximal border of bridge of entepicondylar foramen). Comparing these lengths in AMNHM 259906 and 268008 (table 4) reveals that the partial shaft of the Long Mile humerus is approximately 23% shorter than the comparable region of the Drum Cave specimen, even though the former is presumably fairly close to adult size. This accords with one's general impression that the Long Mile partial humeri are more gracile than the Drum or New Cave specimens.

Paralouatta Mnhncu 76.1010–76.1013, 76.1024, and 76.1035

Although the humerus is also well represented in the Paralouatta postcranial collection (N  =  6; figs. 7–Figure 8.Figure 9.10; table 5), only two of the specimens are appreciably complete. MNHNCu 76.1010 is very nearly entire, although there are losses to the head, tubercles, and the lateral part of the distal epiphysis (capitulum and lateral epicondyle). MNHNCu 76.1035 is missing its shaft proximal to the level of the deltopectoral tuberosity as well as the lateral part of the distal epiphysis. MNHNCu 76.1011 is much smaller in all dimensions and is judged to be juvenile. The other accessioned specimens are more fragmentary, but in some cases they provide useful information on parts not represented in the two more complete specimens. All are figured here save for MNHNCu 76.1024, a badly damaged distal articular end.

The humerus of Paralouatta is not simply a relatively longer version of that of Xenothrix: the diaphysis is less posteriorly concave, and for its length it is more gracile (cf. ratios C and D, tables 4 and 5). It also displays marked contrasts in the conformation of the distal articular end (see Functional Considerations).

Although MNHNCu 76.1035 gives the impression of being considerably more robust than MNHNCu 76.1010, this is mainly due to the size of its medial and lateral supracondylar ridges. Midshaft circumference, which is taken above the termination of these lines, is very similar in the two specimens, as is minimum shaft width (table 5). The deltopectoral eminence ends in both examples in a distinctive “V” shape, presumably defined by the line of origin of the medial head of triceps m. Compared to MNHNCu 76.1010, the shaft of MNHNCu 76.1035 is relatively flatter above the level of the olecranon fossa, and the medial epicondyle is more prominent and less abraded.

The one striking contrast between these specimens that requires comment is the entepicondylar foramen, present in MNHNCu 76.1010 but not MNHNCu 76.1035. It is also clearly present in the diaphyseal specimen, MNHNCu 76.1011 (fig. 9C, D), and a slight depression just above the shallow coronoid fossa in MNHNCu 76.1013 (fig. 10A) hints at an additional occurrence. According to Fleagle (1983), the entepicondylar foramen is found in about half of the extinct platyrrhine taxa for which the humerus is known. Among living platyrrhines foramen presence can be variable even within species (e.g., Aotus, Callicebus, and Alouatta; J. Meldrum, unpubl. obs.; consistently absent in Callithrix and Leontopithecus but not Saguinus; Ford, 1986a, 1986b; Meldrum, 1990). In view of the overarching similarity of all of the humerus specimens from the monkey caves (and, not incidentally, the teeth; Horovitz and MacPhee, 1999), we conclude that, like several extant platyrrhine species, P. varonai was variable for entepicondylar foramen development, and that only one kind of primate is represented in the hypodigm.

Among humeri in the comparative set, MNHNCu 76.1010 is approximately as long as that of Alouatta seniculus and Trachypithecus pileatus (fig. 11D–F, G–I). It resembles these taxa in having a comparatively straight shaft, but is more like Erythrocebus and Theropithecus (fig. 11M–O, P–R) in exhibiting a ML narrow distal epiphysis. The overall appearance of the posterior aspect of the distal humerus is also somewhat cercopithecidlike in the lack of medial projection of the medial epicondyle, the proportions of the posterior extension of the trochlear surface, and the depth of the lateral margin of the olecranon fossa. The capitulum is wider (in anterior aspect) than the trochlea, although this is hard to measure accurately because the waist defining their respective limits is indistinct on these specimens (fig. 10A). In Alouatta (fig. 11E) and other large-bodied atelids, the posteromedial edge of the trochlea ends in a long medial lip that is aimed medially more than ventrally. In Trachypithecus, Lophocebus, Erythrocebus, and Theropithecus the homologous area is directed inferiorly (fig. 11H, K, N, Q). In Paralouatta conditions are intermediate (fig. 10A).

The olecranon fossa is notably deep in the two most complete specimens. The floor of the fossa is intact in MNHNCu 76.1010 but perforated in MNHNCu 76.1035 (which affects measurement). Whether the perforation is natural or due to postmortem breakage is difficult to say. Under high magnification, involved edges are not smooth and show a thin layer of cancellous tissue sandwiched between compact bone surfaces, suggesting that material has spalled off.

Functional Considerations

Xenothrix Amnhm 268010

The ulna from Somerville Cave, AMNHM 268010 (fig. 12; table 7), agrees in detail with AMNHM 259907, the immature specimen from Long Mile Cave described by MacPhee and Fleagle (1991: their fig. 14). Also, the trochlear notch of AMNHM 268010 articulates reasonably well with the complete humerus AMNHM 268008, which helps to corroborate the view that they belong to the same species. Because breakage occurs in approximately the same place in both ulnae, the new find adds little to what is already known. However, because AMNHM 268010 is from an adult and is less abraded than earlier finds it provides a better sense of the size and disposition of proximal joint surfaces and muscle markings. (In fig. 12, note prominent scars for supinator, brachialis, and flexor digitorum superficialis mm.)

It is difficult to estimate the degree of shaft curvature in incomplete ulnae. In the case of Xenothrix AMNHM 268010, the remaining proximal section of the posterior border (fig. 12B) is straight, but distally there is the beginning of a slight curvature, probably much as in Cebus apella (fig. 14B). It appears that the epiphysis of the triceps process of Xenothrix was small and tablike: in the new fossil there is no visible metaphyseal “line” in the cancellous bone fortuitously exposed by breakage on the medial side of the olecranon region (fig. 12B). Posteromedial slant of the process, which is characteristic of both arboreal and terrestrial Old World monkeys (to differing degrees) is not indicated (fig. 14I, J, M; table 7). A deep trochlear notch, with a sharply projecting coronoid as seen in Xenothrix, is characteristic of primates that emphasize quadrupedalism (Knussman, 1967) (cf. Cebus apella, fig. 14B).

The nonarticular areas on the trochlear surface are well marked in AMNHM 268010 (fig. 12C): They extend onto the central part of the notch medially and especially laterally, but do not extend across the notch's whole face. The radial notch is “inset” on the lateral aspect of the bone, being almost flush with it and extending onto and even slightly under the coronoid process. This feature, which has an interesting distribution, is discussed further below.

The radius of Xenothrix is not yet known.

Paralouatta Mnhncu 76.1014, 76.1016, and 76.1017

The ulnae in the hypodigm are highly incomplete (fig. 13A–I). Even so, the size contrast between both MNHNCu 76.1014 and 76.1017 on the one hand and MNHNCu 76.1016 on the other is quite noticeable, the former being larger for given linear measurements by ~20–25%. MNHNCu 76.1014 and 76.1017 are from opposite sides of the body, but in size they are very similar and quite possibly represent the same animal.

Although the posterior border of the ulna was evidently rather straight in its upper moiety, as in Xenothrix, too little is left of the shaft to ascertain whether the distal section was straight or bowed. As in Xenothrix, muscle scars around the coronoid process are well marked. Of interest is the fact that the supinator crest is displaced relatively posteriorly, as in Cebus, Lophocebus, and Theropithecus, but unlike Alouatta (or other large-bodied platyrrhines) in which the indistinct supinator crest lies closer to the interosseous crest (fig. 14).

The preserved part of the shaft in MNHNCu 76.1016 and 1017 is anteroposteriorly as wide as, or wider than, in other large-bodied platyrrhines such as Alouatta (fig. 14D–F; table 7) and Brachyteles. Mediolaterally it is compressed into a knife edge, whereas in other large-bodied platyrrhines the shaft tends to be more rounded in this dimension. This feature is possibly correlated with the extensive fossa beneath the radial notch, which recalls a similar feature seen in Macaca and some other cercopithecids in the comparative set (e.g., Erythrocebus, Theropithecus; fig. 14J–M). In these last taxa, the fossa is needed in order to give free passage to the bicipital tuberosity during movements of supination/pronation, because the tuberosity is located relatively higher on the shaft than in large-bodied platyrrhines. Xenothrix lacks this feature. In Lagothrix the ulna is compressed in this region, but it too lacks the fossa.

MNHNCu 76.1014 (fig. 13A) provides evidence that the triceps process of Paralouatta was not especially large and was built as in other platyrrhines (i.e., the process was not posteromedially retroflexed as in some cercopithecids; cf. fig. 14L).

The proximal articular areas are incomplete to some degree in all Paralouatta specimens. The trochlear notch is moderately deep, intermediate between the conditions seen in suspensory platyrrhines and terrestrial cercopithecids. As in Xenothrix, the triceps process is not medially twisted or deviated. The disposition of the nonarticular areas within the trochlear notch are hard to interpret because of damage to joint surfaces. In MNHNCu 76.1016, however, on the lateral side there is evidence that the nonarticular surface penetrated rather far into the notch. It is clear that the radial articular facet was relatively “inset” on the lateral aspect of the ulna, as in Xenothrix (cf. figs. 12, 13). In this feature, both xenotrichins agree with other platyrrhines, and in particular with the large-bodied taxa in which the elbow joints emphasize mobility (e.g., Alouatta, fig. 14F).

In Old World monkeys (fig. 14I, J, M), even in highly arboreal Colobus, the radial articular facet is more “outset,” projecting at a sharp angle out of the plane of the shaft's lateral aspect and thereby imparting a strong curve to the radial notch (Fleagle, 1983). In the comparative set, projection reaches a maximum in Theropithecus, Erythrocebus, and Macaca, in which the radial notch is divided in two by an intervening nonarticular area (e.g., fig. 14K). The “outset” condition and presence of a subdivided radial facet are evident in many ground-dwelling cercopithecids. In Trachypithecus pileatus and Colobus guereza there is only one radial facet, but in Cercocebus galeritas there are two, practically conjoined, whereas in Lophocebus albigena there are clearly two and they are quite separate (fig. 14G). This variation implies that the subdivided radial notch is not completely diagnostic of preferred substrate. The fact that platyrrhines are all quite similar for the “inset” version of this feature suggests that it is not strongly correlated with any single locomotor style.

The radius (MNHNCu 76.1015; fig. 15; table 8) attributed to Paralouatta consists only of the proximal end and a small portion of the shaft, and extensive interpretation or comparison is not warranted. Most of the articular circumference is chipped away, but there is no reason to think that it was not extensive, as in primates generally. The short neck and rather high positioning of the long, contoured bicipital tuberosity strongly recalls radii of some Old World monkeys, such as Lophocebus and Erythrocebus.

Functional Considerations

Xenothrix Amnhm 268009

AMNHM 268009, the Skeleton Cave coxal specimen (fig. 16A–C; table 9), is as incomplete as AMNHM 259904 from Long Mile Cave (fig. 16D–F) described by MacPhee and Fleagle (1991). The only noteworthy feature that is better preserved in the former is the superior ramus of the pubis. MacPhee and Fleagle (1991) inferred on the basis of the Long Mile specimen that, in the intact state, the superior ramus would have jutted at a wide angle from the coxal body; the new specimen confirms this. By superimposing images of AMNHM 2599004 (more complete ischium) on AMNHM 268009 (more complete pubis), it can be established that in Xenothrix the superior ramus departs the coxal body at somewhat less than a right angle (75–80°). Old and New World monkeys alike, especially larger species, display broadly similar angles (MacPhee and Fleagle, 1991; Meldrum, 1993; Meldrum and Kay, 1997).

In the new specimen (fig. 16A), the superior ramus is notably gracile, flat, and craniocaudally narrow. The maximum distance from the approximate center of the acetabulum to the medial end of the pubis as preserved is 27.3 mm. On the broken medial margin no rugosities or other features are present which might serve to indicate that part of the true symphyseal surface is preserved. Evidently, in the intact state the complete ramus would have been longer still. On the underside of the superior ramus there is another broken surface (arrow, fig. 16A), the site of the inferior ramus of the pubis. Although the shape of the obturator foramen cannot be inferred from the evidence at hand, it must have been relatively large, as the root of the inferior ramus lies at a considerable distance from obturator margin of the acetabular region.

The acetabulum is notably wide in both specimens. Acetabular depth is approximately one-half of acetabular diameter (ratio A, table 9), as is typical for primates (Schultz, 1969). Owing to the condition of the new specimen, in which the sciatic margin is broken away (fig. 16C), dorsal and medial acetabular wall dimensions could not be taken. However, the ventral wall is intact and its measurement resembles that of AMNHM 259904 (table 9).

MacPhee and Fleagle (1991) noted previously that the locomotor correlates of the Long Mile os coxae were indeterminate; the Skeleton Cave specimen sheds no new light on this question. However, they noted that the expanded iliac planum is consistent with slothlike slow quadrupedalism or climbing, as is the gracile and apparently elongated pubic ramus.

Paralouatta Mnhncu 76.1036

Although abrasion has affected most edges of this specimen, reducing the accuracy of measurements, it is clear that the os coxae was large and robustly built in the Cuban monkey, with wide iliac surfaces and a massive dorsal acetabular wall (fig. 17; table 9). The pubis is shorn off at its acetabular root, and only a small portion of the ischium is preserved. The iliac portion includes most of the sacral articular surface, but nothing remains of its rostral margin. The broad iliac blade is reflected laterally in such a way that the dorsal surface is noticeably concave, as in large Ateles belzebuth or Lagothrix lagotricha. The ischium is broad and appears to have supported a wide and perhaps slightly laterally flaring tuberosity. Nothing, however, in the anatomy of the part preserved suggests that the tuberosity was built out into a platform, as in Old World monkeys. The acetabulum is conspicuously large and slightly more downward-facing than in living large-bodied platyrrhines.

The longest dimension, as preserved, is 115 mm. However, the proportions of the os coxae suggest that it might have exceeded 140 mm in maximum length when intact, which is within the range of coxal lengths found in the largest living platyrrhines.

Functional Considerations

Xenothrix Amnhm 268003

The highly distinctive femur of Xenothrix was originally described on the basis of AMNHM 259900, a relatively intact specimen from Long Mile Cave (MacPhee and Fleagle, 1991; fig. 18; table 10). This specimen presents an odd combination of features: some are primatelike, such as large greater and lesser trochanters, but others are rare or absent in other members of the order, such as the “fourth” trochanter or adductor process on the posterior aspect of the bone. As with the os coxae, functionally significant features of the femur suggests that Xenothrix was a slow, quadrupedal climber with no obvious adaptations for more energetic forms of locomotion such as leaping.

The Somerville specimen (AMNHM 268003; fig. 19) is much less complete, although for the parts represented it is actually in a better state of preservation. The femur was found in a small pile of bones on the surface of an exposed ledge on the north side of the large pit fall that represents the entrance to the cave (for a plan, see Fincham, 1997). It is thus possibly very recent in age. No additional primate elements were found among these other bones, which seem to have fallen or weathered out of openings (?owl roosts) situated about a meter above the ledge.

The shaft of the new specimen is somewhat more gracile than that of AMNHM 259900. This feature tends to emphasize the relative bulk of the condyles (fig. 19), which are essentially intact. As noted by MacPhee and Fleagle (1991) on the basis of the less complete Long Mile specimen, the femoral condyles of Xenothrix are large, mediolaterally compressed, and define between them a broad, rather flat patellar surface. The area giving rise to the adductor process seen in AMNHM 259900 is not preserved.

For completeness, it may be briefly noted that no additional examples of femora resembling those from Coco Ree Cave (UF 40097) and Sheep Pen (UF 58350) in central and northern Jamaica have been found in recent years (see Ford and Morgan, 1986; Ford 1990; see also MacPhee and Fleagle, 1991: their fig. 2). These specimens—both poorly preserved proximal femora—are of considerable interest because Ford described them as possessing primatelike features. MacPhee and Fleagle (1991) concluded that they differed too greatly from AMNHM 259900 to warrant their placement in the same hypodigm, but no progress has been made in finding a better attribution for them.

Paralouatta Mnhncu 76.1018 and 76.1019

Proximal femur MNHNCu 76.1018 is badly battered (fig. 20; table 10). Fresh breaks on the specimen's shaft indicate that the bone was probably broken during the course of recovery, although no diaphyseal fragments in the collection can be precisely fitted to the specimen. The head and greater trochanter are missing, evidently because they were still in the epiphyseal stage at the time of death. The lesser trochanter is present but damaged. The shaft quickly tapers distal to the position of the trochanters, as in platyrrhines generally, but too little is left to allow a good estimate of robusticity or midshaft circumference. The femoral head of Paralouatta was obviously large and spherical, judging from the dimensions of the acetabular cup in MNHNCu 76.1036 (table 9, ratio A). Although the neck of MNHNCu 76.1018 is partially preserved, its angulation in relation to the shaft cannot be reliably established.

The distal epiphysis MNHNCu 76.1019 (fig. 21), also from an immature animal, pairs well with the proximal femur in terms of relative size, but nothing associates these specimens beyond the fact that they were found in the same chimney fill. As in Xenothrix (and many other mammals) there is a small facet on the posterior articular surface of the lateral condyle for a sesamoid, the lateral fabella. The anterior patellar surface, which is deeper than in Xenothrix, has lost some material just where the craniad border of the epiphysis would have met the diaphysis; however, the measurement (12.3 mm) of this feature is unlikely to be greatly in error.

The lateral condyle is damaged in MNHNCu 76.1019, and therefore condylar width as defined by MacPhee and Fleagle (1991) cannot be taken directly on this specimen. However, one's visual impression is that the lateral condyle was relatively larger than in Xenothrix, and that therefore the condylar proportionality ratio was actually higher than in the Jamaican monkey (see MacPhee and Fleagle, 1991, for additional comparative data and discussion of ratios).

Functional Considerations

Xenothrix Amnhm 259903

Two proximal tibiae from the Long Mile faunal collection (the more complete of which is illustrated in fig. 22) were assigned to Xenothrix by MacPhee and Fleagle (1991). No additional discoveries have been made in recent years. As preserved the incomplete shafts of the Long Mile specimens are comparatively straight. The medial condylar articular facet is larger in area than the lateral, which is consistent with the asymmetry of the femoral condyles in Xenothrix. According to MacPhee and Fleagle (1991), certain features (size and prominence of scars for hamstrings and tibial tuberosity) suggest an animal that was capable of powerful flexion and extension at the knee. However, because of the inferred overall shortness of the hind limb and presence of features indicating slow climbing, exceptional leaping ability is unlikely.

Paralouatta Mnhncu 76.1034

MNHNCu 76.1034 is the distal end of a right tibia, with half (or less) of the shaft preserved (fig. 23; table 11). The posterior and lateral aspects of the distal end are damaged, including the area where the fibular notch was situated. The interosseous border is faintly indicated, but otherwise there are no strong lines or muscle markings on the shaft. The anterior “border” is smoothly rounded rather than sharp, as in platyrrhines generally. The diaphysis was probably relatively straight, as it is in most but not all platyrrhines (fig. 25B, F, J), although with only half of the element available this point cannot be settled.

The medial aspect of the distal tibia of Paralouatta is distinctive: the shaft is quite massive anteroposteriorly, and terminates distally in a wide, blunt malleolus (fig. 23B). The anterolateral aspect of the malleolus terminates in a poorly defined facet (fig. 23A) for the cotylar fossa of the talus. In primates generally the malleolus tends to be pyramidal rather than rectangular (fig. 25), but the specimens of Ateles belzebuth (fig. 25F) and Lagothrix lagotricha (fig. 25J) in the comparative set show some approximation to the condition in Paralouatta.

Note also that, in posterior view (fig. 23C), the tibia's lateral surface is remarkably straight compared to tibiae of other large-bodied platyrrhines such as Ateles and Lagothrix (fig. 25G, K), in which the lateral surface of the distal end is slightly projecting. The squared-off appearance of the region of the fibular facet resembles the condition in many catarrhines (Hershkovitz, 1988; cf. Lophocebus, fig. 25O). This arrangement may have allowed the distal moiety of the fibular shaft to be closely approximated to the facing surface of the tibia (cf. Meldrum and Kay, 1997). However, it is also clear that, unlike Lophocebus, the lateral margin of the distal articular surface is not deeply notched by the fibular facet in Paralouatta (fig. 23D). The significance of this is uncertain, because according to Ford (1986a) Old and New World monkeys differ markedly in the size and depth of the fibular facet.

Finally, the malleolus bears a small excavation (fig. 23C) where one might expect a groove for the tendon of tibialis posterior m. (as in Cebus, fig. 25C). However, the floor of the groove is rough rather than smooth, and the feature itself is oriented at an angle impossible for the tendon to assume. Bone lateral to this area is badly abraded and it is not clear whether there were grooves for this last muscle or flexor digitorum longus m.; on the whole it seems doubtful that there were.

Antillothrix Usnmm 254682

Ford (1986a) described the Samaná tibia (fig. 24) in some detail and compared it to a wide range of other primates, and in regard to basic anatomical details we are in agreement with most of her observations. However, like Hershkovitz (1988) we are not convinced that the morphology of the distal tibia supports a strong case for callitrichid affinities. Indeed, of the numerous tibial characters that Ford (1986a, 1986b) considered in her cladistic analysis, only three strongly implied a callitrichid connection, and two of these are variable within the latter group. The remaining character, strong development of a bony flange for conducting the tendon of tibialis posterior m. into the foot, is produced to about the same degree in the Samaná tibia and Saguinus (which are shown as sister taxa in Ford's cladogram). However, this feature, which is not uncommon among mammals generally (MacPhee, 1994), shows about the same amount of development in Callicebus. As already noted the flange is absent in Paralouatta, making it further doubtful that this is a feature of much systematic valency. Hershkovitz (1988: 383) concluded that the Samaná tibia represented “a platyrrhine distinct from known living forms”, possibly the same species as Antillothrix bernensis. Although we favor the same conclusion, it is unlikely that there will be any consensus until there is new material to evaluate.

Both Paralouatta MNHNCu 76.1034 and the Samaná tibia (fig. 24) are notably robust for their respective sizes, as far as this can be judged, but they differ in several details (e.g., medial malleolus in Antillothrix is pyramidal in medial aspect, as in anthropoids generally, whereas in Paralouatta it is more massive and rectangular). The cotylar facet is well developed in both.

Functional Considerations

Paralouatta Mnhncu 76.1037 and 76.3059 (talus)

Two tali have been referred to Paralouatta: one is the partial talus MNHNCu 76.1037 of Paralouatta varonai from Cueva Alta (fig. 26A–D); the other is MNHNCu 76.3059 from the Early Miocene locality of Domo de Zaza, which MacPhee et al. (2003) recently made the holotype of a second species, P. marianae (fig. 26E–H). These authors noted that the two specimens differ only slightly—a remarkable point, given that 17–18 Ma allegedly separate them (see Introduction)—and for the characters of interest here they are nearly identical. Because MNHNCu 76.1037 is quite incomplete, we feel that it is justified to utilize the Miocene fossil as our basis for genus-level comments in this section.

In an earlier paper, MacPhee and Iturralde-Vinent (1995) concluded that there were no strong matches for the talus of Paralouatta among living platyrrhines. In particular, they noted that large-bodied platyrrhines (living atelines and Alouatta) differ sharply from Paralouatta in possessing a “wedged” trochlear articular surface with overall low trochlear relief. This morphology helps insure maximum mobility at the talocrural joint; by contrast, the talus of Paralouatta seems to have been built for stability (MacPhee and Iturralde-Vinent, 1995).

Paralouatta tali also present a definite if shallow cotylar fossa fronting a lengthy articular surface for the medial malleolus (fig. 26A, C), thereby providing firm seating for the latter. The limits of the fossa are difficult to make out because of damage to the neck in both specimens. Talar cotylar fossae are insignificant (when present at all) in larger platyrrhines such as Ateles, Chiropotes, and Alouatta but are well developed in Old World monkeys such as Theropithecus and Lophocebus. According to Gebo and Sargis (1994), there is a similar contrast (but on a lesser scale) between moderately terrestrial Cercopithecus lhoesti and highly arboreal C. mitis. Previously, it was assumed (e.g., MacPhee, 1994) that the cotylar fossa was limited to cercopithecoids, in which it is normally well defined. Very deep cotylar fossae, not to be compared with the modest versions in primates under discussion here, occur in graviportal terrestrial mammals as disparate as the bear Ursus, the giant rodent Amblyrhiza, and the bibymalagasy Plesiorycteropus (MacPhee, 1994; see also Zack et al., 2005).

To better characterize the distinctions of the Paralouatta talus, we took 12 morphometric measurements on MNHNCu 76.3059 and the tali of 14 other platyrrhine genera (fig. 27; see tabulated data presented by Meldrum [1990]). Size-adjusted variates were created by scaling to the sum of talar head width and height. Paralouatta stands somewhat apart from the main trend linking talar size to m1 mesiodistal length in platyrrhines (although it is closest to uakaris and woolly monkeys), suggesting that it has a relatively large m1 for its talar length (fig. 28).

Principal components analysis was carried out on both the individual specimens and the genus-level means, with comparable results. For brevity, the plots of the analysis of the means are presented along with the loadings of each variable on the first three axes, accounting for 99% of the variance (fig. 29, table 13). The scatter produced a pattern that arranged the tali in a series of clusters corresponding to atelines, pitheciines-cebines, and callitrichines, with modest intergroup overlap; these results are comparable to those previously reported by Meldrum (1990). The talus of Paralouatta is notably distinct from the tali of other platyrrhines. In particular, the lack of trochlear “wedging” sets Paralouatta off from all other large-bodied platyrrhines along the second component in the principal components analysis, and is reflected in the high negative loading of posterior trochlear width (PTW) in table 13.

Paralouatta Mnhncu 76.1020 (calcaneus) and Mnhncu 76.1021 (middle Cuneiform)

The single calcaneus ascribed to Paralouatta is highly incomplete and badly preserved (fig. 30). Among the few features that can be readily discriminated is the indication of a very wide peroneal shelf on the lateral side of the specimen, also seen (but not uniquely) in Callicebus.

Only a fraction of the plantar surface is preserved. The area still present is relatively flat as in Lophocebus rather than sharply ridged as in Alouatta. However, Lophocebus is not markedly different from Brachyteles in this regard, indicating that this feature is not correlated with a single locomotor category. Unfortunately, the plantar tuberosity for the origin of quadratus plantae m. (flexor accessorius m.), which is very pronounced and projecting in Alouatta and Brachyteles but not as developed in Lophocebus and Theropithecus, is not preserved in this specimen.

Among the more unlikely fossils recovered from Cueva Alta is the perfectly preserved middle cuneiform illustrated in figure 31. The facet for the head of the navicular is narrow but markedly rounded for reception of the navicular. This suggests that midfoot dorsoventral mobility was well developed, as is true of most anthropoids other than humans.

Paralouatta Mnhncu 76.1022, 76.1023, and 76.1025–76.1028 (metapodials)

Examples of both MC1 and MT1 are available, permitting them to be clearly discriminated morphologically and metrically. The single specimen of MC1 (MNHNCu 76.1022) is about three-quarters the length of the only MC2 (MNHNCu 76.1023) in the collection (table 14). Compared to that of Alouatta seniculus and other large-bodied extant platyrrhines, the MC1 of Paralouatta (fig. 32) has a relatively less bulbous head, a straighter shaft, and a less projecting ulnar border. In addition, there are two prominent crests on the distal end not seen in the howler monkey. The one on the radial side is presumably for insertion of abductor pollicis longus m.; the one on the ulnar side, if not for the attachment of ligamentous tissue, is dubiously for the origin of an unusually developed first palmar interosseous m. A similar morphology is seen in the thumbs of some Old World monkeys (e.g., Trachypithecus pileatus). The joint surface for the trapezoid is uniaxial and semicylindrical, as is normally the case in platyrrhines. There are obvious facets for distal sesamoids.

Of the two MT1s in the collection, MNHNCu 76.1025 (fig. 34) is relatively complete; MNHNCu 76.1026 lacks its proximal end and has not been illustrated. The MT1 resembles the equivalent element of Alouatta, with the difference that the process for peroneus longus m. is better developed in the former. There is torsion of the head, but Alouatta exhibits about the same degree of twisting as Paralouatta. There are several additional metapodials in the hypodigm (table 2), the best preserved of which are MC2 MNHNCu 76.1023 (fig. 33) and MT3 MNHNCu 76.1028 (fig. 35). As discussed below, in relation to the estimated BM of Paralouatta, all metapodials are robust and relatively short (cf. table 14).

Paralouatta Mnhncu 76.1029–76.1033 (phalanges)

As already noted, some of the phalangeal elements described in this section assigned to the Paralouatta hypodigm have unusual features. However, there does not appear to be any other vertebrate taxon to which they could be justifiably assigned, and they are therefore accepted here as belonging to the Cuban monkey.

There are four proximal phalanges assignable to Paralouatta. The first of these (MNHNCu 76.1029, fig. 36A) is distinct morphologically, and judging from the asymmetry of its proximal articular surface, it must be part of a DR1. Its size and robusticity suggest that it belongs to the DR1 of the pes (cf. Hamrick et al., 1995), which means that the condition of the thumb in the Cuban monkey is still unknown. However, given the large size of MC1, there is no reason to suspect that the thumb was reduced as in atelines.

The remaining proximal phalanges (MNHNCu 76.1030a–c) can be placed only in a general sense, as representatives of one or another of DR2–5; only one (MNHNCu 76.1030a) is complete (fig. 36B). Its proximal end is notably expanded, with a single concave facet for reception of a large metapodial head. The shaft is marked by ridges for the flexor sheath, and the head presents the usual pulley-shaped articular surface for the middle phalanx. Although this specimen is utilized in the reconstruction of DR2 (manus) in figure 37, there is no morphological basis for regarding it as manual rather than pedal.

A group of 12 distinctive middle phalanges from the monkey caves were compared to, and found to be unlike, those of any known megalonychid, capromyid, echimyid, or solenodontid (i.e., the other terrestrial mammalian taxa represented in the Quaternary fauna of Cuba). All are extremely short, averaging 9.6 mm in length (cf. table 14, footnote b), and are robust for their length. Apart from size, however, they otherwise resemble typical platyrrhine middle phalanges and may reasonably be considered to represent Paralouatta (fig. 36C). Their proximal ends are dimpled by two small, concave facets separated by an indistinct ridge, to articulate with the pulleys of the proximal phalanges. Their distal ends are likewise pulley-shaped to receive the unguals. Each bears well-defined medial and lateral ridges for insertion of flexor digitorum superficialis m. and associated flexor sheath.

The five distal phalanges in the hypodigm are notably unlike their counterparts in other Cuban mammals. Four are similar to one another and display expanded or “cauliflower” distal ends (tuberosities or apical tuffs), to which connective tissues of the finger-tip pulp would have attached (MNHNCu 76.1032a–d, fig. 36D). One would normally conclude without hesitation that unguals having this morphology must represent DR1, because in known platyrrhines the unguals of digits other than the thumb and big toe are conical or only slightly expanded. In the existing Paralouatta hypodigm there is only one specimen (MNHNCu 76.1033, fig. 36E) answering to this latter description, although because the specimen in question is somewhat damaged it is difficult to be sure of its original condition. It might be argued that the odds are against recovering four unguals of DR1 but only one representative from all of the other digital rays combined, but the alternative interpretation is that distal expansion was present on many or most distal phalanges in Paralouatta. Were that the case, distal phalanx morphology in the Cuban monkey would be unlike that of any other New World monkey, large or small—or, for that matter, any Old World monkeys except the large ground-adapted species like Theropithecus gelada and Macaca nemestrina in which the unguals are distally expanded. Erythrocebus patas displays a different pattern which may be relevant to note: the distal phalanges of most fingers and toes other than the thumb and big toe are only slightly expanded, but the axial digits (DR3) have larger and wider elements not unlike MNHNCu 76.1032a (fig. 36D).

It is unfortunate that the issue of distal phalanx placement has to be left unresolved, as the condition of DR2–5 unguals would appear to have some diagnostic value regarding preferred substrate. However, there is an additional source of inference, digital ray length, that provides some further functional insight into the Cuban monkey's cheiridial morphology (see next section).

Functional Considerations