SYSTEMATIC PALEONTOLOGY
(continued)

Superfamily Giraffoidea Gray 1821
Family ?Giraffidae Gray 1821

Genus Progiraffa Pilgrim 1908

Diagnosis

Moderate-sized pecoran (m2-m3 length: ~ 5.3 cm). Ossicones present. Brachyodont teeth with rugose enamel. Lower molars with prominent metastylid well separated from the metaconid, lingual face of metaconid and entoconid convex, m3 with robust entoconulid filling the lingual wall. “Palaeomeryx‑fold” absent. Upper molars with subsidiary spurs separate from labially directed postprotocrista and premetaconule crista. Postmetaconule crista with bifurcation. Low lingual cingulum on posterior of protocone.

Progiraffa exigua Pilgrim 1908

Diagnosis

As for the genus.

New Material

Locality Z 117: 2376, medial phalanx.

Locality Z 120: Z 593, fragment of a right p2 or p3; Z 2276, left astragalus; Z 2392, right lower molar fragment.

Locality Z 121: Z 2274, right distal metatarsal.

Locality Z 124: Z 162, posterior portion of skull.

Locality Z 126: Z 2391, distal left humerus.

Locality Z 137: Z 202, right cuboid-navicular; Z 210, proximal left femur.

Locality Z 203: DGK 15, left astragalus.

Locality Z 205: DGK 23, right astragalus; DGK 45, left proximal femur; DGK 148, fragment of an ossicone; Y 41662, left mandible with incomplete m1 and m2.

Locality Z 211: DGK 145, left unciform; DGK 204, astragalus; DGK 215, right m1 or m2; DGK 291, right magnum-trapezoid.

Locality Z 212: DGK 188, right astragalus; DGK 200, right distal metacarpal.

Locality H 8115: H 208, left m3; H 664, right M3(?).

Locality H 8125; H 312, right maxilla with erupting P3 and DP4-M3.

Locality S 2: S 88, very worn left m1 or m2; S 412, left p3.

Locality S 4: S 48, incomplete left m3; S 495, fragment of a right m1 or m2.

Locality S 6: S 154, right m1 or m2.

Locality S 15: S 305, right mandible fragment with m1 or m2.

Locality Y 591: Y 24013, broken left cuneiform; Y 24020, distal metapodial; Y 24021, fragment of a left P4; Y 31676, left m1 or m2.

Locality Y 592: Y 17554, incomplete left astragalus; Y 31204, fragment of a left calcaneum; Y 31206, right P4; Y 47224, medial phalanx; Y 47225, right fibula.

Locality Y 652: Y 23429, left cuneiform.

Locality Y 687: Y 47366, proximal phalanx.

Locality Y 721: Y 26598, incomplete right astragalus; Y 26599, fragments of a right calcaneum.

Locality Y 738: Y 31148, fragment of a very worn left upper molar.

Locality Y 744: Y 40808, incomplete right astragalus.

Locality Y 747: Y 31733, left cuboid-navicular; Y 31735, left unciform; Y 31736, left cuneiform; Y 31739, left cuneiform; Y 31743, incomplete right astragalus; Y 31745, fragment of a right astragalus; Y 31748, left astragalus; Y 31760, medial phalanx; Y 31764, proximal portion of a proximal phalanx; Y 31766, medial phalanx; Y 31768, distal metapodial; Y 31771, distal portion of a medial phalanx; Y 31772, distal fragment of a proximal phalanx Y 31773, medial phalanx; Y 31774, medial phalanx; Y 31775, distal metapodial; Y 31776, distal metacarpal; Y 31784, right distal femur; Y 31787, proximal left tibial epiphysis; Y 31789, fragment of a proximal right tibial epiphysis; Y 31794, fragment of a left distal radius; Y 31797, lower left p3; Y 41455, distal metapodial; Y 46276, distal metapodial; Y 46277, left cuneiform; Y 46284, fragment of a left astragalus; Y 47475, proximal portion of a proximal phalanx; Y 47476, proximal phalanx; Y 47477, fragment of left m1 or m2; Y 47478, distal portion of a proximal phalanx; Y 47479, distal metapodial epiphysis.

Locality Y 780: Y 32920, small fragment of a right astragalus.

Locality Y 802: Y 46236, right fibula; Y 46237, left lunar.

Locality Y 843: Y 41451, distal portion of a proximal phalanx.

The presence of three left cuneiforms at Locality Y 747 indicates there are at least three individuals at that site.

Localities and Age

Pilgrim’s type specimen is from the equivalent of the Chitarwata Formation at Dera Bugti, but its age is not known with any certainty. The Zinda Pir sites are in the upper unit of the Chitarwata Formation and the overlying Vihowa Formation, with an age range of approximately 20 to 17 Ma (Lindsay et al. this issue). The Manchar sites (GSP-H and GSP-S) are in the lower part of the sequence (Raza et al. 1984; Hussain, personal commun., 1986) and are of Lower and Middle Miocene age. The oldest Potwar sites (GSP-Y 747 and Y 721) are at the base of the terrestrial sequence in the Salt Range and are estimated to be about 18.3 Ma, while the youngest (GSP-Y 591 and Y 592) are estimated to be about 16.0 Ma (Johnson et al. 1985). Ginsburg et al. (2001) have reported additional specimens from level 6 of Welcome et al. (2001) in the Chitarwata Formation at Dera Bugti, to which the latter authors assign an Early Miocene age.

Description

Lower Dentition. The available specimens are all isolated premolars and molars, except for Y 41662, a mandible with broken but otherwise well-preserved m1 and m2. The presumed p3’s (S 412 and Y 31797) (Figure 9.1-9.2) are low and long, with faint labial incisions, a large posterolingually directed metaconid that runs parallel to the equally strong, oblique entoconid. The latter converges on a large, more transverse entostylid to define a basin with a narrow lingual opening. The long anterior crest is bifurcated, with a robust, lingually directed paraconid. In both specimens there is a low cingulum just behind the base of the paraconid.

The lower molars (Figure 10.1-10.4) are brachyodont, with fine striations in the enamel. The obliquely situated metaconid and entoconid have flattened labial faces but retain convex lingual faces with weak development of lingual ribs in some cases. The premetacristid contacts the anterolabial end of the preprotocristid, while the posthypocristid reaches the labial side of the tooth, ending in a tubercle and nearly closing off the posterolingual end of the median valley. In all specimens the prehypocristid is separate from the preentocristid and trigonid cusps, even in very advanced wear. None of the molars have even a vestige of a “Palaeomeryx‑fold,” but all have large lingually displaced metastylids that are separated from the metaconid by a strong vertical groove. The metastylid typically lies lingual to the anterior end of the preentocristid. In two of the molars (S 305 and Y 31676) (Figure 10.1-10.2) there is a small entostylid terminating the postentocristid. This entostylid is distinct from the tubercle on the posthypocristid. All the molars have low ectostylids and anterior and posterior basal cingula.

Both of the more complete m3’s (H 208 and S 48) (Figure 10.3-10.4) have simple, crescent-shaped hypoconulids and a large entoconulid that fills the space between the entoconid and hypoconulid, making the lingual wall of the hypoconulid loop continuous. In S 48 the posthypocristid contacts the entoconulid.

Upper Dentition. H 312 (Figure 11.1) is a well-preserved maxilla with undamaged crowns of all the molars, a worn dP4, and P3 exposed but still in its crypt. An unerupted P4 is also present, but only the forming roots are visible and the crown is hidden within the maxilla. P3 has a tall, anteriorly situated paracone with a strong labial rib and foreshortened anterior crest. The posterior crest of the paracone is, in contrast, elongated and blade-like. A large parastyle is separated from the paracone by a deep vertical groove. The anteriorly situated protocone is connected to the parastyle by a low crest forming a convex lingual wall. Within the posterior fossette of the median valley there is a complicated, low spur of enamel connecting to the inner wall of the postprotocrista and running anteriorly.

The upper molars are low crowned, with large metaconules on M1 and M2. On M3 the metaconule is smaller than the protocone. The parastyles and mesostyles are prominent on all the molars, the paracones have very strong labial ribs and the metacones flat labial faces. On the M1 the postmetaconule crista has a distinct bifurcation, and there are faint traces of this condition on M2 and M3. The three molars of H 312 have a complex of low enamel spurs near the junction of the postprotocrista and premetaconule crista. On M2 and M3 these appear as a bifurcation of the worn premetaconule crista, but on M1 it has a more complex shape. These spurs clearly have formed as structures separate from the postprotocone and premetaconule crista, although with wear they appear to merge with the centrally directed crista. Both M2 and M3 have a low cingulum on the posterior face of the protocone. This cingulum originates between the protocone and metaconule. At the base of the metaconule there is an entostyle-like structure.

H 664 (Figure 11.2) is judged to be an M3 because, although in advanced wear, it has no posterior interdental facet. In addition, the metaconule is smaller than the protocone, as is typical of an M3. The molar has a bifurcated postmetaconule crista, but it does not have the small spurs, entostyle, nor protocone cingulum seen in the other specimens.

Cranial Remains. Ossicones: DGK 148 (Figure 12.1-12.3) is a small section of an ossicone (here used broadly to include the branched structures of Climacoceras). The specimen is associated with a mandible (Y 41662) and postcranials referred to Progiraffa exigua. We assume, therefore, it also belongs to Progiraffa exigua. The ossicone is possibly a midbeam segment, approximately 57.3 mm long. It is straight and tapers toward the presumed distal end, with cross-section dimensions of 24.6 x 18.6 mm at the craniad end and 19.0 x 14.9 mm distally. In cross section it has an oval shape, flattened on one side and with the greatest minor dimension slightly off center. In cross section there is a gradual transition between a very thin (3-6 mm at proximal end) outer zone of dense cortical bone and the largely cancellenous interior. The surface has many fine grooves originating from nutrient foramina at their proximal ends. These structures are scattered uniformly about the surface and spiral counterclockwise about the long axis of the bone when viewed from the distal end.

Skull: Z 162 (Figure 13.1-13.4) is the rear of a broken skull. The specimen represents a medium-sized ruminant and, as Progiraffa is the only known appropriate sized ruminant at this level, we refer it to that species.

The specimen comprises the posterior of a damaged cranium, lacking teeth and ossicones. Except for the nuchal crest and a small remnant of the most dorsal part of the supraoccipital, the dorsal surface of the cranium has been broken away, exposing a natural endocast of the brain. The ventral surface has suffered only minor damage, while the supraoccipital region is more or less intact. Although the frontals and skull roof have been destroyed, the great thickness of the dorsal-lateral part of the lambdoidal crest and orientation of the dorsal part of the supraoccipital suggest that the skull roof was domed or that there may have been large posterior cranial appendages. The supraoccipital is posteriorly projecting and laterally expanded as it contacts the lambdoidal crest, with shallow pits for the semispinalis capitis. Above the foramen magnum, the supraoccipital is slightly swollen, while ventrally the paired occipital condyles are completely fused into a ring-like structure, with the intercondyloid notch (incisura intercondyloidea of Hamilton [1973]) obliterated. The mastoid is narrowly exposed. On the ventral side of the skull, the styloid process is posterolateral to and well separated from the auditory bulla. The bulla is inflated and hollow, with an oval outline in ventral view. It is well separated from the basioccipital and is not anteriorly elongated. Consequently the middle lacerate foramen is left uncovered. The basioccipital is posteriorly wide, narrowing anteriorly. It has well-developed, laterally projecting condylar flexion stops (posterior tuberosities). A pair of very subdued basilar tubercles is located posteriorly at about the level of the posterior lacerate foramen, while anteriorly at the level of the foramen ovale there is a second pair of very faint swellings. A median keel originates between these latter swellings, running anteriorly onto the broken sphenoid. Anterior and lateral to the posterior pair of basilar tubercles and just medial to the auditory bulla there are paired irregular pits.

Postcranial Remains. Calcaneum: Y 31204 and Y 26599 both preserve the fibular, cuboid, and much of the astragalar articulations, and in the case of 26599 part of the calcaneal process. The fibular articulation is typically pecoran, with a large convex posterior facet and a smaller concave-convex anterior one. The bulbous posterior fibular articulation has a medially projecting conical process with a distinct posteromedial facet for the proximal lateral facet of the astragalus.

Fibula: Y 47225 is a distal fibula with a small spine indicating it is a reduced remnant. Although damaged, the anterior tibial facet is narrow and flat, and apparently did not curve medially.

Astragalus: The best preserved specimen is DGK 188, while all the others are broken or corroded by weathering. The disto-lateral calcaneal facet is separated from the raised lateral edge of the susentacular facet by a large sulcus, while the proximal lateral calcaneal facet is confined to the edge of the susentacular facet and is separated from the dorsal fibular facet. The cuboid condyle extends laterally, creating a distinct notch on the lateral side of the astragalus, while the cuboid portion of the condyle is cylindrical. The astragalus is narrow, with an approximate width to length ratio of 1:1.7.

Cuboid-navicular: Z 202 is the more complete specimen, but has been cracked and fractured, obscuring some of its features. Y 31723 is very well preserved, except for having lost the postero-ventral portion of the astragalar articulation. In proximal view both are dorso-ventrally narrow compared to the medial‑lateral diameter, with the cuboid‑astragalar facet being slightly wider than the navicular‑astragalar one. The medial plantar process is very prominent and the dorso‑medial angle of the navicular-astragalar articulation is retracted. In distal view, the distal process does not extend to the lateral margin of the anterior cuboid‑metatarsal facet and the relatively broad posterior metatarsal articulation has a slightly inclined medial part originating near the entocuneiform facet with a more horizontal lateral extension. The facet for the 4th metatarsal lacks a posterior medial extension bounding the groove for the tendon of the peroneus longus. Consequently the peroneus groove is shallow and broad. The junction between the ectomesocuneiform and endocuneiform articulations rises to form a low prominence, but both facets are on the same level.

Lunar: The sole example (Y 46237) is too poorly preserved to describe.

Cuneiform: With four well-preserved examples and a fifth broken one, the cuneiform is the most common postcranial element. They demonstrate slight morphological and size variation, but the stratigraphically youngest (Y 23429) is typical in all respects. The unciform articulation is relatively short and the disto-ventral process is directed ventrally rather than being inflected distally. The pisiform articulation is narrow at its proximal end, with its lateral margin being continuous rather than angled at the junction with the ulnar articulation.

Magnum-trapezoid: The sole example (DGK 291) is well preserved. Its dorsal ventral diameter is much larger than its medio-lateral diameter, primarily because the lunar articulation is narrow and not extended laterally. The junction between the lunar and scaphoid articulations forms a high proximal keel. The inferior posterior unciform facet is widely separated from the anterior one.

Unciform: The two referred specimens (DGK 145 and Y 31735) differ somewhat in size and morphology, apparently reflecting individual variation. DGK 145 is the smaller of the two. Its lunar articulation has a flat, rectangular dorsal part that rises ventrally to form an almost cylindrical condyle. The articulation for the cuneiform is relatively narrow, without a marked lateral lip. The junction between the cuneiform and lunar articulations is well differentiated, but low so that the two lie in nearly the same horizontal plane. Y 31735 differs primarily in being about 10% larger and in having a relatively wider posterior lunar articulation and a narrower one for the cuneiform.

Metapodials: The fossils are all distal portions. Three specimens (Z 2274, DGK 200, and Y 31776) preserve both the third and fourth digits, while the remainder have only one side. Z 2274 is a metatarsal, while DGK 200 and Y 31776 are metacarpals. The metatarsal gully appears to be open in Z 2274, but the shaft is not preserved proximally enough to be certain. In all specimens the keels of the distal articular surface extend dorsally but do not project as far as they do ventrally. Consequently, in lateral view the keels are strongly asymmetrical. The external condyle has a lipped rim which, while stronger ventrally, also extends dorsally. The dorsal articular surface of the external condyle is thus complete. Both the external and internal articular surfaces terminate in a small pit on the dorsal side of the shaft.

Comparisons

The presence of ossicones leads us to tentatively place Progiraffa in the Giraffidae.

Progiraffa exigua differs from middle Miocene giraffids (sensu Hamilton 1978) such as Giraffokeryx punjabiensis Pilgrim 1911 and Injanatherium Heintz, Brunet, and Sen 1981 in numerous ways (Colbert 1933; Morales et al. 1987). These include the presence in Progiraffa of a large, well-separated metastylid, a cingulum on the protocone, and an enamel complex connecting the postprotocrista and premetaconule crista. Progiraffa also seems to have a more sporadic presence of a bifurcated metaconule and a more primitive basicranium with small basilar tubercles and an oval auditory bulla that is well separated from the basioccipital.

Progiraffa is similar to various primitive giraffoids, such Propalaeoryx Stromer 1926, Climacoceras MacInnes 1936, Teruelia Moyà-Solà 1987, and Lorancameryx Morales, Pickford, and Soria 1993. The first of these, Propalaeoryx, is smaller and as far as is known lacks cranial appendages. It also has a more anterior P3 protocone, lacks entostyles on the molars, and the Namibian species P. austroafricanus has a “Palaeomeryx‑fold” on the lower molars (Morales et al. 1999). The ossicone described here for Progiraffa exigua could be a segment of the branched, antler-like ossicone of Climacoceras, although it shows no sign of secondary tines and its internal structure has a greater mass of cancelleous bone and only a thin outer layer of dense cortical bone. The many fine surface grooves and nutrient foramina on the Zinda Pir specimen are also absent in Climacoceras africanus, although Hamilton (1978) noted them in C. gentryi. Dentally both species of Climacoceras differ from Progiraffa. Their rather hypsodont lower molars have more compressed lingual cusps with nearly parallel axes, metastylids that are not separated from the metaconid, and m3 with the hypoconulid lingual wall incomplete. Climacoceras also has a more anterior P3 protocone and narrower upper molars. Most of the same dental characters differentiate Progiraffa from Lorancameryx and Teruelia, the latter also lacking the bifurcated paraconid on p3.

The close similarity between Progiraffa and Canthumeryx sirtensis Hamilton 1973 (including Zarafa zelteni Hamilton 1973) has been noted before (Moyà-Solà 1987, Gentry 1994; Ginsburg et al. 2001). Canthumeryx is known principally from the dentition and postcranials, to which a skull may be added if the synonymy of Zarafa is accepted (Hamilton 1978, but see Janis and Scott 1987). This taxon is near the size of Progiraffa and nearly indistinguishable dentally. Possible points of difference are a slightly stronger and more isolated metastylid in Progiraffa and stronger bifurcation of the postmetacrista and greater development of lingual basal structures in Canthumeryx (shown principally in material originally attributed to Zarafa). The posterior and basicrania of the skull of Progiraffa are also very similar to Canthumeryx. Canthumeryx, however, has a flat skull roof, a large swelling over the foramen magnum, an open intercondyloid notch, and it appears to have a larger, more anterior pair of basilar tubercles. The slender ossicone fragment (DGK 148) described here is also difficult to reconcile with the massive bases seen in the referred skull of Canthumeryx, although Churcher (1978; fig. 25.10) choose to reconstruct the specimen with slender, spike-like ossicones.

Nyanzameryx pickfordi Thomas 1984 and Prolibytherium magnieri Arambourg 1961 are two additional primitive giraffoids sharing some features of the skull and dentition with Progiraffa (Geraads 1986). The isolated ossicone (DGK 148) is especially noteworthy, in that it could be a segment of one of the slender ossicones of Nyanzameryx. However, the nuchal area of the East African species is more gracile and less projecting, while the basicrania has more anteriorly positioned basilar tubercles. In addition, Nyanzameryx has lower molars with compressed lingual cusps nearly parallel to the axis of the tooth, metastylids that are not well separated from the metaconid, and m3 with the hypoconulid lingual wall incomplete. It is also a much smaller taxon. Prolibytherium magnieri shares one very distinctive feature with Progiraffa in that it has a reduced intercondyloid notch, while the basilar tubercles are posteriorly situated and very subdued. The great thickness of the skull roof of Progiraffa suggests the presence of large and elaborate ossicones as in Prolibytherium. The supraoccipital of Prolibytherium, however, does not project so strongly posteriorly. There are also dental differences from Progiraffa, principally in the possession of compressed lingual cusps that are more parallel to the axis of the tooth, metastylids that are not well separated from the metaconid, and an incomplete hypoconulid on m3.

Discussion

The initial description of Progiraffa was very brief and included only one species (Pilgrim, 1908). In his subsequent, more detailed account of Progiraffa Pilgrim (1911) referred a second species to the genus, one which Lydekker (1883) had originally described as Propaleomeryx sivalensis. Lydekker's single specimen is an isolated upper molar, with few distinctive characters. It lacks the secondary complex of low enamel spurs near the junction of the postprotocrista and premetaconule crista, and is similar to the molar (H 664) from Sind. Except for its smaller size, the latter specimen is virtually indistinguishable from Giraffokeryx punjabiensis. The type specimen of Progiraffa exigua was until recently all that was known of the taxon, but the new collections show the species is rather common.

The reference of both the ossicone (DGK 148) and skull (Z 162) to one species is somewhat problematic. The construction of the nuchal area of the skull (Z 162) suggests the cranial appendages were probably robust and perhaps even similar to those of Prolibytherium. This combination seems incompatible with the more spike-like ossicone DGK 148. The skull fragment is about 19 Ma while the ossicone fragment is between 18 and 16 Ma (Lindsay et al. this issue). Both are from the Vihowa Formation.

The oldest specimen we attribute to Progiraffa exigua is a poorly preserved distal humerus (Z 2391) from the upper unit of the Chitarwata Formation, at a level we estimate to be 20 Ma. The specimen is clearly a large pecoran, but might belong to the indeterminate large pecoran (Z 2031) from locality Z 127 rather than Progiraffa exigua. However, it is appreciably larger than what we expect for a tooth the size of Z 2031 and is an appropriate size for Progiraffa exigua.

On the Potwar Plateau Progiraffa exigua persists up to at least 16 Ma. There are postcranial remains of a larger form that is morphologically similar from sites between 16 and approximately 14 Ma. While these might belong to another species of Progiraffa, we do not describe nor discuss this larger form because it is only known from postcranial elements. The cuneiform (Y 23429) from locality Y 652 is associated with a large distal metapodial, which is likely to represent the larger pecoran, indicating the two probably co-existed. After 14 Ma the still larger but morphologically different remains of Giraffokeryx are found.