A new condor (Ciconiiformes, Vulturidae) from the late Miocene/early Pliocene Pisco Formation, Peru (página 2)
Order Ciconiiformes (Bonaparte 1854) Family Vulturidae (Illiger 1811)
Perugyps gen. nov.
Perugyps diazi sp. nov. (Fig. 2–4)
Holotype. Right carpometacarpus missing proximal portion of os metacarpale minus (MUSM 213; Fig. 2A), collected by M. Stucchi, July 2000.
Locality/horizon. Pisco Formation, Montemar vertebrate-bearing locality (late Miocene/early Pliocene; 6.0–4.5 Ma; de Muizon and DeVries 1985; DeVries, pers. comm.).
Diagnosis. Perugyps is diagnosed as a condor by the following characters:
Mandible with symphysis proportionately larger than in Coragyps, Cathartes melambrotus Wetmore 1964, and Gymnogyps; smaller than in Sarcoramphus and Vultur; and similar in proportions to Cathartes aura (Linnaeus 1758). Symphysis is proportionately broader and the dentary has a relatively higher coronoid process than in all living Vulturidae. Mandible longer than in Vultur gryphus Linnaeus 1758 and Gymnogyps californianus (Shaw 1798, Table 1).
Sixth cervical vertebra with prezygopophyses angled more anteriorly, rounder and more robust, than in Vultur and Gymnogyps; postzygopophyses rounder and angled more laterally than in Vultur and Gymnogyps.
Coracoid with deep and rounded sternocoracoidal impression that is not pneumatic (shallower and not rounded, often pneumatic in Vultur, Gymnogyps, Sarcoramphus, Coragyps, and Cathartes).
Carpometacarpus with anterior carpal fossa less pneumatic than in Vultur, Gymnogyps, Sarcoramphus, Coragyps, and Cathartes. Proximal symphysis short, as in Vultur; symphysis relatively longer in Cathartes, Coragyps, and Gymnogyps. MUSM 206 has a muscle scar for the flexor metacarpi short and pronounced, as in Vultur and Breagyps (L. Miller 1910); scar in less pronounced in Gymnogyps and more so in Cathartes and Coragyps. The scar is longer and pronounced in Sarcoramphus. The intermetacarpal tuberosity is low in Perugyps, similar to Vultur, Gymnogyps californianus, and Breagyps, and higher in Sarcoramphus, Cathartes, Coragyps, and G. kofordi Emslie 1988.
Tibiotarsus with tendinal furrow more centered than in Vultur, Gymnogyps, Sarcoramphus, Coragyps, and Cathartes.
Tarsometatarsus robust with distal external trochlea placed as low or lower than middle trochlea (external trochlea higher than middle in Vultur, Gymnogyps, Sarcoramphus, Coragyps, and Cathartes).
TABLE 1. Mandibular meseasurements (mm) of living Vulturidae in comparison with Perugyps diazi new genus and species. Measurement codes are: (1) symphysis length, (2) symphysis width at proximal end, (3) coronoid process height, (4) coronoid process-articular length, and (5) total length of mandible. All measurements are mean ± SD.
Genus etymology. From Peru, where the fossils were found, and gyps from Greek, masculine, vulture.
Species etymology. Named for Mr. Eusebio Díaz, in recognition of his contributions to Peruvian vertebrate paleontology.
Referred material. MUSM 205, 206, and 260 are from the Sacaco Sur locale while MUSM 204, 261, 263, and 423 are from the Montemar locale of the Pisco Formation (Fig. 1). Right mandible with distal symphysis, MUSM 261 (Fig. 3A); cervical vertebra, MUSM 263; sternal end of right coracoid, MUSM 205 (Fig. 3B); distal left ulna, MUSM 423 (Fig. 2C); proximal right carpometacarpus, MUSM 206 (Fig. 2B), distal left tibiotarsus, MUSM 260 (Fig. 4A); right tarsometatarsus, MUSM 204 (Fig. 4B).
FIGURE 3. (A) Right mandible with distal symphysis (MUSM 261) of Perugyps diazi new genus and species in dorsal (top) and lateral (bottom) views. (B) Sternal end of right coracoid (MUSM 205) of Perugyps diazi new genus and species in ventral (left) and dorsal (right) views. Scale bar = 1 cm.
FIGURE 4. (A) Distal left tibiotarsus (MUSM 260) of Perugyps diazi new genus and species in anterior view. (B) Right tarsometatarsus (MUSM 204) of Perugyps diazi new genus and species in anterior (left) and posterior (right) views. Scale bar = 2 cm.
Measurements. See Table 1 for mandibular measurements. Measurements that are approximate due to erosion on the bone are indicated by the ? symbol. Holotype right carpometacarpus (MUSM 213): total length, 147.2 mm; proximal breadth, 38.4 mm; least breadth and depth of shaft, 26.9 and 23.1 mm, respectively. Proximal right carpometacarpus (MUSM 206): proximal breadth, 40.2 mm. Distal left ulna (MUSM 423): distal breadth and depth, 17.8 mm and 24.9 mm, respectively. Distal left tibiotarsus (MUSM 260): distal breadth and depth, 27.6 mm and 26.2 mm, respectively. Right tarsometatarsus (MUSM 204): total length, ?141 mm; proximal breadth, 28.7 mm; least breadth 15.7 mm and depth of shaft 8 mm; middle trochlea breadth ?11.3 mm and depth ?14.7 mm; distal breadth, ?40 mm.
The Family Vulturidae is characterized by the presence of a deep and often pneumatic anterior carpal fossa in the carpometacarpus, which is not present or shallow in Ciconiidae and Teratornithidae (Emslie 1988b). Other characteristics for Vulturidae are a massive os metacarpale minus and majus with a broad distal symphysis, a long and proximally curved os metacarpalis alulare, with a rounded extensor process; a broad contour of the carpal trochlea, and rounded facets on the distal articular surface. The carpometacarpus of Perugyps (MUSM 206, 213) presents at least three clear condor characteristics including (1) a proximally curved process extensorius, (2) low intermetacarpal tuberosity, and (3) large size (Hertel 1992).
In addition to characters above in the generic diagnosis, further characters distinguish Perugyps diazi.
Mandible. In dorsal view, the distal symphysis of MUSM 261 (Fig. 3A) is distinctly longer than in Coragyps, Sarcoramphus, or Gymnogyps, exceeded in length only by Vultur; the symphysis is relatively broader in Perugyps compared to all living Vulturidae. The symphysis in Cathartes aura is proportionally the same length as in Perugyps. Vultur and Gymnogyps also have a longer and more pronounced (higher) proximal end and articular (Table 1). In addition, the ventral surface of the mandible in lateral view curves downward more sharply towards the distal end in Gymnogyps compared to Perugyps (Fig. 3A) and Vultur.
Cervical vertebra. MUSM 263 is more similar to Vultur than Gymnogyps in size, shape, and robustness. MUSM 263 also is similar in characters to Cathartes, though much larger. In anterior view, Perugyps has external borders of the prezygopophyses positioned at the same height as the diapophyses, similar to Sarcoramphus and Cathartes; these borders are relatively higher in Coragyps. No vertebrae of Breagyps or Geronogyps were available for comparison.
Coracoid. MUSM 205 (Fig. 3B) has an internal distal angle that is more robust, curved, and with a lower-hanging rim and the line for muscle attachment that is more distinct and extends farther up the shaft in Perugyps, compared to all living genera of Vulturidae. Geronogyps (ROM 12991, 12992, 12993) is more like Vultur in the sterno-coracoidal impression, pneumatization, and shaft of internal distal angle.
Ulna. MUSM 423 (Fig. 2C) has a very pronounced and robust process lateral to the internal condyle with a small pneumatic area at the base, similar to Vultur and Gymnogyps (less robust with no or little pneumatic area in Sarcoramphus, relatively robust with larger pneumatic area in Coragyps and Cathartes). The external condyle in internal view extends relatively farther up the shaft, and is narrower, in Gymnogyps than in Perugyps and Vultur. This condyle also is relatively narrower in Perugyps than in Breagyps and the internal condyle is more prominent in the latter.
Tibiotarsus. MUSM 260 (Fig. 4A) is more similar to Gymnogyps than Vultur in the morphology of the distal condyles; the tendinal opening is relatively higher (more proximal) on the shaft in Perugyps than in these two species or Coragyps, Cathartes, and Sarcoramphus. In anterior view, the intercondylar area is deeply grooved and symmetrical in Perugyps (area is shallow and asymmetrical in Vultur and Gymnogyps, very shallow in Cathartes). There is a distinct bony shelf on the internal side of the tendinal opening in Perugyps, similar to Gymnogyps (this shelf is small in Vultur and nearly absent in Coragyps). The external condyle is relatively more robust in Perugyps compared to Gymnogyps or Vultur. The tendinal groove passing below the supratendinal bridge is straight in Perugyps, Cathartes, and Sarcoramphus, but curved internally and proximally in Coragyps, Gymnogyps, and Vultur (see Campbell 1979). Geronogyps (ROM 13007) has a higher tendinal opening on the shaft, similar to Perugyps, as well as a large shelf on the internal side. The intercondylar area is deeper in Geronogyps than in all living vultures, but not as deep as in Perugyps. Perugyps does not have any obvious features that differ from Breagyps in this element.
Tarsometatarsus. MUSM 204 (Fig. 4B) has an anterior metatarsal groove that is deep and distinct, extending half way down the shaft (extends farther down the shaft in Vultur, Gymnogyps, Geronogyps, Hadrogyps Emslie 1988, and Pliogyps Tordoff 1959). The external border of this groove also is slightly larger than the internal in Perugyps, Vultur, and Coragyps; these borders are similar in size in Cathartes, Sarcoramphus, and Gymnogyps. The shaft is relatively robust as in Gymnogyps and Vultur, narrower in Coragyps, Cathartes and Sarcoramphus. The shaft also flares only slightly outward at the proximal and distal ends in Perugyps (shaft flares distinctly outward at ends in Vultur, Gymnogyps, Geronogyps, Breagyps, Hadrogyps, and Pliogyps; more columnar in Hadrogyps and Aizenogyps Emslie 1998). The tarsometatarsus of Aizenogyps toomeyae is relatively larger and more robust, with broader and deeper distal trochleae, than in Perugyps.
The Pisco Formation consists of tuffaceous sandy siltstones, medium and coarse-grained sandstones, shelly sandstones, and to a lesser extent, conglomerates, bedded tuffs, and coquinas that represent littoral environments that were partially protected and close to shore (de Muizon and DeVries 1985). Six vertebrate-bearing levels were identified by de Muizon and DeVries (1985), including those at Montemar and Sacaco Sur where fossils of Perugyps were recovered. The sediments at these two localities reflect a littoral paleoenviroment with protected beaches and reefs exposed to marine currents (Marocco and de Muizon 1988). Other avian families so far identified from the Pisco Formation include Spheniscidae, Sulidae, Phalacrocoracidae, Pelagornithidae, Laridae, Scolopacidae, Procellariidae and Diomedeidae (de Muizon 1981, de Muizon and DeVries 1985, Cheneval 1993, Stucchi 2003).
Perugyps is the eighth genus of fossil condors and condor-like vultures to be described. Of the other seven genera, three (Dryornis, Geronogyps, and Wingegyps) are known from South America (Brodkorb 1967, Campbell 1979, Alvarenga and Olson 2004). Wingegyps cartellei is a small enigmatic condor from the late Pleistocene of Brazil, no larger than a raven, but with characters strikingly similar to Gymnogyps (Alvarenga and Olson 2004). Dryornis pampeanus Moreno and Mercerat 1891 (early to middle Pliocene, Argentina) is not known by any elements shared with Perugyps and cannot be compared (Moreno and Mercerat 1891). In addition, an undescribed condor also from the middle Pliocene of Argentina is known by only a proximal ulna and radius (Tambussi and Noriega 1999) and is not comparable to Perugyps.
Other fossil condors include Hadrogyps aigialeus from the middle Miocene, California (Emslie 1988a), and Pliogyps charon Tordoff 1959 and P. fisheri Becker 1986 from the late Miocene and middle Pliocene, respectively, of Florida and Kansas (Tordoff 1959, Becker 1986). These two genera are smaller, condor-like vultures that represent a parallel lineage of vultures to the larger condors. Aizenogyps toomeyae was a large, robust condor from the Pliocene of Florida (Emslie 1998). Breagyps clarki is well represented by fossils from the late Pleistocene Rancho la Brea, and it is distinct in morphology from all other genera (Miller 1910, Miller and Howard 1938, Howard 1974, Emslie 1988b). One other fossil genus, Antillovultur Arredondo 1976 from the late Pleistocene of Cuba, is now considered to be congeneric with Gymnogyps (Emslie 1988b, Suárez 2000, Suárez and Emslie 2003). An indeterminate genus and species of large condor from the early Pliocene Lee Creek Mine, North Carolina, is known by a humeral end of a coracoid, distal tibiotarsus, and pedal phalanx (Olson and Rasmussen 2001). This material is too fragmentary to provide diagnostic characters in comparison to other condors, though the distal tibiotarsus (USNM 430883) has a relatively shallower intercondylar fossa compared with Perugyps (MUSM 260).
Perugyps diazi indicates that condors were present in South America by the late Miocene, at least 2.0 Ma earlier than suggested by Emslie (1988b), who proposed that condors may have arrived by the middle Pliocene and near the beginning of the Great American Biotic Interchange. In addition, Tonni and Noriega (1998) report a fossil of the living Andean Condor from the early Chapadmalalan (4 Ma), Río Quequén Salado (Buenos Aires), Argentina. Thus, it is now apparent that condors reached South America by the late Miocene to early Pliocene.
If condors did evolve in North America, then they were able to reach South America early in the evolution of this group. We hypothesize that an ancestral condor was able to expand southward following coastal corridors on the western side of the Andes. The California Condor can range hundreds of kilometers in a single day, at ground speeds up to 70–95 kph (Snyder and Snyder 2000), while the Andean Condor can reach speeds averaging 65 kph (McGahan 1971) and can fly 200 km across deserts from the Andean foothills to the coast to forage in a single day. Moreover, Pennycuick and Scholer (1984) found that the latter species is almost entirely dependent on slope uplifts to sustain prolonged soaring flight. We believe these flight capabilities of condors, along with coastal winds and updrafts common along the western slope of the Andes, may have allowed an ancestral condor to cross the marine barrier that existed between North and South America (the submerged Panamanian land bridge) in the late Miocene and early Pliocene.
During the late Miocene/early Pliocene, the Peruvian coast was characterized by a diverse assemblage of marine mammals and birds (de Muizon and DeVries 1985, Cheneval 1993, Stucchi 2003). This fauna is associated with remains of Perugyps and we believe that this condor fed on coastal carcasses of marine mammals, and perhaps took live chicks of seabirds, similar to the Andean Condor"s habits along the north coast of Peru today (Pennycuick and Scholer 1984, Wallace and Temple 1987). As no other scavenging species are known among the fauna of the Pisco Formation, it is reasonable to assume that Perugyps filled this niche. We expect that additional material of this condor will be recovered from vertebrate-bearing units of the Pisco Formation.
ACKNOWLEDGMENTS
We thank Messrs. Ana María and Santiago E. Stucchi, Mario Urbina, Rodolfo Salas and Thomas DeVries for their important contributions to this research. S. Olson and J. Dean allowed access to comparative collections at the U. S. National Museum, Washington, DC. David Willard and John Bates allowed access to comparative collections at the Field Museum Natural of History, Chicago. We also thank Paul Velazco, Gonzalo Cárdenas, Judith Figueroa, Michael McGowan and José Tello for their help in Chicago, and S. Olson, H. James and T. DeVries for their help in Washington DC. This paper was improved by comments from K. Campbell and S. Olson.
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Autor:
Marcelo Stucchi
Steven D. Emslie
1Asociacion Ucumari. Jr. Los Agrologos 220, Lima 12, Peru
2Department of Biological Sciences, University of North Carolina, Wilmington, NC 28403
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