Genus Buteogallus Lesson, 1830, Traité d'Orn., livr. 2, p. 83. Type, by monotypy, Buteogallus cathartoides Lesson, 1830 = Falco aequinoctialis J. F. Gmelin, 1788.

Synonym. Amplibuteo Campbell, 1979: 77; type species by original designation Amplibuteo hibbardi Campbell, new synonymy.

Characters of the tarsometatarsus described by Campbell (1979: 77) as diagnostic of ‘Amplibuteo', but recorded by him as present in Buteogallus (= ‘Harpyhaliaetus' and ‘Heterospizias Sharpe', see diagnosis of ‘Miraquila' Campbell 1979: 74), include: ‘(1) inner calcaneal ridge of hypotarsus projecting posteriad at approximately 60–70° to vertical axis of shaft [= ‘Harpyhaliaetus']; (2) intercotylar area elevated slightly [= ‘Heterospizias' and Buteogallus]; (3) edge of shaft external to outer calcaneal ridge of hypotarsus without ridge [more similar to ‘Harpyhaliaetus’, character of specific value, variable in Buteogallus, see Suárez & Olson 2009b: 250]; (4) anterior metatarsal groove moderately deep [= ‘Heterospizias' and Buteogallus]; (5) internal anterior metatarsal ridge only slightly developed [= Buteogallus]; (6) attachment of tibialis anticus not separated from external anterior metatarsal ridge by groove [= ‘Harpyhaliaetus' and ‘Heterospizias']; (7) middle trochlea short, turned significantly externally in anterior view [= ‘Harpyhaliaetus']; (8) internal trochlea rotated posteriad such that posteromedial edge is at same level as posterolateral edge of middle trochlea [= ‘Heterospizias' and Buteogallus]; (9) internal trochlea projecting distad beyond middle trochlea and rotated significantly externally in anterior view [= ‘Harpyhaliaetus']; (10) internal trochlea with distinct angular proximolateral projection [= ‘Harpyhaliaetus' and ‘Heterospizias'].' Therefore, the extinct taxa currently placed in ‘Amplibuteo’ are treated herein under Buteogallus, as B. woodwardi (L. Miller, 1911) new comb., B. hibbardi (Campbell, 1979) new comb., and B. concordatus (Emslie & Czaplewski, 1999) new comb., which are all members of the Buteogalline radiation among extinct Accipitridae from America (cf. Olson 2007, Suárez & Olson 2008, 2009b). Specimens of the new species also replicate the general skeletal morphology present in the living B. solitarius (or vice versa), being part of a small (apparently monophyletic) assemblage of allopatric-allochronic fossil species that includes B. concordatus and B. woodwardi, from North America, and B. hibbardi from South America.

Holotype.—Left tarsometatarsus lacking proximal end, USNM PAL 299573 (Figs. 1A–E, 2A;not ‘USNM 244573' [lapsus calami], as reported by Olson & Hilgartner 1982: 28). Collected by Charles Woods under 60 cm of red earth, at the type locality, on 24 April 1978. This specimen was incorrectly cited as ‘a tarsometatarsus lacking its distal end (USNM 244573, from Cueva de las Abejas)’ by Steadman et al. (2019: 328).

Paratype.—Cueva de Sandoval (Sandoval III low deposit), c.4 km south of Vereda Nueva, Caimito municipality, Artemisa (formerly La Habana) province, Cuba: partial skeleton WS 365, with one cervical (axis) and three thoracic vertebrae, seven fragments of ribs, fragmentary pelvis, proximal fragmentary right humerus, distal fragments of left humerus, segment of shaft of left ulna, left fragmentary femur without distal end, proximal and distal fragmentary ends of right femur, shaft of left tibiotarsus, proximal right fibula, left tarsometatarsus (lacking inner calcaneal ridge, part of the proximal end of the metatarsal facet, wing of trochlea II and posterior surface of trochlea III) (Fig. 2B), left digit I-phalanx 1 and 2, left digit III-phalanx 2 and 3, right digit III-phalanx 4, right digit IV-phalanx 4. Collected by WS on 2 March 1995. Quaternary, probably late Pleistocene, but not directly dated (see Suárez 2000). For illustrations and description see Suárez (2004: 121–123, Figs. 1–2).

Measurements of holotype.—Total length as preserved: 124.9 mm; proximal width at distal level of tubercle for tibialis anticus: 17.0 mm; width of shaft at midpoint: 13.2 mm; minimum width of shaft: 11.8 mm; minimum width of shaft at proximal end of metatarsal facet: 13.0 mm; depth of lateral side at proximal end of metatarsal facet: 9.8 mm; distance from proximal edge of metatarsal facet to inner inter-trochlear notch: 30.3 mm; distal width: 27+ mm; width of trochlea III: 8.3 mm; depth of trochlea IV: 12.2 mm (Table 1).

Diagnosis.—Resembles B. woodwardi and B. hibbardi in size and general morphology, but tarsometatarsus more robust, with shaft expanded at distal end, and trochleae relatively shorter in B. irpus.

Measurements of paratype.—See Suárez (2004: 123–124, Table 1, Fig. 3), Table 1.

Type locality and age.—Cueva de las Abejas (18°01′N, 71°40′W; c.20 m), near Cabo Rojo, 8 km south-east of Pedernales, 1.5 km north of Highway 44, Pedernales province, Dominican Republic. Quaternary, probably late Pleistocene, but not directly dated (see Olson & Hilgartner 1982: 28, Steadman et al. 2019: 321).

Etymology.—From Latin irpus, = wolf, in reference to the ecological role played by this large raptor in controlling the regional ‘megafauna’ on the two largest islands of the Greater Antilles, occupying the ecological niche of a carnivorous mammal (cf. Arredondo 1976, Morgan et al. 1980).

Status.—Extinct, known only from fossil material.

Description.—The skeleton of B. irpus sp. nov. (Figs. 1–2; see Suárez 2004: Figs. 1–2, Suárez & Olson 2008: Fig. 1) is partially represented by fragmentary material, with the tarsometatarsus best preserved and more diagnostic of the known elements (see Olson & Hilgartner 1982: 28, Suárez 2004: 121). Both tarsometatarsi under study (holotype and paratype, see above) represent adults, probably of different sexes. These fossils are similar in general morphology to the equivalent elements in the extant B. solitarius and the Quaternary extinct B. woodwardi and B. hibbardi, but B. irpus is much larger and robust than material available of the living species (Table 1). All other modern Buteogallus examined, including B. anthracinus, B. gundlachii, B. aequinoctialis (see Olson 2006, for discussion of some skeletal elements of this species), B. meridionalis and B. urubitinga, are much smaller than B. irpus sp. nov., and therefore do not require further comparison. B. irpus differs from the extinct B. woodwardi (Fig. 2C) and B. hibbardi (see Campbell 1979: Fig. 28 A(i)–(iii) = holotype ROM 16905) in having tarsometatarsus with stouter shaft (relatively thinner, more gracile in B. woodwardi and B. hibbardi), distal end flattened and more expanded bilaterally, especially above the trochleae (distal end thinner, less expanded in B. woodwardi and B. hibbardi), trochlea II short, poorly projected distad (longer, projected more distad in B. woodwardi and B. hibbardi), trochlea III small, nearly squared, with thin groove and more laterally angled (larger, less squared, with wide groove and less bent laterad in B. woodwardi and B. hibbardi). Trochleae deep and massive in distal view (trochleae shallower and less massive in B. woodwardi and B. hibbardi). The new species is larger than B. concordatus (see Suárez 2004: 122) from the late Pliocene (late Blancan) of Florida and Arizona which is the smallest of the former ‘Amplibuteo’ species (see Emslie & Czaplewski 1999).

Compared with tarsometatarsi of the continental extinct species B. daggetti and B. terrestris (the latter known from incomplete specimens), both represent more gracile species, with the former (c.40% larger than the average size of B. meridionalis, see Olson 2007) being the longest and more gracile of the extinct Buteogallus compared. The tarsometatarsus of B. daggetti differs from the same elements in B. irpus in being extremely elongated, gracile and straight, with a deep anterior metatarsal groove, tubercle for tibialis anticus well centred on the mid-line of the shaft and well separated from the anterior external metatarsal ridge by a wide groove (see Olson 2007: Figs. 1C, 2C, Suárez & Olson 2009b: Fig 1D). B. daggetti and B. terrestris do not exhibit the characteristic expanded distal end, or the reduction of the trochlea III (see Campbell 1979: Figs. E (i)–(ii), Olson 2007: Figs. 1C, 2C), diagnostic of B. irpus sp. nov. The extinct B. fragilis and B. royi are distinct, apart from their much smaller size when compared to B. irpus sp. nov., in having more slender or gracile tarsometatarsi, anterior and posterior metatarsal grooves deeper, and the tubercle for tibialis anticus more proximad (see Suárez 2020: Figs. 9–10).

B. irpus differs from comparable elements in extinct B. borrasi from Cuba, in having: humerus (see Suárez 2004, Figs. 2A–C, Suárez & Olson 2008, Fig. 2A) larger and robust, proximal head less projected, capital groove wider and deeper, and ligamental furrow larger (smaller and gracile, head more projected, capital groove thin and shallow, and ligamental furrow smaller in B. borrasi). Ulna (in B. irpus sp. nov. known only by a segment of middle shaft, see Suárez 2004: Fig. 2D) robust, with better-developed inner and outer papillae of secondaries (more gracile, both papillae smaller or less developed in B. borrasi). Femur (see Suárez 2004: Fig. 2F–G) also more robust, with attachment of round ligament smaller and deeper (expanded, shallow and vertically oriented in B. borrasi), shaft cylindrical in cross section, less compressed anteroposteriorly at ends (more ovoid and compressed in B. borrasi), prominent anterior intermuscular line, more distally extended along the mid-line of the shaft (less developed, more laterally located and restricted to the proximal half of shaft in B. borrasi, see Suárez & Olson 2008: Fig. 3A), pneumatic foramen large and oval-shaped (consistently smaller and rounded in B. borrasi), and large condyles (smaller in B. borrasi). Tibiotarsus (in B. irpus sp. nov. known only by a proximal segment of shaft, see Suárez 2004: Fig. 2I) robust with fibular crest short and greatly projected (gracile, fibular crest larger but less projected in B. borrasi, see Suárez & Olson 2008: Fig. 3E). Tarsometatarsus (Figs. 1–2; see Suárez 2004: Fig. 2J–L, Suárez & Olson 2008: Fig. 1) shorter, wider, with robust shaft well expanded above the trochleae, and shallow anterior and posterior metatarsal grooves (gracile and slender, not expanded above the trochlea with deeper grooves in B. borrasi). Trochleae distally placed on shaft, trochlea III short, with marked lateral orientation. Phalanx I-digit 1 (see Suárez 2004: Fig. 2M) shorter, robust and not too curved downward (longer, less robust and more curved in B. borrasi). Ungual phalanges less curved than in B. borrasi (see Suárez 2004: Fig. 2N–O, Suárez 2020: Fig. 8H).

Compared with the holotype tarsometatarsus of Titanohierax gloveralleni (MCZ 2257) from the Bahamas (Fig. 2E), the same element in B. irpus is slightly smaller, shorter and robust, and less flattened, as it is less compressed anteroposteriorly at the distal end, the trochleae are shorter (trochlea II unknown in T. gloveralleni), especially trochlea IV, in which the lateral rim (distal view) is also less pronounced (longer, more projected distally, with lateral rim pronounced in T. gloveralleni), posterior metatarsal groove shallow (much deeper in T. gloveralleni) and metatarsal facet not as highly placed, or proximal (see Wetmore 1937: 430, Olson & Hilgartner 1982: 28).

B. irpus is considerably smaller compared to the huge Cuban species Gigantohierax suarezi, with the following characters (cf. Suárez 2004: 122–123): femur shaft straight, nearly circular in cross-section (curved anteroposteriorly, greatly compressed in G. suarezi), anterior intermuscular line centred on shaft (lateral in G. suarezi), proximal and distal end not expanded (greatly expanded in G. suarezi), poor pneumaticity proximad (great pneumaticity in G. suarezi), head thinner and rounder with long neck, attachment of round ligament smaller (head broad or expanded, with short neck and attachment of round ligament large, vertically oriented, in G. suarezi), iliac facet wide (thin in G. suarezi), distally the rotular groove is shallow (deep in G. suarezi), and reduced but deeper popliteal area (large and shallow in G. suarezi). The tarsometatarsus is less compressed anteroposteriorly, being more triangular in cross-section (more compressed, flatter or less triangular in G. suarezi), and external proximal half of shaft nearly flat (convex in G. suarezi). Differs from G. itchei (Fig. 2D) also from Cuba, in having femur smaller, not flared or flattened (compressed anteroposteriorly) at proximal end, with less pneumaticity proximad (wider, flaring greatly proximad, with a distinctive concavity formed by the most proximal pneumatic foramen in G. itchei). The tarsometatarsus also lacks the diagnostic thinner and deep anterior metatarsal groove on a flattened shaft, with less anteroposterior compression at the distal end, resulting in a narrower distal end compared to G. itchei (see Suárez 2020: 26–27). For additional comparisons, descriptions, measurements and illustrations of fragmentary elements of the paratype skeleton WS 365 with other taxa, including B. fragilis and extinct West Indies accipitrids such as B. borrasi, Titanohierax gloveralleni and Gigantohierax suarezi, see Suárez (2004: 121–124, Figs. 1–3, Table 1) and Suárez & Olson (2008: Fig. 1).