Gigantohierax itchei, Suárez, 2020

Suárez, William, 2020, The fossil avifauna of the tar seeps Las Breas de San Felipe, Matanzas, Cuba, Zootaxa 4780 (1), pp. 1-53 : 25-27

† Gigantohierax itchei sp. nov.

Itche’s Eagle; Águila de Itche

( Figure 11 : J–P; Table 6)

Holotype. Distal third of right tarsometatarsus without trochlea metatarsi IV, MNHNCu 75.4869. Collected by members of the Departamento de Geología y Paleontología, MNHNCu, in San Felipe II, during field expedition to the type locality in 1998.

Measurements (mm) of holotype. Total length as preserved: 69.5; least width and depth of shaft: 12.0–9.0; distal width from the wing of trochlea metatarsi II to the outer rim of trochlea metatarsi III: 23.5; width and depth of trochlea metatarsi III: 8.4–10.1 (see Table 6).

Paratype (topotype). San Felipe II: Proximal end of fragmentary right femur (MNHNCu 75.4725) .

Measurements (mm) of paratype. Femur ( G. suarezi in parentheses): depth of neck: 13.7 (19.0); width and depth at level of the distal end of the trochanteric ridge: 18.5 (23.9)–12.2 (16.2); length from distal point of the pneumatic foramen to the distal end of the trochanteric ridge: 19.5 (15.5).

Etymology. After my dear friend Irving “Itche” Himel, Toronto, Canada, for his sincere friendship and unconditional support during my paleontological studies in his country.

Diagnosis. The smallest species in the genus Gigantohierax .

Description. Specimens of Gigantohierax itchei sp. nov. are ~29% smaller than the equivalent elements in the skeleton of G. suarezi (mean 17.63%, range 9.27–26.84% in between-species of large Accipitridae , see Holdaway 1990). The femur ( Fig. 11 J–L) in anterior view has a large pneumatic depression (= proximal pneumatic foramen), located proximomediad to the distal pneumatic foramen (similar, greater pneumaticity and presence of perforations in the basal wall by some very small foramina in G. suarezi ); small distal pneumatic foramen, apparently semitriangular, according to the preserved portions (larger, semitriangular in G. suarezi ); the distance between the distal margin of the distal pneumatic foramen and the distal end of the trochanteric ridge is very large (smaller in G. suarezi ). In posterior view, the proximal surface is irregular, being inflated (or bulky) in its center, as result of the high development of the obturator ridge (flattened and pneumatic surface, with little or no development of the obturator ridge in G. suarezi ). The tarsometatarsus ( Fig. 11 M–P) has a shaft proportionally thinner (anterior and/or posterior view), less flattened or compressed (lateral and/or medial view) than in the largest species (more flattened and compressed, being wide in G. suarezi ). In anterior view, it is deeply excavated by a distinctive, very deep and narrow anterior metatarsal groove, which extends well distad (groove much less excavated or extended distad, with anterior surface of the shaft more flattened or convex in G. suarezi ). The distal foramen is large (proportionately smaller in G. suarezi ), trochlea metatarsi III with very wide and grooved articular surface (relatively narrow in G. suarezi ). In posterior view, the posterior metatarsal groove is slightly deeper, but less extended distally (superficial, ending more distad in G. suarezi ); crista plantaris medialis better defined (rounded, less defined in G. suarezi ); larger distal foramen (relatively smaller in G. suarezi ); fossa supratrochlearis plantaris shallow (deep and expanded in G. suarezi ); broadly furrowed trochlea metatarsi III (narrow groove in G. suarezi ) with very narrow and laterally oriented inner ring (much wider and mediad in G. suarezi ); internal side of this last trochlea very excavated medially (less excavated, more superficial in G. suarezi ). In cross section, the shaft is squarer, furrowed by the deep anterior metatarsal groove (more triangular, less excavated in G. suarezi ).

Comparisons with other Antillean and continental related fossil accipitrids. Gigantohierax itchei sp. nov. is a larger species compared with Buteogallus borrasi , “ Amplibuteo ” woodwardi, or “ A ” hibbardi, being close in size to Titanohierax gloveralleni of the Bahamas ( Table 6). Gigantohierax itchei sp. nov. differs from all these species by having a wider femur (unknown element in T. gloveralleni ), flaring greatly (anterior and/or posterior view) proximad; presence of distinctive concavity formed by the most proximal pneumatic foramen; second (more distad) pneumatic foramen small and semitriangular in shape. In posterior view, the proximal surface is flattened and expanded, not rounded. In lateral view, this element is greatly compressed in anteroposterior direction, being almost flat and the trochanteric ridge is narrow and long distad. Tarsometatarsus ( Fig. 11 M–P) also more compressed anteroposteriorly, being wide and flat, especially at the distal end; very deep anterior metatarsal groove that extends well down (distad) on shaft; distal foramen large; surface between this last foramen and the external border very wide and rounded (very thin and acute in T. gloveralleni ; similar in the other species); trochleae flaring abruptly and distally on shaft; trochlea metatarsi III short, wide, and with a distinct wide groove (longer, thinner, with thin groove in T. gloveralleni ; proportionately similar in the remaining species compared); in lateral view, the lateral border or surface is thinner (by the great anteroposterior compression) and rounded, especially at the distal end (wide, concave because it is deeply grooved, less rounded distally in B. borrasi ; very wide and flat even distally, only slightly grooved in T. gloveralleni ; intermediate in characters in “ A ”. woodwardi and “ A ”. hibbardi); internal (inner) side forming a thin, acute or sharp border, specially above the level of the metatarsal facet. In posterior view, the poste- rior metatarsal groove is shallow, crista plantaris medialis and crista plantaris lateralis with poor development; metatarsal facet higher (proximal) on shaft; distal foramen ovoid and much larger; trochlea metatarsi III wide, widely grooved, with short articular surface and distinct long neck at base (wide and also widely grooved, long surface without neck in B. borrasi ; much thinner and less grooved, much longer or extended posterior surface without neck in T. gloveralleni ; intermediate in characters in “ A ”. woodwardi and “ A ”. hibbardi); in distal view, the later trochlea is wide but not deep, being squared in morphology (much thinner, very deep, rectangular in T. gloveralleni ); outer rim very wide.

Comments. In the initial stages of the process of identification of the specimens described here as Gigantohierax itchei sp. nov. the author considered as the first hypothesis the logical possibility that the holotype of this species, due to its similar size, could represent Titanohierax gloveralleni , an extinct and large buteonine hawk unknown in Cuba so far, and described from the nearby Bahamas ( Wetmore 1937; Olson & Hilgartner 1982). After direct comparisons with the type series of the Bahamian taxon, this hypothesis was quickly dismissed. Titanohierax is closer to the genus Geranoaetus (and Buteo Lacépède ) than to Buteogallus ( Olson & Hilgartner 1982; Suárez & Olson 2007), or Gigantohierax— which shares some characters with Buteogallus (see descriptions above)—, as seen in the anatomy of its tarsometatarsus, especially on both sides of the shaft and in the trochleae. After comparisons and explorations on the osteology of both species described in the extinct genus “ Amplibuteo ” Campbell (see Campbell 1979), it seems that those must be more accurately placed under Buteogallus (see Olson 2007; Suárez & Olson 2009b).

Figures

FIGURE 11. Gigantohierax suarezi: Left humerus (MNHNCu 75.4722) in anterior/cranial (A) and posterior/caudal (B) views; left carpometacarpus (MNHNCu 75.4723) in dorsal (C) view; right tarsometatarsus (MNHNCu 75.4728) in distal (D), anterior (E), medial (F) and posterior (G) views; phalanx I, left digit I, in dorsal (H) view; ungual phalanx, left digit I (MNHNCu 75.4731) in lateral (I) view. Gigantohierax itchei sp. nov.: Right femur (Paratype, MNHNCu 75.4725) in anterior (J), posterior (K) and lateral (L) views; right tarsometatarsus (Holotype, MNHNCu 75.4869) in anterior (M), medial (N), posterior (O) and distal (P) views. Scale = 2 cm.