Archaehieraxinae, Mather, Ellen K., Lee, Michael S. Y., Camens, Aaron B. & Worthy, Trevor H., 2021

Mather, Ellen K., Lee, Michael S. Y., Camens, Aaron B. & Worthy, Trevor H., 2021, An exceptional partial skeleton of a new basal raptor (Aves: Accipitridae) from the late Oligocene Namba formation, South Australia, Historical Biology 34 (7), pp. 1175-1207 : 6

Subfamily: Archaehieraxinae subfam. nov.

Type genus: Archaehierax gen. nov.

Remarks

The fossil is identified as an accipitrid due to the following combination of characters: Skull – Rostrum deep and narrow, with hooked tip and a large, broad nasal aperture; Tibiotarsus – Pons supratendineus ossified, aligned steeply transversely, medially placed, with unbranched canalis tendinosus, and distal condyles much wider than craniocaudally deep; Tarsometatarsus – Robust, with monosulcate hypotarsus, the lateral and medial hypotarsal crests widely separated and trochleae metatarsorum splayed both medially and laterally, and dorsally arched in distal view; Foot – Four digits with raptorial unguals, those of digits 1 and 2 relatively large; Digit IV – phalanges 2 and 3 are very short compared to phalanx 4.

Thefossilcanbeexcludedfrom Falconiformes (Falconidae) and the other families of Accipitriformes ( Cathartidae , Sagittariidae , Pandionidae ) by the morphology of the tarsometatarsal hypotarsus cristae and sulcus. The cristae are fused or partially fused together to enclose thesulcus in Cathartidae , Sagittariidae , and Pandionidae , while in Falconidae the medial crista isconnected to the shaft by a ridge that extends two-thirds of its length, features that are absent in the fossil.

Diagnosis

Accipitrids in which the following autapomorphic features are found: the pila medialis of the sternum dorsally separates two deep pneumatic fossae, the humerus has the caput humeri only slightly elevated proximally past the tuberculum ventralis, the tip of the processus procoracoideus of the coracoid sharply curves inwards ventrally towards the medial face of the bone, the tibiotarsus has the lateral/distal retinaculum scar in a deep fossa, the tarsometatarsus is relatively elongate with narrow trochleae metatarsorum that are separated by wide incisurae, and the incisura for the m. flexor hallucis brevis tendon is large, distinct, and extends distal to the fossa metatarsi I. In addition to this, the following features occur: the rostral tip of the rostrum is hooked below the tomial margin at a relatively shallow 30–40° angle, the quadrate has a deep, distinct foramen pneumaticum caudomediale, and the sternum has the apex carinae displaced caudally from the base of the spina externa.,