Pinpanetta, Worthy, 2009

Worthy, Trevor H., 2009, Descriptions and phylogenetic relationships of two new genera and four new species of Oligo-Miocene waterfowl (Aves: Anatidae) from Australia, Zoological Journal of the Linnean Society 156 (2), pp. 411-454 : 416-417

GENUS PINPANETTA GEN. NOV.

Type species: Pinpanetta tedfordi sp. nov.

Diagnosis: Oxyurines in which humeri have the following unique combination of characters: incisura capitis (capital groove) forming either a very shallow or no notch in proximal profile; ventral pneumotricipital fossa closed or nonpneumatic, not extending under median crest; dorsal pneumotricipital fossa narrower than ventral one; dorsal tubercle about as wide as long, not elongate; attachment of M. scapulohumeralis cranialis (supraspinatus) an elongate ridge, extending distally to point level with junction of bicipital crest and shaft; tuber. supracondylare ventrale (facet for anterior ligament) buttressed cranially; ectepicondylar prominence distinct; and attachment of pronator brevis is an isolated pit on ventral facies.

Etymology: After Lake Pinpa and the Pinpa Local Fauna from which many specimens derive, and for ‘netta’, duck in Greek.

Description and comparison: Within Anatidae , lack of a well-developed notch at the ventral end of the capital groove, as shown by Pinpanetta , is found only in dendrocygnines, anserines, and tadornines. Thalassornis, Biziura , Oxyura, Nomonyx , Stictonetta , Malacorhynchus , Mionetta , and Manuherikia are all more derived with their proximal profile interrupted by a distinct notch at the ventral end of the capital groove. The relatively narrow dorsal pneumotricipital fossa in Pinpanetta is shared with dendrocygnines, anserines, and tadornines. Within oxyurines, Mionetta , Manuherikia , Thalassornis, Biziura , Stictonetta , and Malacorhynchus also retain the narrow dorsal pneumotricipital fossa, but in Oxyura and Nomonyx the fossa is relatively wider. Pinpanetta shares the derived condition of a closed or nonpneumatic ventral pneumotricipital fossa with all oxyurines except Stictonetta and Nomonyx , in which taxa the fossa is pneumatic. In Pinpanetta , the attachment scar for m. latissimus dorsi posterioris commences proximal to and links to the end of the deltoid crest before extending down the shaft, as in Anseranas , some Dendrocygna species , and Cereopsis . This character state is therefore probably the primitive condition, and is shared with Mionetta , Thalassornis , Oxyura , and Nomonyx . In the assumed more derived states there is no connection of the scar with the deltoid crest, whether the scar begins anterior of the end of the crest, e.g. Biziura and Manuherikia , or commences level with its end e.g. Stictonetta , Malacorhynchus , tadornines, and most anatines. The tuber. ventrale slightly overhangs the ventral pneumotricipital fossa in Pinpanetta , rather than being directed proximally. This is a derived condition accentuated in most diving anatids, e.g. Biziura and Oxyura , and so differs from Stictonetta and Mionetta where the ventral tubercle is directed proximally. The dorsal tubercle is about as wide as long, as seen in Anseranas , Dendrocygna , anserines, and some oxyurines. The derived state (an elongate tubercle) is seen in other oxyurines (some Oxyura species , Nomonyx , Stictonetta , Manuherikia , and Dunstanetta ), most tadornines and all anatines. An elongated attachment of the supraspinatus is derived relative to a short attachment characteristic of Anseranas , Dendrocygna species , and anserines. In Pinpanetta , the attachment is as elongate as in Manuherikia , Thalassornis , Oxyura, Biziura and Malacorhynchus , but it is much shorter in Stictonetta, Nomonyx , and Mionetta .

Distally, in Pinpanetta , the facet for the anterior ligament is cranially buttressed, as in Mionetta , Manuherikia , Dunstanetta , Malacorhynchus , Stictonetta , and Nomonyx , and so is derived relative to the unbuttressed state where the facet is parallel to the shaft in Anseranas , Thalassornis, Biziura , and Oxyura . The space between the facet for the anterior ligament and the dorsal condyle is wider than this facet, versus narrower in Thalassornis and Dendrocygna bicolor , which latter state is regarded as more primitive ( Woolfenden, 1961). In Pinpanetta , the sulcus scapulotricipitalis (scapulotricipital groove) extends from the caudal surface around the distal margin, as in most oxyurines, tadornines and anatines, and is therefore derived compared to Anseranas , Cnemiornis and Biziura , which either lack or have a barely defined scapulotricipital groove caudally, and to Dendrocygna , Thalassornis and some anserines, where the groove exists only on the caudal face. Although the epicondylus dorsalis is well developed and dorsally prominent level with the proximal margin of the dorsal condyle in Pinpanetta , a distinct ectepicondylar prominence of similar or relatively larger size to that in Malacorhynchus is also present. A distinct ectepicondylar prominence is present in Anseranas , anserines and Dendrocygna , and so its presence in Pinpanetta is a retained plesiomorphy shared with Thalassornis and Stictonetta , but the derived condition (lack of ectepicondylar prominence) is found in Oxyura, Nomonyx, Biziura , most tadornines, and all Anatinae. Pinpanetta has the attachment of the pronator brevis (sensu Howard, 1929) in an isolated pit on the ventral facies of the ventral epicondyle, thus distinguishing it from Thalassornis , Oxyura, Nomonyx, and Biziura which have a derived state with the attachment area fused with the ventral margin of the facet for the anterior ligament. The brachial fossa is elongate, with well-defined margins, is separated from the ventral margin by a narrow rounded ridge, and lacks secondary deepening distoventrally, as in Manuherikia . In Stictonetta , the fossa is poorly defined and flat.