Gracanicanetta happi, Bochenski & Happ & Salwa & Tomek, 2025

Gracanicanetta happi sp. nov.

Figures 1 View FIGURE 1 , 2A View FIGURE 2 , 3A, 4 View FIGURE 4 , 5A, B, D View FIGURE 5 , 6A, B View FIGURE 6

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Etymology. The species is named after Helga and Friedrich Happ, herpetologists and donors of the fossil, who dedicated their lives to the conservation of reptiles and amphibians of Carinthia, southern Austria.

Holotype. ISEA AF / GRA1 ( Figures 1 View FIGURE 1 , 2A View FIGURE 2 , 3A, 4 View FIGURE 4 , 5 View FIGURE 5 , 6A, B View FIGURE 6 ), partly articulated, nearly complete skeleton on a slab from which os carpi ulnare has been removed and is visible as a 3D object; housed at the Institute of Systematics and Evolution of Animals , Polish Academy of Sciences, Krakow, Poland.

Type locality and horizon. Gračanica open-cast lignite mine, still utilized commercially, situated in the Bugojno basin, between Gornji Vakuf and Donji Vakuf, central Bosnia and Herzegovina; GPS coordinates using WGS84 datum: 43.997662° N, 17.518516° E (Mandic et al., 2016). The age of the Gračanica mine deposits is estimated to be Early-Middle Miocene, late Langhian, 16-13.5 Ma, however, the dating is still considered to be contentious (Göhlich and Mandic, 2020). The specimen was found by miners during their working routine in the lower half of the 40 m thick deposits, rich in lignites (Göhlich and Mandic, 2020, fig. 1c) GoogleMaps .

Diagnosis. As for the genus.

Measurements. Measurements (in mm) including total length (TL) and others: coracoid, medial length ca 36.7; scapula TL, 46.2; humerus TL, 68.0, proximal width, 15.9, distal width, 10.5; ulna TL, 59.7; carpometacarpus TL, 39.1, proximal width, 9.6; phalanx proximalis digiti majoris TL, 17.6; femur TL, ca 36.4.

Description and Comparison

Skull and mandible. The skull is visible in ventrolateral view ( Figures 1 View FIGURE 1 , 2A View FIGURE 2 ). As in some extant Mergini (e.g., Bucephala , Clangula ) the beak is wide and significantly shorter than the braincase. Other extant Mergini (e.g., Melanitta ), Tadornini (e.g., Tadorna ), Aythyini ( Aythya and Netta ), Dendrocygninae ( Dendrocygna ) and Oxyurinae ( Oxyura ) also have wide beaks, but the length of their beaks is similar to the length of the braincase. The beaks of extant Anatini are usually slightly narrower but like in the Miocene Mionetta blanchardi and Lavanttalorins hassleri, their length is also similar to the length of the braincase. Completely different beaks (extremely narrow and very long) are observed in extant Mergus and Mergellus . As in derived Anatinae (i.e., Anatini, Aythyini, Mergini) and Tadornini, the preorbital (lacrimal) region of the skull is elongated; in Mionetta and Mioquerquedula , and more primitive extant Anatidae such as Dendrocygninae , Thalassornis , Biziura ), this region is shortened. As in extant anseriforms, the foramina neurovascularia are visible at the end of the beak and mandible. As in extant Anatidae , a long and rostrally projecting processus postorbitalis can be distinguished within the crushed braincase. The articular part of the mandible bears the processus medialis and the long processus retroarticularis which is typical of all anatids.

Sternum. The sternum is visible in dorsal view ( Figures 1 View FIGURE 1 , 3A). Although the right part of the sternum is partially obscured by the pelvis, the sternum was wide in relation to its length. Similar sternum proportions are observed in extant Mergini (except Mergus and Mergellus ) and Aythyini. Ducks belonging to Anatini, Tadornini, Oxyurini and Dendrocygnini have a more elongated sternum. As in most extant anatids but unlike Oxyura , the pila coracoidea forms a thickened ridge (Worthy and Lee, 2008: character 34). The remaining details of the rostrum sterni are not visible because they are covered by crushed vertebrae.

Coracoid. Coracoids are visible in dorsal view; the right one is complete but partially obscured by other bones, and the left one shows only a fragment of the shaft ( Figures 1 View FIGURE 1 , 4 View FIGURE 4 ). In length, the coracoid is similar to that of extant Spatula querquedula but its shaft is more massive and wider. As in Chenoanas , the medial edge of the shaft is straight and does not deviate medially; in Lavanttalornis, the omal section of the shaft inclines strongly medially. As in Mergini and part of Aythyini but unlike Mioquerquedula minutissima , Manuherikia lacustrina , Aix praeclara , Anas kurochkini , and extant Anatitni and Tadornini, the plane through the depth of the acrocoracoid is subperpendicular to the plane of extremitas sternalis (Worthy and Lee, 2008: character 45). The processus acrocoracoideus projects only slightly beyond the medial edge of the shaft, which distinguishes it from Chenoanas , Dunstanetta , Pinpanetta , Caerulonettion natator , Matanas enrighi , Aix praeclara , Mioquerquedula minutissima , Mioquerquedula soporata , Mioquerquedula palaeotagaica , Protomelanitta gracilis , and many extant taxa including Anatini and Aix . Unlike Dunstanetta , Aythya molesta, Tagayanetta palaeobaikalensis, Anas kurochkini and extant Anas s.l., facies articularis clavicularis does not bear a distinct notch in its caudal margin although its surface is slightly concave. There is a moderately deep depression in the dorsal part of the sulcus m. supracoracoidei, which differs from Protomelanitta velox , where this sulcus is without a pronounced concavity and pits. As in all anatids, the margin of the facies articularis humeralis projects laterally, and the cotyla scapularis is large, rounded and deeply concave.

Scapula. The right scapula is visible in ventrolateral view ( Figures 1 View FIGURE 1 , 4 View FIGURE 4 ). This element has a typical duck-like appearance with an extended acromion and a moderately prominent tuberculum coracoideum. In the ventral edge, just below the articular part, there is a “shelf-shaped” attachment with a longitudinal depression. A similar structure is found in extant Clangula hyemalis . In Aythya , Melanitta and Bucephala there is a flattening but without a depression, while in Anas the flattening, if present, is very small.

Clavicula. Omal fragments of both claviculae have been preserved; the right one is visible in lateral view, and the left in medial view ( Figures 1 View FIGURE 1 , 4 View FIGURE 4 , 5 View FIGURE 5 ). Unlike Mionetta blanchardi and all extant Anatidae , the clavicula is very robust and thick also lateromedially. The thick facies articularis acrocoracoidea is well developed and moderately long, somewhat similar to that in Melanitta ; in many extant Anatidae it is longer and rather narrow (e.g. Anatini, Aythyini) or poorly developed (e.g., Dendrocygninae , Tadornini, Somateria ).

Humerus. The left humerus is visible in caudal view and the right humerus in dorsocranial view ( Figures 1 View FIGURE 1 , 5 View FIGURE 5 ). Although the proximal part of the shaft is partially crushed, a weak capital shaft ridge oriented to the tuberculum dorsale is visible, as in Protomelanitta . This ridge orientation is also seen in fossil Mionetta , Manuherikia , and Dunstanetta and in extant Oxyura and Mergini, except that the ridge is prominent in these taxa (Worthy and Lee, 2008: character 51). In other taxa including fossil Nogusunna and Miotadorna and extant Dendrocygninae and Tadornini, the prominent capital shaft ridge is oriented between tubercule dorsale and caput humeri. Miocene Aythya shihuibas and extant Anatini have virtually no capital shaft ridge. Of all Miocene taxa, the caput humeri is most similar to that of Protomelanitta . It is true that it is wider proximodistally than in Protomelanitta gracilis and P. bakeri but still relatively narrow, distinctly narrower than, for example, in Caerulonettion natator . The distal margin of the caput humeri in caudal view is almost straight as in Protomelanitta ; in Sharganetta and especially in Caerulonettion the distal margin is convex. Similar to, among others, Protomelanitta gracilis , P. bakeri and Nogosunna conflictoides , the fossa pneumotricipitalis dorsalis is narrower than the fossa pneumotricipitalis ventralis (Worthy and Lee, 2008: character 53) and undercuts the caput humeri; in Sharganetta and extant Dendrocygninae , Tadornini, Aythyini and Anatini, the fossa does not undercut the head (Worthy and Lee, 2009: character 134). Although the apex of the tuberculum ventrale is missing, it seems that, like in Manuherikia lacustrina, Lavanttalornis hassleri and extant Oxyurinae, Mergini, Aythyini and Anatini, it was directed caudo-cranially (Worthy and Lee, 2008: character 57) because the caudal border of fossa pneumotricipitalis ventralis is not concave as in Protomelanitta gracilis but straight or even slightly convex. In Protomelanitta gracilis , Mionetta blanchardi , Miotadorna sanctibathansi , Chenoanas , Sharganetta and extant Dendrocygninae and Tadornini, the tuberculum ventrale is directed proximally. As in most extant ducks including Oxyurinae, Mergini, Aythyini and Anatini, the proximal profile of the humerus is interrupted by a distinct notch created by incisura capitis (Worthy and Lee, 2008: character 59). A similarly distinct notch is also found in many fossil taxa such as Sharganetta mongolica , Nogusunna conflictoides , Protomelanitta gracilis , P. bakeri , Aythya molesta , A. shihuibas , Manuherikia and Dunstanetta . A shallow notch was reported for Mionetta blanchardi , Mionetta defossa , Carulonettion natator , Miotadorna sanctibathansi , Aythya denesi and Lavanttalornis hassleri whereas in Selenonetta and Pinpanetta as well as extant Dendrocygninae and Tadornini it is almost missing. The tuberculum dorsale is similar to that of Protomelanitta in that it is subtriangular, has only a slightly extended distal margin, and is somewhat elevated above the caudal surface of shaft - the latter not as much as the modern Dendrocygninae but more than the Miocene Aythya shihuibas , modern Aythyini, Mergini, or Anatini which are defined as “coplanar” (Worthy and Lee, 2008: character 56). Unlike in Protomelanitta bakeri but similar to P.garacilis , the tuberculum dorsale is oriented more caudally than dorsally. Proximal fragments of the crista deltopectoralis are visible on both humeri, and the right humerus also shows remnants of the connection between the crista deltopectoralis and the humeral shaft, which allows for the assessment of the length of the crista. Unlike Selenonetta, the crista deltopectoralis is noticeably longer than the proximal width of the humerus. Other details of the proximal humerus, including fossa pneumotricipitalis ventralis and crista bicipitalis, are not visible. The processus flexorius extends distally roughly as far as the condylus dorsalis (Worthy and Lee, 2008: character 63). As in many extant Mergini, the fossa brachialis is large, wide and has a distinct ventral margin; in extant Anatini, the fossa is usually narrower and has a smaller surface area.

Ulna. The left ulna is visible in ventral view, and the distal part of the right bone is visible in dorsal view ( Figures 1 View FIGURE 1 , 5 View FIGURE 5 ). The ulna is noticeably shorter than the humerus. The proximal part is too poorly preserved for meaningful comparisons. As in some Mergini (e.g., Melanitta ), the ventral edge of the condylus dorsalis is somewhat elongated and merges quite gently with the shaft; in Anatini, the edge is semicircular and joins more abruptly with the shaft.

Carpometacarpus. The left carpometacarpus is visible in ventral view, the right one is missing ( Figures 1 View FIGURE 1 , 5 View FIGURE 5 ). Processus extensorius is less prominent cranially than in extant Tadornini; as in the similarly sized extant Aythya nyroca , it is relatively wide proximodistally and its proximal edge is oriented mainly cranially, whereas in many extant Anatini it is directed proximocranially. Contrary to e.g., Mioquerquedula palaeotagaica and Protomelanitta velox , the fossa infratrochlearis is deep, and another fossa located distocaudally to the processus pisiformis is also very pronouned. The caudal rim of the dorsal portion of the trochlea carpalis has a wide notch, which can be seen on the CT scan. The synostosis metacarpalis distalis is shorter than the width of the carpometacarpus measured at the distal end of the spatium intermetacarpale (Worthy and Lee, 2008: character 84). Short synostosis is present in some extant Mergini ( Bucephala , Clangula , Melanitta ) and Tadornini ( Tadorna ). A long (i.e., different) synostosis is present in Miocene Lavanttalornis hassleri, Mionetta blanchardi , Manuherikia lacustrina and in many extant taxa, including Dendrocygninae , Aythyini and Anatini.

Os carpi ulnare. The left os carpi ulnare was originally visible in proximal view but has been carved from the slab and is now a three-dimensional object ( Figures 1 View FIGURE 1 , 6 View FIGURE 6 ). Its distal surface is different from all extant ducks (this element has not yet been described in Miocene ducks): In dorsal view, the distal edge is almost flat, while in extant Anatidae there is a bulge of varying shape.

Pelvis. The damaged pelvis, which appears rather narrow, is visible in dorsal view against the background of the sternum ( Figures 1 View FIGURE 1 , 3A). The right femur is in articulation with it. There is a cluster of several dozen smooth gastroliths in the postacetabular region; some of them are whitish and others are black. The cluster measures approximately 18 x 10 mm. The dimensions of the exposed stones range approximately from 0.5 to 2.5 mm.

Femur. The crushed but almost complete right femur, in articulation with the pelvis, is visible in caudolateral view ( Figure 1 View FIGURE 1 ). In the proximal part, the outline of the trochanter has been preserved; it protrudes above the caput femoris. Contrary to all extant Anatidae , the shaft is very thick for its length; it does not seem that this thickness results exclusively from crushing because both edges (cranial and caudal) are smooth. Similarly stout bones, albeit of the wing, have been observed in Bambolinetta ; leg elements are not known for this fossil. The shaft is moderately bent caudally in the distal third (Worthy and Lee, 2008: character 93). Members of extant Anas have straight shafts, whereas Aythni and Mergini usually have shafts that are bent to varying degrees. The distal part does not allow a meaningful description.

Ratios between skeletal elements. The brachial index (humerus length/ulna length) for Gracanicanetta happi is 1.1 and is the same as for Lavanttalornis hassleri and many extant species from all Anatinae groups (Appendix 1). Slightly lower values (approximately 1.0) are observed in all Dendrocygninae and parts of Tadornini, and slightly higher values (1.2) are observed in representatives of various groups. The length ratio of carpometacarpus / phalanx proximalis digiti majoris is more diversified in Anatidae . This ratio for Gracanicanetta happi is 2.2. No extant species examined had such a low value of this ratio; the closest value (2.3) occurred in some Dendrocygna , Oxyura and Mergini. Higher values (2.4 - 2.7) were observed in various taxonomic groups. Lavanttalornis hassleri also showed a higher ratio (2.4). The ratio humerus length / carpometacarpus length for Gracanicanetta happi is 1.7. This value was higher (1.8 - 2.0) in all examined representatives of Dendrocygninae (5 species), Oxyurinae (1 species) and Aythyini (5 species) (Appendix 1). The vast majority of Anatini (15 out of 20) showed slightly lower values of this ratio (1.6), but the rest had the same ratio (1.7). A similar range of ratio was in Tadornini (1.6 - 1.7). For Mergini, the values of the ratio ranged from 1.6 to 1.8, with more than half of the species (6 out of 10) having the same value as for Gracanicanetta (1.7). The carpometacarpus length / coracoid medial length ratio for Gracanicanetta is 1.1 (Appendix 1). The ranges encompassing this ratio value were found in Mergini (09 - 1.2), Aythyini (0.9 - 1.1) and Anatini (1.1 - 1.2). All Dendrocygninae and Tadornini had larger ratio values (1.2 - 1.4 and 1.3 - 1.4, respectively), and Oxyurini had a distinctly smaller value (0.9).