| Garganornis | |
|---|---|
 | |
| Drawings ofGarganornis material discovered from Gargano and Scontrone localities | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Anseriformes |
| Family: | Anatidae |
| Genus: | †Garganornis Meijer, 2014 |
| Species: | †G. ballmanni |
| Binomial name | |
| †Garganornis ballmanni Meijer, 2014 | |
Garganornis (meaning "Gargano bird") is an extinct genus of enormous flightlessanatidwaterfowl from the LateMiocene ofGargano,Italy. The genus contains one species,G. ballmanni, named by Meijer in 2014. Itsenormous size is thought to have been an adaptation to living in exposed, open areas with no terrestrial predators, and as a deterrent to the indigenous aerial predators like theeagleGarganoaetus and the giantbarn owlTyto gigantea.
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Thetibiotarsus ofGarganornis is approximately 30% larger than that of the livingmute swan incircumference. Based on comparisons with the latter, it has been estimated thatGarganornis had a weight in the range of 15–22 kilograms (33–49 lb), larger than any livinganatid. This suggests that it was likely flightless.[1]
The preservedcarpometacarpi from the wings had quite a short and robust shaft, much shorter than any of the living large-bodiedanseriforms that are capable of flight. The carpometacarpus was also peculiarly flattened on its top end; and the trochlea carpalis (a bony articular process that drives wing extension and flexion) is reduced and weak in shape, limiting wrist movement - both likely adaptations to a flightless life.[2]
In some specimens ofGarganornis, there is a small bony knob on the top of the carpometacarpus that is similar to that ofswans,geese,ducks, and other anseriforms; this was likely used for fighting, as in other members of the group.[2][3]
Likewise short and robust was thetarsometatarsus of the foot. The processes known as the trochlea metatarsi II and IV, on the bottom portion of the tarsometatarsus, are more equal in length than most other anseriforms, with the exception of theCape Barren goose,screamers, and the giant, extinctCygnus falconeri. Thephalanx bones of the toes are also relatively robust, and similar to other giant anseriforms; however, the impressions of ligaments on the bones are weaker and less defined.[2]
The first remains ofGarganornis were discovered from the Posticchia 5 fissure filling near the town ofApricena inGargano,Italy. These deposits are part of theMioceneMikrotia faunal assemblage (named after an abundantmurid rodent), which has been dated to 6–5.5 Ma in age. Theholotype consists of a single partial lefttibiotarsus, catalogued as RGM 443307, which was described by Meijer in 2014.[1]
Additional material was later described from Gargano by Paviaet al. in 2016, consisting of partialcarpometacarpi (DSTF-GA 49, NMA 504/1801), a single damaged tibiotarsus (DSTF-GA 77), partialtarsometatarsi (RGM 425554, RGM 425943), and variousphalanx bones from the foot (MGPT-PU 135356, RGM 261535, RGM 261945). Additionally, some geologically earlier butmorphologically comparable material was described from the Scontrone locality, which is close to the town ofScontrone and has been dated to 9 Ma in age. This material consists of an almost complete tarsometatarsus, SCT 23; although it is temporally separated from the other material, the morphology and unusually large size of the bone suggests that it pertains toGarganornis.[2]
The genus nameGarganornis is derived from the general area of Gargano, in which the holotype fossils were discovered; the Greek suffixornis means "bird". The species name honors Peter Ballmann, who first described the birds of the Gargano region.[1]
Several characteristics of thetibiotarsus allowGarganornis to be placed definitely in theorderAnseriformes: themedial condyle is angled medially and bears a projection at its front end; and thecanal of the extensor tendon is placed centrally over theintercondylar fossa.[1] Features of thecarpometacarpus allow for a more specific assignment to the familyAnatidae: the extensor process is parallel to the trochlea carpalis and is not tilted towards the bottom; thepisiform process is wide and unpointed; and a small knob is present above the caudal carpalfovea.[2]
Garganornis peculiarly shares a number of characteristics in the tibiotarsus with another group of large anseriforms, theGastornithidae.[4] In particular, the intercondylar fossa is wide, the bottom opening of the extensor canal is circular (although it is placed more centrally relative to thecondyles than in gastornithids), the extensorsulcus is relatively deep, and the pons supratendineus (a projection above the opening of the extensor canal) has a depression on its side.[1] However, given that gastornithids and otherPaleogene fauna do not appear to have survived in - or even reached - this region, it is more likely that these shared traits areconvergent adaptations to gigantic body sizes.[2]
Surveys conducted by P. Ballmann in the 1970s revealed a diverse bird fauna in the Gargano locality, consisting of 16 different taxa;[5] later work established the presence of 10 additional distinct taxa (not includingGarganornis), bringing the total to 26.[6] These include theanatidsAnas cf. velox and an additional unnamed anatid;[7] the gianteaglesGarganoaetus freudenthali andG. murivorus,[5] as well as an unnamed smalleraccipitrid;[6] thephasianidPalaeortyx volans;[8] theowlsTyto robusta,T. gigantea,"Strix" perpasta,[5] another species referred toStrix, an additional species referred toAthene, and an unnamed taxon formerly referred toT. sanctialbani;[6] thepigeonColumba omnisanctorum; theswiftApus wetmorei;[5] thesandpipersCalidris sp. and an unnamed taxon;[7] athreskiornithid; awoodpecker; asongbird; tworails; twocharadriiforms; abustard; amousebird; and acorvid.[6] To date,Garganornis is the only bird that is found in both the Gargano and Scontrone localities; the lack of other Gargano birds in Scontrone is probably a result oftaphonomic bias.[2]
Asides from birds, various mammals and reptiles are known from the Gargano and Scontrone localities. Most notably, thegiantmuridMikrotia (includingM. magna,M. parva, andM. maiuscula) is very abundant; the genus lends its name to the entire local ecosystem, which has become known as theMikrotia fauna.[9][10] A second murid,Apodemus sp., is also present. Other rodents include the giantdormiceStertomys laticrestatus,S. daunius, andS. lyrifer, along with the smaller speciesS. deguili,S. simplex, andS. daamsi;[11][10][12] and thehamstersHattomys gargantua,H. nazarii,[11][10][12]Neocricetodon sp., andApocricetus sp.[11] Thegymnures (hairy hedgehogs)Deinogalerix freudenthalli,D. minor,D. intermedius,D. brevirostris,D. koenigswaldi, andD. masinii were also giant,[11][12] while their smaller relativeApulogalerix cf. pusillus is also present.[10] Other mammals include thecrocidosoricineshrewLartetium cf. dehmi;[10] thepikasProlagus apricenicus andP. imperialis;[11] the deer-likehoplitomerycidHoplitomeryx mathei; and the otterParalutra garganensis.[12] There is one reptile genus: a crocodile referred toCrocodylus.[13]
Garganornis and the rest of theMikrotia fauna has been dated to theTortonian stage of the LateMiocene.[12] During the Miocene, the Gargano and Scontrone areas were part of an isolated archipelago that has been referred to as the Apulia-Abruzzi Palaeobioprovince.[14] Small mammals, including the gymnure ancestors ofDeinogalerix, probably reached these islands viarafting.[12]
