| Palintropus | |
|---|---|
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | Theropoda |
| Clade: | Avialae |
| Clade: | †Ambiortiformes |
| Genus: | †Palintropus Brodkorb, 1970 |
| Species: | †P. retusus |
| Binomial name | |
| †Palintropus retusus (Marsh, 1892) | |
| Synonyms | |
Cimolopteryx retusaMarsh, 1892 | |
Palintropus is a prehistoricbirdgenus from the LateCretaceous. A singlespecies has been named (Palintropus retusus) based on a proximal coracoid from theLance Formation ofWyoming, dated to the latestMaastrichtian, 66 million years ago.[verification needed] Coracoids and a proximal scapula of two unnamed species from the upperCampanianDinosaur Park Formation ofAlberta, dating to between 76.5 and 75 million years ago,[1] are also known.[2]
Initially it was placed in thewastebin genus"Cimolopteryx".Pierce Brodkorb assigned it its current name, first affiliating it withApatornis in 1963, and establishing its current genus in 1970.[3]
Its relationships are not well determined, mainly due to the paucity of material. Several major theories have been established: Like many of the birds of the subtropical coastlands of theWestern Interior Seaway - maybe a bit like eastern Australia today - it is sometimes believed to be an early member of theCharadriiformes (waders, gulls, auks, etc.; see also "Graculavidae").[3] However, an alternate theory is that it is agalliform, perhaps aquercymegapodiid.[2]
In 2009, Longrich and colleagues proposed thatPalintropus is a primitive bird related toApsaravis. They conducted the firstcladistic analysis of the remains, and found this to be the most likely hypothesis, suggestingPalintropus warrants inclusion in the newly establishedPalintropiformes.[4]
The quercymegapodiid hypothesis is supported by paleornithologist Sylvia Hope's (2002) paper on Mesozoic neornithines.[5] This is based on the humeral facet of the coracoid having a large, free lateral flange, the reduced size of the procoracoid process, and a long, raised, ragged scar within the supracoracoid sulcus and parallel to the scapular facet. However, she also noted it differs from quercymegapodiids and more derivedgalliforms in retaining a supracoracoid foramen. Altogether, the most satisfying and quite robust hypothesis is that ifP. retusus was not actually an early quercymegapodiid, it was justbasal to that group.
The quercymegapodiids, anextinct group of prehistoric Galliformes, lived apparently on both sides of theAtlantic, which by then was narrower, with only a few straits separating Europe and North America in the temperateGreenland region. They seem to have been inhabitants of warm regions as they seem also have to occurred inBrazil, and it is quite likely that they were also found in or even originated inAfrica from where almost no contemporary bird fossils are known. Their undisputed fossil record starts in theEocene.
Given thatAnseriformes are now known to haveradiated into the families still present today, it is suspected that by the end of the Cretaceous, at least 4 lineages ofGalliformes existed as distinct:Megapodiidae,Cracidae,Phasianidae and the Quercymegapodiidae. Consequently, the possibility that the present species was also a quercymegapodiid is well in agreement with thephylogenetic andbiogeographic data.
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