Friday, February 15, 2013

Pterosaurs taken as birds

Here are pterosaurs that have been taken as birds. This again shows that pterosaurs and primitive birds are very similar.
Palaeocursornis is a monotypic genus of pterosaurs. The only known species, P. corneti, was described in 1984 based on a single bone (MTCO-P 1637) interpreted as the distal part of a left femur, found in Early Cretaceous (Berriasian rocks (dating to around 143 mya) from a mine at Cornet near Oradea in northwestern Romania. It was initially assumed to be a flightless paleognathe bird, possibly a ratite, and later as a more primitive ornithuromorph or non-avialan theropod (Benton et al., 1997). However, re-evaluation of the specimen suggested that it was not a femur at all, but the upper arm bone (humerus) of a pterodactyloid pterosaur similar to Azhdarcho.[1]
Piksi is a genus of pterosaurs containing the single species Piksi barbarulna (meaning "strange elbowed big bird ", from Blackfoot piksi, "big bird" or, specifically, "chicken" and Latin barbarus "strange, outlandish" + ulnaelbow[1]). It lived roughly 75 million years ago in what is now MontanaUSA. Known from parts of a right wing – the humerusulna and radius bones – the only specimens found so far are housed in the Museum of the Rockies(collection number MOR 1113). The genus Piksi is monotypic at present.
The bones are fragmentary and represent roughly the elbow area. Comparing the fossils' size to the wing bones of other ground birds, P. barbarulna seems to have been about as large as a Common Pheasant, i.e. some 15 in (35–40 cm) long excluding tail, and with a wingspan of perhaps 30 in (80 cm) or somewhat less. It would thus have weighed maybe 1 – 2 pounds (some 500 g – 1 kg).[2]The original description of the fossils found its affinities unresolvable except that it was probably an ornithothoracine bird. Agnolin and Varricchio (2012) reinterpreted Piksi barbarulna as a pterosaur rather than a bird, most likely a member of Ornithocheiroidea.[3]
Original article::
Varricchio (2002 ) described some forelimb bones from the Late Cretaceous (Campanian) Two Medicine Formation, Glacier County, Montana (USA), as the holotype of Piksi barbarulna, a supposed ornithothoracine bird. However reevaluation of Piksi Varricchio, 2002 instead recognizes this genus as belonging to Pterosauria Kaup, 1834 and not Aves Linnaeus, 1758. Piksi exhibits the following derived humeral traits of pterosaurs: 1) very large ectepicondyle; 2) large trochlea; 3) with a deep, wide and poorly deliminated brachial depression that is proximodistally extended; 4) a wide and deep olecranal fossa not marked dorsally by a ridge; and 5) lacking a distal depression of the groove for the m. humerotricipitalis. Moreover, the putative Early Cretaceous birds Eurolimnornis Jurcsák & Kessler, 1986 and Palaeocursornis Jurcsák & Kessler, 1986 , based on distal humeri, are also regarded as pterosaurs. The record of Piksi constitutes an important addition to the Latest Cretaceous pterosaurian record.


  1. Here is a summary of some of the information about basal pterosaurs:
    "The hairs were described as stranded or plumaceous and seen as corresponding to Stage II in the evolution of feathers and as indicative that pterosaur hair [protofeathers] and dinosaur [paravian] feathers were homologous.[2]"

    Another characteristic shared by pterosaurs and birds:;jsessionid=A1CA60013B42AE8DCA4EDCACEF3A2BF7
    The morphology of the trunk of pterosaurs differs from previous descriptions in several aspects that are crucial to lung ventilation and respiratory efficiency. Contrary to earlier reports [1], [7], [29], [30], pterosaur sternal ribs are not of uniform length and posterior elements commonly exhibit a two-fold or greater increase in length (Figs. 2, S1; Table S2). Consequently, and unlike recent reconstructions of pterosaurs which tend to show a horizontal or even posterodorsally sloping sternum, the posterior margin of the pterosaur sternum sloped posteroventrally, similar to birds[21]. (Leon P. A. M. Claessens1*, Patrick M. O'Connor2, David M. Unwin3)


    Another characteristic shared by pterosaurs and birds:;jsessionid=A1CA60013B42AE8DCA4EDCACEF3A2BF7
    "The aspiration pump of pterosaurs maximised trunk expansion in the ventrocaudal region, while at the same time limiting the degrees of freedom of movement of the trunk in other directions. This provided greater control over the location, amount and timing of trunk expansion, thereby enabling precisely-timed localized generation of pressure gradients within the pulmonary system, a trait that is also present in living birds where it is of paramount importance for the generation of air flow patterns in the lungs [27], [36]." (Leon P. A. M. Claessens1*, Patrick M. O'Connor2, David M. Unwin3)