TY  - JOUR
A1  - Witmer, Lawrence M.
T1  - The craniofacial air sac system of Mesozoic birds (Aves)
T2  - Zoological journal of the Linnean Society
N2  - Birds are characterized by pneumatization of their skeletons by epithelial diverticula from larger, air-filled cavities. The diverticula-or 'air sacs'-that invade the postcranium result from outgrowths of the lungs; poslcranial pneumaticity has been very well studied. Much more poorly understood are the air sacs that pneumatize the skull. Study or craniofacial pneumaticity in modern birds (Neornithes) indicates the presence of two separate systems: nasal pneumaticity and tympanic pneumaticity, The lacrimal and maxillary bones arc pneumatized by diverticula of the main paranasal cavity, the antorbital sinus. There are five tympanic diverticula in neornithines that pneumatize the quadrate, articulare and the bones of the braincase. The pneumatic features of the following six genera of Mesozoic birds are examined: Archaeopteryx, Ellaliornis, Baplomis, Parahesperornis, Hesperornis and lchthyornis. Despite the 'archaic' aspect of most of these birds, many of the pneumatic features of neornithines are found in .Mesozoic birds and are considered primitive for Aves. The phylogenetic levels at which most of the avian pneumatic features arose within Archosauria are uncertain. Until the phylogenetic levels at which homologous pneumatic features arose are determined, it is unwise to use most pneumatic characters in the discussion of avian origins. Within avian phylogeny, Ornithurae and Neornithes are well-supported by pneumatic synapomorphies. There is a trend towards reduction of craniofacial pneumaticity within Hesperornithiformes. Witthin Neornithes, four derived pneumatic characters suggest that the Palaeognathae (ratites and tinamous) is monophyletic.
KW  - Pneumaticity
KW  - air sacs
KW  - craniofacial morphology
KW  - Mesozoic
KW  - Archaeopteryx
KW  - Hesperornis
KW  - lchtlryornis
KW  - phylogeny
Y1  - 2010
UR  - http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/14564
UR  - https://nbn-resolving.org/urn:nbn:de:hebis:30-1153286
SN  - 0024-4082
N1  - Signatur: 8 Q 17.273
VL  - 100
SP  - 327
EP  - 378
PB  - Blackwell
CY  - Oxford
ER  -