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Cranial morphology of Archaeopteryx : evidence from the seventh skeleton

1996; Taylor & Francis; Volume: 16; Issue: 1 Linguagem: Inglês

10.1080/02724634.1996.10011286

1937-2809

Andrzej Elżanowski, Peter Wellnhofer,

Ichthyology and Marine Biology

ABSTRACT ABSTRACT Most of the cranial bones are preserved in the seventh skeleton of Archaeopteryx. Whereas most of the braincase bones and the quadrates are crushed against one another as a result of sediment compaction, the displaced bones lying apart are nearly intact. In contrast with the predominantly reptilian postcranial skeleton, the skull of Archaeopteryx shows a few specifically avian traits. The palatine has a maxillary (=premaxillary) process, a hookshaped choanal process, and a long pterygoid wing, which makes it distinctively avian and different from the tetraradiate palatine of archosaurs. The mandible lacks the coronoid bone. Being unrelated to locomotion, the avian features of the skull demonstrate that Archaeopteryx is a bird rather than a feathered nonavian archosaur. The interdental plates, ectopterygoid, a big rostroventral wing of the prootic that contacted the laterosphenoid rostra1 to the trigeminal foramen, and the postorbital and quadratojugal processes of the squamosal add to the evidence that Archaeopteryx is the most primitive of the unquestionable birds known to date. Archaeopteryx is more like certain theropods than any other nonavian archosaur in having a strongly curved, hook-shaped jugal process of the ectopterygoid and probably a single vomer.