How to keep a head in order
Article Abstract:
The mammalian cephalic region is composed of a complex skeletal system that is divided into the braincase, the dermal bone and visceral arch. The development of the cephalic skeletal region was analyzed by antibody labelling in chicks with transplanted sections of quail rhombomeres. Antibody labeling indicated the development of the retroarticular process from the fourth rhombomere while the second and first rhombomeres form the rest of the jaw. On the other hand, the attachments of visceral arch muscles to the braincase wall are formed from neural-crest cell populations.
Publication Name: Nature
Subject: Zoology and wildlife conservation
ISSN: 0028-0836
Year: 1997
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Something fishy in the family tree
Article Abstract:
Zhu and colleagues have discovered a basal bony fish with unexpected characteristics that may result in large parts of the vertebrate family tree being reconsidered. The 400-million year old Psarolepis is from the earliest Devonian and latest Silurian of Yunnan in south China and has a brain-case similar to that of an orthodox sarcopterygian. However the tooth-bearing bones of the snout and lower jaw, and the cheek bones, match those of actinopterygians. It appears to have spines in front of its median fins, a feature of acanthodians.
Publication Name: Nature
Subject: Zoology and wildlife conservation
ISSN: 0028-0836
Year: 1999
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Therapsids and transformation series
Article Abstract:
The newly discovered Paleocene therapsid fossil Chronoperates has become the subject of much scientific debate over whether to classify it as a mammal or a branch group near to but not included in the mammals. Some scientists support its classification as a mammal-like reptile because it lacks some of the characteristics used to determine the clade Mammalia. However, others contend that those characteristics are the result of further specializations and that the Chronoperates signifies an early mammal.
Publication Name: Nature
Subject: Zoology and wildlife conservation
ISSN: 0028-0836
Year: 1993
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