Wait? What Part of the Pharynx Becomes the Jaw? – #UREES270 – 2018

Cerny, Lwigale, Ericsson, Meulemans, Epperlein, and Bronner-Fraser, 2004, Developmental origins and evolution of jaws: new interpretation of “maxillary” and “mandibular”: Developmental Biology, v. 276, p. 225-236

What’s it about?

Historically, it has been thought that the upper part of the first branchial (gill) arch becomes the upper jaw (maxillary) and the lower part of the first arch becomes the lower jaw (mandibular). By tracing neural crest cells in the embryos of axolotls and chickens, the authors show that both the upper and lower jaws develop from the lower part of the first arch, and that the upper part becomes the trabecular cartilage, which is part of the skull.

Why does it matter?

These results show that our assumptions about the embryological origins of the jaw are probably incorrect, which then affects our interpretation of the evolutionary origins of the jaw.

Why did I read this?

This paper is for discussion on Friday of week 5 of my vertebrate paleontology course. Week five is focused on the evolutionary origins of the jaw. This paper illustrates in interdisciplinary nature of paleontology and the value of embryology to evolutionary questions.