BIO202H5 Chapter Notes - Chapter 1: Actinomycetales, Australopithecus Afarensis, Escovopsis
Document Summary
Ratfish fossils can suggest whether the mother provided nourishment for the developing young (matrotrophy) as opposed to yolk-based feeding (lecithotrophy) It is also possible that fetuses ate eggs (oophagy) or mucoid-protein secretions of proteins and lipids from the lining of the uterus (histotrophy) Fossils also suggested that the female is able to carry multiple litters in the uterus at the same time (superfetation) The data from the fossil ratfish suggest that development of young within the body of the female and associated live birth appeared early in the evolutionary history of vertebrates. This raises the possibility that bearing live young, whether by vivipary or ovovivipary, could be an ancestral trait among vertebrates. This example illustrates the importance of the morphology of fossils in understanding the functions of the animals they represent. Tetrapods have 13 groups of hox genes tightly clustered at four loci, hoxa to hoxd.
