acanthostega and icthyostega have been called fish-like tetrapods. Explain why they are described as such and describe the environment in which they probably lived.

blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart. as the ventricle contracts, blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs where it is oxygenated.