The polypterids (bichirs and ropefish) are extant basal actinopterygian (ray-finned) fishes that breathe air and share similarities with extant lobe-finned sarcopterygians (lungfishes and tetrapods) ...

What might be mistaken for a waterslide in this image is actually the breathing tube, or trachea, of a dragonfly. This tube connects to openings in the insect's exoskeleton (outer “shell”) called ...

Invertebrates are a wildly diverse lot — far more diverse than the relatively small group known as vertebrates. Accordingly, the inverts have a huge diversity of life styles and body plans. Consider ...