Megamouth shark "M. applegatei" – have also recently been proposed on the basis of fossilized tooth remains. However, the Cretaceous-aged "M. comanchensis" has been recently reclassified as an odontaspid shark in the genus "Pseudomegachasma", and is in fact unrelated to the megamouth shark despite similar teeth morphology. The appearance of the megamouth is distinctive, but little else is known about it. It has a brownish-black colour on top, is white underneath, and has an asymmetrical tail with a long upper lobe, similar to that of the thresher shark. The interior of its gill slits are lined with finger-like gill rakers that capture
Fish anatomy gonads). Much like the mammalian immune system, teleost erythrocytes, neutrophils and granulocytes are believed to reside in the spleen whereas lymphocytes are the major cell type found in the thymus. In 2006, a lymphatic system similar to that in mammals was described in one species of teleost fish, the zebrafish. Although not confirmed as yet, this system presumably will be where naive (unstimulated) T cells accumulate while waiting to encounter an antigen. Fish anatomy Fish anatomy is the study of the form or morphology of fishes. It can be contrasted with fish physiology, which is the study of how the