needlefishes. In other words, as traditionally defined, the halfbeak family is paraphyletic. Within the subfamily Hemiramphinae, the "flying halfbeak" genus Oxyporhamphus has proved to be particularly problematic; while morphologically closer to the flyingfishes, molecular evidence places it with Hemiramphus and Euleptorhamphus. Together, these three genera form the sister group to the flyingfish family. The other two hemiramphine genera Hyporhamphus and Arrhamphus form another clade of less clear placement. Rather than being closely related to the flyingfishes, the subfamily Zenarchopterinae appears to be the sister group of the needlefishes and sauries. This is based on the pharyngeal jaw apparatus, sperm ultrastructure, and molecular evidence. However, this hypothesis has awkward implications for how the morphological evolution of the group is understood, because the fused pharyngeal plate has been considered reliably diagnostic of the halfbeak family. Furthermore, the existing theory that because juvenile needlefish pass through a developmental stage where the lower jaw is longer than the upper jaw (the so-called "halfbeak stage") the theory that halfbeaks are paedomorphic needlefish is untenable. In fact the unequal lengths of the upper and lower jaws of halfbeaks appears to be the basal condition, with needlefish being relatively derived in comparison. Morphology The halfbeaks are elongate, streamlined fish adapted to living in open water. Halfbeaks can grow to over SL in the case of Euleptorhampus viridis. The scales are relatively large, cycloid (smooth), and easily detached. There are no spines in the fins. A distinguishing characteristic is that the third pair of upper pharyngeal bones are anklylosed (fused) into a plate. Halfbeaks are one of several fish families that lack a stomach, all of which possess a pharyngeal jaw apparatus (pharyngeal mill). Most species have an extended lower jaw, at least as juveniles, though this feature may be lost as the fish mature, as with Chriodorus, for example. As is typical for surface dwelling, open water fish, most species are silvery, darker above and lighter below, an example of countershading. The tip of the lower jaw is bright red or orange in most species. Halfbeaks carry several adaptations to feeding at the water surface. The eyes and nostrils are at the top of the head and the upper jaw is mobile, but not the lower jaw. Combined with their streamlined shape and the concentration of fins towards the back (similar to that of a pike), these adaptations allow halfbeaks to locate, catch, and swallow food items