Question: Bubble-net feeding is a unique and complex feeding behavior engaged in by what animal, that has a distinctive body shape, with long pectoral fins and a knobbly head?

 It is one of the few surface feeding behaviors that humpback whales are known to engage in.  This type of feeding is often done in groups. Bubble-net feeding is a unique and complex feeding behavior engaged in by Humpback whales (Megaptera novaeangliae) and Bryde's whales in Gulf of Tosa (), Japan.  The group size can range from a minimum of two or three whales participating and up to sixty at one time.  Whales can also perform a similar method of surface feeding called lunge feeding but is done solo. <SEP> The humpback whale ("Megaptera novaeangliae") is a species of baleen whale.  One of the larger rorqual species, adults range in length from 12 - and weigh about 36000 kg .  It is known for breaching and other distinctive surface behaviors, making it popular with whale watchers.  Males produce a complex song lasting 10 to 20 minutes, which they repeat for hours at a time.  Its purpose is not clear, though it may have a role in mating.  The humpback has a distinctive body shape, with long pectoral fins and a knobbly head. <SEP> The Callorhinchidae (sometimes spelled "Callorhynchidae"), or plough-nose chimaeras, are a family of marine fish containing one genus, Callorhinchus.  They are similar in form and habits to other chimaeras, but are distinguished by the presence of an elongated, flexible, fleshy snout, with a vague resemblance to a ploughshare.  The snout is used to probe the sea bottom in search of the invertebrates and small fishes on which it preys.  The remainder of the body is flat and compressed, often described as elongated.  The mouth is just under this snout and the eyes are located high on top of the head.  The usual color is black or brown, and, often a mixture between the two.  Phylogenetically, they are the oldest group of living jawed Chondrichthyes.  They possess the same cartilaginous skeleton seen in sharks but are considered holocephali to distinguish them from the shark and ray categorization.  Because of this, they provide a useful research organism for studying the early development of the jawed characteristic.  Among the Chondrichthyes genome, "Callorhinchus" has the smallest genome.  Because of this, it has been proposed to be used for entire genome sequencing to represent the cartilaginous fish class.  They are considered to resemble a cross between a shark and a ray or skate, but can be distinguished from sharks because they possess an operculum over their gill slits.  Additionally, their skin is smooth, not covered in tough scales, characteristic of the shark.  While the shark's jaw is loosely attached to the skull, the Callorhinchidae family differ in that their jaws are fused to their skulls.  Many classify the Callorhinchidae as a chimeric species due to their shared characteristics of both the sharks and rays.  They are found in muddy and sandy substrates of the ocean bottom, where they filter feed, with small shellfish making up the bulk of their diet.  They have broad flat teeth that have adapted for this type of eating habit, two pair that reside in the upper jaw and one pair in the lower jaw.  In addition to its utilization for feeding, the trunk of the Callorhinchus fish can sense movement and electric fields, allowing them to locate their prey.  They possess large pectoral fins, believed to aid in moving swiftly through the water.  They also have two dorsal fins spaced widely apart, which help identify the species in the open ocean. <SEP> Asterolepis is an extinct genus of antiarch placoderms from the Devonian of North and South America and Europe.  They were heavily armored flat-headed benthic detritivores with distinctive jointed limb-like pectoral fins and hollow spine.  The armor plate gives the "Asterolepis" a box-like shape.  Its pectoral fins are also armored but the caudal and dorsal fin are not.  The first fossils were named by M. Eichwald in 1840 after noticing star-like markings on the fossils.