The catfishes, a large and highly diverse order of the Ostariophysi. Another ordinal name commonly used is Nematogathi, from the Greek nematos, thread, and gnathos, jaw, a descriptive name referring to the long barbels around the mouth of most catfishes. Catfishes differ from other members of the Ostariophysi in having a more complex Weberian apparatus and in lacking intermuscular bones, as well as lacking subopercle, symplectic, or intercalar bones in the head. They are further characterized by either lacking scales (in which case they are covered with tough skin) or being covered with overlapping bony plates; having vomer, pterygoid, and palatine bones that are usually toothed; having maxillae that are rudimentary and toothless; lacking a parietal bone; usually having one to four pairs of barbels (some members of the family Loricariidae lack visible barbels); having (usually) an adipose fin and having pectoral and dorsal fins that are each preceded by a strong spine in most species.