Which of the following creatures is NOT included in the phylum Arthropoda?

The correct answer is mammals, as they belong to a different phylum known as Chordata. The phylum Arthropoda includes a vast diversity of invertebrate animals that are characterized by their jointed legs, segmented bodies, and exoskeletons made of chitin. This phylum encompasses various species, including spiders, crabs, and centipedes.

Spiders are arachnids, a subgroup within Arthropoda, which also includes scorpions and ticks. Crabs are crustaceans, another group within the phylum, and are well-known for their hard shell and aquatic lifestyle. Centipedes are myriapods, characterized by their elongated bodies and a high number of legs. All these examples (spiders, crabs, and centipedes) showcase the defining features of organisms classified under the phylum Arthropoda, thereby distinguishing them from mammals, which are vertebrates and feature distinct characteristics, such as fur or hair and mammary glands.