Characteristics. In the simplest sense, craniates are chordates with well-defined heads, thus excluding members of the chordate subphyla Tunicata (tunicates) and Cephalochordata (lancelets), but including Myxini, which have cartilaginous crania and tooth-like structures composed of keratin.Craniata also includes all lampreys and armoured jawless fishes, …

Eumetazoa (from Ancient Greek ... Characteristics of eumetazoans include true tissues organized into germ layers, the presence of neurons and muscles, and an embryo that goes through a gastrula stage. Some phylogenists once speculated the sponges and eumetazoans evolved separately from different single-celled organisms, ...

The Placozoa / p l æ k ə ˈ z oʊ ə / are a basal form of marine free-living (non-parasitic) multicellular organism. They are the simplest in structure of all animals. Three genera have been found: the classical Trichoplax adhaerens, Hoilungia hongkongensis, and Polyplacotoma mediterranea, where the last appears most basal.The last two have been found only since 2017.

Ecdysozoa (/ ˌ ɛ k d ɪ s oʊ ˈ z oʊ ə /) is a group of protostome animals, including Arthropoda (insects, chelicerata, crustaceans, and myriapods), Nematoda, and several smaller phyla.They were first defined by Aguinaldo et al. in 1997, based mainly on phylogenetic trees constructed using 18S ribosomal RNA genes. A large study in 2008 by Dunn et al. strongly supported the …

The universal tetrapod characteristics of front limbs that bend backward at the elbow and hind limbs that bend forward at the knee can plausibly be traced to early tetrapods living in shallow water. Panderichthys is a 90–130 cm (35–50 in) long fish from the Late Devonian period (380 Mya). It has a large tetrapod-like head.

Etymology. The word "animal" comes from the Latin animalis, meaning 'having breath', 'having soul' or 'living being'. The biological definition includes all members of the kingdom Animalia. In colloquial usage, the term animal is often used to refer only to nonhuman animals. The term "metazoa" is from Ancient Greek μετα (meta, used to mean "later") and ζῷᾰ (zōia, plural of …

Study with Quizlet and memorize flashcards containing terms like Which one of the following terms applies to the phylum Arthropoda? a. coelomate b. radial symmetry c. deuterostome d. Parazoa e. diploblastic, What are the three animal phyla that dominate animal life on land? a. Cnidaria, Mollusca, Platyhelminthes b. Platyhelminthes, Nematoda, Arthropoda c. Porifera, …

The subphylum Hexapoda (from Greek for 'six legs') comprises most species of arthropods and includes the insects as well as three much smaller groups of wingless arthropods: Collembola, Protura, and Diplura (all of these were once considered insects). The Collembola (or springtails) are very abundant in terrestrial environments. Hexapods are named for their most distinctive …

Los moluscos (Mollusca, del latín mollis "blando") conforman uno de los grandes filos del reino animal.Son invertebrados protóstomos celomados, triblásticos de simetría bilateral (aunque algunos pueden tener una asimetría secundaria) no segmentados, de cuerpo blando, desnudo o protegido por una concha.Los moluscos son los invertebrados más numerosos después de los …

Pauropods are small, pale, millipede-like arthropods.Around 830 species in twelve families are found worldwide, living in soil and leaf mold. They look rather like centipedes, or millipedes, and may be a sister group of the latter. However, this is controversial, as a close relationship with Symphyla has also been posited.