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Hagfish embryos have characteristics of gnathostomes and may be plesiomorphic; [33] however, these characteristics drastically change morphologically as the hagfish matures. [33] The following hagfish and lamprey phylogeny is an adaptation based on the 2019 work of Miyashita et al. [ 69 ]
Lampreys have seven pairs of pouches, while hagfishes may have six to fourteen, depending on the species. In the hagfish, the pouches connect with the pharynx internally. In adult lampreys, a separate respiratory tube develops beneath the pharynx proper, separating food and water from respiration by closing a valve at its anterior end. [11]
Lampreys have seven pairs of pouches, while hagfishes may have six to fourteen, depending on the species. In the hagfish, the pouches connect with the pharynx internally. In adult lampreys, a separate respiratory tube develops beneath the pharynx proper, separating food and water from respiration by closing a valve at its anterior end. [6]
A related species, the Gulf hagfish (Eptatretus springeri), occurs in the Gulf of Mexico. [7]To distinguish these two types of hagfishes, we can look at their lateral line and eyes, the Myxine glutinosa has no lateral line system and also an unpigmented, cornea-like window in the skin overlying the eye.
In the hagfish, the pouches connect with the pharynx internally and a separate tube which has no respiratory tissue (the pharyngocutaneous duct) develops beneath the pharynx proper, expelling ingested debris by closing a valve at its anterior end. [9]
Hagfish and lampreys have relatively small cerebella, while the mormyrid cerebellum is massive and apparently involved in their electrical sense. [59] The brain stem or myelencephalon is the brain's posterior. [59] As well as controlling some muscles and body organs, in bony fish at least, the brain stem governs respiration and osmoregulation. [59]
The Basihyals and Basibranchials lie at the midline of the lower edge of the throat. Almost all modern chondrichthyans have a single midline basihyal, as do many teleosts, lungfish, and tetrapodomorphs. In tetrapods, the basihyal is modified into a structure known as the hyoid bone, which provides muscle attachment for the tongue, pharynx, and ...
The mouth cone ("everted pharynx") of a possible new species of Meiopriapulus, a marine worm in the Priapulida, bears pharyngeal teeth. [5] Fossils of the Yunnanozoon and Haikouella possess pharyngeal teeth. The lower pharyngeal bones of cichlids also carry specialized teeth which augment their normal mandibular teeth in the breakdown of food.