Hyperoartia or Petromyzontida is a disputed group of vertebrates that
includes the modern lampreys and their fossil relatives.
Examples of hyperoartians from early in their fossil record are
Endeiolepis and Euphanerops, fish-like animals with hypocercal tails
that lived during the Late
Devonian Period. Some paleontologists still
place these forms among the "ostracoderms" (jawless armored fishes) of
the class Anaspida, but this is increasingly considered an artificial
arrangement based on ancestral traits.
Placement of this group among the jawless vertebrates is a matter of
dispute. While today enough fossil diversity is known to make a close
relationship among the "ostracoderms" unlikely, this has muddied the
issue of the Hyperoartia's closest relatives. Traditionally the group
was placed in a superclass
Cyclostomata together with the Myxini
(hagfishes). More recently, it has been proposed that the
more basal among the skull-bearing chordates, while the Hyperoartia
are retained among vertebrates. But even though this may be correct,
the lampreys represent one of the oldest divergences of the vertebrate
lineage, and whether they are better united with some "ostracoderms"
in the Cephalaspidomorphi, or not closer to these than to e.g. to
other "ostracoderms" of the Pteraspidomorphi, or even the long-extinct
conodonts, is still to be resolved. Even the very existence of the
Hyperoartia is disputed, with some analyses favoring a treatment
of the "basal Hyperoartia" as a monophyletic lineage Jamoytiiformes
that may in fact be very close to the ancestral jawed vertebrates.
The only hyperoartians surviving today are lampreys, classified in the
Petromyzontiformes. The discovery of the fossil
back the oldest known occurrence of true lampreys to the Late
Devonian. The evidence of phylogeny, however, suggests the lamprey
lineage diverged much earlier from other vertebrates, rather than
arising from among the "ostracoderms". The origin of
therefore extend back to the early Paleozoic, if not earlier.
Placed in this group are at present:
†Jamoytiidae White 1946
Jamoytius kerwoodi White 1946
†Endeiolepidiformes Berg 1940
†Endeiolepididae Stensio 1939
Endeiolepis aneri Stensio 1939
†Euphaneropidae Woodward 1900
†Euphanerops longaevus Woodward 1900 [Legendrelepis Arsenault &
Janvier 1991; Legendrelepis parenti Arsenault & Janvier 1991]
Cornovichthys blaauweni Newman & Trewin 2001
^ Janvier, Philippe. "Palaeontology: Modern look for ancient lamprey".
Nature. 443 (7114): 921–924. doi:10.1038/443921a.
^ Osório, Joana; Rétaux, Sylvie (2008-02-15). "The lamprey in
evolutionary studies". Development Genes and Evolution. 218 (5):
221–235. doi:10.1007/s00427-008-0208-1. ISSN 0949-944X.
^ Haaramo, Mikko (2003). "Petromyzontidae - lampreys". in Mikko's
Phylogeny Archive. Retrieved November 25, 2013.
Extant chordate classes
Ascidiacea (sea squirts)
Thaliacea (pyrosomes, salps, doliolids)
(Vertebrates + Myxini)
(fish + Tetrapods)
Agnatha (jawless fish)
Chondrichthyes (cartilaginous fish: sharks, rays, chimaeras)
Actinopterygii (ray-finned fish)
Squamata (scaled reptiles)²
¹subclasses of Sarcopterygii
²orders of class Reptilia (reptiles)
³traditionally placed in Anapsida
italic are paraphyletic groups
This fish-related article is a stub. You can help by