Myllokunmingiidae is a group of very early, jawless
prehistoric fish
The evolution of fish began about 530 million years ago during the Cambrian explosion. It was during this time that the early chordates developed the skull and the vertebral column, leading to the first craniates and vertebrates. The first fis ...
(
Agnatha
Agnatha (, Ancient Greek 'without jaws') is an infraphylum of jawless fish in the phylum Chordata, subphylum Vertebrata, consisting of both present (cyclostomes) and extinct (conodonts and ostracoderms) species. Among recent animals, cyclosto ...
ns) which lived during the
Cambrian period
Period may refer to:
Common uses
* Era, a length or span of time
* Full stop (or period), a punctuation mark
Arts, entertainment, and media
* Period (music), a concept in musical composition
* Periodic sentence (or rhetorical period), a concept ...
.
The Myllokunmingiids are the earliest known group of
craniate
A craniate is a member of the Craniata (sometimes called the Craniota), a proposed clade of chordate animals with a skull of hard bone or cartilage. Living representatives are the Myxini (hagfishes), Hyperoartia (including lampreys), and the m ...
s. The group contains three genera, ''
Haikouichthys
''Haikouichthys'' is an extinct genus of craniate (animals with notochords and distinct heads) that lived 518 million years ago, during the Cambrian explosion of multicellular life. ''Haikouichthys'' had a defined skull and other characteristi ...
'', ''
Myllokunmingia
''Myllokunmingia'' is a genus of basal chordate from the Lower Cambrian Maotianshan shales of China 518 to 490 mya and is thought to be a vertebrate, although this is not conclusively proven. The species M. fengjiaoa is 28 mm long and 6&n ...
'', and ''
Zhongjianichthys''. Their fossils have been found only in the
Maotianshan Shales
The Maotianshan Shales are a series of Early Cambrian deposits in the Chiungchussu Formation, famous for their '' Konservat Lagerstätten'', deposits known for the exceptional preservation of fossilized organisms or traces. The Maotianshan Shales ...
lagerstätte
A Lagerstätte (, from ''Lager'' 'storage, lair' '' Stätte'' 'place'; plural ''Lagerstätten'') is a sedimentary deposit that exhibits extraordinary fossils with exceptional preservation—sometimes including preserved soft tissues. These f ...
.
Taxonomy
* Order †Myllokunmingiida
Shu, 2003
** Family †Myllokunmingiidae
Shu, 2003
*** Genus †''
Haikouichthys
''Haikouichthys'' is an extinct genus of craniate (animals with notochords and distinct heads) that lived 518 million years ago, during the Cambrian explosion of multicellular life. ''Haikouichthys'' had a defined skull and other characteristi ...
''
Luo, Hu & Shu 1999 sensu Shu ''et al.'', 2003
**** Species †''
Haikouichthys ercaicunensis''
Luo, Hu & Shu 1999 sensu Shu ''et al.'', 2003
*** Genus †''
Myllokunmingia
''Myllokunmingia'' is a genus of basal chordate from the Lower Cambrian Maotianshan shales of China 518 to 490 mya and is thought to be a vertebrate, although this is not conclusively proven. The species M. fengjiaoa is 28 mm long and 6&n ...
''
Shu, Zhang & Han, 1999
**** Species †''
Myllokunmingia fengjiaoa
''Myllokunmingia'' is a genus of basal chordate from the Lower Cambrian Maotianshan shales of China 518 to 490 mya and is thought to be a vertebrate, although this is not conclusively proven. The species M. fengjiaoa is 28 mm long and 6&n ...
''
Shu, Zhang & Han, 1999
*** Genus †''
Zhongjianichthys''
Shu, 2003
**** Species †''
Zhongjianichthys rostratus''
Shu, 2003
See also
Other stem vertebrates or transitional between
olfactores
Olfactores is a clade within the Chordata that comprises the Tunicata ( Urochordata) and the Vertebrata (sometimes referred to as Craniata). Olfactores represent the overwhelming majority of the phylum Chordata, as the Cephalochordata are the o ...
and
vertebrates
Vertebrates () comprise all animal taxa within the subphylum Vertebrata () (chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, with c ...
are:
*''
Metaspriggina
''Metaspriggina'' is a genus of chordate initially known from two specimens in the Middle Cambrian Burgess Shale and 44 specimens found in 2012 at the Marble Canyon bed in Kootenay National Park.
Whilst named after the Ediacaran organism ...
''
*''
Yunnanozoon
''Yunnanozoon lividum'' (Yunnan + Greek ζῷον ''zôion'', ''lividum''; "livid animal of Yunnan") is an extinct species of possible vertebrate or chordate from the Lower Cambrian, Chengjiang biota of Yunnan province, China. It is thought o ...
''
*''
Palaeospondylus
''Palaeospondylus'' is a fish-like fossil vertebrate. Its fossils are described from the Achanarras slate quarry in Caithness, Scotland.
The fossil as preserved is carbonized, and indicates an eel-shaped animal up to in length. The skull, whi ...
''
*''
Zhongxiniscus
''Zhongxiniscus'' is a genus of primitive chordate from eastern Yunnan that lived during the Early Cambrian. Known from a single specimen, it had a small, broad and short, fish-like body that was roughly ten millimeters in length. It possessed S- ...
''
*''
Haikouella
''Haikouella'' is an agnathan chordate from the Lower Cambrian Maotianshan Shales of Chengjiang County in Yunnan Province, China. An analysis in 2015 placed ''Haikouella'' as a junior synonym of ''Yunnanozoon,'' another Maotianshan shale Cambrian ...
''
References
Prehistoric jawless fish families
Cambrian chordates
Cambrian first appearances
Cambrian extinctions
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