The cambroernids are an informally-named

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English ter ...

of unusual

Paleozoic The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon. The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words ''palaiós'' (, "old") and ...

animals with coiled bodies and filamentous tentacles. They include a number of early to middle Paleozoic ( Cambrian to Devonian) genera noted as 'bizarre" or "orphan" taxa, meaning that their affinities with other animals, living or extinct, has long been uncertain. One leading hypothesis is that cambroernids were unusual ambulacrarian

deuterostomes Deuterostomia (; in Greek) are animals typically characterized by their anus forming before their mouth during embryonic development. The group's sister clade is Protostomia, animals whose digestive tract development is more varied. Some exampl ...

, related to echinoderms and

hemichordates Hemichordata is a phylum which consists of triploblastic, enterocoelomate, and bilaterally symmetrical marine deuterostome animals, generally considered the sister group of the echinoderms. They appear in the Lower or Middle Cambrian and includ ...

. Previously some cambroernids were compared to members of the broad invertebrate clade

Lophotrochozoa Lophotrochozoa (, "crest/wheel animals") is a clade of protostome animals within the Spiralia. The taxon was established as a monophyletic group based on molecular evidence. The clade includes animals like annelids, molluscs, bryozoans, brachi ...

; in particularly they were allied with lophophorates, a subset of lophotrochozoans bearing

ciliated The cilium, plural cilia (), is a membrane-bound organelle found on most types of eukaryotic cell, and certain microorganisms known as ciliates. Cilia are absent in bacteria and archaea. The cilium has the shape of a slender threadlike project ...

tentacles known as lophophores. However, this interpretation has more recently been considered unlikely relative to the deuterostome hypothesis for cambroernid origins. Cambroernids encompass three particular types of enigmatic animals first appearing in the Cambrian: ''

Herpetogaster ''Herpetogaster'' is an extinct cambroernid genus of animal from the Early Cambrian Chengjiang biota of China, Pioche Formation of Nevada and Middle Cambrian Burgess Shale of Canada containing the species ''Herpetogaster collinsi'' and ''Herpeto ...

'' (the

type genus In biological taxonomy, the type genus is the genus which defines a biological family and the root of the family name. Zoological nomenclature According to the International Code of Zoological Nomenclature, "The name-bearing type of a nominal ...

), '' Phlogites'', and the eldoniids. They are united by a set of common features including at least one pair of bifurcated or divided oral tentacles, and a large stomach and narrower intestine enclosed together in a coiled sac. ''Herpetogaster'' has a segmented and clockwise-curved body attached to the substrate via a narrow and partially mobile stolon (stalk). ''Phlogites'' was even more simple, with a thick immobile stolon leading up to a tentacle-bearing calyx (cup-shaped main body). The eldoniids (also known as eldonioids or eldonids) were diverse and disc-shaped, commonly described as "medusiform", i.e.

jellyfish Jellyfish and sea jellies are the informal common names given to the medusa-phase of certain gelatinous members of the subphylum Medusozoa, a major part of the phylum Cnidaria. Jellyfish are mainly free-swimming marine animals with umbrell ...

-shaped. Though the lifestyle of eldoniids is still debated, it can be agreed that they had a large curved stomach and no stolon.

References

Prehistoric deuterostomes Burgess Shale fossils {{Cambrian-animal-stub